High-frequency AC (HFAC) power distribution systems have been the subject of great interest over the last several decades. This paper presents a thorough review of different HFAC power distribution architectures on which the authors have worked in the last 30 years. The review is focused on the HFAC power architectures and topologies for space, telecommunications, and computer applications. Detail of each architecture is given and evaluated in terms of performance specific to each application.

A Review of High-Frequency Power Distribution Systems: For Space, Telecommunication, and Computer Applications

A new asymmetric half-bridge (HB) resonant converter for dc/dc power system with a wide range of low input voltage is proposed in this paper. The proposed converter is easily derived based on the switch integration technique, merging a buck–boost, which is the same with the active-clamp forward's primary circuit, and the HB LLC resonant converter. By adopting the buck–boost circuit in front of the HB LLC resonant converter, higher input voltage of LLC resonant converter stage can be achieved. As a result, the primary conduction loss can be significantly reduced. In addition, to cover wide input voltage range, an asymmetric pulse width modulation control is applied. It can mitigate the design limitation for a high efficiency. Moreover, the proposed converter can achieve not only the small conduction loss and the optimal design for high efficiency, but also high power density and low cost due to the switch integration technique. The validity of the proposed converter is confirmed by the experimental results of a prototype converter with 36–72 V DC input and 300 W (12 V/25 A) output.

An Asymmetric Half-Bridge Resonant Converter Having a Reduced Conduction Loss for DC/DC Power Applications With a Wide Range of Low Input Voltage

In this paper, a CLL resonant tank fed by an asymmetrical pulsewidth-modulated (APWM) drive train is presented as an attractive option for low-power point-of-use power supplies used in telecom applications. This configuration can guarantee zero-voltage switching (ZVS) for an extended input voltage range of 35-75 V, while significantly reducing the associated conduction loss present in existing topologies. Proper resonant tank design will ensure efficient operation over the entire working range by maintaining ZVS for all line and load conditions, as well as minimizing the conduction loss by decreasing the circulating-current commensurate with load. Analysis of the converter topology is conducted, and a design procedure is presented. Experimental results from a 25-W 48-V/2.5-V proof-of-concept prototype are presented to validate the analysis and simulation results and to highlight the merits of the proposed topology. The proposed converter is shown to provide a 7%-14% efficiency improvement over a reference topology.

A CLL Resonant Asymmetrical Pulsewidth-Modulated Converter With Improved Efficiency

A hysteretic buck converter provides improved regulation control, in particular for buck converter standby operation A comparison circuit compares the output voltage of the buck converter to a waveform that is generated from an indication of the output current of the converter, so that the turn-on time of the converter is advanced as the output current demand increases The resulting action anticipates a reduction in output voltage due to the increased current, preventing an excursion of the output voltage below the ripple voltage minimum The turn-off time of the converter is controlled by an upper threshold that limits the ripple voltage maximum The output current indication may be a measurement of output current, or may be a dynamic value calculated from the input voltage and the output voltage waveform

Hysteretic buck converter having dynamic thresholds

The characteristics of an asymmetrical duty cycle (ADC) controlled LCL-T resonant converter operating at the resonant frequency are studied by solving the state-space model of the converter. Four operating modes are identified having different circuit waveforms representing different device conduction sequences, thereby creating different conditions during the device switching. The mode boundaries are obtained and plotted on the D-Q plane. A region on the D-Q plane is identified for the converter design, where the switches operate under zero-voltage-switching condition. A prototype 500 W, 100 kHz converter is designed and built to experimentally demonstrate the operating modes, control characteristics, and performance of ADC-controlled LCL-T resonant converter.

Characteristics and Design of an Asymmetrical Duty-Cycle-Controlled LCL-T Resonant Converter

A modified asymmetrical pulse-width-modulated resonant dc/dc converter employing an auxiliary circuit will be proposed in this paper. The auxiliary circuit consists of a network of two capacitors and an inductor. The aim of this network is to produce zero-voltage-switching (ZVS) over a wide input voltage range, while reducing the voltage stress on the resonant component. A detailed analysis and performance characteristics are presented. Experimental results for a 5 V, 35 W converter show an efficiency of 83% at a constant operating frequency of 500 kHz. Using metal oxide semiconductor field effect transistors (MOSFETs) as synchronous rectifiers can further reduce power losses and improve the efficiency to be greater than 90%.

S. Mangat

Papers

A modified asymmetrical pulse-width-Modulated resonant DC/DC converter topology