Wen-Jian Gu

A new method to regulate resonant converters

A resonant frequency-modulation method is presented as an alternative to the switching frequency-modulation method to regulate resonant converters. A switch-controlled inductor and switch-controlled capacitor, in which switching losses are found to be very low due to zero-current or zero-voltage switching, are developed to do so. A new family of resonant converters that are regulated at a fixed switching frequency is proposed. A steady-state analysis of the Class E resonant converter regulated by a switch-controlled capacitor is presented. Theoretical and experimental results verify the validity of the proposed method. The efficiency measured from a breadboard of 1 MHz, 5 V, 25 W Class E regulated resonant DC-DC converter is up to 83%. >

A circuit model for the class E resonant DC-DC converter regulated at a fixed switching frequency

An averaging circuit model is developed for the class E resonant DC-DC converter regulated at a fixed switching frequency. The regulation is achieved by use of an auxiliary switch. The model is obtained based on the circuit analysis using the Fourier series expansion. Steady-state and small-signal dynamic analysis is presented, which reveals that the DC output is well controlled by the control angle of the auxiliary switch and that there exists a right-half-plane zero in the control-to-output transfer function. The analysis results are verified by the experiments. >

Novel self-excited PWM converters with zero-voltage-switched resonant transition using a saturable core

A new family of self-excited pulse-width-modulated (PWM) converters with zero-voltage-switched (ZVS) resonant transition is proposed. A saturable core is used in the transformer to realize the ZVS resonant transition during turn-on and turn-off transition. The waveforms of the voltage across and current the switch the flowing in the switch are quasi-square-wave The converters have the advantages of both PWM and resonant mode converters.<<ETX>>

Steady state analysis of Class E resonant DC-DC converter regulated under fixed switching frequency

Analytical and experimental results are presented for a novel type of Class E resonant DC-DC converter that is regulated by an auxiliary switch. The switching frequency of the converter is fixed. The analysis gives the switching-frequency range for which losses are very low as well as the steady-state characteristics of the converter at these frequencies. Experiments on a 1 MHz, 5 V, 25 W breadboard regulator verify the theoretical results. The measured efficiency is as high as 83%.<<ETX>>

A novel, self-excited, PWM forward converter with ZVS resonant transition using two minor-loop-operated saturable cores

A self-excited forward power converter is proposed. The turn-on and turn-off transitions of the switch are zero voltage switched resonant transitions. Two saturable cores operated in minor B-H loop are used to achieve such transitions. The waveform of the voltage across the switch is trapezoidal, and the current flowing in the switch is a quasi-square-wave. The switching losses are considerably reduced, and the stresses in the switch are significantly suppressed. The converter has load characteristics similar to those of a square-wave pulse-width-modulated (PWM) forward converter. The on duty ratio is modulated by a small current applied to the winding of one core. Experiments on a 350 kHz, 100 W DC-DC power converter show good performance.<<ETX>>