JP2016093004A - Switch box - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switch box for surely detecting an open failure or a short circuit failure in each of switching transistors connected in parallel.SOLUTION: The switch box includes: a pair of switching transistors connected in series to connect a pair of cells in parallel; a pair of diodes respectively connected to the pair of switching transistors in parallel and connected to an anode terminal in common; an individual driving circuit for individually performing ON/OFF operation of the pair of switching transistors; and a driving circuit which when turning on either one of the pair of switching transistors, sets a drive voltage to be applied to a control terminal of the one switching transistor to be turned on so that a voltage of a node of the pair of switching transistors becomes a voltage capable of preventing flow of a current to a cell of the switching transistor in OFF operation through the diode.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a switch box.

  In recent years, computerization has progressed in various fields, and a plurality of secondary batteries have been used as power sources due to demands for securing electric capacity.

  In addition, in automobiles, in-vehicle power supplies are equipped with a lithium-ion battery as a sub-battery for supplying power to in-vehicle devices such as audio equipment in addition to lead-acid batteries as main batteries that drive starter motors for engine start A system has been proposed.

The background of the proposal of such an in-vehicle power supply system includes not only securing electric capacity but also improving the life of the apparatus and suppressing cost increase.
That is, a lead storage battery as a main battery is less expensive than a lithium ion battery as a sub battery, but has low durability against frequent charging and discharging. Especially when a lead-acid battery is used in a vehicle that has an idle stop function that stops the engine when the vehicle is stopped, or a vehicle that generates electricity by using the alternator to regenerate the vehicle's regenerative energy, it is frequently discharged or charged. This is because early deterioration is predicted.

  Therefore, an inexpensive lead-acid battery and a lithium ion battery with high durability against frequent charging and discharging are installed at the same time, and frequent charging and discharging operations such as power supply to the load and regenerative charging during idle stop are applied to the lithium ion battery. By giving priority to reducing the deterioration of lead-acid batteries, and by ensuring the lead-acid batteries are responsible for securing power capacity such as long-term backup power supply, we aim to reduce costs by reducing the capacity of lithium-ion batteries. -ing

JP 2009-166769 A

In realizing the above configuration, the main battery and the sub-battery are connected via the switch box in order to control the connection state between the two batteries based on the voltage of each battery.
By the way, in the in-vehicle power supply system as described above, the switch box includes a plurality of switching transistors (for example, MOSFETs). In order to operate the switch box reliably, the plurality of switching transistors are used in the test mode. It is desirable to be able to reliably detect an open failure or a short-circuit failure by individually driving the devices.

  The present invention has been made in view of the above circumstances, and in order to reliably detect an open failure or a short-circuit failure for each of the switching transistors connected in parallel, a plurality of switching transistors connected in parallel are provided. An object is to provide a switch box that can be individually driven.

  In order to solve the above-described problem, a switch box according to an embodiment includes a pair of switching transistors connected in series for connecting a pair of batteries in parallel, a parallel connection to each of the pair of switching transistors, and an anode terminal A pair of diodes connected in common, an individual drive circuit for individually turning on / off the pair of switching transistors, and connection of the pair of switching transistors when one of the pair of switching transistors is turned on The drive voltage applied to the control terminal of the one switching transistor to be turned on is set so that the voltage at the point does not flow through the diode to the battery on the switching transistor side during the off operation. And a driving circuit for

  Further, in the switch box, a wraparound prevention circuit for preventing the wraparound of power from one switching transistor in an on state to another switching transistor via the control terminal is provided with the control terminals connected in common. It may be.

  In the switch box, a pair or a plurality of pairs of switching transistors connected in parallel to the pair of switching transistors, and a pair or a plurality of pairs connected in parallel to the pair of switching transistors. Are connected in parallel to each of the switching transistors, and a pair or a plurality of pairs of diodes whose anode terminals are commonly connected, and a pair or a plurality of pairs of switching transistors connected in parallel to the pair of switching transistors, respectively. One or a plurality of pairs of individual drive circuits that individually perform on / off operations of the corresponding switching transistors may be provided.

