US20170271863A1 - System and method for connecting a first battery in parallel with a second battery by charging for equalization - Google Patents
System and method for connecting a first battery in parallel with a second battery by charging for equalization Download PDFInfo
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- US20170271863A1 US20170271863A1 US15/608,890 US201715608890A US2017271863A1 US 20170271863 A1 US20170271863 A1 US 20170271863A1 US 201715608890 A US201715608890 A US 201715608890A US 2017271863 A1 US2017271863 A1 US 2017271863A1
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- battery
- voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/001—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection limiting speed of change of electric quantities, e.g. soft switching on or off
- H02H9/002—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection limiting speed of change of electric quantities, e.g. soft switching on or off limiting inrush current on switching on of inductive loads subjected to remanence, e.g. transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
- H02J7/0018—Circuits for equalisation of charge between batteries using separate charge circuits
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
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- Y02T10/7055—
Definitions
- Batteries are used as an important source of electrical energy in portable applications and can also function as important stationary electrical energy storage devices. Batteries can provide a source of electrical energy for many purposes. For example, batteries provide electrical energy for handheld devices, electric cars, various types of electronic vehicles, alternative energy storage, etc. Batteries can also be used for storage of electrical energy when sources of electronic energy are not otherwise available.
- cells In order to provide a sufficient supply of electrical energy, cells, as well as batteries, may be connected in parallel and/or in series. Various series/parallel connections can provide a desired current and voltage, for a wide number of applications.
- An embodiment of the present invention may therefore comprise a method of safely connecting a first battery in parallel with a second battery using chargers comprising: detecting a first terminal voltage of terminals of the first battery; detecting a second terminal voltage of terminals of the second battery; charging the first battery to a first voltage if the first terminal voltage of the first battery is less than the second terminal voltage of the second battery; charging the second battery to a second voltage if the second terminal voltage of the second battery is less than the first terminal voltage of the first battery; connecting the terminals of the first battery and the terminals of the second battery in parallel if the first voltage is sufficiently close to the second terminal voltage, or if the second voltage is sufficiently close to the first terminal voltage, so that currents flowing between the first battery and the second battery upon initially connecting the terminals of the first battery to the terminals of the second battery are less than a first maximum current
- An embodiment of the present invention may further comprise a method of safely connecting a first battery in parallel with a second battery using discharging techniques comprising: detecting a first terminal voltage of terminals of the first battery; detecting a second terminal voltage of terminals of the second battery; actively discharging the second battery to a second voltage if the terminal voltage of the second battery is greater than the terminal voltage of the first battery; actively discharging the first battery to a first voltage if the terminal voltage of the first battery is greater than the terminal voltage of the second battery; connecting terminals of the first battery and the terminals of the second battery in parallel if the second voltage is sufficiently close to the first terminal voltage, or the first voltage is sufficiently close to the second terminal voltage, so that currents created upon initially connecting the first battery and the second battery are less than a first desired maximum current.
- An embodiment of the present invention may further comprise a method of safely connecting a first battery in parallel with a second battery using DC to DC converters comprising: detecting a first terminal voltage of terminals at the first battery; detecting a second terminal voltage of terminals of the second battery; connecting an input of a step-down DC to DC converter to terminals of the first battery and an output of the step-down DC to DC converter to terminals of the second battery if the first terminal voltage is greater than the second terminal voltage; connecting the input of the step-down DC to DC converter to the terminals of the second battery and an output of the step-down DC to DC converter to terminals of the first battery if the second terminal voltage is greater than the first terminal voltage.
- An embodiment of the present invention may further comprise a method of safely connecting a first battery in parallel with a second battery using DC to DC converters comprising: detecting a first terminal voltage of terminals at the first battery; detecting a second terminal voltage of terminals of the second battery; detecting a first state of charge of the first battery; detecting a second state of charge of the second battery; connecting an input of a step-up DC to DC converter to the first battery and an output of the step-up DC to DC converter to the second battery if the state of charge of the first battery is greater than the state of charge of the second battery and if the first terminal voltage is less than the second terminal voltage; connecting an input of the step-up DC to DC converter to the second battery and an output of the step-up DC to DC converter to the first battery if the state of charge of the second battery is greater than the state of charge of the first battery and if the first terminal voltage is greater than the second terminal voltage.
- An embodiment of the present invention may further comprise a method of safely connecting a first battery in parallel with a second battery using a bi-directional DC to DC converter comprising: connecting terminals of the first battery to a first input of the bi-directional DC to DC converter; connecting terminals of a second battery to a second input of the bi-directional DC to DC converter; using the bi-directional DC to DC converter to transfer charge between the first battery and the second battery in the direction that reduces the resulting current at the moment of initial connection of the first terminals to the second terminals; connecting the terminals of the first battery to the terminals of the second battery when the first battery has a first terminal voltage and open circuit voltage that is sufficiently close to a second terminal voltage and open circuit voltage on the second battery so that currents flowing between the first battery and the second battery, when the first battery is initially connected in parallel to the second battery, are less than a maximum current.
- An embodiment of the present invention may further comprise a method of safely connecting a battery in parallel with a capacitive load using a DC to DC converter comprising: connecting terminals of the battery to a first input of the DC to DC converter; connecting terminals of the capacitive load to a second input of the DC to DC converter; using the DC to DC converter to transfer charges between the battery and the capacitive load; connecting the terminals of the battery to the terminals of the load when the battery has a first charge that is sufficiently close to a second charge on the capacitive load so that currents flowing between the battery and the capacitive load when the battery is initially connected to the capacitive load are less than a maximum current.
- An embodiment of the present invention may further comprise a system for safely connecting a first battery in parallel with a second battery using charging techniques comprising: a controller that detects a first terminal voltage of terminals of the first battery, and a second terminal voltage of terminals of the second battery; a first charger connected to the first battery, which charges the first battery to a first voltage, the first charger activated by the controller if the first terminal voltage is less than the second terminal voltage; a second charger connected to the second battery, which charges the second battery to a second voltage, the second charger activated by the controller if the second terminal voltage is less than the first terminal voltage; a switch that connects the first battery in parallel with the second battery that is activated by the controller if the first voltage is sufficiently close to the second terminal voltage, or if the second voltage is sufficiently close to the first terminal voltage, so that currents flowing between the first battery and the second battery when the switch is initially activated by the controller are less than a first maximum current.
- An embodiment of the present invention may further comprise a system for safely connecting a first battery in parallel with a second battery using automated discharging techniques comprising: a controller that detects a first terminal voltage of terminals of the first battery and a second terminal voltage of terminals of a second battery; a first switch that is activated by the controller that connects a first resistive element in parallel with the first battery to actively discharge the first battery to a first voltage if the first terminal voltage is greater than the second terminal voltage; a second switch that is activated by the controller that connects a second resistive element in parallel with the second battery to actively discharge the second battery to a second voltage if the second terminal voltage is greater than the first terminal voltage; a third switch activated by the controller, that connects the first battery in parallel with the second battery if the first voltage, if present, is sufficiently close to the second terminal voltage, or the second voltage, if present, is sufficiently close to the first terminal voltage, so that currents flowing between the first battery and the second battery, when the third switch is initially activated by the controller
- An embodiment of the present invention may further comprise a system for safely connecting a first battery in parallel with a second battery using DC to DC converters comprising: a controller that detects a first terminal voltage of terminals of a first battery, and a second terminal voltage of terminals of a second battery; a step-down DC to DC converter having an input and an output; at least one switch that connects the input to the terminals of the first battery, and the output to the terminals of the second battery when the first terminal voltage is greater than the second terminal voltage, and the input to the terminals of the second battery and the output to the terminals of the first battery when the second terminal voltage is greater than the first terminal voltage.
- An embodiment of the present invention may further comprise a system for safely connecting a first battery in parallel with a second battery comprising: a bi-directional DC to DC converter having a first input and a second input; a controller that generates control signals; a plurality of first electronic switches, responsive to the control signals, that connect terminals of the first battery to a first input of the bi-directional DC to DC converter, and terminals of the second battery to a second input of the bi-directional DC to DC converter, to transfer charge between the first battery and the second battery; at least one second electronic switch that connects the terminals of the first battery in parallel to the terminals of the second battery when the first battery has a first charge that is sufficiently close to a second charge on the second battery so that current flowing between the first battery and the second battery, when the second electronic switch is activated, is less than a maximum current.
- An embodiment of the present invention may further comprise a system for safely connecting a battery in parallel with a capacitive load comprising: a DC to DC converter having a first input and a second input; a controller that generates control signals; a plurality of first electronic switches, responsive to the control signals, that connect terminals of the battery to a first input of the DC to DC converter, and terminals of the capacitive load to a second input of the bi-directional DC to DC converter, to transfer charge between the battery and the capacitive load; at least one second electronic switch that connects the terminals of the battery in parallel to the terminals of the capacitive load when the battery has a first charge that is sufficiently close to a second charge on the capacitive load so that current flowing between the battery and the capacitive load, when the second electronic switch is activate, is less than a maximum current.
- An embodiment of the present invention may further comprise an isolated, bi-directional DC to DC converter comprising: a first DC voltage source; an inductor; a first pair of switches that connected the inductor to the first DC voltage source in a first polarity direction during a first phase of operation; a second DC voltage source; a second pair of switches that connect the inductor to a second DC voltage source in a second polarity direction, that is opposite to the first polarity direction, during a second phase of operation, so that current flows in the inductor in the first polarity direction while the inductor is connected to the first voltage source, during the first phase of operation, and the current through the inductor is reduced during the second phase of operation.
- an isolated, bi-directional DC to DC converter comprising: a first DC voltage source; an inductor; a first pair of switches that connected the inductor to the first DC voltage source in a first polarity direction during a first phase of operation; a second DC voltage source; a second pair of switches that connect the induct
- An embodiment of the present invention may further comprise an isolated, uni-directional DC to DC converter comprising: a DC voltage source; an inductor; a pair of switches that connect the inductor to the DC voltage source during a first phase of operation so that current flows through the inductor in a first direction; a load; a pair of diodes that allow the current to continue to flow through the inductor during a second phase of operation when the first pair of switches are opened and the DC voltage source is isolated from the inductor.
- an isolated, uni-directional DC to DC converter comprising: a DC voltage source; an inductor; a pair of switches that connect the inductor to the DC voltage source during a first phase of operation so that current flows through the inductor in a first direction; a load; a pair of diodes that allow the current to continue to flow through the inductor during a second phase of operation when the first pair of switches are opened and the DC voltage source is isolated from the inductor.
- An embodiment of the present invention may further comprise an isolated, uni-directional DC to DC converter comprising: a DC voltage source; an inductor; a first pair of switches that connect the inductor to the DC voltage source during a first phase of operation so that current flows through the inductor in a first direction; a load; a second pair of switches that connect the inductor to the load that allows the current to continue to flow through the inductor in the first direction during a second phase of operation when the first pair of switches are opened and the second pair of switches are substantially simultaneously closed and the DC voltage source is isolated from the inductor.
- an isolated, uni-directional DC to DC converter comprising: a DC voltage source; an inductor; a first pair of switches that connect the inductor to the DC voltage source during a first phase of operation so that current flows through the inductor in a first direction; a load; a second pair of switches that connect the inductor to the load that allows the current to continue to flow through the inductor in the first direction during a second phase
- An embodiment of the present invention may further comprise a method of converting a first DC voltage to a second DC voltage using an isolated, bi-directional DC to DC converter comprising: generating the first DC voltage using a first DC voltage source; applying the first DC voltage to an inductor using a first pair of switches that connect the first DC voltage source to the inductor in a first polarity direction; generating the second DC voltage using a second DC voltage source; applying the second DC voltage to the inductor using a second pair of switches that connect the second DC voltage source to the inductor in a second polarity direction that is opposite to the first polarity direction.
- An embodiment of the present invention may further comprise a method of converting a first DC voltage to a second DC voltage using an isolated, uni-directional DC to DC converter comprising: generating the first DC voltage using a DC voltage source; applying the DC voltage source to an inductor using at least a first pair of switches that connect the DC voltage source to the inductor that generates a current in the conductor; opening the at least first pair of switches and substantially simultaneously closing the at least second pair of switches so that the current continues to flow through the inductor into a load.
- An embodiment of the present invention may further comprise a method of converting a first DC voltage to a second DC voltage using an isolated, uni-directional DC to DC converter comprising: generating the first DC voltage using a DC voltage source; applying the DC voltage source to an inductor using at least a first pair of switches that connect the DC voltage source to the inductor that generates a current in the inductor; opening the at least first pair of switches so that current flows through the inductor and through a pair of diodes and a load connected to the diodes.
- FIG. 1 is a schematic view of an embodiment of two batteries that are wired for parallel connection through a switch.
- FIG. 2 is a schematic illustration of an embodiment of two batteries that are connected in parallel with a switch.
- FIG. 3 is a schematic illustration of an embodiment of two ideal voltage sources that are wired in parallel for connection with a switch.
- FIG. 4 is a schematic illustration of an embodiment of the two ideal voltage sources of FIG. 3 that are connected in parallel with a switch.
- FIG. 5 is a graph of an embodiment of a current pulse produced when connecting two ideal batteries.
- FIG. 6 is a graph of the voltages that are produced when connecting two ideal batteries in parallel.
- FIG. 7 is a schematic illustration of an embodiment of two real world batteries wired for connection parallel.
- FIG. 8 is a schematic block diagram of an embodiment of the two real world batteries of FIG. 7 that are connected in parallel with a switch.
- FIG. 9 is a plot of the current flowing between two real world batteries versus time.
- FIG. 10 is a plot of the internal, open circuit voltages of each battery.
- FIG. 11 is a schematic illustration of an embodiment of two batteries connected in parallel with highly differing voltages
- FIG. 12 is an equation illustrating the amount of current that initially flows between the two batteries with highly differing voltages are initially connected in parallel.
- FIG. 13 is a schematic illustration of an embodiment of two batteries connected in parallel with medium differing voltages.
- FIG. 14 is an equation illustrating the amount of current that initially flows between the two batteries with medium differing voltages are initially connected in parallel.
- FIG. 15 is a schematic block diagram of an embodiment of two batteries connected in parallel with low differing voltages.
- FIG. 16 is an equation illustrating the amount of current flowing when the two batteries with low differing voltages are initially connected in parallel.
- FIG. 17 is a schematic illustration of an embodiment of a pre-charge circuit in a first state.
- FIG. 18 is a schematic illustration of an embodiment of the pre-charge circuit of FIG. 17 in a second state.
- FIG. 19 is a schematic diagram of an embodiment of the circuit of FIG. 17 in a third state.
- FIG. 20 is a plot of the current versus time of current flowing in the circuit illustrated in FIG. 18 .
- FIG. 21 is a plot of the voltage of the capacitive load versus time in the circuit of FIG. 18 .
- FIG. 22 is a schematic illustration of an embodiment of a post-discharge circuit in a first state.
- FIG. 23 is a schematic illustration of an embodiment of the discharge circuit illustrated in FIG. 22 in a second state.
- FIG. 24 is a plot of current flowing versus time in the discharge circuit illustrated in FIG. 23 .
- FIG. 25 is a plot of voltage of the capacitive load versus time in the circuit illustrated in FIG. 23 .
- FIG. 26 is a schematic illustration of an embodiment of a battery equalization circuit in a first state.
- FIG. 27 is an illustration of current flowing in the embodiment of FIG. 26 versus time.
- FIG. 28 is a schematic illustration of an embodiment of the battery equalization circuit of FIG. 26 in a second state.
- FIG. 29 is a graph of the current flowing in the circuit of FIG. 28 versus time.
- FIGS. 30-33 are schematic illustrations of an embodiment of a battery equalization circuit in various states, wherein FIG. 30 illustrates a first battery at a lower voltage than a second battery, FIG. 31 illustrates a charger charging first battery, FIG. 32 illustrates a first battery charged to same voltage as a second battery, charger goes off, and FIG. 33 illustrates a first battery connected to a second battery.
- FIGS. 34-37 are schematic illustrations of an embodiment of a battery equalization circuit in various states, wherein FIG. 34 illustrates a first battery at a higher voltage than a second battery, FIG. 35 illustrates a charger charging a second battery, FIG. 36 illustrates a second battery charged to the same voltage as a first battery, charger goes off, and FIG. 37 illustrates a first battery connected to second battery.
- FIGS. 38-41 are schematic illustrations of an embodiment of a discharging equalization circuit in various states where FIG. 38 illustrates a voltage of first battery that is higher than a voltage of a second battery, FIG. 39 illustrates a discharge load connected across first battery, to remove charge from the battery, FIG. 40 illustrates a first battery discharged to the same voltage as a second battery, load disconnected, and FIG. 41 illustrates a first battery connected to a second battery.
- FIGS. 42-45 are schematic illustrations of an embodiment of a discharging equalization circuit in various states.
- FIG. 46A is a schematic block diagram of an embodiment of an energy exchange equalization circuit between two batteries.
- FIG. 46B is a schematic block diagram of another embodiment of an energy exchange equalization circuit between a battery and a capacitive load.
- FIG. 47 is a schematic illustration of an embodiment of an energy exchange equalization circuit in the case that the state of charge of a first battery is greater that the second battery, using a step-down DC-DC converter.
- FIG. 48 is a schematic illustration of an embodiment of an energy exchange equalization circuit in the case that the state of charge of a first battery is greater that the second battery, using a step-up DC-DC converter.
- FIG. 49 is a schematic illustration of an embodiment an energy exchange equalization circuit in the case that the state of charge of a first battery is lower that the second battery, using of a step-up DC-DC converter.
- FIG. 50 is a schematic illustration of an embodiment of an energy exchange equalization circuit in the case that the state of charge of a first battery is lower that the second battery, using a step-down DC-DC converter.
- FIG. 51 is a schematic illustration of an embodiment of an energy exchange battery equalization circuit using a step-up DC-DC converter, a step-down DC-DC converter, and a multitude of switches.
- FIG. 52 is a schematic diagram of an embodiment of a bi-directional, same polarity DC to DC converter.
- FIG. 53 is a schematic diagram of an embodiment of an inverting DC to DC converter in a first state.
- FIG. 54 is a schematic diagram of an embodiment with the inverting DC to DC converter of FIG. 53 disabled, and the batteries connected directly in parallel.
- FIG. 55 is a schematic diagram of an embodiment of a three-terminal, non-isolated, step-up DC to DC converter system.
- FIG. 56 is a schematic diagram of a three-terminal, non-isolated step-down DC to DC converter system.
- FIG. 57 is a schematic diagram of a three-terminal, non-isolated, inverting DC to DC converter system.
- FIG. 58 is a schematic diagram of an isolated, four-terminal DC to DC converter system.
- FIG. 59 is a schematic diagram of an embodiment of a four terminal, flying inductor, DC to DC converter system that is a transformer-less, DC-DC converter with limited isolation.
- FIG. 60 is a schematic illustration of a flying inductor DC to DC converter system that has the negative input terminals connected together.
- FIG. 61 is a schematic illustration of a flying inductor DC to DC converter system that has the positive input terminals connected together.
- FIG. 62 is a schematic illustration of a flying inductor DC to DC converter system that has the negative input terminal connected to the positive output terminal
- FIG. 63 is a schematic illustration of a flying inductor DC to DC converter system that has the positive input terminal connected to the negative output terminal
- FIG. 64 illustrates a unidirectional DC to DC converter.
- FIG. 65 is a schematic illustration of a bi-directional DC to DC converter system.
- FIG. 66 illustrates the differential voltages in a bi-directional flying inductor DC to DC converter system.
- FIG. 67A is a schematic diagram of an embodiment of a flying inductor DC to DC converter system.
- FIG. 67B is a schematic diagram of another embodiment of a flying inductor DC to DC converter system.
- FIG. 68 is a schematic diagram of the flying inductor DC to DC converter in phase-A.
- FIG. 69 is a schematic diagram of the flying inductor DC to DC converter in phase-B.
- FIG. 70 is a schematic diagram of the flying inductor DC to DC converter in a dead time phase.
- FIG. 71 is a schematic diagram of a uni-directional flying inductor DC to DC converter.
- FIG. 72 is a plot of inductor current versus time of the uni-directional flying inductor DC to DC converter illustrated in FIG. 71 that is operating in a discontinuous mode.
- FIG. 73 is a plot of inductor voltage versus time for the uni-directional DC to DC converter of FIG. 71 .
- FIG. 74 is a schematic illustration of the phase-A operation of a uni-directional flying inductor DC to DC converter.
- FIG. 75A is a schematic illustration of the phase-B operation of a uni-directional flying inductor DC to DC converter.
- FIGS. 75B, 75C illustrate the current flow into an external circuit that results from the loss of isolation due to mismatch in the opening and closing times of switches 7404 , 7410 .
- FIG. 76 is a schematic illustration of the dead time operation of a uni-directional flying inductor DC to DC converter.
- FIG. 77 is a plot of inductor current versus time of a uni-directional flying inductor DC to DC converter that is operating in critical mode.
- FIG. 78 is a plot of inductor voltage versus time of a uni-directional flying inductor DC to DC converter operating in critical mode.
- FIG. 79 is a plot of inductor current versus time of a uni-directional flying inductor DC to DC converter in continuous mode.
- FIG. 80 is a plot of inductor voltage of a uni-directional flying inductor DC to DC converter versus time that is operating in a continuous mode.
- FIG. 81A is a schematic diagram of a uni-directional, flying inductor, DC to DC converter employing a biased inductor.
- FIG. 81B is a schematic illustration of a uni-directional flying inductor DC to DC converter indicating the path of current that limits the input-output isolation when the voltage of the load is more negative than the voltage of the power source.
- FIG. 82 is a schematic illustration of a uni-directional flying inductor DC to DC converter indicating the path of current that limits the input-output isolation when the voltage of the load is more positive than the voltage of the power source.
- FIG. 83 is a schematic illustration of a uni-directional flying inductor DC to DC converter using bi-directional active switches, indicating the path of current that limits the input-output isolation when the voltage of the load is more negative than the voltage of the power source.
- FIG. 84A is a schematic illustration of a uni-directional flying inductor DC to DC converter using bi-directional active switches, indicating the path of current that limits the input-output isolation when the voltage of the load is more positive than the voltage of the power source.
- FIG. 84B is a schematic illustration of a uni-directional flying inductor DC to DC converter using bi-directional active switches, indicating the path of current that limits the input-output isolation when the voltage of the load is more negative than the voltage of the power source.
- FIG. 85 is a schematic illustration of a bi-directional DC to DC converter for transferring charges between voltage sources.
- FIG. 86 is a schematic illustration of a bi-directional DC to DC converter for transferring a charge from a voltage source to a load.
- FIG. 87 is a schematic illustration of a bi-directional flying inductor DC-DC converter transferring power from V 1 to V 2 , in phase-A.
- FIG. 88 is a schematic illustration of a bi-directional flying inductor DC-DC converter transferring power from V 1 to V 2 , in phase-B.
- FIG. 89 is a plot of current through the inductor versus time for critical mode operation of the bi-directional DC to DC converter of FIGS. 87 and 88 as the power transfer direction is from V 1 to V 2 .
- FIG. 90 is a plot of the voltage across the inductor versus time for critical mode operation of the bi-directional DC to DC converter, regardless of the direction of power transfer.
- FIG. 91 is an illustration of a bi-directional flying inductor DC to DC converter illustrating the power transfer direction from V 2 to V 1 that is initiated, in a phase-B operation.
- FIG. 92 illustrates the phase-A operation of the flying inductor DC to DC converter of FIG. 91 showing the power transfer direction from V 2 to V 1 , in a phase-A.
- FIG. 93 is a plot of the current through the inductor versus time for critical mode operation of the bi-directional DC to DC converter, showing the direction of power transfer is from V 2 to V 1 , as illustrated in FIGS. 91 and 92 .
- FIG. 94 is a plot of inductor current versus time for critical mode operation of the bi-directional DC to DC converter, showing the direction of power transfer from V 2 to V 1 .
- FIG. 95 is a plot of inductor current versus time for discontinuous mode of operation of the bi-directional DC to DC converter, as the direction of power transfer is from V 1 to V 2 .
- FIG. 96 is a plot of the inductor voltage versus time for a discontinuous mode of operation of the bi-directional DC to DC converter, as the direction of power transfer is from V 1 to V 2 .
- FIG. 97 is a plot of the inductor current versus time for a discontinuous mode of operation of the bi-directional DC to DC converter, as the direction of power transfer is from V 2 to V 1 .
- FIG. 98 is a plot of inductor voltage versus time for a discontinuous mode of operation of the bi-directional DC to DC converter, as the direction of power transfer is from V 2 to V 1 .
- FIG. 99 is a plot of inductor current versus time for a continuous mode of operation as the direction of power transfer is from V 1 to V 2 .
- FIG. 100 is a plot of inductor voltage versus time for a continuous mode of operation as the direction of power transfer is from V 1 to V 2 .
- FIG. 101 is a plot of inductor current versus time for a continuous mode of operation as the direction of power transfer is from V 2 to V 1 .
- FIG. 102 is a plot of inductor voltage versus time for a continuous mode of operation was the direction of power transfer is from V 2 to V 1 .
- FIG. 103 is a schematic diagram of a bi-directional, flying bridge DC to DC converter using bi-directional switches.
- FIG. 104 is a schematic diagram of a flying inductor DC to DC converter system converted to a three terminal device by connecting the positive terminals together.
- FIG. 105 is a schematic diagram of a flying inductor DC to DC converter converted to a three terminal device by connecting the negative terminals together.
- FIG. 1 is a schematic view of an embodiment of two batteries that are wired for connection in parallel through a switch 108 .
- battery 100 can be schematically illustrated as a voltage source 104 having a voltage V 1 and a series resistance 110 .
- battery 102 is schematically illustrated as a voltage source 106 having a voltage V 2 and a series resistance 112 .
- the two batteries 100 , 102 can be connected in parallel using switch 108 .
- FIG. 2 is a schematic illustration of the batteries illustrated in FIG. 1 , which are connected in parallel.
- battery 100 includes a voltage source 104 and an internal series resistance 110 .
