JP4415730B2 - Voltage converter - Google Patents

Description

  The present invention relates to a voltage conversion device suitably used for, for example, an in-vehicle application, and more particularly to a voltage conversion device configured to operate a plurality of voltage conversion circuits that convert an input voltage into different output voltages in parallel.

  An electric vehicle and a hybrid vehicle using a combination of an engine and a motor as a power source are known. These automobiles are usually often configured as a two-battery type vehicle including a high-voltage battery connected to a motor and a low-voltage battery disposed on the low-voltage side via a transformer. For example, in the case of a hybrid vehicle, the high-voltage battery is driven by a motor to assist the engine during vehicle acceleration, while being recharged by the motor (functioning as a generator) during vehicle deceleration. ing. On the other hand, the low-voltage battery is used as a power source for vehicle auxiliary equipment (various instruments, drive circuits, control circuits, etc.).

  In the two battery type vehicle as described above, power is supplied from the high voltage battery to the low voltage battery using a DC-DC converter. In this DC-DC converter, a DC input voltage is converted into a pulse voltage by a switching circuit composed of a switching element, and then the pulse voltage is stepped down by a transformer. It has a function of converting to a DC voltage.

  This type of DC-DC converter can also be applied to a fuel cell vehicle. Since this fuel cell vehicle requires a large amount of electric power, it is conceivable to provide a plurality of DC-DC converters and operate them in parallel. In the case of a fuel cell vehicle, in the so-called 10.15 mode, the DC-DC converter often operates at a low load factor (ratio of output power to maximum output power) of about 20 to 30%. For this reason, when the parallel operation of the DC-DC converter is always performed, the efficiency of the conversion circuit portion in each DC-DC converter decreases and the loss increases during the light load operation as described above. As a result, the fuel consumption is reduced and the cruising distance is shortened.

Therefore, for example, in Patent Document 1, the present applicant provides two chargers, a master and a slave, and connects the output terminals of the chargers in common, and operates both the master and the slave in a high output power region. In the low output power region, a battery charging device is proposed in which the slave is stopped and only the master is operated. According to this device, high-efficiency operation is possible even at light loads.
JP 2000-299136 A

  In the battery charging apparatus described above, since the master always operates over the entire output power region, even if the slave fails, there is no problem because the master only needs to operate independently. On the other hand, since the slave does not operate alone, in the unlikely event that the master fails for some reason, there is a possibility that even the slave that should be able to operate normally will stop, It is irrational. That is, in the conventional parallel operation type battery charging device, it is difficult to ensure an appropriate operation state when the master fails, and there is room for improvement.

  This invention is made | formed in view of this problem, The objective is to provide the voltage converter which can always ensure an appropriate driving | running state.

  The voltage conversion device of the present invention includes an input terminal and an output terminal, a main conversion circuit that is connected between the input terminal and the output terminal, converts a voltage input from the input terminal into a different voltage, and the input terminal and the output terminal. Is connected in parallel with the main conversion circuit, and converts the voltage input to the input terminal into a different voltage, and the sum of the output current of the main conversion circuit and the sub conversion circuit exceeds the reference current In the case where both the main conversion circuit and the sub conversion circuit are operated, when the sum of the output currents is equal to or lower than the reference current, the first control circuit that performs stop control on the sub conversion circuit and the output voltage at the output terminal are detected. Output voltage detection circuit, overcurrent detection means for detecting whether or not the main conversion circuit is in the output overcurrent droop state, and the main conversion circuit fails based on the detection results of the output voltage detection circuit and the overcurrent detection means State To determine Luke, when it is determined that the failure, and a second control circuit to disable the stop control for the sub converter according to the first control circuit.

  In the voltage conversion device of the present invention, both the main conversion circuit and the sub-conversion circuit are in a state where the sum of the output currents of the main conversion circuit and the sub-conversion circuit (that is, the total output current) exceeds the reference current (high output region). When the sum of output currents is less than or equal to the reference current (low output region), the sub-conversion circuit stops operating and only the main conversion circuit operates. On the other hand, the state of the output voltage is checked and whether or not the output overcurrent is drooping is checked. Based on these results, it is determined whether or not the main conversion circuit is truly in a fault state. If it is determined that there is a failure, the sub-conversion circuit is inhibited from being stopped regardless of the sum of the output currents, and the sub-conversion circuit becomes operable.

  Here, the “output overcurrent drooping state” refers to a state in which the output voltage suddenly decreases and the output current reaches a peak when the load exceeds the maximum output current. This output overcurrent drooping state is different from the device failure state, and when the load is reduced, it returns to the normal output voltage again, which is a normal state of the device.

  In the voltage converter of the present invention, the second control circuit is configured such that the output voltage detected by the output voltage detection circuit is lower than the reference voltage, and the output overcurrent drooping state of the main conversion circuit is detected by the overcurrent detection means. If not detected, it can be configured to determine that the main converter circuit is in a fault condition. The overcurrent detection means is connected to a current detection transformer having a primary side winding connected to the input terminal and a secondary side winding magnetically coupled to the primary side winding, and to a secondary side winding of the detection transformer. The current-voltage conversion circuit and a comparator provided on the output side of the current-voltage conversion circuit can be included. The main converter circuit preferably has a main auxiliary power supply that operates as a power supply for driving the main converter circuit using the voltage input from the input terminal. The sub-conversion circuit preferably has a sub-auxiliary power source that operates as a power source for the first and second control circuits and the output voltage detection circuit using the voltage input from the input terminal. This sub-auxiliary power supply ensures the operation of the first and second control circuits and the output voltage detection circuit even if the main conversion circuit stops operating at all.

