Power supply control circuit

Abstract

To provide a power supply control circuit capable of prolonging a power supply time from a power supply to a load when a main power supply such as a sub battery falls.SOLUTION: A power supply control circuit 1 comprises a first circuit 2 which connects a main battery 52 with a sub battery 53 via a DC / DC converter 20, a second circuit 3 which connects the main battery 52 with a load 54, and a third circuit 4 which connects the sub battery 53 with the load 54 via a semiconductor switch 32. The semiconductor switch 32 is turned on when the main battery 52 falls and supplies power from the sub battery 53 to the load 54. A parasitic diode 32a of the semiconductor switch 32 has a forward direction from the load 54 side to the sub battery 53. Furthermore, the DC / DC converter 20 boosts a voltage from the main battery 52 to supply the same to the sub battery 53.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

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

[0003] For example, Patent Document 1 describes a device that includes a first switch connected between a main power supply and a load, a second switch connected between a sub-battery and the load, and a reverse current prevention circuit that prevents reverse current flow between the main power supply and the sub-battery, and that allows current to pass from the sub-battery to the load even when the second switch is off. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-182318 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, it is known that the circuit connecting the sub-battery and the load can be switched by a semiconductor switch as in Patent Document 1. In addition, this semiconductor switch may be configured with back-to-back FETs (field effect transistors). A specific example will be described with reference to FIG.

[0006] The power supply control circuit 100 shown in FIG. 4 is connected to an alternator 51 that generates power and outputs DC power when the vehicle is in operation, a main battery 52 that is the main power supply, a sub-battery 53 that supplies power to a load 54 in the event of a failure of the main battery, and the load 54.

[0007] The power supply control circuit 100 includes an interrupter circuit 10, a DC / DC converter 20, and semiconductor switches 101 and 102. The interrupter circuit 10 includes a voltage detection unit 11 and semiconductor switches 12 and 13. The voltage detection unit 11 monitors the voltage supplied from the main battery 52, and when a failure is detected, controls the semiconductor switches 12 and 13 to interrupt the electrical connection between the power supply control circuit 100 and the main battery 52. ​​The load 54 is connected to the rear stage of the interrupter circuit 10, and is normally supplied with power from the main battery 52 via the path indicated by the arrow A11.

[0008] 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 and 102 are composed of MOSFETs (metal oxide semiconductor field effect transistors). The semiconductor switches 101 and 102 are connected between the sub-battery 53 and the load 54 and are normally off, but are turned on when the main battery 52 fails, so that power is supplied from the sub-battery 53 to the load 54 (see arrow A12).

[0009] In the circuit shown in FIG. 4, semiconductor switch 101 and semiconductor switch 102 are connected back-to-back to prevent a reverse current flow during normal operation when current is applied from main battery 52.

[0010] As described above, when power is supplied from sub-battery 53, it passes through semiconductor switch 101 and semiconductor switch 102. In this case, a voltage drop equivalent to two MOSFETs is applied to load 54. The voltage of a battery decreases as power is supplied (discharged). Therefore, there is a risk that the time during which load 54 can operate, that is, the time during which power is supplied from sub-battery 53 to load 54, may become shorter than expected due to the voltage drop due to semiconductor switches 101 and 102.

[0011] In view of the above problems, an object of the present invention is to provide a power supply control circuit that can extend the time for which power is supplied from a power supply to a load when a main power supply such as a sub-battery fails. [Means for solving the problem]

[0012] The invention made to solve the above problem includes a first circuit that connects a first battery and a second battery via a DC / DC converter, a second circuit that connects the first battery and a first load, and a third circuit that connects the second battery and the first load via a first semiconductor switch, wherein the first semiconductor switch is It consists of one transistor, The first semiconductor switch is turned on when the first battery fails to supply power from the second battery to the first load. Transistors that make up The parasitic diode of Second The power supply control circuit is characterized in that a direction toward the battery side is defined as a forward direction, and the DC / DC converter boosts the voltage from the first battery and supplies the boosted voltage to the second battery. Effect of the Invention

