Reliability detection circuit for power relays

Abstract

The application provides a reliability detection circuit of a power relay, which comprises an isolated signal transmission unit, a resistance unit and a signal analysis unit. The isolated signal transmission unit comprises a primary side and a secondary side which are isolated from each other. The resistance unit is connected in series with the primary side of the isolated signal transmission unit, and then connected between the common node between the first power relay and the first terminal of the alternating-current port and the common node between the second power relay and the second terminal of the alternating-current port. The secondary side of the isolated signal transmission unit outputs a voltage detection signal. The signal analysis unit receives the voltage detection signal and an alternating-current output voltage indication signal, and outputs a state indication signal indicating the state of the power relay according to the voltage detection signal and the alternating-current output voltage indication signal. The alternating-current output voltage indication signal is a signal used for indicating the alternating-current voltage output by the power converter.

Description

Technical Field

[0001] This application relates to the field of power supplies, and in particular to reliability detection circuits for power relays. Background Technology

[0002] With the development of technology and market demand, electric vehicles are becoming increasingly popular.

[0003] Currently, electric vehicles on the market typically include a high-voltage battery cell and a bidirectional AC / DC converter. (See also...) Figure 1 The diagram shows a typical partial circuit diagram inside an electric vehicle. The DC terminal of the bidirectional AC / DC converter 210 is connected to the high-voltage battery unit HV. The first AC terminal dac1 is connected to the first terminal AC1 of the AC port through the first power relay RL1. The second AC terminal dac2 is connected to the second terminal AC2 of the AC port through the second power relay RL2. That is, the first terminal AC1 and the second terminal AC2 form an AC port, which is used to connect an AC source or an AC load. Figure 1 Taking the connection of the AC port to the AC source (AC) as an example.

[0004] In practical applications, when the bidirectional AC / DC converter 210 operates in charging mode, it converts AC power into DC power to charge the high-voltage battery unit HV; when operating in inverter mode, it can convert the electrical energy of the high-voltage battery unit HV into AC power to regulate the power grid or to power loads on electric vehicles (such as vehicle refrigerators).

[0005] In practical applications, the AC terminals of the bidirectional AC / DC converter 210 are connected to or disconnected from the AC port by controlling the opening or closing of the first power relay RL1 and the second power relay RL2. However, in reality, due to various reasons, the first power relay RL1 and the second power relay RL2 are prone to malfunctions such as sticking together.

[0006] Therefore, in practical applications, it is necessary to test whether the power relays (such as the first power relay RL1 and the second power relay RL2 mentioned above) can work reliably, such as whether they can close and open reliably. Utility Model Content

[0007] According to one embodiment, this application provides a reliability detection circuit for a power relay, wherein the power relay includes a first power relay and a second power relay. The first power relay is connected between a first AC terminal of a power converter and a first terminal of an AC port, and the second power relay is connected between a second AC terminal of the power converter and a second terminal of the AC port. The circuit is characterized by comprising: an isolation signal transmission unit, including a primary side and a secondary side isolated from each other; a resistor unit, which is connected in series with the primary side of the isolation signal transmission unit and then connected between a common node between the first power relay and the first terminal of the AC port and a common node between the second power relay and the second terminal of the AC port; the secondary side of the isolation signal transmission unit outputs a voltage detection signal; and a signal analysis unit, which receives the voltage detection signal and an AC output voltage indication signal, and outputs a status indication signal indicating the state of the power relay based on the voltage detection signal and the AC output voltage indication signal, wherein the AC output voltage indication signal is a signal used to indicate the AC voltage output by the power converter.

[0008] Furthermore, the isolated signal transmission unit includes: a light-emitting diode forming the primary side of the isolated signal transmission unit; a phototransistor forming the secondary side of the isolated signal transmission unit, wherein the collector of the phototransistor is connected to a voltage source, the emitter of the phototransistor is grounded, and the collector of the phototransistor outputs the voltage detection signal.

