JP6375929B2 - Vehicle power supply - Google Patents

Description

  The present invention relates to a power supply device for a vehicle that can cut off a current when a short circuit abnormality occurs in the vehicle.

  In a vehicle, a high-density storage battery (second storage battery) such as a lithium ion storage battery may be mounted for the purpose of assisting a lead storage battery. For example, in patent document 1, a lead storage battery and a 2nd storage battery are connected in parallel via a switch part. And the electric power supply using a lead storage battery and the electric power supply using a 2nd storage battery are switched by switching the conduction | electrical_connection and interruption | blocking of a switch part (refer patent document 1).

  By the way, an inductance component exists in various electric equipment and electronic equipment connected to each of these storage batteries, or in a connection path. Therefore, there is a concern that a surge voltage may be generated due to an inductance component when the switch unit is shut off. The surge voltage tends to increase as the cutoff speed of the switch portion increases. Therefore, in order to protect various devices and the like from the surge voltage, the cut-off speed of the switch unit is suppressed.

JP 2004-618159 A

  However, if a short circuit abnormality occurs and the switching speed of the switch unit is limited, there may be a disadvantage associated with the time required to shut off the overcurrent.

  The present invention has been made in view of the above, and it is a primary object of the present invention to provide a vehicular power supply device that can appropriately perform current interruption when a short circuit abnormality occurs.

  The present invention is provided in a storage battery (12, 13) connected to a generator (14) and a connection path (L1, L2) for electrically connecting the generator and the storage battery, and the generator and the And a semiconductor switch (16, 17) that switches between conduction and interruption with the storage battery, and is applied to a power supply system for a vehicle in which the storage battery is charged by power generation of the generator, and the generator and the storage battery Short-circuit abnormality determining means for determining presence or absence of short-circuit abnormality in the connection path, cutoff speed setting means for setting a cutoff speed when shutting off the semiconductor switch based on the determination result of presence or absence of short-circuit abnormality, and the cutoff speed And a shutoff control means for shutting off the semiconductor switch at a shutoff speed set by a setting means.

  According to the present invention, since the shutoff speed for shutting off the semiconductor switch is set according to the presence / absence of a short circuit abnormality in the connection path between the generator and the storage battery, the semiconductor switch is appropriately set according to the presence / absence of the short circuit abnormality. Can be blocked.

The figure which shows the electrical constitution of a power supply system. The figure which shows the electric constitution of a control part. The flowchart which shows the procedure of the interruption | blocking process. The figure which shows the example of execution of the interruption | blocking process. The figure which shows the example of execution of the interruption | blocking process.

  First, prior to description of a specific configuration of a battery unit, an outline of a power supply system to which the battery unit is applied will be described with reference to FIG.

  As shown in FIG. 1, the power supply system includes a lead storage battery 12, a lithium ion storage battery 13, a rotating machine 14 that is a motor generator, an electrical load 15, switches 16 and 17, a current sensor 18, and a control unit 20. Among these, the lithium ion storage battery 13, the switches 16 and 17, the current sensor 18, and the control unit 20 are integrated by being accommodated in a housing (accommodating case) and configured as a battery unit 10. The control unit 20 switches between conduction (ON) and interruption (OFF) of the switches 16 and 17, thereby controlling charging and discharging of the storage batteries 101 and 102.

  The lead storage battery 12 is a well-known general-purpose storage battery. On the other hand, the lithium ion storage battery 13 is a high-density storage battery with less power loss in charge / discharge and higher output density and energy density than the lead storage battery 12. The lithium ion storage battery 13 is constituted by an assembled battery formed by connecting a plurality of battery cells in series.

  In the battery unit 10, terminals P1 and P2 are provided as power input / output terminals. A lead storage battery 12 and an electric load 15 are connected to the terminal P1. A rotating machine 14 is connected to the terminal P2. A switch 16 is provided in the connection path L1 that connects the terminals P1 and P2. A switch 17 is provided in the connection path L2 that connects the connection point N1 on the connection path L1 and the lithium ion storage battery 13.

