Relay coil voltage automatic switching circuit and inverter

Abstract

The utility model discloses a relay coil voltage automatic switching circuit and an inverter, and relates to the technical field of inverters. The relay coil voltage automatic switching circuit comprises a contact voltage detection control circuit and a relay power supply circuit. Wherein the contact voltage detection control circuit can detect the main contact voltage of the relay and output a corresponding voltage feedback signal according to the main contact voltage of the relay. And the relay power supply circuit is used for switching the coil voltage output to the relay according to the voltage feedback signal. Thus, when the main contact of the relay is disconnected, the relay power supply circuit can output a high rated voltage to the coil of the relay, and when the main contact of the relay is closed, the relay power supply circuit can output a low holding voltage to the coil of the relay. Therefore, automatic switching of the voltage of the coil of the relay is realized, and the risk that the relay is overheated and even burnt down is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of inverters, and particularly relates to a relay coil voltage automatic switching circuit and an inverter. Background Technique

[0002] An inverter is a key component for converting direct current into alternating current. In the main power circuit on the low-voltage direct current side, a high-power relay is usually used as a switching switch. To prevent the relay from overheating and burning out due to long-term operation at the rated voltage, the relay coil voltage automatic switching circuit will reduce the coil voltage from the rated voltage to the holding voltage after the relay is closed.

[0003] In existing inverters, a method of supplying power from two independent power sources is generally adopted to achieve voltage switching, that is, one path provides the rated voltage and the other path provides the holding voltage, and the switching process is completed by an electronic switch controlled by software. However, if the software control system fails, it may cause the relay coil voltage to fail to be correctly switched to the holding voltage state, easily resulting in overheating and even burning out of the relay. Summary of the Utility Model

[0004] The main purpose of the utility model is to provide a relay coil voltage automatic switching circuit, aiming to solve the problem that the relay is prone to overheating and even burning out when the rated voltage and the holding voltage are switched by software control.

[0005] To achieve the above object, the relay coil voltage automatic switching circuit proposed by the utility model is applied to a relay and includes:

[0006] A contact voltage detection and control circuit, the detection end of the contact voltage detection and control circuit is connected to the main contact of the relay; the contact voltage detection and control circuit is used to detect the main contact voltage of the relay and output a corresponding voltage feedback signal according to the main contact voltage of the relay;

[0007] A relay power supply circuit, the feedback end of the relay power supply circuit is connected to the output end of the contact voltage detection and control circuit, the power output end of the relay power supply circuit is connected to one end of the coil of the relay, and the relay power supply circuit is used to switch the magnitude of the coil voltage output to the relay according to the voltage feedback signal.

[0008] In an embodiment, the relay coil voltage automatic switching circuit further includes:

[0009] A main control circuit, the main control circuit is used to output a first control signal;

[0010] An AND gate circuit, the first input terminal of the AND gate circuit is connected to the output terminal of the contact voltage detection and control circuit, and the second input terminal of the AND gate circuit is connected to the output terminal of the main control circuit; the output terminal of the AND gate circuit is connected to the feedback terminal of the relay power supply circuit; the AND gate circuit is used to output a first logic signal according to the first control signal and the voltage feedback signal;

[0011] The relay power supply circuit is used to switch the magnitude of the coil voltage output to the relay according to the first logic signal.

[0012] In an embodiment, the relay coil voltage automatic switching circuit further includes:

[0013] A drive circuit, one end of the drive circuit is connected to the other end of the coil of the relay; the controlled end of the drive circuit is connected to the control end of the main control circuit; the drive circuit is used to drive the coil of the relay to be energized / de-energized;

[0014] The input terminal of the main control circuit is connected to the output terminal of the contact voltage detection and control circuit; the main control circuit is used to control the operation of the drive circuit according to the voltage feedback signal to control the connection state of the main contact of the relay.

[0015] In an embodiment, the relay power supply circuit includes:

[0016] A feedback circuit, the input terminal of the feedback circuit is the input terminal of the relay power supply circuit; the feedback circuit is used to switch the magnitude of the output feedback voltage according to the first logic signal;

[0017] A switching power supply circuit, the feedback terminal of the switching power supply circuit is connected to the output terminal of the feedback circuit; the power output terminal of the switching power supply circuit is connected to one end of the coil of the relay; the switching power supply circuit is used to switch the magnitude of the coil voltage output to the relay according to the feedback voltage.

[0018] In an embodiment, the feedback circuit includes a first resistor, a second resistor, a third resistor and a first switching tube;

[0019] Wherein, the controlled end of the first switching tube is connected to the input terminal of the feedback circuit; the first end of the first switching tube is connected to one end of the third resistor; the other end of the third resistor, one end of the first resistor, and one end of the second resistor are connected to the feedback terminal of the switching power supply circuit; the other end of the first resistor is connected to the power output terminal of the switching power supply circuit; the other end of the second resistor and the second end of the first switching tube are grounded.