[0009] Furthermore, the isolated signal transmission unit also includes a second light-emitting diode, which is connected in anti-parallel with the first light-emitting diode.

[0010] Furthermore, the resistor unit includes: a first resistor unit connected between the primary side of the isolation signal transmission unit and the common node between the first power relay and the first terminal of the AC port; and a second resistor unit connected between the primary side of the isolation signal transmission unit and the common node between the second power relay and the second terminal of the AC port.

[0011] Furthermore, the resistance value of the resistor unit is selected such that at least one light-emitting diode in the optocoupler is turned on and the phototransistor is turned on within at least one interval where there is a first AC current between the first terminal and the second terminal of the AC port.

[0012] Furthermore, the signal analysis unit is configured such that when the AC output voltage indication signal indicates that the power converter outputs a first AC current and the voltage detection signal is at a first level, the status indication signal output by the signal analysis unit indicates that the power relay is reliably closed.

[0013] Furthermore, the signal analysis unit is configured such that when the AC output voltage indication signal indicates that the power converter outputs a first AC current and the voltage detection signal is at a second level, the status indication signal output by the signal analysis unit indicates that the power relay is reliably disconnected.

[0014] Furthermore, the power converter is a bidirectional AC / DC converter used in electric vehicles.

[0015] Furthermore, the DC end of the bidirectional AC / DC converter is connected to a high-voltage power battery.

[0016] Furthermore, the amplitude of the first AC current is lower than that of the 220V AC current.

[0017] This application also provides an electric vehicle including the aforementioned bidirectional AC / DC converter 210.

[0018] The features and technical advantages of this disclosure have been outlined quite extensively above to facilitate a better understanding of the detailed description that follows. Additional features and advantages of this disclosure, which form the subject matter of the claims, will be described below. Those skilled in the art will understand that the disclosed concepts and specific embodiments can be readily used as the basis for modifying or designing other structures or processes to achieve the same purpose as this disclosure. Those skilled in the art will also recognize that such equivalent structures do not depart from the spirit and scope of this disclosure as set forth in the appended claims. Attached Figure Description

[0019] To gain a more complete understanding of this disclosure and its advantages, the following description is given in conjunction with the accompanying drawings, wherein:

[0020] Figure 1 A schematic diagram of a typical circuit in an electric vehicle is shown.

[0021] Figure 2 A schematic diagram of a reliability detection circuit for a power relay according to an embodiment of this application is shown;

[0022] Figure 3 A schematic diagram of a reliability detection circuit for a power relay according to a specific embodiment of this application is shown;

[0023] Figure 4 A schematic diagram of a reliability detection circuit for a power relay according to another specific embodiment of this application is shown;

[0024] Figure 5 A schematic diagram of the operating waveform of a power relay for detecting reliability according to an embodiment of this application is shown.

[0025] Unless otherwise stated, corresponding numbers and symbols in the various figures generally refer to corresponding parts. These figures are drawn to clearly illustrate relevant aspects of the various embodiments and are not necessarily drawn to scale. Detailed Implementation

[0026] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] One embodiment of this application provides a reliability detection circuit for a power relay, which can be found in [reference needed]. Figure 2 The diagram shown is a schematic of a reliability detection circuit for a power relay according to an embodiment of this application. Please refer to it in conjunction with... Figure 1 The power relay includes a first power relay RL1 and a second power relay RL2. The first power relay RL1 is connected between the first AC terminal dac1 of the power converter 200 and the first terminal AC1 of the AC port. The second power relay RL2 is connected between the second AC terminal dac2 of the power converter 200 and the second terminal AC2 of the AC port. An embodiment of the power relay reliability detection circuit of this application includes:

[0028] The isolation signal transmission unit 310 includes a primary side and a secondary side that are isolated from each other;

[0029] The resistor unit 320 is connected in series with the primary side of the isolation signal transmission unit 310 and is connected between the common node d1 between the first power relay RL1 and the first terminal AC1 of the AC port and the common node d2 between the second power relay RL2 and the second terminal AC2 of the AC port. The secondary side of the isolation signal transmission unit 310 outputs a voltage detection signal Vs.

