Patent ID: 7710214

Claim:
A pulse width modulation (PWM) structure enabling regulated duty cycle, comprising: a DC power supply unit for supplying a voltage source and generating a voltage signal; a signal generating unit for generating a waveform signal; a voltage-dividing resistor unit for setting voltage levels for the signal generating unit; a reference voltage unit having a voltage regulator, a fifth resistor element, and a sixth resistor element for setting a voltage value from an external circuit or an internal circuit; and a comparing unit for receiving and comparing signals from the signal generating unit and the reference voltage unit, and outputting a comparison signal; whereby when the DC power supply unit sends a voltage signal to the voltage-dividing resistor unit, the latter receives the voltage signal and sets voltage levels, so that the waveform signal generated by the signal generating unit regulates voltage levels thereof according to the received voltage signal before sending the waveform signal to the comparing unit; and the comparing unit compares the signals received from the signal generating unit and the reference voltage unit and outputs a comparison signal, so that the finally output signal is substantially linear and smooth.