| 摘要 |
PURPOSE:To prevent an inductive load from being damaged by an overcurrent by constituting a phase controller so that a thyristor is not turned on for a specific time in a phase deviation section between the voltage and current of a power source. CONSTITUTION:The phase controller consists of an AC power source 1, a transformer T2, diodes D1-D6, resistances R0-R21, capacitors C1-C3, operational amplifiers Q1 and Q4, a timer Q2, PNP type transistors Q3, and Q6-Q8, an LED 7, and a comparator Q5. The timer Q2 in the circuit of the upper half part of a figure is a protecting circuit for the inductive load and has a protection time longer than the time constant that the inductive load has, thereby preventing an overcurrent flowing to the inductive load. Further, the lower half circuit of the figure is a phase control circuit which makes the quantity of light of a lamp 2 constant and the quantity of light of the lamp is made constant without reference to variation in source voltage.
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