[0030] The signal analysis unit 330 receives the voltage detection signal Vs and the AC output voltage indication signal Sf, and outputs a status indication signal SRf indicating the state of the power relay based on the voltage detection signal Vs and the AC output voltage indication signal Sf, wherein the AC output voltage indication signal Sf is a signal used to indicate the AC voltage output by the power converter 200.

[0031] Please see Figure 3 The schematic diagram shown is of a reliability detection circuit for a power relay according to a specific embodiment of this application. The isolation signal transmission unit 310 is implemented as an optocoupler. Figure 3As shown, the isolation signal transmission unit 310 includes: a light-emitting diode D1, forming the primary side of the isolation signal transmission unit 310; a phototransistor S1, forming the secondary side of the isolation signal transmission unit 310, the collector of the phototransistor S1 is connected to a voltage source VCC, the emitter of the phototransistor S1 is grounded, and the collector of the phototransistor S1 outputs the voltage detection signal Vs.

[0032] Please see Figure 4 The schematic diagram shown here is a reliability detection circuit diagram of a power relay according to another specific embodiment of this application. The optocoupler is implemented as including two anti-parallel light-emitting diodes, that is, in Figure 3 Based on the above, the isolation signal transmission unit 310 further includes a second light-emitting diode D2, which is connected in anti-parallel with the light-emitting diode D1.

[0033] Please refer to the following: Figure 3 Resistor unit 320 is implemented as the first resistor R1. Please refer to [further details]. Figure 4 The resistor unit 320 is implemented as a first resistor R1 and a second resistor R2, both of which are connected in series with the light-emitting diode in the optocoupler. Specifically, the first resistor R1 is connected between the primary side of the isolation signal transmission unit 310 and the common node d1 between the first power relay RL1 and the first terminal AC1 of the AC port; the second resistor R2 is connected between the primary side of the isolation signal transmission unit 310 and the common node d2 between the second power relay RL2 and the second terminal AC2 of the AC port. In practical applications, the first resistor R1 and the second resistor R2 can be implemented as a single resistor or as multiple resistors connected in series and parallel. That is, this application does not limit the specific structure of the resistor unit 320, as long as it forms an impedance connected in series with the light-emitting diode in the optocoupler.

[0034] for Figure 3 and Figure 4 In one embodiment, the resistance value of the resistor unit 320 is selected such that at least one light-emitting diode D1 in the optocoupler is turned on and the phototransistor S1 is turned on within at least one interval where there is a first AC current between the first terminal AC1 and the second terminal AC2 of the AC port.

[0035] Furthermore, such as Figure 3 and 4As shown, the power converter 200 is implemented as a bidirectional AC / DC converter 210, specifically, it can be an on-board charger in an electric vehicle, with its DC terminal connected to the high-voltage battery unit HV. When the high-voltage battery unit HV needs charging, the bidirectional AC / DC converter 210 operates in AC-DC conversion mode, that is, converting the AC power (220V AC power from the grid) at the AC port into DC power to charge the high-voltage battery unit HV. When the high-voltage battery unit HV needs discharging or needs to supply power to loads outside or inside the electric vehicle, the bidirectional AC / DC converter 210 operates in DC-AC inverter mode, that is, converting the electrical energy of the high-voltage battery unit HV into 220V AC power to supply power to AC loads (such as the grid or in-vehicle electrical equipment such as a car refrigerator).

[0036] In practical applications, such as Figure 4 As shown, the controller 220 controls the bidirectional AC / DC converter 210 to operate in the AC-DC conversion mode or DC-AC inverter mode described above.

[0037] In actual operation, before the bidirectional AC / DC converter 210 operates in the aforementioned inverter mode, the controller 220 also controls the bidirectional AC / DC converter 210 to operate in the initial inverter mode of converting DC power into first AC power, wherein the amplitude of the first AC power is lower than the amplitude of 220V AC power, such as the first AC power being 30V AC power.

