V. Grigore

High power factor rectifier based on buck converter operating in discontinuous capacitor voltage mode

The buck converter with LC input filter operating in discontinuous capacitor voltage mode has inherent power factor correction properties and continuous input current. The paper presents a detailed analysis of the converter operating in this mode, leading to design criteria. Finally, experimental results for a 48 V/sub dc//100 W converter are presented.

A new zero-voltage-transition PWM buck converter

In this paper a new zero-voltage-transition (ZVT) PWM buck converter is presented. An auxiliary circuit (consisting of one active switch and some reactive components) is added to the original buck converter. The auxiliary circuit is inactive during the ON and OFF intervals of the main switch in the normal buck converter. However, the transitions between the two states are controlled by the auxiliary circuit. Prior to turn-on, the voltage across the active switch in the buck converter is forced to zero. Thus, the turn-on losses of the active switch are practically eliminated. At turn-off the auxiliary circuit behaves like a nondissipative passive snubber, reducing the turn-off losses to a great extent. Zero-voltage-transition switching technique almost eliminates switching losses. The active switch operates under ZVT conditions, the passive switch (diode) has a controlled reverse recovery, and the switch in the auxiliary circuit operates under zero-current-switching (ZCS) conditions.

A step-down converter with low ripple input current for power factor correction

Step-down converters can be used to achieve power factor correction when a low output voltage is desired. The paper analyzes a nonisolated, two-inductor, step-down power converter and presents its application to power factor correction, when operating in the continuous conduction mode with average current mode control. The input current of the converter is continuous, since one of the inductors is on the line side. Moreover, for a proper coupling of the two inductors, the ripple of the input current can be significantly reduced. Thus, a PFC preregulator with low output voltage and low-ripple input current is obtained. The paper also presents experimental results for a 48 VDC output-voltage and 200 W output-power power factor correction preregulator, operating with 230 VRMS input voltage.

Input filter design for power factor correction converters operating in discontinuous conduction mode

Power factor correction (PFC) converters operating in discontinuous conduction mode (DCM) are very attractive for use in low-cost and low-power applications, due to simpler control when compared with continuous conduction mode (CCM) operation. Design of the EMI input filter for DCM operation has different constraints in certain aspects, when compared with the CCM case. This paper focuses on particularities of the input filter design in the DCM case.

Analysis of a high power factor rectifier based on discontinuous capacitor voltage mode operation

Discontinuous capacitor voltage mode operation offers inherent power factor correction properties and continuous input current. A detailed analysis of a flyback-derived converter operating in this mode is presented in the paper and its application as a high power factor rectifier is studied. Finally, experimental results are presented.