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Projector lamps thyristor AC regulating voltage circuit

2016-08-10 22:17  
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Projector lamps thyristor AC regulating voltage circuit
In order to steady projector lamps L's brightness, it uses thyristor AC regulating voltage circuit. So that it adds thyristor T5 to the AC bridge road. It's triggering pulse is produced by unijunction transistor VT4. The transistors VT1, VT2 and light activated triode VT3 has the same function. When projector lamps' light changing with power voltage's change,light activated triode's value changes, and the voltage phase which controls unijunction transistor changes too, so that the pulse triggering transistor's phase moves to increase or decreae the transistor conduction time, L voltage approximate remain, the brightness of the projector lamps also approximate remain, then the light keeps stability.