Three-phase high-voltage and low-voltage inverter circuit, inverter and air conditioner

Abstract

The utility model discloses a three-phase high-voltage and low-voltage inverter circuit, an inverter and an air conditioner, relates to the technical field of inverter circuits, and discloses a three-phase high-voltage and low-voltage inverter circuit comprising a low-voltage pre-charging unit of which the input end is connected with a zero line; the input end of the high-voltage pre-charging unit is connected with the live wire; the input end of the low-voltage inversion unit is connected with the output end of the low-voltage pre-charging unit, and the output end of the low-voltage inversion unit is connected with an external low-voltage motor; the input end of the rectifying unit is connected with the output end of the high-voltage pre-charging unit; the input end of the high-voltage inversion unit is connected with the output end of the rectification unit, the output end of the high-voltage inversion unit is connected with an external high-voltage motor, and the high-voltage inversion unit, the rectification unit and the low-voltage inversion unit are in common ground. According to the invention, the cost of the three-phase high-voltage and low-voltage inverter circuit is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of inverter circuits, and in particular to a three-phase high-voltage and low-voltage inverter circuit, an inverter, and an air conditioner. Background Art

[0002] As inverter circuits are used more and more widely in different fields, users have also put forward higher requirements for inverter circuits, especially three-phase high-voltage and low-voltage inverter circuits (circuits that require inverter output to drive high-voltage motors and low-voltage motors).

[0003] The traditional three-phase high-voltage and low-voltage inverter circuit draws power directly from the bus after three-phase rectification, and uses two high-voltage-resistant high-voltage inverter modules to drive the high-voltage motor and the low-voltage motor respectively. This three-phase high-voltage and low-voltage inverter circuit has a big defect, and there is a phenomenon that two high-voltage-resistant high-voltage inverter modules are needed. That is, this three-phase high-voltage and low-voltage inverter circuit will cause the cost of the three-phase high-voltage and low-voltage inverter circuit to be high due to the need to use two high-voltage-resistant high-voltage inverter modules.

[0004] The above content is only used to assist in understanding the technical solution of this application and does not constitute an admission that the above content is prior art. Utility Model Content

[0005] The main purpose of this application is to provide a three-phase high-voltage and low-voltage inverter circuit, an inverter and an air conditioner, aiming to solve the technical problem of high cost of the three-phase high-voltage and low-voltage inverter circuit.

[0006] To achieve the above objectives, the present application provides a three-phase high-voltage and low-voltage inverter circuit, the three-phase high-voltage and low-voltage inverter circuit comprising:

[0007] A low-voltage pre-charging unit, wherein an input end of the low-voltage pre-charging unit is connected to the neutral line;

[0008] a high-voltage pre-charging unit, wherein an input end of the high-voltage pre-charging unit is connected to the live wire;

[0009] A low-voltage inverter unit, wherein the input end of the low-voltage inverter unit is connected to the output end of the low-voltage pre-charging unit, and the output end of the low-voltage inverter unit is connected to an external low-voltage motor;

[0010] A rectifier unit, the input end of the rectifier unit is connected to the output end of the high-voltage pre-charging unit; a high-voltage inverter unit, the input end of the high-voltage inverter unit is connected to the output end of the rectifier unit, and the output end of the high-voltage inverter unit is connected to an external high-voltage motor, wherein the high-voltage inverter unit and the low-voltage inverter unit share a common ground.

[0011] In one embodiment, the low voltage pre-charging unit includes:

[0012] a first thermistor, wherein a first end of the first thermistor is connected to the neutral line;

[0013] a first relay, wherein a first end of the first relay is connected to a second end of the first thermistor, and a second end of the first relay is connected to an input end of the low-voltage inverter unit;

[0014] A second relay, wherein a first end of the second relay is connected to the neutral line, and a second end of the second relay is connected to the input end of the low-voltage inverter unit.

[0015] In one embodiment, the low voltage inverter unit includes:

[0016] a low-voltage charging capacitor, wherein a first end of the low-voltage charging capacitor is connected to the second end of the first relay and the second end of the second relay in the low-voltage pre-charging unit, and a second end of the low-voltage charging capacitor is grounded, wherein the second end of the low-voltage charging capacitor is connected to the ground end of the rectifier unit and the ground end of the high-voltage inverter unit;

[0017] a first low-voltage inverter bridge arm, wherein a first end of the first low-voltage inverter bridge arm is connected to a first end of the low-voltage charging capacitor, a second end of the first low-voltage inverter bridge arm is grounded, and a midpoint of the first low-voltage inverter bridge arm is connected to the low-voltage motor;

[0018] a second low-voltage inverter bridge arm, wherein a first end of the second low-voltage inverter bridge arm is connected to the first end of the low-voltage charging capacitor, a second end of the second low-voltage inverter bridge arm is grounded, and a midpoint of the second low-voltage inverter bridge arm is connected to the low-voltage motor;

[0019] A third low-voltage inverter bridge arm, wherein the first end of the third low-voltage inverter bridge arm is connected to the first end of the low-voltage charging capacitor, the second end of the third low-voltage inverter bridge arm is grounded, and the midpoint of the third low-voltage inverter bridge arm is connected to the low-voltage motor, wherein the first low-voltage inverter bridge arm, the second low-voltage inverter bridge arm and the third low-voltage inverter bridge arm are composed of two low-voltage switching tubes connected in series.

[0020] In one embodiment, the live wire includes a first-phase live wire and a second-phase live wire, and the high-voltage pre-charging unit includes:

[0021] a second thermistor, wherein a first end of the second thermistor is connected to the first phase live wire, and a second end of the second thermistor is connected to the input end of the rectifier unit;

[0022] a third relay, wherein a first end of the third relay is connected to the first phase live wire, and a second end of the third relay is connected to the second end of the second thermistor;

[0023] a third thermistor, wherein a first end of the third thermistor is connected to the second-phase live wire, and a second end of the third thermistor is connected to the input end of the rectifier unit;

[0024] A fourth relay, wherein a first end of the fourth relay is connected to the second-phase live wire, and a second end of the fourth relay is connected to the second end of the third thermistor.

[0025] In one embodiment, the live wire includes a third-phase live wire, and the rectifier unit includes:

[0026] a first rectifier bridge arm, wherein the second end of the first rectifier bridge arm is grounded, the midpoint of the first rectifier bridge arm is connected to the third-phase live wire, and the second end of the first rectifier bridge arm is connected to the second end of the low-voltage charging capacitor in the low-voltage inverter unit;

[0027] a second rectifier bridge arm, wherein a first end of the second rectifier bridge arm is connected to a first end of the first rectifier bridge arm, a second end of the second rectifier bridge arm is grounded, and a midpoint of the second rectifier bridge arm is connected to a second end of a second thermistor in the high-voltage pre-charging unit;

[0028] A third rectifier bridge arm, wherein the first end of the third rectifier bridge arm is connected to the first end of the first rectifier bridge arm, the second end of the third rectifier bridge arm is grounded, and the midpoint of the third rectifier bridge arm is connected to the second end of the third thermistor in the high-voltage pre-charging unit, wherein the first rectifier bridge arm, the second rectifier bridge arm and the third rectifier bridge arm are composed of two diodes connected in series.