  A current sensor 18 that detects a current flowing through the lithium ion storage battery 13 is connected between the switches 16 and 17 (between the connection point N1 and the switch 17). The current sensor 18 may be, for example, one that uses a shunt resistor or one that magnetically detects using a Hall element.

  The electric load 15 is a general electric load such as a headlight mounted on a vehicle, a wiper such as a front windshield, a blower fan of an air conditioner, and a defroster heater of a rear windshield.

  The rotating machine 14 has a power generation function for generating power by rotating the crankshaft of the engine. The electric power generated by the rotating machine 14 is supplied to the electric load 15 and also supplied to the lead storage battery 12 and the lithium ion storage battery 13. The amount of discharge from each storage battery 12, 13 to the rotating machine 14 and the electrical load 15 and the amount of charge from the rotating machine 14 to each storage battery 12, 13 are overdischarged by the SOC (State of charge) of each storage battery 12, 13.・ It is controlled so as to be within an appropriate range that does not cause overcharge.

  In FIG. 2, each of the switches 16 and 17 is a MOSFET (semiconductor switch) and is connected in series so that the polarities of the parasitic diodes of the MOSFETs are opposite to each other. Therefore, when the switches 16 and 17 are cut off, the current flowing between the switches 16 and 17 is cut off by the parasitic diode.

  The control unit 20 includes an MPU 121, a drive circuit 122a connected to the switch 16, and a drive circuit 122b connected to the switch 17. The MPU 121 is configured by a known microcomputer including a CPU, a ROM, a RAM, and the like. By adjusting the signal levels of the drive circuits 122a and 122b based on command signals from a host ECU (not shown), Switches between conduction and interruption of the switches 16 and 17.

  For example, when the switch 16 (17) is turned on, the drive circuit 122a (122b) is set to the high level. When the switch 16 (17) is cut off, the drive circuit 122a (122b) is set to a low level.

  Incidentally, an inductance component exists in each electric / electronic device constituting the battery unit and a connection path connected to each device. Therefore, there is a concern that a surge voltage is generated when the switches 16 and 17 are cut off. The surge voltage tends to increase as the breaking speed increases when the switches 16 and 17 are turned off. Therefore, when the switches 16 and 17 are shut off, various devices and the like are protected from surge voltage by suppressing the shut-off speed.

  However, when a short circuit abnormality occurs in the power supply path (for example, the connection path L2) of the lithium ion storage battery 13, an overcurrent is generated, which may cause an influence. At this time, if the cut-off speed of the switches 16 and 17 is limited, inconvenience occurs due to the time required until the overcurrent is cut off.

  Therefore, in the present embodiment, a shut-off circuit for shutting off the switches 16 and 17 at different shut-off speeds is provided between the switch 16 and the drive circuit 122a and between the switch 17 and the drive circuit 122b.

  Next, the configuration of the cutoff circuit will be described in detail. Here, for the sake of simplification of description, a cutoff circuit of the switch 17 will be described. The cut-off circuit of the switch 16 has the same configuration as the cut-off circuit of the switch 17, and thus detailed description thereof is omitted.

  As illustrated, a resistor R1 is connected between the gate which is an input terminal of the switch 17 and the drive circuit 122b. A capacitance C1 is connected between the gate and source, which is between the input and output terminals of the switch 17. The resistor R1 and the capacitance C1 constitute a first cutoff circuit that shuts off the switch 17 with a time constant τ1 = C1 · R1 (cutoff speed V1).

  A resistor R2 having a resistance value larger than that of the resistor R1 is connected to the gate of the switch 17 (R1 <R2). The resistor R2 is connected to a switch 113 that can be switched between conduction and interruption based on a command signal from the MPU 121. And the 2nd interruption | blocking circuit which interrupts | blocks the switch 17 with time constant (tau) 2 (breaking speed V2) smaller than time constant (tau) 1 is comprised by capacitance C1, resistor R1, R2.

