Leakage protection circuit and electrical equipment

Abstract

The utility model relates to the technical field of electronic power, and discloses an electric leakage protection circuit and electrical equipment, and the electric leakage protection circuit comprises a reference voltage circuit, a signal output circuit, a first voltage comparison circuit and a second voltage comparison circuit. The second output end of the reference voltage circuit is connected with the second voltage comparison circuit, the output end of the second voltage comparison circuit is connected with the first input end of the first voltage comparison circuit, and the second voltage comparison circuit outputs a second voltage comparison signal when the leakage voltage is larger than the first reference voltage. The second reference voltage is connected to the first input end of the first voltage comparison circuit, and the input voltage of the first input end of the first voltage comparison circuit is instantly increased to a fixed voltage value, so that misjudgment caused by fluctuation of the input voltage of the first voltage comparison circuit due to noise interference and the like is avoided; the electric leakage unlocking action is prevented from being frequently executed due to small voltage fluctuation, so that the reliability of the electric leakage detection circuit is greatly enhanced.

Description

Technical Field

[0001] The present application relates to the field of electronic power technology, and in particular to a leakage protection circuit and electrical equipment. Background Art

[0002] In order to adapt to some special working environments, most electrical equipment needs to have good insulation performance, so electrical equipment must be protected against leakage. Taking the inverter as an example, with the development of inverter technology, most existing inverters are required to have leakage lockout protection to ensure that they can be locked when leakage occurs in the inverter to avoid electric shock accidents.

[0003] At present, a comparator, a switch tube and a relay are usually used to form a leakage detection circuit to detect the insulation resistance of electrical equipment. When the insulation resistance of the electrical equipment decreases, that is, when the electrical equipment has leakage, the comparator outputs a conduction signal to the switch tube, so that the circuit where the relay is located is turned on, and the contact state of the relay changes accordingly, thereby performing a leakage lock operation based on the contact state of the relay. However, since the comparator outputs a corresponding signal based on the comparison result of the input voltage, when the input voltage fluctuates due to noise interference and other reasons, the output signal of the comparator is prone to change accordingly, resulting in misjudgment of the leakage detection result, and then causing the electrical equipment to frequently perform unlocking actions when it leaks. Utility Model Content

[0004] The main purpose of the present application is to propose a leakage protection circuit and electrical equipment, aiming to solve the problem that the existing leakage detection circuit is prone to misjudgment and has relatively poor reliability.

[0005] To achieve the above object, the present application provides a leakage protection circuit, which is applied to electrical equipment, and the leakage protection circuit includes a reference voltage circuit, a signal output circuit, a first voltage comparison circuit and a second voltage comparison circuit;

[0006] The first input terminal of the first voltage comparison circuit is connected to the leakage voltage, the second input terminal of the first voltage comparison circuit is connected to the first output terminal of the reference voltage circuit, the first output terminal of the reference voltage circuit is used to output a first reference voltage, and the first voltage comparison circuit is used to output a first voltage comparison signal when the leakage voltage is greater than the first reference voltage;

[0007] The input end of the signal output circuit is connected to the output end of the first voltage comparison circuit, and the signal output circuit is used to output a leakage fault signal according to the first voltage comparison signal;

[0008] The first input terminal of the second voltage comparison circuit and the output terminal of the second voltage comparison circuit are respectively connected to the first input terminal of the first voltage comparison circuit, the second input terminal of the second voltage comparison circuit is connected to the second input terminal of the first voltage comparison circuit, the second voltage comparison circuit is also connected to the second output terminal of the reference voltage circuit, the second output terminal of the reference voltage circuit is used to output a second reference voltage, and the second voltage comparison circuit is used to output a second voltage comparison signal when the leakage voltage is greater than the first reference voltage, so that the second reference voltage is connected to the first input terminal of the first voltage comparison circuit.

[0009] Optionally, the first voltage comparison circuit includes a first comparator, and the second voltage comparison circuit includes a second comparator and a first diode;

[0010] The first input terminal of the first comparator is connected to the leakage voltage, the second input terminal of the first comparator is connected to the first output terminal of the reference voltage circuit, and the output terminal of the first comparator is connected to the input terminal of the signal output circuit;

[0011] The first input terminal of the second comparator is connected to the first input terminal of the first comparator, the second input terminal of the second comparator is connected to the second input terminal of the first comparator, the anode of the first diode is respectively connected to the output terminal of the second comparator and the second output terminal of the reference voltage circuit, and the cathode of the first diode is connected to the first input terminal of the first comparator.

[0012] Optionally, the second voltage comparison circuit also includes a first resistor, one end of the first resistor is connected to the anode of the first diode and the output end of the second comparator respectively, and the other end of the first resistor is connected to the second output end of the reference voltage circuit.

