Power supply control circuit

Abstract

A power supply control circuit allows power to be supplied to a load from a power supply, such as a sub-battery, for a longer period of time in a case where a main power supply fails. A power supply control circuit (1) is provided with: a first circuit (2) that connects a main battery (52) and a sub-battery (53) via a DC / DC converter (20); a second circuit (3) that connects the main battery (52) and the load (54); and a third circuit (4) that connects the sub-battery (53) and the load (54) via the semiconductor switch (32). When a failure occurs in the main battery (52), the semiconductor switch (32) is turned on to supply power from the sub-battery (53) to the load (54), and a forward direction of a parasitic diode (32a) of the semiconductor switch (32) is a direction from the load (54) to the sub-battery (53). In addition, the DC / DC converter (20) boosts the voltage from the main battery (53), and supplies the boosted voltage to the sub battery (53).

Description

Technical Field

[0001] The present invention relates to a power supply control circuit for controlling a battery of, for example, a vehicle. Background Art

[0002] For example, in a vehicle such as a car, not only a main battery but also a sub-battery can be installed as an on-board power source. With such a configuration, when the main battery cannot supply power to important loads due to a failure of the main battery, the sub-battery can supply power instead of the main battery.

[0003] For example, patent document 1 discloses a system including a first switch connected between a main power supply and a load, a second switch connected between a sub-battery and the load, and an anti-backflow circuit for preventing current from flowing back between the main power supply and the sub-battery, wherein the polarity of the anti-backflow circuit is designed to allow current to pass in a direction from the sub-power supply to the load even when the second switch is in a disconnected state.

[0004] Prior art

[0005] Patent Literature

[0006] Patent document 1: JP2020182318A Summary of the invention

[0007] Problems to be solved by the present invention

[0008] Incidentally, it is known that a circuit connecting a sub-battery and a load can be switched by a semiconductor switch as in Patent Document 1. In addition, the semiconductor switch may be configured with back-to-back FETs (Field Effect Transistors). Figure 4 A specific example is described.

[0009] Figure 4 The power control circuit 100 shown is connected to an AC generator 51, a main battery 52, a sub-battery 53 and a load 54, the AC generator 51 generates electricity and outputs direct current when the vehicle is running, the main battery 52 is the main power source, and the sub-battery 53 supplies power to the load 54 in the event of a main battery failure.

[0010] The power supply control circuit 100 includes a cutoff circuit 10, a DC / DC converter 20, and semiconductor switches 101, 102. The cutoff circuit 10 includes a voltage detection unit 11 and semiconductor switches 12, 13. The voltage detection unit 11 monitors the voltage supplied from the main battery 52, and when a fault is detected, controls the semiconductor switches 12, 13 to cut off the electrical connection between the power supply control circuit 100 and the main battery 52. ​​The load 54 is connected to the downstream section of the cutoff circuit 10, and during normal operation, is supplied with power from the main battery 52 via the path indicated by the arrow A11.

[0011] The DC / DC converter 20 converts the power from the main battery 52 into a predetermined DC voltage and supplies it to the sub-battery 53 to charge the sub-battery 53. The semiconductor switches 101, 102 are composed of MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The semiconductor switches 101, 102 are connected between the sub-battery 53 and the load 54 and are disconnected during normal operation, but are turned on when a failure occurs in the main battery 52, thereby supplying power from the sub-battery 53 to the load 54 (see arrow A12).

[0012] exist Figure 4 In the circuit shown, semiconductor switch 101 and semiconductor switch 102 are connected back-to-back to prevent reverse current flow during normal operation when current is applied from the main battery 52 .

[0013] As described above, when power is supplied from the sub-battery 53, current flows through the semiconductor switches 101 and 102. In this case, a voltage drop equivalent to the voltage drop of the two MOSFETs is applied to the load 54. The voltage of the battery decreases as power is supplied (discharged). Therefore, there is a risk that the time during which the load 54 can operate, that is, the time during which power is supplied from the sub-battery 53 to the load 54, may become shorter than expected due to the voltage drop caused by the semiconductor switches 101 and 102.