[0029] In one embodiment, the high-voltage inverter unit includes:

[0030] a first high-voltage charging capacitor, wherein a first end of the first high-voltage charging capacitor is connected to a first end of a first rectifier bridge arm in the rectifier unit;

[0031] a second high-voltage charging capacitor, wherein a first end of the second high-voltage charging capacitor is connected to a second end of the first high-voltage charging capacitor, and a second end of the second high-voltage charging capacitor is grounded;

[0032] a first high-voltage inverter bridge arm, wherein a first end of the first high-voltage inverter bridge arm is connected to a first end of the first high-voltage charging capacitor, a second end of the first high-voltage inverter bridge arm is grounded, and a midpoint of the first high-voltage inverter bridge arm is connected to the high-voltage motor;

[0033] a second high-voltage inverter bridge arm, wherein a first end of the second high-voltage inverter bridge arm is connected to the first end of the first high-voltage charging capacitor, a second end of the second high-voltage inverter bridge arm is grounded, and a midpoint of the second high-voltage inverter bridge arm is connected to the high-voltage motor;

[0034] A third high-voltage inverter bridge arm, wherein the first end of the third high-voltage inverter bridge arm is connected to the first end of the first high-voltage charging capacitor, the second end of the third high-voltage inverter bridge arm is grounded, and the midpoint of the third high-voltage inverter bridge arm is connected to the high-voltage motor, wherein the first high-voltage inverter bridge arm, the second high-voltage inverter bridge arm and the third high-voltage inverter bridge arm are composed of two high-voltage switching tubes connected in series.

[0035] In one embodiment, the three-phase high-voltage and low-voltage inverter circuit further includes:

[0036] a step-down circuit, wherein an input end of the step-down circuit is connected to a first end of the first high-voltage charging capacitor, and a first output end of the step-down circuit is connected to a power supply end of a first relay in the low-voltage pre-charging unit, a power supply end of a second relay in the low-voltage pre-charging unit, a power supply end of a third relay in the high-voltage pre-charging unit, and a power supply end of a fourth relay in the high-voltage pre-charging unit;

[0037] A control chip, wherein the power supply end of the control chip is connected to the second output end of the step-down circuit, the first control end of the control chip is connected to the control end of the first relay in the low-voltage pre-charging unit, the control end of the second relay in the low-voltage pre-charging unit, the control end of the third relay in the high-voltage pre-charging unit, and the control end of the fourth relay in the high-voltage pre-charging unit, and the second control end of the control chip is connected to the control end of the low-voltage switching tube in the low-voltage inverter unit and the control end of the high-voltage switching tube in the high-voltage inverter unit.

[0038] In one embodiment, the three-phase high-voltage and low-voltage inverter circuit further includes:

[0039] A phase sequence detection circuit, wherein the input end of the phase sequence detection circuit is connected to the neutral line and the live line, the output end of the phase sequence detection circuit is connected to the low-voltage pre-charging unit and the high-voltage pre-charging unit, and the detection end of the phase sequence detection circuit is connected to the control chip in the three-phase high-voltage and low-voltage inverter circuit.

[0040] In addition, to achieve the above-mentioned purpose, an inverter is also provided, which includes the above-mentioned three-phase high-voltage and low-voltage inverter circuit.

[0041] In addition, to achieve the above purpose, an air conditioner is also provided, which includes the above inverter, a low-voltage motor and a high-voltage motor, and the inverter is connected to the low-voltage motor, the high-voltage motor and the power grid.

[0042] The embodiment of the present application provides a three-phase high-voltage and low-voltage inverter circuit, including a low-voltage pre-charging unit, the input end of the low-voltage pre-charging unit is connected to the neutral line; a high-voltage pre-charging unit, the input end of the high-voltage pre-charging unit is connected to the live line; a low-voltage inverter unit, the input end of the low-voltage inverter unit is connected to the output end of the low-voltage pre-charging unit, and the output end of the low-voltage inverter unit is connected to an external low-voltage motor; a rectifier unit, the input end of the rectifier unit is connected to the output end of the high-voltage pre-charging unit; a high-voltage inverter unit, the input end of the high-voltage inverter unit is connected to the output end of the rectifier unit, and the output end of the high-voltage inverter unit is connected to an external high-voltage motor, wherein the high-voltage inverter unit and the low-voltage inverter unit share a common ground. This three-phase high-voltage and low-voltage inverter circuit is connected to the neutral line through the input end of the low-voltage pre-charging unit, and then to the live line through the low-voltage inverter unit. The live wire connected to the rectifier unit forms a voltage to supply power to the external low-voltage motor. At the same time, the input end of the high-voltage pre-charging unit is connected to the live wire, and then the external high-voltage motor is supplied with power through the rectifier unit and the high-voltage inverter unit. Among them, the high-voltage inverter unit and the low-voltage inverter unit share a common ground to achieve the effect of supplying power to the low-voltage motor, thereby avoiding the need to use two high-voltage-resistant high-voltage inverter modules to drive the high-voltage motor and the low-voltage motor respectively. This three-phase high-voltage low-voltage inverter circuit uses the input end of the low-voltage pre-charging unit to connect to the neutral wire, and then supplies power to the external low-voltage motor through the low-voltage inverter unit to replace the function that originally required the use of a high-voltage inverter module. It can reduce the use of high-voltage inverter modules in the three-phase high-voltage low-voltage inverter circuit, thereby reducing the cost of the three-phase high-voltage low-voltage inverter circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the framework of the first embodiment of the three-phase high-voltage and low-voltage inverter circuit of the present application;

[0044] Figure 2 This is a connection diagram of a low-voltage pre-charging unit in the three-phase high-voltage and low-voltage inverter circuit of the present application;

[0045] Figure 3 This is a connection diagram of the low-voltage inverter unit in the three-phase high-voltage and low-voltage inverter circuit of the present application;

[0046] Figure 4 This is a connection diagram of a high-voltage pre-charging unit in the three-phase high-voltage and low-voltage inverter circuit of the present application;

[0047] Figure 5 This is a connection diagram of a rectifier unit in the three-phase high-voltage and low-voltage inverter circuit of the present application;

[0048] Figure 6 This is a connection diagram of the high-voltage inverter unit in the three-phase high-voltage and low-voltage inverter circuit of the present application;

[0049] Figure 7This is a connection diagram of the first embodiment of the three-phase high-voltage and low-voltage inverter circuit of the present application;

[0050] Figure 8 This is a connection diagram of the second embodiment of the three-phase high-voltage and low-voltage inverter circuit of the present application;

[0051] Figure 9 This is a connection diagram of a third embodiment of the three-phase high-voltage and low-voltage inverter circuit of the present application;

[0052] Figure 10 A control flow diagram of the three-phase high-voltage and low-voltage inverter circuit of the present application;

[0053] Figure 11 This is another control flow diagram of the three-phase high-voltage and low-voltage inverter circuit of the present application.

