Semiconductor Components Industries, LLC

Tomoyuki Goto

Shuhei Kawai

Feng Xu

In accordance with an embodiment, a light emitting element driving circuit includes a comparator having an input connected to smoothing circuit and an output connected to a voltage-dividing circuit through a transistor. A drain-to-source resistance of the transistor is connected in parallel with a portion of the voltage dividing circuit. An output signal of the voltage dividing circuit is connected to another comparator that generates a drive transistor drive signal. The drive transistor is connected to one or more light emitting elements. In accordance with another embodiment, a reference voltage is generated in response to a rectified signal and compared with a sense voltage to generate a drive signal that is used to drive the drive transistor. Light is emitted from the one or more light emitting elements in response to the drive signal and the rectified voltage being greater than the forward voltage drops of the one or more light emitting elements.

Light emitting element driving circuit

A TRIAC dimmer gates an AC waveform from an AC power source in proportion to a control signal and outputs a TRIAC pulse having part of the waveform missing. The TRIAC pulse is rectified and is applied to an LED array and the drive current flowing to the LED array is detected at a current detection resistor. The drive current value and a predetermined value are compared at a comparator and in accordance with the comparison result thereof the control transistor is turned off. Then, the TRIAC pulse is converted to a DC voltage signal and in accordance with the obtained DC voltage signal the drive current value or the predetermined value input by the comparator are changed. Furthermore, instead of the TRIAC pulse, a PWM pulse supplied from an external source may also be utilized.

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Ota, Japan

Tomoyuki Goto