Research on Application of Bidirectional Thyristor in the Intelligent Air Filter

Abstract

The bidirectional thyristor can be conducted bidirectionally and has good switching characteristics. The conversion from weak electricity to strong electricity and low power to high power can be realized via bidirectional thyristor. The intelligent air filter monitors indoor air quality and real-time control filer fan start-up and speed adjustment automatically according to the monitoring results. Therefore it can exchange the filtered outside air with the inside air.In the intelligent air filter, the zero-crossing detection circuit and the speed regulating circuit are designed. The zero-crossing Detection Circuit is realized by the photoelectric coupling device TLP521-2, and the accurate zero-crossing pulse is generated every time the power supply voltage passes the zero point. In the interrupt program, the I/O pin of the main control microcomputer is set to control the voltage of the fan to turn on and off, so as to realize the speed regulation.In the intelligent air filter, a total of 11 states are set. In each state, the proportion of different voltage connected, the fan can work at different speeds. When the voltage connected 20% , the speed is very low, increase in turn, when all connected, the speed is maximum. It has been proved by experiments that the characteristics of Sine curve of AC voltage can be guaranteed by half-waveguide pass. Fans can run continuously and stably under different settings, and the noise is even. So that fan speed regulation can be realized , no contact, quick action and high reliability.