[0054] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings.

[0055] Description of Figure Numbers:

[0056] 100, three-phase high-voltage and low-voltage inverter circuit; L, live wire; N, neutral wire; 10, low-voltage pre-charging unit; 20, low-voltage inverter unit; 30, high-voltage pre-charging unit; 40, rectifier unit; 50, high-voltage inverter unit; 200 (M1), low-voltage motor; 300 (M2), high-voltage motor; R1, first thermistor; RY1, first relay; RY2, second relay; C1, low-voltage charging capacitor; 21, first low-voltage inverter bridge arm; 22, second low-voltage inverter bridge arm; 23, third low-voltage inverter bridge arm; Q1-Q6, first low-voltage switch tube - sixth low-voltage switch tube; L2, second phase live wire; L3, third phase live wire; L1, first phase live wire; R2, second thermistor; R3, third thermistor; RY3, third relay; RY4, fourth relay; 41, first rectifier bridge arm; 42, second rectifier bridge arm; 43, first rectifier bridge arm; D1-D6, first diode Tube - sixth diode; C2, first high-voltage charging capacitor; C3, second high-voltage charging capacitor; 51, first high-voltage inverter bridge arm; 52, second high-voltage inverter bridge arm; 53, third high-voltage inverter bridge arm; Q7-Q12, seventh high-voltage switch tube - twelfth high-voltage switch tube; 60, step-down circuit; 70, control chip; 80, phase sequence detection circuit; 400, power grid; RY11, power supply terminal of the first relay; RY21, power supply terminal of the second relay; RY31, power supply terminal of the third relay; RY41, power supply terminal of the fourth relay; RY12, control terminal of the first relay; RY22, control terminal of the second relay; RY32, control terminal of the third relay; RY42, control terminal of the fourth relay; G1-G6, control terminal of the first low-voltage switch tube - control terminal of the sixth low-voltage switch tube; G7-G12, control terminal of the seventh high-voltage switch tube - control terminal of the twelfth high-voltage switch tube. DETAILED DESCRIPTION

[0057] 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.

[0058] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0059] The three-phase high-voltage and low-voltage inverter circuit is a circuit that requires an inverter output to drive a high-voltage motor (taking a compressor as an example) and a low-voltage motor (taking a fan as an example). There are two generally used solutions. One is that both the compressor and the fan draw power from the three-phase rectified bus (537V), and a high-voltage module (1200V) is required. That is, the switching tubes in the high-voltage inverter module must have high-voltage resistance. The compressor drive and the fan drive can be controlled by the same MCU. That is, at this time, both the high-voltage motor and the low-voltage motor use high-voltage-resistant switching tubes to form a high-voltage module, which makes the entire three-phase high-voltage and low-voltage inverter circuit cost higher. Another solution is for the compressor to draw power from the three-phase rectifier bus (about 537V), which requires a high-voltage module (1200V); the fan draws power from one phase of the rectification (about 310V) and uses a low-voltage module (650V); the compressor drive and fan drive are controlled by different MCUs, and the fan and compressor control circuits are not grounded, with basic insulation requirements. However, this solution requires single-phase rectification when using a low-voltage module, which makes the circuit complex and not grounded with the high-voltage system, making PCB (Printed Circuit Board) layout difficult; if this phase is missing, the low-voltage system will lose power and cannot work.

[0060] Therefore, based on the shortcomings of the above-mentioned three-phase high-voltage and low-voltage inverter circuit safety upgrade method, the three-phase high-voltage and low-voltage inverter circuit of the present application is proposed: the input end of the low-voltage pre-charging unit is connected to the neutral line, and then the external low-voltage motor is powered by the low-voltage inverter unit. At the same time, the input end of the high-voltage pre-charging unit is connected to the live wire, and then the external high-voltage motor is powered by the rectifier unit and the high-voltage inverter unit. The high-voltage inverter unit and the low-voltage inverter unit are grounded to achieve the effect of powering the low-voltage motor, thereby avoiding the need to use two high-voltage-resistant high-voltage inverter modules to drive the high-voltage motor and the low-voltage motor respectively. This three-phase high-voltage and low-voltage inverter circuit uses the input end of the low-voltage pre-charging unit to connect to the neutral line, and then the low-voltage inverter unit is used to power the external low-voltage motor to replace the function that originally required the use of a high-voltage inverter module. It can reduce the use of high-voltage inverter modules in the three-phase high-voltage and low-voltage inverter circuit, thereby reducing the cost of the three-phase high-voltage and low-voltage inverter circuit.

[0061] Based on this, the embodiment of the present application provides a three-phase high-voltage and low-voltage inverter circuit, referring to Figure 1 , Figure 1 This is a schematic diagram of the framework of the first embodiment of the three-phase high-voltage and low-voltage inverter circuit of the present application.

[0062] Reference Figure 1 The present application provides a three-phase high-voltage and low-voltage inverter circuit 100, which includes:

[0063] A low-voltage pre-charging unit 10, wherein the input end of the low-voltage pre-charging unit 10 is connected to the neutral line N;

[0064] A high-voltage pre-charging unit 30 , wherein an input end of the high-voltage pre-charging unit 30 is connected to the live wire L;

[0065] A low-voltage inverter unit 20 , wherein the input end of the low-voltage inverter unit 20 is connected to the output end of the low-voltage pre-charging unit 10 , and the output end of the low-voltage inverter unit 20 is connected to an external low-voltage motor 200 ;

[0066] The rectifier unit 40 has an input end connected to the output end of the high-voltage pre-charging unit 30;

[0067] The high-voltage inverter unit 50 has its input end connected to the output end of the rectifier unit 40 , and its output end connected to the external high-voltage motor 300 , wherein the high-voltage inverter unit 50 and the low-voltage inverter unit 20 share a common ground.

[0068] In this embodiment, based on the defects of the existing three-phase high-voltage and low-voltage inverter circuit, the three-phase high-voltage and low-voltage inverter circuit of this embodiment is proposed. On the one hand, the high-voltage pre-charging unit 30 is connected to the live wire L, and then the live wire voltage is used to supply the rectifier unit 40, and then the external high-voltage motor 300 is powered based on the high-voltage inverter unit 50 to achieve normal operation of the high-voltage motor 300; on the other hand, the low-voltage pre-charging unit 10 is connected to the neutral wire N. Because the high-voltage inverter unit 50 and the low-voltage inverter unit 20 share a common ground, rectification can be performed between the neutral wire N and any live wire L to achieve normal operation of the low-voltage motor 200. Because the neutral wire is used to power the low-voltage motor 200 at this time, the voltage resistance requirements of some power devices in the three-phase high-voltage and low-voltage inverter circuit can be reduced (specifically, the switch tube in the low-voltage inverter unit 20 can use a switch tube with general voltage resistance), thereby reducing the wiring complexity to save PCB space and electrical control costs. It is worth noting that because the two high and low voltage control power supply methods share a common ground and the two can be controlled collaboratively, it is convenient for the MCU (Microcontroller Unit) to control the drive signal. At the same time, due to the addition of the rectifier unit 40, the entire high-voltage inverter unit 50 can use any two-phase live wire voltage to achieve power supply. Therefore, if any phase of the live wire is missing, the entire high-voltage motor 300 can also operate normally. Therefore, the entire three-phase high-voltage and low-voltage inverter circuit can reduce the cost of the three-phase high-voltage and low-voltage inverter circuit while ensuring normal power supply.

