CN113708442A - Bypass type battery equalization device and control method - Google Patents
Bypass type battery equalization device and control method Download PDFInfo
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- CN113708442A CN113708442A CN202110933303.9A CN202110933303A CN113708442A CN 113708442 A CN113708442 A CN 113708442A CN 202110933303 A CN202110933303 A CN 202110933303A CN 113708442 A CN113708442 A CN 113708442A
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
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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
- H02J7/0016—Circuits for equalisation of charge between batteries using shunting, discharge or bypass circuits
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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
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/00302—Overcharge protection
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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
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/0031—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using battery or load disconnect circuits
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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
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/0034—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using reverse polarity correcting or protecting circuits
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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
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/0036—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using connection detecting circuits
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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
- H02J7/0068—Battery or charger load switching, e.g. concurrent charging and load supply
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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
- H02J7/007—Regulation of charging or discharging current or voltage
- H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
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- Charge And Discharge Circuits For Batteries Or The Like (AREA)
Abstract
The invention designs a bypass type battery equalization device and a control method thereof. Compared with the prior art, the balance energy of the invention comes from an external charging power supply, thereby avoiding the discharge process of the single battery with high energy, reducing the discharge times of the single battery and prolonging the service life of the battery; in the process of charging the single batteries with lower energy, the constant current module is coordinated with the bypass module, so that the fully charged single batteries are protected, the overcharge phenomenon of the batteries is avoided, and all the single batteries can be fully charged, so that the effective capacity of the battery pack is fully utilized; the energy loss is reduced through the current control of the bypass module; the equalizing circuit does not need to carry out digital control on each battery monomer specially, and the workload of a CPU in the BMS is reduced.
Description
Technical Field
The invention relates to a battery bypass type active equalization device, belongs to a management system of related batteries such as lithium ion batteries and the like, and particularly relates to an equalization circuit for equalizing a plurality of single batteries in series.
Background
With the development of lithium batteries and energy storage technologies, the requirements on battery management systems are also higher and higher. A plurality of battery cells are connected in series, and unbalanced problems can be generated in the charging and discharging process due to inconsistent performance of the battery cells, so that the aging of the battery is caused, and the service life and the safety of the battery are influenced.
At present, a passive equalization method and an active equalization method are mainly used for equalizing the battery. The passive equalization method is mainly a resistance energy consumption type, two ends of each single battery are connected with a resistor shunt in parallel, and the energy consumption equalization is to consume redundant energy in batteries with large capacity, so that the voltage equalization of the whole battery set is realized. For example, chinese patents CN102457078A, CN106329667A, CN102195314A, CN107492924A and CN108063473A disclose several different forms of energy consuming equalization circuits and control methods thereof, respectively. Energy-consuming balancing not only consumes valuable energy but also causes the system to heat up.
The active balancing method is to transfer the monomer energy with high energy to the monomer energy with low energy or supplement the whole group of energy to the monomer lowest battery, and an energy storage link is needed in the implementation process, so that the energy is redistributed through the link. Chinese patents CN207098716U, CN103248077A, CN105391130A, CN102111003A and CN104113110A disclose several battery equalization circuits using inductive energy storage, while CN107994651A, CN103051029A, CN107579575A, CN107317376A and CN106816930A disclose several battery equalization circuits using capacitive energy storage. No matter inductive energy storage or capacitive energy storage is adopted, a plurality of power switching devices of high-speed switches are needed, the cost is high, the control is complex, and the balance control cannot be simultaneously carried out on any single battery, so the balance efficiency is low.
Chinese patents CN104577227A, CN104201743, CN107785957A and CN107834655A disclose several centralized active equalization circuits using transformer isolation or using DC/DC converters, and since only one transformer is used to equalize all the single batteries, there are many taps of the transformer, which makes the installation difficult and is not suitable for the change of the battery pack. In addition, a plurality of high-speed power switching devices are needed, and the cost is high, and the control is complicated. And a plurality of arbitrary cells cannot be equalized at the same time.
Chinese patent CN203933055U discloses a battery equalization circuit based on Flyback converter, which realizes battery equalization by transferring energy from single battery to battery pack. However, this circuit structure is complicated, and requires power switches, selection switches, power diodes, and electrolytic capacitors in the same number as the number of the single batteries, which results in a very high cost. In addition, the circuit can only transfer energy to one single battery or a plurality of adjacent batteries through the selection switch, so that the balance of any plurality of batteries cannot be realized, and the balance efficiency is low. In addition, the final equalization effect of the equalization circuit cannot fully charge the electric energy, and extra control is needed to charge the battery pack.
