This paper proposes a novel phase-shifted zerovoltage and zero-current-switching (ZVZCS) pulsewidth modulation full-bridge converter, which realizes ZVS for the leading leg and ZCS for the lagging leg. A blocking capacitor is added in series with the primary winding of the transformer to make the primary current decay to zero during zero state to ensure ZCS for the lagging leg. In order to prevent the primary current from reversing during zero state, two diodes in series with the lagging leg are added. The principle of operation, steady-state analysis, and design procedures are presented. The experimental results are also included to verify the theoretical analysis.

A resonant capacitor is introduced to the current-doubler-rectifier zero-voltage-switching pulsewidth-modulation full-bridge converter to alleviate the limit for the leakage inductance of the transformer. In this letter, the effect and calculation of the introduced resonant capacitor are analyzed and verified by a 540-W prototype converter.

Phase-shifted ZVS PWM full-bridge converter realizes ZVS and eliminates the voltage oscillation caused by the reverse recovery of the rectifier diodes by introducing a resonant inductance and two clamping diodes. This paper improves the converter just by exchanging the position of the resonant inductance and the transformer such that the transformer is connected with the lagging leg. The improved converter has several advantages over the original counterpart, e. g., the clamping diodes conduct only once in a switching cycle, and the resonant inductance current is smaller in zero state, leading to a higher efficiency and reduced duty cycle loss. A blocking capacitor is usually introduced to the primary side to prevent the transformer from saturating, this paper analyzes the effects of the blocking capacitor in different positions, and a best scheme is determined. A 2850W prototype converter is built to verify the effectiveness of the improved converter and the best scheme for the blocking capacitor.

This paper proposes a zero-voltage-switching (ZVS) pulse-width modulation (PWM) hybrid full-bridge three-level converter, which has a three-level leg and a two-level leg. The switches of the three-level leg sustain only the half of the input voltage, and they can realize ZVS in a wide load range. The switches of the two-level leg sustain the input voltage, and they can realize ZVS with the use of the resonant inductance. The secondary rectified voltage is a three-level waveform having lower high-frequency content compared with that of the traditional full-bridge converters, which can reduce the output filter, and as a result, the dynamic response of the converter is improved. The voltage stress of the rectifier diode is reduced also. The input current of the converter has quite little ripple, so the input filter can also be significantly reduced. The operation principle of the proposed converter is analyzed and verified by the experimental results.

A zero-voltage-switching pulsewidth-modulation three-level (ZVS PWM TL) converter realizes ZVS for the switches with the use of the leakage inductance (or external resonant inductance) and the output capacitors of the switches, however, the rectifier diodes suffer from reverse recovery which results in oscillation and voltage spike. In order to solve this problem, this paper proposes a novel ZVS PWM TL converter, which introduces two clamping diodes to the basic TL converter to eliminate the oscillation and clamp the rectified voltage to the reflected input voltage; in the meanwhile, all the switches keep to realize ZVS. Furthermore, the proposed ZVS PWM TL converter can be simplified by removing the two freewheeling diodes. The operation principle of the novel converter and the simplified converter are analyzed and are verified by a prototype converter. The experimental results are also included in this paper.

This paper proposes a new family of zero-voltageswitching multi-resonant three-level converters (ZVS-MRTLCs), which is derived by introducing a LCC multi-resonant network to the basic three-level converters. The unique arrangement of a multi-resonant network results in absorption of all major parasitic components in the resonant circuit, including switch output capacitor, diode junction capacitor and transformer leakage inductor. Compared with the traditional multi-resonant converters (MRCs), which is a two-level converter, the proposed converters achieve ZVS in a wider load range, reduce the voltage stress on the switches and diodes, and the filter can be reduced significantly. Buck ZVS-MR-TLC is taken as the example to illustrate the operation principle, characteristics and the advantages over the Buck ZVS-MRC. A 1kW prototype converter is built in our lab to verify the theoretical analysis.

This paper proposes a family of modulation strategies for PWM three-level (TL) converters. The modulation strategies can be classified into two kinds according to the turn-off sequence of the two switches of the pair of switches. The concept of the leading switches and the lagging switches is introduced to realize soft-switching for PWM TL converters. The realization of soft-switching for both the leading switches and the lagging switches is proposed, based on which, soft-switching PWM TL converters can be classified into two kinds: zero-voltage-switching (ZVS) and zero-voltage and zero-current-switching (ZVZCS), for which the suitable modulation strategies are pointed out respectively from the family of modulation strategies. A novel ZVZCS TL converter is proposed, its operation principle and parameter design are analyzed, and the experimental results are included also.

This paper proposes a zero-voltage-switching (ZVS) pulse-width modulation three-level converter with current-doubler-rectifier, which achieves ZVS for all the switches under wide load range and in a wide line range. The rectifier diodes commutate naturally, therefore no oscillation occurs. The determination of the output filter inductance and the blocking capacitor is discussed in details. The experimental results are presented to verify the operation principle of the proposed converter.

A special requirement of the voltage regulator module (VRM) is fast transient response with fight output voltage tolerance. This paper proposes an Interleaved Three-Level Forward Converter (ITLFC), which can reduce the output inductor significantly so that the transient response is improved. Further analysis shows that, for VRM, the output capacitor can be reduced as well, which means the higher power density can be achieved. So ITLFC is very suitable for the application of VRM. A 48V input, 0.8V/100A output prototype is built to verify the operation principle of the proposed ITLFC.

Boost converter is widely used as active power factor correction (PFC) pre-regulator. Its input voltage range is universal (90-265V), and its output voltage is regulated at about 380V. At low line (90V) the switch's rms current is high, so the conduction loss of power switch MOSFET is large and the efficiency of whole converter is very low. This paper proposes a new control method that the output voltage varies with the input voltage change. Under this control the MOSFET's on-time is shortened, and the switch's rms current decreases, which reduces the conduction loss and increases the Boost converter efficiency. The distribution of power loss is analyzed by computing software (mathcad 2000) and the realization of this special control method is given. A 1200W Boost power factor corrector with average current control is built up. In order to improve the diode's turn-off loss the performance of a 600V, 12A silicon carbide (SiC) Schottky diode is also experimentally evaluated. Measurements of overall efficiency and reverse recovery behavior are compared between SiC diode and fast recovery diode.