CN204613629U - A power relay control circuit - Google Patents

Abstract

The utility model relates to a kind of power relay control circuit, comprise: shunt, first power relay and the second power relay, the the first power relay controller controlling described first power relay is electrically connected with described first power relay, the the second power relay controller controlling described second power relay is electrically connected with described second power relay, with described shunt, described first power relay controller and described second power relay controller electrical connection are with the system controller sending control signals to described first power relay controller and described second power relay controller.Implement power relay control circuit of the present utility model, by adopting the first and second power relay controllers to assist control first and second power relay, therefore device cost is low, installing space is little and installation difficulty is little.

Description

A power relay control circuit

technical field

The utility model relates to the field of communication power supplies, in particular to a power relay control circuit.

Background technique

With the continuous development and progress of communication power supply technology, the power density of the rectifier module is getting higher and higher, and the volume is getting smaller and smaller. The miniaturization of communication power supply has become the future development trend. Therefore, the traditional power relay control circuit composed of contactors and shunts cannot meet the needs of miniaturization of the power system due to its high device cost, large installation space and difficult installation. Therefore, there is a need for a power relay control circuit with low component cost, small installation space and low installation difficulty.

Utility model content

The technical problem to be solved by the utility model is to provide a power relay control circuit with low device cost, small installation space and low installation difficulty for the defects of high device cost, large installation space and high installation difficulty in the prior art power relay control circuit. Relay control circuit.

The technical solution adopted by the utility model to solve the technical problem is: to construct a power relay control circuit, including: a shunt, a first power relay and a second power relay, electrically connected with the first power relay to control the The first power relay controller of the first power relay is electrically connected with the second power relay to control the second power relay controller of the second power relay, and the shunt and the first power relay control The controller and the second power relay controller are electrically connected to send control signals to a system controller of the first power relay controller and the second power relay controller.

In the power relay control circuit of the present invention, the first power relay controller includes a first signal relay; the second power relay controller includes a second signal relay.

In the power relay control circuit described in the present invention, the first end of the coil of the first signal relay is connected to the first control signal end of the system controller, and the second end is connected to the first control signal end of the system controller. The second control signal terminal, the moving contact of the first signal relay is connected to the system busbar output positive pole of the system controller, and the normally closed contact pin of the first signal relay is connected to the coil of the first power relay The first end of the coil of the first power relay is connected to the output negative pole of the system busbar, and the normally open contact of the first power relay is connected to the first end of the shunt and the system busbar Between the output negative poles of the row, the second end of the shunt is connected to the negative pole of the battery, the first end of the signal output of the shunt is connected to the first shunt signal end of the system controller, and the second end of the signal output is connected to The second shunt signal terminal of the system controller; the first terminal of the coil of the second signal relay is connected to the third control signal terminal of the system controller, and the second terminal is connected to the first terminal of the system controller Four control signal terminals, the moving contact of the second signal relay is connected to the system busbar output positive pole of the system controller, the normally closed contact pin of the second signal relay is connected to the coil of the second power relay The first end, the second end of the coil of the second power relay is connected to the output negative pole of the system busbar, and the normally open contact of the second power relay is connected between the non-important load and the output negative pole of the system busbar.

In the power relay control circuit described in the present invention, the power relay control circuit further includes a first freewheeling diode, a second freewheeling diode, a third freewheeling diode and a fourth freewheeling diode, the first freewheeling diode The anode of the freewheeling diode is connected to the second end of the coil of the first power relay, the cathode is connected to the first end of the coil of the first power relay, and the anode of the second freewheeling diode is connected to the first end of the first signal relay The second end and cathode of the coil are connected to the first end of the coil of the first signal relay, the anode of the third freewheeling diode is connected to the second end of the coil of the second power relay, and the cathode is connected to the second The first end of the coil of the power relay, the anode of the fourth freewheeling diode is connected to the second end of the coil of the second signal relay, and the cathode is connected to the first end of the coil of the second signal relay.