[0069] In this embodiment, a three-phase high-voltage and low-voltage inverter circuit is provided, including a low-voltage pre-charging unit, wherein the input end of the low-voltage pre-charging unit is connected to the neutral line; a high-voltage pre-charging unit, wherein the input end of the high-voltage pre-charging unit is connected to the live line; a low-voltage inverter unit, wherein the input end of the low-voltage inverter unit is connected to the output end of the low-voltage pre-charging unit, and the output end of the low-voltage inverter unit is connected to an external low-voltage motor; a rectifier unit, wherein the input end of the rectifier unit is connected to the output end of the high-voltage pre-charging unit; a high-voltage inverter unit, wherein the input end of the high-voltage inverter unit is connected to the output end of the rectifier unit, and the output end of the high-voltage inverter unit is connected to an external high-voltage motor, wherein the high-voltage inverter unit and the low-voltage inverter unit share a common ground. This three-phase high-voltage and low-voltage inverter circuit is connected to the neutral line through the input end of the low-voltage pre-charging unit, and then to the live line through the low-voltage inverter unit. The live wire connected to the rectifier unit forms a voltage to supply power to the external low-voltage motor. At the same time, the input end of the high-voltage pre-charging unit is connected to the live wire, and then the external high-voltage motor is supplied with power through the rectifier unit and the high-voltage inverter unit. Among them, the high-voltage inverter unit and the low-voltage inverter unit share a common ground to achieve the effect of supplying power to the low-voltage motor, thereby avoiding the need to use two high-voltage-resistant high-voltage inverter modules to drive the high-voltage motor and the low-voltage motor respectively. This three-phase high-voltage low-voltage inverter circuit uses the input end of the low-voltage pre-charging unit to connect to the neutral wire, and then supplies power to the external low-voltage motor through the low-voltage inverter unit to replace the function that originally required the use of a high-voltage inverter module. It can reduce the use of high-voltage inverter modules in the three-phase high-voltage low-voltage inverter circuit, thereby reducing the cost of the three-phase high-voltage low-voltage inverter circuit.

[0070] Further, based on the first embodiment of the present application, a second embodiment of the three-phase high-voltage and low-voltage inverter circuit of the present application is proposed, referring to Figure 2 , Figure 2 This is a connection diagram of a low-voltage pre-charging unit in the three-phase high-voltage and low-voltage inverter circuit of the present application. The low-voltage pre-charging unit 10 includes:

[0071] a first thermistor R1, wherein a first end of the first thermistor R1 is connected to a neutral line N;

[0072] a first relay RY1 , wherein a first end of the first relay RY1 is connected to a second end of the first thermistor R1 , and a second end of the first relay RY1 is connected to an input end of the low-voltage inverter unit 20 ;

[0073] The second relay RY2 has a first end connected to the neutral line N, and a second end connected to the input end of the low-voltage inverter unit 20 .

[0074] Exemplarily, the low-voltage pre-charging unit 10 refers to a circuit for pre-charging the low-voltage charging capacitor C1 in the low-voltage inverter unit 20, that is, it is connected through the first relay RY1, and then the low-voltage charging capacitor C1 is charged through the first thermistor R1 at this time, and after the pre-charging of the low-voltage charging capacitor C1 is completed, the first relay RY1 is disconnected and the second relay RY2 is closed, so that the low-voltage charging capacitor C1 supplies power to the low-voltage motor 200 connected to the low-voltage inverter unit 20 (the commonly used pre-charging method is to use a thermistor for pre-charging and short-circuit the thermistor after the pre-charging is completed). At this time, because the first end of the first thermistor R1 is connected to the neutral line N, that is, the voltage on the neutral line N is used for pre-charging, the phenomenon that the switching tube in the low-voltage pre-charging unit 20 needs to use a high-voltage device can be avoided, thereby greatly reducing the cost of the entire three-phase high-voltage and low-voltage inverter circuit. It is worth noting that the low-voltage pre-charging unit 10 can also be composed of other devices, which are not limited here.

[0075] In one embodiment, referring to Figure 3 , Figure 3 This is a connection diagram of a low-voltage inverter unit in the three-phase high-voltage low-voltage inverter circuit of the present application. The low-voltage inverter unit 20 includes:

[0076] a low-voltage charging capacitor C1, wherein a first end of the low-voltage charging capacitor C1 is connected to a second end of the first relay RY1 and a second end of the second relay RY2 in the low-voltage pre-charging unit 10, and a second end of the low-voltage charging capacitor C1 is grounded, wherein the second end of the low-voltage charging capacitor C1 is connected to a ground end of the rectifier unit 40 and a ground end of the high-voltage inverter unit 50;

[0077] A first low-voltage inverter bridge arm 21, wherein a first end of the first low-voltage inverter bridge arm 21 is connected to a first end of the low-voltage charging capacitor C1, a second end of the first low-voltage inverter bridge arm 21 is grounded, and a midpoint of the first low-voltage inverter bridge arm 21 is connected to the low-voltage motor 200;

[0078] A second low-voltage inverter bridge arm 22, wherein a first end of the second low-voltage inverter bridge arm 22 is connected to a first end of the low-voltage charging capacitor C1, a second end of the second low-voltage inverter bridge arm 22 is grounded, and a midpoint of the second low-voltage inverter bridge arm 22 is connected to the low-voltage motor 200;

[0079] The third low-voltage inverter bridge arm 23, the first end of the third low-voltage inverter bridge arm 23 is connected to the first end of the low-voltage charging capacitor C1, the second end of the third low-voltage inverter bridge arm 23 is grounded, and the midpoint of the bridge arm of the third low-voltage inverter bridge arm 23 is connected to the low-voltage motor 200, wherein the first low-voltage inverter bridge arm 21, the second low-voltage inverter bridge arm 22 and the third low-voltage inverter bridge arm 23 are composed of two low-voltage switching tubes connected in series.