- Battery 102 includes a voltage source 106 and an internal series resistance 112 .
- the switch 108 When the switch 108 is connected, current 110 flows between the two batteries if the terminal voltages of the batteries are different.
- the terminal voltage of battery 100 is greater than the terminal voltage of battery 102 so the current 110 flows in the direction of the arrow from battery 100 to battery 102 .
- the difference in the terminal voltages as well as the magnitude of the internal resistances of the batteries control the magnitude of the current 110 that flows between the parallel connected batteries 100 , 102 .
- FIG. 3 is a schematic illustration of an embodiment of two ideal voltage sources 300 , 302 that are wired in parallel for connection with a switch 304 .
- the ideal voltage source 300 includes a voltage source 306 that produces a voltage V 1 without any series resistance.
- Ideal voltage source 302 includes a voltage source 308 that produces a voltage V 2 without any series resistance.
- Switch 304 is used to connect the ideal voltage source 300 in parallel with the ideal voltage source 302 .
- FIG. 4 is a schematic block diagram of the embodiment of FIG. 3 with the switch 304 closed.
- the ideal voltage source 300 is connected in parallel through switch 304 to the ideal voltage source 302 .
- Current 310 flows in the direction of the arrow when V 1 is greater than V 2 . Since voltage source 300 is an ideal voltage source and voltage source 302 is an ideal voltage source, instantaneous current 310 , upon closing switch 304 , is infinite.
- FIG. 5 is a graph of the current 310 versus time.
- FIG. 7 is a schematic illustration of an embodiment of two batteries that are wired for connection in parallel by switch 704 .
- voltage source 710 having a voltage V 1 is connected in series with series resistance 706 in battery 700 .
- Battery 702 includes a voltage source 712 having a voltage V 2 that is connected in series with series resistance 708 .
- FIG. 8 is a schematic illustration of the embodiment of FIG. 7 with switch 704 closed.
- battery 700 which includes the voltage source 710 having voltage V 1 and series resistance 706 , is connected in parallel using switch 704 with battery 702 , which has a voltage source 712 , having a voltage V 2 , that is connected to series resistance 706 .
- switch 704 When switch 704 is closed, current 714 flows from battery 700 to battery 702 assuming V 1 is greater than V 2 .
- FIG. 9 is a graph of current versus time for the current 714 flowing between battery 700 and battery 702 in FIG. 8 .
- the peak value of the current in the plot illustrated in FIG. 9 is proportional to the difference in the terminal voltages of batteries 700 and 708 , and inversely proportional to the magnitude of the series resistance 706 , 708 , which limit the current flowing between batteries 700 , 702 .
- the decay time constant of the current 714 illustrated in FIG. 9 is proportional to the sum of the capacities of batteries 700 and 702 , assuming they are the same, and inversely proportional to the sum of the series resistances 706 , 708 .
- FIG. 10 is a plot of the open circuit voltages of battery 710 and battery 712 versus time.
- the voltages V 1 and V 2 of batteries 710 , 712 , respectively, are illustrated in the graph of FIG. 10 .
- the voltages gradually equalize to create a third voltage (V 3 ) 716 , which is the average of V 1 and V 2 , assuming that battery 700 and 708 have the same capacity.
- V 3 third voltage
- the gradual averaging of the voltages occurs over time that is proportional to the sum of the capacities of batteries 700 and 702 , assuming they are the same, and inversely proportional to the sum of the series resistances 706 , 708 .
- the level of the current resulting from the initial interconnection of two batteries in parallel may be on the order of 0.1 C to 100 C (where C is the value of the capacitance of the battery), depending on the chemistry and the state of charge levels of the two batteries.
- a current of 1 C means that such current, if sustained, would discharge a full battery in 1 hour.
- a current of 0.1 C means that such current, if sustained, would discharge a full battery in 10 hours.
- a current of 100 C means that such current, if sustained, would discharge a full battery in 36 seconds, which is 1/100 th of an hour.
- Batteries can typically handle currents of up to 1 C, although a charging current of 1 C may be a problem for some cells. Charging currents of greater than 1 C are often too much current for charging a battery. Batteries that have a steep slope in their voltage versus state of charge curve, and a very low internal resistance and are close to being full, present an extreme case for charging currents, since when a cell is completely full, the internal charging resistance of the cell increases, thereby reducing the resulting current.
- High power cells have a resistance that is particularly low (on the order of 25 mOhm*Ah) and the slope of the voltage versus state of charge curve for these cells is somewhat steep, especially when the cells are nearly full (on the order of 250 mV/1% SOC).
- the initial current will be on the order of 100 C.
- the initial current of 100 C quickly drops to a lower value, but the initial current can be damaging, especially to the battery being charged.
- Lithium ion cells are normally rated to handle as much as 30 C of discharging current and therefore a mostly charged cell may be able to handle being connected in parallel with a lesser charged cell. However, lithium ion cells should only be charged at 0.5 C, or at most, 4 C. Therefore, cells will be damaged if charged at 100 C.
- Lithium ion cells may be particularly sensitive to abuse, and they react by exploding and bursting in flames. Accordingly, the most care must be exercised when connecting such batteries in parallel. Lithium ion batteries should be connected directly in parallel only when the voltages on these batteries are equal or nearly equal so that the resulting current is minimized and damage does not occur to the batteries or cells.
- FIG. 11 is a schematic illustration of an embodiment of two parallel connected batteries 1100 .
- battery 1102 includes a voltage source 1114 having a voltage (V 1 ) that is equal to 12 volts.
- the series resistance 1110 of battery 1102 is 0.5 mOhm.
- Battery 1104 has a voltage source 1116 having a voltage V 2 that is equal to 10 volts.
- the series resistance 1112 is the same as series resistance 1110 of battery 1102 , which is 0.5 mOhm.
- FIG. 12 is a calculation 1200 of the initial current 1106 created when batteries 1102 , 1104 are connected in parallel, as illustrated in FIG. 11 .
- the initial current is the difference in the voltages, i.e., 12 volts minus 10 volts (2.0 volts), which is divided by the total of the series resistances, which is 1 mOhm. This results in an initial current of 2,000 amps.
- FIG. 13 is a schematic illustration of an embodiment of two parallel connected batteries 1300 .
- Battery 1302 is connected in parallel with battery 1304 by switch 1308 .
- Voltage source 1314 of battery 1302 provides a voltage of 10.2 volts.
- the series resistance 1310 of battery 1302 is 0.5 mOhm.
- Battery 1304 includes a voltage source 1316 , which provides a voltage V 2 equal to 10 volts.
- Series resistance 1312 of battery 1304 is 0.5 mOhm.
- FIG. 14 is an equation illustrating a calculation 1400 of the initial current 1306 that flows between the two batteries 1302 , 1304 when switch 1308 is initially closed.
- the current (i) 1306 is equal to the difference in voltages, which is 10.2 volts minus 10 volts (0.2 volts) divided by the total resistance of the two batteries, which is 1 mOhm.
- the initial current is calculated as 200 amps.
- the change of voltage from a difference of 2 volts to a difference of 0.2 volts reduces the initial current by an order of magnitude from 2000 amps to 200 amps.
- FIG. 15 is a schematic illustration of an embodiment of two parallel connected batteries 1500 .
- battery 1502 includes a voltage source that has a voltage V 1 equal to 10.02 volts.
- the series resistance 1510 of the battery 1502 is 0.5 mOhm.
- Battery 1504 has a voltage source 1516 that has a voltage V 2 equal to 10 volts.
- the series resistance 1512 of battery 1504 is 0.5 mOhm.
- Switch 1508 connects battery 1502 in parallel with battery 1504 so that a current 1506 flows between the batteries.
- FIG. 16 is a calculation 1600 of the initial current 1506 that flows between battery 1502 and battery 1504 when initially connected.
- the current (i) 1506 is equal to the difference in voltages 10.02 minus 10 volts, which is 0.02 volts, divided by the total series resistance of batteries 1502 and 1504 , which is 1 mOhm. This produces an initial current of 20 amps.
- the difference in voltages is reduced by an order of magnitude, which reduces the initial current by an order of magnitude to 20 amps from 200 amps, as illustrated in FIG. 14 .
- FIGS. 11-16 illustrate the manner in which the initial current can be greatly reduced by connecting batteries that have output voltages that are very close.
- FIGS. 11-16 also provide a perspective that a difference between the batteries of only 0.02 volts can still result in an initial current of 20 amps.
- precharging of a load can be used to equalize the charge on the load and the battery, which can limit the initial in-rush of current when the capacitive load and the battery are initially connected.
- battery 1702 has a voltage V 1 .
- a precharge resistor 1710 is used, which may have a resistance of 100 ohms.
- Precharge switch 1708 is used to connect the battery 1702 to a capacitive load 1704 to charge the load 1704 to a charge level that is substantially equal to the charge level V 1 of battery 1702 .
- pre-charge switch 1708 is closed, and current flows from the battery 1702 to charge the load 1704 .
- the precharge switch remains closed until the battery 1702 and load 1704 are equalized.
- the main switch 1706 is closed and the pre-charge switch 1708 is opened. Current can then flow from the battery 1702 directly to the load 1704 , such as during operation of the load 1704 .
- the precharge resistor 1710 is eliminated from the circuit since the pre-charge switch 1708 is open.
- FIG. 20 illustrates a graph 1900 that illustrates the current by flowing from the battery 1702 through the load 1704 when the pre-charge switch 1708 is initially connected.
- the initial current has a spike, which gradually decays.
- the initial current is equal to V 1 over R, which may range from approximately 10 amps to 100 amps.
- precharging resistor 1710 a resistor used for precharging has the disadvantage of dissipating energy, which is undesirable in situations in which battery charge is a valuable commodity. An additional surge may occur when the main switch is connected to the load if the voltages are not sufficiently equalized.
- FIG. 22 illustrates a post discharge circuit 2200 .
- battery 2202 has a voltage V 1 .
- Battery 2202 is connected to switch 2208 so that current 2302 is supplied to load 2204 .
- Switch 2210 is open, which isolates the discharge resistor 2206 .
- FIG. 23 is an illustration of the discharge circuit 2200 during the post discharge mode. As illustrated in FIG. 23 , switch 2208 is open and switch 2210 is closed. Discharge resistor 2206 discharges the current 2400 on the load 2204 through dissipation in discharge resistor 2206 while switch 2210 is closed. Battery 2202 is disconnected from the circuit by switch 2208 .
- FIG. 26 is a schematic illustration of an embodiment a battery connection circuit 2600 .
- Battery module 2602 includes a battery 2208 and a controller 2612 .
- Controller 2612 controls the operation of switch 2610 and detects the terminal voltage of battery 2608 on nodes 2630 , 2628 and a second battery 2604 on nodes 2620 , 2628 .
- Battery 2604 is connected to battery module 2602 by terminals 2620 , 2622 .
- Controller 2612 may also be connected to the battery 2604 to detect any current flowing from the battery 2604 to load 2626 . Detection of current may occur over a communication link from a module mounted on the battery 2604 or from a separate circuit (not shown) connected to the battery 2604 .
- Controller 2612 generates a control signal 2614 , which activates the switch 2610 . Controller 2612 activates the switch 2610 when it is determined that the terminal voltages of battery 2608 and battery 2604 are sufficiently close that an initial rush of current between battery 2608 and battery 2604 will not damage either of the batteries, terminals 2620 , 2622 or switch 2610 . Controller 2612 may also detect current flowing from battery 2604 to a load 2626 , as indicated above.
- controller 2612 includes logic that may prevent the generation of control signal 2614 to close the switch 2610 if the current from the battery 2604 to a load 2626 is high.
- FIG. 29 is a graph showing the voltage at terminals 2620 , 2622 .
- switch 2610 is closed, which applies the voltage (V 1 ) of battery 2608 to the terminals 2620 , 2622 , which is the same as the terminal voltage of battery 2604 .
- controller 2612 ensured that the voltage of battery module 2602 was close to the voltage of battery 2604 before closing switch 2610 , the voltage across terminals 2620 and 2622 remains the same after switch 2610 is closed.
- FIGS. 30-33 disclose a charging battery equalization circuit 3000 in different states of operation.
- a battery module 3002 is wired for connection to battery 3012 having a voltage (V 2 ).
- Battery module 3002 includes a battery 3006 having a voltage (V 1 ).
- a charger 3004 is connected to battery 3006 and is controlled by a controller 3010 .
- Controller 3010 is connected to the terminals of battery 3012 to detect the terminal voltage of battery 3012 .
- controller 3010 is connected to the terminals of battery 3006 to detect the terminal voltage of battery 3006 .
- Controller 3010 also controls the operation of switch 3008 .
- the battery module 3002 is connected to battery 3012 .
- Controller 3010 detects that the terminal voltage (V 2 ) is greater than the battery voltage (V 1 ) of battery 3006 .
- Controller 3010 generates a control signal 3014 to activate charger 3004 to charge battery 3006 .
- Switch 3008 remains in the open position while battery 3006 is being charged.
- controller 3010 detects that the terminal voltage of battery 3006 is charged to same voltage level as the terminal voltage of battery 3012 . In other words, battery 3006 is charged until V 1 equals V 2 . Controller 3010 then turns off the charger 3004 . Switch 3008 remains in the open position.
- controller 3010 closes the switch 3008 after detecting that the voltage (V 1 ) in battery 3006 is substantially equal to the voltage (V 2 ) in battery 3012 .
- Charger 3004 remains in the off position.
- Current 3016 that flows initially between the battery module 3002 and battery 3012 is essentially zero.
- FIGS. 34-37 illustrate a battery equalization circuit 3400 in different states of operation.
- a charger 3414 is used to charge battery 3412 , which has a voltage (V 2 ) that is less than the voltage (V 1 ) on battery 3404 .
- battery module 3402 is wired for connection with battery module 3410 .
- Battery module 3402 includes a battery 3404 that has a terminal voltage (V 1 ).
- Controller 3408 generates a control signal 3416 to control switch 3406 .
- Controller 3408 also generates a control signal 3418 that controls the operation of charger 3414 to charge battery 3412 in battery module 3410 .
- controller 3408 detects the terminal voltage of battery 3412 at nodes 3420 , 3422 . Similarly, controller 3408 detects the terminal voltage of battery 3404 at nodes 3424 , 3422 . The value of the measurement of the voltage of battery 3412 can also be provided to controller 3408 over a communication link from a controller in battery module 3410 (not shown). Controller 3408 detects that the battery 3412 has a terminal voltage (V 2 ) that is less than the terminal voltage (V 1 ) of battery 3404 . Controller 3408 then generates control signal 3418 to turn on charger 3414 to charge battery 3412 .
- controller 3408 detects that battery 3412 has been charged to a voltage which is substantially equal to the voltage of battery 3404 , and generates a control signal 3418 to turn off the charger 3414 . In other words, controller 3408 detects that V 1 is substantially equal to V 2 . Switch 3406 of battery module 3402 remains in an open position so that no current is flowing between battery module 3402 and battery module 3410 .
- the controller generates the control signal 3416 to close switch 3406 , once the controller 3408 has detected that the voltage (V 1 ) of battery 3404 is substantially equal to the voltage (V 2 ) of battery 3412 .
- Control signal 3418 causes the charger 3414 to remain in an off condition.
- a low level current (i) 3420 then may flow between the battery module 3402 and battery module 3410 to further equalize the charges between batteries 3404 , 3412 .
- Current 3420 should remain at a sufficiently low level so the damage is not caused to batteries 3404 , 3412 since battery 3412 has been charged so that V 2 is substantially equal to V 1 .
- chargers can be placed in both battery modules, which would constitute a combination of the circuits illustrated in FIGS. 30-33 and FIGS. 34-37 .
- FIGS. 38-41 illustrate a discharging equalizer circuit 3800 .
- the battery modules may include a load resistor to dissipate energy and lower the voltage of the battery that is at a higher voltage in order to equalize the voltages between the batteries prior to connection.
- the discharging equalizer circuit 3800 includes a battery module 3802 that is wired for connection with a battery 3804 .
- Battery module 3802 includes a battery 3806 that has a terminal voltage (V 1 ).
- Discharging resistor 3842 is wired to be connected in parallel with battery 3806 upon activation of switch 3848 .
- Controller 3808 generates a control signal 3844 that activates switch 3848 to connect the discharging resistor 3842 in parallel with battery 3806 .
- Controller 3808 also generates a control signal 3840 to activate switch 3846 .
- Battery 3804 has a voltage (V 2 ) that is greater than V 1 in the example illustrated in FIGS. 38-39 .
- controller 3808 has determined that the battery 3806 has a voltage that is greater than the voltage of battery 3804 by detecting the terminal voltage of battery 3804 on nodes 3850 , 3852 and battery 3806 on nodes 3854 , 3852 . Battery voltages can also be reported through a communication link from a controller on battery 3804 (not shown).
- Switch 3848 is activated by a control signal 3844 from controller 3808 , which connects the discharging resistor 3842 in parallel with the battery 3806 .
- the discharge resistor causes the battery 3806 to discharge by dissipating energy in the discharging resistor 3842 .
- the controller 3808 detects the voltage on the battery 3806 on nodes 3854 , 3852 and voltage on battery 3804 on nodes 3850 , 3852 , or through a communications link. Once the voltage on battery 3806 is substantially equal to the charge of battery 3804 , the controller 3808 deactivates control signal 3844 to open switch 3848 , as illustrated in FIG. 40 .
- controller closes the switch 3846 to connect battery 3806 in parallel with battery 3804 after switch 3848 has been opened, and the voltages on batteries 3806 , 3804 are substantially equal so that an initial in-rush of current does not occur.
- FIGS. 42-45 illustrate a discharging circuit 4200 , which discharges battery module 4204 .
- battery 4206 has a voltage that is lower than battery 4216 of battery module 4204 .
- Battery module 4202 is wired for connection in parallel with the battery module 4204 .
- Controller 4208 generates a control signal 4214 that operates switch 4220 .
- Switch 4220 connects discharge resistor 4218 in parallel with battery 4216 to discharge battery 4216 .
- Controller 4208 also generates a control signal 4212 to activate switch 4210 , which connects battery module 4202 in parallel with battery module 4204 when the voltages on batteries 4206 , 4216 are substantially equal so that a large in-rush of current does not occur.
- FIG. 43 is another illustration of the discharging equalization circuit 4200 .
- battery module 4202 is connected to battery module 4204 .
- Controller 4208 detects the terminal voltages of battery 4216 on nodes 4224 , 4226 .
- controller 4208 detects the terminal voltages of battery 4206 on nodes 4228 , 4226 . Since the controller 4208 detects that the voltage on battery 4216 is greater than the voltage of battery 4206 , controller 4208 activates control line 4214 to close switch 4220 .
- Switch 4220 connects discharging resistor 4218 in parallel with battery 4216 to discharge battery 4216 .
- FIG. 44 is a schematic illustration of the discharging equalization circuit 4200 with switch 4220 in an open position. Controller 4208 generates a control signal 4214 that opens switch 4220 once the terminal voltage of battery 4216 is substantially equal to the terminal voltage of battery 4206 .
- controller 4208 then activates switch 4210 to connect battery module 4202 in parallel with battery module 4204 .
- Current 4222 is sufficiently low that damage is not caused to batteries 4206 , 4216 .
- FIGS. 38-41 illustrate the discharging of one of the batteries
- FIGS. 42-45 illustrate the discharging of the other battery
- these circuits can be combined to allow discharge of either set of batteries by a controller.
- FIG. 46A is a schematic block diagram of an energy exchange battery equalization circuit 4600 .
- the circuits illustrated in FIGS. 38-45 disclose energy dissipation circuits, which dissipate energy from one of the batteries to equalize the charge on the batteries so that the initial in-rush of current does not damage the batteries. However, dissipation of energy from the batteries is inefficient.
- the energy exchange battery equalization circuit 4600 does not require charging, which requires an external energy source, or dissipation of charge, which results in wasted energy.
- the energy exchange battery equalization circuit 4600 operates by exchanging charge between the batteries prior to connection of the batteries in parallel so that the terminal voltages of the batteries, when connected in parallel, are substantially equal so that a large amount of current is not created, which may cause damage to the batteries.
- controller 4608 detects the terminal voltage of battery 4606 at nodes 4220 , 4222 .
- controller 4608 detects the terminal voltage of battery 4604 at nodes 4624 , 4622 . All of this is performed while the main switch 4616 is open.
- the DC to DC converter 4610 is disposed in the battery module 4602 .
- the DC to DC converter 4610 is connected between battery 4606 , 4604 upon closing of the DC to DC switch 4612 in response to a control signal 4618 .
- the DC to DC converter 4610 may comprise a bi-directional DC to DC converter that is capable of transferring charge in either direction between batteries 4606 , 4604 .
- the DC to DC converter 4610 may comprise a pair of DC to DC converters including a step-up converter and a step-down converter that can be connected in the proper orientation in response to the detected voltages and states of charge of the batteries 4606 , 4604 by controller 4608 .
- the DC to DC converter 4610 transfers charge between the batteries 4606 , 4604 until the voltages or states of charge are substantially equal. At that point, controller 4608 generates a control signal 4616 that closes the main switch 4614 to connect battery 4606 in parallel with battery 4604 . A substantial in-rush of current does not occur as long as the voltages of batteries 4606 , 4604 are substantially equalized by the DC to DC converter 4610 .
- FIG. 46B discloses an energy exchange battery/load equalization circuit 4650 .
- the energy exchange battery/load equalization circuit 4650 is similar to the energy exchange battery equalization circuit 4600 , illustrated in FIG. 46A .
- the difference between the circuits is that the charge on a capacitive load 4652 is equalized with the charge on battery 4654 prior to connecting the circuits to prevent damage to battery 4654 and/or load 4652 .
- Load 4652 may include a large capacitive load such as may be present at the input of a motor controller circuit.
- motor controller circuits are used in electric cars and other electric vehicles to control the application of current to the motors of the vehicles. Controller 4662 can detect the terminal voltages of the load 4652 and the battery 4654 to determine when the terminal voltages become substantially equal.
- Controller 4662 activates switch 4658 to allow the DC to DC converter 4656 to charge the load 4652 to the voltage of the battery 4654 .
- the switch 4658 is opened by controller 4662 , and the main switch 4660 is closed.
- the DC to DC converter 4656 can also be used to discharge the charge on load 4652 and apply that charge to the battery 4654 to further conserve energy. Discharging the load 4652 is also done to remove voltage from load 4652 , for safety purposes.
- FIG. 47 illustrates the manner in which a step-down converter system 4700 can be used to transfer charge between a first battery 4706 and a second battery 4708 .
- the voltage Vb 1 of battery 4706 is greater than the voltage Vb 2 of battery 4708 .
- a step-down DC to DC converter 4716 has an input 4712 that is connected to battery 4706 .
- the output of the step-down DC to DC converter 4716 is connected to battery 4708 .
- the state of charge SOC 1 of battery 4706 is greater than the state of charge SOC 2 of battery 4708 . In this manner, energy can be transferred from battery 4706 to battery 4708 in the direction of the arrow 4710 .
- a step-up converter 4716 is connected between battery 4806 and battery 4808 .
- battery 4806 is connected to the input 4812 of the step-up DC to DC converter, while the output 4814 of the step-up DC to DC converter is connected to battery 4808 .
- battery 4806 has a terminal voltage Vb 1 that is less than the terminal voltage Vb 2 of battery 4808 .
- the state of charge of battery 4806 is greater than the state of charge of battery 4808 as indicated by block 4804 .
- Battery 4806 is connected to a load 4818 that causes the terminal voltage of battery 4806 to be lower than the terminal voltage (Vb 2 ) of battery 4808 .
- battery 4806 would have a higher terminal voltage than battery 4808 .
- Vb 1 terminal voltage
- Vb 2 terminal voltage of battery 4808
- a step-up DC to DC converter 4816 must be utilized so that energy can be transferred from battery 4806 (with a higher state of charge, SOC 1 ) to battery 4808 (with a lower state of charge, SOC 2 ), in the direction shown by the arrow 4810 .
- FIG. 49 is a schematic illustration of a step-up converter system 4900 .
- the input 4912 of the step-up DC to DC converter 4916 is connected to battery 4906 .
- Battery 4906 is also connected to load 4918 .
- the output 4914 of the step-up DC to DC converter 4916 is connected to battery 4906 having a terminal voltage (Vb 1 ) that is greater than the terminal voltage (Vb 2 ) of battery 4908 .
- the state of charge of the battery 4806 is greater than the state of charge of battery 4906 , as indicated at block 4904 , even though the terminal voltage of the battery 4806 (Vb 2 ) is less than the terminal voltage (Vb 1 ) of battery 4906 .
- step-up DC to DC converter 4916 is used to transfer energy from the battery 4806 , that has a higher state of charge, to battery 4906 , which has a lower state of charge, which causes energy to flow in the direction of the arrow 4910 .
- FIG. 50 is a schematic illustration of a step-down converter system 5000 .
- battery 5008 having a terminal voltage Vb 2
- Battery 5006 having a terminal voltage Vb 1
- battery 5006 having a terminal voltage Vb 1
- battery 5008 has a terminal voltage (Vb 2 ) that is greater than the terminal voltage (Vb 1 ) of battery 5006 .
- the state of charge of battery 5008 is greater than the state of charge of battery 5006 . Accordingly, energy flows in the direction of the arrow 5010 .
- FIG. 51 is a schematic illustration of an energy exchange battery equalization circuit 5100 .
- battery 5106 has a voltage (V 1 ) and is disposed in the battery module 5102 .
- Battery 5104 has a terminal voltage (V 2 ) and is connected to the battery module 5102 .
- Controller 5104 detects the terminal voltage of battery 5106 at nodes 5132 , 5134 .
- controller 5104 detects the terminal voltage of battery 5104 at nodes 5136 , 5134 .
- a communication link from modules mounted on the batteries 5104 , 5106 can also supply this information.
