JP7059946B2 - Power control circuit - Google Patents

Description

The present invention relates to a power supply control circuit.

Conventionally, as seen in Patent Document 1, a power supply control circuit including first and second semiconductor switches (specifically, FETs) is known. The first semiconductor switch is provided in the first electric path connecting the positive electrode terminal of the battery and the high potential side of the inverter. The second semiconductor switch is provided in the second electric path connecting the negative electrode terminal of the battery and the low potential side of the inverter.

In this power supply control circuit, the gate voltage of the first semiconductor switch when the first semiconductor switch is switched to the on state is gradually increased after the second semiconductor switch is switched to the on state at the time of its activation. This suppresses the flow of inrush current when precharging from the battery to the capacitor of the inverter.

Japanese Unexamined Patent Publication No. 2018-23179

In the power supply control circuit described in Patent Document 1, since semiconductor switches are provided in each of the first and second electric paths as a configuration for precharging, there is a concern that the configuration of the power supply control circuit may be complicated.

An object of the present invention is to provide a power supply control circuit capable of suppressing an inrush current from flowing during precharging with a simple configuration.

The first invention comprises a semiconductor switch provided in an electric path connecting a positive electrode side of a DC power supply and a high potential side of an electric load having a capacitive component.
A first drive unit connected to the gate of the semiconductor switch and switching the semiconductor switch at the first switching speed by supplying a voltage to the gate.
A second drive unit connected to the gate of the semiconductor switch and switching the semiconductor switch at a second switching speed lower than the first switching speed by supplying a voltage to the gate.
When the precharge process for charging the capacitance component from the DC power supply is performed, the semiconductor switch is switched to the on state by the second drive unit, and after the precharge process is completed, the semiconductor switch is operated by the first drive unit. A control unit for switching is provided.

According to the first invention, when the precharge process is performed, the second drive unit switches the semiconductor switch to the on state, so that the inrush current flowing from the DC power supply to the capacitive component of the electric load can be suppressed. On the other hand, after the precharge process is completed, the switching loss can be reduced by switching the semiconductor switch by the first drive unit.

As described above, according to the first invention, the inrush current at the time of precharging is suppressed by using the semiconductor switch on the electric path connecting the positive side of the DC power supply and the high potential side of the electric load, and also. After the precharge is completed, the DC power supply and the electric load can be electrically connected or disconnected. Therefore, as compared with the configuration described in Patent Document 1, it is possible to suppress the inrush current from flowing during precharging with a simple configuration.

The second invention relates to the first gate path, which is an electric path connecting the output unit of the first drive unit and the gate of the semiconductor switch in the first invention.
A second gate path, which is an electric path connecting the output unit of the second drive unit and the gate of the semiconductor switch, is provided.
The first drive unit outputs a voltage that rises according to the first time constant from the output unit to the first gate path.
The second drive unit outputs a voltage rising from the output unit to the second gate path according to a second time constant larger than the first time constant.
A direction provided in the second gate path, which allows current to flow in the direction from the output unit of the second drive unit to the gate of the semiconductor switch, and from the gate to the output unit of the second drive unit. It is equipped with a rectifying element that blocks the flow of current.

The current output from the output unit of the first drive unit flows into the second drive unit via the first and second gate paths and the output unit of the second drive unit, and the gate voltage of the semiconductor switch is quickly raised. May not be possible. In this case, there is a concern that the effect of reducing the switching loss by the first drive unit is reduced.

Therefore, in the second invention, a rectifying element is provided in the second gate path. As a result, it is possible to prevent the current from flowing into the second drive unit and prevent the effect of reducing the switching loss when the semiconductor switch is switched by the first drive unit.

As the rectifying element, for example, as in the third invention, a diode of a passive element can be used. As a result, it is possible to prevent the current from flowing into the second drive unit with a simple configuration.

The overall block diagram of the power supply system which concerns on 1st Embodiment. A time chart showing the transition of the output voltage of each drive unit. The figure which shows the calculation and the actual measurement result which defines the relationship between the time constant of a drive part and the peak value of an inrush current. A time chart showing that the peak value of the inrush current differs depending on whether the time constant is small or large. The figure which shows a part of the power-source system which concerns on 2nd Embodiment. A time chart showing the transition of the output voltage of each drive unit.

