JP2013005677A - Cell balancer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell balancer that can effectively use discharge energy obtained when performing a cell balance, while suppressing a dispersion of each output voltage of a plurality of secondary batteries constituting a main battery.SOLUTION: A cell balancer 1 comprises: a transformer 6 in which a primary coil 6-1 and a secondary coil 6-2 are electromagnetically coupled as an AC current flows into the primary coil 6-1 owing to an intermittent discharging of modules 13; a DC-DC converter 4 provided between the secondary coil 6-2 and an auxiliary battery 7; a battery ECU8 which, when output voltage differences of modules 13 are equal to or more than a threshold value, makes prescribed modules 13 discharge intermittently so that an output voltage of each module 13 becomes balanced, and also makes a voltage applied to the secondary coil 6-2 drop so as to charge the auxiliary battery 7 by an output voltage from the DC-DC converter 4.

Description

  The present invention relates to a cell balance device for suppressing variation in output voltage of each secondary battery constituting a main battery mounted on a vehicle.

  As a battery mounted on a vehicle such as a hybrid vehicle or an electric vehicle, there is an auxiliary battery that supplies electric power to an electric equipment such as a main battery or a car navigation system that supplies electric power to a traveling motor (for example, Patent Document 1 or Patent Document 2).

  In addition, as a main battery, in a main battery configured by connecting a plurality of secondary batteries in series in order to achieve a high output voltage, variations in the output voltage of each secondary battery caused by repeated charge and discharge It is necessary to suppress the entire deterioration by eliminating as much as possible.

  For example, as a technique for equalizing the output voltages of the respective secondary batteries (hereinafter referred to as cell balance), as shown in FIG. 4, a plurality of secondary batteries 41 (41-1 to 41-1 constituting the main battery 40 are included. 41-n) is connected to a switch 42 and a resistor 43, and each switch 42 is turned on and off in turn, whereby each secondary battery 41 is discharged and consumed by each resistor 43. There is a so-called passive cell balance in which each output voltage is aligned with the lowest output voltage. For example, when the output voltage of the secondary battery 41-2 becomes the lowest after the main battery 40 is used or charged, the switches 42 connected to the secondary batteries 41-1 and 41-3 to 41-n, respectively. Are turned on and off in order to discharge the secondary batteries 41-1 and 41-3 to 41-n in order, respectively, and as shown in FIG. Each output voltage of 41-n is made equal to the output voltage of the secondary battery 41-2.

  In this way, the passive cell balance is a configuration in which the secondary battery is discharged and the discharge energy is consumed by the resistance in order to align the respective output voltages of the respective secondary batteries, so that the discharge energy is wasted. Become.

Japanese Patent Laid-Open No. 10-164709 JP 2008-302852 A

  An object of the present invention is to provide a cell balance device capable of effectively using discharge energy generated during cell balance while suppressing variations in output voltages of a plurality of secondary batteries constituting a main battery. .

  The cell balance device of the present invention includes a main battery including first and second secondary batteries connected in series to each other, a cell balance circuit for discharging the first or second secondary battery, and the first or second battery. An alternating current flows through the primary coil due to intermittent discharge of the second secondary battery and the primary coil and the secondary coil are electromagnetically coupled, and between the secondary coil of the transformer and the auxiliary battery. When the difference between the output voltages of the DC-DC converter provided in the first and second secondary batteries is equal to or greater than a threshold value, the first and second control circuits control the operation of the cell balance circuit. The first or second secondary battery is intermittently discharged so that the higher output voltage of the respective output voltages of the secondary battery is aligned with the lower output voltage, and the operation of the DC-DC converter is controlled. And a control circuit for charging the auxiliary battery voltage outputted from the DC-DC converter by stepping down the voltage applied to the secondary coil by.

  Thereby, the dispersion | variation in each output voltage of each secondary battery of a main battery can be suppressed, and the lifetime of a main battery can be extended. Moreover, since it is the structure which charges an auxiliary machine battery using the discharge current from a secondary battery at the time of cell balance, the discharge energy produced at the time of cell balance can be used effectively.