  When the short circuit abnormality has not occurred, the MPU 121 suppresses the generation of the surge voltage by shutting off the switch 17 at the shutoff speed V1 using the first shutoff circuit. On the other hand, when a short circuit abnormality occurs, the MPU 121 protects the power supply system from overcurrent by shutting off the switch 17 at the shutoff speed V2 (> V1) using the second shutoff circuit. The cutoff speed V2 is set to a speed at which the switches 16 and 17 are not damaged by the surge voltage in consideration of the withstand voltage of the switches 16 and 17.

  Next, the procedure of the switching process of the switch 17 by the MPU 121 will be described with reference to FIG. The switch 16 has the same processing procedure as that of the switch 17 and therefore will not be described in detail.

  First, it is determined whether or not the switch 17 is conductive (S11). In this processing, an affirmative determination is made when the drive circuit 122b is at a high level, and a negative determination is made when the drive circuit 122b is at a low level. If an affirmative determination is made in S11, it is determined whether or not the switch 17 is switched off (S12). This process is determined based on a command signal from a host ECU (not shown). The host ECU outputs a command signal for conducting and shutting off based on the normal operation of the switch 17 and outputs a command signal for forcibly shutting off the switch 17 when a short circuit abnormality of the switch 17 occurs.

  If it is determined in S12 that the switch 17 is to be shut off, it is determined whether or not the short circuit abnormality determination flag is on (S13). The short circuit abnormality determination flag is turned off when the current detection value I is less than the predetermined threshold Ith, and turned on when the current detection value I is equal to or greater than the predetermined threshold Ith.

  When the short circuit abnormality determination flag is off, the drive circuit 122b is switched to a low level with the switch 113 turned off (S14). At this time, since the switch 113 is off, the time constant τ1 is set by the first cutoff circuit. Thus, the switch 17 is turned off. If the short circuit abnormality determination flag is on, the drive circuit 112b is switched to a low level with the switch 113 turned on (S15). At this time, since the switch 113 is on, the time constant τ2 is set by the second cutoff circuit. Thus, the switch 17 is turned off.

  Next, an execution example of the above processing will be described with reference to FIGS. FIG. 4 is an example of a shut-off process in a normal state where no short circuit abnormality has occurred. FIG. 5 is an example of a shut-off process when a short circuit abnormality occurs. 4 and 5, A is the output signal of the drive circuit 122b, B is the conduction / cutoff state of the switch 113, C is the voltage of the connection path L1, D is the current of the connection path L1, and S is the switching loss. Show. The following processing is repeatedly performed by the control unit 20 at a predetermined cycle. 4 and 5 exemplify the switching operation of the switch 17.

  In FIG. 4, when the switch 17 is switched from conduction to cutoff at time t1, the switch 17 is cut off with the time constant τ1 of the first cutoff circuit because the detected current value I <Ith. In this case, since the voltage of the connection path L1 is cut off relatively slowly over the period ΔT1, the surge voltage is suppressed.

  In FIG. 5, at time t10, when an overcurrent state is established where the current detection value I> Ith, the switch 17 is forcibly cut off based on a command signal from an ECU (not shown). At this time, since I> Ith, the switch 17 is cut off with the time constant τ2 of the second cutoff circuit. In this case, the switch 17 is cut off at a relatively high speed in a period ΔT2 (<ΔT1) shorter than the period ΔT1. Therefore, in this case, it is possible to suppress the loss due to the overcurrent as compared with the case where the switch 17 is shut off with the time constant τ1.

  According to the above, the following excellent effects are exhibited.

  -In the vehicle power supply system, since the shutoff speed when shutting down the semiconductor switch is set according to the presence or absence of a short circuit abnormality in the connection path between the generator and the storage battery, the semiconductor switch is set according to the presence or absence of the short circuit abnormality. It can be blocked properly.