- Controller 5104 may also receive signals indicating the amount of current flowing from batteries 5106 , 5104 and can calculate the state of charge of the batteries 5106 , 5104 . In response to these signals, controller 5104 can generate control signals to operate switches 5116 , 5118 , 5120 , 5122 to connect the input and the output of the step-up DC to DC converter 5112 , or activate switches 5124 , 5126 , 5128 , 5130 to connect the input and the output of step-down DC to DC converter 5114 . In this manner, energy can be transferred between the batteries 5106 , 5104 in accordance with the detected voltages, and states of charge of batteries 5106 , 5104 , in response to control signals from controller 5104 .
- the controller 5104 can activate the main switch 5110 to connect the batteries 5106 , 5104 in parallel. If the battery voltage versus the state of charge is not monotonic, or if the battery resistance is undetermined, the controller 5104 can use the state of charge information instead of a calculated open circuit voltage to determine the direction in which the DC to DC converter should transfer energy.
- the open circuit voltage of a loaded battery can be estimated by the voltage, resistance and current of the battery.
- the main switch 5110 is closed and the DC to DC converts 5112 , 5114 are isolated from the circuit.
- the controller 5104 monitors a communication link between the battery module 5102 and the battery 5104 . If the battery module 5102 becomes disconnected from battery 5104 , controller 5104 opens the main switch 5110 and the system returns to the initial condition for safety reasons.
- FIG. 52 illustrates a bi-directional, non-isolated, ⁇ uk DC to DC converter 5220 that is capable of transferring charge between batteries 5222 , 5224 .
- Switches 5230 , 5232 are alternately closed which alternately connects the capacitor 5238 in parallel across the batteries 5222 , 5224 . In this manner, voltages are temporarily stored by capacitor 5238 .
- Conductors 5226 , 5228 limit the amount of current that flows through the capacitor 5238 when the switches 5230 , 5232 are alternatively closed. The charges stored on the capacitor 5238 are transferred between the batteries 5222 , 5224 to equalize the charges on batteries 5222 , 5224 .
- Switches 5230 , 5232 are constructed from MOS technology and include diodes 5234 , 5236 , respectively, that temporarily allow current to flow through the switches 5230 , 5232 if the opening and closing of switches 5230 , 5232 are not accurately synchronized.
- the pulse width of the pulses that operate the switches 5230 , 5232 determines the flow of energy between batteries 5222 , 5224 .
- the bi-directional DC to DC converter 5220 is a variation of a ⁇ uk converter, which uses two active switches rather a single active switch.
- FIGS. 53 and 54 illustrate an inverting DC to DC converter 5300 .
- switches 5314 , 5316 are closed, which connects the inverting DC to DC converter in a reverse polarity direction so that the batteries 5302 , 5304 are connected with the proper polarity.
- Switch 5318 opens and closes at a high frequency, so that energy is stored from battery 5303 in inductor 5306 , and then transferred through diode 5308 to battery 5304 .
- switches 5314 , 5316 are opened and then switches 5310 , 5312 are closed as illustrated in FIG. 54 .
- Non-isolated DC to DC converters typically use an inductor, which provides a simpler circuit that is less expensive and allows essentially all of the input current to flow to the output.
- non-isolated DC to DC converters do not isolate the input from the output, which results in noise and other interference, that may be present on the input, to be transmitted to the output.
- the output voltage is constrained by the input voltage as explained in more detail below.
- isolated DC to DC converters isolate noise between the input and output or a first port and a second port, and the output voltage is not constrained by the polarity or level of the input voltage.
- isolated DC to DC converters employ a transformer, which is expensive and less efficient than simply using an inductor, such as employed in a non-isolated DC to DC converter.
- Non-isolated DC to DC converters are three-terminal devices.
- the output voltage of a non-isolated DC to DC converter can be either higher than the input voltage, in which case a step-up converter is used, or lower than the input voltage, in which case a step-down converter may be used, or may be the opposite polarity of the input voltage, in which case an inverting non-isolated DC to DC converter would be used.
- FIGS. 55-66 disclose various implementations of non-isolated DC to DC converters.
- FIG. 55 discloses a three-terminal, non-isolated step-up DC to DC converter system 5500 .
- battery 5502 has a voltage (Vb) and is connected to input 5506 of the step-up DC to DC converter 5510 .
- Load 5504 has a voltage (V 1 ) and is connected to the output 5508 of the step-up DC to DC converter 5510 .
- the voltage (Vb) of battery 5502 is less than the voltage (V 1 ) across the load 5504 .
- a step-up DC to DC converter 5510 is used to transfer energy from the battery 5502 to the load 5504 .
- FIG. 56 discloses a three-terminal non-isolated step-down DC to DC converter system 5600 .
- battery 5602 has a voltage (V 2 ) and is connected to the input 5606 of the step-down DC to DC converter 5610 .
- Load 5604 is connected to the output 5608 of the step-down DC to DC converter 5610 .
- the voltage (V 1 ) across load 5604 is less than the voltage (Vb) across battery 5602 . Accordingly, a step-down converter 5610 is used to transfer energy from the battery 5602 to the load 5604 .
- FIG. 57 discloses an inverting DC to DC converter system 5700 .
- battery 5702 is connected to the input 5706 of the inverting DC to DC converter 5710 .
- Load 5704 is connected to the output 5708 of the inverting DC to DC converter 5710 . Since the inverting DC to DC converter 5710 inverts the voltage, the load 5704 is connected in opposite polarity to the battery 5702 .
- FIG. 58 illustrates an isolated four-terminal DC to DC converter system 5800 .
- battery 5802 has a voltage (Vb 1 ) and is connected to the input 5806 of the isolated DC to DC converter 5810 .
- Load 5804 has a voltage (V 1 ) across its terminals and is connected to an output 5808 of the isolated DC to DC converter 5810 .
- the isolated DC to DC converter 5810 can be operated such that Vb can be less than V 1 , Vb can be equal to V 1 and Vb can be greater than V 1 .
- the polarities of the input and output voltages can be inverted.
- FIG. 59 is a schematic illustration of a flying inductor DC to DC converter system 5900 .
- battery 5902 has a voltage (Vb) and is connected to the input 5908 of the flying inductor DC to DC converter 5912 .
- Load 5904 has a voltage V 1 across its terminals and is connected to the output 5910 of the flying inductor DC to DC converter 5912 .
- Vb can be greater than V 1
- Vb can be less than V 1
- Vb can be equal to V 1 and the polarity of V 1 can be inverted with respect to Vb.
- the flying inductor DC to DC converters share many of the advantages of the isolated DC to DC converters as well as many of the advantages of the non-isolated DC to DC converters. Just like the isolated DC to DC converters, the flying inductor DC to DC converter essentially isolates noise from being transmitted between the input and the output of the flying inductor DC to DC converter. Additionally, the flying inductor DC to DC converter provides a degree of electrical isolation between its input and output. Finally, the output voltage level and polarity of the flying inductor DC to DC converter is not constrained by the input voltage level and polarity of the input voltage.
- the flying inductor topology does not require the use of an expensive and bulky transformer and has the ability to transfer essentially all of the input current to the output. Accordingly, the flying inductor DC to DC converter has advantages of both the isolated and non-isolated converters and can be effectively used as a DC to DC converter and in systems for equalizing charges on batteries or between batteries and capacitive loads.
- the flying inductor DC to DC converter system can be reduced to a three-terminal system from a four-terminal system by connecting one of the input terminals to one of the output terminals.
- the negative input terminals can be connected together
- the positive terminals can be connected together
- a negative input terminal can be connected to a positive output terminal
- a positive input terminal can be connected to a negative output terminal.
- FIGS. 60-63 illustrate these various typologies.
- FIG. 60 is a schematic illustration of the flying inductor DC to DC converter system 6000 that has the negative input terminals connected together.
- battery 6002 has a voltage Vb.
- Battery 6002 is connected through the input 6006 that includes a positive terminal and negative terminal 6010 .
- Battery 6002 supplies a voltage Vb to the flying inductor DC to DC converter 6000 .
- Load 6004 is connected to output 6008 , which has a positive terminal and a negative terminal 6012 .
- Conductor 6014 connects the negative terminals 6010 , 6012 of the flying inductor together.
- the negative terminal of the battery 6002 and the negative terminal of the load 6004 are also connected to the negative terminals of the flying inductor.
- the voltage across load 6004 is equal to V 1 .
- the topology illustrated in FIG. 60 allows the voltage Vb to be less than, greater than, or equal to the voltage V 1 .
- the flying inductor DC to DC converter 6016 can operate as a step-up or step-down converter. In that regard, it is similar to a non-isolated ⁇ uk converter, but simpler in operation.
- FIG. 61 is a schematic illustration of the flying inductor DC to DC converter system 6100 that has the positive terminals connected together.
- battery 6102 is connected to the input 6106 of the flying inductor DC to DC converter 6100 .
- Battery 6102 supplies a voltage Vb to the flying inductor DC to DC converter 6100 .
- Load 6104 is connected to the output 6108 of the flying inductor DC to DC converter 6100 .
- Load 6104 has a voltage V 1 across its terminals.
- Conductor 6110 connects the positive terminals of the input to the positive terminal of the output of the flying inductor DC to DC converter 6100 .
- the flying inductor DC to DC converter 6100 is a three-terminal device similar to the three-terminal device illustrated in FIG. 60 , but with input and out voltages that are negative with respect to common conductor 6110 . Accordingly, the flying inductor DC to DC converter 6112 can operate as a step-up converter or a step-down converter and is also similar to the non-isolated ⁇ uk converter.
- FIG. 62 is a schematic illustration of a flying inductor DC to DC converter system 6200 that has the negative input terminals connected to the positive output terminal.
- battery Vb is connected to the input 6206 of the flying inductor DC to DC converter 6200 .
- Battery 6202 supplies a voltage Vb to the flying inductor DC to DC converter 6200 .
- Load 6204 is connected to the output 6208 of the flying inductor DC to DC converter 6210 .
- the negative terminal of the input 6206 is connected to the positive terminal of the output 6208 by conductor 6203 , to render this as a three-terminal device. By connecting these terminals together, the system 6200 becomes an inverting converter, such as disclosed herein.
- FIG. 63 is a schematic illustration of a flying inductor DC to DC converter 6300 that has the positive input terminals connected to the negative output terminal.
- battery 6302 is connected to the input 6310 of the flying inductor DC to DC converter 6314 .
- Battery 6302 supplies a voltage Vb to the flying inductor DC to DC converter 6300 .
- Load 6304 is connected to the output 6312 of the flying inductor DC to DC converter 6300 .
- Load 6304 has a voltage Vb plus V 1 across its terminals since conductor 6308 connects the positive terminal of the battery 6302 to the negative terminal of the load 6304 .
- FIG. 64 illustrates a unidirectional DC to DC converter 6400 .
- energy flows in the direction from the input to the output as illustrated by arrow 6412 .
- Battery 6402 applies a voltage to the input of the unidirectional DC to DC converter 6400 that is equal to Vb.
- the load 6404 is connected to the output 6408 of the unidirectional DC to DC converter 6410 .
- the negative terminals of the battery 6402 , the load 6404 and the unidirectional DC to DC converter 6410 are connected together.
- the unidirectional DC to DC converter 6410 can only transfer energy from the input 6406 to the output 6408 in the direction of the arrow 6412 .
- FIG. 65 is a schematic illustration of a bi-directional DC to DC converter system 6500 .
- battery 6502 is connected to the first port of the bi-directional DC to DC converter 6510 and applies a voltage (Vb) to the first port 6506 .
- Battery 6504 is connected to a second port 6508 of the bi-directional DC to DC converter 6510 and applies a voltage Vb 2 to the second port 6508 .
- the bi-directional DC to DC converter 6510 is capable of transferring energy in either direction between battery 6502 and battery 6504 as illustrated by arrow 6512 .
- Bi-directional DC to DC converters may operate to transfer energy in either direction.
- Bi-directional DC to DC converters use active switches in place of rectifier diodes.
- the flying inductor DC to DC converter may also be designed to operate bi-directionally.
- the flying inductor topology suffers from several limitations.
- the flying inductor topology is inherently less efficient than a simple, non-isolated DC to DC converter because the current path includes two switches rather than one switch in the non-isolated DC to DC converter.
- the flying inductor DC to DC converter does not offer true galvanic isolation.
- the maximum voltage difference between any input terminal and any output terminal is determined by the relative value of the input and output voltages, as long as the breakdown voltages of the components used in the flying inductor DC to DC converter are sufficiently high.
- FIG. 66 illustrates a bi-directional flying inductor DC to DC converter system 6600 .
- a first voltage source 6606 has a voltage V 1 that is connected to the input 6602 of the bi-directional flying inductor DC to DC converter 6610 .
- Voltage source 6608 has a voltage (V 2 ) and is connected to the output 6604 of the bi-directional flying inductor DC to DC converter 6610 .
- the voltage constraints of the bi-directional flying inductor DC to DC converter 6610 are that the output voltage V 2 minus input voltage V 1 can only range between minus V 2 and plus V 1 .
- FIG. 67A is a schematic diagram of an embodiment of a bi-directional flying inductor DC to DC converter system 6700 , which is unable to include a dead time.
- the flying inductor DC to DC converter 6700 transfers charge in either direction between battery 6702 and battery 6704 .
- Switches 6716 , 6718 are driven by inverting buffers 6708 , 6710 , respectively.
- Switches 6720 , 6722 are driven by non-inverting buffers 6712 , 6714 , respectively.
- switches 6716 , 6718 are closed and switches 6720 , 6722 are open. This is defined as Phase A.
- switches 6716 , 6718 are open and switches 6720 , 6722 are closed. This is defined as Phase B.
- switches 6716 , 6718 are open, switches 6720 , 6722 are closed, and vice versa.
- the opening and closing of the switches is substantially simultaneous, as a result of the topology of the circuit of the flying inductor DC to DC converter 6700 .
- Inductor 6724 is therefore alternately connected between battery 6702 , and battery 6704 . Current in the inductor 6724 increases, decreases, and changes direction, depending upon the pulse width of the pulse waveform generator 6706 .
- Each of the switches 6720 , 6722 , 6516 , 6518 may be implemented with a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) that includes a reverse rectifier diode.
- MOSFET Metal Oxide Semiconductor Field Effect Transistor
- the reverse rectifier diodes allow for slight variations in the simultaneity of the opening and closing of the switches.
- MOSFETs and IBGTs include intrinsic reverse rectifier diodes as part of their structure. Discrete rectifier diodes may be added in parallel with each switch to improve performance of the intrinsic rectifier diodes, or for switches that do not include an intrinsic rectifier diode.
- FIG. 67B is a schematic diagram of another embodiment of a bi-directional flying inductor DC to DC converter system 6720 , which is able to include a dead time.
- the flying inductor DC to DC converter 6720 transfers charge in either direction between battery 6702 and battery 6704 .
- Switches 6716 , 6718 are driven by buffers 6728 , 6730 , respectively.
- switches 6716 , 6718 are closed.
- switches 6716 , 6718 are open.
- Switches 6720 , 6722 are driven by buffers 6712 , 6714 respectively.
- switches 6720 , 6722 are closed.
- switches 6720 , 6722 are open.
- switches 6716 , 67518 close and open together.
- switches 6720 , 6722 alternately close and open together.
- waveforms 6740 and 6741 are both low, switches 6712 , 6722 , 6728 and 6730 are all open. This is the Dead Time. Waveforms 6740 and 6741 are never both high.
- Inductor 6724 is therefore alternately connected between battery 6702 , and battery 6704 or not connected to either battery 6702 or battery 6704 .
- Current in the inductor 6724 increases, decreases, and changes direction, depending upon the timing of the pulse waveforms 6740 , 6741 from generator 6736 . In this fashion, waveform generator 6736 can control the direction and amount of energy transferred between batteries 6702 , 6704 .
- FIGS. 68-70 illustrate the three operating phases of the bi-directional flying inductor DC to DC converter of FIG. 67B .
- FIG. 68 illustrates the phase-A 6800 operating mode of the flying inductor DC to DC converter.
- switches 6806 , 6808 are in a closed position and switches 6810 , 6812 are in an open position.
- the voltage source V 1 is applied across inductor 6814 , with the polarity illustrated in FIG. 68 .
- Voltage source V 2 6804 is isolated from the inductor.
- FIG. 69 illustrates the operation of the flying inductor DC to DC converter in phase-B 6900 .
- switches 6810 , 6812 are in a closed position, while switches 6806 , 6808 are in an open position.
- Voltage source V 2 is applied to inductor 6814 with the polarity illustrated in FIG. 69 .
- Voltage source V 1 6802 is isolated from inductor 6814 .
- FIG. 70 is a schematic illustration of the flying inductor DC to DC converter in a dead time phase 7000 .
- switches 6806 , 6808 , 6810 , 6812 are all in an open position.
- Inductor 6814 is isolated from both voltage sources 6082 , 6804 .
- the switches illustrated in FIGS. 68-70 may be implemented as active switches, such as transistors, such as MOSFETs, IGBTs, BJTs, or thyristors, such as SCRs, GTOs, TRIACs. In some cases, isolation of the voltage sources is not complete because of the structure of these switches, such as MOSFETs and IBGTs, as explained in more detail below.
- active switches such as transistors, such as MOSFETs, IGBTs, BJTs, or thyristors, such as SCRs, GTOs, TRIACs.
- FIG. 71 is a schematic diagram of a uni-directional flying inductor DC to DC converter system 7100 .
- a voltage source 7102 supplies a voltage (V 1 ) to the uni-directional flying inductor DC to DC converter 7100 .
- the uni-directional flying inductor DC to DC converter 7100 has two active switches 7106 , 7108 , and two rectifier diodes 7114 , 7116 .
- Switch 7106 is operated by non-inverting buffer 7110 .
- Switch 7108 is operated by inverting buffer 7112 .
- Waveform generator 7118 generates a variable duty cycle square wave waveform that operates buffers 7110 , 7112 .
- switches 7106 , 7108 are closed.
- switches 7106 , 7108 are open.
- switches 7106 , 7108 when closed, allow current to flow from the voltage source 7102 through the inductor 7120 in a direction from left to right, as illustrated in FIG. 71 .
- diodes 7114 , 7116 allow current to flow through the inductor 7120 from left to right through load 7104 .
- the current decays linearly over time when the current is applied to the resistive load 7104 . If the energy in inductor 7120 is depleted, current ceases to flow, during the dead time. In this manner, energy is transferred from the voltage source 7102 to the load 7104 in the uni-directional flying inductor DC to DC converter 7100 , illustrated in FIG. 71 .
- FIG. 72 is a graph of inductor current versus time of the uni-directional flying inductor DC to DC converter illustrated in FIG. 71 that is operating in a discontinuous mode.
- the inductor current increases in a direction from left to right (positive direction), as illustrated in FIG. 71 , because the voltage V 1 is supplied across inductor 7120 .
- switches 7106 , 7108 are opened at the end of the time period phase-A 7202 , diodes 7114 , 7116 conduct the current through the inductor 7120 through the load 7104 .
- the inductor current decays to zero through the time period phase-B 7104 , until the current reaches zero.
- waveform generator 7118 During dead time 7206 , the output of waveform generator 7118 remains low, so switches 7106 , 7108 remain open. At the end of the period of dead time 7106 , waveform generator 7118 generates a pulse so that switches 7106 , 7108 are closed, which begins phase-A again.
- FIG. 73 is a graph of inductor voltage versus time for the uni-directional DC to DC converter, which is operating in the discontinuous mode, such as illustrated in FIG. 72 .
- the voltage across inductor 7120 is equal to V 1 .
- the voltage (V 1 ) of voltage source 7102 is applied across the inductor 7120 , as a result of switches 7110 , 7112 being closed.
- phase-B 7304 the voltage across inductor 7120 is equal to the negative of voltage of load 7104 , ⁇ V L , since switches 7106 , 7108 are open and the voltage across load 7104 is applied across the inductor 7120 in a direction opposite (negative polarity) to the voltage applied by the voltage source 7102 .
- zero voltage is applied across the inductor 7120 . The process then begins again with phase-A 7308 .
- FIG. 74 is a schematic illustration of the phase-A operation 7400 of the uni-directional flying inductor DC to DC converter.
- switches 7404 , 7406 are on and diodes 7414 , 7416 are off.
- Waveform generator 7422 is high, which causes buffers 7406 , 7412 to generate an output to close switches 7404 , 7410 , so that current 7420 flows through switch 7404 , inductor 7408 and switch 7410 .
- load 7418 is substantially isolated from the voltage source 7402 .
- FIG. 75A is a schematic illustration of the phase-B operation 7500 of the uni-directional flying inductor DC to DC converter.
- the output 7422 of waveform generator 7422 is low, which, through buffers 7406 and 7410 , drives switches 7404 and 7410 respectively in an open condition.
- the voltage 7402 of voltage source is isolated from inductor 7408 .
- the current 7520 in inductor 7408 which was generated during phase-A operation and which cannot be interrupted, creates a voltage across inductor 7408 of the opposite polarity from phase A of FIG. 74 , until its amplitude is sufficiently high to forward-bias rectifier diodes 7414 and 7416 .
- inductor 7408 is connected to load 7418 , and current 7520 flows into load 7418 .
- the current flowing through load 7418 in the manner illustrated in FIG. 75 , decays due to dissipation from the resistive load 7418 .
- Phase B ends when the current 7520 in inductor 7408 has decreased to 0, at which point the entire energy in the inductor 7408 has been transferred to load 7418 .
- the switches 7404 , 7410 of FIG. 75 are assumed to open essentially simultaneously at the transition between phase-A and phase-B. However, there can be a short period between the end of phase-A and the beginning of phase-B during which only one of switches 7404 , 7410 remains closed.
- FIGS. 75B, 75C illustrate the current flow into an external circuit that results from the loss of isolation due to mismatch in the opening and closing times of switches 7404 , 7410 .
- switch 7404 were to open first, the current 7420 of FIG. 74 would be interrupted, but the current 7520 would start immediately, because the current through inductor 7408 cannot be interrupted. This would connect the inductor 7408 to load 7418 through forward biased diode rectifiers 7414 , 7416 , as illustrated in FIG. 75A .
- switch 7410 would is still closed, connecting the negative terminal of voltage source 7402 to the positive terminal of load 7418 .
- switch 7410 were to open first, the current 7420 of FIG.
- an impulse of current 7532 flows in the clockwise direction through an external circuit 7536 during the time that switch 7404 , is closed and switch 7410 is open.
- an impulse 7534 of current flows in the counter-clockwise direction through the external circuit 7536 during the time that switch 7410 , is closed and switch 7404 is open.
- the current of these pulses can be limited through the use of low pass filter 7530 . If these current impulses are symmetrical, there is no net DC flow in the external circuit. However, an asymmetrical mismatch between the opening and closing times of switches 7404 and 7410 results in a net flow of DC current through the external circuit. To minimize this loss of isolation, the opening and closing moments of switches 7404 and 7410 must be synchronized to a great extent. At the minimum, the asymmetry in the times must be minimized, so that only AC flows in the external circuit which can be minimized through the use of filter 7530 .
- FIG. 76 is a schematic illustration of the dead time operation 7600 of a uni-directional flying inductor DC to DC converter.
- switches 7404 , 7410 are open, since buffers 7406 , 7412 are off, as a result of the waveform generator 7422 being in a low condition.
- the voltage source 7402 is therefore substantially isolated from the load 7418 during the dead time.
- FIG. 77 is a graph 7700 of inductor current of the uni-directional flying inductor DC to DC converter 7100 that is operating in critical mode.
- inductor current gradually builds, since the voltage V 1 is applied across the inductor 7408 .
- the switches 7404 , 7410 are opened and the current 7424 ( FIG. 75 ), through the inductor 7408 , decays as a result of dissipation and the resistive load 7418 .
- switches 7404 , 7410 are closed, as a result of the waveform generator 7422 going high, and another phase-A 7706 is initiated and the current again starts to build in the inductor 7408 .
- FIG. 78 is a graph 7800 of inductor voltage of a uni-directional flying inductor DC to DC converter 7100 operating in critical mode.
- the voltage waveform 7808 has a voltage equal to V 1 during phase-A 7802 .
- the voltage waveform 7808 has a voltage equal to the negative of the load voltage, ⁇ VL.
- the voltage waveform then returns to the voltage V 1 during phase C 7806 .
- Phase-B is timed so that the inductor current decreases to 0 when the next phase is initiated.
- FIG. 79 is a graph 7900 of inductor current of a uni-directional flying inductor DC to DC converter 7100 in continuous mode.
- the continuous mode of operation is similar to the critical mode, except that the next phase is initiated before the current 7424 decays to zero so that there is still current in the inductor 7408 .
- the new phase is started and more current is added to the inductor 7408 , which is an addition to the current that is already flowing in the inductor.
- the continuous mode of operation is considered continuous because there is always current flowing in the inductor 7408 .
- the amount of energy transferred is regulated by adjusting the pulse width modulation of the control signal, which is the ratio of the duty cycle of phase-A versus the sum of phase-A plus phase-B.
- phase-A 7902 inductor current increases to I 2 , as illustrated by plot 7908 .
- Phase-B 7904 is such that the current decreases to I 1 as shown by current plot 7908 .
- Phase-B is shown as shorter, Phase-B could be longer, depending upon the ratio of the input and output voltage.
- Phase-A 7906 then begins again before the inductor current 7908 decreases to zero.
- FIG. 80 is a plot 8000 of conductor voltage of a uni-directional flying inductor DC to DC converter 7100 versus time that is operating in a continuous mode. As illustrated in FIG. 80 , during phase-A 8002 , the inductor voltage is at voltage level V 1 . During phase-B 8004 the inductor voltage is the negative of the load voltage, V.
- FIG. 81A is an illustration of another embodiment 8100 of a uni-directional flying inductor DC-DC converter, using a biased inductor.
- the current in inductor 7408 in FIG. 74 flows in only one direction, therefore using only one half of the available magnetization of inductor 7408 .
- Use of a magnetically biased inductor 8102 allows use of the full range of the available magnetization of inductor 8102 , and therefore allows the use of a physically smaller inductor for a given amount of power transferred.
- FIG. 81B is an illustration of the uni-directional flying inductor DC to DC converter 8100 illustrating an analysis of the isolation limits of the uni-directional flying inductor DC to DC converter 8100 with the load pulled as far negative as possible.
