A relay self-test circuit, method and relay system of grid-connected inverter

Abstract

The present invention discloses a relay self-test circuit, method and a relay system of a grid-connected inverter. A relay self-test circuit is used to detect whether the driving circuit of the relay is abnormal, and the self-test circuit includes: a detection terminal, which is used to detect the second end of the coil of the relay, and the coil of the relay also has a first end for connecting to a working voltage; a comparison circuit, one input end of the comparison circuit is electrically connected to the detection terminal, and the other input end of the comparison circuit is connected to a first power supply voltage; and a self-test signal output terminal, which is electrically connected to the output end of the comparison circuit. The present invention can confirm whether the relay driving circuit is normal and improve the accuracy of self-test.

Description

Technical Field

[0001] The invention relates to a relay self-checking circuit and method and a relay system of a grid-connected inverter. Background Art

[0002] Relay is one of the important components of inverters such as photovoltaic grid-connected inverters. When the relay is working, voltage needs to be applied to the driving coil of the relay to close the relay. At present, voltage is usually applied to the driving coil of the relay through a relay driving circuit to control the operation of the relay. Figure 1 That is, a relay system of a current grid-connected inverter is shown. From the perspective of safety regulations, the relay needs to be able to self-check. The current inverter relay self-check is performed based on the assumption that the drive circuit is working normally. However, if the relay drive circuit is abnormal, it will lead to misjudgment and fail to achieve the purpose of relay self-check. Summary of the invention

[0003] In view of at least one of the above problems, an object of the present invention is to provide a self-test circuit for a relay, which can confirm whether the relay drive circuit is normal and improve the accuracy of the self-test.

[0004] Another object of the present invention is to provide a self-test method for a relay, which can confirm whether the relay drive circuit is normal and improve the accuracy of the self-test.

[0005] An object of the present invention is to provide a relay system for a grid-connected inverter using the above relay self-test circuit.

[0006] According to one aspect of the present invention, a self-test circuit of a relay is used to detect whether a driving circuit of the relay is abnormal, and the self-test circuit comprises:

[0007] A detection terminal, which is used to detect the second end of the coil of the relay, and the coil of the relay also has a first end for connecting to the working voltage;

[0008] a comparison circuit, wherein one input terminal of the comparison circuit is electrically connected to the detection terminal, and another input terminal of the comparison circuit is connected to a first power supply voltage; and

[0009] The self-test signal output terminal is electrically connected to the output end of the comparison circuit.

[0010] Preferably, the comparison circuit includes a first comparator and a second comparator, the detection terminal is connected to the inverting input of the first comparator; the non-inverting input of the first comparator is connected to a first power supply; the output of the first comparator is connected to the non-inverting input of the second comparator; the inverting input of the second comparator is grounded, and the output of the second comparator is connected to the self-test signal output terminal.

[0011] More preferably, the output terminal of the first comparator is connected to the non-inverting input terminal of the second comparator through a resistor.

[0012] More preferably, the output end of the second comparator is connected to the self-test signal output terminal through a resistor.

[0013] More preferably, the negative electrode of the first power supply is grounded, the positive electrode is connected in series with a resistor R23 and then grounded, and the positive electrode of the first power supply is connected to the non-phase input terminal of the first comparator through the resistor R23, the self-test circuit also includes a resistor R24, one end of the resistor R24 ​​is connected to the positive electrode of the first power supply, and the other end is connected to the midpoint between the detection terminal and the inverting input terminal of the first comparator; and / or, the negative electrode of the first power supply is grounded, the positive electrode is connected in series with a resistor R25 and then grounded, and the positive electrode of the first power supply is connected to the inverting input terminal of the second comparator through the resistor R25.

[0014] More preferably, the self-test circuit further includes a resistor R26 and a capacitor C21, one end of the resistor R26 is connected to the positive electrode of the first power supply, the other end of the resistor R26 is connected to one end of the capacitor C21, and the other end of the capacitor C21 is grounded.

[0015] Preferably, the self-detection circuit further comprises a diode, a cathode of the diode is connected to the detection terminal, and an anode of the diode is connected to the input end of the comparison circuit.