<First Embodiment>
Hereinafter, the first embodiment in which the power supply control circuit according to the present invention is embodied will be described with reference to the drawings. The power supply control circuit of this embodiment is mounted on the vehicle.

As shown in FIG. 1, the power supply system includes a lead storage battery 11 as a first storage battery and a lithium ion storage battery 12 as a second storage battery. Each storage battery 11 and 12 can be charged by an ISG (Integrated Starter Generator) 13 that functions as a generator. A lead storage battery 11 and a lithium ion storage battery 12 are connected in parallel with the ISG 13. In this embodiment, the ISG 13 corresponds to an electrical load.

The lead storage battery 11 is a well-known general-purpose storage battery. On the other hand, the lithium ion storage battery 12 is a high-density storage battery having a smaller power loss in charging / discharging, a higher output density, and a higher energy density than the lead storage battery 11. The lithium ion storage battery 12 is preferably a storage battery having higher energy efficiency during charging / discharging than the lead storage battery 11. Further, the lithium ion storage battery 12 is configured as an assembled battery each having a plurality of cell cells. In the present embodiment, the rated voltages of the storage batteries 11 and 12 are all the same, for example, 12V.

The lithium ion storage battery 12 is housed in a storage case and is configured as a battery unit U integrated with a substrate. The battery unit U has first and second output terminals P1 and P2. The positive electrode terminal of the lead storage battery 11 is connected to the first output terminal P1, and the ground is connected to the negative electrode terminal of the lead storage battery 11. The high potential side terminal of ISG13 is connected to the second output terminal P2. The ISG 13 includes a smoothing capacitor 14 for a passive element as a capacitive component, a rotary electric machine (not shown), and an ECU 15 for controlling the rotary electric machine.

Next, the battery unit U constituting the power supply system will be described. The battery unit U is connected to the first electric path L1 connecting the output terminals P1 and P2, the connection point N on the first electric path L1 and the positive electrode terminal of the lithium ion storage battery 12 as the electric path in the unit. A second electric path L2 is provided. A ground is connected to the negative electrode terminal of the lithium ion storage battery 12.

The battery unit U includes a first switch SW1 provided on the first electric path L1 and a second switch SW2 provided on the second electric path L2. The first switch SW1 is composed of a pair of N-channel MOSFETs, a first A switch 21A and a first B switch 21B. The first output terminal P1 is connected to the drain of the first A switch 21A, and the source of the first B switch 21B is connected to the source of the first A switch 21A. A connection point N is connected to the drain of the first B switch 21B. As a result, the body diodes of the pair of MOSFETs are connected in series so as to face each other in opposite directions.

A pair of N-channel MOSFETs in which drains are connected to each other may be used as the first switch SW1. As a result, the cathodes of the body diodes are connected to each other.

The first A switch 21A corresponds to a first control switch that allows current to flow in the direction from the lead storage battery 11 to the smoothing capacitor 14 only when it is turned on. The first B switch 21B corresponds to a second control switch that blocks the flow of current in the direction from the smoothing capacitor 14 to the lead storage battery 11 only when it is turned off.

The second switch SW2 is composed of a pair of N-channel MOSFETs, a second A switch 22A and a second B switch 22B. A connection point N is connected to the drain of the second A switch 22A, and the source of the second B switch 22B is connected to the source of the second A switch 22A. The positive electrode terminal of the lithium ion storage battery 12 is connected to the drain of the second B switch 22B. In FIG. 1, the description of the resistor, the Zener diode, and the capacitor connected between the gate and the source of the first switch SW1 is omitted for the second switch SW2.

The battery unit U includes first to fifth drive units 31 to 35. The first drive unit 31 includes first to sixth resistors 31a to 31f, a constant voltage power supply 31 g, and first to third drive switches 31h to 31j. The first and third drive switches 31h and 31j are NPN type bipolar transistors, and the second drive switch 31i is a PNP type bipolar transistor.

A signal from the control unit 40 is input to the first end of the first resistor 31a. The base of the first drive switch 31h and the first end of the second resistor 31b are connected to the second end of the first resistor 31a. The emitter of the first drive switch 31h and the ground are connected to the second end of the second resistor 31b.