[0038] The following will use a 30V AC power supply and an isolation signal transmission unit 310 as an example to explain the principle of the reliability detection circuit of this application for detecting the reliability of the first power relay RL1 and the second power relay RL2.

[0039] For details, please refer to Figure 4 Please see Figure 5 The diagram shown is a schematic representation of the operating waveform of a power relay used for reliability detection according to an embodiment of this application. Figure 5 As shown, in actual operation, the controller 220 can be configured such that when the controller 220 controls the bidirectional AC / DC converter 210 to operate in the initial inverter mode of outputting the first AC power VAC, the AC output voltage indication signal Sf output by the controller 220 is at a high level; when the controller 220 controls the bidirectional AC / DC converter 210 to operate in the output 220V AC power or AC-DC conversion mode, the AC output voltage indication signal Sf output by the controller 220 is at a low level.

[0040] If the first power relay RL1 and the second power relay RL2 are selected as normally closed relays, such as Figure 5As shown, if the AC output voltage indication signal Sf is high (i.e., the bidirectional AC / DC converter 210 outputs 30V AC), the control signal Sr of the first power relay RL1 and the second power relay RL2 is low (i.e., the first power relay RL1 and the second power relay RL2 should be closed). For Figure 4 If the first power relay RL1 and the second power relay RL2 are reliably closed, the first AC current VAC output by the bidirectional AC / DC converter 210 will be transmitted to the AC port through the closed first power relay RL1 and the second power relay RL2. As described above, the resistor unit 320 is selected such that in at least one interval between the first terminal AC1 and the second terminal AC2 of the AC port, which is the first AC current VAC, the light-emitting diode D1 in the optocoupler is turned on, and the phototransistor S1 is turned on, pulling the collector of the phototransistor S1 low. Figure 5 As shown, during the time interval t1 to t2 of the positive half-cycle of the first AC current VAC, the voltage detection signal Vs is at a low level, and during other time intervals of the first AC current, the light-emitting diode D1 is cut off, and the voltage detection signal Vs is at a high level.

[0041] Furthermore, the signal analysis unit 330 is configured such that when the AC output voltage indication signal Sf is high (indicating that the power converter 200 outputs a first AC VAC) and the voltage detection signal Vs is at a first level (low level), the status indication signal SRf output by the signal analysis unit 330 is high (indicating that the power relay is reliably closed), as shown below. Figure 5 As shown, during the time interval from t1 to t2, the status indicator signal SRf is at a high level, meaning that the power relay can reliably close.

[0042] Specifically, such as Figure 5 As shown, the time interval from t1 to t2 is the interval in which the amplitude of the first AC current VAC is greater than the voltage V1. During this interval, the current formed by the first AC current VAC applied to the resistor unit 320 is sufficient to turn on the light-emitting diode and the phototransistor S1.

[0043] like Figure 5 As shown, if the AC output voltage indication signal Sf is high (i.e., the bidirectional AC / DC converter 210 outputs 30V AC), the control signals Sr for the first power relay RL1 and the second power relay RL2 are disconnected, meaning the control signals Sr for the first power relay RL1 and the second power relay RL2 become high (i.e., the first power relay RL1 and the second power relay RL2 should be disconnected). For Figure 3If the first power relay RL1 and the second power relay RL2 are reliably disconnected, the first AC power VAC output from the bidirectional AC / DC converter 210 will not be able to be transmitted to the AC port. Figure 3 As shown, the light-emitting diode D1 in the optocoupler will be turned off, which will also turn off the phototransistor S1, so the voltage detection signal Vs will always be high.

[0044] Furthermore, the signal analysis unit 330 is configured such that when the AC output voltage indication signal Sf is high (indicating that the power converter 200 outputs a first AC VAC) and the voltage detection signal Vs is at the second level (high level), the status indication signal SRf output by the signal analysis unit 330 is low (indicating that the power relay can be reliably disconnected), that is, the power relay can be reliably disconnected.