[0016] Preferably, the self-test circuit further includes a second power supply and a resistor, wherein the positive electrode of the second power supply is connected to one end of the resistor and the negative electrode is grounded; and the other end of the resistor is connected to the self-test signal output terminal.

[0017] According to a second aspect of the present invention, a self-test method of a relay is provided, wherein the coil of the relay has a first end and a second end, the first end is connected to a working voltage, and the self-test circuit as described above is used. The self-test method comprises the following steps:

[0018] collecting the voltage at the second end of the relay coil, sending it to the comparison circuit, and outputting a self-test signal through the comparison circuit;

[0019] When the control signal of the relay is a control signal of a first duty cycle, the self-test signal is at a low level, and when the control signal is a control signal of a second duty cycle, the self-test signal is at a high level, then it is judged that the driving circuit of the relay is normal; otherwise, the driving circuit of the relay is abnormal.

[0020] According to a third aspect of the present invention, a relay system of a grid-connected inverter comprises a relay connected in series between an inverter side and a grid side, the relay being driven by a drive circuit, the relay system further comprising a self-test circuit for detecting whether the drive circuit is abnormal, the self-test circuit adopting the self-test circuit as described above;

[0021] The drive circuit includes a control signal input terminal, and the drive circuit also includes a first switch tube circuit, a second switch tube circuit, a third switch tube circuit and a power supply terminal for supplying power to the coil of the relay;

[0022] The power terminal can be electrically connected to the first end of the relay coil;

[0023] The control end of the first switch tube circuit is electrically connected to the control signal input terminal, one end of the action end of the first switch tube circuit can be electrically connected to the second end of the relay coil, and the other end of the action end of the first switch tube circuit is grounded;

[0024] The control end of the second switch tube circuit is electrically connected to the control signal input terminal, one end of the action end of the second switch tube circuit is electrically connected to the control end of the third switch tube circuit, and the other end of the action end of the second switch tube circuit is grounded;

[0025] One end of the action end of the third switch tube circuit is electrically connected to the middle point between the power terminal and the first end of the relay coil, and the other end of the action end of the third switch tube circuit is electrically connected to the second end of the relay coil;

[0026] The driving circuit also includes a delay circuit for turning on the second switch tube circuit a delay time after the first switch tube circuit is turned on, and a first diode for turning on the second switch tube circuit when the first switch tube circuit is turned off.

[0027] Preferably, the first switch tube circuit comprises an NPN transistor, the base of the NPN transistor is electrically connected to the control signal input terminal, the collector is electrically connected to the second end of the relay coil, and the emitter is grounded;

[0028] The third switching tube circuit includes a PNP transistor, a base of the PNP transistor being electrically connected to the control signal input terminal, a collector being electrically connected to a midpoint between the power terminal and the first end of the relay coil, and an emitter being electrically connected to the second end of the relay coil.

[0029] More preferably, a second diode is connected between the emitter of the PNP transistor and the second end of the relay coil.

[0030] More preferably, the driving circuit further comprises a third diode and a voltage regulator diode, wherein the third diode and the voltage regulator diode are connected in series and then connected in reverse parallel between the collector and the base of the PNP transistor.

[0031] Preferably, the second switching tube circuit includes a field effect tube, the gate of the field effect tube (i.e., the above-mentioned control end) is electrically connected to the control signal input terminal, the source (i.e., the other end of the above-mentioned action end) is grounded, and the drain (i.e., one end of the above-mentioned action end) is electrically connected to the control end of the third switching tube circuit.

[0032] Preferably, a first resistor is connected between the control end of the third switch tube circuit and one end of the control end of the second switch tube circuit.

[0033] Preferably, a second resistor is connected between the control signal input terminal and the control end of the second switch tube circuit.

[0034] Preferably, the delay circuit includes a first capacitor and a third resistor, the first capacitor and the third resistor are connected in parallel to form a parallel branch, one end of the parallel branch is electrically connected to the midpoint between the first diode and the control end of the first switching tube circuit, and the other end is electrically grounded.

[0035] Preferably, the anode of the first diode is electrically connected to the control signal input terminal, and the cathode is electrically connected to the control end of the second switch tube circuit.

[0036] Preferably, the driving circuit further includes a second capacitor, and the second capacitor is electrically connected between the power terminal and ground.

