PULSE WIDTH MODULATION CIRCUIT AND METHOD FOR COMPENSATING PROPAGATION DELAY IN PULSE WIDTH MODULATION CIRCUIT

摘要

PROBLEM TO BE SOLVED: To protect completely the maintenance of synchronization by applying a sawtooth wave signal with a prescribed discharge time by a sufficient time interval enough to compensate a delay to each comparator while being synchronously with the sawtooth wave. SOLUTION: A sawtooth wave signal OSC generated by an oscillator is given to a base of a transistor(TR) Q1 being an input of a circuit. A signal current flowing to high breakdown voltage MOS TRs M4, M9 is equal to a signal current flowing to a TR M5 and TRs Q3, Q4 realizing a voltage follower. In the specific operating state, when a discharge phase of the signal OSC is started, a level of a TR M11 reaches a high level faster than the discharge phase of a signal NEW-OSC. Then a sawtooth wave signal having a shorter discharge time than the discharge time of the signal OSC by a time enough to compensate a delay is generated and given to a comparator PWM. Then the TR M11 reaches a high level faster than the discharge signal of the NEW- OSC to compensate the delay.