Patent ID: 8164318

Claim:
A pulse width modulation (PWM) signal generation circuit for generating a PWM signal to control a switching power supply unit according to a switching cycle thereof, the PWM circuit comprising: an analog-to-digital converter (ADC), operating during a conversion cycle, to generate a digital error signal by comparing, during a present switching cycle, a reference voltage with an input voltage that was obtained during a previous switching cycle, generating a delay output current indicative of a desired delay in generation of the error signal, the desired delay being based on a result of the comparison and based on a phase difference between the previous switching cycle and a previous conversion cycle, and converting the delay output current, after a conversion time delay equal to the desired delay, to the digital error signal, the present conversion cycle ending after the error signal is generated, the ADC including a detector for detecting said phase difference and outputting an indication value indicating said phase difference; and a delay circuit for generating the error signal with the conversion time delay according to the delay output current, the delay circuit further determining the duration of the present conversion cycle according to a delay reference current that is generated based on the reference voltage and said phase difference, the delay circuit including a delay element array having a plurality of delay elements connected in series, the delay output current flowing through the delay elements and controlling a signal transmission time of each delay element of the array to define said conversion time delay, the array converting an analog value of the delay output current to the error signal; a circuit for performing a proportional integral and differential (PID) process on the error, and generating a duty command signal that controls a duty cycle of the PWM signal; and a circuit for generating the PWM signal based on the duty command signal.