[0045] If the AC output voltage indication signal Sf is high, the control signals of the first power relay RL1 and the second power relay RL2 are low, but the voltage detection signal Vs is always high, then the status indication signal SRf output by the signal analysis unit 330 will be low (indicating that the power relay is open), meaning that the power relay cannot be reliably closed.

[0046] Similarly, if the AC output voltage indication signal Sf is high, the control signals of the first power relay RL1 and the second power relay RL2 are high, but the voltage detection signal Vs is always low, then the status indication signal SRf output by the signal analysis unit 330 is high (indicating that the power relay is closed), that is, the power relay cannot be reliably disconnected and is in a sticking fault state.

[0047] Thus, the reliability detection circuit of the power relay in this application can detect whether the power relay can reliably turn off and close, and the circuit is simple and the control is simple.

[0048] As described above, if the status indication signal SRf is always high or low within one or more AC cycles, the first power relay RL1 and the second power relay RL2 are considered to be faulty; if the status indication signal SRf has a rising edge, a falling edge, or a high level for a period of time within one or more AC cycles, the first power relay RL1 and the second power relay RL2 are considered not to be faulty.

[0049] That is, as described above, the signal analysis unit 330 is configured such that when the AC output voltage indication signal Sf indicates that the power converter 200 outputs a first AC current and the voltage detection signal Vs is at a first level, the status indication signal SRf output by the signal analysis unit 330 indicates that the power relay is reliably closed. Furthermore, the signal analysis unit 330 is configured such that when the AC output voltage indication signal Sf indicates that the power converter 200 outputs a first AC current and the voltage detection signal Vs is at a second level, the status indication signal SRf output by the signal analysis unit 330 indicates that the power relay is reliably open.

[0050] Of course, this application does not limit the specific levels of the AC output voltage indication signal Sf, voltage detection signal Vs, and status indication signal SRf in a certain state, as long as they can detect whether the power relay is reliably turned off and closed in the manner described above.

[0051] In practical applications, the first power relay RL1 and the second power relay RL2 can also be selected as normally open relays. The detection principle is the same as when the first power relay RL1 and the second power relay RL2 are selected as normally closed relays. As long as the specific level of the AC output voltage indication signal Sf, the voltage detection signal Vs and the status indication signal SRf in a certain state is configured, and the signal analysis unit 330 is configured, it is possible to detect whether the power relay is reliably turned off and closed. The principle is the same as above, and will not be repeated here.

[0052] for Figure 4 The reliability detection circuit for the power relays shown operates with the AC port connected to the first AC current VAC. During the negative half-cycle of the first AC current VAC, when the amplitude of the first AC current VAC is greater than the voltage V1, the second light-emitting diode D2 conducts, causing the phototransistor S1 to conduct and pulling the collector of the phototransistor S1 low. Similarly, the reliability of the first power relay RL1 and the second power relay RL2 can be detected during the negative half-cycle of the first AC current VAC.

[0053] The principle is explained above using the isolation signal transmission unit 310 as an example of an optocoupler. In actual implementation, it can be any isolation signal transmission unit 310, such as a transformer.

[0054] In one embodiment of the actual implementation, the signal analysis unit 330 and the controller 220 may be integrated.

[0055] The above example illustrates the principle using the status indication signal SRf provided by controller 220. In actual implementation, the status indication signal SRf can also be obtained by sampling circuitry; this application does not limit the method of obtaining it.

[0056] Please refer to the following: Figure 3 and Figure 4 The reliability detection circuit of the power relay in this application further includes a first capacitor C1, a second capacitor C2, a third resistor R3, and a fourth resistor R4. The first capacitor C1 is connected in parallel across the light-emitting diode. The third resistor R3 is connected between the collector of the phototransistor S1 and the voltage source VCC. The collector of the phototransistor S1 outputs a voltage detection signal Vs through the fourth resistor R4. Furthermore, as... Figure 3 and Figure 4 As shown, the second capacitor C2 is connected in parallel between the collector and emitter of the phototransistor S1.