In summary, the passive equalization circuit in the prior art not only consumes valuable energy, but also causes problems such as system heating. The active equalization needs a plurality of high-speed power switching devices, has high cost, complex control, needs heat dissipation, cannot equalize a plurality of arbitrary single batteries at the same time, and has low equalization efficiency. In addition, some circuits cannot supplement the energy of the battery pack through equalization to achieve the purpose of fully charging the battery.
Disclosure of Invention
The invention provides a battery bypass type active equalization circuit and a control method aiming at the defects in the prior art. Firstly, the invention does not need high-speed power switch devices and does not need complex passive devices such as inductors, capacitors, transformers and the like, thereby having small volume and light weight and avoiding the defects of an active equalizing circuit. Secondly, the invention can continuously supplement electric energy to the laggard single batteries to achieve the purpose that all batteries can be fully charged, thereby avoiding the defect of passive balance.
The technical scheme adopted by the invention is as follows:
in order to achieve the purpose, the bypass type battery balancing device comprises a battery pack, a constant current module, a charging control module, a bypass module, a sampling module, a control module and a discharging control unit, wherein the battery pack is formed by connecting a plurality of single batteries in series; the input end of the control module is connected with the sampling module, the output end of the control module is connected with the charging control module and the discharging control unit and used for charging, discharging and balancing control, and the sampling module is connected with the sampling end of each single battery in the battery pack; the discharge control unit is connected with the anode of the battery pack and used for controlling the output current of the battery; the bypass module is connected with each single battery in the battery pack in parallel, and whether the balancing current bypasses is controlled during balancing; the input end of the constant current module is connected with the charging anode, and the output end of the constant current module is connected with the anode of the battery pack through the charging control module and used for battery equalization; the bypass type battery balancing device utilizes the external charging end to balance the battery pack, reduces the charging and discharging times of the battery core in the battery pack, improves the utilization rate of energy and prolongs the service life of the battery.
The sampling module comprises a battery voltage acquisition circuit, and the battery voltage acquisition circuit is connected with each single battery and used for detecting the voltage information of all the single batteries in real time and feeding back the voltage information to the control module.
The control module can compare the voltage of each single battery collected by the sampling module with a threshold voltage, the threshold voltage can be set according to different single batteries, and the control module controls power switches in the charging control module and the discharging control unit according to the set voltage.
The charging control module comprises a charging switch, an equalizing switch, a first diode and a second diode;
the charging switch is connected with the first diodes in series, the equalizing switch is connected with the second diodes in series, and the two first diodes are connected with the cathodes of the second diodes and the anodes of the battery packs;
the first diode and the second diode which are conducted in one direction are used for preventing current from reversing.
The control output end of the control module is respectively connected with the charging switch of the charging control module, the equalizing switch of the charging control module and the grid electrode of the Q3 of the discharging control unit, and the state transition among charging, discharging and equalizing of the bypass type battery equalizing device is controlled by driving the charging switch, the equalizing switch and the discharging control unit to be switched on and off.
The input end of the constant current module is connected with the charging anode, and the output end of the constant current module is connected with the drain electrode of the equalizing switch in the charging control module; the constant current module can realize the constancy of balanced current, and the magnitude of the constant current can be set according to the magnitude of the battery capacity; when the equalizing loop is disconnected by the equalizing switch, the output voltage of the constant current module 1 is not higher than the charging voltage.
The constant current module comprises a three-terminal voltage stabilizer and a feedback resistor; the input end of the three-terminal voltage stabilizer is used as the input end of the constant current module, the output end of the three-terminal voltage stabilizer is connected with the feedback resistor, and the other end of the feedback resistor is the output end of the constant current module and is connected with the feedback end of the three-terminal voltage stabilizer.
The constant current module also comprises a detection driving unit, a driving resistor, a power amplification triode and a sampling resistor; the collector of the power amplifier triode is the input end of the constant current module, the emitter is connected with the sampling resistor, the other end of the sampling resistor is the output end of the constant current module, the detection end of the detection driving unit is connected with the two ends of the sampling resistor, negative feedback is formed by reverse amplification inside the detection driving unit, and the power amplifier triode is driven by the driving resistor to work in a constant current amplification state.