[0014] In view of the above problems, an object of the present invention is to provide a power supply control circuit which allows power to be supplied to a load from a power supply such as a sub-battery for a longer period of time in the event of a failure of a main power supply.

[0015] Technical Solution

[0016] The invention made to solve the above-mentioned problem is a power supply control circuit, which includes: a first circuit, which connects a first battery and a second battery via a DC / DC converter; a second circuit, which connects the first battery and a first load; and a third circuit, which connects the second battery and the first load via a first semiconductor switch, wherein, when the first battery fails, the first semiconductor switch is turned on to supply power from the second battery to the first load, the forward direction of the parasitic diode of the first semiconductor switch is from the first load to the second battery, and the DC / DC converter boosts the voltage from the first battery and supplies the boosted voltage to the second battery.

[0017] Technical Effects

[0018] According to the present invention, the third circuit connecting the second battery and the first load is connected only through the first semiconductor switch, which reduces the voltage drop compared to the back-to-back connection and allows power to be supplied to the load from the power source such as the sub-battery for a longer period of time in the event of a failure of the main power source. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] [ Figure 1 ] Figure 1 is a circuit diagram of a power supply control circuit according to an embodiment of the present invention.

[0020] [ Figure 2 ] Figure 2 During normal operation Figure 1 A diagram showing the flow of current in the circuit shown.

[0021] [ Figure 3 ] Figure 3 In case of power failure Figure 1 A diagram showing the flow of current in the circuit shown.

[0022] [ Figure 4 ] Figure 4 is an example of a conventional power supply control circuit.

[0023] Reference Mark List

[0024] 1 Power supply control circuit

[0025] 2 First Circuit

[0026] 3 Second Circuit

[0027] 4 Third Circuit

[0028] 10 Cut off the circuit

[0029] 20DC / DC Converter

[0030] 31 semiconductor switch (second semiconductor switch)

[0031] 32 semiconductor switch (first semiconductor switch)

[0032] 42IPD (protection element)

[0033] 52 Main battery (first battery)

[0034] 53 secondary battery (second battery)

[0035] 54 Load

[0036] 56 Load DETAILED DESCRIPTION

[0037] Embodiments of the present invention will be described below with reference to the accompanying drawings. Figure 1is a circuit diagram of a power supply control circuit according to an embodiment of the present invention. Figure 4 The same elements and devices are identified by the same reference numerals.

[0038] The power supply control circuit 1 is mounted on, for example, a vehicle. The vehicle according to the present embodiment is, for example, an electric vehicle such as an electric vehicle or a hybrid vehicle.

[0039] like Figure 1 As shown, the power supply control circuit 1 is connected to an AC generator 51 that outputs DC power supply power, a main battery 52 as a main power supply, a sub-battery 53 that supplies power to a load 54 when the main battery fails, and loads 54, 55, and 56. That is, the main battery 52 serves as a first battery, and the sub-battery 53 serves as a second battery.

[0040] The power supply control circuit 1 includes a cutoff circuit 10 , a DC / DC converter 20 , semiconductor switches 31 , 32 , and IPDs 41 , 42 .

[0041] The cutoff circuit 10 includes a voltage detection unit 11 and semiconductor switches 12, 13. The voltage detection unit 11 monitors the voltage supplied from the main battery 52, and when a fault is detected, the voltage detection unit 11 controls the semiconductor switches 12, 13 to cut off the electrical connection between the power supply control circuit 1 and the main battery 52.

[0042] The semiconductor switches 12 and 13 are each formed of, for example, MOSFET. Figure 1 In the circuit shown, the semiconductor switch 12 is formed of an n-channel MOSFET, and the semiconductor switch 13 is formed of a p-channel MOSFET.