[0013] Optionally, the reference voltage circuit includes a reference voltage chip, a second resistor, a third resistor, a fourth resistor and a fifth resistor;

[0014] The anode of the reference voltage chip is grounded, the cathode of the reference voltage chip is respectively connected to the power supply and one end of the second resistor, the other end of the second resistor is respectively connected to the voltage output end of the reference voltage chip and one end of the third resistor, the other end of the third resistor is grounded, one end of the fourth resistor is respectively connected to the cathode of the reference voltage chip and the second voltage comparison circuit, the other end of the fourth resistor is respectively connected to the second input end of the first voltage comparison circuit and one end of the fifth resistor, and the other end of the fifth resistor is grounded.

[0015] Optionally, the leakage protection circuit also includes a leakage voltage output circuit, the input end of the leakage voltage output circuit is connected to the first end of the insulation resistor of the electrical equipment, the second end of the insulation resistor is connected to the power supply, the output end of the leakage voltage output circuit is connected to the first input end of the first voltage comparison circuit, and the leakage voltage output circuit is used to output the leakage voltage.

[0016] Optionally, the leakage voltage output circuit includes a sixth resistor and a seventh resistor, one end of the sixth resistor is connected to the first end of the insulation resistor, the other end of the sixth resistor is respectively connected to the first input end of the first voltage comparison circuit and one end of the seventh resistor, and the other end of the seventh resistor is grounded.

[0017] Optionally, the signal output circuit includes a first switch tube and a first relay;

[0018] The first end of the first switch tube is connected to the first end of the coil of the first relay, the second end of the first switch tube is grounded, the controlled end of the first switch tube is connected to the output end of the first voltage comparison circuit, and the second end of the coil of the first relay is connected to a power supply.

[0019] Optionally, the signal output circuit further includes an eighth resistor and a ninth resistor, one end of the eighth resistor is connected to the output end of the first voltage comparison circuit, the other end of the eighth resistor is respectively connected to the controlled end of the first switch tube and one end of the ninth resistor, and the other end of the ninth resistor is grounded;

[0020] And / or, the signal output circuit also includes a second switch tube, the second end of the second switch tube is connected to the first end of the coil of the first relay, the first end of the second switch tube is grounded, and the controlled end of the second switch tube is connected to the first end of the first switch tube.

[0021] Optionally, the signal output circuit further includes a second diode, an anode of the second diode is connected to the first end of the coil of the first relay, and a cathode of the second diode is connected to the second end of the coil of the first relay;

[0022] And / or, the signal output circuit also includes a tenth resistor and a light-emitting diode, one end of the tenth resistor is connected to the anode of the light-emitting diode, the other end of the tenth resistor is connected to the second end of the coil of the first relay, and the cathode of the light-emitting diode is connected to the first end of the coil of the first relay.

[0023] In addition, to achieve the above-mentioned purpose, the present application also provides an electrical device, which includes the leakage protection circuit as described above.

[0024] The present application provides a leakage protection circuit, which includes a reference voltage circuit, a signal output circuit, a first voltage comparison circuit and a second voltage comparison circuit. The first input end of the first voltage comparison circuit is connected to the leakage voltage, and the second input end of the first voltage comparison circuit is connected to the first output end of the reference voltage circuit to connect to the first reference voltage, and outputs a first voltage comparison signal to the signal output circuit when the leakage voltage is greater than the first reference voltage. The signal output circuit then outputs a corresponding leakage fault signal based on the first voltage comparison signal. The leakage fault signal can be used to identify that the electrical equipment is in a leakage state, and a leakage locking operation is performed synchronously to realize the leakage protection function. At the same time, by connecting the output end of the second voltage comparison circuit to the first input end of the first voltage comparison circuit, positive feedback is formed, and the two input ends of the second voltage comparison circuit are also connected to the leakage voltage and the first reference voltage at the same time. The second voltage comparison circuit is also connected to the second output end of the reference voltage circuit, and when the leakage voltage is greater than the first reference voltage, the second voltage comparison signal is output to the first input end of the first voltage comparison circuit. At this time, the second output end of the reference voltage circuit can be connected to the first input end of the first voltage comparison circuit to connect the second reference voltage to the first input end of the first voltage comparison circuit. That is to say, at this time, the input voltage of the first input end of the first voltage comparison circuit can be instantly pulled up to a fixed voltage value, thereby avoiding misjudgment caused by fluctuations in the input voltage of the first voltage comparison circuit due to noise interference and other reasons, and preventing frequent leakage unlocking actions due to small voltage fluctuations, thereby greatly enhancing the reliability of the leakage detection circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the framework structure of a leakage protection circuit in one embodiment of the present application;

[0026] Figure 2 This is a schematic diagram of the framework structure of a leakage protection circuit in another embodiment of the present application;

[0027] Figure 3 This is a schematic diagram of the structure of a leakage protection circuit in one embodiment of the present application.