The bypass module comprises a triode, a controllable precise voltage-stabilizing source and four resistors with specific resistance values, namely a first resistor, a second resistor, a third resistor and a fourth resistor;
the first resistor is connected with the third resistor in series, the second resistor is connected with the controllable precise voltage-stabilizing source in series, the triode is connected with the fourth resistor in series, and the three branches are connected to two ends of the single battery in parallel; the third resistor is connected in parallel between the reference electrode and the anode of the controllable precise voltage-stabilizing source, and the base electrode of the triode is connected with the cathode of the controllable precise voltage-stabilizing source and the second resistor;
when the triode is conducted, the balance current flows through the bypass module, and the parallel single batteries are bypassed.
The bypass module further comprises a triode, a second resistor, a fourth resistor and an optocoupler;
one end of a second resistor is connected with the anode of the single battery, the other end of the second resistor is connected with the collector of a triode in the optocoupler, and the emitter of the triode in the optocoupler is connected with the cathode of the single battery; the triode is connected with the fourth resistor in series and connected to two ends of the single battery in parallel; the base electrode of the triode is connected with the collector electrode of the triode in the optocoupler; the cathode of the light emitting diode in the optical coupler is connected with the ground of the control system, and the anode of the light emitting diode in the optical coupler is connected with the control module.
The series battery lead-out wires in the battery pack are divided into two groups, namely a bypass module connecting end and a sampling module connecting end.
The fourth resistor has a resistance value of R4＝Umax/iOWherein U ismaxFor the maximum voltage at which the cell begins to operate in equilibrium, iOThe constant current is the output constant current of the constant current module; the constant current i output by the constant current module when the balance switch is turned offOWhen the voltage of the input end of the constant current module is zero, the voltage of the input end of the constant current module is equal to the voltage of the output end and is approximately equal to the voltage of the charging positive electrode;
the resistance values of the first resistor and the third resistor need to satisfy a formula
Wherein U isrefIs the reference voltage of a controllable precise voltage-stabilizing source.
The implementation steps of the system state control strategy are as follows:
step A-1: when the voltages of all the single batteries detected by the sampling module are lower than the upper limit U of the threshold voltagemaxWhen the battery pack is charged, the control module drives a charging switch in the charging control module to be switched on and a balancing switch in the charging control module to be switched off, so that the battery pack starts to be charged;
step A-2: when the voltage of any single battery detected by the sampling module is equal to the upper limit U of the threshold voltagemaxWhen the battery pack is in a balanced state, the control module drives a charging switch in the charging control module to be turned off, and then turns on a balancing switch;
step A-3: when the voltages of all the single batteries detected by the sampling module are equal to the upper limit U of the threshold voltagemaxThe control module drives charging in the charging control moduleThe switch and the equalizing switch are both turned off, the discharge control unit Q3 is turned on, and the battery pack starts to be in a discharge state;
step A-4: when the voltage of any single battery detected by the sampling module is equal to the lower limit U of the threshold voltageminWhen the battery pack is charged, the control module drives the discharging control unit Q3 to be switched off, the charging switch in the charging control module is switched on, the equalizing switch is switched off, and the battery pack enters the charging state again.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages and effects:
the invention has the advantages that the balance energy comes from an external charging power supply, the discharge process of the single battery with high energy is avoided, the discharge times of the single battery are reduced, and the service life of the battery is prolonged.
The invention has the advantages that in the process of charging the single batteries with lower energy, the constant current module and the bypass module are coordinated and matched, so that the fully charged single batteries are protected, the phenomenon of overcharging of the batteries is avoided, and all the single batteries can be fully charged, thereby fully utilizing the effective capacity of the battery pack.
One effect of the present invention is that, through the current control of the bypass module, the energy transfer between different single batteries via the intermediate circuit is avoided, and the energy loss is reduced.
The invention has the advantages that no components such as inductance, capacitance and the like for energy storage are needed, and passive components such as a transformer and the like are not needed, so the volume is small and the cost is low.
One effect of the present invention is that the balancing circuit does not need to perform digital control for each battery cell, thereby reducing the workload of the CPU in the BMS.