  According to the voltage conversion device of the present invention, both the main conversion circuit and the sub-conversion circuit are operated in the high output region, and the sub-conversion circuit stops the operation and operates only the main conversion circuit in the low output region. On the other hand, when the state of the output voltage is examined and whether or not the output overcurrent is in a drooping state is determined, and it is determined that the main conversion circuit is in a failure state based on these results, the sub-regardless of the output region, Since the stop operation of the conversion circuit is suppressed, the sub conversion circuit can be operated even when a failure of the main conversion circuit occurs.

  Hereinafter, the best mode for carrying out the present invention (hereinafter simply referred to as an embodiment) will be described in detail with reference to the drawings.

  FIG. 1 shows a configuration of a voltage converter according to an embodiment of the present invention. The voltage converter according to the present embodiment converts a DC input voltage Vin output from the high voltage battery 10 into a lower output DC voltage Vout and supplies it to the low voltage battery 11. For example, it is suitable for being mounted on a vehicle such as a fuel cell vehicle.

  This voltage converter includes a main conversion circuit 1 and a sub conversion circuit 2 connected in parallel between input terminals T1 and T2 and output terminals T3 and T4, and a first control circuit 3 connected to the sub conversion circuit 2. And a second control circuit 4, and an output voltage detection circuit 5 and an overcurrent detection circuit 6 connected to the second control circuit 4. The input terminals T1 and T2 are connected to the high voltage battery 10, and the output terminals T3 and T4 are connected to the low voltage battery 11 to which the load 13 is connected.

  The main conversion circuit 1 functions as a master, and as such functions as a DC-DC converter that converts the input DC voltage Vin input from the input terminals T1 and T2 into a different voltage (output voltage Vout). ing. The sub-conversion circuit 2 functions as a slave, and itself functions as a DC-DC converter that performs voltage conversion similar to that of the main conversion circuit 1. The main conversion circuit 1 always operates from the high output power region to the low output power region regardless of the power consumption of the load 13. On the other hand, the sub-conversion circuit 2 operates only in the high output power region. Such circuit selection control is performed by the first control circuit 3 as described later. Hereinafter, the main conversion circuit 1 and the sub conversion circuit 2 will be described in detail.

  First, the main conversion circuit 1 will be described.

  The main conversion circuit 1 includes a switching circuit 101 provided between the primary high voltage line H1 and the primary low voltage line L1, the primary winding CA1, and the secondary winding CB1, which is magnetically coupled thereto. And a transformer 102 having CC1. An input DC voltage Vin output from the high voltage battery 10 is applied between the input terminal T1 of the primary high voltage line H1 and the input terminal T2 of the primary low voltage line L1. The main conversion circuit 1 also includes a rectifier circuit 103 provided on the secondary side of the transformer 102 and a smoothing circuit 104 connected to the rectifier circuit 103. The main conversion circuit 1 further includes a switching control circuit 106, a current detection transformer 107 provided in the primary side low-voltage line L1, a current-voltage conversion circuit 108 connected to the current detection transformer 107, and a primary high-voltage line. And a main auxiliary power source 109 provided in H1.

  The switching circuit 101 is a single-phase switching circuit that converts an input DC voltage Vin from the high-voltage battery 10 into a substantially rectangular wave pulse voltage. The switching circuit 101 is a switching circuit formed by full-bridge connection of four switching elements S11, S12, S13, and S14 driven by switching signals SG11 to SG14 supplied from the switching control circuit 106, respectively. As the switching elements S11, S12, S13, and S14, for example, a MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor), an IGBT (Insulated Gate Bipolar Transistor), or the like is used. The switching control circuit 106 operates by receiving a current supply from the main auxiliary power source 109.

  The switching element S11 is provided between one end of the primary side winding CA1 of the transformer 102 and the primary side high voltage line H1, and the switching element S12 includes the other end of the primary side winding CA1 and the primary side low voltage line L1. It is provided between. The switching element S13 is provided between the other end of the primary winding CA1 and the primary high-voltage line H1, and the switching element S14 is connected between the one end of the primary winding CA1 and the primary low-voltage line L1. It is provided in between.

  In the switching circuit 101, when the switching elements S11 and S12 are turned on, the first voltage reaches the primary low voltage line L1 through the switching element S11, the primary winding CA1 and the switching element S12 in order from the primary high voltage line H1. While the current flows through one current path, the switching elements S13 and S14 are turned on, so that the primary low-voltage line passes through the switching element S13, the primary winding CA1 and the switching element S14 sequentially from the primary high-voltage line H1. A current flows through the second current path reaching L1.

  A pair of secondary windings CB1 and CC1 of the transformer 102 are connected to each other by a center tap C, and the center tap C is led to an output terminal T4 via a ground line LG1. That is, this DC-DC converter is a center tap type. The transformer 102 steps down the pulse voltage converted by the switching circuit 101, and outputs a pulse voltage having a phase difference of 180 degrees from each end of the pair of secondary windings CB1 and CC1. The degree of step-down in this case is determined by the turn ratio between the primary winding CA1 and the secondary windings CB1 and CC1.

  The rectifier circuit 103 is a single-phase full-wave rectifier circuit including a pair of diodes D11 and D12. The anode of the diode D11 is connected to one end of the secondary winding CB1 of the transformer 102, and the anode of the diode D12 is connected to one end of the secondary winding CC1. The cathodes of the diodes D11 and D12 are connected in common to the output line LO1. That is, this rectifier circuit 103 has a cathode common connection structure, and rectifies each half-wave period of the AC output voltage of the transformer 102 individually by the diodes D11 and D12 to obtain a rectified voltage. . An output voltage Va (that is, an output DC voltage Vout) is input to the output voltage detection circuit 5 from the output terminal T3.