[0037] Specifically, the voltage connected to the power terminal is 12V.

[0038] Preferably, the control signal input terminal is connected to a PWM control port of a DSP chip of the grid-connected inverter.

[0039] According to a second aspect of the present invention, a method for driving a relay adopts the driving circuit as described above, and the driving method comprises the following steps:

[0040] Initially, within a set maintenance time, the control signal output terminal is input with a control signal having a first duty cycle, so that the relay can work normally;

[0041] When the relay works normally, the control signal terminal outputs a control signal having a second duty cycle, wherein the second duty cycle is smaller than the first duty cycle; and / or

[0042] When the relay works normally and the ambient temperature near the relay is lower than the set temperature, the control signal terminal outputs a control signal with a third duty cycle, and the third duty cycle is smaller than the second duty cycle.

[0043] Preferably, the first duty cycle is 100%, the second duty cycle is 50%, and the third duty cycle is 35%.

[0044] Preferably, the holding time is 100 ms.

[0045] Specifically, when the relay performs a closing action, the duty cycle of the PWM control signal is set to 100% within the set holding time (the first 100ms) so that the relay's operating voltage meets the specification requirements; when the relay works normally, the duty cycle of the control signal is set to approximately 50%, and the voltage is maintained at a first voltage that is less than the operating voltage; when it is detected that the ambient temperature of the relay accessories is lower than the set value, the duty cycle of the control signal is set to 35% according to the specification requirements, and the voltage is maintained at a second voltage that is less than the first voltage.

[0046] The present invention adopts the above solution, which has the following advantages compared with the prior art:

[0047] A relay self-checking circuit, method and relay system of a grid-connected inverter of the present invention meet the safety regulations to the greatest extent, and can detect whether the relay drive circuit is abnormal or the relay body is abnormal. When the self-check finds that the relay drive circuit is abnormal, the inverter will not detect the relay again to avoid hidden dangers. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0049] Figure 1 The circuit diagram of the relay system of the conventional grid-connected inverter;

[0050] Figure 2 A circuit diagram of a relay system of a grid-connected inverter according to an embodiment of the present invention;

[0051] Figure 3 is a circuit diagram of a driving circuit of a relay according to an embodiment of the present invention;

[0052] Figure 4 4 is a circuit diagram of a self-test circuit of a relay driving circuit according to an embodiment of the present invention.

[0053] 100, driving circuit; 101, control signal input terminal; 102, power supply terminal; 103, first switch tube circuit; 104, second switch tube circuit; 105, third switch tube circuit; 106, delay circuit;

[0054] 200, driving circuit;

[0055] 300, coil;

[0056] 400, self-test circuit; 401, detection terminal; 402, first power supply; 403, second power supply; 404, self-test signal terminal. DETAILED DESCRIPTION

[0057] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0058] As shown in this specification and claims, the terms "comprises" and "include" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list, and the method or device may also include other steps or elements. The term "and / or" as used herein includes any combination of one or more of the relevant listed items.

[0059] It is further understood that the terms "first", "second", etc. are used to describe various information, but such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other, and do not indicate a specific order or degree of importance. In fact, the expressions "first", "second", etc. can be used interchangeably. For example, without departing from the scope of the present disclosure, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information.

[0060] According to one embodiment of the present invention, a relay system of a photovoltaic grid-connected inverter is Figure 2 See Figure 2The relay system includes a main relay RY1 and a sub-relay RY2 connected in series between the inverter side and the grid side; specifically, the live wire and the neutral wire between the inverter side and the grid side are respectively provided with a main relay RY1 and a sub-relay RY2 connected in series. The main relay RY1 has a drive circuit 100 that provides voltage to the coil 300 of the main relay RY1, so that the main relay RY1 is driven by the drive circuit 100 to work (e.g., closed); the sub-relay RY2 has a drive circuit 200 that provides voltage to the coil 300 of the sub-relay RY2, so that the sub-relay RY2 is driven by the drive circuit 200 to work (e.g., closed).