The first end of the third resistor 31c is connected to the collector of the first drive switch 31h, and the base of the second drive switch 31i and the fourth resistor 31d are connected to the second end of the third resistor 31c. It is connected to the first end. A constant voltage power supply 31g is connected to the second end of the fourth resistor 31d and the emitter of the second drive switch 31i.

The collector of the second drive switch 31i is connected to the first end of each of the fifth resistor 31e and the sixth resistor 31f. The base of the third drive switch 31j is connected to the second end of the fifth resistor 31e. The second end of the sixth resistor 31f is connected to the collector of the third drive switch 31j. The gate of the first A switch 21A is connected to the emitter of the third drive switch 31j (corresponding to the output unit of the first drive unit 31) via the first gate path G1. The first gate resistor 41 is provided in the first gate path G1.

The second drive unit 32 includes first to sixth resistors 32a to 32f, a constant voltage power supply 32 g, first to third drive switches 32h to 32j, and a capacitor 32k. Hereinafter, only the main differences between the second drive unit 32 and the first drive unit 31 will be described. A ground is connected to the base of the third drive switch 32j via a capacitor 32k. The gate of the first A switch 21A is connected to the emitter of the third drive switch 32j (corresponding to the output unit of the second drive unit 32) via the second gate path G2. A diode 50 is provided in the second gate path G2. Specifically, the anode of the diode 50 faces the second drive unit 32 side, and the cathode faces the gate side of the first A switch 21A.

In FIG. 1, one end of the second gate path G2 is connected to the first A switch 21A side of the first gate resistor 41 in the first gate path G1, but the configuration is not limited to this. For example, one end of the second gate path G2 may be directly connected to the gate of the first A switch 21A. Even in this case, the second gate path G2 is electrically connected to the first gate path G1 via the gate of the first A switch 21A.

In the present embodiment, the third to fifth drive units 33 to 35 have the same configuration as the first drive unit 31. Therefore, detailed description of the third to fifth drive units 33 to 35 will be omitted.

The gate of the first B switch 21B is connected to the output unit of the third drive unit 33 via the third gate path G3. A third gate resistor 43 is provided in the third gate path G3.

The gate of the second A switch 22A is connected to the output unit of the fourth drive unit 34 via the fourth gate path G4. A fourth gate resistor 44 is provided in the fourth gate path G4. The gate of the second B switch 22B is connected to the output unit of the fifth drive unit 35 via the fifth gate path G5. A fifth gate resistor 45 is provided in the fifth gate path G5.

The battery unit U includes a control unit 40. The control unit 40 is composed of a microcomputer including a CPU, a ROM, a RAM, an input / output interface, and the like. The control unit 40 sets each switch 21A, 21B, 22A, 22B via the first to fifth drive units 31 to 35 based on the storage state of each storage battery 11 and 12 and a command from a higher-level control device (not shown). Control on / off.

For example, the control unit 40 selectively uses the lead storage battery 11 and the lithium ion storage battery 12 to perform charging and discharging. More specifically, a voltage sensor for detecting the terminal voltage of the lead storage battery 11 is connected to the energization path of the lead storage battery 11, and the terminal voltage of the lithium ion storage battery 12 is detected in the energization path of the lithium ion storage battery 12. The voltage sensor is connected. The control unit 40 calculates the SOC (residual capacity: State Of Charge) of each of the storage batteries 11 and 12 based on the terminal voltage acquired from these voltage sensors. The control unit 40 controls the on / off of the first switch SW1 and the second switch SW2 so that the calculated SOC is kept within a predetermined range of use, and controls the charging and discharging of the storage batteries 11 and 12.

Further, the control unit 40 executes the precharge process when the power supply system is started. The precharge process is a process of charging the smoothing capacitor 14 from the lead storage battery 11 via the first electric path L1. In this embodiment, the second switch SW2 is maintained in the off state during the precharge process.