[0043] The semiconductor switches 12, 13 are connected in a state where the forward direction of the parasitic diode 12a of the semiconductor switch 12 and the forward direction of the parasitic diode 13a of the semiconductor switch 13 are arranged in opposite directions to each other. That is, the source terminal of the semiconductor switch 12 and the source terminal of the semiconductor switch 13 are connected to each other. The drain terminal of the semiconductor switch 12 is connected to the main battery 52, and the drain terminal of the semiconductor switch 13 is connected to the DC / DC converter 20 and the semiconductor switch 31. That is, the semiconductor switches 12, 13 are connected back to back.

[0044] During normal operation of supplying power from the main battery 52 to the AC generator 51, the semiconductor switches 12 and 13 are in the on state to supply power to the downstream DC / DC converter 20, semiconductor switch 31, etc., but if the voltage detection unit 11 detects that the main battery 52 fails due to an abnormality, etc., the semiconductor switches 12 and 13 are disconnected to cut off the power supplied to the downstream DC / DC converter 20 and semiconductor switch 31, etc.

[0045] The DC / DC converter 20 boosts the power from the main battery 52 and supplies the power to the sub-battery 53 to charge the sub-battery 53. The DC / DC converter 20 includes MOSFETs 21, 22, a coil 23, a capacitor 24, and a diode 25. The DC / DC converter 20 supplies a voltage higher than the DC voltage supplied from the main battery 52 to the sub-battery 53, thereby making the charging voltage of the sub-battery 53 higher than the charging voltage of the main battery 52.

[0046] The semiconductor switch 31 is composed of, for example, a MOSFET. Figure 1 In the circuit of , the semiconductor switch 31 is composed of an n-channel MOSFET. The semiconductor switch 31 is connected between the load 54 and a connection point P1 located on the wiring between the cutoff circuit 10 and the DC / DC converter 20. In other words, the source terminal of the semiconductor switch 31 is connected to the cutoff circuit 10 side (connection point P1), and the drain terminal of the semiconductor switch 31 is connected to the load 54. Therefore, the parasitic diode 31a of the semiconductor switch 31 is connected so that the direction from the cutoff circuit 10 toward the load 54 is the forward direction.

[0047] During normal operation, the semiconductor switch 31 is in an on state to allow current to flow from the main battery 52 to the downstream load 54, etc. When the voltage detection unit 11 detects that the main battery 52 has failed, the semiconductor switch 31 is turned off. That is, the semiconductor switch 31 functions as a second semiconductor switch that connects the main battery 52 (first battery) and the load 54 (first load).

[0048] The semiconductor switch 32 is composed of, for example, a MOSFET. Figure 1 In the circuit of , the semiconductor switch 32 is composed of a p-channel MOSFET. The semiconductor switch 32 connects a connection point P2 and a connection point P3, the connection point P2 is located on the wiring between the DC / DC converter 20 and the connection terminal of the sub-battery 53, and the connection point P3 is located on the wiring with the load 54. That is, the source terminal of the semiconductor switch 32 is connected to the sub-battery 53 side (connection point P2), and the drain terminal is connected to the load 54 (connection point P3). Therefore, the parasitic diode 32a of the semiconductor switch 32 is connected so that the direction from the load 54 to the sub-battery 53 is the forward direction.

[0049] During normal operation, the semiconductor switch 32 is turned off, and when the voltage detection unit 11 detects that the main battery 52 has failed, the semiconductor switch 32 is turned on to supply power from the sub-battery 53 to the load 54, etc. In other words, the semiconductor switch 32 functions as a first semiconductor switch.

[0050] IPD 41, 42 is an abbreviation of intelligent power device, which is a component that integrates a highly durable semiconductor switch and various protection / diagnosis circuits in one package. IPD 41, 42 is also called a semiconductor relay. Whether to provide IPD 41, 42 is optional and is not necessarily provided.