  The cell balance circuit includes a first resistor and a second resistor connected in series to each other and connected in parallel to the primary coil of the transformer, and between the first secondary battery and the first resistor. And a second switch provided between the second secondary battery and the second resistor, and the control circuit includes the first and second secondary switches. When the difference between the output voltages of the batteries is equal to or greater than the threshold value, the first or second output voltage is set so that the higher output voltage of the output voltages of the first and second secondary batteries matches the lower output voltage. These switches may be configured to be turned on and off.

  ADVANTAGE OF THE INVENTION According to this invention, the discharge energy produced at the time of cell balance can be used effectively, suppressing the dispersion | variation in each output voltage of each secondary battery which comprises the main battery mounted in a vehicle.

It is a figure which shows the cell balance apparatus of embodiment of this invention. It is a figure which shows an example of a battery monitoring cell balance circuit and a DC-DC converter. It is a figure which shows typically an example of the timing chart of ON / OFF of each switch. It is a figure for demonstrating the cell balance of a passive system. It is a figure which shows the change of each output voltage of each secondary battery at the time of the cell balance of a passive system.

FIG. 1 is a diagram showing a cell balance device according to an embodiment of the present invention.
A cell balance device 1 shown in FIG. 1 includes a main battery 2 composed of a plurality of secondary batteries connected in series, a battery monitoring cell balance circuit 3 (cell balance circuit), DC-DC converters 4, 5 , A transformer 6, an auxiliary battery 7, and a battery ECU (Electronic Control Unit) 8 (control circuit). In addition, the cell balance apparatus 1 of this embodiment shall be mounted in vehicles, such as a hybrid vehicle, a plug-in hybrid vehicle, an electric vehicle, or a forklift. Moreover, each secondary battery of the main battery 2 shall be comprised by a lithium ion secondary battery, a nickel-hydrogen secondary rechargeable battery, etc., for example. Moreover, the auxiliary machine battery 7 shall be comprised by lead acid battery, for example.

The main battery 2 supplies power to the traveling motor 10 via the inverter 9 and obtains regenerative power from the traveling motor 10 via the inverter 9.
The auxiliary battery 7 supplies power to the battery ECU 8 via the DC-DC converter 5 or supplies power to the electrical equipment 11. The electrical equipment 11 is an air conditioner, a car navigation system, or the like.

  The battery monitoring cell balance circuit 3 detects each output voltage of each secondary battery of the main battery 2, outputs the output voltage to the battery ECU 8, and at the time of cell balancing, the secondary voltage corresponding to an instruction from the battery ECU 8 Discharge the battery.

  The battery ECU 8 is in a state where the main battery 2 is not being used by the traveling motor 10 such as when the vehicle is parked, and when the ignition signal IG output from the host ECU that controls the entire vehicle is at a low level, the battery monitoring cell balance When the difference between the highest voltage and the lowest voltage among the voltages output from the circuit 3 exceeds a threshold value, the operation of the battery monitoring cell balance circuit 3 is controlled and each secondary battery of the main battery 2 is controlled. The output voltages are equalized with each other (cell balance). At this time, the battery ECU 8 intermittently discharges the secondary battery having a high output voltage so that the output voltages of the secondary batteries of the main battery 2 are aligned with the lowest output voltage. Due to the intermittent discharge of the secondary battery, an alternating current flows through the primary coil of the transformer 6 and the primary coil and the secondary coil of the transformer 6 are electromagnetically coupled. Thereby, substantially the same voltage as that applied to the primary coil of the transformer 6 is also applied to the secondary coil of the transformer 6 during cell balancing.

  Further, the battery ECU 8 controls the operation of the DC-DC converter 4 at the time of cell balance, and steps down the voltage applied to the secondary coil of the transformer 6 to output the auxiliary battery 7 with the voltage output from the DC-DC converter 4. To charge.

  As described above, the cell balance device 1 of the present embodiment can suppress variations in the output voltages of the secondary batteries of the main battery 2 and can extend the life of the main battery 2.

  Moreover, since the cell balance apparatus 1 of this embodiment is the structure which charges the auxiliary battery 7 using the discharge current from each secondary battery of the main battery 2 at the time of cell balance, the discharge energy produced at the time of cell balance Can be used effectively.