[0028] Description of Figure Numbers:

[0029] Label name Label name 100 Leakage protection circuit 10 Reference voltage circuit 20 First voltage comparison circuit 30 Signal output circuit 40 Second voltage comparison circuit 50 Leakage voltage output circuit U1-1 First comparator U1-2 Second comparator U2 Voltage reference chip R1~R13 The first resistor to the thirteenth resistor D1~D3 The first diode to the third diode D4 Light Emitting Diode Q1~Q2 The first switch tube ~ the second switch tube C1 capacitance K1 First relay K2 Second relay

[0030] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0031] It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0032] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0033] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0034] In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0035] In addition, in this application, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0036] At present, a comparator, a switch tube and a relay are usually used to form a leakage detection circuit to detect the insulation resistance of electrical equipment. When the insulation resistance of the electrical equipment decreases, that is, when the electrical equipment has leakage, the comparator outputs a conduction signal to the switch tube, so that the circuit where the relay is located is turned on, and the contact state of the relay changes accordingly, thereby performing a leakage locking operation based on the contact state of the relay. However, since the comparator outputs a corresponding signal based on the comparison result of the input voltage, when the input voltage fluctuates due to noise interference and other reasons, the output signal of the comparator is prone to change, resulting in misjudgment of the leakage detection result, and then causing the electrical equipment to frequently perform unlocking actions when it leaks. In other words, the existing leakage detection circuit has the problem of easy misjudgment and relatively poor reliability.

[0037] Based on this, the present application provides a leakage protection circuit 100, which is applied to electrical equipment, referring to Figure 1 , the leakage protection circuit 100 includes a reference voltage circuit 10, a signal output circuit 30, a first voltage comparison circuit 20 and a second voltage comparison circuit 40;

[0038] The first input terminal of the first voltage comparison circuit 20 is connected to the leakage voltage, the second input terminal of the first voltage comparison circuit 20 is connected to the first output terminal of the reference voltage circuit 10, the first output terminal of the reference voltage circuit 10 is used to output the first reference voltage, and the first voltage comparison circuit 20 is used to output a first voltage comparison signal when the leakage voltage is greater than the first reference voltage;

[0039] The input end of the signal output circuit 30 is connected to the output end of the first voltage comparison circuit 20, and the signal output circuit 30 is used to output a leakage fault signal according to the first voltage comparison signal;

[0040] The first input terminal of the second voltage comparison circuit 40 and the output terminal of the second voltage comparison circuit 40 are respectively connected to the first input terminal of the first voltage comparison circuit 20, the second input terminal of the second voltage comparison circuit 40 is connected to the second input terminal of the first voltage comparison circuit 20, and the second voltage comparison circuit 40 is also connected to the second output terminal of the reference voltage circuit 10. The second output terminal of the reference voltage circuit 10 is used to output a second reference voltage. The second voltage comparison circuit 40 is used to output a second voltage comparison signal when the leakage voltage is greater than the first reference voltage, so that the second reference voltage is connected to the first input terminal of the first voltage comparison circuit 20.

[0041] In this embodiment, the two input terminals of the first voltage comparison circuit 20 are respectively connected to the leakage voltage and the first reference voltage output by the reference voltage circuit 10, and when the leakage voltage is greater than the first reference voltage, the first voltage comparison signal is output to the signal output circuit 30. The signal output circuit 30 then outputs a corresponding leakage fault signal according to the first voltage comparison signal. The leakage fault signal can be used to identify that the electrical equipment is in a leakage state, and the leakage locking operation can be performed synchronously to realize the leakage protection function. At the same time, by connecting the output end of the second voltage comparison circuit 40 to the first input end of the first voltage comparison circuit 20, positive feedback is formed, and the two input ends of the second voltage comparison circuit 40 are also connected to the leakage voltage and the first reference voltage at the same time. The second voltage comparison circuit 40 is also connected to the second output end of the reference voltage circuit 10, and when the leakage voltage is greater than the first reference voltage, the second voltage comparison signal is output to the first input end of the first voltage comparison circuit 20. At this time, the second output end of the reference voltage circuit 10 can be connected to the first input end of the first voltage comparison circuit 20 to connect the second reference voltage to the first input end of the first voltage comparison circuit 20. That is to say, at this time, the input voltage of the first input end of the first voltage comparison circuit 20 can be instantly pulled up to a fixed voltage value, thereby avoiding misjudgment caused by the input voltage fluctuation of the first voltage comparison circuit 20 due to noise interference and other reasons, and preventing the leakage unlocking action from being frequently performed due to small voltage fluctuations, thereby greatly enhancing the reliability of the leakage detection circuit. It should be noted that in this embodiment, the second voltage comparison signal output by the second voltage comparison circuit 40 is a conduction signal.