In the above switch box, the voltage at the connection point of the pair of switching transistors is Vmid, the voltage of the battery on the switching transistor side in the on operation of the pair of batteries is V1, and the off operation of the pair of batteries is performed. The voltage of the battery on the switching transistor side is V2, the voltage drop of the switching transistor during the on operation is VDS, and the breakdown of the parasitic diode of the switching transistor during the off operation paired with the switching transistor during the on operation is When the voltage is VD, the drive voltage may be set so as to satisfy the following expression.
V1-VDS = Vmid <V2 + VD

  In the switch box, the switching transistor may be an N-channel MOSFET, and the control terminal may be a gate terminal.

  Further, in the switch box, the wraparound prevention circuit may ground the control terminal via a switching element.

  According to the switch box of the embodiment, there is an effect that the plurality of switching transistors connected in parallel in the open failure can be reliably driven individually.

FIG. 1 is a schematic configuration block diagram of an in-vehicle power supply system including a pair of in-vehicle batteries. FIG. 2 is a schematic configuration block diagram of the switch box. FIG. 3 is an explanatory diagram of a detailed circuit example of the switch box. FIG. 4 is a timing chart of the individual operation test of the switching transistors constituting the switch box.

Next, preferred embodiments will be described with reference to the drawings.
FIG. 1 is a schematic configuration block diagram of an in-vehicle power supply system including a pair of in-vehicle batteries.
The in-vehicle power supply system 10 includes a main battery 11 configured as a lead storage battery, a sub-battery 12 also configured as a lead storage battery, an in-vehicle controller 13 configured as an ECU and the like, and the main battery 11 under the control of the in-vehicle controller 13. And a switch box 14 including a solid state relay (SSR) configured as a relay transistor circuit that performs parallel connection / cutoff between the sub battery 12 and the sub battery 12.

  In the above configuration, the in-vehicle controller 13 individually controls on or off a plurality of FETs constituting the switch box 14 in the inspection mode, and configures the switch box 14 based on the obtained test voltage VTST. It detects short-circuit failure and open failure of each FET.

  Further, in the normal operation mode, the in-vehicle controller 13 has an SOC (State Of Charge) of the main battery 11 or the sub battery 12 in order to prevent premature deterioration due to overcharge or overdischarge of the main battery 11 and the sub battery 12. Control is performed so that it is within the appropriate range.

  That is, when the SOC of the main battery 11 falls below an appropriate range, charging the main battery 11 is promoted by setting the set voltage of the generated power adjusted by the regulator high. Further, when the SOC of the main battery 11 rises from an appropriate range, the discharge from the main battery 11 is promoted by setting the set voltage of the generated power adjusted by the regulator low.

  By the way, the open voltage of the main battery 11 and the open voltage of the sub battery 12 are usually different. If the main battery 11 and the sub battery 12 are simply electrically connected, the main battery 11 If the set voltage of the generated power is changed to keep the SOC within an appropriate range, the sub-battery 12 may be overcharged or overdischarged.

  For this reason, when the in-vehicle controller 13 charges the main battery 11 and does not want to charge the sub battery 12, or does not want to discharge the sub battery 12 to the main battery 11, the in-vehicle controller 13 On the other hand, the main battery 11 and the sub-battery 12 are switched to a cut-off state, or an instruction to maintain the cut-off state is issued.

FIG. 2 is a schematic configuration block diagram of the switch box.
The switch box 14 includes a plurality of (three in FIG. 2) relay transistor circuits 21-1 to 21-3 connected in parallel and a plurality of relay transistors based on the all-on control signal CALL-ON from the in-vehicle controller 13. A plurality of relay transistor circuits 21-1 to 21-3 are simultaneously operated based on a simultaneous ON circuit 22 for simultaneously turning on the circuits 21-1 to 21-3 and an all-off control signal CALL-OFF from the in-vehicle controller 13. Based on the simultaneous OFF circuit 23 for OFF operation and the individual ON / OFF control signals CON-OFF11, CON-OFF12, CON-OFF21, CON-OFF22, CON-OFF31, and CON-OFF32 from the in-vehicle controller Each of N-channel MOSFETs functioning as six switching transistors, which will be described later, constituting the relay transistor circuits 21-1 to 21-3, In order to perform an individual operation test of the switch transistor, individual drive circuits 24-1 to 24-6 provided for each relay transistor circuit, a main voltage detection circuit 25 for detecting the voltage VMB of the main battery 11, and The sub-voltage detection circuit 26 for detecting the voltage VSB of the sub-battery 12 and the test-time voltage detection circuit for detecting the test-time voltage VTST during the failure detection operation (failure detection test) of the relay transistor circuits 21-1 to 21-3. 27.
In the above configuration, the relay transistor circuits 21-1 to 21-3 function as solid state relays.