[0057] Although embodiments of the present disclosure and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the spirit and scope of the present disclosure as defined by the appended claims.

[0058] Furthermore, the scope of this application is not intended to be limited to the specific embodiments of the processes, machines, manufactures, compositions of matter, apparatuses, methods, and steps described in the specification. As will be readily understood by those skilled in the art from the disclosure of this publication, processes, machines, manufactures, compositions of matter, means, methods, or steps that perform substantially the same function, currently exist or will be developed or implemented thereafter, will yield substantially the same results as the corresponding embodiments described herein that are available according to this disclosure. Therefore, the appended claims are intended to include such processes, machines, manufactures, compositions of matter, apparatuses, methods, or steps within their scope.

Claims

1. A reliability detection circuit for a power relay, wherein the power relay includes a first power relay and a second power relay, the first power relay being connected between a first AC terminal of a power converter and a first terminal of an AC port, and the second power relay being connected between a second AC terminal of the power converter and a second terminal of the AC port, characterized in that, include: An isolated signal transmission unit includes a primary side and a secondary side that are isolated from each other; A resistor unit is connected in series with the primary side of the isolation signal transmission unit and then connected between the common node between the first power relay and the first terminal of the AC port and the common node between the second power relay and the second terminal of the AC port. The secondary side of the isolation signal transmission unit outputs a voltage detection signal. The signal analysis unit receives the voltage detection signal and the AC output voltage indication signal, and outputs a status indication signal indicating the state of the power relay based on the voltage detection signal and the AC output voltage indication signal, wherein the AC output voltage indication signal is a signal used to indicate the AC voltage output by the power converter.

2. The reliability detection circuit for the power relay according to claim 1, characterized in that, The isolated signal transmission unit includes: A light-emitting diode forms the primary side of the isolated signal transmission unit; A phototransistor forms the secondary side of an isolated signal transmission unit. The collector of the phototransistor is connected to a voltage source, and the emitter of the phototransistor is grounded. The collector of the phototransistor outputs the voltage detection signal.

3. The reliability detection circuit for the power relay according to claim 2, characterized in that, The isolated signal transmission unit further includes a second light-emitting diode, which is connected in anti-parallel to the first light-emitting diode.

4. The reliability detection circuit for the power relay according to claim 1 or 3, characterized in that, The resistor unit includes: The first resistor unit is connected between the primary side of the isolated signal transmission unit and the common node between the first power relay and the first terminal of the AC port; The second resistor unit is connected between the primary side of the isolation signal transmission unit and the common node between the second power relay and the second terminal of the AC port.

5. The reliability detection circuit for the power relay according to claim 2 or 3, characterized in that, The resistance value of the resistor unit is selected such that at least one light-emitting diode in the optocoupler is turned on and the phototransistor is turned on within at least one interval where there is a first AC current between the first terminal and the second terminal of the AC port.

6. The reliability detection circuit for the power relay according to claim 1, characterized in that, The signal analysis unit is configured such that when the AC output voltage indication signal indicates that the power converter outputs a first AC current and the voltage detection signal is at a first level, the status indication signal output by the signal analysis unit indicates that the power relay is reliably closed.

7. The reliability detection circuit for the power relay according to claim 6, characterized in that, The signal analysis unit is configured such that when the AC output voltage indication signal indicates that the power converter outputs a first AC current and the voltage detection signal is at a second level, the status indication signal output by the signal analysis unit indicates that the power relay is reliably disconnected.

8. The reliability detection circuit for the power relay according to claim 1, characterized in that, The power converter is a bidirectional AC / DC converter used in electric vehicles.

9. The reliability detection circuit for the power relay according to claim 1, characterized in that, The DC terminal of the bidirectional AC / DC converter is connected to a high-voltage power battery.

10. The reliability detection circuit for the power relay according to claim 2, characterized in that, The amplitude of the first AC current is lower than that of the 220V AC current.

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