[0061] This embodiment also provides a specific relay driving circuit, which can be applied to the relay system of the photovoltaic grid-connected inverter to drive the main relay RY1 and the sub-relay RY2. The driving circuit 100 of the main relay RY1 is the same as the driving circuit 200 of the sub-relay RY2. The driving circuit 100 of the main relay RY1 is described in detail below. The driving circuit 200 of the sub-relay RY2 is similar to it and will not be described in detail here. Figure 3 As shown, the driving circuit 100 of the main relay RY1 includes a control signal input terminal 101, a first switch tube circuit 103, a second switch tube circuit 104, a third switch tube circuit 105 and a power supply terminal 102 for supplying power to the coil 300 of the relay.

[0062] The control signal input terminal 101 can be electrically connected to the control unit to receive the control signal M_RELAY from the control unit. The control signal input terminal 101 can be electrically connected to the PWM control port of the DSP chip of the photovoltaic grid-connected inverter, through which different duty cycles can be set; thereby, the voltage of the coil 300 of the relay RY1 changes according to the duty cycle, thereby generating different voltages on the relay coil 300.

[0063] The power terminal 102 is electrically connected to the first end of the relay coil 300. The power terminal 102 is used to input working power to the coil 300. In this embodiment, there is only one power terminal 102 and it is connected to a 12V voltage.

[0064] The control end of the first switch tube circuit 103 is electrically connected to the control signal input terminal 101 and is thus controlled by the control signal M_RELAY. One end of the action end of the first switch tube circuit 103 can be electrically connected to the second end of the relay coil 300, and the other end of the action end of the first switch tube circuit 103 is grounded. Specifically in this embodiment, the first switch tube circuit 103 includes an NPN transistor Q1, the base (i.e., the control end) of the NPN transistor Q1 is electrically connected to the control signal input terminal 101, the collector (i.e., one end of the action end) is electrically connected to the second end of the relay coil 300, and the emitter (i.e., the other end of the action end) is grounded.

[0065] The control end of the second switch tube circuit 104 is electrically connected to the control signal input terminal 101, one end of the action end of the second switch tube circuit 104 is electrically connected to the control end of the third switch tube circuit 105, and the other end of the action end of the second switch tube circuit 104 is grounded. Specifically in this embodiment, the second switch tube circuit 104 includes a field effect transistor Q2, the gate (i.e., the control end) of the field effect transistor Q2 is electrically connected to the control signal input terminal 101, the source (i.e., the other end of the action end) is grounded, and the drain (i.e., one end of the action end) is electrically connected to the control end of the third switch tube circuit 105.

[0066] One end of the action end of the third switch tube circuit 105 is electrically connected to the middle point between the power terminal 102 and the relay coil 300, and the other end of the action end of the third switch tube circuit 105 is electrically connected to the second end of the relay coil 300. Specifically in this embodiment, the third switch tube circuit 105 includes a PNP transistor Q3, the base of the PNP transistor Q3 (i.e., the control end) is electrically connected to the drain of the field effect transistor Q2, the collector (i.e., the action end) is electrically connected to the middle point between the power terminal 102 and the relay coil 300, and the emitter (i.e., the other end of the action end) is electrically connected to the second end of the relay coil 300.

[0067] The driving circuit 100 also includes a delay circuit 106 for turning on the second switch tube circuit 104 after a delay time after the first switch tube circuit 103 is turned on, and a first diode D1 for turning on the third switch tube circuit 105 when the first switch tube circuit 103 is turned off. The first diode D1 is located between the control signal input terminal 101 and the gate of the field effect tube Q2, and its positive electrode is electrically connected to the control signal input terminal 101, and its negative electrode is electrically connected to the gate of the field effect tube Q2. The first diode D1 can keep the second switch tube circuit 104 turned on after the first switch tube circuit 103 is turned off, forming a relay shutdown loop. The delay circuit 106 specifically includes a first capacitor C1 and a third resistor R3, and the first capacitor C1 and the third resistor R3 are connected in parallel to form a parallel branch, one end of the parallel branch is electrically connected to the middle point of the first diode D1 and the control end of the first switch tube circuit 103, and the other end is electrically grounded. A delay is set for driving the second switch tube circuit 104, so that the second switch tube circuit 104 is turned on again after the first switch tube circuit 103 is turned on for a period of time (specifically 5 μs), so that the second switch tube circuit 104 provides a shutdown loop without affecting the conduction loop.