  The smoothing circuit 104 includes a choke coil 104L inserted and disposed in the output line LO1, and a smoothing capacitor 104C connected between the output line LO1 (specifically, one end of the choke coil 104L) and the ground line LG1. It consists of An output terminal T4 is provided at the end of the ground line LG1. In the smoothing circuit 104 having such a configuration, the DC voltage rectified by the rectifying circuit 103 is smoothed to generate an output DC voltage Vout, which is supplied to the low voltage battery 11 from the output terminals T3 and T4. Yes.

  The current detection transformer 107 has a primary side winding CD1 inserted and connected to the primary side low voltage line L1, and a secondary side winding CE1 whose one end is grounded and magnetically coupled to the primary side winding CD1. . The current detection transformer 107 detects the current I1 corresponding to the current flowing through the primary side low-voltage line L1 by the secondary winding CE1.

  The current-voltage conversion circuit 108 includes a rectifier diode 108D having an anode connected to one end (opposite the ground side) of the secondary winding CE1 of the current detection transformer 107, and the other end (ground) of the secondary winding CE1. Side) and the cathode of the rectifier diode 108D, the resistor 108R and the capacitor 108C are connected in parallel. The current-voltage conversion circuit 108 rectifies the current I1 detected by the current detection transformer 107 by half-wave rectification by the rectifier diode 108D and then holds the peak by the capacitor 108C, and outputs the DC current detection voltage Vs1 obtained thereby. It has become.

  The main auxiliary power supply 109 is a power supply circuit that converts the input DC voltage Vin input to the input terminals T1 and T2 to generate the DC voltage Vcc1, and is configured by a flyback converter circuit, for example. Although this flyback converter circuit is not suitable for obtaining high output power, it is small and has a relatively simple circuit configuration, and is suitable as a drive power source for low power consumption circuits such as control circuits. The DC voltage Vcc1 generated by the main auxiliary power supply 109 is used as an operation power supply for the switching control circuit 106.

  Next, the sub conversion circuit 2 will be described. In FIG. 1, the constituent elements of the sub-conversion circuit 2 are denoted by reference numerals obtained by adding “100” or “10” to the reference numerals of the corresponding constituent elements in the main conversion circuit 1, and description thereof will be omitted as appropriate.

  The circuit configuration of the sub-conversion circuit 2 is the same as that of the main conversion circuit 1, and the switching circuit 201 provided between the primary high-voltage line H2 and the primary low-voltage line L2, the primary winding CA2, and A transformer 202 having secondary windings CB2 and CC2 magnetically coupled thereto, a rectifier circuit 203 provided on the secondary side of the transformer 202, and a smoothing circuit 204 connected to the rectifier circuit 203 are provided. Yes. The sub-conversion circuit 2 further includes a switching control circuit 206, a current detection transformer 207 provided on the primary low-voltage line L2, a current-voltage conversion circuit 208 connected to the current detection transformer 207, and a primary high-voltage line. And a sub-auxiliary power source 209 provided in H2.

  The switching circuit 201, the transformer 202, the rectifier circuit 203, the smoothing circuit 204, the switching control circuit 206, the current detection transformer 207, the current-voltage conversion circuit 208, and the auxiliary auxiliary power supply 209 are respectively the switching circuit 101 and the transformer in the main conversion circuit 1. 102, rectifier circuit 103, smoothing circuit 104, switching control circuit 106, current detection transformer 107, current-voltage conversion circuit 108, and main auxiliary power supply 109 have the same configuration and function. For example, the current-voltage conversion circuit 208 rectifies the current I2 detected by the current detection transformer 207 by half-wave rectification by the rectifier diode 208D, peaks by the capacitor 208C, and outputs the DC current detection voltage Vs2 obtained thereby. It is like that. The auxiliary auxiliary power supply 209 converts the input DC voltage Vin input to the input terminals T1 and T2 to generate the DC voltage Vcc2. This DC voltage Vcc2 is used not only as an operation power supply for the switching control circuit 206 but also as a power supply for the first control circuit 3, the second control circuit 4, and the output voltage detection circuit 5. .

  Next, the first control circuit 3, the second control circuit 4, the output voltage detection circuit 5, and the overcurrent detection circuit 6 will be described in detail.

  The first control circuit 3 includes an inverting logic comparator 31, a resistor 32, and resistors 30R1 and 30R2. A reference voltage Ref <b> 1 is input to the plus side input terminal of the inverting logic comparator 31. The current detection voltage Vs1 output from the current-voltage conversion circuit 108 of the main conversion circuit 1 is input to the negative side input terminal of the inverting logic comparator 31 via the resistor 30R1, and the current voltage of the sub-conversion circuit 2 is also input. The current detection voltage Vs2 output from the conversion circuit 208 is input via the resistor 30R2. That is, a voltage obtained by dividing the sum of the current detection voltage Vs1 and the current detection voltage Vs2 in accordance with the resistance ratio of the resistors 30R1 and 30R2 is input to the negative side input terminal of the inverting logic comparator 31. ing. The inverting logic comparator 31 is for comparing this divided voltage with the reference voltage Ref1. The output terminal of the inverting logic comparator 31 is pulled up to the DC voltage Vcc2 by the auxiliary auxiliary power supply 209 via the resistor 32. Eventually, the first control circuit 3 determines that the main conversion circuit 1 is in a state where the total output current of the voltage conversion device (the sum I of the output currents of the main conversion circuit 1 and the sub conversion circuit 2) exceeds a certain reference current I0. Both the sub-conversion circuit 2 and the sub-conversion circuit 2 are operated, while the sub-conversion circuit 2 is controlled to stop when the sum I of the output currents is less than or equal to the reference current I0. The reference current I0 is a boundary value for dividing the total output region of the voltage converter into a low output region and a high output region, and is set to 50 amperes, for example. As the reference voltage Ref1, a value corresponding to the reference current I0 is set.