In this case, the test time voltage detection circuit 27 functions as a potential detection circuit.
The reason why a plurality of relay transistor circuits are provided is to divide the current into a plurality of systems and to secure a substantial electric capacity.

FIG. 3 is an explanatory diagram of a detailed circuit example of the switch box.
As shown in FIG. 3, the relay transistor circuits 21-1 to 21-3 include a pair of N-channel MOSFETs 31-1 and 31-2 whose source terminals are back-to-back connected. Further, a pair of Zener diodes having anodes connected between the source terminal and gate terminal of the N-channel MOSFET 31-1 and between the source terminal and gate terminal of the N-channel MOSFET 31-2 prevent backflow, and the N-channel MOSFET 31-1 Alternatively, a backflow prevention constant voltage circuit CV for applying a predetermined constant voltage is connected between the source terminal and the gate terminal of the N-channel MOSFET 31-2.

  In the above configuration, the N-channel MOSFETs 31-1 of the relay transistor circuits 21-1 to 21-3 are connected in parallel, and the gate terminals that are control terminals are commonly connected, so that the main battery 11 and the sub battery 12 that are a pair of batteries. Are functioning as a plurality of switching transistors for connecting in parallel.

  Further, the entire N-channel MOSFET 31-1 of the relay transistor circuits 21-1 to 21-3 constitutes one switching transistor group among the pair of switching transistor groups.

  Similarly, the N-channel MOSFETs 31-2 of the relay transistor circuits 21-1 to 21-3 are connected in parallel, and the gate terminals that are the control terminals are connected in common to connect the main battery 11 and the sub battery 12 that are a pair of batteries. It functions as a plurality of switching transistors for parallel connection.

  Further, the entire N-channel MOSFET 31-2 of the relay transistor circuits 21-1 to 21-3 constitutes the other switching transistor group of the pair of switching transistor groups.

  As shown in FIG. 3, the simultaneous ON circuit 22 includes a PNP transistor 33 having a collector terminal connected to the gate terminals of a pair of N-channel MOSFETs 31-1 and 31-2 constituting a relay transistor via a current limiting resistor 32. The booster circuit 34 is connected to the emitter terminal of the PNP transistor 33 and can apply an “H” level voltage, and the all-on control signal CALL-ON is input from the in-vehicle controller to the base terminal, and the collector terminal of the PNP transistor 33 An NPN transistor that is connected to the base terminal, has a collector terminal connected to the base terminal of the PNP transistor 33 via a pull-down resistor 35, has an emitter terminal grounded, and drives the PNP transistor 33 based on the all-on control signal CALL-ON 36.

  In the above configuration, a constant voltage circuit CV2 in which a Zener diode and a resistor are connected in parallel is provided between the base terminal and the emitter terminal of the PNP transistor 33 in order to make the base-emitter voltage in the ON state of the PNP transistor 33 constant. It has been.

  As shown in FIG. 3, the simultaneous OFF circuit 23 has a source terminal connected to both source terminals of the pair of N-channel MOSFETs 31-1 and 31-2, and a gate terminal of each of the pair of N-channel MOSFETs. N-channel MOSFETs 37 (= driving circuit) for controlling off-state, in which the drain terminals are connected to both gate terminals of the N-channel MOSFETs 31-1 and 31-2 and are turned on to short-circuit the source-gate terminals of the N-channel MOSFETs. ), A pull-down resistor 38 for connecting the gate terminal of the N-channel MOSFET 37 to the reference potential Vref (= 0 V), a collector terminal is connected to a connection point of the N-channel MOSFET 37 and the pull-down resistor 38, and an emitter terminal is connected to the booster circuit 34. Is connected to the PNP transistor 39 and the base terminal The all-off control signal CALL-OFF is input from the roller, the collector terminal is connected to the base terminal of the PNP transistor 39 via the pull-down resistor 40, the emitter terminal is grounded, and the PNP transistor is based on the all-off control signal CALL-OFF. NPN transistor 41 for driving 39.