- Node 8114 on the negative terminal of voltage source 8102 , is the reference, by definition at 0 Volt.
- Node 8116 on the positive terminal of load 8104 , can be pulled in the negative direction until rectifier diode 8108 and the intrinsic diode in switch 8112 are forward biased. At that point, the voltage drop across rectifier diode 8108 is approximately 1 V, as is the voltage drop across the intrinsic diode in switch 8112 .
- the voltage of terminal 8116 is unable to go any more negative than 2 V below the reference node 8114 .
- the voltage on node 8118 , on the negative terminal of load 8104 is lower than the voltage on node 8116 , on the positive terminal of load 8104 , by an amount equal to the voltage across the load 8104 . Therefore, the voltage on node 8118 is unable to go any more negative than the load voltage, VL, plus 2 V. In other words, the negative end of load 8104 is clamped to ⁇ VL ⁇ 2 V.
- the voltage on node 8118 will not be clamped if the components 8108 , 8112 are not allowed to be forward biased, that is if the voltage on node 8118 is not allowed to go below ⁇ VL, the negative of the voltage of the load 8104 .
- FIG. 82 is the illustration of the uni-directional, flying inductor DC to DC converter 8100 illustrating an analysis of the isolation limits of a uni-directional flying inductor DC to DC converter 8100 with the load pulled as far positive as possible.
- Node 8116 on the negative terminal of voltage source 8102 , is the reference, by definition at 0 Volt.
- Node 8118 on the negative terminal of load 8104 , can be pulled in the positive direction until rectifier diode 8106 and the intrinsic diode in switch 8110 are forward biased. At that point, the voltage drop across rectifier diode 8106 is approximately 1 V, as is the voltage drop across the intrinsic diode in switch 8110 .
- the voltage of terminal 8118 is unable to go any more positive than 2 V above the voltage of node 8122 on the positive terminal of voltage source 8102 .
- the voltage on node 8122 is higher than the voltage on reference node 8114 , on the negative terminal of voltage source 8102 , by V 1 . Therefore, the voltage on node 8118 is unable to go any more positive than the voltage source voltage, V 1 , plus 2 V. In other words, the negative end of load 8104 is clamped to V 1 ⁇ 2 V.
- the voltage on node 8118 will not be clamped if the components 8106 , 8110 are not allowed to be forward biased, that is if the voltage on node 8118 is not allowed to go above V 1 , the voltage of the voltage source 8102 .
- FIGS. 81A, 81B and 82 show that the voltage source 8102 , and the load 8104 , are essentially isolated from each other as long as the voltage on node 8118 remains within the range ⁇ VL and V 1 , where VL is the voltage of the load 8104 , and V 1 is the voltage of the voltage source 8012 . Outside of that range, the uni-directional, flying inductor DC-DC converter is not isolated.
- FIG. 83 is a schematic illustration of another embodiment 8300 of the uni-directional DC-DC converter that has a higher isolation voltage range than the circuit of FIGS. 81A, 81B and 82 .
- the active switches 8110 and 8112 of FIG. 81A, 81B and 82 are replaced by bidirectional active switches 8302 and 8304 , respectively.
- bidirectional switches 8302 and 8304 When closed, bidirectional switches 8302 and 8304 are able to conduct current in either direction. When open, bidirectional switches 8302 and 8304 do not conduct current in any direction.
- a bidirectional switch may consist of two transistors in series though in the opposite direction, such as two MOSFETs, two IGBTs, two BJTs.
- a bidirectional switch may also consist of a transistor and a rectifier diode in series, with the transistor in the normal orientation, such as switches 8110 and 8112 in FIG. 82 , and the rectifier diode in the direction that is the opposite of the intrinsic diode across the transistor.
- the use of bidirectional switches removes the limitation of the circuit in FIG. 82 , because there is no longer a series of diodes that can be forward biased when the load is pulled negatively or positively.
- FIG. 84A is the illustration of a uni-directional, flying inductor, DC to DC converter 8400 that provides an analysis of the isolation limits of the uni-directional flying inductor DC to DC converter 8400 , as the load is pulled in the positive direction.
- Rectifier diodes 8312 , 8314 may have a reverse breakdown voltage of 1.2 kV, that is, they are able to withstand a voltage across them of 1200 V without conducting or damage.
- Bidirectional switches 8302 , 8304 may have a breakdown voltage of 1.2 kV, that is, they are able to withstand a voltage across them in either direction of 1200 V without conducting or damage.
- Node 8306 on the negative terminal of the voltage source 8308 is defined as a reference.
- the voltage on node 8306 is, by definition, 0 V.
- the voltage on node 8316 on the negative terminal of the load 8316 , is pulled up to positive 1 kV above the reference node 8306 .
- Rectifier diode 8312 is forward biased, allowing the positive 1 KV voltage to be applied to inductor 8318 .
- the intrinsic diode in the bottom component in bidirectional switch 8302 is also forward biased, allowing the positive 1 KV voltage to be applied to the mid-point voltage inside switch 8302 .
- the top component in bidirectional switch 8302 is oriented in the opposite direction, and is therefore reverse biased.
- bidirectional switch 8302 As the breakdown voltage of bidirectional switch 8302 is 1.2 kV, it can withstand that reverse voltage, preventing the positive 1 KV voltage to be applied to node 8307 , on the positive terminal of voltage source 8308 . Therefore, in the unidirectional, flying inductor DC-DC converter, the voltage source 8308 is isolated from the load 8310 as long as the voltage on the load 8310 is no more positive than 1 kV.
- FIG. 84B is an illustration of the uni-directional, flying inductor, DC to DC converter 8400 that provides an analysis of the isolation limits of a uni-directional flying inductor DC to DC converter 8400 , as the load is pulled in the negative direction.
- Node 8306 on the negative terminal of the voltage source 8308 is defined as a reference, at 0 V by definition.
- the voltage on node 8316 on the negative terminal of the load 8316 , is pulled down to negative 1 kV below the reference node 8306 .
- Rectifier diode 8314 is forward biased, allowing the negative 1 kV voltage to be applied to inductor 8318 .
- the intrinsic diode in the top component in bidirectional switch 8304 is also forward biased, allowing the negative 1 kV voltage to be applied to the mid-point voltage inside switch 8304 .
- the bottom component in bidirectional switch 8304 is oriented in the opposite direction, and is therefore reverse biased.
- the breakdown voltage of bidirectional switch 8304 is 1.2 kV, it can withstand that reverse voltage, preventing the negative 1 kV voltage to be applied to node 8306 . Therefore, in the unidirectional, flying inductor DC-DC converter, the voltage source 8308 is isolated from the load 8310 as long as the voltage on the load 8310 is no more negative than 1 kV.
- FIGS. 84A and 84B shows that the voltage source 8102 , and the load 8104 , are essentially isolated from each other as long as the voltage on node 8316 remains within the range ⁇ Vbreakdown and +Vbreakdown, where Vbreakdown is the breakdown voltage of the components 8312 , 8314 , 8302 , 8304 . Outside of that range, the uni-directional, flying inductor DC-DC converter with bidirectional switches is not isolated.
- FIG. 85 is a schematic illustration of a bi-directional DC to DC converter 8500 for transferring charges between voltage sources.
- two voltage sources 8502 , 8504 are connected to the bi-directional DC to DC converter 8500 .
- Waveform generator 8506 generates a waveform on output 8508 and waveform on output 8510 .
- waveform 8508 can be low, or waveform 8510 can be low, of both can be low.
- waveform 8508 and 0810 be both high.
- These waveforms are typically variable duty cycle, square wave waveforms.
- Buffers 8512 , 8514 are driven by output 8508 and close switches 8520 , 8526 on the high portion of the waveform at output 8508 of waveform generator 8506 .
- Buffers 8516 , 8518 are driven by output 8510 and close switches 8520 , 8526 on the high portion of the waveform at output 8510 .
- switches 8520 , 8526 are closed only during a first phase, phase-A and are opened otherwise.
- Switches 8522 , 8524 are closed only during a second phase, phase-B and are opened otherwise. All switches 8520 , 8524 , 8522 , 8526 are opened during a dead time phase.
- FIG. 86 is a schematic illustration of a bi-directional flying inductor DC to DC converter 8600 for transferring a charge from a voltage source 8602 to a load 8604 .
- the bi-directional DC to DC converter 8600 operates in the same manner as the bi-directional DC to DC converter 8500 , illustrated in FIG. 85 , with the exception that the pulse width of the waveform that is applied by the waveform generator 8606 controls the amount of energy that is transferred from the voltage source 8602 to the load 8604 .
- the topology of the circuits illustrated in FIGS. 85 and 86 differs from the uni-directional topology 7100 that is disclosed in FIG. 71 , in that the two rectifier diodes are replaced by active switches, making the topology of the bi-directional DC to DC converter 8600 fully symmetrical.
- the bi-directional DC to DC converter 8600 illustrated in FIG. 86 , has better efficiency than the uni-directional DC to DC converter 7600 , illustrated in FIG. 76 , since the active switches in the bi-directional DC to DC converter 8600 can be designed to have a lower voltage drop than the forward voltage drop of rectifier diodes 7414 , 7416 . Therefore, the bidirectional converter is preferable to the unidirectional converter even in unidirectional applications, due to its higher efficiency, though at a slightly higher parts cost.
- the bi-directional DC to DC converter can operate in the discontinuous mode, critical mode and continuous mode, and in either two or three phases, such as phase-A, phase-B or an optional dead time phase.
- phase-A or phase-B can occur first depending upon the direction in which power is to be transferred. For example, if phase-A occurs first, energy is transferred from a first power source to a second power source, or if phase-B occurs first, energy is transferred from a second power source to a first power source, as disclosed in more detail below.
- inductor 8726 or 9106 current flowing through an inductor, such as inductor 8726 or 9106 , from left to right is considered to be in a positive direction and current flowing through inductor 8726 or 9106 from right to left is considered to be in a negative direction.
- voltage with a voltage more positive on the right end of the inductor, such as inductor 8726 or 9106 is considered to be a positive voltage
- a voltage more negative on the right end of the inductor, such as inductor 8726 or 9106 is considered to be a negative voltage.
- FIGS. 87-90 disclose the manner in which energy is transferred from a first voltage source 8702 to a second voltage source 8728 by first initiating the operation of the bi-directional inductor DC to DC converter in phase-A.
- FIG. 87 illustrates phase-A operation 8700 of the bidirectional floating inductor DC-DC converter transferring energy in the forward direction.
- the waveform generator 8704 generates the first output 8706 in a high condition.
- buffer 8710 closes switch 8718 and buffer 8716 closes switch 8720 .
- the current 8730 flows from voltage source 8702 through switch 8718 , through inductor 8726 through switch 8720 and returns to the voltage generator 8702 , transferring energy from voltage source 8702 to inductor 8726 .
- the waveform generator 8704 generates signal 8708 in a low condition.
- buffers 8712 , 8714 open switches 8722 , 8724 , respectively, isolating inductor 8726 from the second voltage source 8728 .
- FIG. 88 illustrates the phase-B operation 8800 of the bi-directional flying inductor DC to DC converter, that is illustrated in FIG. 87 , transferring energy in the forward direction.
- the waveform generator 8704 generates a low signal on output 8706 .
- buffers 8710 , 8716 open switches 8718 , 8720 , respectively, isolating inductor 8726 from the first voltage source 8702 .
- the waveform generator 8704 generates a high signal on output 8708 .
- buffer 8712 closes switch 8722 and buffer 8714 closes switch 8724 .
- the voltage V 2 from voltage source 8728 is asserted across inductor 8726 in the manner illustrated in FIG. 88 .
- the voltage (V 1 ) that is asserted across the inductor 8726 in phase-A (in a positive direction), as illustrated in FIG. 87 is the opposite of the voltage (V 2 ) that is asserted across the inductor 8726 during phase-B (in a negative direction), as illustrated in FIG. 88 .
- the current in inductor 8726 is discharged onto second voltage source 8728 , transferring the energy stored in inductor 8726 onto second voltage source 8728 .
- the flying inductor DC-DC converter succeeded in transferring energy in the forward directions, from the first voltage source 8702 to the second voltage source 8728 .
- FIG. 89 illustrates a plot 8900 of current through the inductor for critical mode operation of the bi-directional DC to DC converter transferring energy in the forward direction illustrated in FIGS. 87-88 .
- the inductor current increases linearly from 0 during phase-A 8902 , as illustrated by the highlighted path 8730 of FIG. 87 , as a result of the voltage V 1 applied across the inductor 8726 in a positive direction.
- phase-B 8904 the current decreases linearly to zero because of the voltage V 2 that is asserted across the inductor 8726 in an opposite direction from V 1 , as illustrated in FIG.
- FIG. 89 shows the inductor current in plot 8908 , which is reduced to zero at the end of phase-B 8904 .
- the voltage of the waveform 8910 transitions to a positive voltage, which causes the inductor current 8908 to increase again during phase-A 8906 .
- FIG. 90 is a plot 9000 of the voltage across the inductor 8726 for critical mode operation of the bi-directional DC to DC converter 8700 transferring energy in the forward direction.
- the voltage 8910 is initiated at a level V 1 during phase-A 8902 .
- phase-B 8904 the voltage waveform 8910 transitions to a minus V 2 .
- Phase-A 8906 is then initiated again, so that the voltage waveform 8910 transitions to a voltage of V 1 .
- the voltage waveform 8910 is timed so that the inductor current 8908 reaches a maximum during phase-A.
- the voltage waveform 8910 has a pulse width so that the current 8908 decays to zero volts, so that critical mode operation is established.
- FIGS. 91 and 92 are illustrations of a bi-directional flying inductor DC to DC converter 9100 that transfers energy in the reverse direction.
- the processes initiated in phase-B by the waveform generator 9116 which initially generates a low condition on control line 9112 , and a high condition on control line 9114 .
- the high condition in control line 9114 causes buffers 9107 , 9103 to close switches 9108 , 9104 , respectively.
- the voltage (V 2 ) is applied to across inductor 9106 with a negative polarity. Buffers 9120 , 9122 are off, which causes switches 9124 , 9126 to be open. Consequently, current flows from second voltage source 910 to inductor 9106 , transferring energy from second voltage source 910 to inductor 9106 .
- FIG. 92 illustrates phase-A operation 9200 of the flying inductor DC to DC converter that transfers energy in the reverse direction.
- the waveform generator 9116 generates a low condition on control line 9114 .
- buffers 9103 , 9107 open switches 9104 , 9108 respectively, isolating the inductor 9106 from second voltage source 9110 .
- the waveform generator 9116 generates a high condition on control line 9112 .
- buffers 9121 , 9123 close switches 9122 , 9124 respectively. This causes voltage V 1 to be applied across the inductor 9106 in a positive direction, which is the opposite of the direction in which V 2 was applied to inductor 9106 during phase B of FIG. 91 .
- FIGS. 93 is a plot 9300 of the current through the inductor 9106 for critical mode operation of the bi-directional DC to DC converter transferring power in the reverse direction, illustrated in FIGS. 91-92 .
- the inductor current as shown by plot 9308 , starts from 0, then linearly increases in the negative direction since the current is flowing from right to left through the inductor 9106 , as illustrated in FIG. 91 .
- the end of phase-B 9302 as illustrated in FIG.
- the voltage V 1 from voltage generator 9120 is applied across the inductor 9106 in a positive direction during phase-A 9404 that is opposite to the voltage V 2 that is applied to inductor 9106 during phase-B 9402 .
- This causes the current to decrease linearly during phase-A to zero current.
- the voltage waveform 9308 transitions to a negative pulse, which initiates phase-B 9406 . Since the initiation of phase-B 9406 is at the same time that the current 9308 reaches zero, this is considered to be the critical mode of operation of the bi-directional DC to DC converter.
- FIG. 95 is a plot 9500 of inductor current versus time for discontinuous mode of operation transferring power in the forward direction. Compared to critical mode, discontinuous mode adds a dead time, which allows fixing the period of a complete cycle, and therefore to set the overall switching frequency.
- phase-A 9502 the current builds from zero to h.
- Phase-B 9504 has a period that depends on the ratio of V 1 over V 2 .
- the inductor current 9510 decreases to zero during phase-B.
- the current 9510 is not flowing through the inductor 9106 .
- Phase-A 9508 then starts and the current 9510 starts increasing for the period of phase-A 9508 .
- FIG. 96 is a plot 9600 of the voltage across the inductor 9106 versus time for a discontinuous mode of operation transferring energy in the forward direction.
- the voltage waveform 9512 is at a voltage level equal to V 1 during phase-A 9502 .
- phase-B 9504 the voltage 9512 transitions to minus V 2 .
- phase-A then begins again at 9508 where the voltage transitions to voltage V 1 .
- FIG. 97 is a graph 9700 of the inductor current versus time for a discontinuous mode of operation while transferring energy in the reverse direction.
- the current 9710 starts at 0 and increases in the negative direction during phase-B 9702 , which occurs first.
- Phase-A 9704 is then initiated and the voltage V 1 is applied across the inductor, which causes the magnitude of the current 9710 to decrease until the current reaches zero.
- dead time 9706 no current is flowing in the inductor since all the switches are off.
- Phase-B 9708 is then initiated and the current 9710 begins to increase negatively.
- FIG. 98 is a plot 9800 of inductor voltage 9710 versus time for a discontinuous mode of operation while transferring energy in the reverse direction.
- the voltage waveform 9712 across the inductor 9106 is initiated at phase-B 9702 with a voltage of minus V 2 since the voltage source of V 2 is applied across the inductor, such as inductor 9106 in FIG. 91 , as a negative voltage.
- Phase-A 9704 is then initiated and the voltage 9712 transitions to a positive voltage V 1 since the voltage across the inductor 9106 , as illustrated in FIG. 92 , is applied in a positive direction.
- phase-B 9708 is initiated as a negative pulse.
- FIG. 99 is a plot 9900 of inductor current 9808 versus time for a continuous mode of operation while transferring energy in the forward direction. Compared to critical mode, in continuous mode the inductor current never decays to 0. This allows the total period of a cycle to be constant, and therefore the switching frequency to be fixed. As illustrated in FIG. 99 , the inductor current 9908 starts at zero and increases during phase-A 9902 . During phase-B 9904 , a voltage equal to minus V 2 is applied across the inductor in a negative direction, which causes the current 9908 to linearly decrease to a level i 1 . Phase-A 9906 is initiated prior to the time that the current 9908 reaches zero, which causes the DC to DC converter 8500 to operate in a continuous mode.
- FIG. 100 is a plot of the voltage of the inductor for a continuous mode of operation while transferring energy in the forward direction.
- a positive voltage V 1 is applied across the inductor.
- a negative voltage minus V 2 is applied across the inductor as illustrated by voltage waveform 10008 .
- Phase-B 1004 is a period that is less than it would be for critical mode of FIG. 90 so that the current 9908 does not reach zero at the end of phase-B 10004 .
- Phase-A 10006 is initiated prior to the current 9908 reaching zero so that the flying inductor DC to DC converter is operating in a continuous mode.
- FIG. 101 is a plot 10100 of inductor current 10108 versus time for a continuous mode of operation while transferring energy in the reverse direction.
- the current 10108 starts at 0 and increases linearly in the negative direction.
- phase-A 10104 is initiated, which causes the negative current to steadily decrease.
- phase-B 10106 is initiated so that the flying bridge DC to DC converter 8500 is operating in a continuous mode.
- FIG. 102 is a plot 10200 of inductor voltage 10208 versus time for a continuous mode of operation while transferring energy in the reverse direction.
- the process initiated in phase-B 10202 with a negative voltage minus V 2 that is applied to the inductor.
- Phase-A 10204 is then initiated, which causes the voltage waveform 10208 to transition to a voltage of positive V 1 .
- Phase-B 10206 is then initiated at the end of phase-A 10204 .
- the pulse width of phase-A 10204 is less than the pulse width of phase-B 9406 of FIG. 94 for critical mode so that the current 10108 does not reach zero prior to the time that phase-B 10106 is initiated.
- FIG. 103 is an analysis of the schematic diagram of a bi-directional, flying inductor DC to DC converter 10300 using bi-directional switches.
- voltage source 10302 has a voltage V 1 .
- Voltage source 10304 has a voltage V 2 .
- the circuit illustrated in FIG. 103 operates in the same manner as described above with regard to the flying inductor converter 8500 .
- each switch is replaced with a bi-directional switch such as bi-directional switches 10306 , 10308 , 10310 , 10312 .
- the bi-directional switches 10306 - 10312 can comprise TRIACs or transistors/thyristors in series.
- bi-directional flying inductor DC to DC converter circuits such as illustrated in FIGS.
- the circuit is limited to a certain differential voltage.
- the differential voltage between negative terminal of the first power source, such as power source 8502 illustrated in FIG. 85 , and the negative terminal of the second power source 8504 may only vary between minus V 1 and plus V 2 , where V 1 is the voltage of the first power source 8502 and V 2 is the voltage of the second power source 8504 .
- the bi-directional switches 10306 - 10312 eliminate these restrictions as there is no intrinsic diode across the active switch that can be forward biased.
- the input/output voltage differential is limited by the breakdown voltage of the component used.
- switches 10306 - 10312 have a breakdown voltage of 1.2 kilovolts.
- the circuit illustrated in FIG. 103 would be able to operate within input to output differential voltage of plus or minus 1 kilovolt
- FIGS. 104, 105 illustrate other embodiments of the bi-directional, flying inductor DC-DC converter, reduced from a 4 terminal device to three terminal devices, by connecting one an input terminal to an output terminal. Such embodiments no longer provide isolation between the input and the output. Since in the 4-terminal embodiment of the lying inductor DC-DC converter the input and output are isolated, connecting one an input terminal to an output terminal is possible without affecting the operation of the flying inductor DC-DC converter.
- FIG. 104 illustrates another embodiment of the four-terminal, bi-directional flying inductor DC to DC converter system 10400 , reduced to a three-terminal device with negative input and output.
- the positive terminal of batteries 10402 , 10404 are connected together by conductor 10410 .
- the positive terminal of battery 10404 is connected to conductor 10408 . Since the switches are alternately opened and closed, conductors 10406 , 10408 can be connected at node 10410 without changing the operation of the circuit.
- FIG. 105 is another embodiment of the four-terminal, bi-directional flying inductor DC to DC converter 10500 , reduced to a three-terminal device with positive input and output.
- the flying inductor DC to DC converter 10500 includes batteries 10502 , 10504 that have their negative terminals that are connected to each other through conductor 10510 . Since the switches 10512 , 10514 , 10516 , 10518 are alternately opened and closed, conductor 10506 , 10508 can be connected at node 10510 without changing the operation of the flying inductor DC to DC converter 10500 .
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
- Secondary Cells (AREA)
- Dc-Dc Converters (AREA)
Abstract
Disclosed is a battery and load equalization circuit that prevents the in-rush of current when batteries and/or loads are initially connected in parallel. Various techniques are used including charging, discharging and use of DC to DC converters to equalize charges between batteries and between batteries and capacitive loads.
Description
- The present application is a Divisional of U.S. patent application Ser. No. 13/544,100, filed Jul. 9, 2012, now U.S. Pat. No. ______. This Divisional application claims the benefit of U.S. patent application Ser. No. 13/544,100, filed Jul. 9, 2012, incorporated herein by reference.
- Batteries are used as an important source of electrical energy in portable applications and can also function as important stationary electrical energy storage devices. Batteries can provide a source of electrical energy for many purposes. For example, batteries provide electrical energy for handheld devices, electric cars, various types of electronic vehicles, alternative energy storage, etc. Batteries can also be used for storage of electrical energy when sources of electronic energy are not otherwise available.
- In order to provide a sufficient supply of electrical energy, cells, as well as batteries, may be connected in parallel and/or in series. Various series/parallel connections can provide a desired current and voltage, for a wide number of applications.
- An embodiment of the present invention may therefore comprise a method of safely connecting a first battery in parallel with a second battery using chargers comprising: detecting a first terminal voltage of terminals of the first battery; detecting a second terminal voltage of terminals of the second battery; charging the first battery to a first voltage if the first terminal voltage of the first battery is less than the second terminal voltage of the second battery; charging the second battery to a second voltage if the second terminal voltage of the second battery is less than the first terminal voltage of the first battery; connecting the terminals of the first battery and the terminals of the second battery in parallel if the first voltage is sufficiently close to the second terminal voltage, or if the second voltage is sufficiently close to the first terminal voltage, so that currents flowing between the first battery and the second battery upon initially connecting the terminals of the first battery to the terminals of the second battery are less than a first maximum current
- An embodiment of the present invention may further comprise a method of safely connecting a first battery in parallel with a second battery using discharging techniques comprising: detecting a first terminal voltage of terminals of the first battery; detecting a second terminal voltage of terminals of the second battery; actively discharging the second battery to a second voltage if the terminal voltage of the second battery is greater than the terminal voltage of the first battery; actively discharging the first battery to a first voltage if the terminal voltage of the first battery is greater than the terminal voltage of the second battery; connecting terminals of the first battery and the terminals of the second battery in parallel if the second voltage is sufficiently close to the first terminal voltage, or the first voltage is sufficiently close to the second terminal voltage, so that currents created upon initially connecting the first battery and the second battery are less than a first desired maximum current.
- An embodiment of the present invention may further comprise a method of safely connecting a first battery in parallel with a second battery using DC to DC converters comprising: detecting a first terminal voltage of terminals at the first battery; detecting a second terminal voltage of terminals of the second battery; connecting an input of a step-down DC to DC converter to terminals of the first battery and an output of the step-down DC to DC converter to terminals of the second battery if the first terminal voltage is greater than the second terminal voltage; connecting the input of the step-down DC to DC converter to the terminals of the second battery and an output of the step-down DC to DC converter to terminals of the first battery if the second terminal voltage is greater than the first terminal voltage.
