In the flyback power supply, the circuits and electrical appliances that use thyristor isolation to control high-power loads

Abstract

The invention discloses a circuit and an electrical appliance for controlling a high-power load by means of thyristor isolation in a flyback power supply, including a high-frequency transformer, an absorbing circuit, a secondary output circuit, an auxiliary power supply circuit, a drive circuit and a thyristor; the auxiliary power supply The circuit is connected to the high-frequency transformer, and the two ends of the auxiliary power supply circuit are connected to the AC phase line input and the analog ground; the output end of the drive circuit is connected to the G pole of the thyristor, which is used to control the conduction of the thyristor. When the flyback power supply starts, the auxiliary power supply circuit has a continuous DC output; when the drive circuit is turned on, the thyristor has a DC input provided by the auxiliary power supply circuit, the purpose of the present invention The purpose is to provide a circuit that utilizes thyristor isolation to control high-power loads in a flyback power supply. An auxiliary power supply circuit is added to the circuit, which can directly provide trigger current for the conduction of the thyristor, and reduce the voltage loss when the thyristor is turned on. Instantaneous current or instantaneous voltage is conducive to passing the EMC test.

Description

technical field [0001] The invention relates to the technical field of a flyback power supply and thyristor drive application, in particular to a circuit and an electrical appliance which use thyristor isolation to control a high-power load in a flyback power supply. Background technique [0002] With the advancement of science and technology and the development of society, people have more and more demands for high-power products, and people are becoming more and more strict about product quality certification, especially in EMC testing. At present, most products that have isolation requirements and need to frequently control high-power load switches generally use the following technologies: [0003] Generally, a switching power supply with a flyback topology is used as a power supply, and a thyristor and a bidirectional optocoupler are used as control devices. The thyristor isolation control circuit is to connect the T2 pole, G pole, current limiting resistor and the outp...

AI Technical Summary

Problems solved by technology

[0004] However, due to the trigger current of the bidirectional thyristor, the current-limiting resistance and the conduction voltage of the bidirectional optocoupler, there will be a large instantaneous voltage and current at the moment when the bidirectional thyristor is turned on, that is, dv / dt and di / dt, especially bidirectional thyristors control high-power devices; and every time the AC mains input passes through the zero point, it is necessary to wait for the voltage across the bidirectional thyristor T2 pole and G pole to reach a certain level before there is enough triggering The current turns on the triac, making it difficult for the product to pass EMC tests

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