  In addition, a pair of Zener diodes connected to the anode between the source terminal and the gate terminal of the N-channel MOSFET 37 prevent backflow, and a predetermined constant voltage is applied between the source terminal and the gate terminal of the N-channel MOSFET 37. A backflow prevention constant voltage circuit CV1 is connected. In addition, a constant voltage circuit CV3 in which a Zener diode and a resistor are connected in parallel is provided between the base terminal and the emitter terminal of the PNP transistor 39 in order to make the base-emitter voltage in the ON state of the PNP transistor 39 constant. Yes.

Next, when the N-channel MOSFETs 31-1 and 31-2 that constitute the relay transistor circuits 21-1 to 21-3 and each function as a switching transistor are separately tested, the corresponding N-channel MOSFET 31-1, The individual drive circuits 24-1 to 24-6 for individually driving the 31-2 will be described.
Here, the individual drive circuit 24-1 can drive the N-channel MOSFET 31-1 constituting the relay transistor circuit 21-1, and the individual drive circuit 24-2 constitutes the relay transistor circuit 21-1. The N-channel MOSFET 31-2 can be driven. Similarly, the individual drive circuit 24-3 can drive the N-channel MOSFET 31-1 constituting the relay transistor circuit 21-2, and the individual drive circuit 24-4 constitutes the relay transistor circuit 21-2. The N-channel MOSFET 31-2 can be driven, and the individual drive circuit 24-5 can drive the N-channel MOSFET 31-1 constituting the relay transistor circuit 21-3. The individual drive circuit 24-6 The N-channel MOSFET 31-2 constituting the relay transistor circuit 21-3 can be driven.
By the way, since the individual drive circuits 24-1 to 24-6 have the same configuration, the individual drive circuit 24-1 will be described as an example with reference to FIG.

  The individual drive circuit 24-1 has an emitter terminal connected to each of the main battery 11 and the sub-battery 12 via forward-connected diodes D11 and D12, and the collector terminal forms a voltage dividing circuit. The PNP transistor 52 connected to the gate terminal of the N-channel MOSFET 31-1 and the high-potential side terminal connected to the emitter terminal of the PNP transistor 52 via the voltage dividing resistor 51-1 of the resistors 51-1 and 51-2. The voltage dividing circuit 53 connected in parallel with the PNP transistor 52 to supply the divided voltage to the base terminal of the PNP transistor 52, the low potential side terminal of the voltage dividing circuit 53 is connected to the collector terminal, and the emitter terminal is grounded NPN transistor whose individual on / off control signal CON-OFF11 from the in-vehicle controller 13 is input to the base terminal It is provided with a motor 54, a.

  In the above configuration, the collector terminals of all the PNP transistors 52 constituting the individual drive circuits 24-1 to 24-6 are commonly connected to the collector terminal of the NPN transistor 56 via the pull-down resistor 55.

  Here, the NPN transistor 56 receives the turn-in prevention control signal CSTP from the in-vehicle controller 13 at the base terminal, and is turned on during the individual on / off operation. As a result, the N-channel MOSFET 31-1 other than the control target is controlled regardless of the operation state (ON or OFF) of the control-target N-channel MOSFET 31-1 (or N-channel MOSFET 31-2) that is the target of the individual ON / OFF operation. , 31-2 is in a grounded state ("L" level) and is not turned on due to the wraparound of power when controlling the N-channel MOSFET 31-1 (or N-channel MOSFET 31-2) to be controlled. The other N-channel MOSFETs 31-1 and 31-2 to be controlled are not operated. That is, the pull-down resistor 55 and the NPN transistor 56 function as the wraparound prevention circuit 28.

  As a result, each of the N-channel MOSFET 31-1 and the N-channel MOSFET 31-2 which are switching transistors connected in parallel can be individually driven in order to reliably detect an open failure or a short-circuit failure for each switching transistor.

  A plurality of N-channel MOSFETs 31-1 (switching transistors) connected in parallel and a plurality of N-channel MOSFETs 31-2 (switching transistors) connected in parallel are used as a switching transistor group, and a pair of switching transistor groups are connected in series. Since it is connected to the wraparound prevention circuit 28, it is possible to reliably prevent the wraparound of electric power with a simple configuration.