- An embodiment of the present invention may further comprise a method of safely connecting a first battery in parallel with a second battery using DC to DC converters comprising: detecting a first terminal voltage of terminals at the first battery; detecting a second terminal voltage of terminals of the second battery; detecting a first state of charge of the first battery; detecting a second state of charge of the second battery; connecting an input of a step-up DC to DC converter to the first battery and an output of the step-up DC to DC converter to the second battery if the state of charge of the first battery is greater than the state of charge of the second battery and if the first terminal voltage is less than the second terminal voltage; connecting an input of the step-up DC to DC converter to the second battery and an output of the step-up DC to DC converter to the first battery if the state of charge of the second battery is greater than the state of charge of the first battery and if the first terminal voltage is greater than the second terminal voltage.
- An embodiment of the present invention may further comprise a method of safely connecting a first battery in parallel with a second battery using a bi-directional DC to DC converter comprising: connecting terminals of the first battery to a first input of the bi-directional DC to DC converter; connecting terminals of a second battery to a second input of the bi-directional DC to DC converter; using the bi-directional DC to DC converter to transfer charge between the first battery and the second battery in the direction that reduces the resulting current at the moment of initial connection of the first terminals to the second terminals; connecting the terminals of the first battery to the terminals of the second battery when the first battery has a first terminal voltage and open circuit voltage that is sufficiently close to a second terminal voltage and open circuit voltage on the second battery so that currents flowing between the first battery and the second battery, when the first battery is initially connected in parallel to the second battery, are less than a maximum current.
- An embodiment of the present invention may further comprise a method of safely connecting a battery in parallel with a capacitive load using a DC to DC converter comprising: connecting terminals of the battery to a first input of the DC to DC converter; connecting terminals of the capacitive load to a second input of the DC to DC converter; using the DC to DC converter to transfer charges between the battery and the capacitive load; connecting the terminals of the battery to the terminals of the load when the battery has a first charge that is sufficiently close to a second charge on the capacitive load so that currents flowing between the battery and the capacitive load when the battery is initially connected to the capacitive load are less than a maximum current.
- An embodiment of the present invention may further comprise a system for safely connecting a first battery in parallel with a second battery using charging techniques comprising: a controller that detects a first terminal voltage of terminals of the first battery, and a second terminal voltage of terminals of the second battery; a first charger connected to the first battery, which charges the first battery to a first voltage, the first charger activated by the controller if the first terminal voltage is less than the second terminal voltage; a second charger connected to the second battery, which charges the second battery to a second voltage, the second charger activated by the controller if the second terminal voltage is less than the first terminal voltage; a switch that connects the first battery in parallel with the second battery that is activated by the controller if the first voltage is sufficiently close to the second terminal voltage, or if the second voltage is sufficiently close to the first terminal voltage, so that currents flowing between the first battery and the second battery when the switch is initially activated by the controller are less than a first maximum current.
- An embodiment of the present invention may further comprise a system for safely connecting a first battery in parallel with a second battery using automated discharging techniques comprising: a controller that detects a first terminal voltage of terminals of the first battery and a second terminal voltage of terminals of a second battery; a first switch that is activated by the controller that connects a first resistive element in parallel with the first battery to actively discharge the first battery to a first voltage if the first terminal voltage is greater than the second terminal voltage; a second switch that is activated by the controller that connects a second resistive element in parallel with the second battery to actively discharge the second battery to a second voltage if the second terminal voltage is greater than the first terminal voltage; a third switch activated by the controller, that connects the first battery in parallel with the second battery if the first voltage, if present, is sufficiently close to the second terminal voltage, or the second voltage, if present, is sufficiently close to the first terminal voltage, so that currents flowing between the first battery and the second battery, when the third switch is initially activated by the controller, are less than a first maximum current.
- An embodiment of the present invention may further comprise a system for safely connecting a first battery in parallel with a second battery using DC to DC converters comprising: a controller that detects a first terminal voltage of terminals of a first battery, and a second terminal voltage of terminals of a second battery; a step-down DC to DC converter having an input and an output; at least one switch that connects the input to the terminals of the first battery, and the output to the terminals of the second battery when the first terminal voltage is greater than the second terminal voltage, and the input to the terminals of the second battery and the output to the terminals of the first battery when the second terminal voltage is greater than the first terminal voltage.
- An embodiment of the present invention may further comprise a system for safely connecting a first battery in parallel with a second battery comprising: a bi-directional DC to DC converter having a first input and a second input; a controller that generates control signals; a plurality of first electronic switches, responsive to the control signals, that connect terminals of the first battery to a first input of the bi-directional DC to DC converter, and terminals of the second battery to a second input of the bi-directional DC to DC converter, to transfer charge between the first battery and the second battery; at least one second electronic switch that connects the terminals of the first battery in parallel to the terminals of the second battery when the first battery has a first charge that is sufficiently close to a second charge on the second battery so that current flowing between the first battery and the second battery, when the second electronic switch is activated, is less than a maximum current.
- An embodiment of the present invention may further comprise a system for safely connecting a battery in parallel with a capacitive load comprising: a DC to DC converter having a first input and a second input; a controller that generates control signals; a plurality of first electronic switches, responsive to the control signals, that connect terminals of the battery to a first input of the DC to DC converter, and terminals of the capacitive load to a second input of the bi-directional DC to DC converter, to transfer charge between the battery and the capacitive load; at least one second electronic switch that connects the terminals of the battery in parallel to the terminals of the capacitive load when the battery has a first charge that is sufficiently close to a second charge on the capacitive load so that current flowing between the battery and the capacitive load, when the second electronic switch is activate, is less than a maximum current.
- An embodiment of the present invention may further comprise an isolated, bi-directional DC to DC converter comprising: a first DC voltage source; an inductor; a first pair of switches that connected the inductor to the first DC voltage source in a first polarity direction during a first phase of operation; a second DC voltage source; a second pair of switches that connect the inductor to a second DC voltage source in a second polarity direction, that is opposite to the first polarity direction, during a second phase of operation, so that current flows in the inductor in the first polarity direction while the inductor is connected to the first voltage source, during the first phase of operation, and the current through the inductor is reduced during the second phase of operation.
- An embodiment of the present invention may further comprise an isolated, uni-directional DC to DC converter comprising: a DC voltage source; an inductor; a pair of switches that connect the inductor to the DC voltage source during a first phase of operation so that current flows through the inductor in a first direction; a load; a pair of diodes that allow the current to continue to flow through the inductor during a second phase of operation when the first pair of switches are opened and the DC voltage source is isolated from the inductor.
- An embodiment of the present invention may further comprise an isolated, uni-directional DC to DC converter comprising: a DC voltage source; an inductor; a first pair of switches that connect the inductor to the DC voltage source during a first phase of operation so that current flows through the inductor in a first direction; a load; a second pair of switches that connect the inductor to the load that allows the current to continue to flow through the inductor in the first direction during a second phase of operation when the first pair of switches are opened and the second pair of switches are substantially simultaneously closed and the DC voltage source is isolated from the inductor.
- An embodiment of the present invention may further comprise a method of converting a first DC voltage to a second DC voltage using an isolated, bi-directional DC to DC converter comprising: generating the first DC voltage using a first DC voltage source; applying the first DC voltage to an inductor using a first pair of switches that connect the first DC voltage source to the inductor in a first polarity direction; generating the second DC voltage using a second DC voltage source; applying the second DC voltage to the inductor using a second pair of switches that connect the second DC voltage source to the inductor in a second polarity direction that is opposite to the first polarity direction.
- An embodiment of the present invention may further comprise a method of converting a first DC voltage to a second DC voltage using an isolated, uni-directional DC to DC converter comprising: generating the first DC voltage using a DC voltage source; applying the DC voltage source to an inductor using at least a first pair of switches that connect the DC voltage source to the inductor that generates a current in the conductor; opening the at least first pair of switches and substantially simultaneously closing the at least second pair of switches so that the current continues to flow through the inductor into a load.
- An embodiment of the present invention may further comprise a method of converting a first DC voltage to a second DC voltage using an isolated, uni-directional DC to DC converter comprising: generating the first DC voltage using a DC voltage source; applying the DC voltage source to an inductor using at least a first pair of switches that connect the DC voltage source to the inductor that generates a current in the inductor; opening the at least first pair of switches so that current flows through the inductor and through a pair of diodes and a load connected to the diodes.
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FIG. 1 is a schematic view of an embodiment of two batteries that are wired for parallel connection through a switch. -
FIG. 2 is a schematic illustration of an embodiment of two batteries that are connected in parallel with a switch. -
FIG. 3 is a schematic illustration of an embodiment of two ideal voltage sources that are wired in parallel for connection with a switch. -
FIG. 4 is a schematic illustration of an embodiment of the two ideal voltage sources ofFIG. 3 that are connected in parallel with a switch. -
FIG. 5 is a graph of an embodiment of a current pulse produced when connecting two ideal batteries. -
FIG. 6 is a graph of the voltages that are produced when connecting two ideal batteries in parallel. -
FIG. 7 is a schematic illustration of an embodiment of two real world batteries wired for connection parallel. -
FIG. 8 is a schematic block diagram of an embodiment of the two real world batteries ofFIG. 7 that are connected in parallel with a switch. -
FIG. 9 is a plot of the current flowing between two real world batteries versus time. -
FIG. 10 is a plot of the internal, open circuit voltages of each battery. -
FIG. 11 is a schematic illustration of an embodiment of two batteries connected in parallel with highly differing voltages -
FIG. 12 is an equation illustrating the amount of current that initially flows between the two batteries with highly differing voltages are initially connected in parallel. -
FIG. 13 is a schematic illustration of an embodiment of two batteries connected in parallel with medium differing voltages. -
FIG. 14 is an equation illustrating the amount of current that initially flows between the two batteries with medium differing voltages are initially connected in parallel. -
FIG. 15 is a schematic block diagram of an embodiment of two batteries connected in parallel with low differing voltages. -
FIG. 16 is an equation illustrating the amount of current flowing when the two batteries with low differing voltages are initially connected in parallel. -
FIG. 17 is a schematic illustration of an embodiment of a pre-charge circuit in a first state. -
FIG. 18 is a schematic illustration of an embodiment of the pre-charge circuit ofFIG. 17 in a second state. -
FIG. 19 is a schematic diagram of an embodiment of the circuit ofFIG. 17 in a third state. -
FIG. 20 is a plot of the current versus time of current flowing in the circuit illustrated inFIG. 18 . -
FIG. 21 is a plot of the voltage of the capacitive load versus time in the circuit ofFIG. 18 . -
FIG. 22 is a schematic illustration of an embodiment of a post-discharge circuit in a first state. -
FIG. 23 is a schematic illustration of an embodiment of the discharge circuit illustrated inFIG. 22 in a second state. -
FIG. 24 is a plot of current flowing versus time in the discharge circuit illustrated inFIG. 23 . -
FIG. 25 is a plot of voltage of the capacitive load versus time in the circuit illustrated inFIG. 23 . -
FIG. 26 is a schematic illustration of an embodiment of a battery equalization circuit in a first state. -
FIG. 27 is an illustration of current flowing in the embodiment ofFIG. 26 versus time. -
FIG. 28 is a schematic illustration of an embodiment of the battery equalization circuit ofFIG. 26 in a second state. -
FIG. 29 is a graph of the current flowing in the circuit ofFIG. 28 versus time. -
FIGS. 30-33 are schematic illustrations of an embodiment of a battery equalization circuit in various states, whereinFIG. 30 illustrates a first battery at a lower voltage than a second battery,FIG. 31 illustrates a charger charging first battery,FIG. 32 illustrates a first battery charged to same voltage as a second battery, charger goes off, andFIG. 33 illustrates a first battery connected to a second battery. -
FIGS. 34-37 are schematic illustrations of an embodiment of a battery equalization circuit in various states, whereinFIG. 34 illustrates a first battery at a higher voltage than a second battery,FIG. 35 illustrates a charger charging a second battery,FIG. 36 illustrates a second battery charged to the same voltage as a first battery, charger goes off, andFIG. 37 illustrates a first battery connected to second battery. -
FIGS. 38-41 are schematic illustrations of an embodiment of a discharging equalization circuit in various states whereFIG. 38 illustrates a voltage of first battery that is higher than a voltage of a second battery,FIG. 39 illustrates a discharge load connected across first battery, to remove charge from the battery,FIG. 40 illustrates a first battery discharged to the same voltage as a second battery, load disconnected, andFIG. 41 illustrates a first battery connected to a second battery. -
FIGS. 42-45 are schematic illustrations of an embodiment of a discharging equalization circuit in various states. -
FIG. 46A is a schematic block diagram of an embodiment of an energy exchange equalization circuit between two batteries. -
FIG. 46B is a schematic block diagram of another embodiment of an energy exchange equalization circuit between a battery and a capacitive load. -
FIG. 47 is a schematic illustration of an embodiment of an energy exchange equalization circuit in the case that the state of charge of a first battery is greater that the second battery, using a step-down DC-DC converter. -
FIG. 48 is a schematic illustration of an embodiment of an energy exchange equalization circuit in the case that the state of charge of a first battery is greater that the second battery, using a step-up DC-DC converter. -
FIG. 49 is a schematic illustration of an embodiment an energy exchange equalization circuit in the case that the state of charge of a first battery is lower that the second battery, using of a step-up DC-DC converter. -
FIG. 50 is a schematic illustration of an embodiment of an energy exchange equalization circuit in the case that the state of charge of a first battery is lower that the second battery, using a step-down DC-DC converter. -
FIG. 51 is a schematic illustration of an embodiment of an energy exchange battery equalization circuit using a step-up DC-DC converter, a step-down DC-DC converter, and a multitude of switches. -
FIG. 52 is a schematic diagram of an embodiment of a bi-directional, same polarity DC to DC converter. -
FIG. 53 is a schematic diagram of an embodiment of an inverting DC to DC converter in a first state. -
FIG. 54 is a schematic diagram of an embodiment with the inverting DC to DC converter ofFIG. 53 disabled, and the batteries connected directly in parallel. -
FIG. 55 is a schematic diagram of an embodiment of a three-terminal, non-isolated, step-up DC to DC converter system. -
FIG. 56 is a schematic diagram of a three-terminal, non-isolated step-down DC to DC converter system. -
FIG. 57 is a schematic diagram of a three-terminal, non-isolated, inverting DC to DC converter system. -
FIG. 58 is a schematic diagram of an isolated, four-terminal DC to DC converter system. -
FIG. 59 is a schematic diagram of an embodiment of a four terminal, flying inductor, DC to DC converter system that is a transformer-less, DC-DC converter with limited isolation. -
FIG. 60 is a schematic illustration of a flying inductor DC to DC converter system that has the negative input terminals connected together. -
FIG. 61 is a schematic illustration of a flying inductor DC to DC converter system that has the positive input terminals connected together. -
FIG. 62 is a schematic illustration of a flying inductor DC to DC converter system that has the negative input terminal connected to the positive output terminal -
FIG. 63 is a schematic illustration of a flying inductor DC to DC converter system that has the positive input terminal connected to the negative output terminal -
FIG. 64 illustrates a unidirectional DC to DC converter. -
FIG. 65 is a schematic illustration of a bi-directional DC to DC converter system. -
FIG. 66 illustrates the differential voltages in a bi-directional flying inductor DC to DC converter system. -
FIG. 67A is a schematic diagram of an embodiment of a flying inductor DC to DC converter system. -
FIG. 67B is a schematic diagram of another embodiment of a flying inductor DC to DC converter system. -
FIG. 68 is a schematic diagram of the flying inductor DC to DC converter in phase-A. -
FIG. 69 is a schematic diagram of the flying inductor DC to DC converter in phase-B. -
FIG. 70 is a schematic diagram of the flying inductor DC to DC converter in a dead time phase. -
FIG. 71 is a schematic diagram of a uni-directional flying inductor DC to DC converter. -
FIG. 72 is a plot of inductor current versus time of the uni-directional flying inductor DC to DC converter illustrated inFIG. 71 that is operating in a discontinuous mode. -
FIG. 73 is a plot of inductor voltage versus time for the uni-directional DC to DC converter ofFIG. 71 . -
FIG. 74 is a schematic illustration of the phase-A operation of a uni-directional flying inductor DC to DC converter. -
FIG. 75A is a schematic illustration of the phase-B operation of a uni-directional flying inductor DC to DC converter. -
FIGS. 75B, 75C illustrate the current flow into an external circuit that results from the loss of isolation due to mismatch in the opening and closing times ofswitches -
FIG. 76 is a schematic illustration of the dead time operation of a uni-directional flying inductor DC to DC converter. -
FIG. 77 is a plot of inductor current versus time of a uni-directional flying inductor DC to DC converter that is operating in critical mode. -
FIG. 78 is a plot of inductor voltage versus time of a uni-directional flying inductor DC to DC converter operating in critical mode. -
FIG. 79 is a plot of inductor current versus time of a uni-directional flying inductor DC to DC converter in continuous mode. -
FIG. 80 is a plot of inductor voltage of a uni-directional flying inductor DC to DC converter versus time that is operating in a continuous mode. -
FIG. 81A is a schematic diagram of a uni-directional, flying inductor, DC to DC converter employing a biased inductor. -
FIG. 81B is a schematic illustration of a uni-directional flying inductor DC to DC converter indicating the path of current that limits the input-output isolation when the voltage of the load is more negative than the voltage of the power source. -
FIG. 82 is a schematic illustration of a uni-directional flying inductor DC to DC converter indicating the path of current that limits the input-output isolation when the voltage of the load is more positive than the voltage of the power source. -
FIG. 83 is a schematic illustration of a uni-directional flying inductor DC to DC converter using bi-directional active switches, indicating the path of current that limits the input-output isolation when the voltage of the load is more negative than the voltage of the power source. -
FIG. 84A is a schematic illustration of a uni-directional flying inductor DC to DC converter using bi-directional active switches, indicating the path of current that limits the input-output isolation when the voltage of the load is more positive than the voltage of the power source. -
FIG. 84B is a schematic illustration of a uni-directional flying inductor DC to DC converter using bi-directional active switches, indicating the path of current that limits the input-output isolation when the voltage of the load is more negative than the voltage of the power source. -
FIG. 85 is a schematic illustration of a bi-directional DC to DC converter for transferring charges between voltage sources. -
FIG. 86 is a schematic illustration of a bi-directional DC to DC converter for transferring a charge from a voltage source to a load. -
FIG. 87 is a schematic illustration of a bi-directional flying inductor DC-DC converter transferring power from V1 to V2, in phase-A. -
FIG. 88 is a schematic illustration of a bi-directional flying inductor DC-DC converter transferring power from V1 to V2, in phase-B. -
FIG. 89 is a plot of current through the inductor versus time for critical mode operation of the bi-directional DC to DC converter ofFIGS. 87 and 88 as the power transfer direction is from V1 to V2. -
FIG. 90 is a plot of the voltage across the inductor versus time for critical mode operation of the bi-directional DC to DC converter, regardless of the direction of power transfer. -
FIG. 91 is an illustration of a bi-directional flying inductor DC to DC converter illustrating the power transfer direction from V2 to V1 that is initiated, in a phase-B operation. -
FIG. 92 illustrates the phase-A operation of the flying inductor DC to DC converter ofFIG. 91 showing the power transfer direction from V2 to V1, in a phase-A. -
FIG. 93 is a plot of the current through the inductor versus time for critical mode operation of the bi-directional DC to DC converter, showing the direction of power transfer is from V2 to V1, as illustrated inFIGS. 91 and 92 . -
FIG. 94 is a plot of inductor current versus time for critical mode operation of the bi-directional DC to DC converter, showing the direction of power transfer from V2 to V1. -
FIG. 95 is a plot of inductor current versus time for discontinuous mode of operation of the bi-directional DC to DC converter, as the direction of power transfer is from V1 to V2. -
FIG. 96 is a plot of the inductor voltage versus time for a discontinuous mode of operation of the bi-directional DC to DC converter, as the direction of power transfer is from V1 to V2. -
FIG. 97 is a plot of the inductor current versus time for a discontinuous mode of operation of the bi-directional DC to DC converter, as the direction of power transfer is from V2 to V1. -
FIG. 98 is a plot of inductor voltage versus time for a discontinuous mode of operation of the bi-directional DC to DC converter, as the direction of power transfer is from V2 to V1. -
FIG. 99 is a plot of inductor current versus time for a continuous mode of operation as the direction of power transfer is from V1 to V2. -
FIG. 100 is a plot of inductor voltage versus time for a continuous mode of operation as the direction of power transfer is from V1 to V2. -
FIG. 101 is a plot of inductor current versus time for a continuous mode of operation as the direction of power transfer is from V2 to V1. -
FIG. 102 is a plot of inductor voltage versus time for a continuous mode of operation was the direction of power transfer is from V2 to V1. -
FIG. 103 is a schematic diagram of a bi-directional, flying bridge DC to DC converter using bi-directional switches. -
FIG. 104 is a schematic diagram of a flying inductor DC to DC converter system converted to a three terminal device by connecting the positive terminals together. -
FIG. 105 is a schematic diagram of a flying inductor DC to DC converter converted to a three terminal device by connecting the negative terminals together. -
FIG. 1 is a schematic view of an embodiment of two batteries that are wired for connection in parallel through aswitch 108. As shown inFIG. 1 ,battery 100 can be schematically illustrated as avoltage source 104 having a voltage V1 and aseries resistance 110. Similarly,battery 102 is schematically illustrated as avoltage source 106 having a voltage V2 and aseries resistance 112. The twobatteries switch 108. -
FIG. 2 is a schematic illustration of the batteries illustrated inFIG. 1 , which are connected in parallel. As illustrated inFIG. 2 ,battery 100 includes avoltage source 104 and aninternal series resistance 110.Battery 102 includes avoltage source 106 and aninternal series resistance 112. When theswitch 108 is connected, current 110 flows between the two batteries if the terminal voltages of the batteries are different. As illustrated inFIG. 2 , the terminal voltage ofbattery 100 is greater than the terminal voltage ofbattery 102 so the current 110 flows in the direction of the arrow frombattery 100 tobattery 102. The difference in the terminal voltages as well as the magnitude of the internal resistances of the batteries control the magnitude of the current 110 that flows between the parallelconnected batteries -
FIG. 3 is a schematic illustration of an embodiment of twoideal voltage sources switch 304. As illustrated inFIG. 3 , theideal voltage source 300 includes avoltage source 306 that produces a voltage V1 without any series resistance.Ideal voltage source 302 includes avoltage source 308 that produces a voltage V2 without any series resistance.Switch 304 is used to connect theideal voltage source 300 in parallel with theideal voltage source 302. -
FIG. 4 is a schematic block diagram of the embodiment ofFIG. 3 with theswitch 304 closed. As shown inFIG. 4 , theideal voltage source 300 is connected in parallel throughswitch 304 to theideal voltage source 302. Current 310 flows in the direction of the arrow when V1 is greater than V2. Sincevoltage source 300 is an ideal voltage source andvoltage source 302 is an ideal voltage source, instantaneous current 310, upon closingswitch 304, is infinite. -
FIG. 5 is a graph of the current 310 versus time. Theplot 500 shows aninfinite pulse 502 of current 310 that occurs at t=0 when theswitch 304 is closed. -
FIG. 6 is a plot of voltage versus time. As shown inFIG. 6 , theplot 606 shows theindividual voltages voltages ideal voltage sources current pulse 502 is infinite -
FIG. 7 is a schematic illustration of an embodiment of two batteries that are wired for connection in parallel byswitch 704. As illustrated inFIG. 7 ,voltage source 710 having a voltage V1 is connected in series withseries resistance 706 inbattery 700.Battery 702 includes avoltage source 712 having a voltage V2 that is connected in series withseries resistance 708.Switch 704 is in an open position until time t=0. -
FIG. 8 is a schematic illustration of the embodiment ofFIG. 7 withswitch 704 closed. As illustrated inFIG. 8 ,battery 700, which includes thevoltage source 710 having voltage V1 andseries resistance 706, is connected in parallel usingswitch 704 withbattery 702, which has avoltage source 712, having a voltage V2, that is connected toseries resistance 706. Whenswitch 704 is closed, current 714 flows frombattery 700 tobattery 702 assuming V1 is greater than V2. -
FIG. 9 is a graph of current versus time for the current 714 flowing betweenbattery 700 andbattery 702 inFIG. 8 . As shown inFIG. 9 , the current 714 increases instantaneously at time t=0, whenswitch 704 is closed, and gradually decays to 0 current asbatteries FIG. 9 is proportional to the difference in the terminal voltages ofbatteries series resistance batteries FIG. 9 is proportional to the sum of the capacities ofbatteries series resistances -
FIG. 10 is a plot of the open circuit voltages ofbattery 710 andbattery 712 versus time. Prior to theswitch 704 being closed at t=0, the voltages V1 and V2 ofbatteries FIG. 10 . At t=0, the voltages gradually equalize to create a third voltage (V3) 716, which is the average of V1 and V2, assuming thatbattery batteries series resistances FIG. 9 , until enough charge has been transferred between the batteries to equalize the voltage, as illustrated inFIG. 10 The level of the current resulting from the initial interconnection of two batteries in parallel may be on the order of 0.1 C to 100 C (where C is the value of the capacitance of the battery), depending on the chemistry and the state of charge levels of the two batteries. A current of 1 C means that such current, if sustained, would discharge a full battery in 1 hour. Similarly, a current of 0.1 C means that such current, if sustained, would discharge a full battery in 10 hours. Similarly, a current of 100 C means that such current, if sustained, would discharge a full battery in 36 seconds, which is 1/100th of an hour. Batteries can typically handle currents of up to 1 C, although a charging current of 1 C may be a problem for some cells. Charging currents of greater than 1 C are often too much current for charging a battery. Batteries that have a steep slope in their voltage versus state of charge curve, and a very low internal resistance and are close to being full, present an extreme case for charging currents, since when a cell is completely full, the internal charging resistance of the cell increases, thereby reducing the resulting current. - This extreme case exists for lithium ion batteries using “high power” cells. High power cells have a resistance that is particularly low (on the order of 25 mOhm*Ah) and the slope of the voltage versus state of charge curve for these cells is somewhat steep, especially when the cells are nearly full (on the order of 250 mV/1% SOC). As a consequence, when two such batteries, one at 100 percent SOC and the other at 90 percent SOC, are connected together in parallel, the initial current will be on the order of 100 C. The initial current of 100 C quickly drops to a lower value, but the initial current can be damaging, especially to the battery being charged. Lithium ion cells are normally rated to handle as much as 30 C of discharging current and therefore a mostly charged cell may be able to handle being connected in parallel with a lesser charged cell. However, lithium ion cells should only be charged at 0.5 C, or at most, 4 C. Therefore, cells will be damaged if charged at 100 C.