  The second control circuit 4 includes a comparator 40, resistors 42 and 43, an NPN transistor 44, a diode 45, and a resistor 46. The reference voltage Ref2 is input to the negative input terminal of the comparator 40, and the positive input terminal is connected to the output terminal of the output voltage detection circuit 5 and the output terminal of the overcurrent detection circuit 6 via the resistor 46. Yes. The output terminal of the comparator 40 is connected through a resistor 43 to the base of an NPN transistor 44 whose emitter is grounded and to the anode of a diode 45. The cathode of the diode 45 is connected to the positive side input terminal of the comparator 40, and plays the role of latching the output of the comparator 40 in cooperation with the resistor 46. The output terminal of the comparator 40 is also pulled up to the DC voltage Vcc2 by the auxiliary auxiliary power supply 209 via the resistor 42. The resistor 46 has a sufficiently large resistance value (a resistance value such that the divided voltage of the DC voltage Vcc2 by the resistors 42 and 46 is larger than the reference voltage Ref2) compared to the resistor 42. A collector of the NPN transistor 44 is connected to a control input terminal (not shown) in the switching control circuit 206 of the sub-conversion circuit 2 together with the output terminal of the first control circuit 3. The second control circuit 4 determines whether or not the main conversion circuit 1 is in a failure state based on the outputs (detection results) of the output voltage detection circuit 5 and the overcurrent detection circuit 6, and determines that there is a failure. Sometimes, the first control circuit 3 has a function of invalidating the stop control for the sub-conversion circuit 2. The detailed operation will be described later.

  The output voltage detection circuit 5 has an output terminal connected to the inverting logic comparator 51 connected to the plus side input terminal of the comparator 40 in the second control circuit 4, and one end connected to the minus side input terminal of the inverting logic comparator 51. The other end of the resistor 52 is connected to the output terminal T3 of the main conversion circuit 1, and the resistor 53 is connected between the negative input end of the inverting logic comparator 51 and the ground line. A reference voltage Ref3 is applied to the positive input terminal of the inverting logic comparator 51. The output terminal of the inverting logic comparator 51 is pulled up to the DC voltage Vcc2 by the auxiliary auxiliary power supply 209 via the resistor 54. The output voltage detection circuit 5 having such a configuration monitors the output voltage Va (= output DC voltage Vout) of the main conversion circuit 1 and detects whether or not the output voltage Va is equal to or higher than the reference voltage Ref3. It has become.

  The overcurrent detection circuit 6 includes an inverting logic comparator 61 whose output terminal is connected to the plus side input terminal of the comparator 40 in the second control circuit 4, and an output terminal to the minus side input terminal of the inverting logic comparator 61. And a connected comparator 62. The reference voltage Ref4 is input to the plus side input terminal of the inverting logic comparator 61. The output terminal of the inverting logic comparator 61 is pulled up to the DC voltage Vcc2 via the resistor 54 described above. The current detection voltage Vs1 is input from the current-voltage conversion circuit 108 of the main conversion circuit 1 to the positive input terminal of the comparator 62, and the reference voltage Ref5 is input to the negative input terminal. The output terminal of the comparator 62 is pulled up to the DC voltage Vcc1 by the main auxiliary power supply 109 via the resistor 63. The overcurrent detection circuit 6 functions as a specific example of the “overcurrent detection means” in the present invention in cooperation with the current detection transformer 107 and the current-voltage conversion circuit 108 of the main conversion circuit 1. The overcurrent detection circuit 6 having such a configuration monitors the current detection voltage Vs1 of the main conversion circuit 1 to determine whether the main conversion circuit 1 is in an output overcurrent drooping state (hereinafter simply referred to as an overcurrent state). Whether or not is detected. Hereinafter, this overcurrent state will be briefly described.

  FIG. 3 schematically shows output voltage versus output current characteristics (hereinafter referred to as VI output characteristics) of the main conversion circuit 1. In this figure, the horizontal axis represents the output current I, and the vertical axis represents the output voltage V. As shown in this figure, the main conversion circuit 1 is configured to output a substantially constant voltage Vr regardless of the magnitude of the output current (that is, the magnitude of the load). Therefore, a maximum output current Imax is provided. When the load exceeds the maximum output current Imax, the output voltage is suddenly decreased to shift to the overcurrent state, so that the output current does not increase any further. Therefore, in this overcurrent state, the output voltage Vex with respect to the output current Iex becomes remarkably small. However, this does not mean that the device is in a failure state, but when the load is reduced, the output voltage Vex returns to the normal output voltage again. Yes, the device is in a normal state.

  Next, the operation of the voltage converter having the above configuration will be described. First, the basic operation (voltage conversion operation) will be described.

  The switching circuit 101 switches the input DC voltage Vin supplied from the input terminals T1 and T2 to generate a pulse voltage, and supplies this to the primary winding CA1 of the transformer 102. From the secondary windings CB1 and CC1 of the transformer 102, a pulse voltage that has been transformed (here, stepped down) is taken out.

  The rectifier circuit 103 performs full-wave rectification on the pulse voltage by the diodes D11 and D12. As a result, a rectified output is generated between the center tap C (ground line LG1) and the connection point (output line LO1) of the diodes D11 and D12.

  The smoothing circuit 104 smoothes the rectified output generated between the ground line LG1 and the output line LO1, and outputs it as an output DC voltage Vout from the output terminals T3 and T4. This output DC voltage Vout is fed to the low-voltage battery 11 and used for charging.

