Patent ID: 7772903
Filing Date: 2010-08-10
Classification: H03K

Abstract:
1. A pulse width modulation circuit capable of linearly adjusting duty cycle with voltage, comprising: an input voltage source for generating an input voltage; a regulator coupled to the input voltage source for generating a regulated voltage; a first voltage-dividing unit coupled to the regulator and a ground terminal for providing a first divided voltage; a second voltage-dividing unit coupled to the regulator and the ground terminal for providing a second divided voltage; a third voltage-dividing unit coupled to the input voltage source and the ground terminal for providing a third divided voltage; a voltage adder coupled to the first voltage-dividing unit and the third voltage-dividing unit for adding the first divided voltage and the third divided voltage for generating a high level voltage; a waveform generator coupled to the voltage adder and the third voltage-dividing unit for generating an oscillating signal according to the high level voltage and the third divided voltage; and a comparator having a first input terminal coupled to the second voltage-dividing unit, a second terminal coupled to the waveform generator, and an output terminal for comparing the second divided voltage with the oscillating signal to output a pulse width modulation signal through the output terminal.