[0020] In one embodiment, the contact voltage detection and control circuit includes a differential amplifier and a comparator; the main contacts of the relay include a first main contact end and a second main contact end;

[0021] The first input terminal of the differential amplifier is connected to the first main contact end of the relay, the second input terminal of the differential amplifier is connected to the second main contact end of the relay, and the output terminal of the differential amplifier is connected to the positive input terminal of the comparator; the negative input terminal of the comparator is connected to the reference voltage input terminal of the contact voltage detection and control circuit; the output terminal of the comparator is connected to the output terminal of the contact voltage detection and control circuit.

[0022] In one embodiment, the contact voltage detection and control circuit further includes a filter circuit. The first input terminal of the filter circuit is connected to the first main contact end of the relay, the second input terminal of the filter circuit is connected to the second main contact end of the relay, the first output terminal of the filter circuit is connected to the first input terminal of the differential amplifier, and the second output terminal of the filter circuit is connected to the second input terminal of the differential amplifier.

[0023] In one embodiment, the relay coil voltage automatic switching circuit further includes a delay circuit. The input terminal of the delay circuit, the output terminal of the contact voltage detection and control circuit, and the input terminal of the main control circuit are connected. The output terminal of the delay circuit is connected to the first input terminal of the AND gate circuit.

[0024] The present invention also provides an inverter, which includes a relay and the relay coil voltage automatic switching circuit as described above.

[0025] In one embodiment, the power input terminal of the inverter is connected to the first main contact end of the relay; the inverter further includes a main power circuit. The power input terminal of the main power circuit is connected to the second main contact end of the relay, and the main power circuit is used to convert a DC power supply into an AC power supply for output.

[0026] The technical solution of the present utility model adopts a relay coil voltage automatic switching circuit, including a contact voltage detection and control circuit and a relay power supply circuit. Among them, when the main contact of the relay is in the open state, the contact voltage detection and control circuit can detect that the main contact of the relay is in the open state according to the corresponding voltage value between the main contacts, and output a corresponding voltage feedback signal. The relay power supply circuit can output a larger rated voltage to the coil of the relay according to the voltage feedback signal, so that the coil can generate an adsorption force sufficient to adsorb the main contact for closing action, and the relay can actively close. When the main contact of the relay is in the closed state, the contact voltage detection and control circuit can detect that the main contact of the relay is in the closed state according to the corresponding voltage value between the main contacts, and output a corresponding voltage feedback signal. The relay power supply circuit can output a smaller holding voltage to the coil of the relay according to the voltage feedback signal, so that the coil can generate an adsorption force sufficient to maintain the closed state of the main contact, and the relay can maintain the closed state. In this way, the present utility model can control the switching of the relay coil voltage by detecting the connection state of the main contact of the relay, automatically switch and output the holding voltage to the coil of the relay when the main contact of the relay is in the closed state, realizing the automatic switching of the relay coil voltage. Compared with the prior art, it avoids the situation that the relay coil voltage cannot be correctly switched to the holding voltage state due to the failure of the software control system, and reduces the risk of the relay overheating or even burning out. Brief Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0028] Figure 1 It is a schematic structural diagram of an embodiment of the relay coil voltage automatic switching circuit provided by the present utility model;

[0029] Figure 2 It is a schematic structural diagram of another embodiment of the relay coil voltage automatic switching circuit provided by the present utility model;

[0030] Figure 3 It is an electronic structure diagram of an embodiment of the inverter provided by the present utility model.

[0031] Explanation of the reference numerals in the drawings:

[0032]

[0033] The realization, functional features and advantages of the present utility model will be further described in conjunction with the embodiments with reference to the accompanying drawings. Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all embodiments. Based on the embodiments in the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0035] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present utility model are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0036] In addition, the descriptions involving "first", "second", etc. in the present utility model are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions appears to be contradictory or unable to be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present utility model.

[0037] In existing inverters, generally, a method of supplying power by two independent power supplies is adopted to achieve voltage switching, that is, one path provides the rated voltage and the other path provides the holding voltage, and the switching process is completed by an electronic switch controlled by software. However, if the software control system fails, it may cause the coil voltage of the relay to fail to correctly switch to the holding voltage state, easily resulting in overheating or even burning of the relay.

[0038] The present utility model proposes an automatic switching circuit 100 for the coil voltage of a relay.

[0039] Please refer to Figure 1 , in an embodiment of the present utility model, the automatic switching circuit 100 for the coil voltage of the relay is applied to a relay K1 and includes:

[0040] A contact voltage detection and control circuit 110, the detection end of the contact voltage detection and control circuit 110 is connected to the main contact of the relay K1; the contact voltage detection and control circuit 110 is used to detect the main contact voltage of the relay K1 and output a corresponding voltage feedback signal according to the main contact voltage of the relay K1.

