PWM audio power amplifiers: sigma delta versus sliding mode control

Sigma delta and robust sliding mode controllers for high fidelity PWM audio power amplifiers are designed and evaluated. The used theoretical approach allows, for both controllers, an integrated design of the control, modulator and semiconductor drive electronics. The sliding mode controller shows much better tracking performance with faster dynamics, no steady-state errors, flatter passband response, due to the intrinsic "Just In Time" (JIT) switching operation, step response without overshoot due to the third-order Bessel control polynomial, and short circuit proof operation. Test results confirm that the sliding mode controller exceeds the performance of existing sigma delta controllers. Furthermore, the proposed sliding mode approach provides a new, nonlinear theoretical frame for solving the control problem of PWM audio power amplifiers with output filters.