[0042] In one embodiment, reference Figure 3 , the first voltage comparison circuit 20 includes a first comparator U1-1, and the second voltage comparison circuit 40 includes a second comparator U1-2 and a first diode D1;

[0043] A first input terminal of the first comparator U1-1 is connected to the leakage voltage, a second input terminal of the first comparator U1-1 is connected to a first output terminal of the reference voltage circuit 10, and an output terminal of the first comparator U1-1 is connected to an input terminal of the signal output circuit 30;

[0044] The first input terminal of the second comparator U1-2 is connected to the first input terminal of the first comparator U1-1, the second input terminal of the second comparator U1-2 is connected to the second input terminal of the first comparator U1-1, the anode of the first diode D1 is respectively connected to the output terminal of the second comparator U1-2 and the second output terminal of the reference voltage circuit 10, and the cathode of the first diode D1 is connected to the first input terminal of the first comparator U1-1.

[0045] In this embodiment, the first input terminal of the first comparator U1-1 and the first input terminal of the second comparator U1-2 are non-inverting input terminals, and the second input terminal of the first comparator U1-1 and the second input terminal of the second comparator U1-2 are inverting input terminals. When the leakage voltage at the non-inverting input terminal is greater than the first reference voltage at the inverting input terminal, the first voltage comparison signal output by the first comparator U1-1 is a high-level signal, and the signal output circuit 30 outputs a leakage fault signal after receiving the high-level signal, so as to identify that the electrical equipment is in a leakage state through the leakage fault signal, and perform a leakage locking operation to prevent damage to the equipment. The output end of the second comparator U1-2 is connected to the second output end of the reference voltage circuit 10, and the output end of the second comparator U1-2 is connected to the first input end of the first comparator U1-1 through the first diode D1, thereby forming a comparator hysteresis circuit together with the first comparator U1-1. When the leakage voltage is greater than the first reference voltage, the second comparator U1-2 outputs a high-level signal, causing the first diode D1 to be turned on. At this time, the circuit between the second output end of the reference voltage circuit 10 and the first input end of the first comparator U1-1 is connected, and the second reference voltage output from the second output end of the reference voltage circuit 10 can be connected to the first input end of the first comparator U1-1, and the voltage value is fixed, which means that the input voltage of the first input end of the first comparator U1-1 is instantly pulled up to a fixed voltage value at this time, thereby avoiding misjudgment caused by input voltage fluctuations of the first voltage comparison circuit 20 due to noise interference and other reasons, and preventing frequent leakage unlocking actions due to small voltage fluctuations, thereby greatly enhancing the reliability of the leakage detection circuit. It should be noted that, in this embodiment, in order to ensure that the first comparator U1 - 1 can continuously output a high level when the electrical device is in a leakage state, the voltage value of the second reference voltage at the first input terminal is greater than the voltage value of the first reference voltage at the second input terminal.

[0046] Optionally, in some feasible embodiments, reference Figure 3 The second voltage comparison circuit 40 also includes a first resistor R1, one end of the first resistor R1 is respectively connected to the anode of the first diode D1 and the output end of the second comparator U1-2, and the other end of the first resistor R1 is connected to the second output end of the reference voltage circuit 10.

[0047] In this embodiment, in order to limit current and divide voltage, a first resistor R1 is connected in series between the first diode D1 and the second output terminal of the reference voltage circuit 10, that is, the first resistor R1 is connected in series between the first input terminal of the first comparator U1-1 and the second output terminal of the reference voltage circuit 10, thereby improving the stability of the input voltage.

[0048] In one embodiment, reference Figure 3, the reference voltage circuit 10 includes a reference voltage chip U2, a second resistor R2, a third resistor R3, a fourth resistor R4 and a fifth resistor R5;

[0049] The anode of the reference voltage chip U2 is grounded, the cathode of the reference voltage chip U2 is respectively connected to the power supply and one end of the second resistor R2, the other end of the second resistor R2 is respectively connected to the voltage output end of the reference voltage chip U2 and one end of the third resistor R3, the other end of the third resistor R3 is grounded, one end of the fourth resistor R4 is respectively connected to the cathode of the reference voltage chip U2 and the second voltage comparison circuit 40, the other end of the fourth resistor R4 is respectively connected to the second input end of the first voltage comparison circuit 20 and one end of the fifth resistor R5, and the other end of the fifth resistor R5 is grounded.

