Design of digital robust controller for PWM power amplifier and bumpless mode switching

In this paper a multi-stage switching type digital controller is proposed for spreading capacitance load range more and improving transient characteristics for inductance load. In the previous proposed controller, the configuration of the controller is the same to all loads. At inductive load, there is a possibility that the transient characteristics may become bad and the specification may not be satisfied. Therefore, a load current is estimated at inductive load, and the controller which also uses load current for feedback is configured. A inductance is estimated and a controller is switched to this controller bumplessly. In order to extend the range of capacitance load, a controller is increased from two stage to three stage, and these are switched to each other bumplessly. A DSP is implemented to this digital controller. It is demonstrated from experiments that the multi-stage switching type digital controller is realizable and the given specifications are satisfied.