Switched-capacitor programmable filter for power processors

A switched-capacitor programmable filter is proposed as educational tool for the feedback compensation of power converters. The transfer function of the external feedback network, expressed in the Z-transform domain, can be assigned by means of Multiplying DACs. The cancellation of poles and zeros of switching power cells is precisely implemented even in the case they are complex. An ideal final single pole loop gain transfer function can be obtained after choosing the gain-bandwidth product and the dominant pole. Educational laboratories of power electronics in Universities awarding the MS and the Ph.D degrees can benefit from this tool. Duly reprogrammed, it avoids the realization of a dedicated controller for each power conversion exercise and it opens the possibility to investigate some aspects of the dynamic stability experimentally. The paper illustrates the compensation of a pulse width modulated step-down DC/DC converter. Measurements well fit the theoretical forecasts.