[0080] In this embodiment, the low-voltage inverter unit 20 includes a low-voltage charging capacitor C1, and a first low-voltage inverter bridge arm 21, a second low-voltage inverter bridge arm 22 and a third low-voltage inverter bridge arm 23 composed of two low-voltage switching tubes connected in series. The low-voltage charging capacitor C1 is used to store electricity, wherein the second end of the low-voltage charging capacitor C1 is connected to the ground end of the rectifier unit 40 and the ground end of the high-voltage inverter unit 50, which is equivalent to forming a rectification circuit with the neutral line connected to the low-voltage pre-charging unit 10 and the live line connected to the rectifier unit 40 when the low-voltage charging capacitor C1 is charged, thereby charging the low-voltage charging capacitor C1. The first low-voltage inverter bridge arm 21, the second low-voltage inverter bridge arm 22 and the third low-voltage inverter bridge arm 23 are used to output three-phase voltage to control the low-voltage motor M1 in the low-voltage motor 200 (i.e., output three-phase voltages U1, V1, W1). Because the low-voltage pre-charging unit 10 uses the neutral line for power supply, the withstand voltage requirement for the low-voltage switch tube is small at this time, so the cost of the three-phase high-voltage and low-voltage inverter circuit can be reduced. Figure 3 , Figure 3 The three-phase inverter circuit of the low-voltage inverter unit 20 is a commonly used inverter circuit. The connection relationship of the entire circuit and the model of the low-voltage switching tube used are not limited here. The first end of the low-voltage inverter bridge arm is one end of the two low-voltage switching tubes connected in series, the second end of the low-voltage inverter bridge arm is the other end of the two low-voltage switching tubes connected in series, and the midpoint of the low-voltage inverter bridge arm is on the connection line of the two low-voltage switching tubes in series.

[0081] Furthermore, based on the first embodiment and / or the second embodiment of the present application, a third embodiment of the three-phase high-voltage and low-voltage inverter circuit of the present application is proposed, with reference to Figure 4 , Figure 4 This is a connection diagram of a high-voltage pre-charging unit in the three-phase high-voltage and low-voltage inverter circuit of the present application. The live wire L includes a first-phase live wire L1 and a second-phase live wire L2. The high-voltage pre-charging unit 30 includes:

[0082] a second thermistor R2, wherein a first end of the second thermistor R2 is connected to the first phase live wire L1, and a second end of the second thermistor R2 is connected to an input end of the rectifier unit 40;

[0083] a third relay RY3 , wherein a first end of the third relay RY3 is connected to the first phase live wire L1 , and a second end of the third relay RY3 is connected to the second end of the second thermistor R2 ;

[0084] a third thermistor R3 , wherein a first end of the third thermistor R3 is connected to the second phase live wire L2 , and a second end of the third thermistor R3 is connected to the input end of the rectifier unit 40 ;

[0085] The fourth relay RY4 has a first end connected to the second-phase live wire L2 , and a second end connected to the second end of the third thermistor R3 .

[0086] Exemplarily, the high-voltage pre-charging unit 30 refers to a circuit for pre-charging the first high-voltage charging capacitor C2 and the second high-voltage charging capacitor C3 in the high-voltage inverter unit 50, that is, the first phase live wire L1 is connected to the third thermistor R2 and the second phase live wire L2 is connected to the first high-voltage charging capacitor C2 and the second high-voltage charging capacitor C3 are charged, and after the pre-charging of the first high-voltage charging capacitor C2 and the second high-voltage charging capacitor C3 is completed, the third relay RY3 and the fourth relay RY4 are closed, so that the first high-voltage charging capacitor C2 and the second high-voltage charging capacitor C3 are powered by the high-voltage motor 300 connected to the high-voltage inverter unit 50. At this time, because the first end of the second thermistor R2 is connected to the first phase live wire L1 and the first end of the third thermistor R3 is connected to the second phase live wire L2, that is, the voltage on the two live wires is used for pre-charging, the phenomenon of the entire circuit not being able to work normally due to a single-phase live wire failure can be avoided, thereby ensuring the normal operation of the three-phase high-voltage and low-voltage inverter circuit. It is worth noting that the high-voltage pre-charging unit 30 can also be composed of other components, which are not limited here.

[0087] In one embodiment, referring to Figure 5 , Figure 5 This is a connection diagram of a rectifier unit in the three-phase high-voltage and low-voltage inverter circuit of the present application. The live wire L includes the third-phase live wire L3. The rectifier unit 40 includes:

[0088] A first rectifier bridge arm 41, a second end of the first rectifier bridge arm 41 is grounded, a midpoint of the first rectifier bridge arm 41 is connected to the third phase live wire L3, wherein the second end of the first rectifier bridge arm 41 is connected to the second end of the low-voltage charging capacitor C1 in the low-voltage inverter unit 20;

[0089] A second rectifier bridge arm 42, wherein a first end of the second rectifier bridge arm 42 is connected to a first end of the first rectifier bridge arm 41, a second end of the second rectifier bridge arm 42 is grounded, and a midpoint of the second rectifier bridge arm 42 is connected to a second end of a second thermistor R2 in the high-voltage pre-charging unit 30;

[0090] The third rectifier bridge arm 43, the first end of the third rectifier bridge arm 43 is connected to the first end of the first rectifier bridge arm 41, the second end of the third rectifier bridge arm 43 is grounded, and the midpoint of the third rectifier bridge arm 43 is connected to the second end of the third thermistor R3 in the high-voltage pre-charging unit 30, wherein the first rectifier bridge arm 41, the second rectifier bridge arm 42 and the third rectifier bridge arm 43 are composed of two diodes connected in series.

[0091] For example, because the high-voltage inverter unit 50 uses the voltage on the two live wires for pre-charging, the rectifier unit 40 is required for rectification. It is worth noting that the second end of the first rectifier bridge arm 41 is connected to the second end of the low-voltage charging capacitor C1 in the low-voltage inverter unit 20. When the low-voltage charging capacitor C1 is charged, the neutral line connected to the low-voltage pre-charging unit 10 and the live line connected to the rectifier unit 40 form a rectifier circuit, thereby charging the low-voltage charging capacitor C1. The rectifier unit 40 includes a first rectifier bridge arm 41, a second rectifier bridge arm 42, and a third rectifier bridge arm 43 composed of two diodes connected in series to rectify the pre-charged voltage and the phase that is not pre-charged. Because of the existence of the rectifier unit 40, only the voltage on any two live wires can be used for pre-charging, which can greatly reduce the difficulty of powering the entire high-voltage motor 300. Figure 5 The three-phase rectifier circuit of the rectifier unit 40 is a commonly used rectifier circuit. The connection relationship of the entire circuit and the type of diode used are not limited here. The first end of the rectifier bridge arm is one end of the two diodes connected in series, the second end of the rectifier bridge arm is the other end of the two diodes connected in series, and the midpoint of the rectifier bridge arm is on the line connecting the two diodes in series.