[0041] It should be noted that the main contacts of relay K1 include a first main contact end and a second main contact end. When the current in the coil of relay K1 is relatively large, the coil can attract the main contacts to close; when the current in the coil of relay K1 is relatively small or there is no current, the coil stops attracting and the main contacts open.

[0042] It should be noted that the contact voltage detection and control circuit 110 can detect the voltage value between the first main contact end and the second main contact end, and generate a corresponding voltage feedback signal.

[0043] Specifically, the contact voltage detection and control circuit 110 can include a filtering circuit, a voltage detection circuit, and a comparison circuit. Among them, the filtering circuit can filter the voltage signal output from the first main contact end and the second main contact end through filters such as an RC low-pass filter. The voltage detection circuit can collect the voltage value between the first main contact end and the second main contact end through devices such as a sampling resistor or an operational amplifier. The comparison circuit can compare the voltage value between the first main contact end and the second main contact end with a reference voltage value to output a voltage feedback signal of high level or low level. For example, when the main contacts of relay K1 are open, the voltage value between the first main contact end and the second main contact end is relatively large, then the voltage detection circuit can detect this voltage value, and the comparison circuit can compare this voltage value with the reference voltage to output a corresponding voltage feedback signal, such as outputting a high level. When the main contacts of relay K1 are closed, the voltage value between the first main contact end and the second main contact end is relatively small, then the voltage detection circuit can detect this voltage value, and the comparison circuit can compare this voltage value with the reference voltage to output a corresponding voltage feedback signal, such as outputting a low level. In this way, the contact voltage detection and control circuit 110 can detect the main contact voltage of relay K1 and output a corresponding voltage feedback signal according to the main contact voltage of relay K1.

[0044] The relay power supply circuit 120, the feedback end of the relay power supply circuit 120 is connected to the output end of the contact voltage detection and control circuit 110, the power output end of the relay power supply circuit 120 is connected to one end of the coil of relay K1, and the relay power supply circuit 120 is used to switch the magnitude of the coil voltage output to relay K1 according to the voltage feedback signal.

[0045] It should be noted that in the state where the main contacts of the relay K1 are disconnected, the relay power supply circuit 120 needs to provide a rated voltage to ensure that the current in the coil of the relay K1 is large enough to generate an adsorption force sufficient to move the main contacts from the disconnected state to the closed state. When the main contacts of the relay K1 are closed, only an adsorption force to maintain the closed state of the main contacts is required, and the relay power supply circuit 120 can provide a holding voltage lower than the rated voltage. In this way, the power consumption of the relay K1 can be reduced, and the risk of overheating or even burning of the relay K1 can be reduced. In this embodiment, the relay power supply circuit 120 can provide the rated voltage / holding voltage to the coil of the relay K1 according to the voltage feedback signal.

[0046] Specifically, the relay power supply circuit 120 can include a power supply circuit and a power supply circuit feedback network. The power supply circuit can provide a rated voltage or a holding voltage, and the power supply circuit feedback network can output different control signals according to the voltage feedback signal to control the power supply circuit to output the rated voltage to the coil of the relay K1 or the holding voltage to the coil of the relay K1. For example, when the contact voltage detection and control circuit 110 outputs a high level, the power supply circuit feedback network outputs a first feedback voltage to control the power supply circuit to output the rated voltage to the coil of the relay K1. At this time, the main contacts of the relay K1 are in the disconnected state. When the relay K1 receives a closing control signal, the relay power supply circuit 120 can provide a sufficient rated voltage to the coil of the relay K1, so that the coil can generate an adsorption force sufficient to adsorb the main contacts to perform a closing action, and the relay K1 can actively close. When the contact voltage detection and control circuit 110 outputs a low level, the power supply circuit feedback network outputs a second feedback voltage to control the power supply circuit to output the holding voltage to the coil of the relay K1. At this time, the main contacts of the relay K1 are in the closed state, and the relay power supply circuit 120 can provide the holding voltage to the coil of the relay K1, so that the coil can generate an adsorption force sufficient to maintain the closed state of the main contacts, and the relay K1 can maintain the closed state.