Next, the operation of the embodiment will be described.
[1] Operation when All is On First, the operation when all the N-channel MOSFETs 31-1 to 31-2 constituting the relay transistor circuits 21-1 to 21-3 are all turned on will be described. .
In the initial state, all the N-channel MOSFETs 31-1 to 31-2 constituting the relay transistor circuits 21-1 to 21-3 are in an off state, and the N-channel MOSFET 31-1, the N-channel MOSFET 31-2, Since the source terminals are back-to-back connected and the parasitic diodes are opposite to each other, the main battery 11 and the sub-battery 12 are not connected.

First, the in-vehicle controller 13 sets the all-on control signal CALL-ON = “H” level.
As a result, the NPN transistor 36 is turned on, the potential of the base terminal of the PNP transistor 33 is brought to the ground level by the pull-down resistor 35, and the PNP transistor 33 is turned on.
As a result, the “H” level voltage (= 20 V) of the booster circuit 34 is applied to the gate terminals of the N-channel MOSFETs 31-1 and 31-2 constituting the relay transistor circuits 21-1 to 21-3. When applied, all the N-channel MOSFETs 31-1 and 31-2 are turned on (closed).

  Accordingly, the main battery 11 and the sub-battery 12 are connected in parallel via the relay transistor circuits 21-1 to 21-3 and integrally supply power.

[2] Operation at All OFF Next, operation at all OFF when all the N-channel MOSFETs 31-1 to 31-2 constituting the relay transistor circuits 21-1 to 21-3 are all turned off will be described. To do.
In the initial state, it is assumed that all the N-channel MOSFETs 31-1 to 31-2 constituting the relay transistor circuits 21-1 to 21-3 are in an on state.

The in-vehicle controller 13 sets the all-on control signal CALL-ON = “L” level, turns off the NPN transistor 36 and the PNP transistor 33, and then sets the all-off control signal CALL-OFF = “H” level.
As a result, the NPN transistor 41 is turned on, the potential of the base terminal of the PNP transistor 39 is brought to the ground level by the pull-down resistor 40, and the PNP transistor 39 is turned on.

As a result, the “H” level voltage of the booster circuit 34 is applied to the gate terminal of the N-channel MOSFET 37.
The N-channel MOSFET 37 is turned on, and the potentials of the source terminals and the gate terminals of all the N-channel MOSFETs 31-1 to 31-2 constituting the relay transistor circuits 21-1 to 21-3 are the same potential. Thus, all the N-channel MOSFETs 31-1 to 31-2 are turned off.

  Accordingly, the parallel connection between the main battery 11 and the sub battery is canceled by the relay transistor circuits 21-1 to 21-3.

[3] Operation at the time of the individual operation test of the switched-on transistor An individual operation test for individually testing the N-channel MOSFETs 31-1 to 31-2 constituting the relay transistor circuits 21-1 to 21-3. The individual on / off operation of the switching transistor performed at this time will be described with reference to FIG.
FIG. 4 is a timing chart of the individual operation test of the switching transistors constituting the switch box.
As described above, since the individual drive circuits 24-1 to 24-6 have the same configuration, the operation is also the same.
Therefore, the individual on / off operation of the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 will be described using the individual drive circuit 24-1 as an example.
In this case, the individual on operation and the individual off operation are performed continuously.

First, the individual ON operation will be described.
In the initial state, all the N-channel MOSFETs 31-1 and 31-2 constituting the relay transistor circuits 21-1 to 21-3 are in an off state, and the main battery 11 and the sub battery 12 are not connected. It shall be.
The above state can be confirmed by the fact that the test voltage VTST detected by the test voltage detection circuit 27 is 0 V (ground potential).

  First, the vehicle-mounted controller 13 sets the wraparound prevention control signal CSTP to the “H” level voltage at time t1. As a result, the NPN transistor 56 is turned on, and the gate terminals of all the N-channel MOSFETs 31-1 and 31-2 are grounded (“L” level) via the pull-down resistor 55.

  At this time, the in-vehicle controller 13 monitors the test voltage VTST output from the test voltage detection circuit 27, and when the test voltage detection circuit 27 has all the N-channel MOSFETs 31-1 and 31-2 in the off state. It is confirmed that the detected potential, that is, the test voltage VTST detected by the test voltage detection circuit 27 is 0 V (ground potential).

