Source Voltage Sensor-less Digital Control Using Observer for PWM Converter

For promotion of low-priced and reliable PWM converters, it is important to decrease the number of parts which comprise a PWM converter. The proposed control method realizes an integrated control circuit using inexpensive DSP (Digital Signal Processor) to offer unity input power factor without a source voltage sensor. In the method, an observer estimates voltage instead of sensing it. Then, the phase-angle error between the estimated voltage wave and a sine wave generating input current command is made zero by a phase controller based on the Fourier series. The stability of the system is shown by the Popov's method. Experiments demonstrate the system achieves sinusoidal input current and unity power factor.