[0047] In this embodiment, the contact voltage detection and control circuit 110 can detect the main contact voltage of the relay K1 and output a corresponding voltage feedback signal according to the main contact voltage of the relay K1. The relay power supply circuit 120 can switch the magnitude of the coil voltage output to the relay K1 according to the voltage feedback signal. In this way, when the main contact of the relay K1 is in the open state, the contact voltage detection and control circuit 110 can detect that the main contact of the relay K1 is in the open state according to the corresponding voltage value between the main contacts and output a corresponding voltage feedback signal. The relay power supply circuit 120 can output a larger rated voltage to the coil of the relay K1 according to the voltage feedback signal, so that the coil can generate an adsorption force sufficient to adsorb the main contact for closing, and the relay K1 can actively close. When the main contact of the relay K1 is in the closed state, the contact voltage detection and control circuit 110 can detect that the main contact of the relay K1 is in the closed state according to the corresponding voltage value between the main contacts and output a corresponding voltage feedback signal. The relay power supply circuit 120 can output a smaller holding voltage to the coil of the relay K1 according to the voltage feedback signal, so that the coil can generate an adsorption force sufficient to maintain the closed state of the main contact, and the relay K1 can maintain the closed state. In this way, this embodiment can control the switching of the coil voltage of the relay K1 by detecting the connection state of the main contact of the relay K1, and automatically switch the output to the holding voltage of the coil of the relay K1 when the main contact of the relay K1 is in the closed state, realizing the automatic switching of the coil voltage of the relay K1. Compared with the prior art, it avoids the situation that the coil voltage of the relay K1 cannot be correctly switched to the holding voltage state due to a failure of the software control system, and reduces the risk of overheating or even burning of the relay K1.

[0048] In the present utility model, when the main contacts of relay K1 are in the open state, the contact voltage detection and control circuit 110 can detect that the main contacts of relay K1 are in the open state according to the corresponding voltage value between the main contacts, and output a corresponding voltage feedback signal. The relay power supply circuit 120 can output a relatively large rated voltage to the coil of relay K1 according to the voltage feedback signal, so that the coil can generate an adsorption force sufficient to adsorb the main contacts for closing action, and relay K1 can actively close. When the main contacts of relay K1 are in the closed state, the contact voltage detection and control circuit 110 can detect that the main contacts of relay K1 are in the closed state according to the corresponding voltage value between the main contacts, and output a corresponding voltage feedback signal. The relay power supply circuit 120 can output a relatively small holding voltage to the coil of relay K1 according to the voltage feedback signal, so that the coil can generate an adsorption force sufficient to maintain the closed state of the main contacts, and relay K1 can maintain the closed state. Thus, the present utility model can detect the connection state of the main contacts of relay K1, control the switching of the coil voltage of relay K1, and automatically switch to output the holding voltage to the coil of relay K1 when the main contacts of relay K1 are in the closed state, realizing the automatic switching of the coil voltage of relay K1. Compared with the prior art, it avoids the situation that the coil voltage of relay K1 cannot be correctly switched to the holding voltage state due to the failure of the software control system, and reduces the risk of overheating or even burning of relay K1.

[0049] Please refer to Figure 2 , in an embodiment of the present utility model, the relay coil voltage automatic switching circuit 100 further includes:

[0050] The main control circuit 130, which is used to output a first control signal;

[0051] The AND gate circuit 140, the first input end of the AND gate circuit 140 is connected to the output end of the contact voltage detection and control circuit 110, and the second input end of the AND gate circuit 140 is connected to the output end of the main control circuit 130; the output end of the AND gate circuit 140 is connected to the feedback end of the relay power supply circuit 120; the AND gate circuit 140 is used to output a first logic signal according to the first control signal and the voltage feedback signal;

[0052] The relay power supply circuit 120 is used to switch the magnitude of the coil voltage output to relay K1 according to the first logic signal.

[0053] In this embodiment, the AND gate circuit 140 can be composed of multiple switching tubes, and the output is high level only when both inputs are high level at the same time, otherwise it is low level.

[0054] It should be noted that, in order to further strengthen the protection of the relay K1 and realize the switching from the rated voltage to the holding voltage. This embodiment further includes a main control circuit 130, which can perform dual switching control with the contact voltage detection and control circuit 110. In this way, when the contact voltage detection and control circuit 110 malfunctions, the main control circuit 130 can control the switching output of the holding voltage by outputting a first control signal, avoiding the coil voltage of the relay K1 from being input with a relatively large rated voltage for a long time due to the malfunction of the contact voltage detection and control circuit 110.

[0055] Specifically, when the contact voltage detection and control circuit 110 is working normally, when the main contact of the relay K1 is disconnected, the contact voltage detection and control circuit 110 can output a high level. At this time, the first control signal of the main control circuit 130 also outputs a high level. Then, the AND gate circuit 140 performs a logical judgment and outputs a first logical signal with a high level. Then, the relay power supply circuit 120 outputs the rated voltage to the coil of the relay K1. When the main contact of the relay K1 is switched from the disconnected state to the closed state, the contact voltage detection and control circuit 110 outputs a low level. Among them, the main control circuit 130 can be set by software to output a high level within the first time when the main contact of the relay K1 is switched from the disconnected state to the closed state, and output a low level after the first time. Then, the AND gate circuit 140 performs a logical judgment and outputs a first logical signal with a low level. The relay power supply circuit 120 outputs the holding voltage to the coil of the relay K1.