[0068] A second diode D2 is connected between the other end of the relay coil 300 and the emitter of the PNP transistor Q3. Specifically, the anode of the second diode D2 is electrically connected to the second end of the relay coil 300, and the cathode is electrically connected to the emitter of the PNP transistor Q3. The function of the second diode D2 is to provide a freewheeling path for the coil current when the voltage of the relay coil is reversed, so as to protect the voltage of the relay coil from exceeding the specification requirements.

[0069] The drive circuit 100 also includes a third diode D3 and a voltage stabilizing diode ZD1. The third diode D3 and the voltage stabilizing diode ZD1 are connected in series and then reversely connected in parallel between the collector and the base of the PNP transistor Q3. When the voltage of the relay coil is reversed, the second diode D2 and the voltage stabilizing diode ZD1 provide a freewheeling loop to clamp the coil voltage to the power supply voltage +12V, thereby protecting the relay coil voltage from exceeding the specification requirements. The third diode D3 acts to accelerate the conduction of the PNP transistor Q3.

[0070] A first resistor R1 is connected between the control end of the third switch tube circuit 105 and one end of the control end of the second switch tube circuit 104. Specifically, the first resistor R1 is electrically connected in series between the drain of the field effect tube Q2 and the base of the PNP transistor Q3. The first resistor R1 is the base resistor of the PNP transistor Q3 and provides a driving current to the PNP transistor Q3.

[0071] A second resistor R2 is connected between the control signal input terminal 101 and the control end of the second switch tube circuit 104. Specifically, the second resistor R2 is connected in series between the control signal input terminal 101 and the positive electrode of the first diode D1. The second resistor R2 and the first capacitor C1 form a delay, so that the field effect tube Q2 is turned on after the NPN transistor Q1 is turned on.

[0072] The driving circuit 100 further includes a fourth resistor R4, a fifth resistor R5 and a fourth diode D4. The fourth resistor R4 is connected in series between the control signal input terminal 101 and the base of the NPN transistor Q1. The fourth diode D4 and the fifth resistor R5 are connected in series and then connected in reverse parallel between the two ends of the third resistor R3. The fourth resistor R4 is a turn-on driving resistor of the NPN transistor Q1. The fourth diode D4 and the fifth resistor R5 are a turn-off driving circuit of the NPN transistor Q1 to achieve fast turn-off.

[0073] The driving circuit 100 further includes a second capacitor C2, which is electrically connected between the power supply terminal 102 and the ground. The second capacitor C2 is used as an energy storage and voltage stabilizing capacitor to provide a stable voltage during the RELAY switching process.

[0074] The working principle of the driving circuit 100 is:

[0075] When the control signal M_RELAY is high, the NPN transistor Q1 is turned on, and the +12V of the power terminal 102 forms a loop through the relay coil 300 and the NPN transistor Q1, and the current of the relay coil 300 increases; when the control signal M_RELAY is low, the NPN transistor Q1 is turned off, the voltage of the relay coil 300 is reversed, and a loop is formed through the second diode D2 and the PNP transistor Q3, and the current of the relay coil 300 decreases. A delay is set for the drive of the field effect transistor Q2 through the delay circuit 106, so that the field effect transistor Q2 is turned on again after the NPN transistor Q1 is turned on for 5us, and the field effect transistor Q2 provides a turn-off loop without affecting the turn-on loop. The first diode D1 allows the field effect transistor Q2 to remain turned on after the NPN transistor Q1 is turned off, forming a RELAY turn-off loop. When RELAY is closed, the PWM is set to 100% in the first 100ms, so that the RELAY action voltage meets the specification requirement of +12V; when RELAY is working normally, the PWM can be set to about 50% according to the specification requirements of the relay to maintain the voltage at +6V; when the NTC sensor of the inverter detects that the ambient temperature of the RELAY accessories is very low, the PWM can be set to 35% according to the specification requirements to maintain the voltage at +4.2V, thereby reducing the relay drive power consumption and improving the efficiency of the whole machine. The circuit has good consistency. When replacing the relay to reduce costs, the PWM duty cycle can be directly modified by software according to the holding voltage requirements of the new relay, which has good portability.

