Light-emitting device control circuit

摘要

In a control circuit for a light-emitting device, a reference voltage generation circuit detects a full-wave rectified voltage and generates a first voltage as well as generating a second voltage by converting the rectified voltage into a DC voltage. A voltage corresponding to a difference between the first voltage and the second voltage or a voltage corresponding to a ratio of the first voltage to the second voltage is generated as a reference voltage by a subtraction circuit or by a division circuit, respectively. As a result, a change in amplitude of the reference voltage can be suppressed when amplitude of the rectified voltage is varied due to a variation in an AC input voltage supplied from an AC power supply.

主权项

1. A control circuit for a light-emitting device, comprising:
a rectification circuit rectifying an AC voltage to generate a rectified voltage; a switching device configured to turn on and off the light emitting device; a reference voltage generation circuit generating a reference voltage; a first comparator comparing a comparison voltage with the reference voltage, the comparison voltage corresponding to a current flowing through the light-emitting device in response to the rectified voltage; and a flip-flop configured to be set in response to a trigger pulse and reset in response to a result of comparison by the first comparator, the flip-flop outputting an output voltage and controlling the switching device in accordance with the output voltage, wherein the reference voltage generation circuit is configured so that a change in amplitude of the reference voltage is suppressed when amplitude of the AC voltage varies.