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Light-operated Starter Circuit

2014-11-10 04:05  
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Light-operated Starter Circuit
The traditional starter of fluorescent lamp is neon-tube.The start time of neon starter is greatly affected by ambient temperature and voltage,so that its utility is not ideal.As shown in figure is a light-operated starter circuit,it can solve the problems that fluorescent lamps start slowly or cannot start because of temperature reduction and voltage changes.The main component of circuit are thyristor and photo-coupler.When switch K is on,220V commercial power is reduced by fluorescent filament and R1,RC C1 and divided by R4,then,commutated by bridge rectifier VD1,filtered by C2,and through 15V voltage-regulator diode VD2,and,finally,the commercial power offers electricity to unidirectional thyristor and photo-coupler.The control voltage of unidirectional thyristor is offered by voltage-regulator diode VD3 as well as C3 and the thyristor SCR can be connected within 1s.Then,LED of photo-coupler U1 is on power and photistor is connected by light,bringing lots of electric current to fluorescent filament to preheat. Moreover,the conductive photistor makes the control end of electronic starter short and the starter shuts down.Thus,photistor of photo-coupler stops working,which is equal to a filament circuit cut.