Analysis of a Boost PFC Pre-regulator Operated in both CRM and DCM

Abstract

PFC (Power Factor Correction) power supplies are required to provide high input power factor and tight output voltage regulation [1]. Through analyzing the characteristics of various PFC converter modes, this paper is about the design and simulation of a boost PFC pre-regulator. This boost PFC pre-regulator takes advantage of both CRM(Critical Conduction Mode) and DCM(Discontinuous Conduction Mode) operating modes that can help to simplify the front−ended filter design, to reduce the costs and to improve the reliability of the circuit. Andthis paper presents a 100W PFC circuit and the computation methods of essential circuit parameters. The experimental results prove that the PFC circuit has the following characteristics:simple circuit, convenient debugger, high power factor, reliable and stable work. Introduction The issue of how to increase the efficiency of electronic power systems has been attracting more and more attention in recent years. Power grid connects more and more electronic equipments which employ rectifier in large scale. Therefore, harmonic pollution of power grid has emerged. The traditional means of ac-to-dc conversion involves a rectifier followed by a large filter capacitor which can produce a dc voltage from the utility ac line. This technique is well-understood, simple and inexpensive. However, the line delivers no current until the line voltage is close to a maximal value and the effect of harmonic currents reduces the efficiency of the electric power system. Fig.1 Two-stage PFC power supply circuit topology For PF, if both current and voltage are sinusoidal and in phase, the PF is 1.0. If both are sinusoidal but not in phase, the power factor is the cosine of the phase angle. However, PFC converter forces the input current to follow the input voltage that results in a unity power factor. PFC can be modeled in many approaches [2]. A block diagram of the two-stage PFC power supply is depicted in Fig.1. In order to improve PF, APFC (Active Power Factor Correction) technologies are employed in equipments widely. As a result of boost converter's special merit, it gets many applications in low power single-phase PFC systems [3]. The boost converter can operate in various modes such as CCM (Continuous Conduction Mode), DCM and CRM. The comparisons between different PFC converter modes and the description of them are showed in Table.1.