  FIG. 2 is a diagram illustrating an example of the battery monitoring cell balance circuit 3 and the DC-DC converter 4. The main battery 2 is configured by n modules 13 (modules 13-1 to 13-n) configured by three battery cells 12 connected in series with each other in series. The number of battery cells 12 constituting one module 13 is not limited to three. Moreover, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG.

  The battery monitoring cell balance circuit 3 shown in FIG. 2 includes n voltage detectors 14 (14-1 to 14-n) for detecting the output voltage of each module 13 and n pieces of the voltage detectors 14 connected to each module 13, respectively. Switch 15 (15-1 (first switch) to 15-n (second switch)) and n resistors 16 (16-1 (first resistor) to 16 connected to each switch 15 respectively) -N (second resistor)). That is, the resistors 16-1 to 16-n are connected in series to each other and are connected in parallel to the primary coil 6-1 of the transformer 6. Also, the resistor 16-1 is connected to the plus terminal of the module 13-1 via the switch 15-1, and the resistor 16-n is connected to the minus terminal of the module 13-n and the ground (for example, the vehicle body). Connected to a virtual ground). Further, a switch 15-2 is provided between the resistor 16-2 and the plus terminal of the module 13-2,..., A switch 15-n between the resistor 16-n and the plus terminal of the module 13-n. Is provided. One end of the primary coil 6-1 of the transformer 6 is connected between the switch 15-1 and the resistor 16-1, and the other end of the primary coil 6-1 is between the resistor 16-n and the ground. It is connected to the.

Voltage detectors 14-1 to 14-n detect voltages V1 to Vn output from modules 13-1 to 13-n, respectively, and output them to battery ECU 8.
When the ignition signal IG is at a low level, the battery ECU 8 determines whether the difference between the highest voltage and the lowest voltage among the voltages V1 to Vn detected by the voltage detectors 14-1 to 14-n is equal to or greater than a threshold value. If it is determined whether or not the difference is equal to or greater than the threshold value, each of the switches 15-1 to 15-n is controlled to be turned on / off so that the other voltage is aligned with the lowest voltage.

  The switches 15-1 to 15-n are configured by switching elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), for example, and are turned on and off by control signals S1 to Sn output from the battery ECU 8. For example, the duty of each of the control signals S1 to Sn when the switch 15 is turned on and off is 50%. Further, the respective frequencies of the control signals S1 to Sn when the switch 15 is turned on and off may be set according to a desired cell balance execution time of each module 13 or the like.

  The battery ECU 8 turns on and off the switches 15 respectively connected to the modules 13 other than the module 13 having the lowest output voltage among the switches 15-1 to 15-n one by one during the cell balance. Each switch 15 other than the switch 15 that is turned on and off is always turned off. Note that the time for turning on and off one switch 15 is until the output voltage of the module 13 connected to the switch 15 reaches the lowest output voltage. As a result, the output voltages of the modules 13-1 to 13-n are equalized.

  For example, when the cell balance is performed, the switch 15-1 is turned on and off, and the other switches 15-2 to 15-n are always turned off. A current flows through the primary coil 6-1 and energy is stored in the primary coil 6-1, and the energy stored in the primary coil 6-1 is released to the ground or the like when the switch 15-1 is turned off. As a result, the module 13-1 is gradually discharged.

  The DC-DC converter 4 shown in FIG. 2 includes a MOSFET 17, a diode 18, a coil 19, and a capacitor 20. That is, one end of the secondary coil 6-2 of the transformer 6 is connected to one end of the capacitor 20 via the MOSFET 17 and the coil 19, and the other end of the secondary coil 6-2 of the transformer 6 is connected to the other end of the capacitor 20. It is connected. The cathode of the diode 18 is connected between the MOSFET 17 and the coil 19, and the anode of the diode 18 is connected to the other end of the capacitor 20. A capacitor 20 is connected in parallel to the auxiliary battery 7. The winding ratio between the primary coil 6-1 and the secondary coil 6-2 is, for example, 1: 1. Further, the MOSFET 17 may be composed of other transistors such as a bipolar transistor. Further, the DC-DC converter 4 is not limited to the configuration shown in FIG.