[0051] The IPD 41 is provided at the downstream section of the semiconductor switch 31 and is connected to the load 55 to protect the load 55 from overcurrent, etc. The IPD 42 is provided at the upstream section (main battery 52 side) of the semiconductor switch 31 and is connected to the load 56 to protect the load 56 from overcurrent, etc. That is, the IPD 42 is connected to the load 56 (second load) at the upstream section of the semiconductor switch 31 (second semiconductor switch), and the IPD 42 (protection element) is connected to the upstream section of the load 56.

[0052] The above-mentioned semiconductor switch, IPD, etc. are controlled by a control unit (not shown) or the like provided separately, and the detection result of the voltage detection unit 11 is acquired.

[0053] exist Figure 1 In the configuration of , the circuit from the connection point P1 to the connection point P2 (i.e., the DC / DC converter 20) forms a first circuit 2, which connects the main battery 52 (first battery) and the sub-battery 53 (second battery) via the DC / DC converter 20. The circuit from the connection point P1 to the connection point P3 forms a second circuit 3 connecting the main battery 52 (first battery) and the load 54 (first load). The circuit from the connection point P2 to the connection point P3 forms a third circuit 4, which connects the sub-battery 53 (second battery) and the load 54 (first load) via the semiconductor switch 32 (first semiconductor switch).

[0054] The cutoff circuit 10 is connected between the main battery 52 (first battery) and the first circuit 2 / second circuit 3 .

[0055] Next, refer to Figure 2 and Figure 3 The operation of the power supply control circuit 1 having the above-described configuration is described. Figure 2 Under normal operation Figure 1 A diagram of the current flow in the circuit shown. Figure 3 In case of power failure Figure 1 A diagram of the current flow in the circuit shown.

[0056] In such Figure 2During the normal operation shown, the semiconductor switch 31 is turned on, and the semiconductor switch 32 is turned off. The IPDs 41, 42 are in the on state. Then, power is supplied from the main battery 52 and the alternator 51 to each load 54, 55, 56 (arrow A1). At the same time, the sub-battery 53 is charged by the boosted voltage from the DC / DC converter 20. In addition, since the semiconductor switch 32 is in the off state, power is not supplied from the sub-battery 53 to the load 54.

[0057] During normal operation, a voltage drop occurs due to the semiconductor switch 31. However, since the alternator 51 is connected, the main battery 52 is continuously charged. Therefore, the output voltage hardly drops due to the discharge of the main battery 52, and the voltage supplied to the load 54 does not drop below the operating voltage.

[0058] On the contrary, Figure 3 In the case where a power failure such as an abnormality occurs in the main battery 52 shown, the semiconductor switch 31 is turned off and the semiconductor switch 32 is turned on. Then, power is supplied from the sub-battery 53 to the load 54 (arrow A2). At the same time, the cutoff circuit 10 turns off the semiconductor switches 12, 13, cutting off the electrical connection with the main battery 52. ​​Therefore, the charging operation from the DC / DC converter 20 to the sub-battery 53 is also stopped.

[0059] Although the semiconductor switch 31 is turned off, the load 55 is connected to the downstream section of the semiconductor switch 31, and therefore when the semiconductor switch 32 is turned on, it becomes possible to supply power (arrow A2) from the sub-battery 53. The load 56 is connected to the upstream section (connection point P1 side) of the semiconductor switch 31, and therefore the load 56 is not electrically connected to the sub-battery 53, and is no longer supplied with power.

[0060] According to the present embodiment, the power supply control circuit 1 includes a first circuit 2 connecting the main battery 52 and the sub-battery 53 via the DC / DC converter 20, a second circuit 3 connecting the main battery 52 and the load 54, and a third circuit 4 connecting the sub-battery 53 and the load 54 via the semiconductor switch 32. When the main battery 52 fails, the semiconductor switch 32 is turned on to supply power from the sub-battery 53 to the load 54, and the forward direction of the parasitic diode 32a of the semiconductor switch 32 is the direction from the load 54 to the sub-battery 53. In addition, the DC / DC converter 20 boosts the voltage from the main battery 52 and supplies the boosted voltage to the sub-battery 53.

