Soft start charging circuit and control method thereof

Abstract

The invention provides a soft start charging circuit, which comprises a controller, a first relay, a second relay and a charging resistor, wherein both the first relay and the second relay are electrically connected with the controller; the first relay comprises two contacts namely the first contact and the second contact; the contact of the second relay is connected in series with the charging resistor and then connected in parallel with the first contact; and the contact of the second relay and the second contact are respectively connected in series with different input ends of a three-phase alternating current power supply. The invention further relates to a control method of the soft start charging circuit. According to the soft start charging circuit and the control method thereof, the two relays are respectively placed between any two phases of the input side of the three-phase alternating current power supply, so that operation is simple and convenient. A primary surge current and a secondary surge current are effectively inhibited, and the impact damage of the surge currents to circuit devices is avoided. Meanwhile, the service lives of the relays are prolonged.

Description

technical field [0001] The invention relates to the technical field of charging circuits, in particular to a soft-start charging circuit and a control method thereof. Background technique [0002] The commonly used start-up charging scheme in inverter air conditioners is mainly realized by connecting a relay in parallel with the negative electrode of the DC bus in series with a resistor. But at the moment when the charging circuit is powered on, the resistance and inductance in the circuit can only suppress the surge current, and it is difficult to reduce the current to a reasonable range. At the same time, the bus voltage can only be charged to about 500V. Due to the voltage difference, a secondary surge current will be generated when the relay is closed. After the charging is completed, the relay is connected in series in the main circuit for a long time, and there are problems such as contact adhesion and short life. The main circuit current is a direct current with ric...

AI Technical Summary

Problems solved by technology

But at the moment when the charging circuit is powered on, the resistance and inductance in the circuit can only suppress the surge current, and it is difficult to reduce the current to a reasonable range

At the same time, the bus voltage can only be charged to about 500V. Due to the voltage difference, a secondary surge current will be generated when the relay pulls in.

After the charging is completed, the relay is connected in series in the main circuit for a long time, and there are problems such as contact adhesion and short life.

The main circuit current is a direct current with rich harmonics, and it is required to select a reliable direct current relay or contactor, and the cost of such devices is very high

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