In the power relay control circuit described in the utility model, the power relay control circuit further includes a first current limiting resistor, a second current limiting resistor, a first voltage dividing resistor and a second voltage dividing resistor, the first limiting resistor The flow resistor is connected between the anode of the first freewheeling diode and the second end of the coil of the first power relay, and the first voltage dividing resistor is connected to the first control signal terminal and the first control signal terminal of the system controller. Between the first ends of the coil of the first signal relay, the second current limiting resistor is connected between the anode of the third freewheeling diode and the second end of the second power relay coil, the The second voltage dividing resistor is connected between the third control signal terminal of the system controller and the first terminal of the second signal relay coil.

In the power relay control circuit described in the present invention, the first power relay controller includes a first triode, a third voltage dividing resistor and a fourth voltage dividing resistor; the second power relay controller includes a first Two triodes, the fifth voltage dividing resistor and the sixth voltage dividing resistor.

In the power relay control circuit described in the present invention, the base of the first triode is connected to the second control signal terminal of the system controller, the emitter is connected to the output negative pole of the system busbar, and the collector is connected to the The first end of the coil of the first power relay, the second end of the coil of the first power relay is connected to the output positive pole of the system busbar, and the normally open contact of the first power relay is connected to the first terminal and the output negative pole of the system busbar, the second terminal of the shunt is connected to the negative pole of the battery, the first end of the signal output of the shunt is connected to the first shunt signal terminal of the system controller, and the signal The second output end is connected to the second shunt signal end of the system controller; the base of the second triode is connected to the fourth control signal end of the system controller, and the emitter is connected to the system busbar output negative pole, The collector is connected to the first end of the coil of the second power relay, the second end of the coil of the second power relay is connected to the output positive pole of the system busbar, and the normally open contact of the second power relay is connected to the load and Between the output negative poles of the system busbar; the third voltage dividing resistor is connected between the base of the first triode and the second control signal terminal of the system controller, and the fourth voltage dividing resistor The resistor is connected between the second control signal terminal of the system controller and the positive output pole of the system busbar, and the fifth voltage dividing resistor is connected to the base of the second triode and the system controller Between the fourth control signal terminals of the system controller, the sixth voltage dividing resistor is connected between the fourth control signal terminal of the system controller and the positive output pole of the system busbar.

In the power relay control circuit described in the present invention, the power relay control circuit includes a first freewheeling diode, a first current limiting resistor, a second freewheeling diode and a second current limiting resistor, and the first freewheeling The anode of the diode is connected to the first end of the first power relay coil, the cathode is connected to the second end of the first power relay coil through the first current limiting resistor, and the anode of the second freewheeling diode is connected to the first end of the first power relay coil. The first end and cathode of the second power relay coil are connected to the second end of the second power relay coil through the second current limiting resistor.

In the power relay control circuit described in the present invention, the shunt, the first power relay, the second power relay, the first power relay controller, the second power relay controller and The system controller is integrated on a printed circuit board.

The power relay control circuit implementing the utility model adopts the first and second power relay controllers to assist in controlling the first and second power relays, so the device cost is low, the installation space is small and the installation difficulty is small. Furthermore, by using a signal relay or a triode as a power relay controller, the cost of the device is lower, the circuit is simpler, and the process is better. Further, by using the freewheeling diode and the current limiting resistor, not only the damage to the system when the relay coil is powered off is eliminated, but also the influence of lightning strikes and surges on the freewheeling diode is prevented. Further, by using the voltage dividing resistor, the selection range of the rated operating voltage of the signal relay coil is widened, so that a lower-cost relay can be used to realize the control function of the power relay shown.

Description of drawings

The utility model will be further described below in conjunction with accompanying drawing and embodiment, in the accompanying drawing:

Fig. 1 is the system block diagram of the power relay control circuit of the present utility model;

Fig. 2 is the circuit diagram of the first embodiment of the power relay control circuit of the present utility model;

Fig. 3 is the circuit diagram of the second embodiment of the power relay control circuit of the present invention;

Fig. 4 is the circuit diagram of the third embodiment of the power relay control circuit of the present utility model;

Fig. 5 is a circuit diagram of the fourth embodiment of the power relay control circuit of the present invention.

