Average current mode control apparatus for an AC output amplifier

TLDR: In this article, an inner current error control loop coupled between the AC power output and the PWM, controls the average current in the output inductor by generating a current error signal for inputting to the PWR for conversion to the gate drive signals.

Abstract: A current mode control apparatus generates an AC power output from a DC input source. The apparatus includes a pulse width modulator (PWM) to produce gate drive signals for driving a power output section having an output inductor and connected across the DC input source. An inner current error control loop coupled between the AC power output and the PWM, controls the average current in the output inductor by generating a current error signal for inputting to the PWM for conversion to the gate drive signals. The current error signal is the difference between the average current and a voltage controlled input signal. An outer voltage error control loop coupled between the AC power output and the inner current error control loop generates a voltage error signal based on the difference between the AC power output and a reference AC voltage. The voltage error signal represents a change in demand for current in the output inductor and serves as the voltage controlled input signal to the inner current error control loop. A voltage limiter in the outer voltage error control loop limits the voltage error signal to a maximum value to prevent the average current in said output inductor and thus in said AC power output from exceeding a predetermined limit. The current mode control apparatus is adaptable for use in an uninterruptible power supply for supplying a load with the AC power output.