The precharge process will be described with reference to FIG. FIG. 2A shows the transition of the output voltage from the first drive unit 31 to the first gate path G1, and FIG. 2B shows the transition of the output voltage from the second drive unit 32 to the second gate path G2. The transition is shown, and FIG. 2C shows the transition of the output voltage from the third drive unit 33 to the third gate path G3. In FIG. 2, VP on the vertical axis indicates the output voltage of the constant voltage power supply of each drive unit. For example, the VP in the case of the first drive unit 31 indicates the output voltage of the constant voltage power supply 31 g. In this embodiment, the output voltage of each drive unit is set higher than the output voltage of each of the storage batteries 11 and 12. As a result, an appropriate voltage can be applied to the gate of each switch.

At time t1, the control unit 40 outputs an on command to the third drive unit 33. As a result, the output voltage of the third drive unit 33 rises sharply to VP according to the first time constant τ1. As a result, the first B switch 21B is switched to the ON state at the first switching speed. By switching the first B switch 21B to the on state before the timing of switching the first A switch 21A to the on state, it is possible to prevent the current from the lead storage battery 11 from flowing to the body diode of the first B switch 21B. As a result, heat generation of the first B switch 21B is suppressed.

At time t2, an on command is output from the control unit 40 to the second drive unit 32 (specifically, the first resistor 32a side of the second drive unit 32). As a result, the voltage supplied from the second drive unit 32 to the gate of the first A switch 21A begins to gradually increase from 0 according to the second time constant τ2 (> τ1). After that, at time t3, the output voltage of the second drive unit 32 reaches VP. As a result, the first A switch 21A is switched to the ON state at a second switching speed lower than the first switching speed.

After that, at time t4, the control unit 40 determines that the precharge process is completed. As a result, the control unit 40 outputs an on command to the first drive unit 31 (specifically, the first resistor 31a side of the first drive unit 31). As a result, the output voltage of the first drive unit 31 rises sharply to VP according to the first time constant τ1. As a result, the first A switch 21A is switched to the ON state at the first switching speed. After that, the control unit 40 outputs an off command to the second drive unit 32. As a result, the first A switch 21A is switched to the off state.

The control unit 40 may detect, for example, the potential difference of the first switch SW1 and determine that the precharge process is completed when it is determined that the detected potential difference is equal to or less than a predetermined value.

Subsequently, the time constant will be described with reference to FIGS. 3 and 4.

The solid line in FIG. 3 shows the calculation result of the peak value of the inrush current generated when the second time constant τ2 is changed. The larger the second time constant τ2, the smaller the peak value of the inrush current. In FIG. 2, three actual measurement results of the peak value of the inrush current are plotted.

When the resistance value of the resistor 32e of the second drive unit 32 is R and the capacitance of the capacitor 32k is C, it can be expressed as "τ2 = R × C". Here, for example, when it is desired to set the peak value of the inrush current to 5A, according to the result of FIG. 3, R and C may be set so that τ2 is 0.1 seconds. The second time constant τ2 is preferably set between 0.126 and 0.286 seconds, and more preferably 0.2 seconds or more. Further, it is desirable that the first time constant τ1 is 0.02 or less.

FIG. 4 shows the actual measurement results of the transition of the supply voltage to the ISG13, the gate voltage Vgs of the first A switch 21A, the current flowing through the first A switch 21A, and the difference ΔV between the lead storage battery 11 and the supply voltage to the ISG13. FIG. 4A shows a case where the second time constant τ2 is set to 0.02 seconds, and FIG. 4B shows a case where the second time constant τ2 is set to 0.1 seconds. In the example shown in FIG. 4A, since the second time constant τ2 is smaller than that in the example shown in FIG. 4B, the peak value of the inrush current is large.

According to the present embodiment described in detail above, the following effects can be obtained.

When performing the precharge process, the second drive unit 32 switches the first A switch 21A to the ON state, so that the inrush current flowing from the lead storage battery 11 to the smoothing capacitor 14 can be suppressed. On the other hand, after the precharge process is completed, the switching loss can be reduced by switching the on / off of the first A switch 21A by the first drive unit 31.

As described above, according to the present embodiment, the first A switch 21A on the first electric path L1 is used to suppress the inrush current at the time of precharging, and the lead storage battery 11 and the smoothing capacitor 14 after the precharging is completed. Can be electrically connected or disconnected from and to. As a result, it is possible to suppress the inrush current from flowing during precharging with a simple configuration as compared with the configuration described in Patent Document 1.