Drawings
Fig. 1 is a cell state one of the bypass type battery equalization apparatus of the present invention;
fig. 2 is a cell state two of the bypass type battery equalization apparatus of the present invention;
fig. 3 is a cell state three of the bypass type battery equalizing apparatus of the present invention;
fig. 4 is a cell state four of the bypass type battery equalizing apparatus of the present invention;
fig. 5 is a first schematic diagram of a bypass type battery equalization apparatus according to the present invention;
fig. 6 is a second schematic diagram of the bypass type battery equalization apparatus of the present invention;
fig. 7 is a schematic diagram of a constant current module of the bypass type battery equalization apparatus of the present invention;
fig. 8 is a view showing one embodiment of a constant current module of the bypass type battery equalization apparatus according to the present invention;
fig. 9 is a second embodiment of the constant current module of the bypass type battery equalization apparatus of the present invention;
fig. 10 is a schematic diagram of a charge control module of the bypass type battery equalizing apparatus of the present invention;
fig. 11 is a schematic diagram of a bypass module of the bypass type battery equalization apparatus according to the present invention;
fig. 12 is a second schematic diagram of a bypass module of the bypass type battery equalization apparatus of the present invention;
fig. 13 is a schematic diagram of battery pack connection of the bypass type battery equalization apparatus of the present invention.
In the drawings, each reference numeral represents a component:
1. the device comprises a constant current module, 2, a charging control module, 3, a bypass module, 4, a battery pack, 5, a sampling module, 6, a control module, 7, a discharging control unit, 101, a three-terminal regulator, 102, a feedback resistor, 103, a detection driving unit, 104, a driving resistor, 105, a power amplifier triode, 106, a sampling resistor, 201, a charging switch, 202, an equalizing switch, 203, a first diode, 204, a second diode, 301, a triode, 302, a controllable precision voltage stabilizing source, 303, a first resistor, 304, a second resistor, 305, a third resistor, 306, a fourth resistor, 307, an optical coupler, 401, a series battery, 402, a bypass module connecting end, 403 and a sampling module connecting end.
Detailed Description
The invention will be further described with reference to the accompanying drawings.
Fig. 1 to 4 are schematic diagrams illustrating a principle of battery balancing, and the capacities of the individual batteries of the battery pack are different from each other, and it can be seen from fig. 1 to 4 that the maximum available capacity of the battery pack is smaller than or equal to the capacity of the individual battery with the minimum capacity. In the case of fig. 2, fig. 3, and fig. 4, the maximum available capacity Qmax of the battery pack is smaller than the maximum available capacity of the battery with the smallest available capacity in the battery pack, so that it is necessary to fully charge each battery through energy balance to ensure that the available capacity of the battery pack 4 reaches the maximum value.
In the equalization control process, because the equalization energy comes from an external charging power supply, the discharge process of the single battery with high energy is avoided, the discharge times of the single battery are reduced, and the service life of the battery is prolonged. Meanwhile, in the process of charging the single batteries with lower energy, the constant current module and the bypass module are coordinated and matched, so that the fully charged single batteries are protected, the phenomenon of overcharging of the batteries is avoided, all the single batteries can be fully charged, and the effective capacity of the battery pack is fully utilized. Through bypass module current control, avoided the energy to pass through the transfer of intermediate circuit between different battery cells, reduced energy loss.
Fig. 5 is a schematic diagram of a bypass type battery equalization apparatus, and includes a constant current module 1, a charge control module 2, a bypass module 3, a battery pack 4, a sampling module 5, a control module 6, and a discharge control unit 7. In this embodiment, the battery pack 4 is a series battery 401 composed of a plurality of single batteries, as shown in fig. 13, wherein each single battery is respectively connected to the bypass module connection terminal 402 for battery equalization control, and the sampling module connection terminal 403 for single battery voltage detection.
Every battery cell connects in parallel with bypass module 3 respectively through bypass module link 402, and sampling module link 403 links to each other with sampling module 5, and sampling module (5) contain battery voltage acquisition circuit, battery voltage acquisition circuit is connected with every battery cell, gives control module 6 through sampling module 5 with battery voltage information transmission. The output terminal of the control module 6 is connected to the gates of the charging switch 201, the equalizing switch 202 of the charging control module 2, and the Q3 of the discharging control unit 7, respectively, and controls the state transition between charging, discharging, and equalizing of the bypass type battery equalizing apparatus by driving them on and off. The output end of the charging control module 2 is connected with the anode of the battery pack 4, the number of the input ends of the charging control module 2 is two, one input end is directly connected to the charging anode, and the other input end is connected to the charging anode through the constant current module 1. The discharge control unit 7 controls the positive electrode of the battery pack 4 to output current to the outside. The control module 6 can compare the voltage of each single battery collected by the sampling module 5 with a threshold voltage, the threshold voltage can be set according to the difference of the single batteries, and the power switches in the charging control module 2 and the discharging control unit 7 are controlled according to the set voltage, that is, the control module 6 controls the charging control module 2 and the discharging control unit 7 according to the charging and discharging state and the voltage of the single batteries.
