Digital Control Techniques for Single-Phase Power Factor Correction Rectifiers

Tightening governmental regulations and industry standards for input current harmonics and input power factor correction (PFC) of common electronic devices such as servers, computers and televisions continues to increase the need for high-performance, low-cost power factor correction controllers. In response to this need, digital non-linear carrier (DNLC) PFC control has been developed and is presented in this thesis. DNLC PFC control offers many unique advantages over existing PFC control techniques in terms of design simplicity, low harmonic current shaping over a wide load range including CCM and DCM operation and a reliable, inexpensive digital implementation based on low-resolution analog-to-digital converters (A/D\u27s) and digital pulse width modulator (DPWM). Implementation of the controller requires no microcontroller or digital signal processor (DSP) programming, and is well suited for a simple, low-cost integrated-circuit realization. DNLC PFC control is derived and analyzed for single-phase universal input PFC boost rectifiers. Further analysis of the operation of digitally controlled PFC rectifiers leads to the development of voltage loop compensator design constraints that avoid limit-cycling of the voltage loop. It is demonstrated that voltage loop limit-cycling is unavoidable when using traditional PFC control techniques un- der certain output loading conditions. However, it is also shown that voltage loop limit-cycling is avoidable under the same operating conditions when a DNLC PFC controller is implemented. Additionally, a unique output voltage sensing A/D is also developed that improves the PFC voltage loop transient response to load transients when paired with the DNLC PFC controller. Experimental results are shown for a 300W universal input boost PFC rectifier