[0092] In one embodiment, referring to Figure 6 , Figure 6 This is a connection diagram of a high-voltage inverter unit in the three-phase high-voltage and low-voltage inverter circuit of the present application. The high-voltage inverter unit 50 includes:

[0093] A first high-voltage charging capacitor C2, wherein a first end of the first high-voltage charging capacitor C2 is connected to a first end of a first rectifier bridge arm 41 in the rectifier unit 40;

[0094] a second high-voltage charging capacitor C3, wherein a first end of the second high-voltage charging capacitor C3 is connected to a second end of the first high-voltage charging capacitor C2, and a second end of the second high-voltage charging capacitor C3 is grounded;

[0095] A first high-voltage inverter bridge arm 51, wherein a first end of the first high-voltage inverter bridge arm 51 is connected to a first end of the first high-voltage charging capacitor C2, a second end of the first high-voltage inverter bridge arm 51 is grounded, and a midpoint of the first high-voltage inverter bridge arm 51 is connected to the high-voltage motor 300;

[0096] A second high-voltage inverter bridge arm 52, wherein a first end of the second high-voltage inverter bridge arm 52 is connected to a first end of the first high-voltage charging capacitor C2, a second end of the second high-voltage inverter bridge arm 52 is grounded, and a midpoint of the second high-voltage inverter bridge arm 52 is connected to the high-voltage motor 300;

[0097] The third high-voltage inverter bridge arm 53, the first end of the third high-voltage inverter bridge arm 53 is connected to the first end of the first high-voltage charging capacitor C2, the second end of the third high-voltage inverter bridge arm 53 is grounded, and the midpoint of the bridge arm of the third high-voltage inverter bridge arm 53 is connected to the high-voltage motor 300, wherein the first high-voltage inverter bridge arm 51, the second high-voltage inverter bridge arm 52 and the third high-voltage inverter bridge arm 53 are composed of two high-voltage switching tubes connected in series.

[0098] In this embodiment, the high-voltage inverter unit 50 includes a first high-voltage charging capacitor C2 and a second high-voltage charging capacitor C3, and a first high-voltage inverter bridge arm 51, a second high-voltage inverter bridge arm 52 and a third high-voltage inverter bridge arm 53 composed of two high-voltage switching tubes connected in series. The first high-voltage charging capacitor C2 and the second high-voltage charging capacitor C3 are used to store electricity. The first high-voltage inverter bridge arm 51, the second high-voltage inverter bridge arm 52 and the third high-voltage inverter bridge arm 53 are used to output three-phase voltage to control the high-voltage motor M2 in the high-voltage motor 300 (that is, output three-phase voltage U2, V2, W2). Because the high-voltage pre-charging unit 30 uses the voltage on the two live wires for pre-charging, the live wire requirements of the three-phase high-voltage and low-voltage inverter circuit can be reduced. Figure 7 This is a connection diagram of the first embodiment of the three-phase high-voltage and low-voltage inverter circuit of this application. Figure 7 The three-phase inverter circuit of the high-voltage inverter unit 50 is a commonly used inverter circuit. The connection relationship of the entire circuit and the model of the high-voltage switching tube used are not limited here. The first end of the high-voltage inverter bridge arm is one end of the two high-voltage switching tubes connected in series, the second end of the high-voltage inverter bridge arm is the other end of the two high-voltage switching tubes connected in series, and the midpoint of the high-voltage inverter bridge arm is on the connection line of the two high-voltage switching tubes in series.

[0099] Furthermore, based on the first embodiment, the second embodiment and / or the third embodiment of the present application, a fourth embodiment of the three-phase high-voltage and low-voltage inverter circuit of the present application is proposed, with reference to Figure 8 , Figure 8 This is a connection diagram of a second embodiment of the three-phase high-voltage and low-voltage inverter circuit of the present application. The three-phase high-voltage and low-voltage inverter circuit 100 further includes:

[0100] a step-down circuit 60, wherein an input end of the step-down circuit 60 is connected to a first end of the first high-voltage charging capacitor C2, and a first output end of the step-down circuit 60 is connected to a power supply end RY11 of a first relay in the low-voltage pre-charging unit 10, a power supply end RY21 of a second relay in the low-voltage pre-charging unit 10, a power supply end RY31 of a third relay in the high-voltage pre-charging unit 30, and a power supply end RY41 of a fourth relay in the high-voltage pre-charging unit 30;

[0101] The control chip 70 has a power supply end connected to the second output end of the step-down circuit 60, a first control end of the control chip 70 is connected to the control end RY12 of the first relay in the low-voltage pre-charging unit 10, a control end RY22 of the second relay in the low-voltage pre-charging unit 10, a control end RY32 of the third relay in the high-voltage pre-charging unit 30, and a control end RY42 of the fourth relay in the high-voltage pre-charging unit 30, and a second control end of the control chip 70 is connected to the control end of the low-voltage switching tube in the low-voltage inverter unit 20 and the control end of the high-voltage switching tube in the high-voltage inverter unit 50.

[0102] Exemplarily, the three-phase high-voltage and low-voltage inverter circuit 100 also includes a step-down circuit 60 and a control chip 70, wherein the step-down circuit 60 can be a commonly used DC (direct current)-DC (direct current) step-down circuit, and can use a special step-down chip or a resistor divider to perform step-down. The specific step-down circuit composition is not limited here. At this time, the stepped-down voltage will be provided to the power supply terminal RY11 of the first relay, the power supply terminal RY21 of the second relay, the power supply terminal RY31 of the third relay and the power supply terminal RY41 of the fourth relay to ensure the normal power supply of the relay, such as providing 12V voltage to the relay. At the same time, voltage will also be provided to the power supply terminal of the control chip 70 to enable the control chip 70 to work normally, such as providing 12V and 5V voltages to the control chip 70. The control chip 70 can be used to control the shutdown of the relay or the shutdown of the low-voltage switch tube in the low-voltage inverter unit 20 and the high-voltage switch tube in the high-voltage inverter unit 50 to realize the pre-charging control of the relay and the drive control of the low-voltage switch tube and the high-voltage switch tube. Among them, the control chip 70 can be an MCU, a single-chip microcomputer, etc., which is not limited here.

[0103] In one embodiment, referring to Figure 9 , Figure 9 This is a connection diagram of a third embodiment of the three-phase high-voltage and low-voltage inverter circuit of the present application. The three-phase high-voltage and low-voltage inverter circuit 100 further includes:

[0104] The phase sequence detection circuit 80 has an input end connected to the neutral line N and the live line L, an output end connected to the low-voltage pre-charging unit 10 and the high-voltage pre-charging unit 30, and a detection end connected to the control chip 70 in the three-phase high-voltage and low-voltage inverter circuit 100.

[0105] In this embodiment, the three-phase high-voltage and low-voltage inverter circuit 100 also includes a phase sequence detection circuit 80, which can be used to check the phase sequence between the neutral wire and the live wire or the voltage of the live wire. For example, the phase sequence detection circuit 80 includes a voltage comparator, and then compares the live wire voltage with the comparison voltage to determine the voltage through the output of the voltage comparator, or directly uses the relevant resistance acquisition method to collect the voltage. The phase sequence detection circuit 80 can also include three voltage collectors, which are respectively connected to the three live wires and the neutral wire, and then determine whether the timing of the neutral wire is correct through the timing of the voltage. At the same time, the inspection result (live wire voltage or neutral wire timing) is output to the control chip 70 to control the entire circuit through the control chip 70, and its control method can be a common method. Please refer to Figure 10 , Figure 10 This is a control flow diagram of the three-phase high-voltage and low-voltage inverter circuit of this application. If an abnormal voltage (abnormal phase sequence) is detected on the N line during operation, the MCU stops outputting signals G1-G6 and disconnects the RY1 and RY2 relays, waiting for the N line voltage to return to normal. After the voltage returns to normal, RY1 is reclosed to charge the C1 capacitor. After charging is complete, RY2 is closed, and the M1 motor resumes operation. The entire process does not affect the normal operation of the M2 motor. In other words, the advantage of powering the step-down circuit 60 with the first high-voltage charging capacitor C2 at this time is that it is not affected by the N line voltage, ensuring the normal operation of the high-voltage motor 300.