Detailed ways

Fig. 1 is a system block diagram of the power relay control circuit of the present invention. As shown in FIG. 1 , the power relay control circuit includes a shunt RL1 , a first power relay RLY1 and a second power relay RLY2 , a first power relay controller 20 and a second power relay controller 30 , and a system controller 10 . As shown in FIG. 1, the system controller 10 is electrically connected to the first power relay controller 20 and the second power relay controller 30 to send control signals to the first power relay controller 20 and the second power relay controller respectively. Power relay controller 30. The first power relay controller 20 is electrically connected with the first power relay RLY1 to control the first power relay RLY1. The second power relay controller 30 is electrically connected with the second power relay RLY2 to control the second power relay RLY2. The shunt RL1 is electrically connected to the system controller 10 to receive the shunt sampling signal.

When the power system is working normally, the first power relay controller 20 controls the first power relay RLY1 to close, and the second power relay controller 30 controls the second power relay RLY2 to close, and then connects the main circuit . When the power supply system needs to start battery protection, the system controller 10 sends a first power-off control signal, and based on the first power-off control signal, the second power relay controller 30 controls the second power The relay RLY2 is opened, thereby disconnecting the non-essential load branch. Similarly, the system controller 10 can send a second power-off control signal, and based on the second power-off control signal, the first power relay controller 20 controls the first power relay RLY1 to turn off, thereby turning off Open important load branches, so that the system is powered off.

In the present invention, any power relay controller can be used as the first power relay controller 20 and the second power relay controller 30 of the present invention, such as switch tube, signal relay, switch circuit and so on. Those skilled in the art can use any known switching devices and/or switching circuits in the art. In the present utility model, the shunt RL1, the first power relay RLY1, the second power relay RLY2, the first power relay controller, the second power relay controller and the system control The device 10 can be integrated on the printed circuit board, so as to further reduce the installation space, shorten the installation time, reduce the cost and improve the efficiency.

The power relay control circuit implementing the utility model adopts the first and second power relay controllers to assist in controlling the first and second power relays, so the device cost is low, the installation space is small and the installation difficulty is small.

Fig. 2 is a circuit diagram of the first embodiment of the power relay control circuit of the present invention. As shown in FIG. 2 , the power relay control circuit includes a shunt RL1 , a first power relay RLY1 and a second power relay RLY2 , a first signal relay RLY3 and a second signal relay RLY4 and a system controller 10 . As shown in FIG. 2, the first end of the coil of the first signal relay RLY3 is connected to the first control signal end LVD1+ of the system controller 10, and the second end is connected to the second control signal end of the system controller 10. The signal terminal LVD1- is used to receive the power-off control signal. The moving contact of the first signal relay RLY3 is connected to the system busbar output positive pole BUS+ of the system controller 10, and the normally closed contact pin of the first signal relay RLY3 is connected to the coil of the first power relay RLY1. first end. The second end of the coil of the first power relay RLY1 is connected to the output negative pole BUS- of the system bus bar. The normally open contact of the first power relay RLY1 is connected between the first end of the shunt RL1 and the system busbar output negative pole BUS−. The second end of the shunt RL1 is connected to the negative pole of the battery, the first end of the signal output of the shunt RL1 is connected to the first shunt signal end RL+ of the system controller 10, and the second end of the signal output is connected to the system The second shunt signal terminal RL− of the controller 10 receives the shunt signal. The first end of the coil of the second signal relay RLY4 is connected to the third control signal end LVD2+ of the system controller 10, and the second end is connected to the fourth control signal end LVD2- of the system controller 10 to receive Power down control signal. The moving contact of the second signal relay RLY4 is connected to the system busbar output positive pole BUS+ of the system controller 10, and the normally closed contact pin of the second signal relay RLY4 is connected to the coil of the second power relay RLY2. first end. The second end of the coil of the second power relay RLY2 is connected to the system busbar output negative pole BUS-, and the normally open contact of the second power relay RLY2 is connected between the load NPL and the system busbar output negative pole BUS- . The system busbar output negative pole BUS- can be connected to an important load, and the load NPL is a non-important load.