Next, the in-vehicle controller 13 individually turns on the N-channel MOSFET, and detects whether the N-channel MOSFET to be tested is turned on (open failure) based on the test-time voltage VTST detected by the test-time voltage detection circuit 27. .
The in-vehicle controller 13 includes a pair of N-channel MOSFETs whose source terminals are back-to-back connected to a source terminal of an N-channel MOSFET to be tested (N-channel MOSFET 31-1 in the following description), and the pair of N-channel MOSFETs. The voltages of the N-channel MOSFETs connected in parallel (in the following description, all N-channel MOSFETs 31-2) are supplied by the main voltage detection circuit 25 or the sub-voltage detection circuit 26 (sub-voltage detection circuit 26 in the following description). To detect.

  Next, the test voltage (individual drive voltage) output to the corresponding relay transistor circuits 21-1 to 21-3 by the individual drive circuits 24-1 to 24-6 is applied to the N-channel MOSFET to be tested. The voltage obtained by subtracting the voltage drop of the N-channel MOSFET to be tested from the voltage of the connected battery, that is, the voltage at the connection point of the N-channel MOSFET is the voltage of the N-channel MOSFET paired with the N-channel MOSFET to be tested. It is determined whether or not the sum of the breakdown voltage of the parasitic diode and the voltage of the battery connected to the tip of the paired N-channel MOSFET is higher.

  This is because the voltage at the connection point between the N-channel MOSFET to be tested and the paired N-channel MOSFET in a state where the test voltage (individual drive voltage) is applied to the gate terminal of the N-channel MOSFET to be tested (individual drive target). Is higher than the voltage of the battery connected to the tip of the cathode terminal of the parasitic diode of the paired N-channel MOSFET, current flows to the battery on the paired N-channel MOSFET side via the parasitic diode. This is because the test voltage VTST fluctuates and an accurate individual on-operation test cannot be performed.

In other words, the test voltage (individual drive voltage) is a low voltage of the main battery 11 and the sub-battery 12 that are a pair of batteries, with the voltage at the connection point of the pair of N-channel MOSFETs 31-1 and 31-2 being Vmid. The breakdown of the diode connected to the high-voltage battery is V1, the voltage of the high-voltage battery is V2, the voltage drop of the switching transistor connected to the low-voltage battery is VDS, When the voltage is VD, it is set so as to satisfy the following equation.
V1-VDS = Vmid <V2 + VD

  For example, when 7V is used as the test voltage (individual drive voltage) satisfying the above formula and the battery voltage V2 on the high voltage side is 12V, the voltage V1 on the low voltage side is about 3V. Thus, no current flows through a parasitic diode having a cathode connected to the battery, and an accurate individual ON operation test can be performed.

  The in-vehicle controller 13 then applies the test target to the voltage obtained by subtracting the voltage drop of the N-channel MOSFET to be tested from the voltage of the battery connected to the N-channel MOSFET to be tested in a state where the test voltage is applied. Individual ON operation when the sum of the breakdown voltage of the parasitic diode of the N-channel MOSFET paired with the N-channel MOSFET and the voltage of the battery connected to the tip of the paired N-channel MOSFET is higher (Hereinafter, the processing performed after detecting that all the N-channel MOSFETs 31-1 to 31-2 are in the OFF state and before shifting to the actual individual ON operation test is referred to as pre-test processing. .)

  When the pre-test process is completed, the in-vehicle controller 13 applies the individual on / off control signal CON-OFF11 to the base terminal of the NPN transistor 54 as the “H” level voltage at time t2. As a result, a current flows from the base terminal of the NPN transistor 54 to the emitter terminal, and the NPN transistor 54 is turned on.

Accordingly, power is supplied to the voltage dividing circuit 53 from the main battery 11 and the sub battery 12 via the diodes D11 and D12, and the voltage of the supplied power is divided and applied to the base terminal of the PNP transistor 52. To do.
As a result, a current flows from the base terminal of the PNP transistor 52 to the collector terminal, and the PNP transistor 52 is turned on.