  Next, with reference to FIG. 2, a characteristic operation in the voltage conversion apparatus of the present embodiment will be described. FIG. 2 shows the waveform of the main part of this voltage converter divided into a normal state period T1 (overcurrent state Pex and non-overcurrent state Pnex) of the main conversion circuit 1 and a failure state period T2. It is. 2A shows the output voltage Va of the main conversion circuit 1, FIG. 2B shows the overcurrent detection voltage Vb of the comparator 62 in the overcurrent detection circuit 6, and FIG. 2C shows the second control circuit. 4, that is, the common output voltage Vc of the output voltage detection circuit 5 and the overcurrent detection circuit 6. (D) shows the determination voltage Vd which is the output voltage of the comparator 40 of the second control circuit 4, and (E) shows the output voltage of the first control circuit 3, that is, the output voltage of the inverting logic comparator 31. A certain stop control voltage Ve is shown. In addition, the code | symbol G in a figure represents a ground level (0V).

  The current detection transformer 107 of the main conversion circuit 1 detects a pulse current flowing through the primary low-voltage line L1, and outputs a pulsed current I1 having a magnitude corresponding to the pulse current. The current-voltage conversion circuit 108 generates a current detection voltage Vs1 by rectifying the current I1 output from the current detection transformer 107 by a half-wave rectification with a rectifier diode 108D and converting it into a DC voltage with a resistor 108R and a capacitor 108C. Is supplied to the resistor 30R1 connected to the negative input terminal of the inverting logic comparator 31 in the first control circuit 3. It can be said that the current detection voltage Vs1 is proportional to the magnitude of the output current of the main conversion circuit 1.

  Similarly, the current detection transformer 207 of the sub-conversion circuit 2 detects the pulse current flowing through the primary low-voltage line L2, and outputs a pulsed current I2 having a magnitude corresponding to the detected pulse current. The current-voltage conversion circuit 208 generates a current detection voltage Vs2 by half-wave rectifying the current I2 output from the current detection transformer 207 with a rectifier diode 208D and converting it into a DC voltage with a resistor 208R and a capacitor 208C. Is also supplied to the resistor 30R2 connected to the negative input terminal of the inverting logic comparator 31 in the first control circuit 3. It can be said that the current detection voltage Vs2 is proportional to the magnitude of the output current of the sub-conversion circuit 2.

  Thus, a voltage obtained by dividing the sum of the current detection voltage Vs1 and the current detection voltage Vs2 according to the resistance ratio of the resistors 30R1 and 30R2 is applied to the negative input terminal of the inverting logic comparator 31 of the first control circuit 3. Is entered. The inverting logic comparator 31 compares the divided voltage input to the negative side input terminal with the reference voltage Ref1. The reference voltage Ref1 is a boundary value for partitioning the total output of the voltage converter into a high output region and a low output region. For example, when the output current value I0 corresponding to the boundary value is 50 amperes, the reference voltage Ref1 is set to a value obtained by converting the current of 50 amperes into a voltage.

  When the divided voltage exceeds the reference voltage Ref1, the inverting logic comparator 31 of the first control circuit 3 outputs the stop control voltage Ve at the low level Lo (= 0 volts), while When the divided voltage is equal to or lower than the reference voltage Ref1, a stop control voltage Ve at a high level Hi (= Vcc2 = 5 volts, for example) is output. Here, the low-level stop control voltage Ve means that the output state of the voltage converter is in the high output region and that both the main conversion circuit 1 and the sub conversion circuit 2 are operated. On the other hand, the high-level stop control voltage Ve means that the output state of the voltage converter is in the low output region, and the sub-converter circuit 2 is stopped and only the main converter circuit 1 is operated.

  As shown in FIG. 2E, during normal operation (when the main conversion circuit 1 is not in failure), the output voltage of the first control circuit 3 is directly used as the stop control voltage Ve. Input to the switching control circuit 206. The switching control circuit 206 selectively controls whether or not to stop the sub-conversion circuit 2 in accordance with the level of the stop control voltage Ve (here, the output level of the first control circuit 3). Specifically, when the stop control voltage Ve is at a high level (in the low output region), the supply of the switching signals SG21 to SG24 to the switching circuit 201 is stopped and the sub-conversion circuit 2 is stopped. On the other hand, when the stop control voltage Ve is at a low level (in the high output region), the switching signals SG21 to SG24 are continuously supplied to the switching circuit 201, and the operation of the sub-conversion circuit 2 is continued.

  On the other hand, in the output voltage detection circuit 5, the inverting logic comparator 51 compares the divided voltage obtained by dividing the output voltage Va of the main conversion circuit 1 by the resistors 52 and 53 with the reference voltage Ref3, and the comparison result. The voltage according to is output. Specifically, as shown in FIG. 2A, when the output voltage Va is normal (for example, 14 volts), a low level Lo (= 0 volts) is output, and the output voltage Va decreases. If it is (for example, 9 volts), a high level Hi (= Vcc2 = for example, 5 volts) voltage is output. As a case where the output voltage Va of the main conversion circuit 1 is lower than normal, in addition to the case where the main conversion circuit 1 is out of order, the main conversion circuit 1 is in normal operation as described above, but is overcurrent. In some cases, the output voltage Va droops because of the state. However, since the low voltage battery 11 is connected to the output terminals T3 and T4, the output voltage Va does not immediately drop to 0 volts in any case, as shown in FIG. For example, it will stop at about 9 volts.

  In the overcurrent detection circuit 6, the comparator 62 compares the current detection voltage Vs1 from the current-voltage conversion circuit 108 of the main conversion circuit 1 with the reference voltage Ref5, and outputs an overcurrent detection voltage Vb that is the comparison result. Here, the reference voltage Ref5 is set to a voltage value corresponding to a current value that is several percent (for example, about 5%) larger than the rated output current (maximum output current Imax). When the current detection voltage Vs1 does not exceed the reference voltage Ref5 (that is, in the normal state (= non-overcurrent state) Pnex), the comparator 62, as shown in FIG. In the state where the overcurrent detection voltage Vb of (= 0 volts) is output while the current detection voltage Vs1 exceeds the reference voltage Ref5 (that is, in the case of the overcurrent state Pex), the high level Hi (= Vcc1 = 5 volts, for example) ) Overcurrent detection voltage Vb.