In this embodiment, the first signal relay RLY3 and the second signal relay RLY4 are used to control the first power relay RLY1 and the second power relay RLY2 respectively. The shunt RL1 samples the charging and discharging current of the battery and feeds it back to the system controller 10 . The first control signal terminal LVD1+ and the second control signal terminal LVD1- of the system controller 10 output a power-off control signal, so as to control the first power relay RLY1 through the first signal relay RLY3. The third control signal terminal LVD2+ and the fourth control signal terminal LVD2- of the system controller 10 output a power-off control signal, so as to control the second power relay RLY2 through the second signal relay RLY4.

When the power system works normally, the voltages at both ends of the first control signal terminal LVD1+, the second control signal terminal LVD1-, the third control signal terminal LVD2+ and the fourth control signal terminal LVD2- are all 0V. The normally closed contacts of the first signal relay RLY3 and the second signal relay RLY4 remain in the closed state, and the coils of the first power relay RLY1 and the second power relay RLY2 are energized, so their normally open contacts are closed and the main power circuit is connected.

When the power system needs to start battery protection, the third control signal terminal LVD2+ and the fourth control signal terminal LVD2- firstly provide a power-off control signal. The second signal relay RLY4 operates, its normally closed contact pin is disconnected, and the voltage of the coil of the second power relay RLY2 is cut off, so that its normally open contact is disconnected, and the non-important load branch is disconnected. Similarly, when the first control signal terminal LVD1+ and the second control signal terminal LVD1- give a power-off control signal, the battery circuit will be cut off, the important load branch circuit will be disconnected, and the system will be powered off.

In the present utility model, the shunt RL1, the first power relay RLY1, the second power relay RLY2, the first signal relay RLY3, the second signal relay RLY4 and the system controller 10 can be integrated in the printed On the circuit board, thereby further reducing the installation space, shortening the installation time, reducing costs and improving efficiency.

In implementing the power relay control circuit of the utility model, by using the signal relay as the power relay controller, the device cost is lower, the circuit is simpler, and the process is better.

Fig. 3 is a circuit diagram of the second embodiment of the power relay control circuit of the present invention. The embodiment shown in Figure 3 is similar to the first embodiment of the power relay control circuit shown in Figure 2, the difference is that the power relay control circuit shown in Figure 3 further includes a freewheeling diode D1, a freewheeling diode D3, a continuous Freewheeling diode D2 and freewheeling diode D4. The anode of the freewheeling diode D1 is connected to the second end of the coil of the first power relay RLY1 , and the cathode is connected to the first end of the coil of the first power relay RLY1 . The anode of the freewheeling diode D3 is connected to the second end of the coil of the first signal relay RLY3, and the cathode is connected to the first end of the coil of the first signal relay RLY3. The anode of the freewheeling diode D2 is connected to the second end of the coil of the second power relay RLY2, and the cathode is connected to the first end of the coil of the second power relay RLY2. The anode of the freewheeling diode D4 is connected to the second end of the coil of the second signal relay RLY4 , and the cathode is connected to the first end of the coil of the second signal relay RLY4 of the system.

In the present utility model, the shunt RL1, the first power relay RLY1, the second power relay RLY2, the first signal relay RLY3, the second signal relay RLY4 and the system controller 10, and the The freewheeling diodes D1-D4 can be integrated on the printed circuit board, thereby further reducing the installation space, shortening the installation time, reducing the cost and improving the efficiency.

In implementing the power relay control circuit of the utility model, by using the signal relay as the power relay controller, the device cost is lower, the circuit is simpler, and the process is better. Further, by using the freewheeling diode, the reverse overvoltage when the relay coil is de-energized can be eliminated, thereby avoiding damage to the system.