[0050] In this embodiment, the reference voltage circuit 10 uses a reference voltage chip U2 to generate a high-precision first reference voltage V0 and a second reference voltage VREF. The anode of the reference voltage chip U2 is grounded, and the cathode of the reference voltage chip U2 is connected to the power supply +24V. The reference voltage chip U2 is powered by the power supply +24V. The second resistor R2, the third resistor R3, the fourth resistor R4 and the fifth resistor R5 are voltage-dividing resistors. The voltage output end of the reference voltage chip U2 is the chip reference voltage (for example, 2.5V) of the reference voltage chip U2. According to the resistor voltage-dividing principle, it can be concluded that:

[0051] The first reference voltage V0 = VREF*(R5 / (R4+R5)) = 2.5*(1+R2 / R3)*(R5 / (R4+R5))(1),

[0052] The second reference voltage VREF=2.5*(1+R2 / R3)(2).

[0053] Optionally, in some feasible embodiments, reference Figure 3 In order to ensure the stability of the power supply voltage of the reference voltage chip U2, the reference voltage circuit 10 further includes an eleventh resistor R11, and the cathode of the reference voltage chip U2 is connected to the power supply +24V through the eleventh resistor R11.

[0054] In one embodiment, reference Figure 2 The leakage protection circuit 100 also includes a leakage voltage output circuit 50, an input end of the leakage voltage output circuit 50 is connected to a first end of an insulation resistor of the electrical equipment, a second end of the insulation resistor is connected to a power supply, an output end of the leakage voltage output circuit 50 is connected to a first input end of the first voltage comparison circuit 20, and the leakage voltage output circuit 50 is used to output a leakage voltage.

[0055] In this embodiment, the leakage voltage output circuit 50 is connected to the power supply +24V through the insulation resistance of the electrical equipment. When leakage occurs in the electrical equipment, it indicates that the insulation resistance decreases. At this time, the leakage voltage output by the leakage voltage output circuit 50 increases accordingly. When the leakage voltage is greater than the first reference voltage, the first voltage comparison circuit 20 outputs a first voltage comparison signal to the signal output circuit 30. The signal output circuit 30 then outputs a corresponding leakage fault signal based on the first voltage comparison signal. The leakage fault signal can be used to identify that the electrical equipment is in a leakage state, and the leakage locking operation can be performed synchronously to realize the leakage protection function. At the same time, when the leakage voltage is greater than the first reference voltage, the second voltage comparison circuit 40 outputs a second voltage comparison signal to the first input terminal of the first voltage comparison circuit 20. At this time, the second output terminal of the reference voltage circuit 10 can be connected to the first input terminal of the first voltage comparison circuit 20 to connect the second reference voltage to the first input terminal of the first voltage comparison circuit 20. At this time, the input voltage of the first input terminal of the first voltage comparison circuit 20 can be instantly raised to a fixed voltage value, thereby avoiding misjudgment due to input voltage fluctuations of the first voltage comparison circuit 20 due to noise interference and other reasons, and preventing frequent leakage unlocking actions due to small voltage fluctuations, thereby greatly enhancing the reliability of the leakage detection circuit.

[0056] Optionally, in some feasible embodiments, reference Figure 3 The leakage voltage output circuit 50 includes a sixth resistor R6 and a seventh resistor R7, one end of the sixth resistor R6 is connected to the first end of the insulation resistor, the other end of the sixth resistor R6 is respectively connected to the first input end of the first voltage comparison circuit 20 and one end of the seventh resistor R7, and the other end of the seventh resistor R7 is grounded.

[0057] In this embodiment, the insulation resistance of the electrical equipment, the sixth resistor R6, the seventh resistor R7 and the power supply +24V are connected in series to form a voltage divider circuit, and the first input terminal of the first voltage comparison circuit 20 is connected to the connection node between the sixth resistor R6 and the seventh resistor R7. When leakage occurs in the electrical equipment, that is, the insulation resistance decreases, the input voltage of the first input terminal of the first voltage comparison circuit 20 increases after voltage division, that is, the leakage voltage increases, and when the leakage voltage is greater than the first reference voltage, the first voltage comparison signal is output to the signal output circuit 30. At the same time, when the leakage voltage is greater than the first reference voltage, the second voltage comparison circuit 40 outputs a second voltage comparison signal to the first input terminal of the first voltage comparison circuit 20. At this time, the second output terminal of the reference voltage circuit 10 can be connected to the first input terminal of the first voltage comparison circuit 20 to connect the second reference voltage to the first input terminal of the first voltage comparison circuit 20. At this time, the input voltage of the first input terminal of the first voltage comparison circuit 20 can be instantly raised to a fixed voltage value, thereby avoiding misjudgment due to input voltage fluctuations of the first voltage comparison circuit 20 due to noise interference and other reasons, and preventing frequent leakage unlocking actions due to small voltage fluctuations, thereby greatly enhancing the reliability of the leakage detection circuit.

[0058] In one embodiment, the signal output circuit 30 includes a first switch tube Q1 and a first relay K1;

[0059] The first end of the first switch tube Q1 is connected to the first end of the coil of the first relay K1, the second end of the first switch tube Q1 is grounded, the controlled end of the first switch tube Q1 is connected to the output end of the first voltage comparison circuit 20, and the second end of the coil of the first relay K1 is connected to the power supply.

