A new family of active auxiliary circuits that allow the power switch in single switch, pulsewidth modulated converters to operate with zero-voltage switching is proposed in this paper. The main feature of an auxiliary circuit belonging to this family is that the auxiliary switch can operate with a zero-current switching turn-on and turn-off without increasing the peak current stresses of the main switch. This is an improvement over previous proposed auxiliary circuits where either the auxiliary switch operates with a hard turn-off or the circuit itself increases the peak stresses of the main switch. In this paper, the fundamental principles behind the proposed family of active auxiliary circuits are explained. Based on these principles, an example auxiliary circuit is systematically derived and presented along with several other auxiliary circuits belonging to the new family. The operation of a boost converter operating with the example auxiliary circuit is discussed in detail, and general guidelines for the design and implementation of auxiliary circuits belonging to the new family are given. The feasibility of the example auxiliary circuit is confirmed by experimental results obtained from a 500-W, 100-kHz boost converter laboratory prototype.

A new family of zero-voltage-transition PWM converters with dual active auxiliary circuits

A novel class of DC to DC power converters and a method of conversion is provided using high-frequency switched capacitors where the switches are implemented by CMOS transistors or diodes on an integrated-circuit chip and using inductors to limit charging current. High efficiency is achieved using inductors to reduce energy losses in circuit capacitors by high frequency switching when inductor current is zero and capacitor voltage is maximized. The high-frequency (100 MHz or greater) operation of the converter circuit permits the use of inductors with a low inductance value on the order of 100 nH (100×10 −9 Henrys) capable of fabrication directly on an integrated-circuit (IC) chip. The use of CMOS integrated components allows the entire converter to be formed on a single IC chip, saving significant space within the portable system. Output voltage and current is high enough to permit EEPROM programming. In addition, fluctuations in the output voltage (ripple voltage) are substantially eliminated when several of the converter circuits are used in parallel.

Efficient CMOS DC-DC converters based on switched capacitor power supplies with inductive current limiters

A new soft-switched ac-dc single-stage pulse width modulation (PWM) full-bridge converter is proposed. The converter operates with zero-voltage switching (ZVS), fixed switching frequency, and with a continuous input current that is sinusoidal and in phase with the input voltage. This is in contrast with other ac-dc single-stage PWM full-bridge converters that are either resonant converters operating with variable switching frequency control and high conduction losses, converters whose switches cannot operate with ZVS, or converters that cannot perform power factor correction (PFC) unless the input current is discontinuous. All converter switches operate with soft-switching due to a simple auxiliary circuit that is used for only a small fraction of the switching cycle. The operation of the converter is explained and analyzed, guidelines for the design of the converter are given, and its feasibility is shown with results obtained from an experimental prototype.

Single-stage ZVS PWM full-bridge converter

A flyback converter has a main switch coupling a primary winding of a transformer between supply terminals, a duty cycle of the main switch controlling an output of the converter derived from a secondary winding of the transformer. Soft (zero voltage) switching of the main switch is facilitated by a snubber capacitor in parallel with the main switch. An auxiliary circuit coupled in parallel with the snubber capacitor and main switch includes a series-connected auxiliary switch, capacitor, and inductor coupled via another inductor to a full wave rectifier arrangement for recovering energy from the snubber capacitor. Resonant circuits provided by the auxiliary circuit facilitate soft switching of the auxiliary switch for low power loss and high frequency operation. The switches can be MOSFETs with reverse-poled diodes in parallel with their drain-source paths.

Flyback converter with soft switching using auxiliary switch and resonant circuit

This paper presents the steady-state analysis and design of a forward-flyback converter that employs two transformers and an output inductor. By utilizing two separate transformers, the proposed converter allows a low-profile design to be readily implemented while retaining the merits of a conventional single-transformer forward-flyback converter with secondary center tap. By using an output inductor, the proposed converter efficiently reduces the output ripple to an acceptable level. The design and performance of the proposed converter are confirmed with experiments on a 100 W prototype converter.

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Analysis and design of a forward-flyback converter employing two transformers

A zero voltage switching forward converter topology is presented in this paper. The topology employs an auxiliary circuit. Only a few small rating components and devices are added. The merits of the proposed topology include: lossless switching independent of the input and load conditions, simple control and power circuitry, and ability to operate in either voltage or current mode control. A steady state analysis is presented and the design procedure is illustrated. A 100 W 300 kHz prototype zero voltage switching forward converter is built which shows an efficiency improvement of approximately 5% as compared to a conventional hard switching forward converter.

H. Jin

Papers

A zero voltage switching forward converter topology