Fig. 10 is a schematic diagram of a charge control module 2 of the bypass type battery equalization apparatus according to the present invention, which includes a charge switch 201, an equalization switch 202, a first diode 203, and a second diode 204. Preferably, the charging switch 201 and the equalizing switch 202 may be power semiconductor devices such as MOSFET and IGBT, or may be mechanical switches such as contactor and relay. The charging switch 201 is connected in series with the first diode 203, the equalizing switch 202 is connected in series with the second diode 204, and the two first diodes 203 are connected with the cathode of the second diode 204 and with the anode of the battery pack 4. The first diode 203 and the second diode 204 conducting in one direction are used to prevent the current from reversing direction.
When the voltage of the single battery detected by the sampling module 5 is lower than the upper limit U of the threshold voltagemaxAt this time, the charging operation can be performed. At this time, the control module 6 controls the charging switch 201 in the charging control module 2 to be turned on. The charging current passes through the charging anode, the charging switch 201, the first diode 203, the series battery 401, and the charging cathode to form a charging loop, and charges the battery pack 4.
When any single battery voltage detected by the sampling module 5 is higher than the upper limit U of the threshold voltagemaxIn order to protect the single battery, the control module 6 controls the charging switch 201 in the charging control module 2 to be turned off, and stops charging.
Since other single batteries are not fully charged, the situations shown in fig. 2, 3 and 4 can occur after the charging is stopped, and the available capacity of the whole battery pack 4 is seriously influenced. Therefore, the control module 6 controls the equalization switch 202 in the charging control module 2 to be turned on. At this time, the equalizing current output by the constant current module 1 passes through the equalizing switch 202 and the second diode 204 to continuously charge the equalizing current i into the battery pack 4O。
Since the single cells in the battery pack 4 are connected in series, if the equalizing current i is charged at this timeOThe overcharging phenomenon of the fully charged single battery can be caused, the service life of the single battery is influenced, and even the single battery is damaged, so that danger is caused. For this purpose, it is necessary to bypass the equalization current of the already charged cells, see fig. 5.
In one embodiment, the bypass module 3 includes a transistor 301, a controllable precision regulator 302, and four resistors with specific resistance values, i.e., a first resistor, a fourth resistor 303 and a resistor 306, as shown in fig. 11. The transistor 301 is preferably a PNP transistor. The first resistor 303 is connected with the third resistor 305 in series, the second resistor 304 is connected with the controllable precision voltage-stabilizing source 302 in series, the triode 301 is connected with the fourth resistor 306 in series, and the three branches are connected to two ends of the single battery in parallel; the third resistor 305 is connected in parallel between the reference electrode and the anode of the controllable precision voltage regulator 302, and the base of the triode 301 is connected with the cathode of the controllable precision voltage regulator 302 and the second resistor 304.
The first resistor 303 and the third resistor 305 are connected in series and across the single battery, and divide the voltage of the single battery. Assuming a cell voltage of ubIn FIG. 11, the voltage at point A is
R1Is a first resistor 303, R3Is a third resistor 305. Let ub＝UmaxWhen the temperature of the water is higher than the set temperature,
wherein U isrefIs a reference voltage of a controllable precision regulated voltage source 302 when u isA≥UrefWhen the voltage is applied, the controllable precision voltage regulator 302 is turned on to pull down the voltage at point B, i.e. the voltage at point B is reducedThe base voltage of the transistor 301 is pulled down, turning on the transistor 301. The current i flowing through the transistor 301 is the bypass current.
Preferably, the fourth resistor 306 has a resistance value of
Then the current i is equalizedOAll the current flows through the fourth resistor 306, so that the current charged into the corresponding unit cell is 0, and the unit cell does not generate an overcharge phenomenon.
When the control module 6 detects that the voltage of all the single batteries is higher than the upper limit U of the threshold voltage through the sampling module 5maxWhen the battery pack 4 reaches the full-cell slow-charging state shown in fig. 1(a), the capacity of the battery is utilized to the maximum extent, the overcharge of the battery is prevented, the service life of the battery is prolonged, and the safety of the battery is guaranteed.