Fig. 4 is a circuit diagram of the third embodiment of the power relay control circuit of the present invention. The embodiment shown in Figure 4 is similar to the second embodiment of the power relay control circuit shown in Figure 3, the difference is that the power relay control circuit shown in Figure 4 further includes a current limiting resistor R9, a voltage dividing resistor R1, a limiting Flow resistor R10 and voltage divider resistor R5. The current limiting resistor R9 is connected between the anode of the freewheeling diode D1 and one end of the coil of the first power relay RLY1, and the voltage dividing resistor R1 is connected to the first control signal terminal of the system controller 10 Between LVD1+ and one end of the coil of the first signal relay RLY3, the current limiting resistor R10 is connected between the anode of the freewheeling diode D2 and one end of the coil of the second power relay RLY2, and the protection resistor R5 It is connected between the third control signal terminal LVD2+ of the system controller 10 and one end of the coil of the second signal relay RLY4.

In this embodiment, since the current limiting resistors R9 and R10 are set, it can protect the freewheeling diodes D1 and D2 from being damaged when the DC side of the system is struck by lightning and surges; the voltage dividing resistors R1 and R5 can make the The signal voltage output by the first control signal terminal LVD1+, second control signal terminal LVD1-, third control signal terminal LVD2+ and fourth control signal terminal LVD2- of the system controller 10 is higher than the rated work of the coils of the signal relays RLY3 and RLY4 Voltage can also be used normally.

In the present utility model, the shunt RL1, the first power relay RLY1, the second power relay RLY2, the first signal relay RLY3, the second signal relay RLY4, the system controller 10, the The freewheeling diodes D1-D4, the voltage dividing resistors (R1, R5), and the current limiting resistors (R10, R9) can be integrated on the printed circuit board, thereby further reducing the installation space, shortening the installation time, reducing costs and improving efficiency .

In implementing the power relay control circuit of the utility model, by using the signal relay as the power relay controller, the device cost is lower, the circuit is simpler, and the process is better. Further, by using the freewheeling diode and the protection resistor, not only can the reverse overvoltage when the relay coil is de-energized, thereby avoiding damage to the system, but also prevent lightning strikes and surges from affecting the freewheeling diode.

Fig. 5 is a circuit diagram of the fourth embodiment of the power relay control circuit of the present invention. As shown in FIG. 5 , the power relay control circuit includes a shunt RL1 , a first power relay RLY1 and a second power relay RLY2 , a transistor Q1 , a transistor Q2 , voltage dividing resistors R1 - R4 and a system controller 10 . The voltage dividing resistor R3 is connected between the base of the triode Q1 and the second control signal terminal LVD1- of the system controller 10, and the voltage dividing resistor R1 is connected to the second control signal terminal LVD1- of the system controller 10. Between the control signal terminal LVD1- and the system busbar output positive pole BUS+, the voltage dividing resistor R4 is connected between the base of the triode Q2 and the fourth control signal terminal LVD2- of the system controller 10, The voltage dividing resistor R2 is connected between the fourth control signal terminal LVD2 − of the system controller 10 and the positive output terminal BUS+ of the system busbar. The emitter of the transistor Q1 is connected to the system busbar output negative pole BUS-, and the collector of the transistor Q1 is connected to the first end of the coil of the first power relay RLY1. The second end of the coil of the first power relay RLY1 is connected to the output positive pole BUS+ of the system busbar, and the normally open contact of the first power relay RLY1 is connected to the first end of the shunt RL1 and the system busbar Between the output negative pole BUS-. The second end of the shunt RL1 is connected to the negative pole of the battery, the first end of the signal output of the shunt RL1 is connected to the first shunt signal end RL+ of the system controller 10, and the second end of the signal output is connected to the The second shunt signal terminal RL- of the system controller 10 . The emitter of the transistor Q2 is connected to the system busbar output negative pole BUS-, and the collector of the transistor Q2 is connected to the first end of the coil of the second power relay RLY2. The second end of the coil of the second power relay RLY2 is connected to the system busbar output positive pole BUS+, and the normally open contact of the second power relay RLY2 is connected between the load NPL and the system busbar output negative pole BUS-.