  In the example shown in FIG. 1, the output terminal of the comparator 62 is pulled up with the DC voltage Vcc1 from the main auxiliary power supply 109 of the main conversion circuit 1. However, even if the main auxiliary power supply 109 fails, The overcurrent detection voltage Vb from the comparator 62 becomes the low level Lo, and as a result, becomes the same logic level as the normal state (= non-overcurrent state) Pnex. For this reason, the failure of the main auxiliary power supply 109 does not hinder the final determination as to whether or not the main conversion circuit 1 has failed.

  The overcurrent detection voltage Vb output from the comparator 62 is further input to the negative side input terminal of the inverting logic comparator 61. The inverted logic comparator 61 outputs a voltage obtained by inverting the logic of the overcurrent detection voltage Vb. That is, in the normal state (= non-overcurrent state) Pnex, a high level Hi (= Vcc1 = 5 volts, for example) is output, while in an overcurrent state Pex, a low level Lo (= 0 volts) is output. To do.

  Thus, as shown in FIG. 2C, the common output voltage Vc of the output voltage detection circuit 5 and the overcurrent detection circuit 6 decreases the output voltage Va from 14 volts to 9 volts, for example, and overcurrent detection. Only when the voltage Vb becomes low level (that is, when the output of the main conversion circuit 1 decreases and is not in an overcurrent state), it becomes high level Hi (= Vcc2 = 5 volts, for example). After all, only when the output of the main conversion circuit 1 is reduced due to a factor other than the output droop due to overcurrent, the common output voltage Vc at the high level Hi indicating that the main conversion circuit 1 is in the failure state is the second control. It is input to the plus side input terminal of the comparator 40 in the circuit 4. That is, when the common output voltage Vc is at a low level, it can be seen that the main conversion circuit 1 is operating normally, and when the common output voltage Vc is at a high level, it can be seen that the main conversion circuit 1 has failed. .

  The comparator 40 of the second control circuit 4 compares the common output voltage Vc input to its positive input terminal with the reference voltage Ref2, and when the common output voltage Vc exceeds the reference voltage Ref2, FIG. As shown in (D), the determination voltage Vd of the high level Hi (= Vcc2 = 5 volts, for example) is output. On the other hand, when the common output voltage Vc does not exceed the reference voltage Ref2, the determination voltage Vd of the low level Lo (= 0 volts) is output. That is, the level of the determination voltage Vd means the same as the common output voltage Vc, and the low level Lo indicates the normal state of the device and the high level Hi indicates the device failure state. When the determination voltage Vd is at the high level Hi, feedback is applied to the positive side input terminal of the comparator 40 via the diode 45. As a result, as shown in FIG. 2D, even if the level of the common output voltage Vc of the output voltage detection circuit 5 and the overcurrent detection circuit 6 changes to the low level Lo as shown in FIG. And is applied to the base of the NPN transistor 44. Hereinafter, this latch operation will be described in more detail. In the initial state, since the output of the comparator 40 is low level Lo, no feedback is applied to the plus side input terminal by the output. Therefore, in this state, when the common output voltage Vc of the output voltage detection circuit 5 and the overcurrent detection circuit 6 becomes the low level Lo, the voltage Vc is input to the positive side input terminal of the comparator 40 via the resistor 46. As a result, the output of the comparator 40 becomes a low level Lo. Therefore, also in this case, feedback by the diode 45 is not applied. Next, when the common output voltage Vc is displaced to the high level Hi, the potential is input to the positive side input terminal of the comparator 40 via the resistor 46, and as a result, the output of the comparator 40 changes to the high level Hi. To do. In this state, feedback is applied by the diode 45, and a high level Hi potential is input to the positive side input terminal of the comparator 40. In this state, when the common output voltage Vc changes to the low level Lo again, the divided voltage of the DC voltage Vcc2 by the resistors 42 and 46 is input to the positive side input terminal of the comparator 40. In this case, the resistance value of the resistor 46 is set sufficiently larger than the resistor 42 so that the divided voltage is larger than the reference voltage Ref2, and therefore, the resistance value to the plus side input terminal of the comparator 40 is set. The input becomes the high level Hi, and as a result, the output of the comparator 40 is maintained at the high level Hi.

  The NPN transistor 44 is kept off when the determination voltage Vd applied to the base is at the low level Lo (that is, when the main conversion circuit 1 is operating normally). As a result, the output voltage of the inverting logic comparator 31 of the first control circuit 3 is supplied as it is to the switching control circuit 206 as the stop control voltage Ve. Therefore, as shown in FIG. 2E, the sum of the input voltage (that is, the current detection voltage Vs1 and the current detection voltage Vs2) to the negative side input terminal of the inverting logic comparator 31 is the resistance of the resistors 30R1 and 30R2. When the voltage divided according to the ratio exceeds the reference voltage Ref1 (when the output state of the voltage converter is in the high output region), the stop control voltage Ve becomes the low level Lo (= 0 volts). Both the main conversion circuit 1 and the sub conversion circuit 2 operate. On the other hand, when the input voltage to the negative input terminal of the inverting logic comparator 31 is equal to or lower than the reference voltage Ref1 (when the output state of the voltage converter is in the low output region), the stop control voltage Ve is high. The level becomes Hi (= Vcc2 = 5 volts, for example), so that the sub-conversion circuit 2 stops and only the main conversion circuit 1 operates.