When discharging is needed, the control module 6 controls the discharging control unit 7 to be conducted to start discharging, and when the sampling module 5 detects that the voltage of any single battery is less than or equal to the lower limit U of the threshold voltageminAnd meanwhile, the control module 6 controls the discharge control unit 7 to be turned off to stop discharging, so that the battery is prevented from being damaged by overdischarge.
In one embodiment, a bypass type battery equalization apparatus shown in fig. 6 may be employed. The charging switch 201 is preferably turned on, the input end of the equalization switch 202 is connected in parallel, and is connected to the negative electrode of the battery pack 4, the negative electrode of the first diode 203 is connected to the charging negative electrode, and the negative electrode of the second diode 204 is connected to the charging negative electrode through the constant current module 1. The principle and mode of operation are similar to the previous embodiment.
Fig. 7 is a schematic diagram of the constant current module 1 of the bypass type battery equalization apparatus of the present invention. The constant current module 1 has an input terminal and an output terminal, wherein the constant current conversion circuit can be implemented by a linear analog circuit or a switching power supply. The constant current circuit can control the output current to be kept constant regardless of the adopted mode, and when the equalizing loop is disconnected by the equalizing switch 202, the output voltage of the constant current module 1 is not higher than the charging voltage.
In one embodiment, the constant current module 1 shown in fig. 8 is preferably adopted, and comprises a three-terminal regulator 101 and a feedback resistor 102. Preferably, the LM317 is adopted as the three-terminal regulator 101, the input terminal of the three-terminal regulator 101 is adopted as the input terminal of the constant current module 1, the output terminal of the three-terminal regulator 101 is connected with the feedback resistor 102, and the other terminal of the feedback resistor 102 is the output terminal of the constant current module 1 and is connected with the feedback terminal of the three-terminal regulator 101. By adjusting the resistance of the feedback resistor 102, the output constant current i can be adjustedOThe size of (2).
In one embodiment, the constant current module 1 shown in fig. 9 is preferably adopted, and includes a detection driving unit 103, a driving resistor 104, a power amplification triode 105, and a sampling resistor 106. The collector of the power amplifier triode 105 is the input end of the constant current module 1, the emitter is connected with the sampling resistor 106, the other end of the sampling resistor 106 is the output end of the constant current module 1, the detection end of the detection driving unit 103 is connected with the two ends of the sampling resistor 106, and the output end of the detection driving unit 103 drives the base of the power amplifier triode 105 through the driving resistor 104.
When outputting a constant current iOWhen the current flows through the sampling resistor 106, voltage is generated at two ends of the sampling resistor 106, the voltage is reversely amplified through an operational amplifier in the detection driving unit 103, then base current of the power amplifier triode 105 is generated through a driving circuit, and the constant current i can be controlled by adjusting the base current of the power amplifier triode 105OThe size of (2). Preferably, the power amplifier transistor 105 operates in a constant current amplification state. Because the detection driving unit 103 detects the constant current iONegative feedback control is performed, so that iOWill remain constant. When the equalizing loop is disconnected by the equalizing switch 202, the base current output by the detection driving unit 103 reaches the maximum, and the power amplifier triode 105 is in saturated conduction, so that the output voltage of the constant current module 1 is approximately equal to the input voltage, and high voltage cannot be generated.
In this embodiment, the charging circuit is divided into two branches by the charging switch 201 and the equalizing switch 202 for controlling respectively. The branch controlled by the charging switch 201 is used for charging a large current, and the branch controlled by the balancing switch 202 is used for switching on and off the balancing current during the balancing operation of the battery.
In one embodiment, the bypass module 3 shown in fig. 12 may be adopted, and includes a transistor 301, a second resistor 304, a fourth resistor 306, and an optocoupler 307. In this embodiment, the bypass module 3 itself does not need to set the bypass-on voltage, but the control module 6 is used to digitally control the bypass module 3. One end of the second resistor 304 is connected with the anode of the single battery, the other end of the second resistor 304 is connected with the collector of the triode in the optocoupler 307, and the emitter of the triode in the optocoupler 307 is connected with the cathode of the single battery; the triode 301 is connected in series with the fourth resistor 306 and connected to two ends of the single battery in parallel; the base electrode of the triode 301 is connected with the collector electrode of the triode in the optocoupler 307; the cathode of the light emitting diode in the optical coupler 307 is connected with the ground of the control system, and the anode is connected with the control module 6.