[0076] This embodiment also provides a self-test circuit 400 of the relay drive circuit 100; further, the relay system of the above-mentioned grid-connected inverter of this embodiment further includes the self-test circuit 400, through which the drive circuit 100 of the main relay RY1 and the drive circuit 200 of the auxiliary relay RY2 are detected to be abnormal. Figure 4 As shown, the self-test circuit 400 includes two detection terminals 401; one detection terminal 401 is used to detect the voltage of the second end of the coil 300 of the main relay RY1, that is, the voltage of the collector of the NPN transistor Q1 in the main relay RY1 drive circuit 100; the other detection terminal 401 is used to detect the voltage of the second end of the coil 300 of the auxiliary relay RY2, that is, the voltage of the collector of the NPN transistor Q1 in the auxiliary relay RY2 drive circuit 200. The self-test circuit 400 also includes a comparison circuit, the above two detection terminals 401 are respectively electrically connected to one input end of the comparison circuit, the other input end of the comparison circuit is connected to the first power supply voltage, and the output end of the comparison circuit is electrically connected to a self-test signal output terminal 404, the self-test signal output terminal 404 can be electrically connected to a control module, specifically a DSP chip of a photovoltaic grid-connected inverter, and the DSP chip is used to determine whether the relay drive circuit 100 is abnormal.

[0077] Specifically, the comparison circuit specifically includes a first comparator U1 and a second comparator U2. The two detection terminals 401 are connected to the inverting input terminal of the first comparator U1; the non-inverting input terminal of the first comparator U1 is connected to a first power supply 402 to access the voltage, and the voltage of the first power supply 402 is equal to the operating voltage of the relay, that is, +12V; the output terminal of the first comparator U1 is connected to the non-inverting input terminal of the second comparator U2 through a resistor R21. The inverting input terminal of the second comparator U2 is grounded, and the output terminal of the second comparator U2 is connected to the self-test signal output terminal 404 through a resistor R22.

[0078] The negative electrode of the first power supply 402 is grounded, and the positive electrode is connected in series with two resistors R23 and then grounded. The non-inverting input terminal of the first comparator U1 is connected to the middle point of the two resistors R23. The self-test circuit 400 also includes a resistor R24, one end of which is connected to the positive electrode of the first power supply 402, and the other end is connected to the middle point between the detection terminal 401 and the inverting input terminal of the first comparator U1.

[0079] The positive electrode of the first power supply 402 is also connected in series with two resistors R25 and then grounded, and the inverting input terminal of the second comparator U2 is connected to the middle point of the two resistors R25. The self-test circuit 400 also includes a resistor R26 and a capacitor C21, one end of the resistor R26 is connected to the positive electrode of the first power supply 402, the other end of the resistor R26 is connected to one end of the capacitor C21, and the other end of the capacitor C21 is grounded.

[0080] The self-test circuit 400 also includes a second power supply 403 and a resistor R27. The voltage of the second power supply 403 is less than the voltage of the first power supply 402, specifically 3.3V; the positive electrode of the second power supply 403 is connected to one end of the resistor R27, and the negative electrode is grounded. The other end of the resistor R27 is connected to the output end of the second comparator U2 and the middle point of the resistor R22.

[0081] The self-test circuit 400 further includes a capacitor C22 , one end of which is connected to the middle point between the resistor R22 and the self-test signal output terminal 404 , and the other end of which is grounded.

[0082] A diode D21 is connected between each detection terminal 401 and the inverting input terminal of the first comparator U1. Specifically, the cathode of the diode D21 is connected to the detection terminal 401, and the anode is connected to the inverting input terminal of the first comparator U1.

[0083] The traditional relay self-test scheme does not consider the situation of driver damage, which will cause the relay self-test judgment to be wrong, because it is very likely that the relay body is not damaged, but the relay drive circuit 100 is damaged. The self-test circuit 400 of the relay drive circuit 100 of this embodiment can detect whether the relay drive circuit 100 is damaged, so as to truly detect whether the relay body is damaged, thereby meeting the requirements of safety regulations. The principle of the self-test circuit 400 is to detect the voltage at one end of the relay coil 300, that is, the voltage of the collector of the NPN transistor Q1 in the drive circuit 100, and judge whether the signal is normal through a comparator. Before the inverter is connected to the grid, the RELAY drive circuit will be self-tested first. The DSP PWM will first output 100% DUTY, and detect that the DSP_RLY signal is high. Then the DSP PWM will output PWM with 0% DUTY, and detect that DSP_RLY is low. This is to judge that the RELAY drive circuit 100 is normal; otherwise, the drive circuit 100 is judged to be abnormal.