[0061] By configuring the power supply control circuit 1 as described above, the sub-battery 53 and the load 54 are connected only via the semiconductor switch 32 in the third circuit 4, so that the voltage drop can be reduced to about half of the voltage drop of the back-to-back connection, and power can be supplied from the sub-battery 53 to the load 54 for a longer period of time. In addition, since power can be supplied for a longer period of time in the present embodiment, this realizes a configuration that effectively maintains the system at the time of power failure, which is a requirement for, for example, autonomous driving.

[0062] Furthermore, the forward direction of the parasitic diode 32a of the semiconductor switch 32 is the direction from the load 54 to the sub-battery 53, and the DC / DC converter 20 boosts the voltage from the main battery 52 and supplies the boosted power to the sub-battery 53. Therefore, the charging voltage of the sub-battery 53 is higher than the charging voltage of the main battery 52, and this can prevent current from flowing through the parasitic diode 32a during normal operation.

[0063] Furthermore, the second circuit 3 has a semiconductor switch 31 that connects the main battery 52 and the load 54, and when the main battery 52 fails, the semiconductor switch 31 is disconnected, and the forward direction of the parasitic diode 31a of the semiconductor switch 31 is the direction from the main battery 52 to the load 54. In this way, when the main battery 52 fails, even if the cutoff circuit 10 fails, the electrical connection between the main battery 52 and the load 54 can be cut off.

[0064] In addition, the second circuit 3 is connected to the load 56 at the upstream section of the second semiconductor switch. This makes it possible to power off the load that does not need to be driven by the sub-battery 53. This makes it possible to separate the load that needs to be driven by the sub-battery 53 from the load that does not need to be driven by the sub-battery 53. As a result, the sub-battery 53 drives only the necessary load, thereby reducing power consumption and allowing power to be supplied for a longer period of time.

[0065] Furthermore, the IPD 42 may be provided at an upstream stage of the load 56. In this case, the load 56 can be protected from an overcurrent or the like.

[0066] Furthermore, a cutoff circuit 10 that cuts off the power supply of the main battery 52 when a failure occurs in the main battery 52 is connected between the main battery 54 and the first circuit 2 / second circuit 3. In this case, when a failure occurs in the main battery 52, for example, when an abnormality occurs in the main battery 52, the power supply from the main battery 52 can be cut off.

[0067] The present invention is not limited to the above-described embodiments. In other words, those skilled in the art can implement the present invention by modifying the present invention in various ways according to conventionally known knowledge without departing from the gist of the present invention. As long as the power supply control circuit of the present invention is still provided after such modification, it is certainly included in the scope of the present invention.

Claims

1. A power control circuit, comprising: a first circuit connected to a first battery and a second battery via a DC / DC converter; a second circuit connecting the first battery and a first load; as well as a third circuit connecting the second battery and the first load via a first semiconductor switch, wherein, when the first battery fails, the first semiconductor switch is turned on to supply power from the second battery to the first load, The forward direction of the parasitic diode of the first semiconductor switch is from the first load to the second battery, and The DC / DC converter boosts the voltage from the first battery and supplies the boosted voltage to the second battery.

2. The power control circuit according to claim 1, wherein: The second circuit includes a second semiconductor switch connecting the first battery and the first load. When the first battery fails, the second semiconductor switch is turned off, and The forward direction of the parasitic diode of the second semiconductor switch is from the first battery to the first load.

3. The power supply control circuit according to claim 2, wherein: The second circuit is connected to a second load at an upstream section of the second semiconductor switch.

4. The power supply control circuit according to claim 3, wherein: A protection element is arranged at an upstream section of the second load.

5. The power supply control circuit according to claim 1, wherein: A cutoff circuit is connected between the first battery and the first and second circuits to cut off power supplied from the first battery when a failure occurs in the first battery.

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