A new PWM controller with one cycle response

Abstract

This paper proposes a new nonlinear control technique that has one cycle response, does not need a resettable integrator in the control path, and has nearly constant switching frequency. It obtains one cycle response by forcing the error between the switched-variable and the control reference to zero, each cycle. The on-pulse of the controller is adjusted each cycle by a simple circuit to ensure almost constant switching frequency. The small switching frequency variation due to variations in the reference signal and supply voltage and delays in the circuit are quantified. An additional improvement is achieved by using double edge modulation. An experimental 10 kHz bandwidth 100 Watt RMS power audio amplifier using the control method shows THD+N less than 0.62% and power supply ripple rejection (PSRR) of 56 dB demonstrating the applicability of this control technique for high fidelity audio applications.