  On the other hand, the NPN transistor 44 is turned on when the determination voltage Vd applied to the base is at the high level Hi (that is, when the main conversion circuit 1 has failed). As a result, the potential at the output terminal of the first control circuit 3 is forcibly lowered to a low level (= 0 volts) regardless of the output level of the inverting logic comparator 31. Therefore, the low level stop control voltage Ve is supplied to the switching control circuit 206. That is, the output level of the inverting logic comparator 31 is ignored, and the stop control of the sub-conversion circuit 2 by the first control circuit 3 is invalidated. Therefore, the sub-conversion circuit 2 always operates regardless of the sum of the current detection voltages Vs1 and Vs2 (regardless of whether the output state of the voltage converter is in the high output region or the low output region). It will be. That is, even when the main conversion circuit 1 fails, the sub conversion circuit 2 can continue the voltage conversion operation.

  Here, with reference to FIG. 2, operations when a failure occurs in the main conversion circuit 1 and when an overcurrent state occurs will be described in time series.

  The main conversion circuit 1 outputs, for example, 14 volts as the output voltage Va during normal operation. However, when a failure occurs in the main conversion circuit 1 (for example, a failure in the switching circuit 101 or the switching control circuit 106), the output voltage Va is output from the low-voltage battery 11 (see FIG. 2A). For example, the voltage drops to about 9 volts) (time t1 in FIG. 2).

  Then, as shown in FIGS. 2C and 2D, the determination voltage Vd changes from the low level Lo to the high level Hi together with the common output voltage Vc, and the stop control voltage Ve is forcibly lowered to the low level Lo. Therefore, the sub-conversion circuit 2 becomes operable. The sub-conversion circuit 2 starts operation at time t2 when a very short time T has elapsed from time t1, and outputs a voltage of, for example, 14 volts. As a result, the output DC voltage Vout (= output voltage Va) returns to 14 volts (FIG. 2A), so that the common output voltage Vc returns to the low level Lo (FIG. 2C).

  However, the determination voltage Vd is maintained at a value (high level Hi) before the change of the common output voltage Vc by the latch function of the comparator 40 in the second control circuit 4 (FIG. 2D). The stop control voltage Ve is maintained at the low level Lo. For this reason, even after the sub-conversion circuit 2 starts operating after the failure of the main conversion circuit 1 and the output voltage Va returns to the normal voltage, the sub-conversion circuit 2 remains operable, and the voltage conversion device The continuation of operation is guaranteed.

  When the output of the main converter circuit 1 is in a drooping state due to overcurrent, the output voltage Va drops to the output voltage (for example, about 9 volts) of the low voltage battery 11 (time t3 in FIG. 2). On the other hand, since the overcurrent detection voltage Vb changes from the low level Lo to the high level Hi, the output of the inverting logic comparator 61 becomes the low level Lo. Therefore, regardless of the output level of the inverting logic comparator 51, the common output voltage Vc maintains the low level Lo (FIG. 2C), so the determination voltage Vd also maintains the low level Lo (FIG. 2 ( D)). That is, when the main conversion circuit 1 is in the output overcurrent drooping state and the output is reduced, it is not determined that the main conversion circuit 1 is in failure. Accordingly, the stop control voltage Ve in this case is determined depending only on the voltage (the output voltage of the inverting logic comparator 31) determined based on the divided voltage sum of the current detection voltages Vs1 and Vs2. That is, whether or not the sub-conversion circuit 2 operates depends only on whether or not the output of the voltage converter is in the high output region.

  Thus, according to the voltage conversion apparatus of the present embodiment, the first control circuit 3 performs the main conversion in a state where the sum I of the output currents of the main conversion circuit 1 and the sub conversion circuit 2 exceeds the reference current I0. While both the circuit 1 and the sub-conversion circuit 2 are operated, the sub-conversion circuit 2 is controlled to stop when the sum I of the output currents is equal to or less than the reference current I0, and the second control circuit 4 Then, based on the detection results of the output voltage detection circuit 5 and the overcurrent detection circuit 6, it is determined whether or not the main conversion circuit 1 is in a failure state. Since the stop control for the circuit 2 is invalidated, the voltage conversion operation can be continued by the sub-conversion circuit 2 even when the main conversion circuit 1 fails.

  In particular, when it is determined that the main conversion circuit 1 has failed only by lowering the output voltage, there is a risk of erroneously determining failure even in the case of output droop due to overcurrent. Since the output droop due to overcurrent is excluded from the target of failure determination, more accurate failure determination is possible.

  Further, according to the voltage conversion device of the present embodiment, the voltage (DC voltage Vcc2) necessary for the operations of the sub-conversion circuit 2, the first control circuit 3, the second control circuit 4, and the output voltage detection circuit 5 is obtained. Since power is supplied from the sub auxiliary power supply 209 of the sub conversion circuit 2, even if the main auxiliary power supply 109 fails, the sub conversion circuit 2, the second control circuit 4, and the output voltage detection circuit 5 are normal. Can work.

  Although the overcurrent detection circuit 6 is driven by the DC voltage Vcc1 from the main auxiliary power supply 109, as described above, even if the main auxiliary power supply 109 fails, the main conversion circuit 1 fails. The logical configuration is made so as not to hinder the determination. For this reason, even when the main conversion circuit 1 including the main auxiliary power supply 109 stops operating at all, the second control circuit 4 invalidates the stop control for the sub-conversion circuit 2 by the first control circuit 3. Thus, the voltage conversion operation by the sub-conversion circuit 2 can be ensured.

  While the present invention has been described with reference to the embodiment, the present invention is not limited to this, and various modifications are possible. For example, in the above-described embodiment, the current detection transformer 107 (207) is provided in the primary low-voltage line L1 (L2). Instead, the current detection transformer is provided in the primary high-voltage line H1 (H2). 107 (207) may be provided.