As a result, power is supplied from the main battery 11 and the sub battery 12 via the diodes D11 and D12 to the voltage dividing resistors 51-1 and 51-2 constituting the voltage dividing circuit via the PNP transistor 52. A divided voltage obtained by dividing the voltage of the generated power is applied as a test voltage to the gate terminal of the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 that is the N-channel MOSFET to be measured. As described above, since the current does not flow from the main battery 11 side to the sub-battery 12 side through the parasitic diode of any N-channel MOSFET 31-2 as described above, an accurate individual on-operation test is performed. Can be done.
On the other hand, since the wraparound prevention control signal CSTP remains at the “H” level voltage, the N-channel MOSFET 31-2 of the relay transistor circuit 21-1 and the N of the relay transistor circuit 21-2 which are non-measurement target N-channel MOSFETs. The gate terminals of the channel MOSFETs 31-1 and 31-2 and the N-channel MOSFETs 31-1 and 31-2 of the relay transistor circuit 21-3 remain in the ground state ("L" level).
The source potentials of all the N-channel MOSFETs 31-2 and relay transistor circuits 21-2 functioning as switching transistors are in the “L” level state.

  Therefore, a predetermined constant voltage is applied between the source terminal and the gate terminal of the N-channel MOSFET 31-1 by the backflow prevention constant voltage circuit CV, and the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 is at time t2. , It is turned on alone.

  As a result, when the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 normally shifts to the ON state, the test-time voltage detection circuit 27 causes the relay transistor that has risen to a predetermined potential by the power supplied from the main battery 11. The potential of the source terminal of the N-channel MOSFET 31-1 of the circuit 21-1 is detected. Then, the test voltage detection circuit 27 outputs the test voltage VTST to the in-vehicle controller 13.

  Therefore, in the in-vehicle controller 13, the test-time voltage VTST becomes a predetermined potential, and the potential of the source terminal of the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 is higher than the initial state where the N-channel MOSFET 31-1 is in the off state. In the case where the value rises above a predetermined threshold value, it is determined that the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 has normally transitioned to the on state.

  Conversely, when the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 cannot normally shift to the on state, the test-time voltage detection circuit 27 indicates that all the N-channel MOSFETs 31-1 to 31-2 are in the off state. In this case, the in-vehicle controller 13 determines that the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 is in the OFF state, that is, an open failure.

Next, in the individual on operation, when the in-vehicle controller 13 confirms that the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 is normal, the in-vehicle controller 13 performs the individual off operation.
First, the vehicle-mounted controller 13 applies the individual on / off control signal CON-OFF11 to the base terminal of the NPN transistor 54 as the “L” level voltage at time t3. As a result, the NPN transistor 54 transitions to the off state.

  Accordingly, the voltage is supplied to the voltage dividing circuit 53 from the main battery 11 and the sub-battery 12 via the diodes D11 and D12 as it is, so that the power supply voltage is also supplied to the base terminal of the PNP transistor 52. The PNP transistor 52 will transition to the off state.

  As a result, power is not supplied to the voltage dividing resistors 51-1 and 51-2 via the PNP transistor 52. Therefore, the gate terminal of the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 is connected to the pull-down resistor 55 and the NPN transistor 56. If the N-channel MOSFET 31-1 is normal and the N-channel MOSFET 31-1 is normal, the N-channel MOSFET 31-1 transitions to an off state.

  Therefore, the in-vehicle controller 13 makes the potential of the source terminal of the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 equal to the initial state where the N-channel MOSFET 31-1 is in the off state based on the test voltage VTST. For example, it is determined that the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 has normally transitioned to the OFF state.

  Conversely, when the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 cannot normally shift to the OFF state, the test-time voltage VTST output from the test-time voltage detection circuit 27 is in the OFF state. In the case where the predetermined threshold value is exceeded beyond the initial state, the in-vehicle controller 13 determines that the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 remains in the on state and is a short circuit failure. It becomes.

When the individual operation test of the N-channel MOSFET 31-1 of the relay transistor circuit 21-1 is completed, the individual ON / OFF operation is similarly performed for the N-channel MOSFET 31-2 of the relay transistor circuit 21-1.
When the individual operations of the N-channel MOSFET 31-1 and the N-channel MOSFET 31-2 of the relay transistor circuit 21-1 are completed, the vehicle-mounted controller 13 sets the wraparound prevention control signal CSTP as the “L” level voltage at time t4. The process is terminated.

Thereafter, the in-vehicle controller 13 similarly performs the individual ON / OFF operation of the N-channel MOSFET 31-1 and the N-channel MOSFET 31-2 constituting the remaining relay transistor circuits 21-2 and 21-3, and these are normal. Whether or not is determined individually.
As described above, according to the present embodiment, the N-channel MOSFETs 31-1 and 31-2 that are a plurality of switching transistors can be individually tested to detect an open failure or a short-circuit failure.