  -The interruption | blocking speed | rate of a semiconductor switch can be switched based on the time constant set from the resistor and capacitance component which were connected to the semiconductor switch.

  -The presence / absence of a short circuit abnormality can be determined based on the detection result of the current in the connection path.

  The present invention is not limited to the description of the above embodiment, and may be implemented as follows. In the following description, the same components as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the above description, an example in which a cutoff circuit is provided in each of the two switches 16 and 17 is shown. However, a cutoff circuit may be provided only in the switch 17 of the lithium ion storage battery 13.

  In the above description, the switches 16 and 17 are provided on the lead storage battery 12 side and the lithium ion storage battery 13 side, respectively, but at least one switch may be provided on the connection paths L1 and L2.

  In the above description, the example in which the cutoff circuit is provided in the battery system including the two secondary batteries of the lead storage battery 12 and the lithium ion storage battery 13 has been described. However, when at least one high-density storage battery is provided in the battery system, Configuration can be applied.

  The current threshold Ith for determining a short circuit abnormality may be variably set according to the voltage of the lithium ion storage battery 13 (open circuit voltage OCV). That is, as the voltage of the lithium ion storage battery 13 decreases, the magnitude of overcurrent that flows when a short-circuit abnormality occurs tends to decrease, so the threshold value Ith is set to a smaller value. In this case, the determination accuracy of the short circuit abnormality can be increased according to the state of charge of the lithium ion storage battery 13.

  -In the above, the example which switches the interruption | blocking speed of switch 16 (17) by switching the resistor electrically connected with respect to switch 16 (17) was shown. In addition to this, by adopting a configuration in which the resistance value of the resistor connected to the switch 16 (17) is variably set, the time constant τ (cutoff speed) when the switch 16 (17) is cut off is switched. May be.

  DESCRIPTION OF SYMBOLS 12 ... Lead storage battery, 13 ... Lithium ion storage battery, 14 ... Rotating machine, 16 ... Switch, 17 ... Switch, 20 ... Control part.

Claims (4)

A storage battery (12, 13) connected to a generator (14);
A semiconductor switch (16, 17) that is provided in a connection path (L1, L2) for electrically connecting the generator and the storage battery, and switches between conduction and disconnection between the generator and the storage battery; Applied to a power supply system for a vehicle in which the storage battery is charged by power generation by a generator,
A short circuit abnormality determining means for determining presence or absence of a short circuit abnormality in the connection path between the generator and the storage battery;
Based on the determination result of the presence or absence of the short circuit abnormality, a shutoff speed setting means for setting a shutoff speed when shutting down the semiconductor switch,
Shut-off control means for shutting off the semiconductor switch at the shut-off speed set by the shut-off speed setting means;
Equipped with a,
The shut-off speed setting means includes
When it is determined that there is no short circuit abnormality, the semiconductor switch is shut off at a first shut-off speed (V1) that suppresses generation of a surge voltage when the semiconductor switch is shut off,
When it is determined that the short circuit abnormality is present, the semiconductor switch is shut off at a second shutoff speed (V2) that is greater than the first shutoff speed and that does not damage the semiconductor switch due to the surge voltage. Vehicle power supply device. The cutoff speed setting means includes a variable resistance means for changing the resistance of a resistor connected to the input terminal of the semiconductor switch,
The vehicle power supply device according to claim 1, wherein the cutoff speed is set based on a time constant determined by a resistance value and a capacitance component of the resistor. The storage battery is electrically connected in parallel to the lead storage battery capable of charging the power charged by the generator, and is capable of charging the power of the generator, and the output density compared to the lead storage battery Or a second storage battery having a high energy density,
The vehicle power supply device according to claim 1, wherein the semiconductor switch is electrically connected between the lead storage battery and the second storage battery. Current detection means (18) for detecting the current of the connection path;
The vehicle power supply device according to any one of claims 1 to 3, wherein the short-circuit abnormality determining unit determines presence or absence of the short-circuit abnormality based on a current detection value by the current detection unit.

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