DSP controlled Buck/Boost power factor correction for telephony rectifiers

A cascaded buck/boost circuit using a common inductor is useful for power factor correction off 480 VAC mains because it generates traditional DC link voltages of about 400 VDC. However the necessary dual-mode control is not readily available in specialized IC controllers. This means designing a custom discrete controller or utilizing a general purpose programmable controller. This paper describes a Buck/Boost power factor corrector that utilizes a digital signal processor (DSP) for control. PWM algorithms are identified and coded for use with the Analog Devices ADMC401 DSP controller. MATLAB models allow early testing and optimizing of the code for fast execution within each high frequency cycle. Finally a bench prototype is constructed to demonstrate the approach.