[0106] In one embodiment, referring to Figure 11 , Figure 11This is another control flow diagram of the three-phase high-voltage and low-voltage inverter circuit of the present application. After the whole machine is powered on, L1, L2, and L3 charge the high-voltage module capacitors C2 and C3 through R2 and R3. The MCU and the relay are powered by C2 after the voltage is stepped down by the step-down circuit. The MCU identifies the input voltage phase sequence and input voltage through the phase sequence detection circuit 80. At this time, the phase sequence detection circuit 80 is for the MCU to determine whether the wiring is normal by respectively detecting the phase voltage and phase difference of L1, L2, and L3. When the phase sequence of the N line is correct, the RY1 relay is closed. At this time, the N line charges the low-voltage module capacitor C1 through R1. After charging is completed, the RY2, RY3, and RY4 relays are closed, that is, the low-voltage load M1 motor and the high-voltage load motor M2 start working; if the phase sequence of the N line is wrong, all relays remain disconnected. At this time, due to the presence of the rectifier unit 40, even if any phase of L1, L2, or L3 is missing, the entire system can still start and operate normally. In the entire three-phase high-voltage and low-voltage inverter circuit 100, the rectifier unit 40 outputs a high bus voltage (about 537V) for use by the high-voltage inverter unit 50 (1200V). U2, V2, and W2 are the inverter outputs of the high-voltage motor, controlling the operation of the M2 motor; the low-voltage charging capacitor C1 outputs a low bus voltage (about 310V) for use by the low-voltage inverter unit 20 (650V). U1, V1, and W1 are the inverter outputs of the low-voltage motor, controlling the operation of the M1 motor. The inverter system of the entire high-voltage motor and the inverter system of the low-voltage motor share a common ground, and there is no basic insulation requirement. The drive signals G1-G12 can be controlled by the same MCU to reduce the use cost of the entire three-phase high-voltage and low-voltage inverter circuit.

[0107] The present application also provides an inverter, which includes the above-mentioned three-phase high-voltage and low-voltage inverter circuit.

[0108] It is worth noting that, according to the inverter of the embodiment of the present invention, the inverter is connected to the neutral line through the input end of the low-voltage pre-charging unit, and then the external low-voltage motor is powered by the low-voltage inverter unit. At the same time, the input end of the high-voltage pre-charging unit is connected to the live wire, and then the external high-voltage motor is powered by the rectifier unit and the high-voltage inverter unit. The high-voltage inverter unit and the low-voltage inverter unit are grounded to achieve the effect of powering the low-voltage motor, thereby avoiding the need to use two high-voltage resistant high-voltage inverter modules to drive the high-voltage motor and the low-voltage motor respectively. This three-phase high-voltage low-voltage inverter circuit replaces the function that originally required the use of a high-voltage inverter module by connecting the input end of the low-voltage pre-charging unit to the neutral line and then powering the external low-voltage motor through the low-voltage inverter unit. It can reduce the use of high-voltage inverter modules in the three-phase high-voltage low-voltage inverter circuit, thereby reducing the cost of the three-phase high-voltage low-voltage inverter circuit.

[0109] The device provided in this application can solve the technical problem of high cost of three-phase high-voltage and low-voltage inverter circuits. Compared with the prior art, the beneficial effects of the device provided in this application are the same as those of the three-phase high-voltage and low-voltage inverter circuit provided in the above embodiment, and will not be repeated here.

[0110] The present application also provides an air conditioner, which includes the above-mentioned inverter, a low-voltage motor M1 and a high-voltage motor M2, wherein the inverter is connected to the low-voltage motor M1, the high-voltage motor M2 and a power grid 400.

[0111] It is worth noting that the inverter can be installed on the air conditioner to drive the low-voltage motor and the high-voltage motor, and driven by the power grid at the same time. A three-phase high-voltage and low-voltage inverter circuit is set inside the inverter, and is connected to the motors that drive the low-voltage motor and the high-voltage motor respectively. Then, the input end of the low-voltage pre-charging unit can be connected to the neutral line, and then the external low-voltage motor is powered by the low-voltage inverter unit. At the same time, the input end of the high-voltage pre-charging unit is connected to the live wire, and then the external high-voltage motor is powered by the rectifier unit and the high-voltage inverter unit. The high-voltage inverter unit and the low-voltage inverter unit are grounded together to achieve the effect of powering the low-voltage motor.

[0112] It is worth noting that the air conditioner may also include other hardware, which will not be described one by one here. The entire inverter can be set on the air conditioner or on other products, which is not limited here.

[0113] The device provided in this application can solve the technical problem of high cost of three-phase high-voltage and low-voltage inverter circuits. Compared with the prior art, the beneficial effects of the air conditioner provided in this application are the same as those of the three-phase high-voltage and low-voltage inverter circuit provided in the above embodiment, and will not be repeated here.

[0114] The above description is only part of the embodiments of the present application and does not limit the patent scope of the present application. All equivalent structural transformations made by using the contents of the present application specification and drawings under the technical 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 three-phase high-voltage and low-voltage inverter circuit, characterized in that: The three-phase high-voltage and low-voltage inverter circuit includes: A low-voltage pre-charging unit, wherein an input end of the low-voltage pre-charging unit is connected to the neutral line; a high-voltage pre-charging unit, wherein an input end of the high-voltage pre-charging unit is connected to the live wire; A low-voltage inverter unit, wherein the input end of the low-voltage inverter unit is connected to the output end of the low-voltage pre-charging unit, and the output end of the low-voltage inverter unit is connected to an external low-voltage motor; a rectifier unit, wherein an input end of the rectifier unit is connected to an output end of the high-voltage pre-charging unit; A high-voltage inverter unit, wherein the input end of the high-voltage inverter unit is connected to the output end of the rectifier unit, and the output end of the high-voltage inverter unit is connected to an external high-voltage motor, wherein the high-voltage inverter unit, the rectifier unit and the low-voltage inverter unit share a common ground.

2. The three-phase high-voltage and low-voltage inverter circuit according to claim 1, characterized in that: The low voltage pre-charging unit comprises: a first thermistor, wherein a first end of the first thermistor is connected to the neutral line; a first relay, wherein a first end of the first relay is connected to a second end of the first thermistor, and a second end of the first relay is connected to an input end of the low-voltage inverter unit; A second relay, wherein a first end of the second relay is connected to the neutral line, and a second end of the second relay is connected to the input end of the low-voltage inverter unit.