In the preferred embodiment shown in Figure 5, the power relay control circuit further includes a freewheeling diode D1, a current limiting resistor R9, a freewheeling diode D2 and a current limiting resistor R10, and the anode of the freewheeling diode D1 is connected to the first One end and the cathode of a power relay RLY1 coil are connected to the other end of the first power relay RLY1 coil through the current limiting resistor R9, and the anode of the freewheeling diode D2 is connected to one end of the second power relay RLY2 coil, and the cathode is connected to the other end of the coil of the second power relay RLY2 through the current limiting resistor R9. The current limiting resistor R10 is connected to the other end of the coil of the second power relay RLY2. It can be seen from the embodiment shown in FIG. 2 that in the simplified embodiment of the present invention, the freewheeling diode D1, the current limiting resistor R9, the freewheeling diode D2 and the current limiting resistor R10 can be omitted.

In the embodiment shown in FIG. 5 , triodes Q1 and Q2 are used instead of signal relays to control the first and second power relays RLY1 and RLY2 . When the system is normal, the second control signal terminal LVD1- and the fourth control signal terminal LVD2-, under the action of the voltage dividing resistors R1, R3 and R2, R4, the transistors Q1 and Q2 are in a saturated conduction state. The first and second power relays RLY1 and RLY2 are turned on to connect the main power circuit. When the power supply system needs to start battery protection, the fourth control signal terminal LVD2- first gives a control signal, the transistor Q2 is cut off, and the coil voltage of the second power relay RLY2 is switched, causing its normally open contact to be disconnected, breaking non-important loads Similarly, when the second control signal terminal LVD1- gives a control signal, the battery circuit is cut off, the important load branch is cut off, and the system is powered off.

In implementing the power relay control circuit of the utility model, by using the triode as the power relay controller, the device cost is lower, the circuit is simpler, and the process is better. Furthermore, by using freewheeling diodes and voltage dividing resistors, not only eliminates the damage to the system when the relay coil is powered off, but also prevents lightning strikes and surges from affecting the freewheeling diodes.

Although the utility model is described through specific embodiments, those skilled in the art should understand that various changes and equivalent substitutions can be made to the present invention without departing from the scope of the present invention. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but should include all implementations falling within the scope of the appended claims.

Claims (9)

