PWM signal generating circuit for DC-DC converter using dimming signal and LED driving circuit having the same in direct digital dimming method

摘要

An LED driving circuit is provided. The LED driving circuit includes an input unit which receives an input dimming signal for driving an LED array, a PWM signal generating unit which extends an on-period of the input dimming signal to form an extended dimming signal, and generates a PWM signal using the extended dimming signal, a DC-DC converter which supplies output voltage to the LED array using the PWM signal, and an LED driving unit which drives the LED array using the input dimming signal.

主权项

1. A pulse width modulation (PWM) signal generating circuit, comprising:
a signal extending circuit configured to
receive an input dimming signal, wherein the input dimming signal comprises a plurality of pulses alternately having an on-period and off-period, andgenerate an extended dimming signal, wherein the extended dimming signal has, for each on-period of the input dimming signal, an on-period exceeding the on-period of the input dimming signal; an oscillator configured to generate a clock signal not synchronized with the input dimming signal; and a signal generating circuit configured to generate a PWM signal pulse for each on-period of the extended dimming signal, in response to the clock signal having a falling edge during the on-period of the extended dimming signal.