[0056] If, when the main contact of the relay K1 is switched from the disconnected state to the closed state, the contact voltage detection and control circuit 110 malfunctions and still outputs a high level. Due to the software setting of the main control circuit 130, a low level is output after the first time. Then, the first logical signal output by the AND gate circuit 140 after the first time is a low level. The relay power supply circuit 120 can still switch and output the holding voltage to the coil of the relay K1 after the first time. In this way, it can be ensured that the control switching of the coil voltage of the relay K1 can be completed even when the contact voltage detection and control circuit 110 malfunctions. In this way, the reliability of the circuit switching output in this embodiment is enhanced.

[0057] Please refer to Figure 2 , in an embodiment of the present invention, the relay coil voltage automatic switching circuit 100 further includes:

[0058] A drive circuit 150, one end of the drive circuit 150 is connected to the other end of the coil of the relay K1; the controlled end of the drive circuit 150 is connected to the control end of the main control circuit 130; the drive circuit 150 is used to drive the coil of the relay K1 to be energized / de-energized;

[0059] The input end of the main control circuit 130 is connected to the output end of the contact voltage detection and control circuit 110; the main control circuit 130 is used to control the operation of the drive circuit 150 according to the voltage feedback signal, so as to control the connection state of the main contact of the relay K1.

[0060] It should be noted that the other end of the drive circuit 150 can be connected to a low voltage, such as grounded. The drive circuit 150 can include a switching tube, and by controlling the conduction state of the switching tube, the magnitude of the drive current output to the coil of the relay K1 can be controlled.

[0061] It should be noted that the main control circuit 130 can output a relay control signal, and the drive circuit 150 can convert the relay control signal into a drive current for driving the coil of the relay K1. For example, when the main control circuit 130 outputs a high level, the drive circuit 150 outputs a drive current, and the coil of the drive relay K1 is energized to generate an adsorption force, controlling the main contact of the relay K1 to close; when the main control circuit 130 outputs a low level, the drive circuit 150 stops outputting the drive current, the coil of the drive relay K1 is de-energized, and the main contact of the relay K1 is controlled to open.

[0062] In this embodiment, the main control circuit 130 can monitor the connection state of the main contact of the relay K1 according to the voltage feedback signal. For example, when the main control circuit 130 controls the drive circuit 150 to drive the coil of the relay K1 to be energized, under the preset state, the main contact of the relay K1 will be in the closed state, and at this time, the main control circuit 130 receives a low-level voltage feedback signal. If a low-level voltage feedback signal cannot be received within the set time, the relay K1 may have some faults, and the main control circuit 130 can control the drive circuit 150 to drive the coil of the relay K1 to be de-energized and not work, so as to avoid further damage to the circuit.

[0063] Please refer to Figure 2 , in an embodiment of the present invention, the relay power supply circuit 120 includes:

[0064] A feedback circuit 121, the input end of the feedback circuit 121 is the input end of the relay power supply circuit 120; the feedback circuit 121 is used to switch the magnitude of the output feedback voltage according to the first logic signal;

[0065] A switching power supply circuit 122, the feedback end of the switching power supply circuit 122 is connected to the output end of the feedback circuit 121; the power output end of the switching power supply circuit 122 is connected to one end of the coil of the relay K1; the switching power supply circuit 122 is used to switch the magnitude of the voltage output to the coil of the relay K1 according to the feedback voltage.

[0066] In this embodiment, the feedback circuit 121 can be composed of a resistor and a switching transistor, and can change the power output of the switching power supply circuit 122. The switching power supply circuit 122 can include a buck circuit. For example, when the first logic signal is at a high level, the feedback circuit 121 can output a first feedback voltage to the switching power supply circuit 122 to control the buck circuit to stop working and directly output a rated voltage. When the first logic signal is at a low level, the feedback circuit 121 can output a second feedback voltage to the switching power supply circuit 122 to control the buck circuit to work, step down the rated voltage to a holding voltage and output it to the coil of the relay K1. In this way, the switching power supply circuit 122 of this embodiment can output a rated voltage / holding voltage to the coil of the relay K1.

[0067] Please refer to Figure 3 , in an embodiment of the present invention, the feedback circuit 121 includes a first resistor R1, a second resistor R2, a third resistor R3 and a first switching transistor Q1;

[0068] Among them, the controlled end of the first switching transistor Q1 is connected to the input end of the feedback circuit 121; the first end of the first switching transistor Q1 is connected to one end of the third resistor R3; the other end of the third resistor R3, one end of the first resistor R1, and one end of the second resistor R2 are connected to the feedback end of the switching power supply circuit 122; the other end of the first resistor R1 is connected to the power output end of the switching power supply circuit 122; the other end of the second resistor R2 and the second end of the first switching transistor Q1 are grounded.