[0013] According to the present invention, in the third circuit connecting the second battery and the first load, the connection is made only via the first semiconductor switch, so that the voltage drop can be reduced more than in a back-to-back connection, and the time for which power is supplied from the power source to the load in the event of a failure of the main power source such as a sub-battery can be extended. [Brief description of the drawings]

[0014] [Figure 1] 1 is a circuit diagram of a power supply control circuit according to an embodiment of the present invention; [Diagram 2] 2 is a diagram showing a current flow in the circuit shown in FIG. 1 under normal circumstances. FIG. [Diagram 3] 2 is a diagram showing a current flow in the circuit shown in FIG. 1 when a power supply fails. [Figure 4] 1 is an example of a conventional power supply control circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a circuit diagram of a power supply control circuit according to an embodiment of the present invention. Note that the same elements and devices as those in Fig. 4 described above are indicated with the same reference numerals.

[0016] The power supply control circuit 1 is mounted on, for example, a vehicle. Here, the vehicle of this embodiment is, for example, an electrically powered vehicle such as an electric car or a hybrid car.

[0017] 1, the power supply control circuit 1 is connected to an alternator 51 that outputs DC power supply power, a main battery 52 that is 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 functions as the first battery, and the sub-battery 53 functions as the second battery.

[0018] The power supply control circuit 1 includes an interrupter circuit 10, a DC / DC converter 20, semiconductor switches 31 and 32, and IPDs 41 and .

[0019] The interruption circuit 10 includes a voltage detection unit 11 and semiconductor switches 12 and 13. The voltage detection unit 11 monitors the voltage supplied from the main battery 52, and when a failure is detected, the voltage detection unit 11 controls the semiconductor switches 12 and 13 to interrupt the electrical connection between the power supply control circuit 100 and the main battery 52.

[0020] The semiconductor switches 12 and 13 are configured, for example, by MOSFETs. In the circuit of Fig. 1, the semiconductor switch 12 is configured by an n-channel MOSFET, and the semiconductor switch 13 is configured by a p-channel MOSFET.

[0021] The semiconductor switches 12 and 13 are connected in a state in which 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 the 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 and 13 are connected back-to-back.

[0022] The semiconductor switches 12 and 13 are normally turned on when electricity is supplied from the main battery 52 to the alternator 51, and supply electricity to the downstream DC / DC converter 20, semiconductor switch 31, etc., but if the voltage detection unit 11 detects that the main battery 52 has failed due to an abnormality or the like, the semiconductor switches 12 and 13 are turned off, and electricity is cut off to the downstream DC / DC converter 20, semiconductor switch 31, etc.

[0023] The DC / DC converter 20 boosts the power from the main battery 52 and supplies it to the sub-battery 53 to charge the sub-battery 53. The DC / DC converter 20 includes MOSFETs 21 and 22, a coil 23, a capacitor 24, and a diode 25. The DC / DC converter 20 supplies a voltage to the sub-battery 53 that is higher than the DC voltage supplied from the main battery 52, thereby making the charging voltage of the sub-battery 53 higher than that of the main battery 52.

[0024] 1, the semiconductor switch 31 is configured with an n-channel MOSFET. The semiconductor switch 31 is connected between a connection point P1 on the wiring between the interrupter circuit 10 and the DC / DC converter 20 and a load 54. That is, the source terminal of the semiconductor switch 31 is connected to the interrupter circuit 10 side (connection point P1), and the drain terminal is connected to the load 54. Therefore, the parasitic diode 31a of the semiconductor switch 31 is connected such that the direction from the interrupter circuit 10 toward the load 54 is the forward direction.

[0025] The semiconductor switch 31 is normally kept on to pass current from the main battery 52 to the downstream load 54 etc. The semiconductor switch 31 is turned off when the voltage detection unit 11 detects that the main battery 52 has failed. 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).

[0026] The semiconductor switch 32 is configured with, for example, a MOSFET. In the circuit of Fig. 1, the semiconductor switch 32 is configured with a p-channel MOSFET. The semiconductor switch 32 is connected to a connection point P3 on a wiring between a connection point P2 on a wiring between the DC / DC converter 20 and a connection terminal to the sub-battery 53 and a load 54. In other words, 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 toward the sub-battery 53 is the forward direction.