Further, according to the present embodiment, when the first drive unit 31 fails, the second drive unit 32 can switch the first A switch 21A after the precharge process is completed. As a result, the charge and discharge control of the storage batteries 11 and 12 can be continued so that the SOC of the storage batteries 11 and 12 is kept within a predetermined range of use.

The current output from the first drive unit 31 flows into the capacitor 32k or the like in the second drive unit 32 via the first and second gate paths G1 and G2, and the gate voltage of the first A switch 21A is quickly set. It may not be possible to raise it. In this case, there is a concern that the effect of reducing the switching loss by the first drive unit 31 after the completion of precharging is reduced.

Therefore, a diode 50 is provided in the second gate path G2. As a result, it is possible to prevent the current from flowing into the second drive unit 32 and prevent the effect of reducing the switching loss when the first drive unit 31 switches the first A switch 21A. Further, by using the diode 50 of the passive element, it is possible to realize the prevention of the current from flowing into the second drive unit 32 with a simple configuration.

When performing the precharge process, the control unit 40 switches the first B switch 21B to the on state before the first A switch 21A is switched to the on state. As a result, it is possible to prevent the current from the lead storage battery 11 from flowing through the body diode of the first B switch 21B, and it is possible to suitably suppress the heat generation of the first B switch 21B due to the precharge process.

<Modified example of the first embodiment>
As shown in FIG. 2, instead of the configuration in which the first B switch 21B is switched to the on state before the first A switch 21A, the first B switch 21B is switched at the same timing as the switching timing of the first A switch 21A to the on state. You may switch to the on state.

<Second Embodiment>
Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, as shown in FIG. 5, the configuration inside the battery unit U is changed. In FIG. 5, the same configurations as those shown in FIG. 1 above are designated by the same reference numerals for convenience. Further, in FIG. 5, a part of the configuration shown in FIG. 1 is not shown.

As shown in FIG. 5, a third switch SW3 is connected in parallel to the first switch SW1. The third switch SW3 is composed of a pair of N-channel MOSFETs, a third A switch 23A and a third B switch 23B. The first output terminal P1 is connected to the drain of the third A switch 23A, and the source of the third B switch 23B is connected to the source of the third A switch 23A. A connection point N is connected to the drain of the third B switch 23B. The configuration in which the third switch SW3 is connected in parallel to the second switch SW2 is to increase the current flowing during the precharge process. In FIG. 5, the description of the resistor, the Zener diode, and the capacitor connected between the gate and the source is omitted for the first and third switches SW3.

The battery unit U includes a sixth drive unit 36 and a seventh drive unit 37. The sixth drive unit 36 and the seventh drive unit 37 have the same configuration as the first drive unit 31. Therefore, detailed description of the sixth drive unit 36 and the seventh drive unit 37 will be omitted.

The gate of the third A switch 23A is connected to the output unit of the sixth drive unit 36 via the sixth gate path G6. A sixth gate resistor 46 is provided in the sixth gate path G6. The gate of the third B switch 23B is connected to the output unit of the seventh drive unit 37 via the seventh gate path G7. A seventh gate resistor 47 is provided in the seventh gate path G7. The control unit 40 has the switches 21A, 21B, 22A, 22B, via the first to seventh drive units 31 to 37, based on the storage state of the storage batteries 11 and 12 and commands from a higher-level control device (not shown). On / off control of 23A and 23B is performed.

The precharge process of this embodiment will be described with reference to FIG. 6 (a) to 6 (c) correspond to the above-mentioned FIGS. 2 (a) and 2 (c). 6 (d) and 6 (e) show the transition of the output voltage from the 6th and 7th drive units 36 and 37 to the 6th and 7th gate paths G6 and G7.

In FIG. 6, only the main differences from FIG. 2 above will be described. T1 to t5 in FIG. 6 correspond to t1 to t5 in FIG. At time t4, the control unit 40 outputs an on command to the sixth and seventh drive units 36 and 37. As a result, the voltage supplied from the sixth and seventh drive units 36 and 37 to the gates of the third A and B switches 23A and 23B rises sharply to VP according to the first time constant τ1. As a result, the third A and B switches 23A and 23B are switched to the ON state at the first switching speed.