[0084] The principle of the self-test circuit is to use the core part of the drive circuit, that is, the collector of Q1, as the detection point. The detection signals of the main and sub RELAYs are connected to the detection circuit and connected to the inverting input of the comparator U1 through the diode D21. When the DSP control PWM signal 101 is 100% DUTY, the main and sub RELAY detection signals 401 are low level, and the inverting input of the comparator U1 is pulled down through the diode D21, U1 outputs a high level, and then the comparator U2 outputs a high level signal. When the DSP control PWM signal 101 is 0% DUTY, the main and sub RELAY detection signals 401 are high level, the diode D21 is cut off, the comparator U1 outputs a low level, and then the comparator U2 outputs a low level signal. When the U2 output signal, that is, the 404 DSP sampling signal, does not meet the above logic, it means that the RELAY drive circuit is abnormal.

[0085] This embodiment also provides a driving method for a relay, which uses the above-mentioned driving circuit. The driving method comprises the following steps:

[0086] Initially, within a set holding time, the control signal output terminal is input with a control signal having a first duty cycle, so that the relay can work normally;

[0087] When the relay works normally, the control signal terminal outputs a control signal with a second duty cycle, and the second duty cycle is smaller than the first duty cycle;

[0088] When the relay works normally and the ambient temperature near the relay is lower than the set temperature, the control signal terminal outputs a control signal with a third duty cycle, and the third duty cycle is smaller than the second duty cycle.

[0089] The first duty cycle may be 100%, the second duty cycle is 50%, and the third duty cycle is 35%.

[0090] Specifically, when RELAY closes, the PWM is set to 100% for the first 100ms (the operating voltage maintenance time required in the relay specifications) so that the operating voltage of RELAY meets the specification requirement of +12V; when RELAY works normally, according to the specifications of the relay, the PWM is set to about 50% to maintain the voltage at +6V; when the NTC temperature sensor of the inverter detects that the ambient temperature of the RELAY accessories is very low, the PWM is set to 35% according to the specifications to maintain the voltage at +4.2V.

[0091] This embodiment further provides a self-test method for a relay drive circuit, wherein the relay coil has a first end and a second end, and the first end is connected to a working voltage. The self-test method comprises the following steps:

[0092] The voltage at the second end of the relay coil is collected and sent to a comparison circuit, and a self-test signal is output through the comparison circuit;

[0093] When the control signal is a control signal of the first duty cycle, the self-test signal is at a low level, and when the control signal is a control signal of the second duty cycle, the self-test signal is at a high level, then the relay drive circuit is judged to be normal; otherwise, the relay drive circuit is abnormal. The second duty cycle is less than the first duty cycle; the first duty cycle can be selected as 100%, and the second duty cycle can be selected as 0.

[0094] This embodiment adopts DSP PWM control technology to realize controllable voltage of RELAY coil, and reduces the driving holding voltage to the maximum extent according to the detection of RELAY ambient temperature and RELAY working state, so as to achieve the maximum improvement of efficiency.

[0095] This embodiment utilizes a driving delay to implement a RELAY shut-off loop, thereby providing a path for controllable RELAY coil voltage.

[0096] This embodiment designs a self-test circuit for the RELAY driver based on the RELAY driver circuit. Through self-test, it is first determined whether the RELAY driver is abnormal, so that it can be 100% confirmed whether the RELAY body is faulty, meeting safety regulations.

