Soft switching method for electric-controlled switch of three-phase AC input circuit

Abstract

The invention discloses a soft switching method of an electric control switch of a three-phase AC input circuit. The three-phase AC input circuit comprises a soft start circuit, and after the soft start of the circuit is finished, the method comprises the following steps of: detecting the six-section wave head direct current; attracting to shut the electric control switch at any time between the zero crossing point of ab, ba sections and the voltage peak point of the ba / ab section if the C-phase of a three-phase AC is connected in series with the electric control switch; attracting to shut the electric control switch at any time between the zero crossing point of bc, cb sections and the voltage peak point of the cb / bc section if the A-phase of the three-phase AC is connected in series with the electric control switch; and attracting to shut the electric control switch at any time between the zero crossing point of ac, ca sections and the voltage peak point of the ca / ac section if the B-phase of the three-phase AC is connected in series with the electric control switch. The soft switching method of the invention begins to work at the time when the voltage of the soft start circuit is reduced to the lowest by controlling the electric control switch, thus causing the current peak on the electric control switch to be the minimum, and prolonging the service life of a relay.

Description

technical field [0001] The invention relates to a power supply, in particular to a soft switching method for an electric control switch of a three-phase AC input circuit. Background technique [0002] In the existing switching power supply modules, generally include such as figure 1 The circuit topology shown includes input soft-start circuit, rectifier circuit, filter circuit (generally composed of filter capacitors), main power supply (composed of main DC / DC converter and its output filter circuit), auxiliary power supply and monitoring circuit, etc. Some switching power supplies are also equipped with a power factor correction circuit, that is, a PFC circuit, between the rectifier circuit and the main power supply. [0003] A period of time when the switching power supply module is just connected to the AC power is the start-up process. During the start-up process, the AC input is used to charge the PFC bus capacitor. Due to the large voltage difference between the AC gr...

AI Technical Summary

Problems solved by technology

[0004] However, in the process of turning on the electric control switch, the voltage drop of the input soft-start circuit is transferred to the electric control switch, and a large current peak is generated on the electric control switch, which reduces the life of the electric control switch

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