[0069] In this embodiment, the first switching transistor Q1 can be an NMOS transistor. When a high level is input to the input end of the feedback circuit 121, the first switching transistor Q1 conducts, and at this time, the voltage of the output of the switching power supply circuit 122 to the coil of the relay K1 is Vrelay1 = (1 + R1 / (R2 / / R3)) * VFB. Among them, Vrelay1 is a higher rated voltage, VFB is the voltage at the feedback end of the switching power supply circuit 122, and R2 / / R3 represents the total resistance after the resistors R2 and R3 are connected in parallel. When a low level is input to the input end of the feedback circuit 121, the first switching transistor Q1 is turned off, and at this time, the voltage of the output of the switching power supply circuit 122 to the coil of the relay K1 is Vrelay2 = (1 + R1 / R2) * VFB. Among them, Vrelay2 is a lower holding voltage, and Vrelay1 > Vrelay2.

[0070] Please refer to Figure 3 , in an embodiment of the present invention, the contact voltage detection and control circuit 110 includes a differential amplifier U1 and a comparator U2; the main contacts of the relay K1 include a main contact first end and a main contact second end;

[0071] The first input terminal of the differential amplifier U1 is connected to the first end of the main contact of the relay K1, the second input terminal of the differential amplifier U1 is connected to the second end of the main contact of the relay K1, and the output terminal of the differential amplifier U1 is connected to the positive input terminal of the comparator U2; the negative input terminal of the comparator U2 is connected to the reference voltage input terminal of the contact voltage detection and control circuit 110; the output terminal of the comparator U2 is connected to the output terminal of the contact voltage detection and control circuit 110.

[0072] In this embodiment, the differential amplifier U1 can amplify the voltage difference between the first end and the second end of the main contact of the relay K1. The specific amplification factor can be selected according to actual needs and then output to the comparator U2. The comparator U2 can compare the output of the differential amplifier U1 with the reference voltage, where the reference voltage can be selected according to actual needs. When the first end and the second end of the main contact of the relay K1 are disconnected, the output of the differential amplifier U1 is greater than the reference voltage, and a high level is output; when the first end and the second end of the main contact of the relay K1 are closed and the output of the differential amplifier U1 is less than the reference voltage, a low level is output.

[0073] Please refer to Figure 3 , in an embodiment of the present invention, the contact voltage detection and control circuit 110 further includes a filtering circuit 111. The first input terminal of the filtering circuit 111 is connected to the first end of the main contact of the relay K1, the second input terminal of the filtering circuit 111 is connected to the second end of the main contact of the relay K1, the first output terminal of the filtering circuit 111 is connected to the first input terminal of the differential amplifier U1, and the second output terminal of the filtering circuit 111 is connected to the second input terminal of the differential amplifier U1.

[0074] In this embodiment, the filtering circuit 111 can filter out the high-frequency signals input by the voltage of the main contact of the relay K1 to prevent high-frequency interference from entering the subsequent differential amplification circuit. The filtering circuit 111 can adopt an RC low-pass filtering circuit or other circuit forms.

[0075] Please refer to Figure 2 , in an embodiment of the present invention, the relay coil voltage automatic switching circuit 100 further includes a delay circuit 160. The input terminal of the delay circuit 160, the output terminal of the contact voltage detection and control circuit 110 are connected to the input terminal of the main control circuit 130, and the output terminal of the delay circuit 160 is connected to the first input terminal of the AND gate circuit 140.

[0076] In this embodiment, the delay circuit 160 can delay the output of the comparator U2. The specific time can be set according to the actual situation. It can filter out the output interference of the comparator U2 and ensure the anti-interference ability of the circuit. An RC delay circuit or other circuit forms can be used. In addition, the delay circuit 160 can also ensure that when the relay K1 has passed the delay time and the main contact is in a stable closed state, the input of the coil voltage is switched to the holding voltage.

[0077] The present utility model also proposes an inverter, which includes a relay K1 and a relay coil voltage automatic switching circuit 100. The specific structure of the relay coil voltage automatic switching circuit 100 refers to the above embodiment. Since this inverter adopts all the technical solutions of the above all embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated here one by one.

[0078] Please refer to Figure 3 , in an embodiment of the present utility model, the power input terminal Vdc of the inverter is connected to the first end of the main contact of the relay K1; the inverter further includes a main power circuit 200, and the power input terminal of the main power circuit 200 is connected to the second end of the main contact of the relay K1. The main power circuit 200 is used to convert the DC power supply into an AC power supply for output.

[0079] In this embodiment, the main power circuit 200 is a power conversion partial circuit of the inverter. The input is a DC power supply, such as 48V or other voltage levels, and the output is an AC power supply. In this embodiment, the switching of the coil voltage of the relay K1 can be controlled by detecting the connection state of the main contact of the relay K1. When the main contact of the relay K1 is in the closed state, the output holding voltage is automatically switched, realizing the automatic switching of the coil voltage of the relay K1. Compared with the prior art, it avoids the situation that the coil voltage of the relay K1 cannot be correctly switched to the holding voltage state due to the failure of the software control system, reduces the power consumption of the inverter, reduces the risk of damage to the main power circuit 200 caused by the relay K1, and improves the reliability and safety of the inverter.

