Design optimization of switching voltage regulators with power factor correction

Abstract

In general, a switching regulator with power-factor-correction (PFC) is composed of a PFC pre-regulator and a voltage regulator in order to satisfy both low input harmonic current distortion and fast voltage regulation simultaneously. The simplest approach to construct the switching regulator is to cascade the PFC pre-regulator with the voltage regulator. The input power of the switching regulator is processed by the PFC pre-regulator and the voltage regulator serially, so the efficiency of this switching regulator is inevitably deteriorated. Although the noncascading connection between the PFC pre-regulator and the voltage regulator is an effective method for constructing efficient switching regulators which can satisfy the relevant regulatory requirements for harmonic emissions, there is a lack of detailed discussion on the analyses of the achievable performances of different types of noncascading PFC switching regulators. This thesis presents the theoretical analysis with simulation results of the achievable performances of different types of noncascading PFC switching regulators and discusses the design aspects of implementing two types of noncascading PFC switching regulators at different output power levels. The particular design considerations such as the gained efficiency, the input current harmonics, and the size of the energy storage for load voltage regulation of each type of noncascading PFC switching regulators are discussed. This thesis also investigates the output load transient characteristics of PFC pre-regulators. The cause of sluggish load transient response of PFC pre-regulators is explained and an analog implementation to accelerate the load transient response without degrading the quality of the input current of PFC pre-regulators is proposed. Experiments are conducted to validate the analog implementation that provides sufficient improvement in the load transient response of PFC pre-regulators. An analytical approach to calculating the relationship between the inductor current, the output capacitance, and the output voltage ripple of continuous-conduction-mode (CCM) boost PFC pre-regulators is presented and some dynamic characteristics of output voltage are studied for different waveshapes of the input current.