1. A power relay control circuit, characterized in that it comprises: a shunt, a first power relay and a second power relay, electrically connected to the first power relay to control the first power relay of the first power relay a controller, a second power relay controller electrically connected to the second power relay to control the second power relay, and the shunt, the first power relay controller and the second power relay control A system controller electrically connected to send control signals to the first power relay controller and the second power relay controller. 2. The power relay control circuit according to claim 1, wherein the first power relay controller comprises a first signal relay; the second power relay controller comprises a second signal relay. 3. The power relay control circuit according to claim 2, wherein the first end of the coil of the first signal relay is connected to the first control signal end of the system controller, and the second end is connected to the The second control signal terminal of the system controller, the moving contact of the first signal relay is connected to the system busbar output positive pole of the system controller, and the normally closed contact pin of the first signal relay is connected to the first The first end of the coil of a power relay, the second end of the coil of the first power relay is connected to the output negative pole of the system busbar, and the normally open contact of the first power relay is connected to the first end of the shunt Between the output negative pole of the system busbar, the second end of the shunt is connected to the negative pole of the battery, the first end of the signal output of the shunt is connected to the first shunt signal end of the system controller, and the The second end of the shunt signal output is connected to the second shunt signal end of the system controller; the first end of the coil of the second signal relay is connected to the third control signal end of the system controller, the second The terminal is connected to the fourth control signal terminal of the system controller, the moving contact of the second signal relay is connected to the system busbar output positive pole of the system controller, the normally closed contact pin of the second signal relay Connect the first end of the coil of the second power relay, the second end of the coil of the second power relay is connected to the output negative pole of the system busbar, and the normally open contact of the second power relay is connected to the unimportant Between the load and the output negative pole of the system busbar. 4. The power relay control circuit according to claim 3, wherein the power relay control circuit further comprises a first freewheeling diode, a second freewheeling diode, a third freewheeling diode and a fourth freewheeling diode, The anode of the first freewheeling diode is connected to the second end of the coil of the first power relay, the cathode is connected to the first end of the coil of the first power relay, and the anode of the second freewheeling diode is connected to the The second end and the cathode of the coil of the first signal relay are connected to the first end of the coil of the first signal relay, and the anode of the third freewheeling diode is connected to the second end and the cathode of the coil of the second power relay The first end of the coil of the second power relay is connected, the anode of the fourth freewheeling diode is connected to the second end of the coil of the second signal relay, and the cathode is connected to the first end of the coil of the second signal relay. 5. The power relay control circuit according to claim 4, wherein the power relay control circuit further comprises a first current limiting resistor, a second current limiting resistor, a first voltage dividing resistor and a second voltage dividing resistor, The first current limiting resistor is connected between the anode of the first freewheeling diode and the second end of the coil of the first power relay, and the first voltage dividing resistor is connected to the first end of the system controller. Between a control signal end and the first end of the coil of the first signal relay, the second current limiting resistor is connected to the anode of the third freewheeling diode and the second end of the second power relay coil Between, the second voltage dividing resistor is connected between the third control signal terminal of the system controller and the first terminal of the second signal relay coil. 6. The power relay control circuit according to claim 1, wherein the first power relay controller comprises a first triode, a third voltage dividing resistor and a fourth voltage dividing resistor; the second power The relay controller includes a second triode, a fifth voltage dividing resistor and a sixth voltage dividing resistor. 7. The power relay control circuit according to claim 6, wherein the base of the first triode is connected to the second control signal terminal of the system controller, the emitter is connected to the output negative pole of the system busbar, The collector is connected to the first end of the coil of the first power relay, the second end of the coil of the first power relay is connected to the output positive pole of the system busbar, and the normally open contact of the first power relay is connected to the Between the first end of the shunt and the output negative pole of the system busbar, the second end of the shunt is connected to the negative pole of the battery, and the first end of the signal output of the shunt is connected to the first end of the system controller. A shunt signal terminal, the second end of the shunt signal signal output is connected to the second shunt signal end of the system controller; the base of the second triode is connected to the fourth control signal of the system controller terminal, the emitter is connected to the system busbar output negative pole, the collector is connected to the first end of the coil of the second power relay, the second end of the coil of the second power relay is connected to the system busbar output positive pole, and the second The normally open contact of the power relay is connected between the load and the output negative pole of the system busbar; the third voltage dividing resistor is connected to the base of the first triode and the second control of the system controller Between the signal terminals, the fourth voltage dividing resistor is connected between the second control signal terminal of the system controller and the positive output pole of the system busbar, and the fifth voltage dividing resistor is connected to the second three Between the base of the pole tube and the fourth control signal terminal of the system controller, the sixth voltage dividing resistor is connected between the fourth control signal terminal of the system controller and the positive output terminal of the system busbar . 8. The power relay control circuit according to claim 7, wherein the power relay control circuit comprises a first freewheeling diode, a first current limiting resistor, a second freewheeling diode and a second current limiting resistor, the The anode of the first freewheeling diode is connected to the first end of the first power relay coil, the cathode is connected to the second end of the first power relay coil through the first current limiting resistor, and the second freewheeling diode The anode is connected to the first end of the second power relay coil, and the cathode is connected to the second end of the second power relay coil through the second current limiting resistor. 9. The power relay control circuit according to any one of claims 1-8, wherein the shunt, the first power relay, the second power relay, the The first power relay controller, the second power relay controller and the system controller are integrated on a printed circuit board.