In this embodiment, when the control module 6 detects that the voltage of the single battery reaches the upper limit U of the threshold voltagemaxWhen the current is flowing through the bypass module 3, the control module 6 outputs a high level to control the conduction of the light emitting diode in the optocoupler 307, and the conduction of the isolation control triode 301 causes the balance current to flow through the bypass module 3, so that the parallel single batteries are bypassed.
The invention has no inductance, capacitance and other elements for energy storage, and no passive devices such as transformer, so the volume is small and the cost is low. The equalizing circuit does not need to carry out digital control on each battery monomer specially, and the workload of a CPU in the BMS is reduced.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention, and the invention is therefore not to be limited to the embodiments illustrated herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (13)
1. A bypass-type battery equalization apparatus comprising a battery pack (4) in which a plurality of unit batteries are connected in series, characterized by further comprising: the device comprises a constant current module (1), a charging control module (2), a bypass module (3), a sampling module (5), a control module (6) and a discharging control unit (7);
the input end of the control module (6) is connected with the sampling module (5), the output end of the control module is connected with the charging control module (2) and the discharging control unit (7) and is used for charging and discharging and balancing control, and the sampling module (5) is connected with the sampling end of each single battery in the battery pack (4);
the discharge control unit (7) is connected with the anode of the battery pack (4) and is used for controlling the output current of the battery;
the bypass module (3) is connected with each single battery in the battery pack (4) in parallel, and whether the balancing current bypasses is controlled during balancing;
the input end of the constant current module (1) is connected with a charging anode, and the output end of the constant current module is connected with the anode of the battery pack (4) through the charging control module (2) and used for battery equalization;
the bypass type battery balancing device utilizes an external charging end to balance the battery pack (4), reduces the charging and discharging times of an electric core inside the battery pack (4), improves the utilization rate of energy and prolongs the service life of the battery.
2. The battery balancing device of claim 1, wherein the sampling module (5) comprises a battery voltage acquisition circuit, and the battery voltage acquisition circuit is connected to each battery cell and is used for detecting the voltage information of all battery cells in real time and feeding the voltage information back to the control module (6).
3. The battery balancing device of the bypass type according to claim 1, wherein the control module (6) is capable of comparing the voltage of each battery cell collected by the sampling module (5) with a threshold voltage, the threshold voltage is set by itself according to the battery cell, and the control module (2) and the power switch in the discharge control unit (7) are controlled according to the set voltage.
4. Battery equalizing device according to claim 1, characterized in that said charge control module (2) comprises a charge switch (201), an equalizing switch (202), a first diode (203), a second diode (204);
the charging switch (201) is connected in series with the first diodes (203), the equalizing switch (202) is connected in series with the second diodes (204), and the two first diodes (203) are connected with the cathode of the second diode (204) and with the anode of the battery pack (4);
the first diode (203) and the second diode (204) which are conducted in one direction are used for preventing the current from reversing.
5. The battery balancing device of the bypass type according to claim 1, characterized in that the control output of the control module (6) is connected to the gates of the charging switch (201), the balancing switch (202) of the charging control module (2) and the Q3 of the discharging control unit (7), respectively, and the state transition between charging, discharging and balancing of the battery balancing device of the bypass type is controlled by driving them on and off.
6. The battery equalization device of the bypass type according to claim 1, characterized in that the input terminal of the constant current module (1) is connected to the charging positive electrode, and the output terminal of the constant current module (1) is connected to the drain terminal of the equalization switch (202) in the charging control module (2); the constant current module (1) can realize the constancy of balanced current, and the magnitude of the constant current can be set according to the magnitude of the battery capacity; when the equalizing loop is disconnected by the equalizing switch (202), the output voltage of the constant current module 1 is not higher than the charging voltage.
7. The battery balancing device of the bypass type according to claim 1 and claim 6, characterized in that the constant current module (1) comprises a three-terminal regulator (101), a feedback resistor (102); the input end of the three-terminal regulator (101) is used as the input end of the constant current module (1), the output end of the three-terminal regulator (101) is connected with the feedback resistor (102), and the other end of the feedback resistor (102) is the output end of the constant current module (1) and is connected with the feedback end of the three-terminal regulator (101).