[0097] The above embodiment is only for illustrating the technical concept and features of the present invention, and is a preferred embodiment. Its purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A relay system for a grid-connected inverter, comprising a relay connected in series between an inverter side and a grid side, wherein the relay is driven by a drive circuit, and characterized in that: The relay system further includes a self-test circuit for detecting whether the drive circuit is abnormal, and the self-test circuit includes: A detection terminal, which is used to detect the second end of the coil of the relay, and the coil of the relay also has a first end for connecting to the working voltage; a comparison circuit, wherein one input terminal of the comparison circuit is electrically connected to the detection terminal, and another input terminal of the comparison circuit is connected to a first power supply voltage; and A self-test signal output terminal electrically connected to the output end of the comparison circuit; The driving circuit includes a control signal input terminal, a first switch tube circuit, a second switch tube circuit, a third switch tube circuit and a power supply terminal for supplying power to the coil of the relay; The power terminal can be electrically connected to the first end of the relay coil; The control end of the first switch tube circuit is electrically connected to the control signal input terminal, one end of the action end of the first switch tube circuit can be electrically connected to the second end of the relay coil, and the other end of the action end of the first switch tube circuit is grounded; The control end of the second switch tube circuit is electrically connected to the control signal input terminal, one end of the action end of the second switch tube circuit is electrically connected to the control end of the third switch tube circuit, and the other end of the action end of the second switch tube circuit is grounded; a first resistor is connected between the control end of the third switch tube circuit and one end of the control end of the second switch tube circuit, and a second resistor is connected between the control signal input terminal and the control end of the second switch tube circuit; One end of the action end of the third switch tube circuit is electrically connected to the middle point between the power terminal and the first end of the relay coil, and the other end of the action end of the third switch tube circuit is electrically connected to the second end of the relay coil; The driving circuit also includes a delay circuit for turning on the second switch tube circuit a delay time after the first switch tube circuit is turned on, and a first diode for turning on the second switch tube circuit when the first switch tube circuit is turned off.

2. The relay system according to claim 1, characterized in that: The comparison circuit includes a first comparator and a second comparator, the detection terminal is connected to the inverting input terminal of the first comparator; the non-inverting input terminal of the first comparator is connected to a first power supply; the output terminal of the first comparator is connected to the non-inverting input terminal of the second comparator; the inverting input terminal of the second comparator is grounded, and the output terminal of the second comparator is connected to the self-test signal output terminal.

3. The relay system according to claim 2, characterized in that: The output terminal of the first comparator is connected to the non-inverting input terminal of the second comparator through a resistor.

4. The relay system according to claim 2, characterized in that: The output end of the second comparator is connected to the self-test signal output terminal through a resistor.

5. The relay system according to claim 2, characterized in that: The negative electrode of the first power supply is grounded, the positive electrode is connected in series with a resistor R23 and then grounded, and the positive electrode of the first power supply is connected to the non-phase input terminal of the first comparator through the resistor R23, the self-test circuit also includes a resistor R24, one end of the resistor R24 ​​is connected to the positive electrode of the first power supply, and the other end is connected to the middle point between the detection terminal and the inverting input terminal of the first comparator; and / or, the negative electrode of the first power supply is grounded, the positive electrode is connected in series with a resistor R25 and then grounded, and the positive electrode of the first power supply is connected to the inverting input terminal of the second comparator through the resistor R25.

6. The relay system according to claim 2, characterized in that: The self-test circuit further includes a resistor R26 and a capacitor C21, one end of the resistor R26 is connected to the positive electrode of the first power supply, the other end of the resistor R26 is connected to one end of the capacitor C21, and the other end of the capacitor C21 is grounded.

7. The relay system according to claim 1 or 2, characterized in that: The self-checking circuit further comprises a diode, wherein a cathode of the diode is connected to the detection terminal, and an anode of the diode is connected to an input end of the comparison circuit.

8. The relay system according to claim 1 or 2, characterized in that: The self-test circuit further includes a second power supply and a resistor, wherein the positive electrode of the second power supply is connected to one end of the resistor and the negative electrode is grounded; the other end of the resistor is connected to the self-test signal output terminal.

9. The relay system according to claim 1, characterized in that: The first switch tube circuit comprises an NPN transistor, the base of the NPN transistor is electrically connected to the control signal input terminal, the collector is electrically connected to the second end of the relay coil, and the emitter is grounded; The third switching tube circuit includes a PNP transistor, a base of the PNP transistor being electrically connected to the control signal input terminal, a collector being electrically connected to a midpoint between the power terminal and the first end of the relay coil, and an emitter being electrically connected to the second end of the relay coil.

Images