[0027] The semiconductor switch 32 is normally in an OFF state, 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.

[0028] The IPDs 41 and 42 are an abbreviation for Intelligent Power Device, and are elements that integrate highly durable semiconductor switches and various protection / diagnosis circuits in one package. The IPDs 41 and 42 are also called semiconductor relays. The installation of the IPDs 41 and 42 is optional and does not have to be provided.

[0029] IPD 41 is provided in the rear stage of semiconductor switch 31, and is connected to load 55 to protect load 55 from overcurrent, etc. IPD 42 is provided in the front stage (main battery 52 side) of semiconductor switch 31, and is connected to load 56 to protect load 56 from overcurrent, etc. That is, IPD 42 is connected to load 56 (second load) in the front stage of semiconductor switch 31 (second semiconductor switch), and IPD 42 (protective element) is connected in the front stage of load 56.

[0030] The above-mentioned semiconductor switches, IPDs, and the like are controlled by a control unit (not shown) or the like that is provided separately and acquires the detection result of the voltage detection unit 11.

[0031] In the configuration of Fig. 1, the connection points P1 to P2 (DC / DC converter 20) form a first circuit 2 that connects the main battery 52 (first battery) and the sub-battery 53 (second battery) via the DC / DC converter 20. The connection points P1 to P3 form a second circuit 3 that connects the main battery 52 (first battery) and the load 54 (first load). The connection points P2 to P3 form a third circuit 4 that connects the sub-battery 53 (second battery) and the load 54 (first load) via the semiconductor switch 32 (first semiconductor switch).

[0032] The interrupter circuit 10 is connected between a main battery 52 (first battery) and the first circuit 2 and the second circuit 3.

[0033] Next, the operation of the power supply control circuit 1 configured as described above will be described with reference to Figures 2 and 3. Figure 2 is a diagram in which arrows indicating the flow of current during normal operation are added to Figure 1, and Figure 3 is a diagram in which arrows indicating the flow of current during power failure are added to Figure 1.

[0034] 2, the semiconductor switch 31 is turned on and the semiconductor switch 32 is turned off. The IPDs 41 and 42 are in a conducting state. Then, the loads 54, 55, and 56 are supplied with power from the main battery 52 and the alternator 51 (arrow A1). Meanwhile, the sub-battery 53 is charged by the boosted voltage from the DC / DC converter 20. Also, since the semiconductor switch 32 is turned off, power is not supplied from the sub-battery 53 to the load 54.

[0035] In addition, under normal circumstances, a voltage drop occurs due to the semiconductor switch 31. However, since the alternator 51 is connected, the main battery 52 is constantly charged. Therefore, there is almost no drop in the output voltage due to the discharge of the main battery 52, and the voltage supplied to the load 54 does not drop below the differential voltage.

[0036] On the other hand, in the event of a power failure such as an abnormality in the main battery 52 shown in Fig. 3, the semiconductor switch 31 is turned on and the semiconductor switch 32 is turned off. Then, power is supplied to the load 54 from the sub-battery 53 (arrow A2). On the other hand, the interrupter circuit 10 turns off the semiconductor switches 12 and 13 to interrupt 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.

[0037] Although the semiconductor switch 31 is turned off, the load 55 is connected to the rear stage of the semiconductor switch 31, and therefore, when the semiconductor switch 32 is turned on, power supply from the sub-battery 53 becomes possible (arrow A2). The load 56 is connected to the front stage (connection point P1 side) of the semiconductor switch 31, and therefore is not electrically connected to the sub-battery 53, and power supply stops.

[0038] According to this embodiment, the power supply control circuit 1 includes a first circuit 2 that connects the main battery 52 and the sub-battery 53 via the 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 a semiconductor switch 32. The semiconductor switch 32 is turned on when the main battery 52 fails to supply power from the sub-battery 53 to the load 54, and the parasitic diode 32a of the semiconductor switch 32 has a forward direction from the load 54 to the sub-battery 53. Furthermore, the DC / DC converter 20 boosts the voltage from the main battery 52 and supplies it to the sub-battery 53.

