Raydium Semiconductor Corporation

Yu-Nan Yen

Yung-Hsiang Yang

Chih-Wei Chu

A light-emitting diode (LED) driver is provided. The LED driver, providing a drive voltage for driving an LED circuit according to an input voltage, includes a current regulator, a dimming signal generator, and a boost converter. In response to a pulse width modulation (PWM) dimming signal, the current regulator enables the LED circuit in a first PWM period and disables the LED circuit outside the first PWM period. The dimming generator generates a prolonged PWM dimming signal according to the PWM dimming signal. The prolonged PWM dimming signal has a prolonged period, a length of which is associated with a level of an input voltage. In response to the prolonged PWM dimming signal, the boost converter is enabled in a second PWM period and maintains a level of the drive voltage according to the input voltage.

LED driver

A control circuit applied in a light emitting diode (LED) driver includes a counter, a sample circuit, and a signal source. The counter counts a parameter indicating the duty cycle width of a dimming signal in response to a front edge of the dimming signal. The sample circuit obtains a sample signal by means of sampling the most significant bit (MSB) of the parameter in response to the rear edge of the dimming signal. The duty cycle width is determined to be greater than a threshold value and smaller than that when the sample signal corresponds with a terminal value and an initial value, respectively. The signal source provides a reference voltage corresponding to first level and that corresponding to second level, higher than the first level, to drive a boost converter of the LED driver in response to the terminal value and the initial value, respectively.

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Zhudong, Taiwan

Yu-Nan Yen