  The MOSFET 17 is turned on / off by a PWM control signal Sdown output from the battery ECU 8. The battery ECU 8 changes the duty of the PWM control signal Sdown according to the voltage applied to the primary coil 6-1 or the secondary coil 6-2 so that the output voltage of the DC-DC converter 4 becomes constant. Also good.

  When the MOSFET 17 is turned on / off by the PWM control signal Sdown at the time of cell balance, the voltage applied to the secondary coil 6-2 is stepped down to a voltage slightly higher than the voltage of the auxiliary battery 7 by the discharge energy of the module 13, and DC-DC Output from the converter 4. That is, when the MOSFET 17 is turned on, energy from the secondary coil 6-2 is stored in the coil 19, and when the MOSFET 17 is turned off, the diode 18 is turned on by the electromotive force of the coil 19, and a current flows from the diode 18 to the capacitor 20. The DC voltage smoothed by the capacitor 20 is output to the auxiliary battery 7, and the auxiliary battery 7 is charged.

  As described above, the cell balance device 1 according to the present embodiment equalizes the output voltages of the modules 13-1 to 13-n and uses the energy discharged from the module 13 at the time of cell balance to make the auxiliary battery 7 Can be charged.

  FIG. 3 is a diagram schematically illustrating an example of an on / off timing chart of each of the switches 15-1 to 15-n and the MOSFET 17. When the main battery 2 is being used by the traveling motor 10 such as when the vehicle is traveling, and when the ignition signal IG is at a high level or when the voltage of each module 13 is detected, the switches 15-1 to 15-15. It is assumed that −n and MOSFET 17 are off.

  For example, when the ignition signal IG is at a low level, the battery ECU 8 determines that the difference between the highest voltage V1 and the lowest voltage V2 is greater than or equal to a threshold, and each of the modules 13-1, 13-3 to 13-n Consider a case in which the switches 15-1, 15-3 to 15-n are sequentially turned on and off so that the output voltages V1, V3 to Vn are aligned with the output voltage V2 of the module 13-2.

In such a case, the battery ECU 8 turns on and off the switches 15-1 and 15-3 to 15-n in order so that the voltages V1 and V3 to Vn are respectively equal to the voltage V2.
Further, when the switches 15-1 and 15-3 to 15-n are turned on and off, the battery ECU 8 turns on and off the MOSFET 17 by the PWM control signal Sdown to charge the auxiliary battery 7.

  As a result, each of the output voltages of the modules 13-1, 13-3 to 13-n is adjusted to the output voltage of the module 13-2, and the auxiliary machine is used by the discharge energy of the modules 13-1, 13-3 to 13-n The battery 7 can be charged.

DESCRIPTION OF SYMBOLS 1 Cell balance apparatus 2 Main battery 3 Battery monitoring cell balance circuit 4, 5 DC-DC converter 6 Transformer 7 Auxiliary battery 8 Battery ECU
9 Inverter 10 Traveling motor 11 Electrical equipment

Claims (2)

A main battery comprising first and second secondary batteries connected in series with each other;
A cell balance circuit for discharging the first or second secondary battery;
A transformer in which an alternating current flows through a primary coil due to intermittent discharge of the first or second secondary battery, and the primary coil and the secondary coil are electromagnetically coupled;
A DC-DC converter provided between a secondary coil of the transformer and an auxiliary battery;
When the difference between the output voltages of the first and second secondary batteries is equal to or greater than a threshold value, the output voltage of each of the first and second secondary batteries is controlled by controlling the operation of the cell balance circuit. Among these, the first or second secondary battery is intermittently discharged so that the high output voltage is aligned with the low output voltage, and the voltage applied to the secondary coil is controlled by controlling the operation of the DC-DC converter. A control circuit that steps down and charges the auxiliary battery with a voltage output from the DC-DC converter;
A cell balance device comprising: The cell balance device according to claim 1,
The cell balance circuit is provided between the first and second resistors connected in series with each other and connected in parallel to the primary coil of the transformer, and between the first secondary battery and the first resistor. A first switch, and a second switch provided between the second secondary battery and the second resistor,
When the difference between the output voltages of the first and second secondary batteries is equal to or greater than the threshold, the control circuit outputs a higher output voltage among the output voltages of the first and second secondary batteries. A cell balance device, wherein the first or second switch is turned on / off so as to be matched with a low output voltage.