[0060] In this embodiment, when the signal output circuit 30 receives the first voltage comparison signal output by the first voltage comparison circuit 20, the state changes of the first switch tube Q1 and the first relay K1 can be regarded as leakage fault signals, thereby observing the states of the first switch tube Q1 and the first relay K1 to determine whether the electrical equipment is currently in a leakage state. Specifically, the controlled end of the first switch tube Q1 is connected to the output end of the first voltage comparison circuit 20 for receiving a first voltage comparison signal. The first end and the second end of the first switch tube Q1 are connected in series with the coil of the first relay K1 between the power supply +24V and the ground. The first switch tube Q1 is an NPN transistor, and the first relay K1 is a normally closed relay. When the electrical equipment is in a leakage state, that is, the insulation resistance of the electrical equipment is less than the set leakage action resistance value, the leakage voltage is greater than the first reference voltage, and the first voltage comparison signal output by the first voltage comparison circuit 20 is a high-level signal. At this time, the first switch tube Q1 is turned on, the coil of the first relay K1 is energized, and the contact T+ / T- of the first relay K1 changes from a normally closed action to a normally open action. Then, it can be judged that the electrical equipment is in a leakage fault according to the passive normally open signal output by the circuit. Optionally, in some feasible embodiments, the first switch tube Q1 can also be a PNP type transistor. Correspondingly, when the leakage voltage is greater than the first reference voltage, the first voltage comparison signal output by the first voltage comparison circuit 20 is a low level signal. The first switch tube Q1 can also be a MOS tube, a GTO (gate turn-off thyristor), an IGBT or a driver chip.

[0061] Optionally, in some feasible embodiments, reference Figure 3 The signal output circuit 30 also includes an eighth resistor R8 and a ninth resistor R9, one end of the eighth resistor R8 is connected to the output end of the first voltage comparison circuit 20, the other end of the eighth resistor R8 is respectively connected to the controlled end of the first switch tube Q1 and one end of the ninth resistor R9, and the other end of the ninth resistor R9 is grounded.

[0062] In this embodiment, an eighth resistor R8 and a ninth resistor R9 are provided to divide the voltage outputted from the first voltage comparison circuit 20 to the controlled end of the first switch tube Q1, so as to prevent excessive current from damaging the controlled end of the first switch tube Q1. Meanwhile, the voltage division of the eighth resistor R8 and the ninth resistor R9 can provide a stable operating voltage for the first switch tube Q1, so as to avoid unstable operation of the first switch tube Q1 due to voltage fluctuation.

[0063] In some other feasible embodiments, continue to refer to Figure 3 The signal output circuit 30 also includes a second switch tube Q2, a second end of the second switch tube Q2 is connected to the first end of the coil of the first relay K1, a first end of the second switch tube Q2 is grounded, and a controlled end of the second switch tube Q2 is connected to the first end of the first switch tube Q1.

[0064] In this embodiment, the second switch tube Q2 is a PNP type triode, the controlled end of the second switch tube Q2 is connected to the first end of the first switch tube Q1, the second end of the first switch tube Q1 is grounded, the first end and the second end of the second switch tube Q2 are connected in series with the coil of the first relay K1 between the power supply +24V and the ground, when the electrical device is in a leakage state, that is, when the insulation resistance of the electrical device is less than the set leakage action resistance value, the leakage voltage is greater than the first reference voltage, and the first voltage comparison circuit 20 outputs the first voltage comparison signal, at this time, the first switch tube Q1 is turned on, so that the controlled end of the second switch tube Q2 is grounded, the second switch tube Q2 is turned on, the coil of the first relay K1 is energized, and the contact T+ / T- of the first relay K1 changes from a normally closed action to a normally open action, and then the electrical device can be judged to be in a leakage fault according to the passive normally open signal output by the circuit. Optionally, in some feasible embodiments, the second switch tube Q2 can also be one of a MOS tube, a GTO (gate turn-off thyristor), an IGBT or a driver chip.

[0065] Optionally, in some feasible embodiments, the signal output circuit 30 also includes a twelfth resistor R12 and a thirteenth resistor R13, one end of the twelfth resistor R12 is connected to the power supply, the other end of the twelfth resistor R12 is respectively connected to one end of the thirteenth resistor R13 and the first end of the first switch tube Q1, and the other end of the thirteenth resistor R13 is connected to the controlled end of the second switch tube Q2.