[0039] By configuring the power supply control circuit 1 as described above, in the third circuit 4, the sub-battery 53 and the load 54 are connected only via the semiconductor switch 32, so that the voltage drop can be reduced to about half that of a back-to-back connection, and the power supply time from the sub-battery 53 to the load 54 can be extended. In addition, since the power supply time is extended according to this embodiment, the configuration can be effective for continuing the system when the power source fails, which is a requirement for automatic driving, for example.

[0040] In addition, the parasitic diode 32a of the semiconductor switch 32 has a forward direction from the load 54 side to the sub-battery 53, and the DC / DC converter 20 boosts the voltage from the main battery 52 and supplies it to the sub-battery 53, so that the charging voltage of the sub-battery 53 is higher than that of the main battery 52, and current flow through the parasitic diode 32a can be prevented under normal circumstances.

[0041] The second circuit 3 also has a semiconductor switch 31 that connects the main battery 52 and the load 54, and the semiconductor switch 31 is turned off when the main battery 52 fails, and the parasitic diode 31a of the semiconductor switch 31 has a forward direction from the main battery 52 side to the load 54 side. In this way, when the main battery 52 fails, the electrical connection between the main battery 52 and the load 54 can be cut off even if there is a malfunction in the interrupter circuit 10.

[0042] In addition, the second circuit 3 is connected to the load 56 at the front stage of the second semiconductor switch. In this way, it is possible to electrically disconnect the load that does not need to be driven by the sub-battery 53. Therefore, it is 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. Therefore, since only the necessary loads are driven by the sub-battery 53, power consumption can be reduced and the power supply time can be extended.

[0043] Furthermore, an IPD 42 may be provided in front of the load 56. In this way, the load 56 can be protected from overcurrent and the like.

[0044] In addition, a cutoff circuit 10 that cuts off the electrode supply from the main battery 52 when the main battery 52 fails is connected between the main battery 52 and the first and second circuits 2 and 3. In this way, it is possible to cut off the power supply from the main battery 52 when the main battery 52 fails, such as when an abnormality occurs in the main battery 52.

[0045] The present invention is not limited to the above-described embodiment. In other words, a person skilled in the art can implement the present invention by modifying it in various ways in accordance with conventional knowledge without departing from the gist of the present invention. As long as the power supply control circuit configuration of the present invention is still included in such modifications, they are of course included in the scope of the present invention. [Explanation of symbols]

[0046] 1 Power supply control circuit 2 1st circuit 3 2nd circuit 4 Third circuit 10. Breaking Circuit 20 DC / DC converter 31 Semiconductor switch (second semiconductor switch) 32 Semiconductor switch (first semiconductor switch) 42 IPD (protective element) 52 Main battery (first battery) 53 Sub-battery (second battery) 54 Load 56 Load

Claims

1. a first circuit connecting the first battery and the second battery via a DC / DC converter; a second circuit connecting the first battery and a first load; a third circuit connecting the second battery and the first load via a first semiconductor switch; the first semiconductor switch is configured with one transistor, and is turned on when the first battery fails to supply power from the second battery to the first load; a parasitic diode of a transistor constituting the first semiconductor switch has a forward direction from the first load side to the second battery side, The DC / DC converter boosts a voltage from the first battery and supplies the boosted voltage to the second battery; the third circuit is provided with no semiconductor switch having a parasitic diode whose forward direction is from the second battery side to the first load side, either between the second battery and the first semiconductor switch or between the first semiconductor switch and the first load.

2. The second circuit includes a second semiconductor switch that connects the first battery and the first load. Has the second semiconductor switch is turned off when the first battery fails; 2. The power supply control circuit according to claim 1, wherein a parasitic diode of the second semiconductor switch has a forward direction from the first battery side to the first load side.

3. 3. The power supply control circuit according to claim 2, wherein the second circuit is connected to a second load at a stage preceding the second semiconductor switch.

4. 4. The power supply control circuit according to claim 3, further comprising a protection element provided in a stage preceding the second load.

5. 2. The power supply control circuit according to claim 1, further comprising a cutoff circuit connected between the first battery and the first circuit and between the first battery and the second circuit, the cutoff circuit cutting off power supply from the first battery when the first battery fails.

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