- Lithium ion cells may be particularly sensitive to abuse, and they react by exploding and bursting in flames. Accordingly, the most care must be exercised when connecting such batteries in parallel. Lithium ion batteries should be connected directly in parallel only when the voltages on these batteries are equal or nearly equal so that the resulting current is minimized and damage does not occur to the batteries or cells.
- In fact, applications that use any batteries with low series resistance require methods of safely connecting these batteries in parallel to avoid damage that may occur from excessive currents on initial connection. The peak surge current when two batteries are connected in parallel is equal to the difference in voltage divided by the total series resistance in the circuit, which is mostly the internal resistance of the batteries. To reduce that peak, either the numerator, which is the difference in the voltages of the batteries, should be minimized, or the denominator, which is the total series resistance, should be maximized. Newer battery technologies are characterized by low internal series resistance which is a desirable feature. Hence, attempting to reduce the peak current by increasing the series resistance is not a viable solution since increasing the series resistance will result in a significant amount of energy being dissipated as heat during normal operation. As such, minimizing the difference in battery voltages presents the best technique for minimizing initial peak currents when batteries are initially connected in parallel.
-
FIG. 11 is a schematic illustration of an embodiment of two parallelconnected batteries 1100. As illustrated inFIG. 11 ,battery 1102 includes avoltage source 1114 having a voltage (V1) that is equal to 12 volts. Theseries resistance 1110 ofbattery 1102 is 0.5 mOhm.Battery 1104 has a voltage source 1116 having a voltage V2 that is equal to 10 volts. Theseries resistance 1112 is the same asseries resistance 1110 ofbattery 1102, which is 0.5 mOhm. -
FIG. 12 is acalculation 1200 of the initial current 1106 created whenbatteries FIG. 11 . As shown inFIG. 12 , the initial current is the difference in the voltages, i.e., 12 volts minus 10 volts (2.0 volts), which is divided by the total of the series resistances, which is 1 mOhm. This results in an initial current of 2,000 amps. -
FIG. 13 is a schematic illustration of an embodiment of two parallelconnected batteries 1300.Battery 1302 is connected in parallel withbattery 1304 byswitch 1308. Voltage source 1314 ofbattery 1302 provides a voltage of 10.2 volts. The series resistance 1310 ofbattery 1302 is 0.5 mOhm.Battery 1304 includes a voltage source 1316, which provides a voltage V2 equal to 10 volts.Series resistance 1312 ofbattery 1304 is 0.5 mOhm. Whenswitch 1308 is closed, current 1306 flows betweenbatteries -
FIG. 14 is an equation illustrating acalculation 1400 of the initial current 1306 that flows between the twobatteries switch 1308 is initially closed. As illustrated inFIG. 14 , the current (i) 1306 is equal to the difference in voltages, which is 10.2 volts minus 10 volts (0.2 volts) divided by the total resistance of the two batteries, which is 1 mOhm. The initial current is calculated as 200 amps. Hence, the change of voltage from a difference of 2 volts to a difference of 0.2 volts reduces the initial current by an order of magnitude from 2000 amps to 200 amps. -
FIG. 15 is a schematic illustration of an embodiment of two parallelconnected batteries 1500. As illustrated inFIG. 15 ,battery 1502 includes a voltage source that has a voltage V1 equal to 10.02 volts. Theseries resistance 1510 of thebattery 1502 is 0.5 mOhm.Battery 1504 has a voltage source 1516 that has a voltage V2 equal to 10 volts. Theseries resistance 1512 ofbattery 1504 is 0.5 mOhm.Switch 1508 connectsbattery 1502 in parallel withbattery 1504 so that a current 1506 flows between the batteries. -
FIG. 16 is acalculation 1600 of the initial current 1506 that flows betweenbattery 1502 andbattery 1504 when initially connected. The current (i) 1506 is equal to the difference in voltages 10.02 minus 10 volts, which is 0.02 volts, divided by the total series resistance ofbatteries FIG. 14 . - Accordingly,
FIGS. 11-16 illustrate the manner in which the initial current can be greatly reduced by connecting batteries that have output voltages that are very close.FIGS. 11-16 also provide a perspective that a difference between the batteries of only 0.02 volts can still result in an initial current of 20 amps. - These same problems are also encountered when a battery is connected to a load that has a large capacitance. The initial in-rush of current to charge up the capacitor of the load to the battery voltage can result in damage to the battery, the load, and/or interconnections between the battery and the load.
- As illustrated in
FIG. 17-21 , precharging of a load can be used to equalize the charge on the load and the battery, which can limit the initial in-rush of current when the capacitive load and the battery are initially connected. As illustrated inFIG. 17 , battery 1702 has a voltage V1.A precharge resistor 1710 is used, which may have a resistance of 100 ohms.Precharge switch 1708 is used to connect the battery 1702 to acapacitive load 1704 to charge theload 1704 to a charge level that is substantially equal to the charge level V1 of battery 1702. - As shown in
FIG. 18 ,pre-charge switch 1708 is closed, and current flows from the battery 1702 to charge theload 1704. The precharge switch remains closed until the battery 1702 andload 1704 are equalized. - As illustrated in
FIG. 19 , once thecapacitive load 1704 is charged to the voltage V1, themain switch 1706 is closed and thepre-charge switch 1708 is opened. Current can then flow from the battery 1702 directly to theload 1704, such as during operation of theload 1704. Theprecharge resistor 1710 is eliminated from the circuit since thepre-charge switch 1708 is open. -
FIG. 20 illustrates agraph 1900 that illustrates the current by flowing from the battery 1702 through theload 1704 when thepre-charge switch 1708 is initially connected. As illustrated inFIG. 20 , the initial current has a spike, which gradually decays. The initial current is equal to V1 over R, which may range from approximately 10 amps to 100 amps. -
FIG. 21 is a graph of the voltage across theload 1704 versus time. As shown inFIG. 21 , thevoltage plot 1704 of the voltage across theload 1704 increases rapidly until it reaches the battery voltage V1 at approximately t=1. - The use of a resistor, such as
precharge resistor 1710, as illustrated inFIGS. 17-21 , for precharging has the disadvantage of dissipating energy, which is undesirable in situations in which battery charge is a valuable commodity. An additional surge may occur when the main switch is connected to the load if the voltages are not sufficiently equalized. - Post discharging of loads may also be necessary for safety reasons and other reasons. Post discharging resistors can be used for this process, such as illustrated in
FIGS. 22-25 .FIG. 22 illustrates apost discharge circuit 2200. As illustrated inFIG. 22 , battery 2202 has a voltage V1. Battery 2202 is connected to switch 2208 so that current 2302 is supplied to load 2204.Switch 2210 is open, which isolates thedischarge resistor 2206. -
FIG. 23 is an illustration of thedischarge circuit 2200 during the post discharge mode. As illustrated inFIG. 23 ,switch 2208 is open andswitch 2210 is closed.Discharge resistor 2206 discharges the current 2400 on theload 2204 through dissipation indischarge resistor 2206 whileswitch 2210 is closed. Battery 2202 is disconnected from the circuit byswitch 2208. -
FIG. 24 is agraph 2400 of the current flowing through thedischarge resistor 2206. As shown inFIG. 24 , at t=0 the current has an initial spike whenswitch 2210 is closed and decays to 0 over time proportional to the size of thedischarge resistor 2206 and to the capacity ofload 2204. -
FIG. 25 is a graph of the voltage across theload 2400 versus time. At time t=0, the voltage is equal to V1. The voltage across theload 2204 slowly decays as the current 2400 flows through thedischarge resistor 2206. Again, the charge on the capacitive load is wasted as dissipated heat. -
FIG. 26 is a schematic illustration of an embodiment abattery connection circuit 2600.Battery module 2602 includes abattery 2208 and acontroller 2612.Controller 2612 controls the operation ofswitch 2610 and detects the terminal voltage ofbattery 2608 onnodes second battery 2604 onnodes Battery 2604 is connected tobattery module 2602 byterminals Controller 2612 may also be connected to thebattery 2604 to detect any current flowing from thebattery 2604 to load 2626. Detection of current may occur over a communication link from a module mounted on thebattery 2604 or from a separate circuit (not shown) connected to thebattery 2604. - As shown in
FIG. 26 ,switch 2610 is open. Hence, current 2606 does not flow betweenbattery 2608 andbattery 2604.Controller 2612 generates acontrol signal 2614, which activates theswitch 2610.Controller 2612 activates theswitch 2610 when it is determined that the terminal voltages ofbattery 2608 andbattery 2604 are sufficiently close that an initial rush of current betweenbattery 2608 andbattery 2604 will not damage either of the batteries,terminals switch 2610.Controller 2612 may also detect current flowing frombattery 2604 to aload 2626, as indicated above. If current is flowing from thebattery 2604, the open circuit voltage may be different from the terminal voltage of thebattery 2604 since theload 2626 may draw down the terminal voltage ofbattery 2604, due to the internal series resistance ofbattery 2604. If theswitch 2610 is closed when thebattery 2604 is connected to aload 2626 and a substantial amount of current is flowing between thebattery 2604 and theload 2626, a surge in current may occur betweenbattery 2604 andbattery 2608 if theload 2626 is disconnected or the current betweenbattery 2604 and theload 2626 changes. As such,controller 2612 includes logic that may prevent the generation ofcontrol signal 2614 to close theswitch 2610 if the current from thebattery 2604 to aload 2626 is high. -
FIG. 27 is a graph of the current 2606 versus time. Since theswitch 2610 is in an open condition, the current 2606 is zero until t=0. When t>0, there is no current sincebattery 2608 has the same exact terminal voltage as the terminal voltage ofbattery 2604. -
FIG. 28 is an illustration of thebattery connection circuit 2600 ofFIG. 26 with theswitch 2610 in a closed position. As shown inFIG. 28 , at time t=0switch 2610 closes.Controller 2612 detects the terminal voltage ofbattery 2604 andbattery 2608 to determine if theswitch 2610 can be safely closed without causing a large in-rush of current that may damage the batteries. Having done so, even afterswitch 2610 closes at time t=0, there is no significant current, as shown inFIG. 28 . -
FIG. 29 is a graph showing the voltage atterminals switch 2610 is closed, which applies the voltage (V1) ofbattery 2608 to theterminals battery 2604. Ascontroller 2612 ensured that the voltage ofbattery module 2602 was close to the voltage ofbattery 2604 before closingswitch 2610, the voltage acrossterminals switch 2610 is closed. -
FIGS. 30-33 disclose a chargingbattery equalization circuit 3000 in different states of operation. As illustrated inFIG. 30 , abattery module 3002 is wired for connection tobattery 3012 having a voltage (V2).Battery module 3002 includes abattery 3006 having a voltage (V1). Acharger 3004 is connected tobattery 3006 and is controlled by acontroller 3010.Controller 3010 is connected to the terminals ofbattery 3012 to detect the terminal voltage ofbattery 3012. In addition,controller 3010 is connected to the terminals ofbattery 3006 to detect the terminal voltage ofbattery 3006.Controller 3010 also controls the operation ofswitch 3008. - In
FIG. 31 , thebattery module 3002 is connected tobattery 3012.Controller 3010 detects that the terminal voltage (V2) is greater than the battery voltage (V1) ofbattery 3006.Controller 3010 generates acontrol signal 3014 to activatecharger 3004 to chargebattery 3006.Switch 3008 remains in the open position whilebattery 3006 is being charged. - In
FIG. 32 ,controller 3010 detects that the terminal voltage ofbattery 3006 is charged to same voltage level as the terminal voltage ofbattery 3012. In other words,battery 3006 is charged until V1 equals V2. Controller 3010 then turns off thecharger 3004.Switch 3008 remains in the open position. - In
FIG. 33 ,controller 3010 closes theswitch 3008 after detecting that the voltage (V1) inbattery 3006 is substantially equal to the voltage (V2) inbattery 3012.Charger 3004 remains in the off position. Current 3016 that flows initially between thebattery module 3002 andbattery 3012 is essentially zero. -
FIGS. 34-37 illustrate abattery equalization circuit 3400 in different states of operation. As illustrated inFIGS. 34-37 , acharger 3414 is used to chargebattery 3412, which has a voltage (V2) that is less than the voltage (V1) onbattery 3404. - As illustrated in
FIG. 34 ,battery module 3402 is wired for connection withbattery module 3410.Battery module 3402 includes abattery 3404 that has a terminal voltage (V1).Controller 3408 generates acontrol signal 3416 to controlswitch 3406.Controller 3408 also generates acontrol signal 3418 that controls the operation ofcharger 3414 to chargebattery 3412 inbattery module 3410. - As illustrated in
FIG. 35 ,battery module 3410 is connected tobattery module 3402, but no current is flowing betweenbattery 3404 andbattery 3412 sinceswitch 3406 is in the open position.Controller 3408 detects the terminal voltage ofbattery 3412 atnodes controller 3408 detects the terminal voltage ofbattery 3404 atnodes battery 3412 can also be provided tocontroller 3408 over a communication link from a controller in battery module 3410 (not shown).Controller 3408 detects that thebattery 3412 has a terminal voltage (V2) that is less than the terminal voltage (V1) ofbattery 3404.Controller 3408 then generatescontrol signal 3418 to turn oncharger 3414 to chargebattery 3412. - As illustrated in
FIG. 36 ,controller 3408 detects thatbattery 3412 has been charged to a voltage which is substantially equal to the voltage ofbattery 3404, and generates acontrol signal 3418 to turn off thecharger 3414. In other words,controller 3408 detects that V1 is substantially equal to V2. Switch 3406 ofbattery module 3402 remains in an open position so that no current is flowing betweenbattery module 3402 andbattery module 3410. - As illustrated in
FIG. 37 , the controller generates thecontrol signal 3416 to closeswitch 3406, once thecontroller 3408 has detected that the voltage (V1) ofbattery 3404 is substantially equal to the voltage (V2) ofbattery 3412.Control signal 3418 causes thecharger 3414 to remain in an off condition. A low level current (i) 3420 then may flow between thebattery module 3402 andbattery module 3410 to further equalize the charges betweenbatteries batteries battery 3412 has been charged so that V2 is substantially equal to V1. - Of course, chargers can be placed in both battery modules, which would constitute a combination of the circuits illustrated in
FIGS. 30-33 andFIGS. 34-37 . -
FIGS. 38-41 illustrate a dischargingequalizer circuit 3800. If there is no external source of power to charge the batteries, the battery modules may include a load resistor to dissipate energy and lower the voltage of the battery that is at a higher voltage in order to equalize the voltages between the batteries prior to connection. - As illustrated in
FIG. 38 , the dischargingequalizer circuit 3800 includes abattery module 3802 that is wired for connection with abattery 3804.Battery module 3802 includes abattery 3806 that has a terminal voltage (V1). Dischargingresistor 3842 is wired to be connected in parallel withbattery 3806 upon activation ofswitch 3848.Controller 3808 generates acontrol signal 3844 that activatesswitch 3848 to connect the dischargingresistor 3842 in parallel withbattery 3806.Controller 3808 also generates acontrol signal 3840 to activateswitch 3846.Battery 3804 has a voltage (V2) that is greater than V1 in the example illustrated inFIGS. 38-39 . - As shown in
FIG. 39 ,controller 3808 has determined that thebattery 3806 has a voltage that is greater than the voltage ofbattery 3804 by detecting the terminal voltage ofbattery 3804 onnodes battery 3806 onnodes Switch 3848 is activated by acontrol signal 3844 fromcontroller 3808, which connects the dischargingresistor 3842 in parallel with thebattery 3806. The discharge resistor causes thebattery 3806 to discharge by dissipating energy in the dischargingresistor 3842. - In
FIG. 40 , thecontroller 3808 detects the voltage on thebattery 3806 onnodes battery 3804 onnodes battery 3806 is substantially equal to the charge ofbattery 3804, thecontroller 3808 deactivatescontrol signal 3844 to openswitch 3848, as illustrated inFIG. 40 . - As illustrated in
FIG. 41 , controller closes theswitch 3846 to connectbattery 3806 in parallel withbattery 3804 afterswitch 3848 has been opened, and the voltages onbatteries -
FIGS. 42-45 illustrate a dischargingcircuit 4200, which dischargesbattery module 4204. As illustrated inFIG. 42 ,battery 4206 has a voltage that is lower thanbattery 4216 ofbattery module 4204.Battery module 4202 is wired for connection in parallel with thebattery module 4204.Controller 4208 generates acontrol signal 4214 that operatesswitch 4220.Switch 4220 connectsdischarge resistor 4218 in parallel withbattery 4216 to dischargebattery 4216.Controller 4208 also generates acontrol signal 4212 to activateswitch 4210, which connectsbattery module 4202 in parallel withbattery module 4204 when the voltages onbatteries -
FIG. 43 is another illustration of the dischargingequalization circuit 4200. As shown inFIG. 43 ,battery module 4202 is connected tobattery module 4204. However, current does not flow betweenbattery module 4202 andbattery module 4204 sinceswitch 4210 is in the open position.Controller 4208 detects the terminal voltages ofbattery 4216 onnodes controller 4208 detects the terminal voltages ofbattery 4206 onnodes controller 4208 detects that the voltage onbattery 4216 is greater than the voltage ofbattery 4206,controller 4208 activatescontrol line 4214 to closeswitch 4220.Switch 4220 connects dischargingresistor 4218 in parallel withbattery 4216 to dischargebattery 4216. -
FIG. 44 is a schematic illustration of the dischargingequalization circuit 4200 withswitch 4220 in an open position.Controller 4208 generates acontrol signal 4214 that opensswitch 4220 once the terminal voltage ofbattery 4216 is substantially equal to the terminal voltage ofbattery 4206. - As illustrated in
FIG. 45 ,controller 4208 then activatesswitch 4210 to connectbattery module 4202 in parallel withbattery module 4204. Current 4222 is sufficiently low that damage is not caused tobatteries - Although
FIGS. 38-41 illustrate the discharging of one of the batteries, andFIGS. 42-45 illustrate the discharging of the other battery, these circuits can be combined to allow discharge of either set of batteries by a controller. -
FIG. 46A is a schematic block diagram of an energy exchangebattery equalization circuit 4600. The circuits illustrated inFIGS. 38-45 disclose energy dissipation circuits, which dissipate energy from one of the batteries to equalize the charge on the batteries so that the initial in-rush of current does not damage the batteries. However, dissipation of energy from the batteries is inefficient. The energy exchangebattery equalization circuit 4600 does not require charging, which requires an external energy source, or dissipation of charge, which results in wasted energy. The energy exchangebattery equalization circuit 4600 operates by exchanging charge between the batteries prior to connection of the batteries in parallel so that the terminal voltages of the batteries, when connected in parallel, are substantially equal so that a large amount of current is not created, which may cause damage to the batteries. As illustrated inFIG. 46A ,controller 4608 detects the terminal voltage ofbattery 4606 atnodes controller 4608 detects the terminal voltage ofbattery 4604 atnodes main switch 4616 is open. The DC toDC converter 4610 is disposed in thebattery module 4602. The DC toDC converter 4610 is connected betweenbattery DC switch 4612 in response to acontrol signal 4618. When thecontroller 4608 detects a difference in the terminal voltages ofbatteries controller 4608 generates acontrol signal 4618 that connects the DC toDC converter 4610 tobatteries DC converter 4610 may comprise a bi-directional DC to DC converter that is capable of transferring charge in either direction betweenbatteries DC converter 4610 may comprise a pair of DC to DC converters including a step-up converter and a step-down converter that can be connected in the proper orientation in response to the detected voltages and states of charge of thebatteries controller 4608. The DC toDC converter 4610 transfers charge between thebatteries controller 4608 generates acontrol signal 4616 that closes themain switch 4614 to connectbattery 4606 in parallel withbattery 4604. A substantial in-rush of current does not occur as long as the voltages ofbatteries DC converter 4610. -
FIG. 46B discloses an energy exchange battery/load equalization circuit 4650. The energy exchange battery/load equalization circuit 4650 is similar to the energy exchangebattery equalization circuit 4600, illustrated inFIG. 46A . The difference between the circuits is that the charge on acapacitive load 4652 is equalized with the charge onbattery 4654 prior to connecting the circuits to prevent damage tobattery 4654 and/orload 4652.Load 4652 may include a large capacitive load such as may be present at the input of a motor controller circuit. For example, motor controller circuits are used in electric cars and other electric vehicles to control the application of current to the motors of the vehicles.Controller 4662 can detect the terminal voltages of theload 4652 and thebattery 4654 to determine when the terminal voltages become substantially equal.Controller 4662 activatesswitch 4658 to allow the DC toDC converter 4656 to charge theload 4652 to the voltage of thebattery 4654. Once theload 4652 has a voltage that is substantially the same as the voltage of thebattery 4654, theswitch 4658 is opened bycontroller 4662, and themain switch 4660 is closed. Afterswitch 4660 is opened, the DC toDC converter 4656 can also be used to discharge the charge onload 4652 and apply that charge to thebattery 4654 to further conserve energy. Discharging theload 4652 is also done to remove voltage fromload 4652, for safety purposes. -
FIG. 47 illustrates the manner in which a step-downconverter system 4700 can be used to transfer charge between a first battery 4706 and asecond battery 4708. As illustrated atblock 4702, the voltage Vb1 of battery 4706 is greater than the voltage Vb2 ofbattery 4708. A step-down DC toDC converter 4716 has aninput 4712 that is connected to battery 4706. The output of the step-down DC toDC converter 4716 is connected tobattery 4708. As indicated at block 4704, the state of charge SOC1 of battery 4706 is greater than the state of charge SOC2 ofbattery 4708. In this manner, energy can be transferred from battery 4706 tobattery 4708 in the direction of thearrow 4710. - As illustrated in
FIG. 48 , a step-upconverter 4716 is connected betweenbattery 4806 and battery 4808. As shown inFIG. 48 ,battery 4806 is connected to theinput 4812 of the step-up DC to DC converter, while theoutput 4814 of the step-up DC to DC converter is connected to battery 4808. As indicated byblock 4802,battery 4806 has a terminal voltage Vb1 that is less than the terminal voltage Vb2 of battery 4808. However, the state of charge ofbattery 4806 is greater than the state of charge of battery 4808 as indicated byblock 4804.Battery 4806 is connected to aload 4818 that causes the terminal voltage ofbattery 4806 to be lower than the terminal voltage (Vb2) of battery 4808. In that regard, ifload 4818 were disconnected from thebattery 4806,battery 4806 would have a higher terminal voltage than battery 4808. However, since thebattery 4806 is connected to theload 4818 and has a lower terminal voltage (Vb1) than the terminal voltage (Vb2) of battery 4808, a step-up DC toDC converter 4816 must be utilized so that energy can be transferred from battery 4806 (with a higher state of charge, SOC1) to battery 4808 (with a lower state of charge, SOC2), in the direction shown by thearrow 4810. -
FIG. 49 is a schematic illustration of a step-upconverter system 4900. As illustrated inFIG. 49 , theinput 4912 of the step-up DC toDC converter 4916 is connected to battery 4906. Battery 4906 is also connected to load 4918. Theoutput 4914 of the step-up DC toDC converter 4916 is connected to battery 4906 having a terminal voltage (Vb1) that is greater than the terminal voltage (Vb2) of battery 4908. The state of charge of thebattery 4806 is greater than the state of charge of battery 4906, as indicated atblock 4904, even though the terminal voltage of the battery 4806 (Vb2) is less than the terminal voltage (Vb1) of battery 4906. This is a result of the fact thatbattery 4806 is connected to load 4918, which reduces the terminal voltage Vb2 of battery 4908. Accordingly, step-up DC toDC converter 4916 is used to transfer energy from thebattery 4806, that has a higher state of charge, to battery 4906, which has a lower state of charge, which causes energy to flow in the direction of thearrow 4910. -
FIG. 50 is a schematic illustration of a step-downconverter system 5000. As illustrated inFIG. 50 ,battery 5008, having a terminal voltage Vb2, is connected to the input 5014 of a step-down DC toDC converter 5016.Battery 5006, having a terminal voltage Vb1, is connected to theoutput 5012 of the step-down DC toDC converter 5016. As illustrated in block 5002,battery 5008 has a terminal voltage (Vb2) that is greater than the terminal voltage (Vb1) ofbattery 5006. In addition, the state of charge ofbattery 5008 is greater than the state of charge ofbattery 5006. Accordingly, energy flows in the direction of thearrow 5010. -
FIG. 51 is a schematic illustration of an energy exchangebattery equalization circuit 5100. As illustrated inFIG. 51 , battery 5106 has a voltage (V1) and is disposed in thebattery module 5102.Battery 5104 has a terminal voltage (V2) and is connected to thebattery module 5102. Until the main switch 5110 is closed in response to acontrol signal 5108 fromcontroller 5104, no current flows betweenbatteries 5106, 5104.Controller 5104 detects the terminal voltage of battery 5106 atnodes controller 5104 detects the terminal voltage ofbattery 5104 atnodes batteries 5104, 5106 can also supply this information.Controller 5104 may also receive signals indicating the amount of current flowing frombatteries 5106, 5104 and can calculate the state of charge of thebatteries 5106, 5104. In response to these signals,controller 5104 can generate control signals to operateswitches switches DC converter 5114. In this manner, energy can be transferred between thebatteries 5106, 5104 in accordance with the detected voltages, and states of charge ofbatteries 5106, 5104, in response to control signals fromcontroller 5104. Once the voltages or states of charge are equalized, thecontroller 5104 can activate the main switch 5110 to connect thebatteries 5106, 5104 in parallel. If the battery voltage versus the state of charge is not monotonic, or if the battery resistance is undetermined, thecontroller 5104 can use the state of charge information instead of a calculated open circuit voltage to determine the direction in which the DC to DC converter should transfer energy. The open circuit voltage of a loaded battery can be estimated by the voltage, resistance and current of the battery. As indicated above, after a sufficient amount of energy is transferred by the selected DC to DC converter, the main switch 5110 is closed and the DC to DC converts 5112, 5114 are isolated from the circuit. Thecontroller 5104 monitors a communication link between thebattery module 5102 and thebattery 5104. If thebattery module 5102 becomes disconnected frombattery 5104,controller 5104 opens the main switch 5110 and the system returns to the initial condition for safety reasons. -
FIG. 52 illustrates a bi-directional, non-isolated, Ćuk DC toDC converter 5220 that is capable of transferring charge betweenbatteries Switches capacitor 5238 in parallel across thebatteries capacitor 5238.Conductors capacitor 5238 when theswitches capacitor 5238 are transferred between thebatteries batteries Switches diodes switches switches switches batteries DC converter 5220 is a variation of a Ćuk converter, which uses two active switches rather a single active switch. -
FIGS. 53 and 54 illustrate an inverting DC toDC converter 5300. Initially, switches 5314, 5316 are closed, which connects the inverting DC to DC converter in a reverse polarity direction so that thebatteries Switch 5318 opens and closes at a high frequency, so that energy is stored from battery 5303 ininductor 5306, and then transferred throughdiode 5308 tobattery 5304. Once thebatteries switches FIG. 54 . - Non-isolated DC to DC converters, such as disclosed above, typically use an inductor, which provides a simpler circuit that is less expensive and allows essentially all of the input current to flow to the output. However, non-isolated DC to DC converters do not isolate the input from the output, which results in noise and other interference, that may be present on the input, to be transmitted to the output. Additionally, in simpler topology non-isolated DC to DC converters, the output voltage is constrained by the input voltage as explained in more detail below.