[0066] In this embodiment, when the electrical equipment is in a normal state, that is, the insulation resistance of the electrical equipment is greater than the set leakage action resistance value, the leakage voltage is less than the first reference voltage, and the first voltage comparison signal output by the first voltage comparison circuit 20 is a low-level signal. At this time, the first switch tube Q1 is turned off, and the power supply +24V is connected to the controlled end of the second switch tube Q2 after voltage division through the twelfth resistor R12 and the thirteenth resistor R13. The second switch tube Q2 is turned off at a high level. At this time, the coil of the first relay K1 loses power, and the contact T+ / T- of the first relay K1 is reset from a normally open action to a normally closed action. Then, it can be judged that the electrical equipment has no leakage fault or the leakage fault is relieved according to the passive normally closed signal output by the circuit.

[0067] Optionally, in some feasible embodiments, reference Figure 3 The signal output circuit 30 further includes a second diode D2, an anode of the second diode D2 is connected to a first end of the coil of the first relay K1, and a cathode of the second diode D2 is connected to a second end of the coil of the first relay K1.

[0068] In this embodiment, in order to suppress the reverse electromotive force generated when the coil of the first relay K1 loses power, a second diode D2 is connected in parallel at both ends of the coil of the first relay K1, and the anode of the second diode D2 is connected to the first end of the coil of the first relay K1, and the cathode of the second diode D2 is connected to the second end of the coil of the first relay K1, so as to prevent the reverse electromotive force generated when the coil of the first relay K1 loses power from damaging other electronic components in the circuit.

[0069] In some other feasible embodiments, continue to refer to Figure 3 The signal output circuit 30 also includes a tenth resistor R10 and a light emitting diode D4, one end of the tenth resistor R10 is connected to the anode of the light emitting diode D4, the other end of the tenth resistor R10 is connected to the second end of the coil of the first relay K1, and the cathode of the light emitting diode D4 is connected to the first end of the coil of the first relay K1.

[0070] In this embodiment, in order to facilitate maintenance personnel to quickly know whether the electrical equipment currently has a leakage fault, a light-emitting diode D4 is connected in parallel at both ends of the coil of the first relay K1, and the anode of the light-emitting diode D4 is connected to the power supply through the tenth resistor R10. When the electrical equipment is in a leakage state, the circuit where the coil of the first relay K1 is located is in a conducting state. At this time, the coil of the first relay K1 is energized, and similarly the circuit where the light-emitting diode D4 is located is also turned on. The light-emitting diode D4 is energized and emits light. Therefore, the maintenance personnel can quickly know whether the electrical equipment currently has a leakage fault based on the state of the light-emitting diode D4.

[0071] Optionally, in some feasible embodiments, reference Figure 3 The leakage protection circuit 100 also includes a third diode D3, the cathode of the third diode D3 is connected to the negative electrode of the power supply, and the anode of the third diode D3 is grounded. The third diode D3 can prevent the power supply +24V from being connected in the opposite polarity to damage the circuit.

[0072] The present application also proposes an electrical device, which includes the above-mentioned leakage protection circuit 100. The specific structure of the leakage protection circuit 100 refers to the above-mentioned embodiment. Since the electrical device adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

[0073] In one embodiment, the electrical device may be a frequency converter. In an application, the three-phase power circuit of the frequency converter is indirectly connected through motor coils U, V, and W. Before the frequency converter is powered on, the leakage protection circuit 100 detects the leakage of any of the three phases U, V, and W of the frequency converter output relative to the ground to realize the frequency converter leakage detection function. Taking the output W phase of the inverter for leakage detection against the ground as an example, the output W phase of the inverter is connected to the power supply +24V of the leakage protection circuit 100 through the on-off of the main contact of the second relay K2, and the casing of the inverter is directly connected to the input end (i.e., LD_PE end) of the leakage voltage output circuit 50 of the leakage protection circuit 100. The inverter is in a power-on standby state. First, the main contact of the second relay K2 is energized, which is equivalent to the insulation resistance between the output W phase of the inverter and the casing of the inverter (i.e., the ground end) is connected between the power supply +24V and the input end of the leakage voltage output circuit 50. Then, the leakage protection circuit 100 of the inverter performs leakage detection. When it is detected that the inverter has no leakage fault or the leakage fault is relieved, the main contact of the second relay K2 is disconnected, and the inverter can operate normally, thereby avoiding leakage faults during the normal operation of the inverter.