In the embodiment and the modification described above, the negative input terminal of the inverting logic comparator 31 is
Although a voltage obtained by dividing the sum of the current detection voltage Vs1 and the current detection voltage Vs2 according to the resistance ratio of the resistors 30R1 and 30R2 is input, instead of this, for example, the current-voltage conversion circuit 108 The other end of the capacitor 108C (FIG. 1) is connected not to the ground line but to the output end of the current-voltage conversion circuit 208 (the side opposite to the ground side of the capacitor 208C), and the negative side of the operational amplifier 31 of the first control circuit 3 The output terminal of the current-voltage conversion circuit 108 may be connected to the input terminal. In this case, the sum of the current detection voltage Vs1 and the current detection voltage Vs2 is input as it is to the negative input terminal of the inverting logic comparator 31 of the first control circuit 3, so that the reference voltage Ref1 is A voltage corresponding to the reference current I0 may be employed.

  In the above-described embodiment and modification, the output terminal of the comparator 62 in the overcurrent detection circuit 6 is pulled up to the DC voltage Vcc1 by the main auxiliary power supply 109. Instead, the auxiliary auxiliary power supply 209 is used instead. The DC voltage Vcc2 may be pulled up.

  In the above-described embodiment and modification, the case where the switching circuits 101 and 102 are a full bridge type using four switching elements has been described. Instead, for example, a single switching element is used. It may be a forward type or a half bridge type using two switching elements.

  In the above-described embodiment and modification, the case where there is one sub-conversion circuit 2 has been described, but two or more sub-conversion circuits may be provided. In this case, for example, a parallel drive voltage converter can be configured as follows. That is, in addition to the main conversion circuit 1, two sub conversion circuits 2A and 2B (not shown) are provided, and the output area is divided into a high output area, a medium output area, and a low output area. Then, a parallel drive control circuit similar to the first control circuit 3 shown in FIG. 1 is provided, so that the main conversion circuit 1 and the three sub conversion circuits 2A and 2B are operated in parallel in the high output region. In the middle output region, the main conversion circuit 1 and the sub-conversion circuit 2A are operated in parallel, and only the main conversion circuit 1 is operated in the low output region. Further, at least one of the two sub-conversion circuits 2A and 2B is provided with an output voltage detection circuit, an overcurrent detection circuit similar to the output voltage detection circuit 5, the overcurrent detection circuit 6 and the second control circuit 4 shown in FIG. And a control circuit is provided. By this control circuit, when the main conversion circuit 1 fails, the stop control for at least one of the sub-conversion circuits 2A and 2B by the parallel drive control circuit is invalidated. As a result, even when the main conversion circuit 1 fails, the voltage conversion operation can be continued by at least one of the sub-conversion circuits 2A and 2B. The present invention can be similarly applied when the number of sub-conversion circuits is three or more.

It is a circuit diagram showing the structure of the voltage converter which concerns on one embodiment of this invention. It is a timing waveform diagram for demonstrating operation | movement of each part of the voltage converter of FIG. FIG. 5 is a characteristic diagram of output voltage versus output current for explaining an output overcurrent drooping state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Main conversion circuit, 2 ... Sub conversion circuit, 3 ... 1st control circuit, 4 ... 2nd control circuit, 5 ... Output voltage detection circuit, 6 ... Overcurrent detection circuit, 10 ... High voltage battery, 11 ... Low voltage Battery, 13 ... Load, 101, 201 ... Switching circuit, 102, 202 ... Transformer, 103, 203 ... Rectifier circuit, 104, 204 ... Smoothing circuit, 106, 206 ... Switching control circuit, 108, 208 ... Current-voltage conversion circuit 109, main auxiliary power source, 209, sub auxiliary power source, T1, T2 ... input terminal, T3, T4, output terminal, I0, reference current, Imax, maximum output current, Vs1, Vs2, current detection voltage, Va, output voltage. , Vb: overcurrent detection voltage, Vc: common output voltage, Vd: determination voltage, Ve: stop control voltage.

Claims (5)

Input and output terminals;
A main conversion circuit that is connected between the input terminal and the output terminal and converts a voltage input from the input terminal into a different voltage;
A sub-conversion circuit that is connected in parallel with the main conversion circuit between the input terminal and the output terminal, and converts a voltage input to the input terminal into a different voltage;
When the sum of the output currents of the main conversion circuit and the sub-conversion circuit exceeds a reference current, both the main conversion circuit and the sub-conversion circuit are operated, while the sum of the output currents is equal to or less than the reference current Then, a first control circuit that performs stop control on the sub-conversion circuit,
An output voltage detection circuit for detecting an output voltage at the output terminal;
Overcurrent detection means for detecting whether or not the main conversion circuit is in an output overcurrent droop state;
Based on detection results of the output voltage detection circuit and the overcurrent detection means, it is determined whether or not the main conversion circuit is in a failure state, and when it is determined that there is a failure, the sub-conversion by the first control circuit And a second control circuit for disabling stop control for the circuit. The second control circuit is configured when the output voltage detected by the output voltage detection circuit is lower than a reference voltage and the overcurrent detection state of the main conversion circuit is not detected by the overcurrent detection unit. The voltage conversion device according to claim 1, wherein the main conversion circuit is determined to be in a failure state. The overcurrent detection means includes
A current detection transformer having a primary winding connected to the input terminal, and a secondary winding magnetically coupled to the primary winding;
A current-voltage conversion circuit connected to the secondary winding of the detection transformer;
The voltage converter according to claim 1, further comprising a comparator provided on an output side of the current-voltage converter circuit. The main conversion circuit includes a main auxiliary power supply that operates as a power supply for driving the main conversion circuit using a voltage input from the input terminal. The voltage converter according to item. The sub-conversion circuit includes a sub-auxiliary power source that operates as a power source for the first and second control circuits and the output voltage detection circuit using a voltage input from the input terminal. The voltage converter of any one of Claim 1 thru | or 4.

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