- On the other hand, isolated DC to DC converters isolate noise between the input and output or a first port and a second port, and the output voltage is not constrained by the polarity or level of the input voltage. However, isolated DC to DC converters employ a transformer, which is expensive and less efficient than simply using an inductor, such as employed in a non-isolated DC to DC converter.
- Classic, non-isolated DC to DC converters are three-terminal devices. The output voltage of a non-isolated DC to DC converter can be either higher than the input voltage, in which case a step-up converter is used, or lower than the input voltage, in which case a step-down converter may be used, or may be the opposite polarity of the input voltage, in which case an inverting non-isolated DC to DC converter would be used.
-
FIGS. 55-66 disclose various implementations of non-isolated DC to DC converters. For example,FIG. 55 discloses a three-terminal, non-isolated step-up DC toDC converter system 5500. As illustrated inFIG. 55 ,battery 5502 has a voltage (Vb) and is connected to input 5506 of the step-up DC toDC converter 5510.Load 5504 has a voltage (V1) and is connected to theoutput 5508 of the step-up DC toDC converter 5510. The voltage (Vb) ofbattery 5502 is less than the voltage (V1) across theload 5504. As such, a step-up DC toDC converter 5510 is used to transfer energy from thebattery 5502 to theload 5504. -
FIG. 56 discloses a three-terminal non-isolated step-down DC toDC converter system 5600. As illustrated inFIG. 56 ,battery 5602 has a voltage (V2) and is connected to theinput 5606 of the step-down DC toDC converter 5610.Load 5604 is connected to theoutput 5608 of the step-down DC toDC converter 5610. The voltage (V1) acrossload 5604 is less than the voltage (Vb) acrossbattery 5602. Accordingly, a step-down converter 5610 is used to transfer energy from thebattery 5602 to theload 5604. -
FIG. 57 discloses an inverting DC toDC converter system 5700. As illustrated inFIG. 57 ,battery 5702 is connected to theinput 5706 of the inverting DC toDC converter 5710.Load 5704 is connected to theoutput 5708 of the inverting DC toDC converter 5710. Since the inverting DC toDC converter 5710 inverts the voltage, theload 5704 is connected in opposite polarity to thebattery 5702. -
FIG. 58 illustrates an isolated four-terminal DC toDC converter system 5800. As illustrated inFIG. 58 ,battery 5802 has a voltage (Vb1) and is connected to theinput 5806 of the isolated DC toDC converter 5810.Load 5804 has a voltage (V1) across its terminals and is connected to anoutput 5808 of the isolated DC toDC converter 5810. The isolated DC toDC converter 5810 can be operated such that Vb can be less than V1, Vb can be equal to V1 and Vb can be greater than V1. In addition, the polarities of the input and output voltages can be inverted. -
FIG. 59 is a schematic illustration of a flying inductor DC toDC converter system 5900. As shown inFIG. 59 ,battery 5902 has a voltage (Vb) and is connected to theinput 5908 of the flying inductor DC toDC converter 5912. Load 5904 has a voltage V1 across its terminals and is connected to theoutput 5910 of the flying inductor DC toDC converter 5912. In a manner similar to the isolated DC to DC converter, Vb can be greater than V1, Vb can be less than V1, Vb can be equal to V1 and the polarity of V1 can be inverted with respect to Vb. - The flying inductor DC to DC converters share many of the advantages of the isolated DC to DC converters as well as many of the advantages of the non-isolated DC to DC converters. Just like the isolated DC to DC converters, the flying inductor DC to DC converter essentially isolates noise from being transmitted between the input and the output of the flying inductor DC to DC converter. Additionally, the flying inductor DC to DC converter provides a degree of electrical isolation between its input and output. Finally, the output voltage level and polarity of the flying inductor DC to DC converter is not constrained by the input voltage level and polarity of the input voltage.
- In a manner similar to the non-isolated DC to DC converters, the flying inductor topology does not require the use of an expensive and bulky transformer and has the ability to transfer essentially all of the input current to the output. Accordingly, the flying inductor DC to DC converter has advantages of both the isolated and non-isolated converters and can be effectively used as a DC to DC converter and in systems for equalizing charges on batteries or between batteries and capacitive loads.
- Further, the flying inductor DC to DC converter system can be reduced to a three-terminal system from a four-terminal system by connecting one of the input terminals to one of the output terminals. In that regard, the negative input terminals can be connected together, the positive terminals can be connected together, a negative input terminal can be connected to a positive output terminal, or a positive input terminal can be connected to a negative output terminal.
FIGS. 60-63 illustrate these various typologies. -
FIG. 60 is a schematic illustration of the flying inductor DC toDC converter system 6000 that has the negative input terminals connected together. As illustrated inFIG. 60 ,battery 6002 has a voltage Vb.Battery 6002 is connected through theinput 6006 that includes a positive terminal andnegative terminal 6010.Battery 6002 supplies a voltage Vb to the flying inductor DC toDC converter 6000.Load 6004 is connected tooutput 6008, which has a positive terminal and anegative terminal 6012.Conductor 6014 connects thenegative terminals battery 6002 and the negative terminal of theload 6004 are also connected to the negative terminals of the flying inductor. The voltage acrossload 6004 is equal to V1. The topology illustrated inFIG. 60 allows the voltage Vb to be less than, greater than, or equal to the voltage V1. In other words, the flying inductor DC toDC converter 6016 can operate as a step-up or step-down converter. In that regard, it is similar to a non-isolated Ćuk converter, but simpler in operation. -
FIG. 61 is a schematic illustration of the flying inductor DC toDC converter system 6100 that has the positive terminals connected together. As illustrated inFIG. 61 ,battery 6102 is connected to theinput 6106 of the flying inductor DC toDC converter 6100.Battery 6102 supplies a voltage Vb to the flying inductor DC toDC converter 6100.Load 6104 is connected to theoutput 6108 of the flying inductor DC toDC converter 6100.Load 6104 has a voltage V1 across its terminals.Conductor 6110 connects the positive terminals of the input to the positive terminal of the output of the flying inductor DC toDC converter 6100. Accordingly, the flying inductor DC toDC converter 6100 is a three-terminal device similar to the three-terminal device illustrated inFIG. 60 , but with input and out voltages that are negative with respect tocommon conductor 6110. Accordingly, the flying inductor DC toDC converter 6112 can operate as a step-up converter or a step-down converter and is also similar to the non-isolated Ćuk converter. -
FIG. 62 is a schematic illustration of a flying inductor DC toDC converter system 6200 that has the negative input terminals connected to the positive output terminal. As illustrated inFIG. 62 , battery Vb is connected to theinput 6206 of the flying inductor DC toDC converter 6200.Battery 6202 supplies a voltage Vb to the flying inductor DC toDC converter 6200. Load 6204 is connected to theoutput 6208 of the flying inductor DC toDC converter 6210. The negative terminal of theinput 6206 is connected to the positive terminal of theoutput 6208 byconductor 6203, to render this as a three-terminal device. By connecting these terminals together, thesystem 6200 becomes an inverting converter, such as disclosed herein. -
FIG. 63 is a schematic illustration of a flying inductor DC toDC converter 6300 that has the positive input terminals connected to the negative output terminal. As illustrated inFIG. 63 ,battery 6302 is connected to theinput 6310 of the flying inductor DC toDC converter 6314.Battery 6302 supplies a voltage Vb to the flying inductor DC toDC converter 6300. Load 6304 is connected to theoutput 6312 of the flying inductor DC toDC converter 6300. Load 6304 has a voltage Vb plus V1 across its terminals sinceconductor 6308 connects the positive terminal of thebattery 6302 to the negative terminal of the load 6304. By connecting the positive terminal of the input to the negative terminal of the output causes the system illustrated inFIG. 63 to simply be an inverting converter, as is the one inFIG. 62 , though the polarity is opposite. -
FIG. 64 illustrates a unidirectional DC toDC converter 6400. As illustrated inFIG. 64 , energy flows in the direction from the input to the output as illustrated byarrow 6412.Battery 6402 applies a voltage to the input of the unidirectional DC toDC converter 6400 that is equal to Vb. Theload 6404 is connected to theoutput 6408 of the unidirectional DC toDC converter 6410. The negative terminals of thebattery 6402, theload 6404 and the unidirectional DC toDC converter 6410 are connected together. The unidirectional DC toDC converter 6410 can only transfer energy from theinput 6406 to theoutput 6408 in the direction of thearrow 6412. -
FIG. 65 is a schematic illustration of a bi-directional DC toDC converter system 6500. As illustrated inFIG. 65 , battery 6502 is connected to the first port of the bi-directional DC toDC converter 6510 and applies a voltage (Vb) to thefirst port 6506.Battery 6504 is connected to a second port 6508 of the bi-directional DC toDC converter 6510 and applies a voltage Vb2 to the second port 6508. The bi-directional DC toDC converter 6510 is capable of transferring energy in either direction between battery 6502 andbattery 6504 as illustrated byarrow 6512. Bi-directional DC to DC converters may operate to transfer energy in either direction. Bi-directional DC to DC converters use active switches in place of rectifier diodes. - The flying inductor DC to DC converter may also be designed to operate bi-directionally. However, the flying inductor topology suffers from several limitations. First, the flying inductor topology is inherently less efficient than a simple, non-isolated DC to DC converter because the current path includes two switches rather than one switch in the non-isolated DC to DC converter. Further, the flying inductor DC to DC converter does not offer true galvanic isolation. For example, the maximum voltage difference between any input terminal and any output terminal is determined by the relative value of the input and output voltages, as long as the breakdown voltages of the components used in the flying inductor DC to DC converter are sufficiently high.
-
FIG. 66 illustrates a bi-directional flying inductor DC toDC converter system 6600. As illustrated inFIG. 66 , afirst voltage source 6606 has a voltage V1 that is connected to theinput 6602 of the bi-directional flying inductor DC toDC converter 6610.Voltage source 6608 has a voltage (V2) and is connected to theoutput 6604 of the bi-directional flying inductor DC toDC converter 6610. The voltage constraints of the bi-directional flying inductor DC toDC converter 6610 are that the output voltage V2 minus input voltage V1 can only range between minus V2 and plus V1. -
FIG. 67A is a schematic diagram of an embodiment of a bi-directional flying inductor DC toDC converter system 6700, which is unable to include a dead time. As illustrated inFIG. 67 , the flying inductor DC toDC converter 6700 transfers charge in either direction betweenbattery 6702 andbattery 6704.Switches buffers Switches non-inverting buffers pulse waveform generator 6706 is low, switches 6716, 6718 are closed andswitches pulse waveform generator 6706 goes low, switches 6716, 6718 are open and switches 6720, 6722 are closed. This is defined as Phase B. As such, when switches 6716, 6718 are open, switches 6720, 6722 are closed, and vice versa. The opening and closing of the switches is substantially simultaneous, as a result of the topology of the circuit of the flying inductor DC toDC converter 6700.Inductor 6724 is therefore alternately connected betweenbattery 6702, andbattery 6704. Current in theinductor 6724 increases, decreases, and changes direction, depending upon the pulse width of thepulse waveform generator 6706. In this fashion, the direction and amount of energy transferred betweenbatteries waveform generator 6706. Each of theswitches -
FIG. 67B is a schematic diagram of another embodiment of a bi-directional flying inductor DC toDC converter system 6720, which is able to include a dead time. As illustrated inFIG. 67B , the flying inductor DC toDC converter 6720 transfers charge in either direction betweenbattery 6702 andbattery 6704.Switches buffers 6728, 6730, respectively. When thewaveform 6740 frompulse waveform generator 6736 is high, switches 6716, 6718 are closed. When thewaveform 6740 frompulse waveform generator 6736 is low, switches 6716, 6718 are open.Switches buffers waveform 6741 frompulse waveform generator 6736 is high, switches 6720, 6722 are closed. When thewaveform 6741 is low, switches 6720, 6722 are open. As such, switches 6716, 67518 close and open together. Similarly, switches 6720, 6722 alternately close and open together. Whenwaveforms switches Inductor 6724 is therefore alternately connected betweenbattery 6702, andbattery 6704 or not connected to eitherbattery 6702 orbattery 6704. Current in theinductor 6724 increases, decreases, and changes direction, depending upon the timing of thepulse waveforms generator 6736. In this fashion,waveform generator 6736 can control the direction and amount of energy transferred betweenbatteries -
FIGS. 68-70 illustrate the three operating phases of the bi-directional flying inductor DC to DC converter ofFIG. 67B .FIG. 68 illustrates the phase-A 6800 operating mode of the flying inductor DC to DC converter. In phase-A, switches 6806, 6808 are in a closed position and switches 6810, 6812 are in an open position. During phase-A, the voltage source V1 is applied acrossinductor 6814, with the polarity illustrated inFIG. 68 .Voltage source V 2 6804 is isolated from the inductor. -
FIG. 69 illustrates the operation of the flying inductor DC to DC converter in phase-B 6900. As illustrated inFIG. 69 ,switches switches inductor 6814 with the polarity illustrated inFIG. 69 .Voltage source V 1 6802 is isolated frominductor 6814. -
FIG. 70 is a schematic illustration of the flying inductor DC to DC converter in adead time phase 7000. As illustrated inFIG. 70 ,switches Inductor 6814 is isolated from bothvoltage sources 6082, 6804. - The switches illustrated in
FIGS. 68-70 may be implemented as active switches, such as transistors, such as MOSFETs, IGBTs, BJTs, or thyristors, such as SCRs, GTOs, TRIACs. In some cases, isolation of the voltage sources is not complete because of the structure of these switches, such as MOSFETs and IBGTs, as explained in more detail below. -
FIG. 71 is a schematic diagram of a uni-directional flying inductor DC toDC converter system 7100. As illustrated inFIG. 71 , avoltage source 7102 supplies a voltage (V1) to the uni-directional flying inductor DC toDC converter 7100. The uni-directional flying inductor DC toDC converter 7100 has twoactive switches rectifier diodes Switch 7106 is operated bynon-inverting buffer 7110.Switch 7108 is operated by invertingbuffer 7112.Waveform generator 7118 generates a variable duty cycle square wave waveform that operatesbuffers waveform generator 7118 goes low, during phase A, switches 7106, 7108 are closed. Whenwaveform generator 7118 goes high, during phase B, switches 7106, 7108 are open.Switches voltage source 7102 through theinductor 7120 in a direction from left to right, as illustrated inFIG. 71 . When switches 7106, 7108 are open,diodes inductor 7120 from left to right throughload 7104. The current decays linearly over time when the current is applied to theresistive load 7104. If the energy ininductor 7120 is depleted, current ceases to flow, during the dead time. In this manner, energy is transferred from thevoltage source 7102 to theload 7104 in the uni-directional flying inductor DC toDC converter 7100, illustrated inFIG. 71 . -
FIG. 72 is a graph of inductor current versus time of the uni-directional flying inductor DC to DC converter illustrated inFIG. 71 that is operating in a discontinuous mode. As illustrated inFIG. 72 , in the first time period, designated as phase-A 7202, the inductor current increases in a direction from left to right (positive direction), as illustrated inFIG. 71 , because the voltage V1 is supplied acrossinductor 7120. When switches 7106, 7108 are opened at the end of the time period phase-A 7202,diodes inductor 7120 through theload 7104. The inductor current decays to zero through the time period phase-B 7104, until the current reaches zero. Duringdead time 7206, the output ofwaveform generator 7118 remains low, so switches 7106, 7108 remain open. At the end of the period ofdead time 7106,waveform generator 7118 generates a pulse so thatswitches -
FIG. 73 is a graph of inductor voltage versus time for the uni-directional DC to DC converter, which is operating in the discontinuous mode, such as illustrated inFIG. 72 . As illustrated inFIG. 73 , during phase-A 7302, the voltage acrossinductor 7120 is equal to V1. The voltage (V1) ofvoltage source 7102 is applied across theinductor 7120, as a result ofswitches B 7304, the voltage acrossinductor 7120 is equal to the negative of voltage ofload 7104, −VL, sinceswitches load 7104 is applied across theinductor 7120 in a direction opposite (negative polarity) to the voltage applied by thevoltage source 7102. During the period of thedead time 7306, zero voltage is applied across theinductor 7120. The process then begins again with phase-A 7308. -
FIG. 74 is a schematic illustration of the phase-A operation 7400 of the uni-directional flying inductor DC to DC converter. As illustrated inFIG. 74 ,switches diodes Waveform generator 7422 is high, which causesbuffers switches switch 7404,inductor 7408 andswitch 7410. Asdiodes load 7418 is substantially isolated from thevoltage source 7402. -
FIG. 75A is a schematic illustration of the phase-B operation 7500 of the uni-directional flying inductor DC to DC converter. Theoutput 7422 ofwaveform generator 7422 is low, which, throughbuffers switches voltage 7402 of voltage source is isolated frominductor 7408. Simultaneously, the current 7520 ininductor 7408, which was generated during phase-A operation and which cannot be interrupted, creates a voltage acrossinductor 7408 of the opposite polarity from phase A ofFIG. 74 , until its amplitude is sufficiently high to forward-bias rectifier diodes inductor 7408 is connected to load 7418, and current 7520 flows intoload 7418. The current flowing throughload 7418, in the manner illustrated inFIG. 75 , decays due to dissipation from theresistive load 7418. Phase B ends when the current 7520 ininductor 7408 has decreased to 0, at which point the entire energy in theinductor 7408 has been transferred to load 7418. - The
switches FIG. 75 are assumed to open essentially simultaneously at the transition between phase-A and phase-B. However, there can be a short period between the end of phase-A and the beginning of phase-B during which only one ofswitches -
FIGS. 75B, 75C illustrate the current flow into an external circuit that results from the loss of isolation due to mismatch in the opening and closing times ofswitches switch 7404 were to open first, the current 7420 ofFIG. 74 would be interrupted, but the current 7520 would start immediately, because the current throughinductor 7408 cannot be interrupted. This would connect theinductor 7408 to load 7418 through forwardbiased diode rectifiers FIG. 75A . However,switch 7410 would is still closed, connecting the negative terminal ofvoltage source 7402 to the positive terminal ofload 7418. Similarly, ifswitch 7410 were to open first, the current 7420 ofFIG. 74 would be interrupted, but the current 7520 would start immediately, because the current throughinductor 7408 cannot be interrupted. This would connect theinductor 7408 to load 7418 through forwardbiased diode rectifiers FIG. 75A . However,switch 7404 would is still closed, connecting the positive terminal ofvoltage source 7402 to the negative terminal ofload 7418. Either one of these conditions result in a temporary loss of isolation betweenvoltage source 7402 andload 7418. - As illustrated in
FIG. 75B , an impulse of current 7532 flows in the clockwise direction through anexternal circuit 7536 during the time that switch 7404, is closed andswitch 7410 is open. - Conversely, as illustrated in
FIG. 75C , animpulse 7534 of current flows in the counter-clockwise direction through theexternal circuit 7536 during the time that switch 7410, is closed andswitch 7404 is open. The current of these pulses can be limited through the use of low pass filter 7530. If these current impulses are symmetrical, there is no net DC flow in the external circuit. However, an asymmetrical mismatch between the opening and closing times ofswitches switches -
FIG. 76 is a schematic illustration of thedead time operation 7600 of a uni-directional flying inductor DC to DC converter. As illustrated inFIG. 76 ,switches buffers waveform generator 7422 being in a low condition. After the current ininductor 7408 decays to zero, no current is flowing throughinductor 7408. Thevoltage source 7402 is therefore substantially isolated from theload 7418 during the dead time. -
FIG. 77 is agraph 7700 of inductor current of the uni-directional flying inductor DC toDC converter 7100 that is operating in critical mode. As illustrated inFIG. 77 , during phase-A 7702, inductor current gradually builds, since the voltage V1 is applied across theinductor 7408. During phase-B 7704, theswitches FIG. 75 ), through theinductor 7408, decays as a result of dissipation and theresistive load 7418. As soon as the current 7424 decays to zero, switches 7404, 7410 are closed, as a result of thewaveform generator 7422 going high, and another phase-A 7706 is initiated and the current again starts to build in theinductor 7408. -
FIG. 78 is agraph 7800 of inductor voltage of a uni-directional flying inductor DC toDC converter 7100 operating in critical mode. As illustrated inFIG. 78 , thevoltage waveform 7808 has a voltage equal to V1 during phase-A 7802. During phase-B 7804, thevoltage waveform 7808 has a voltage equal to the negative of the load voltage, −VL. The voltage waveform then returns to the voltage V1 duringphase C 7806. Phase-B is timed so that the inductor current decreases to 0 when the next phase is initiated. -
FIG. 79 is a graph 7900 of inductor current of a uni-directional flying inductor DC toDC converter 7100 in continuous mode. The continuous mode of operation is similar to the critical mode, except that the next phase is initiated before the current 7424 decays to zero so that there is still current in theinductor 7408. The new phase is started and more current is added to theinductor 7408, which is an addition to the current that is already flowing in the inductor. The continuous mode of operation is considered continuous because there is always current flowing in theinductor 7408. The amount of energy transferred is regulated by adjusting the pulse width modulation of the control signal, which is the ratio of the duty cycle of phase-A versus the sum of phase-A plus phase-B. The higher the average inductor current , the higher the amount of energy transferred. Referring again toFIG. 79 , during phase-A 7902 inductor current increases to I2, as illustrated byplot 7908. Phase-B 7904 is such that the current decreases to I1 as shown bycurrent plot 7908. Although Phase-B is shown as shorter, Phase-B could be longer, depending upon the ratio of the input and output voltage. Phase-A 7906 then begins again before the inductor current 7908 decreases to zero. -
FIG. 80 is a plot 8000 of conductor voltage of a uni-directional flying inductor DC toDC converter 7100 versus time that is operating in a continuous mode. As illustrated inFIG. 80 , during phase-A 8002, the inductor voltage is at voltage level V1. During phase-B 8004 the inductor voltage is the negative of the load voltage, V. -
FIG. 81A is an illustration of anotherembodiment 8100 of a uni-directional flying inductor DC-DC converter, using a biased inductor. The current ininductor 7408 inFIG. 74 flows in only one direction, therefore using only one half of the available magnetization ofinductor 7408. Use of a magnetically biasedinductor 8102 allows use of the full range of the available magnetization ofinductor 8102, and therefore allows the use of a physically smaller inductor for a given amount of power transferred. -
FIG. 81B is an illustration of the uni-directional flying inductor DC toDC converter 8100 illustrating an analysis of the isolation limits of the uni-directional flying inductor DC toDC converter 8100 with the load pulled as far negative as possible.Node 8114, on the negative terminal ofvoltage source 8102, is the reference, by definition at 0 Volt.Node 8116, on the positive terminal ofload 8104, can be pulled in the negative direction untilrectifier diode 8108 and the intrinsic diode inswitch 8112 are forward biased. At that point, the voltage drop acrossrectifier diode 8108 is approximately 1 V, as is the voltage drop across the intrinsic diode inswitch 8112. Therefore, the voltage of terminal 8116 is unable to go any more negative than 2 V below thereference node 8114. The voltage onnode 8118, on the negative terminal ofload 8104, is lower than the voltage onnode 8116, on the positive terminal ofload 8104, by an amount equal to the voltage across theload 8104. Therefore, the voltage onnode 8118 is unable to go any more negative than the load voltage, VL, plus 2 V. In other words, the negative end ofload 8104 is clamped to −VL−2 V. The voltage onnode 8118 will not be clamped if thecomponents node 8118 is not allowed to go below −VL, the negative of the voltage of theload 8104. -
FIG. 82 is the illustration of the uni-directional, flying inductor DC toDC converter 8100 illustrating an analysis of the isolation limits of a uni-directional flying inductor DC toDC converter 8100 with the load pulled as far positive as possible.Node 8116, on the negative terminal ofvoltage source 8102, is the reference, by definition at 0 Volt.Node 8118, on the negative terminal ofload 8104, can be pulled in the positive direction untilrectifier diode 8106 and the intrinsic diode inswitch 8110 are forward biased. At that point, the voltage drop acrossrectifier diode 8106 is approximately 1 V, as is the voltage drop across the intrinsic diode inswitch 8110. Therefore, the voltage of terminal 8118 is unable to go any more positive than 2 V above the voltage ofnode 8122 on the positive terminal ofvoltage source 8102. The voltage onnode 8122 is higher than the voltage onreference node 8114, on the negative terminal ofvoltage source 8102, by V1. Therefore, the voltage onnode 8118 is unable to go any more positive than the voltage source voltage, V1, plus 2 V. In other words, the negative end ofload 8104 is clamped to V1−2 V. The voltage onnode 8118 will not be clamped if thecomponents node 8118 is not allowed to go above V1, the voltage of thevoltage source 8102. - The analysis of
FIGS. 81A, 81B and 82 show that thevoltage source 8102, and theload 8104, are essentially isolated from each other as long as the voltage onnode 8118 remains within the range −VL and V1, where VL is the voltage of theload 8104, and V1 is the voltage of the voltage source 8012. Outside of that range, the uni-directional, flying inductor DC-DC converter is not isolated. -
FIG. 83 is a schematic illustration of anotherembodiment 8300 of the uni-directional DC-DC converter that has a higher isolation voltage range than the circuit ofFIGS. 81A, 81B and 82 . Theactive switches FIG. 81A, 81B and 82 are replaced by bidirectionalactive switches bidirectional switches bidirectional switches switches FIG. 82 , and the rectifier diode in the direction that is the opposite of the intrinsic diode across the transistor. The use of bidirectional switches removes the limitation of the circuit inFIG. 82 , because there is no longer a series of diodes that can be forward biased when the load is pulled negatively or positively. -
