LED drive circuit including a plurality of LEDs connected in series
Abstract:
The LED drive circuit has a rectifying circuit that rectifies an alternating-current voltage, an LED string including a plurality of LEDs connected in series, a first switch whose one end is connected to a cathode of an LED in a last stage of the LED string, a capacitor whose one end is connected to the other end of the first switch, a second switch that is connected between one end of the capacitor and the anode of the LED in the first stage of the LED string, and a third switch that is connected between the cathode of the LED in the last stage of the LED string and a second terminal of the rectifying circuit, and which turns on when the full-wave rectified voltage is lower than a charge start voltage and turns off when the full-wave rectified voltage is higher than or equal to the charge start voltage.
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