In the present embodiment described above, the time constant is changed only on the first switch SW1 side of the first and third switches SW1 and SW3. As a result, it is possible to suitably avoid the complexity of the power supply control circuit while increasing the current flowing during the precharge process. As a result, the cost of the power supply control circuit can be reduced.

As in the first embodiment, when the first drive unit 31 fails, the second drive unit 32 can switch the first A switch 21A.

<Other embodiments>
In addition, each of the above-mentioned embodiments may be changed and carried out as follows.

The diode 50 may not be provided in the second gate path G2. In this case, it is desirable that the output voltage of the second drive unit 32 can be secured to such an extent that the gate of the first A switch 21A can be properly charged.

-The rectifying element is not limited to a diode as a passive element, but may be, for example, a switch as an active element. In this case, the control unit 40 may maintain this switch in the on state until the time t4 in FIG. 2 and switch it to the off state at the time t4.

-The electrical load is not limited to ISG13. As long as it is an electric load having a capacitive component (capacitor), it may be, for example, a seat heater, a heater for a defroster of a rear window, a headlight, a wiper of a front window, a blower fan of an air conditioner, or the like.

11 ... Lead-acid battery, 13 ... ISG, 14 ... Smoothing capacitor, 31 ... First drive unit, 32 ... Second drive unit, 40 ... Control unit, SW1 ... First semiconductor switch.

Claims (5)

A semiconductor switch (21A) provided in the electric path (L1) connecting the positive electrode side of the DC power supply (11) and the high potential side of the electric load (13) having the capacitance component (14).
A first drive unit (31) connected to the gate of the semiconductor switch and switching the semiconductor switch at the first switching speed by supplying a voltage to the gate.
A second drive unit (32) connected to the gate of the semiconductor switch and switching the semiconductor switch at a second switching speed lower than the first switching speed by supplying a voltage to the gate.
When the precharge process for charging the capacitance component from the DC power supply is performed, the semiconductor switch is switched to the on state by the second drive unit, and after the precharge process is completed, the semiconductor switch is operated by the first drive unit. A power supply control circuit including a control unit (40) for switching. The first gate path (G1), which is an electric path connecting the output unit of the first drive unit and the gate of the semiconductor switch,
A second gate path (G2), which is an electric path connecting the output unit of the second drive unit and the gate of the semiconductor switch, is provided.
The first drive unit outputs a voltage that rises according to the first time constant from the output unit to the first gate path.
The second drive unit outputs a voltage rising from the output unit to the second gate path according to a second time constant larger than the first time constant.
A direction provided in the second gate path, which allows current to flow in the direction from the output unit of the second drive unit to the gate of the semiconductor switch, and from the gate to the output unit of the second drive unit. The power supply control circuit according to claim 1, further comprising a rectifying element (50) that blocks the flow of current. The power supply control circuit according to claim 2, wherein the rectifying element is a diode. The second drive unit is
A switch (32j) for electrically connecting or disconnecting the output unit and the power supply (32g), and
The power supply control circuit according to claim 2 or 3, further comprising a resistor (32e) and a series connection of a capacitor (32k) for increasing the voltage supplied to the control terminal of the switch according to the second time constant. The semiconductor switch is a first control switch having a body diode and allowing current to flow in a direction from the DC power supply to the capacitive component only when it is turned on.
A second control switch (21B) having a body diode, blocking the flow of current in the direction from the capacitive component to the DC power supply only when turned off, and connected in series with the first control switch,
A third drive unit (33) connected to the gate of the second control switch and switching the second control switch at a switching speed higher than the first switching speed by supplying a voltage to the gate. Prepare,
The first drive unit is connected to the gate of the first control switch, and by supplying a voltage to the gate, the first control switch is switched at the first switching speed.
The second drive unit is connected to the gate of the first control switch, and by supplying a voltage to the gate, the first control switch is switched at the second switching speed.
When the precharge process is performed, the control unit supplies a voltage from the third drive unit to the gate of the second control switch before the timing when the first control switch is switched to the on state by the second drive unit. The power supply control circuit according to any one of claims 1 to 4, wherein the second control switch is switched to an on state.

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