FIG. 84A is the illustration of a uni-directional, flying inductor, DC toDC converter 8400 that provides an analysis of the isolation limits of the uni-directional flying inductor DC toDC converter 8400, as the load is pulled in the positive direction.Rectifier diodes Bidirectional switches Node 8306, on the negative terminal of thevoltage source 8308 is defined as a reference. The voltage onnode 8306 is, by definition, 0 V. The voltage onnode 8316, on the negative terminal of theload 8316, is pulled up to positive 1 kV above thereference node 8306.Rectifier diode 8312 is forward biased, allowing the positive 1 KV voltage to be applied toinductor 8318. The intrinsic diode in the bottom component inbidirectional switch 8302 is also forward biased, allowing the positive 1 KV voltage to be applied to the mid-point voltage insideswitch 8302. However, the top component inbidirectional switch 8302 is oriented in the opposite direction, and is therefore reverse biased. As the breakdown voltage ofbidirectional switch 8302 is 1.2 kV, it can withstand that reverse voltage, preventing the positive 1 KV voltage to be applied tonode 8307, on the positive terminal ofvoltage source 8308. Therefore, in the unidirectional, flying inductor DC-DC converter, thevoltage source 8308 is isolated from theload 8310 as long as the voltage on theload 8310 is no more positive than 1 kV. -
FIG. 84B is an illustration of the uni-directional, flying inductor, DC toDC converter 8400 that provides an analysis of the isolation limits of a uni-directional flying inductor DC toDC converter 8400, as the load is pulled in the negative direction.Node 8306, on the negative terminal of thevoltage source 8308 is defined as a reference, at 0 V by definition. The voltage onnode 8316, on the negative terminal of theload 8316, is pulled down to negative 1 kV below thereference node 8306.Rectifier diode 8314 is forward biased, allowing the negative 1 kV voltage to be applied toinductor 8318. The intrinsic diode in the top component inbidirectional switch 8304 is also forward biased, allowing the negative 1 kV voltage to be applied to the mid-point voltage insideswitch 8304. However, the bottom component inbidirectional switch 8304 is oriented in the opposite direction, and is therefore reverse biased. As the breakdown voltage ofbidirectional switch 8304 is 1.2 kV, it can withstand that reverse voltage, preventing the negative 1 kV voltage to be applied tonode 8306. Therefore, in the unidirectional, flying inductor DC-DC converter, thevoltage source 8308 is isolated from theload 8310 as long as the voltage on theload 8310 is no more negative than 1 kV. - The analysis of
FIGS. 84A and 84B shows that thevoltage source 8102, and theload 8104, are essentially isolated from each other as long as the voltage onnode 8316 remains within the range −Vbreakdown and +Vbreakdown, where Vbreakdown is the breakdown voltage of thecomponents -
FIG. 85 is a schematic illustration of a bi-directional DC toDC converter 8500 for transferring charges between voltage sources. As illustrated inFIG. 85 , twovoltage sources DC converter 8500.Waveform generator 8506 generates a waveform onoutput 8508 and waveform onoutput 8510. At any given time,waveform 8508 can be low, orwaveform 8510 can be low, of both can be low. At no time can waveform 8508 and 0810 be both high. These waveforms are typically variable duty cycle, square wave waveforms.Buffers output 8508 andclose switches output 8508 ofwaveform generator 8506.Buffers output 8510 andclose switches output 8510. As such, switches 8520, 8526 are closed only during a first phase, phase-A and are opened otherwise.Switches switches inductor 8528 in accordance with the timing of the voltage that is alternatively applied toinductor 8528, resulting in flow of power from eithervoltage source 8502 tovoltage source 8504, or in the reverse direction. -
FIG. 86 is a schematic illustration of a bi-directional flying inductor DC toDC converter 8600 for transferring a charge from avoltage source 8602 to aload 8604. As illustrated inFIG. 86 , the bi-directional DC toDC converter 8600 operates in the same manner as the bi-directional DC toDC converter 8500, illustrated inFIG. 85 , with the exception that the pulse width of the waveform that is applied by the waveform generator 8606 controls the amount of energy that is transferred from thevoltage source 8602 to theload 8604. - The topology of the circuits illustrated in
FIGS. 85 and 86 differs from theuni-directional topology 7100 that is disclosed inFIG. 71 , in that the two rectifier diodes are replaced by active switches, making the topology of the bi-directional DC toDC converter 8600 fully symmetrical. The bi-directional DC toDC converter 8600, illustrated inFIG. 86 , has better efficiency than the uni-directional DC toDC converter 7600, illustrated inFIG. 76 , since the active switches in the bi-directional DC toDC converter 8600 can be designed to have a lower voltage drop than the forward voltage drop ofrectifier diodes - The bi-directional DC to DC converter, such as illustrated in
FIGS. 85 and 86 , can operate in the discontinuous mode, critical mode and continuous mode, and in either two or three phases, such as phase-A, phase-B or an optional dead time phase. In the bi-directional DC to DC converter, either phase-A or phase-B can occur first depending upon the direction in which power is to be transferred. For example, if phase-A occurs first, energy is transferred from a first power source to a second power source, or if phase-B occurs first, energy is transferred from a second power source to a first power source, as disclosed in more detail below. - With respect to
FIGS. 87-102 , current flowing through an inductor, such asinductor inductor inductor inductor -
FIGS. 87-90 disclose the manner in which energy is transferred from afirst voltage source 8702 to asecond voltage source 8728 by first initiating the operation of the bi-directional inductor DC to DC converter in phase-A. -
FIG. 87 illustrates phase-A operation 8700 of the bidirectional floating inductor DC-DC converter transferring energy in the forward direction. Thewaveform generator 8704 generates thefirst output 8706 in a high condition. As such,buffer 8710 closes switch 8718 andbuffer 8716 closesswitch 8720. In this manner, the current 8730 flows fromvoltage source 8702 throughswitch 8718, throughinductor 8726 throughswitch 8720 and returns to thevoltage generator 8702, transferring energy fromvoltage source 8702 toinductor 8726. Thewaveform generator 8704 generatessignal 8708 in a low condition. As such,buffers open switches inductor 8726 from thesecond voltage source 8728. -
FIG. 88 illustrates the phase-B operation 8800 of the bi-directional flying inductor DC to DC converter, that is illustrated inFIG. 87 , transferring energy in the forward direction. As shown inFIG. 88 , thewaveform generator 8704 generates a low signal onoutput 8706. As such,buffers open switches inductor 8726 from thefirst voltage source 8702. Thewaveform generator 8704 generates a high signal onoutput 8708. As such,buffer 8712 closes switch 8722 andbuffer 8714 closesswitch 8724. The voltage V2 fromvoltage source 8728 is asserted acrossinductor 8726 in the manner illustrated inFIG. 88 . In other words, the voltage (V1) that is asserted across theinductor 8726 in phase-A (in a positive direction), as illustrated inFIG. 87 , is the opposite of the voltage (V2) that is asserted across theinductor 8726 during phase-B (in a negative direction), as illustrated inFIG. 88 . In this manner, the current ininductor 8726 is discharged ontosecond voltage source 8728, transferring the energy stored ininductor 8726 ontosecond voltage source 8728. As such, the flying inductor DC-DC converter succeeded in transferring energy in the forward directions, from thefirst voltage source 8702 to thesecond voltage source 8728. -
FIG. 89 illustrates aplot 8900 of current through the inductor for critical mode operation of the bi-directional DC to DC converter transferring energy in the forward direction illustrated inFIGS. 87-88 . As illustrated inFIG. 89 , the inductor current increases linearly from 0 during phase-A 8902, as illustrated by the highlightedpath 8730 ofFIG. 87 , as a result of the voltage V1 applied across theinductor 8726 in a positive direction. During phase-B 8904, the current decreases linearly to zero because of the voltage V2 that is asserted across theinductor 8726 in an opposite direction from V1, as illustrated inFIG. 87 , which decreases the flow of current from left to right ininductor 8726.FIG. 89 shows the inductor current inplot 8908, which is reduced to zero at the end of phase-B 8904. At the end of phase-B 8904, the voltage of the waveform 8910 (FIG. 90 ) transitions to a positive voltage, which causes the inductor current 8908 to increase again during phase-A 8906. -
FIG. 90 is aplot 9000 of the voltage across theinductor 8726 for critical mode operation of the bi-directional DC toDC converter 8700 transferring energy in the forward direction. As illustrated inFIG. 90 , thevoltage 8910 is initiated at a level V1 during phase-A 8902. During phase-B 8904, thevoltage waveform 8910 transitions to a minus V2. Phase-A 8906 is then initiated again, so that thevoltage waveform 8910 transitions to a voltage of V1. Thevoltage waveform 8910 is timed so that the inductor current 8908 reaches a maximum during phase-A. During phase-B 8904, thevoltage waveform 8910 has a pulse width so that the current 8908 decays to zero volts, so that critical mode operation is established. -
FIGS. 91 and 92 are illustrations of a bi-directional flying inductor DC toDC converter 9100 that transfers energy in the reverse direction. - As illustrated in
FIG. 91 , the processes initiated in phase-B by thewaveform generator 9116, which initially generates a low condition oncontrol line 9112, and a high condition oncontrol line 9114. The high condition incontrol line 9114 causesbuffers switches inductor 9106 with a negative polarity.Buffers switches 9124, 9126 to be open. Consequently, current flows from second voltage source 910 toinductor 9106, transferring energy from second voltage source 910 toinductor 9106. Current 9102 flows ininductor 9106 from right to left, in the opposite direction from the direction illustrated inFIG. 87 . The low condition incontrol line 9112 causesbuffers switches inductor 9106 fromfirst voltage source 9120. -
FIG. 92 illustrates phase-A operation 9200 of the flying inductor DC to DC converter that transfers energy in the reverse direction. As shown inFIG. 92 , thewaveform generator 9116 generates a low condition oncontrol line 9114. As such,buffers open switches inductor 9106 fromsecond voltage source 9110. Thewaveform generator 9116 generates a high condition oncontrol line 9112. As such,buffers close switches inductor 9106 in a positive direction, which is the opposite of the direction in which V2 was applied toinductor 9106 during phase B ofFIG. 91 . Consequently, current 9118 flows from theinductor 9106 tofirst voltage source 9120, transferring the energy stored in theinductor 9106 tofirst voltage source 9120. As such, the flying inductor DC-DC converter succeeded in transferring energy in the reverse directions, from thesecond voltage source 9110 tofirst voltage source 9120. -
FIGS. 93 is aplot 9300 of the current through theinductor 9106 for critical mode operation of the bi-directional DC to DC converter transferring power in the reverse direction, illustrated inFIGS. 91-92 . As illustrated inFIG. 93 , during phase-B 9302 the inductor current, as shown byplot 9308, starts from 0, then linearly increases in the negative direction since the current is flowing from right to left through theinductor 9106, as illustrated inFIG. 91 . At the end of phase-B 9302, as illustrated inFIG. 94 , the voltage V1 fromvoltage generator 9120 is applied across theinductor 9106 in a positive direction during phase-A 9404 that is opposite to the voltage V2 that is applied toinductor 9106 during phase-B 9402. This causes the current to decrease linearly during phase-A to zero current. As shown inFIG. 94 , at the end of phase-A 9404, thevoltage waveform 9308 transitions to a negative pulse, which initiates phase-B 9406. Since the initiation of phase-B 9406 is at the same time that the current 9308 reaches zero, this is considered to be the critical mode of operation of the bi-directional DC to DC converter. -
FIG. 95 is aplot 9500 of inductor current versus time for discontinuous mode of operation transferring power in the forward direction. Compared to critical mode, discontinuous mode adds a dead time, which allows fixing the period of a complete cycle, and therefore to set the overall switching frequency. As illustrated inFIG. 95 , during phase-A 9502, the current builds from zero to h. Phase-B 9504 has a period that depends on the ratio of V1 over V2. The inductor current 9510 decreases to zero during phase-B. Duringdead time 9506, the current 9510 is not flowing through theinductor 9106. Phase-A 9508 then starts and the current 9510 starts increasing for the period of phase-A 9508. -
FIG. 96 is a plot 9600 of the voltage across theinductor 9106 versus time for a discontinuous mode of operation transferring energy in the forward direction. As illustrated inFIG. 96 , thevoltage waveform 9512 is at a voltage level equal to V1 during phase-A 9502. During phase-B 9504, thevoltage 9512 transitions to minus V2. At the end of phase-B 9504, the voltage transitions to zero duringdead time 9506. Phase-A then begins again at 9508 where the voltage transitions to voltage V1. -
FIG. 97 is agraph 9700 of the inductor current versus time for a discontinuous mode of operation while transferring energy in the reverse direction. As illustrated inFIG. 97 , the current 9710 starts at 0 and increases in the negative direction during phase-B 9702, which occurs first. Phase-A 9704 is then initiated and the voltage V1 is applied across the inductor, which causes the magnitude of the current 9710 to decrease until the current reaches zero. Duringdead time 9706, no current is flowing in the inductor since all the switches are off. Phase-B 9708 is then initiated and the current 9710 begins to increase negatively. -
FIG. 98 is a plot 9800 ofinductor voltage 9710 versus time for a discontinuous mode of operation while transferring energy in the reverse direction. As illustrated inFIG. 98 , thevoltage waveform 9712 across theinductor 9106 is initiated at phase-B 9702 with a voltage of minus V2 since the voltage source of V2 is applied across the inductor, such asinductor 9106 inFIG. 91 , as a negative voltage. Phase-A 9704 is then initiated and thevoltage 9712 transitions to a positive voltage V1 since the voltage across theinductor 9106, as illustrated inFIG. 92 , is applied in a positive direction. At the end of phase-A 9704, there is adead time 9706 in which no voltage is applied across theinductor 9106. At the end of thedead time 9706, phase-B 9708 is initiated as a negative pulse. -
FIG. 99 is a plot 9900 of inductor current 9808 versus time for a continuous mode of operation while transferring energy in the forward direction. Compared to critical mode, in continuous mode the inductor current never decays to 0. This allows the total period of a cycle to be constant, and therefore the switching frequency to be fixed. As illustrated inFIG. 99 , the inductor current 9908 starts at zero and increases during phase-A 9902. During phase-B 9904, a voltage equal to minus V2 is applied across the inductor in a negative direction, which causes the current 9908 to linearly decrease to a level i1. Phase-A 9906 is initiated prior to the time that the current 9908 reaches zero, which causes the DC toDC converter 8500 to operate in a continuous mode. -
FIG. 100 is a plot of the voltage of the inductor for a continuous mode of operation while transferring energy in the forward direction. During phase-A 10002, a positive voltage V1 is applied across the inductor. During phase-B 10004, a negative voltage minus V2 is applied across the inductor as illustrated byvoltage waveform 10008. Phase-B 1004 is a period that is less than it would be for critical mode ofFIG. 90 so that the current 9908 does not reach zero at the end of phase-B 10004. Phase-A 10006 is initiated prior to the current 9908 reaching zero so that the flying inductor DC to DC converter is operating in a continuous mode. -
FIG. 101 is a plot 10100 of inductor current 10108 versus time for a continuous mode of operation while transferring energy in the reverse direction. As illustrated inFIG. 101 , during phase-B 10102 the current 10108 starts at 0 and increases linearly in the negative direction. At the end of phase-B, phase-A 10104 is initiated, which causes the negative current to steadily decrease. Prior to the time that the current 10108 reaches zero, phase-B 10106 is initiated so that the flying bridge DC toDC converter 8500 is operating in a continuous mode. -
FIG. 102 is a plot 10200 ofinductor voltage 10208 versus time for a continuous mode of operation while transferring energy in the reverse direction. As illustrated inFIG. 102 , the process initiated in phase-B 10202 with a negative voltage minus V2 that is applied to the inductor. Phase-A 10204 is then initiated, which causes thevoltage waveform 10208 to transition to a voltage of positive V1. Phase-B 10206 is then initiated at the end of phase-A 10204. As illustrated inFIG. 102 , the pulse width of phase-A 10204 is less than the pulse width of phase-B 9406 ofFIG. 94 for critical mode so that the current 10108 does not reach zero prior to the time that phase-B 10106 is initiated. -
FIG. 103 is an analysis of the schematic diagram of a bi-directional, flying inductor DC to DC converter 10300 using bi-directional switches. As shown inFIG. 103 ,voltage source 10302 has a voltage V1. Voltage source 10304 has a voltage V2. The circuit illustrated inFIG. 103 operates in the same manner as described above with regard to the flyinginductor converter 8500. However, each switch is replaced with a bi-directional switch such asbi-directional switches FIGS. 85-86 , the circuit is limited to a certain differential voltage. For example, the differential voltage between negative terminal of the first power source, such aspower source 8502 illustrated inFIG. 85 , and the negative terminal of thesecond power source 8504, may only vary between minus V1 and plus V2, where V1 is the voltage of thefirst power source 8502 and V2 is the voltage of thesecond power source 8504. However, the bi-directional switches 10306-10312 eliminate these restrictions as there is no intrinsic diode across the active switch that can be forward biased. However, the input/output voltage differential is limited by the breakdown voltage of the component used. For example, as illustrated inFIG. 103 , switches 10306-10312 have a breakdown voltage of 1.2 kilovolts. As such, the circuit illustrated inFIG. 103 would be able to operate within input to output differential voltage of plus or minus 1 kilovolt -
FIGS. 104, 105 , illustrate other embodiments of the bi-directional, flying inductor DC-DC converter, reduced from a 4 terminal device to three terminal devices, by connecting one an input terminal to an output terminal. Such embodiments no longer provide isolation between the input and the output. Since in the 4-terminal embodiment of the lying inductor DC-DC converter the input and output are isolated, connecting one an input terminal to an output terminal is possible without affecting the operation of the flying inductor DC-DC converter. -
FIG. 104 illustrates another embodiment of the four-terminal, bi-directional flying inductor DC toDC converter system 10400, reduced to a three-terminal device with negative input and output. As shown inFIG. 104 , the positive terminal ofbatteries conductor 10410. Similarly, the positive terminal ofbattery 10404 is connected toconductor 10408. Since the switches are alternately opened and closed,conductors node 10410 without changing the operation of the circuit. -
FIG. 105 is another embodiment of the four-terminal, bi-directional flying inductor DC toDC converter 10500, reduced to a three-terminal device with positive input and output. As shown inFIG. 105 , the flying inductor DC toDC converter 10500 includesbatteries conductor 10510. Since theswitches conductor 10506, 10508 can be connected atnode 10510 without changing the operation of the flying inductor DC toDC converter 10500. - The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.
Claims (26)
1. A charging system for safely connecting a first battery in parallel with a second battery comprising:
a controller in communication with a first battery to detect a first terminal voltage, the controller in communication with a second battery to detect a second terminal voltage;
a first charger connected to the first battery, the first charger activated by the controller;
a second charger connected to the second battery, the second charger activated by the controller;
a switch operable to connect the first battery and the second battery in parallel, the switch activated by the controller;
wherein in a first instance the controller activating the first charger to charge the first battery to a first voltage when the first terminal voltage is less than the second terminal voltage, and in a second instance the controller activating the second charger to charge the second battery to a second voltage when the second terminal voltage is less than the first terminal voltage, the controller activating the switch when the first voltage and the second voltage are sufficiently close to permit parallel connection of the first battery to the second battery without a damaging current flowing there between.
2. The charging system of claim 1 , wherein the controller activates the switch when the first voltage and the second voltage are equal.
3. The charging system of claim 1 , wherein an initial current between the parallel connected first battery and the second battery is essentially zero.
4. The charging system of claim 1 , wherein the first charger and the second charger are both activated by the controller to charge the first battery and the second battery to about an equal third voltage.
5. The charging system of claim 1 , wherein the controller generates a first control signal to activate the first charger, generates a second control signal to activate the second charger, and a third control signal to activate the switch to connect the first battery and the second battery in parallel.
6. The charging system of claim 1 , wherein the controller indirectly directs the activation of at least one of, the first charger, the second charger, and/or the switch.
7. The charging system of claim 1 , wherein the second charger is the first charger.
8. The charging system of claim 1 , wherein the first charger and second charger are disconnected upon equalization.
9. A charging system for safely connecting a first battery in parallel with a second battery comprising:
a controller that detects a first terminal voltage of terminals of a first battery, and a second terminal voltage of terminals of a second battery;
a first charge adjuster activated by the controller to either charge or discharge the first battery to a first voltage when the first terminal voltage is different from the second terminal voltage, the charging or discharging equalizing the voltage;
a second charge adjuster activated by the controller to either charge or discharge the second battery to a second voltage when the second terminal voltage is different from the first terminal voltage, the charging or discharging equalizing the voltage;
a switch activated by the controller when the first voltage and the second voltage are sufficiently close to permit parallel connection of the first battery to the second battery without a damaging current flowing there between.
10. The charging system of claim 9 , wherein the first charge adjuster is selected from the group consisting of: a first charger, a first load, a first discharging resistor.
11. The charging system of claim 9 , wherein the second charge adjuster is selected from the group consisting of: a second charger, a second load, a second discharging resistor.
12. The charging system of claim 9 , wherein the controller activates the switch when the first voltage and the second voltage are essentially equal.
13. The charging system of claim 9 , wherein the controller indirectly directs the activation of at least one of, the first charge adjuster, the second charge adjuster, and/or the switch.
14. The charging system of claim 9 , wherein an initial current between the parallel connected first battery and the second battery is essentially zero.
15. The charging system of claim 9 , wherein the first charge adjuster and the second charge adjuster are both activated by the controller to change the first battery and the second battery to about an equal third voltage.
16. The charging system of claim 9 , wherein the controller generates a first control signal to activate the first charger, generates a second control signal to activate the second charger, and a third control signal to activate the switch to connect the first battery and the second battery in parallel.
17. The charging system of claim 9 , wherein the second charger is the first charger.
18. The charging system of claim 9 , wherein the first adjuster and second adjuster are disconnected upon equalization.
19. A method of charging for safely connecting a first battery in parallel with a second battery comprising:
providing a controller in communication with a first battery to detect a first terminal voltage, the controller in communication with a second battery to detect a second terminal voltage;
providing a first charger connected to the first battery, the first charger activated by the controller:
providing a second charger connected to the second battery, the second charger activated by the controller;
providing a switch operable to connect the first battery and the second battery in parallel, the switch activated by the controller;
detecting the first terminal voltage and the second terminal voltage, wherein in a first instance the controller activating the first charger to charge the first battery to a first voltage when the first terminal voltage is less than the second terminal voltage, and in a second instance the controller activating the second charger to charge the second battery to a second voltage when the second terminal voltage is less than the first terminal voltage, the controller activating the switch when the first voltage and the second voltage are sufficiently close to permit parallel connection of the first battery to the second battery without a damaging current flowing there between.
20. The method of claim 19 , wherein the controller activates the switch when the first voltage and the second voltage are essentially equal.
21. The method of claim 19 , wherein an initial current between the parallel connected first battery and the second battery is essentially zero.
22. The method of claim 19 , wherein the first charger and the second charger are both activated by the controller to charge the first battery and the second battery to about an equal third voltage.
23. The method of claim 19 , wherein the controller generates a first control signal to activate the first charger, generates a second control signal to activate the second charger, and a third control signal to activate the switch to connect the first battery and the second battery in parallel.
24. The method of claim 19 , wherein the second charger is the first charger.
25. The method of claim 19 , wherein the controller indirectly directs the activation of at least one of, the first charger, the second charger, and/or the switch.
26. The method of claim 19 , wherein the first charger and second charger are disconnected upon equalization.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US15/608,890 US20170271863A1 (en) | 2012-07-09 | 2017-05-30 | System and method for connecting a first battery in parallel with a second battery by charging for equalization |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US13/544,100 US9711962B2 (en) | 2012-07-09 | 2012-07-09 | System and method for isolated DC to DC converter |
US15/608,890 US20170271863A1 (en) | 2012-07-09 | 2017-05-30 | System and method for connecting a first battery in parallel with a second battery by charging for equalization |
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US15/608,890 Abandoned US20170271863A1 (en) | 2012-07-09 | 2017-05-30 | System and method for connecting a first battery in parallel with a second battery by charging for equalization |
US15/608,898 Abandoned US20170271864A1 (en) | 2012-07-09 | 2017-05-30 | System and method for connecting a first battery in parallel with a second battery by discharging for equalization |
US15/608,908 Abandoned US20170271865A1 (en) | 2012-07-09 | 2017-05-30 | System and method for connecting a first battery in parallel with a second battery by exchanging energy for equalization |
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US15/608,908 Abandoned US20170271865A1 (en) | 2012-07-09 | 2017-05-30 | System and method for connecting a first battery in parallel with a second battery by exchanging energy for equalization |
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Also Published As
Publication number | Publication date |
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US20170271864A1 (en) | 2017-09-21 |
US20170271865A1 (en) | 2017-09-21 |
US9711962B2 (en) | 2017-07-18 |
US20140009106A1 (en) | 2014-01-09 |
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