[0080] Please refer to Figure 3 , in an embodiment of the present utility model, the relay K1 is a high-power relay K1 with a relatively large current-carrying capacity, which is composed of a driving coil and a main contact, and serves as a switching switch for the main power circuit 200 on the low-voltage DC side of the inverter. The following combines Figure 3 to elaborate the specific working process of this embodiment as follows:

[0081] After the inverter is powered on, the relay control signal output by the main control circuit 130 to the drive circuit 150 defaults to a low level, the first control signal output by the main control circuit 130 to the AND gate circuit 140 defaults to a high level, the high-power relay K1 is default open, the main contact voltage is relatively large, passes through the filter circuit 111, and is input to the differential amplifier U1. The output of the differential amplifier U1 is relatively large, is input to the comparator U2, and is compared with the reference voltage value Vref. If it is greater than the reference voltage Vref, the comparator U2 outputs a high level, then passes through the delay circuit 160, and is input to the AND gate circuit 140. Among them, the AND gate circuit 140 outputs a high level only when both inputs are high levels, otherwise it outputs a low level. Then the output of the AND gate circuit 140 is also a high level, the first switching transistor Q1 conducts, one end of the third resistor R3 is connected to the reference ground, the second resistor R2 is in parallel with the third resistor R3, and the output of the switching power supply circuit 122 is

[0082] Vrelay1 = (1 + R1 / (R2 / / R3)) * VFB;

[0083] Among them, VFB is the feedback terminal voltage of the switching power supply circuit 122, and Vrelay1 is the rated voltage output by the switching power supply circuit 122 to the coil of the relay K1.

[0084] In addition, the comparator U2 outputs a high level to the main control circuit 130, feeding back the connection state of the main contact of the relay K1 to the main control circuit 130. At this time, the state of the relay K1 is the state of not receiving the control signal for actively closing the main contact, and the main contact is not closed.

[0085] When the inverter starts to work, the relay control signal output by the main control circuit 130 to the drive circuit 150 is a high level. The drive circuit 150 outputs a drive signal to control the high-power relay K1 to perform a closing action. When starting to close, the main contact voltage drops rapidly. After completion of closing, the main contact voltage is relatively small, passes through the filter circuit 111, is input to the differential amplifier U1. The output of the differential amplifier U1 is relatively small, is input to the comparator U2, and is compared with the reference voltage value Vref. If it is less than the reference voltage value Vref, the comparator U2 outputs a low level, then passes through the delay circuit 160, and is input to the AND gate circuit 140. At this time, the first control signal output by the main control circuit 130 to the AND gate circuit 140 is still a high level, then the output of the AND gate circuit 140 is a low level, the first switching transistor Q1 is turned off, one end of the third resistor R3 is disconnected from the reference ground, and the output of the switching power supply circuit 122 is

[0086] Vrelay2 = (1 + R1 / R2) * VFB;

[0087] Among them, VFB is the feedback terminal voltage of the switching power supply circuit 122, and Vrelay2 is the holding voltage output from the switching power supply circuit 122 to the coil of the relay K1, and Vrelay2 is less than Vrelay1.

[0088] After the first time set by the software of the main control circuit 130, the first control signal output by the main control circuit 130 to the AND gate circuit 140 is at a low level, then the output of the AND gate circuit 140 is still at a low level, and the first switching transistor Q1 remains in the off state, and the switching power supply circuit 122 outputs Vrelay2. In this way, it can be ensured that when the contact voltage detection and control circuit 110 makes a mistake, the main control circuit 130 can also complete the switching of the rated voltage of the relay K1 coil to the holding voltage.

[0089] In addition, the comparator U2 outputs a low level and inputs it to the main control circuit 130, feeding back the state of the relay K1 to the main control circuit 130. At this time, the state of the relay K1 is the state of having received the control signal for controlling the main contact to actively close, and the main contact has been closed.

[0090] Among them, if the voltage feedback signal of the main contact closing cannot be received within the set time, the main control circuit 130 can control the drive circuit 150 to send a drive signal to disconnect the closed state of the main contact of the relay K1, thereby protecting the inverter.

[0091] In this way, after the main control circuit 130 issues a relay control signal to close the relay K1, when the logic of the first control signal output by the main control circuit 130 to the AND gate circuit 140 is incorrect, or when an error occurs in the output of the contact voltage detection and control circuit 110, the switching of the relay K1 coil voltage can be completed. In terms of control, the setting priority of the contact voltage detection and control circuit 110 can be higher than the control of the first control signal of the main control circuit 130 because the contact voltage detection and control circuit 110 is not easily affected by the environment and the circuit implementation is more reliable.

[0092] In this embodiment, after the high-power relay K1 is correctly closed, the power input to the power input terminal of the inverter can be connected to the main power circuit 200, and the conversion from DC power to AC power can be performed, and the inverter can work normally and output AC power. In this way, the inverter of this embodiment has lower power consumption and stronger reliability.