8. The battery balancing device of the bypass type according to claim 1 and claim 6, wherein the constant current module (1) further comprises a detection driving unit (103), a driving resistor (104), a power amplifier triode (105) and a sampling resistor (106); the collector of the power amplifier triode (105) is the input end of the constant current module (1), the emitter is connected with the sampling resistor (106), the other end of the sampling resistor (106) is the output end of the constant current module (1), the detection end of the detection driving unit (103) is connected with the two ends of the sampling resistor (106), negative feedback is formed by internal reverse amplification, and the power amplifier triode (105) is driven by the driving resistor (104) to work in a constant current amplification state.
9. The battery equalization device of the bypass type according to claim 1, characterized in that the bypass module (3) comprises a triode (301), a controllable precision voltage regulator (302), a first resistor (303), a second resistor (304), a third resistor (305) and a fourth resistor (306), wherein the resistors have specific resistance values;
the first resistor (303) is connected with the third resistor (305) in series, the second resistor (304) is connected with the controllable precise voltage-stabilizing source (302) in series, the triode (301) is connected with the fourth resistor (306) in series, and the three branches are connected to two ends of the single battery in parallel; the third resistor (305) is connected in parallel between the reference electrode and the anode of the controllable precise voltage-stabilizing source (302), and the base electrode of the triode (301) is connected with the cathode of the controllable precise voltage-stabilizing source (302) and the second resistor (304);
when the triode (301) is conducted, the equalizing current flows through the bypass module (3), and the parallel single batteries are bypassed.
10. The battery balancing device of the bypass type according to claim 1, wherein the bypass module (3) further comprises a triode (301), a second resistor (304), a fourth resistor (306), and an optocoupler (307);
one end of a second resistor (304) is connected with the anode of the single battery, the other end of the second resistor (304) is connected with the collector of a triode in the optocoupler (307), and the emitter of the triode in the optocoupler (307) is connected with the cathode of the single battery; the triode (301) is connected with the fourth resistor (306) in series and connected to two ends of the single battery in parallel; the base electrode of the triode (301) is connected with the collector electrode of the triode in the optocoupler (307); the cathode of the light emitting diode in the optical coupler (307) is connected with the ground of the control system, and the anode of the light emitting diode is connected with the control module (6).
11. A battery equalizing device of the bypass type according to claim 1, characterized in that the outgoing lines of the series-connected cells (401) in the battery pack (4) are divided into two groups, a bypass module connection terminal (402) and a sampling module connection terminal (403).
12. Battery equalizing device according to claims 1 and 9, characterized in that the fourth resistor (306) has a resistance value R4＝Umax/iOWherein U ismaxFor the maximum voltage at which the cell begins to operate in equilibrium, iOIs the constant current output by the constant current module (1); the constant current i output by the constant current module (1) when the balance switch (202) is turned offOWhen the voltage of the input end of the constant current module (1) is zero, the voltage of the input end is equal to the voltage of the output end and is approximately equal to the voltage of the charging positive electrode;
the values of the first resistor (303) and the third resistor (305) need to satisfy the formula
Wherein U isrefIs a reference voltage of a controllable precision regulated voltage source (302).
13. The control method of the bypass-type battery equalization apparatus according to any one of claims 1 to 12, characterized in that the system state control strategy is implemented by the steps of:
step A-1: when the voltages of all the single batteries detected by the sampling module (5) are lower than the upper limit U of the threshold voltagemaxWhen the charging control module (2) is charged, the control module (6) drives a charging switch (201) in the charging control module (2) to be switched on, an equalizing switch (202) in the charging control module is switched off, and the battery pack (4) starts to be charged;
step A-2: when the sampling module (5) detectsThe voltage of any single battery is equal to the upper limit U of the threshold voltagemaxWhen the battery pack is in a balanced state, the control module (6) drives a charging switch (201) in the charging control module (2) to be turned off, and then a balancing switch (202) is turned on, so that the battery pack (4) starts to be in a balanced state;
step A-3: when the voltages of all the single batteries detected by the sampling module (5) are equal to the upper limit U of the threshold voltagemaxWhen the battery pack is in a discharging state, the control module (6) drives a charging switch (201) and an equalizing switch (202) in the charging control module (2) to be turned off, a discharging control unit (7) Q3 is turned on, and the battery pack (4) starts to be in the discharging state;
step A-4: when the voltage of any single battery detected by the sampling module (5) is equal to the lower limit U of the threshold voltageminWhen the charging control module (2) is in a charging state, the control module (6) drives the discharging control unit (7) Q3 to be turned off, the charging switch (201) in the discharging control unit (7) is turned on, the equalizing switch (202) in the discharging control unit is turned off, and the battery pack enters the charging state again.
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