3. The three-phase high-voltage and low-voltage inverter circuit according to claim 1, wherein: The low voltage inverter unit includes: a low-voltage charging capacitor, wherein a first end of the low-voltage charging capacitor is connected to the second end of the first relay and the second end of the second relay in the low-voltage pre-charging unit, and a second end of the low-voltage charging capacitor is grounded, wherein the second end of the low-voltage charging capacitor is connected to the ground end of the rectifier unit and the ground end of the high-voltage inverter unit; a first low-voltage inverter bridge arm, wherein a first end of the first low-voltage inverter bridge arm is connected to a first end of the low-voltage charging capacitor, a second end of the first low-voltage inverter bridge arm is grounded, and a midpoint of the first low-voltage inverter bridge arm is connected to the low-voltage motor; a second low-voltage inverter bridge arm, wherein a first end of the second low-voltage inverter bridge arm is connected to the first end of the low-voltage charging capacitor, a second end of the second low-voltage inverter bridge arm is grounded, and a midpoint of the second low-voltage inverter bridge arm is connected to the low-voltage motor; A third low-voltage inverter bridge arm, wherein the first end of the third low-voltage inverter bridge arm is connected to the first end of the low-voltage charging capacitor, the second end of the third low-voltage inverter bridge arm is grounded, and the midpoint of the third low-voltage inverter bridge arm is connected to the low-voltage motor, wherein the first low-voltage inverter bridge arm, the second low-voltage inverter bridge arm and the third low-voltage inverter bridge arm are composed of two low-voltage switching tubes connected in series.

4. The three-phase high-voltage and low-voltage inverter circuit according to claim 1, wherein: The live wire includes a first-phase live wire and a second-phase live wire, and the high-voltage pre-charging unit includes: a second thermistor, wherein a first end of the second thermistor is connected to the first phase live wire, and a second end of the second thermistor is connected to the input end of the rectifier unit; a third relay, wherein a first end of the third relay is connected to the first phase live wire, and a second end of the third relay is connected to the second end of the second thermistor; a third thermistor, wherein a first end of the third thermistor is connected to the second-phase live wire, and a second end of the third thermistor is connected to the input end of the rectifier unit; A fourth relay, wherein a first end of the fourth relay is connected to the second-phase live wire, and a second end of the fourth relay is connected to the second end of the third thermistor.

5. The three-phase high-voltage and low-voltage inverter circuit according to claim 1, wherein: The live wire includes a third-phase live wire, and the rectifier unit includes: a first rectifier bridge arm, wherein the second end of the first rectifier bridge arm is grounded, the midpoint of the first rectifier bridge arm is connected to the third-phase live wire, and the second end of the first rectifier bridge arm is connected to the second end of the low-voltage charging capacitor in the low-voltage inverter unit; a second rectifier bridge arm, wherein a first end of the second rectifier bridge arm is connected to a first end of the first rectifier bridge arm, a second end of the second rectifier bridge arm is grounded, and a midpoint of the second rectifier bridge arm is connected to a second end of a second thermistor in the high-voltage pre-charging unit; A third rectifier bridge arm, wherein the first end of the third rectifier bridge arm is connected to the first end of the first rectifier bridge arm, the second end of the third rectifier bridge arm is grounded, and the midpoint of the third rectifier bridge arm is connected to the second end of the third thermistor in the high-voltage pre-charging unit, wherein the first rectifier bridge arm, the second rectifier bridge arm and the third rectifier bridge arm are composed of two diodes connected in series.

6. The three-phase high-voltage and low-voltage inverter circuit according to claim 1, wherein: The high-voltage inverter unit includes: a first high-voltage charging capacitor, wherein a first end of the first high-voltage charging capacitor is connected to a first end of a first rectifier bridge arm in the rectifier unit; a second high-voltage charging capacitor, wherein a first end of the second high-voltage charging capacitor is connected to a second end of the first high-voltage charging capacitor, and a second end of the second high-voltage charging capacitor is grounded; a first high-voltage inverter bridge arm, wherein a first end of the first high-voltage inverter bridge arm is connected to a first end of the first high-voltage charging capacitor, a second end of the first high-voltage inverter bridge arm is grounded, and a midpoint of the first high-voltage inverter bridge arm is connected to the high-voltage motor; a second high-voltage inverter bridge arm, wherein a first end of the second high-voltage inverter bridge arm is connected to the first end of the first high-voltage charging capacitor, a second end of the second high-voltage inverter bridge arm is grounded, and a midpoint of the second high-voltage inverter bridge arm is connected to the high-voltage motor; A third high-voltage inverter bridge arm, wherein the first end of the third high-voltage inverter bridge arm is connected to the first end of the first high-voltage charging capacitor, the second end of the third high-voltage inverter bridge arm is grounded, and the midpoint of the third high-voltage inverter bridge arm is connected to the high-voltage motor, wherein the first high-voltage inverter bridge arm, the second high-voltage inverter bridge arm and the third high-voltage inverter bridge arm are composed of two high-voltage switching tubes connected in series.

7. The three-phase high-voltage and low-voltage inverter circuit according to claim 6, characterized in that: The three-phase high-voltage and low-voltage inverter circuit further includes: a step-down circuit, wherein an input end of the step-down circuit is connected to a first end of the first high-voltage charging capacitor, and a first output end of the step-down circuit is connected to a power supply end of a first relay in the low-voltage pre-charging unit, a power supply end of a second relay in the low-voltage pre-charging unit, a power supply end of a third relay in the high-voltage pre-charging unit, and a power supply end of a fourth relay in the high-voltage pre-charging unit; A control chip, wherein the power supply end of the control chip is connected to the second output end of the step-down circuit, the first control end of the control chip is connected to the control end of the first relay in the low-voltage pre-charging unit, the control end of the second relay in the low-voltage pre-charging unit, the control end of the third relay in the high-voltage pre-charging unit, and the control end of the fourth relay in the high-voltage pre-charging unit, and the second control end of the control chip is connected to the control end of the low-voltage switching tube in the low-voltage inverter unit and the control end of the high-voltage switching tube in the high-voltage inverter unit.

8. The three-phase high-voltage and low-voltage inverter circuit according to any one of claims 1 to 7, characterized in that: The three-phase high-voltage and low-voltage inverter circuit further includes: A phase sequence detection circuit, wherein the input end of the phase sequence detection circuit is connected to the neutral line and the live line, the output end of the phase sequence detection circuit is connected to the low-voltage pre-charging unit and the high-voltage pre-charging unit, and the detection end of the phase sequence detection circuit is connected to the control chip in the three-phase high-voltage and low-voltage inverter circuit.

9. An inverter, characterized in that: The inverter includes the three-phase high-voltage and low-voltage inverter circuit according to any one of claims 1 to 8.

10. An air conditioner, characterized in that: The air conditioner includes the inverter according to claim 9, a low-voltage motor, and a high-voltage motor, wherein the inverter is connected to the low-voltage motor, the high-voltage motor, and a power grid.

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