PWM power supply with constant RMS output voltage control

摘要

A control system and method for supplying a constant RMS voltage to a load includes a outer control loop for monitoring a characteristic variable of the system and an inner control loop for maintaining the power delivered to the load as a function of the received input power. A pulse width modulator (PWM) coupled to both control loops delivers pulses representative of an unregulated input voltage duty cycle. The inner control loop compares the duty cycle representation of the input voltage with a duty cycle representation of the pulse and generates a control signal to the PWM accordingly.