A new DC/DC converter with zero voltage switching is proposed for applications with high input voltage and high load current. The proposed converter has two circuit modules that share load current and power rating. Interleaved pulse-width modulation (PWM) is adopted to generate switch control signals. Thus, ripple currents are reduced at the input and output sides. For high-voltage applications, each circuit module includes two half-bridge legs that are connected in series to reduce switch voltage rating to V in /2. These legs are controlled with the use of asymmetric PWM. To reduce the current rating of rectifier diodes and share load current for high-load-current applications, two center-tapped rectifiers are adopted in each circuit module. The primary windings of two transformers are connected in series at the high voltage side to balance output inductor currents. Two series capacitors are adopted at the AC terminals of the two half-bridge legs to balance the two input capacitor voltages. The resonant behavior of the inductance and capacitance at the transition interval enable MOSFETs to be switched on under zero voltage switching. The circuit configuration, system characteristics, and design are discussed in detail. Experiments based on a laboratory prototype are conducted to verify the effectiveness of the proposed converter.
This paper presents a new DC/DC converter for high input voltage and high load current applications. In order to adopt low voltage rating power devices in high voltage applications, two split capacitors with four active switches are used in the primary side to reduce the voltage stress of power switches at V in /2. Two flying capacitances are used in order to automatically balance two split capacitor voltages in every switching cycle. The proposed converter includes two resonant circuits to share the load current and to reduce the current stress of passive components. If the switching frequency is less than the series resonant frequency, power switches can be turned on under zero voltage switching and rectifier diodes can be turned off under zero current switching. Therefore, the switching losses on power semiconductors are reduced. The interleaved pulsewidth modulation is adopted to further reduce the ripple current at output side. Thus, the output filter inductances can be reduced. Finally, experiments with a 1.2kW prototype are provided to verify the effectiveness of the proposed converter.
A new three-level zero voltage switching (ZVS) pulse-width modulation (PWM) converter with the balanced output currents is presented for medium input voltage and high load current applications. Three-level converter with two clamped diodes and one flying capacitor is adopted to reduce the voltage stress of power semiconductors for medium voltage application and achieve ZVS operation for power MOSFETs. In order to reduce the size of the magnetic core and copper windings and to decrease the current rating of the rectifier diodes, three circuit cells are adopted in the proposed converter for high current applications. In each circuit cell, two transformers with a series connection are used in order to balance the output currents. To overcome the drawback of a wide range of switching frequencies in conventional series resonant converters, the duty cycle PWM control is adopted in the proposed circuit to achieve ZVS turn-on for power MOSFETs and zero current switching (ZCS) turn-off for rectifier diodes. Finally, experimental results are provided to demonstrate the performance of the proposed converter.
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