  The present invention has been described based on the embodiment. However, the embodiment is an exemplification, and various modifications can be made to each of those components and combinations thereof, and such a modification is also within the scope of the present invention. It will be understood by those skilled in the art.

In the above description, a MOSFET in which a parasitic diode is formed as a switching transistor has been described. However, the present invention can be similarly applied to a configuration in which a diode is separately connected in parallel with a switching transistor such as an IGBT.
For example, in the above description, three sets of relay transistor circuits are provided. However, the present invention is not limited to this, and the present invention can be similarly applied if a plurality of relay transistor circuits are provided.
In the above description, the case of a lead storage battery has been described as the main battery 11 and the sub battery 12. However, if the rated output voltage is the same even if at least one is another secondary battery such as a lithium ion battery, It is possible to apply similarly.

  In the above description, a single secondary battery is used as the main battery 11 and the sub-battery 12, but at least one of them is a group that functions as a single battery by connecting a plurality of batteries in series or in parallel. It can also be configured to be a battery.

DESCRIPTION OF SYMBOLS 10 In-vehicle power supply system 11 Main battery 12 Sub battery 13 In-vehicle controller 14 Switch box 21-1 to 21-3 Relay transistor circuit 22 Simultaneous ON circuit 23 Simultaneous OFF circuit 24-1 to 24-6 Individual drive circuit 25 Main voltage detection circuit 26 Sub voltage detection circuit 27 Test voltage detection circuit (potential detection circuit)
28 Loop prevention circuit 31-1, 31-2 N-channel MOSFET (switching transistor)
34 Booster circuit 35 Pull-down resistor 36 NPN transistor 37 N-channel MOSFET (drive circuit)
38 Pull-down resistor 39 PNP transistor 40 Pull-down resistor 41 NPN transistor 51 Voltage divider resistor 52 PNP transistor 53 Voltage divider circuit 54 NPN transistor 55 Pull-down resistor (around prevention circuit)
56 NPN transistor (around prevention circuit)
Vref reference potential

Claims (6)

A pair of switching transistors connected in series for connecting a pair of batteries in parallel;
A pair of diodes connected in parallel to each of the pair of switching transistors and having an anode terminal commonly connected;
An individual drive circuit for individually performing on / off operations of the pair of switching transistors;
When one of the pair of switching transistors is turned on, the voltage at the connection point of the pair of switching transistors becomes a voltage at which no current flows through the diode to the battery on the switching transistor side during the off operation. A drive circuit for setting a drive voltage to be applied to the control terminal of the one switching transistor to be turned on,
Switch box with. The control terminals are connected in common,
A wraparound prevention circuit for preventing wraparound of power from one switching transistor in an on state to another switching transistor via the control terminal is provided.
The switch box according to claim 1. A pair or a plurality of pairs of switching transistors connected in parallel to the pair of switching transistors; and
A pair or a plurality of pairs of diodes connected in parallel to the pair of switching transistors, connected in parallel to each of the pair or plural pairs of switching transistors, and having an anode terminal commonly connected;
One or a plurality of pairs of individual drive circuits that are respectively provided in a pair or a plurality of pairs of switching transistors connected in parallel to the pair of switching transistors and individually perform on / off operations of the corresponding switching transistors,
The switch box according to claim 1 or 2. The voltage at the connection point of the pair of switching transistors is Vmid,
The voltage of the battery on the switching transistor side in the on operation of the pair of batteries is set to V1,
The voltage of the battery on the switching transistor side during the off operation of the pair of batteries is V2,
The voltage drop of the switching transistor during the on operation is VDS,
When the breakdown voltage of the parasitic diode of the switching transistor in the off operation that is paired with the switching transistor in the on operation is VD, the drive voltage is set to satisfy the following equation:
V1-VDS = Vmid <V2 + VD
The switch box according to any one of claims 1 to 3. The switching transistor is an N-channel MOSFET;
The control terminal is a gate terminal;
The diode is a parasitic diode;
The switch box according to any one of claims 1 to 4. The wraparound prevention circuit is configured such that the control terminal is grounded via a switching element.
The switch box according to claim 2.

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