CN111864877A - A kind of charging circuit of air conditioner inverter controller without inrush current - Google Patents

Abstract

The invention relates to a charging circuit of an air conditioner variable frequency controller without inrush current, comprising a rectifier bridge; the input end R and the input end S of the rectifier bridge are respectively connected to the live wire L1 and the live wire L2 after passing through the relay Q1 and the relay Q2; The input end T of the rectifier bridge is connected to the live wire L3; the output end P and the output end N of the rectifier bridge are respectively connected to the positive end of the capacitor C1 and the negative end of the capacitor C2; the capacitor C1 and the capacitor C2 are connected in series; the The capacitor C1 is connected in parallel with a resistor R1; the capacitor C2 is connected in parallel with a resistor R2; it also includes an auxiliary switching power supply, whose input end and output end are respectively connected to the live wire L3 and the neutral wire N; the series midpoint of the capacitor C1 and the capacitor C2 passes through in turn Resistor R3 and relay K1 are then connected to neutral N. The invention can realize zero inrush current of the relay, reduce the failure rate of the relay, and reduce the maintenance cost of the controller product.

Description

A kind of charging circuit of air conditioner inverter controller without inrush current

technical field

The invention relates to an air conditioner component, in particular to a charging circuit of an air conditioner frequency conversion controller, in particular to an air conditioner frequency conversion controller charging circuit without impact current.

Background technique

At present, in a commercial (three-phase) air conditioner inverter controller, the main power loop first rectifies the AC power on the grid side into DC power through a rectifier bridge. In order to reduce the voltage ripple of the DC bus after rectification, a high-voltage electrolytic capacitor with a certain value is usually added to the DC bus for filtering and energy storage. With the introduction of high-voltage electrolytic capacitors, when the air-conditioning unit is to be turned on, the electrolytic capacitors of the inverter controller will be charged from zero voltage to a certain voltage value. And because the initial state of electrolytic capacitor charging is regarded as a short-circuit state, the charging circuit is generally connected in series with a resistor to limit the current. 10sec, at this time, it is considered that the DC bus voltage value is basically similar to the peak value of the line voltage sine wave of the power grid, but because of the existence of the current limiting resistor, there is actually a difference between them), and then pull in the bypass relay (with the current limiting resistor). parallel), and finally complete the entire charging process.

However, because there is a voltage difference between the front and rear nodes of the relay, and the resistance at the relay contact is very small, there is still a large inrush current at the moment of its pull-in. Long-term impact will accelerate the aging of the contacts of the relay, shorten its life, and even burn out the relay directly.

Therefore, it needs to be improved to eliminate the impact damage of the bypass relay caused by the inrush current.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a charging circuit of an air conditioner variable frequency controller without inrush current, which can realize zero inrush current of the relay, reduce the failure rate of the relay, and reduce the maintenance cost of the controller product.

The technical scheme of the present invention is:

A charging circuit of an air conditioner variable frequency controller without inrush current, comprising a rectifier bridge; an input end R and an input end S of the rectifier bridge are respectively connected to the live wire L1 and the live wire L2 after passing through the relay Q1 and the relay Q2; The input terminal T is connected to the live wire L3; the output terminal P and the output terminal N of the rectifier bridge are respectively connected to the positive terminal of the capacitor C1 and the negative terminal of the capacitor C2; the capacitor C1 and the capacitor C2 are connected in series; Parallel resistor R1; parallel resistor R2 on the capacitor C2;

It also includes an auxiliary switching power supply, whose input end and output end are respectively connected to the live wire L3 and the neutral wire N;

Further, the rectifier bridge is a three-phase rectifier bridge, each phase is formed by connecting two diodes end to end, and then the cathodes of the three-phase diodes are connected to form the output terminal P of the DC bus, and at the same time, the three-phase diodes are connected. The anodes are connected to form the output terminal N of the DC bus.

Further, the capacitor C1 and the capacitor C2 are both high-voltage electrolytic capacitors and have equal capacitance values.

Further, the resistance values of the resistors R1 and R2 are equal.

Beneficial effects of the present invention:

The invention has reasonable design, simple structure and convenient use, can realize zero inrush current of the relay, reduce the failure rate of the relay, and reduce the maintenance cost of the controller product.

Description of drawings

Figure 1 is a schematic structural diagram of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1.

A charging circuit of an air conditioner variable frequency controller without inrush current includes a rectifier bridge. The rectifier bridge is a three-phase rectifier bridge, including six diodes D2, D3, D4, D5, D6 and D8; every two diodes are connected end to end to form a phase; then the cathodes of the three-phase diodes are connected together , form the output terminal P of the DC bus; at the same time, connect the anodes of the three-phase diodes to form the output terminal N of the DC bus.