[0093] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structural transformation made under the technical concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied to other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. An automatic switching circuit for relay coil voltage, applied to a relay, characterized in that, Comprising: A contact voltage detection and control circuit, the detection end of the contact voltage detection and control circuit is connected to the main contact of the relay; The contact voltage detection and control circuit is used to detect the main contact voltage of the relay and output a corresponding voltage feedback signal according to the main contact voltage of the relay; A relay power supply circuit, the feedback end of the relay power supply circuit is connected to the output end of the contact voltage detection and control circuit, the power output end of the relay power supply circuit is connected to one end of the coil of the relay, and the relay power supply circuit is used to switch the magnitude of the coil voltage output to the relay according to the voltage feedback signal.

2. The automatic relay coil voltage switching circuit according to claim 1, characterized in that Further comprising: A main control circuit, the main control circuit is used to output a first control signal; An AND gate circuit, the first input end of the AND gate circuit is connected to the output end of the contact voltage detection and control circuit, and the second input end of the AND gate circuit is connected to the output end of the main control circuit; the output end of the AND gate circuit is connected to the feedback end of the relay power supply circuit; the AND gate circuit is used to output a first logic signal according to the first control signal and the voltage feedback signal; The relay power supply circuit is used to switch the magnitude of the coil voltage output to the relay according to the first logic signal.

3. The automatic switching circuit for the relay coil voltage according to claim 2, wherein Further comprising: A drive circuit, one end of the drive circuit is connected to the other end of the coil of the relay; the controlled end of the drive circuit is connected to the control end of the main control circuit; The drive circuit is used to drive the coil of the relay to be energized / de-energized; The input end of the main control circuit is connected to the output end of the contact voltage detection and control circuit; the main control circuit is used to control the operation of the drive circuit according to the voltage feedback signal to control the connection state of the main contact of the relay.

4. The automatic switching circuit for the relay coil voltage according to claim 2, wherein The relay power supply circuit includes: A feedback circuit, the input end of the feedback circuit is the input end of the relay power supply circuit; the feedback circuit is used to switch the magnitude of the output feedback voltage according to the first logic signal; A switching power supply circuit, the feedback end of the switching power supply circuit is connected to the output end of the feedback circuit; the power output end of the switching power supply circuit is connected to one end of the coil of the relay; the switching power supply circuit is used to switch the magnitude of the coil voltage output to the relay according to the feedback voltage.

5. The automatic switching circuit for relay coil voltage according to claim 4, characterized in that, The feedback circuit includes a first resistor, a second resistor, a third resistor and a first switching tube; Wherein, the controlled end of the first switching tube is connected to the input end of the feedback circuit; the first end of the first switching tube is connected to one end of the third resistor; the other end of the third resistor, one end of the first resistor, and one end of the second resistor are connected to the feedback end of the switching power supply circuit; the other end of the first resistor is connected to the power output end of the switching power supply circuit; the other end of the second resistor is grounded with the second end of the first switching tube.

6. The automatic switching circuit for the relay coil voltage according to claim 1, wherein The contact voltage detection and control circuit includes a differential amplifier and a comparator; the main contact of the relay includes a main contact first end and a main contact second end; The first input terminal of the differential amplifier is connected to the first end of the main contact of the relay, the second input terminal of the differential amplifier is connected to the second end of the main contact of the relay, and the output terminal of the differential amplifier is connected to the non-inverting input terminal of the comparator; the inverting input terminal of the comparator is connected to the reference voltage input terminal of the contact voltage detection and control circuit; the output terminal of the comparator is connected to the output terminal of the contact voltage detection and control circuit.

7. The automatic relay coil voltage switching circuit according to claim 6, wherein The contact voltage detection and control circuit further includes a filter circuit. The first input terminal of the filter circuit is connected to the first end of the main contact of the relay, the second input terminal of the filter circuit is connected to the second end of the main contact of the relay, the first output terminal of the filter circuit is connected to the first input terminal of the differential amplifier, and the second output terminal of the filter circuit is connected to the second input terminal of the differential amplifier.

8. The automatic switching circuit for relay coil voltage according to claim 3, wherein It further includes a delay circuit. The input terminal of the delay circuit, the output terminal of the contact voltage detection and control circuit are connected to the input terminal of the main control circuit, and the output terminal of the delay circuit is connected to the first input terminal of the AND gate circuit.

9. An inverter, characterized in that, It includes a relay and a relay coil voltage automatic switching circuit according to any one of claims 1 to 8.

10. The inverter according to claim 9, characterized in that, The power input terminal of the inverter is connected to the first end of the main contact of the relay; the inverter further includes a main power circuit. The power input terminal of the main power circuit is connected to the second end of the main contact of the relay, and the main power circuit is used to convert a DC power supply into an AC power supply for output.

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