[0074] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. All equivalent structural changes made using the contents of the present application specification and drawings under the application concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A leakage protection circuit, characterized in that: Applied to electrical equipment, the leakage protection circuit includes a reference voltage circuit, a signal output circuit, a first voltage comparison circuit and a second voltage comparison circuit; The first input terminal of the first voltage comparison circuit is connected to the leakage voltage, the second input terminal of the first voltage comparison circuit is connected to the first output terminal of the reference voltage circuit, the first output terminal of the reference voltage circuit is used to output a first reference voltage, and the first voltage comparison circuit is used to output a first voltage comparison signal when the leakage voltage is greater than the first reference voltage; The input end of the signal output circuit is connected to the output end of the first voltage comparison circuit, and the signal output circuit is used to output a leakage fault signal according to the first voltage comparison signal; The first input terminal of the second voltage comparison circuit and the output terminal of the second voltage comparison circuit are respectively connected to the first input terminal of the first voltage comparison circuit, the second input terminal of the second voltage comparison circuit is connected to the second input terminal of the first voltage comparison circuit, the second voltage comparison circuit is also connected to the second output terminal of the reference voltage circuit, the second output terminal of the reference voltage circuit is used to output a second reference voltage, and the second voltage comparison circuit is used to output a second voltage comparison signal when the leakage voltage is greater than the first reference voltage, so that the second reference voltage is connected to the first input terminal of the first voltage comparison circuit.

2. The leakage protection circuit according to claim 1, characterized in that: The first voltage comparison circuit includes a first comparator, and the second voltage comparison circuit includes a second comparator and a first diode; The first input terminal of the first comparator is connected to the leakage voltage, the second input terminal of the first comparator is connected to the first output terminal of the reference voltage circuit, and the output terminal of the first comparator is connected to the input terminal of the signal output circuit; The first input terminal of the second comparator is connected to the first input terminal of the first comparator, the second input terminal of the second comparator is connected to the second input terminal of the first comparator, the anode of the first diode is respectively connected to the output terminal of the second comparator and the second output terminal of the reference voltage circuit, and the cathode of the first diode is connected to the first input terminal of the first comparator.

3. The leakage protection circuit according to claim 2, characterized in that: The second voltage comparison circuit also includes a first resistor, one end of which is connected to the anode of the first diode and the output end of the second comparator respectively, and the other end of the first resistor is connected to the second output end of the reference voltage circuit.

4. The leakage protection circuit according to claim 1, characterized in that: The reference voltage circuit includes a reference voltage chip, a second resistor, a third resistor, a fourth resistor and a fifth resistor; The anode of the reference voltage chip is grounded, the cathode of the reference voltage chip is respectively connected to the power supply and one end of the second resistor, the other end of the second resistor is respectively connected to the voltage output end of the reference voltage chip and one end of the third resistor, the other end of the third resistor is grounded, one end of the fourth resistor is respectively connected to the cathode of the reference voltage chip and the second voltage comparison circuit, the other end of the fourth resistor is respectively connected to the second input end of the first voltage comparison circuit and one end of the fifth resistor, and the other end of the fifth resistor is grounded.

5. The leakage protection circuit according to claim 1, characterized in that: The leakage protection circuit also includes a leakage voltage output circuit, the input end of the leakage voltage output circuit is connected to the first end of the insulation resistor of the electrical equipment, the second end of the insulation resistor is connected to the power supply, the output end of the leakage voltage output circuit is connected to the first input end of the first voltage comparison circuit, and the leakage voltage output circuit is used to output the leakage voltage.

6. The leakage protection circuit according to claim 5, characterized in that: The leakage voltage output circuit includes a sixth resistor and a seventh resistor, one end of the sixth resistor is connected to the first end of the insulation resistor, the other end of the sixth resistor is respectively connected to the first input end of the first voltage comparison circuit and one end of the seventh resistor, and the other end of the seventh resistor is grounded.

7. The leakage protection circuit according to claim 1, characterized in that: The signal output circuit includes a first switch tube and a first relay; The first end of the first switch tube is connected to the first end of the coil of the first relay, the second end of the first switch tube is grounded, the controlled end of the first switch tube is connected to the output end of the first voltage comparison circuit, and the second end of the coil of the first relay is connected to a power supply.

8. The leakage protection circuit according to claim 7, characterized in that: The signal output circuit further includes an eighth resistor and a ninth resistor, one end of the eighth resistor is connected to the output end of the first voltage comparison circuit, the other end of the eighth resistor is respectively connected to the controlled end of the first switch tube and one end of the ninth resistor, and the other end of the ninth resistor is grounded; And / or, the signal output circuit also includes a second switch tube, the second end of the second switch tube is connected to the first end of the coil of the first relay, the first end of the second switch tube is grounded, and the controlled end of the second switch tube is connected to the first end of the first switch tube.

9. The leakage protection circuit according to any one of claims 7 or 8, characterized in that: The signal output circuit further includes a second diode, an anode of the second diode is connected to the first end of the coil of the first relay, and a cathode of the second diode is connected to the second end of the coil of the first relay; And / or, the signal output circuit also includes a tenth resistor and a light-emitting diode, one end of the tenth resistor is connected to the anode of the light-emitting diode, the other end of the tenth resistor is connected to the second end of the coil of the first relay, and the cathode of the light-emitting diode is connected to the first end of the coil of the first relay.

10. An electrical device, characterized in that: The electrical device comprises the leakage protection circuit according to any one of claims 1 to 9.

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