The input end R and the input end S of the rectifier bridge are respectively connected to the live wire L1 and the live wire L2 after passing through the relay Q1 and the relay Q2. The input terminal T of the rectifier bridge is connected to the live wire L3. The output terminal P and the output terminal N of the rectifier bridge are respectively connected to the positive terminal of the capacitor C1 and the negative terminal of the capacitor C2. The capacitor C1 and the capacitor C2 are connected in series. The capacitors C1 and C2 are both high-voltage electrolytic capacitors, and the two capacitors are of equal capacitance.

A resistor R1 is connected in parallel with the capacitor C1; and a resistor R2 is connected in parallel with the capacitor C2. The resistors R1 and R2 are voltage equalizing resistors, which play the role of voltage equalizing.

It also includes an auxiliary switching power supply, whose input end and output end are respectively connected to the live wire L3 and the neutral wire N; The resistor R3 is a current limiting resistor.

The working process of the present invention is:

1. Domestic air conditioner inverter controllers with a power level of 8KW or above usually use three-phase four-wire power supply. According to the standard single-phase rated voltage of 220Vac, the line voltage is 380Vac, and the three-phase live wires L1, L2, and L3 are directly rectified by the rectifier bridge. , the peak voltage of the DC bus is up to 540Vpeak, and the withstand voltage of high-voltage electrolytic capacitors is generally 400V or 450V, so the high-voltage electrolytic capacitor at the DC bus needs to use two capacitors in series to improve the withstand voltage level;

2. The DC bus adopts two high-voltage electrolytic capacitors in series. Due to the differences in capacitance, leakage current, and parasitic parameters of each capacitor, the voltages of the two capacitors in series are equal, so it is necessary to connect two capacitors in parallel. Voltage equalizing resistor to achieve voltage equalization;

3. After the combination switch of the air conditioner is powered on, the auxiliary switching power supply of the variable frequency controller is powered first, and the MCU circuit of the controller has started to work; then a command is issued to close the K1 relay, and L3 and N form a current closed loop, using the sine wave During positive and negative half cycles, capacitors C1 and C2 are charged in turn;

4. After the pull-in time of K1 is ten times of R3*C1, the voltages of C1 and C2 have basically been charged to 220V*1.414=310V, then Vc1+Vc2=620V;

5. The MCU chip picks up the K1 relay and starts timing. After 10*R3*C1 time, the pull-in command of Q1 and Q2 is issued; because the peak line voltage between L1, L2, and L3: 1.732*1.414*220=540V, It is less than Vc1+Vc2=620V, so when the relay Q1 and the relay Q2 are pulled in, there is no inrush current in the contacts; then, after extending for another 1sec, the command to disconnect K1 is issued, and the resistor R3 withdraws from the current limiting function, and the entire charging is completed. process to achieve zero-impact charging.

The parts not involved in the present invention are the same as the prior art or can be implemented by using the prior art.

Claims (4)

1. an air-conditioning frequency conversion controller charging circuit without inrush current, comprising a rectifier bridge; it is characterized in that: the input end R and input end S of the rectifier bridge are respectively connected to live wire L1 and live wire L2 after relay Q1 and relay Q2 The input end T of the rectifier bridge is connected to the live wire L3; the output end P and the output end N of the rectifier bridge are respectively connected to the positive end of the capacitor C1 and the negative end of the capacitor C2; the capacitor C1 and the capacitor C2 are connected in series ; The capacitor C1 is connected in parallel with a resistor R1; the capacitor C2 is connected in parallel with a resistor R2; It also includes an auxiliary switching power supply, whose input end and output end are respectively connected to the live wire L3 and the neutral wire N; 2. The air-conditioning inverter controller charging circuit without inrush current according to claim 1, wherein the rectifier bridge is a three-phase rectifier bridge, and each phase is formed by connecting two diodes end to end, and then the three-phase rectifier bridge is formed. The cathodes of the diodes are connected to form the output terminal P of the DC bus, and at the same time, the anodes of the three-phase diodes are connected to form the output N of the DC bus. 3 . The charging circuit for an air conditioner inverter controller without inrush current according to claim 1 , wherein the capacitor C1 and the capacitor C2 are both high-voltage electrolytic capacitors and have equal capacitance values. 4 . 4 . The charging circuit of an air conditioner inverter controller without inrush current according to claim 1 , wherein the resistance values of the resistors R1 and R2 are equal. 5 .

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