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Zero-Voltage -Transition Buck Converter for High Step-Down DC?DC Conversion with Low EMI
Ali Ariyan and Mohammad Rouhollah Yazdani
Abstract In this study, a new zero-voltage transition (ZVT) buck converter with coupled inductor using a synchronous rectifier and a lossless clamp circuit is proposed. The regular buck converter with tapped inductor has extended duty cycle for high step-down applications. However, the leakage inductance of the coupled inductor produced considerable voltage spikes across the switch. A lossless clamp circuit is used in the proposed converter to overcome this problem. The freewheeling diode was replaced with a synchronous rectifier to reduce conduction losses in the proposed converter. ZVT conditions at turn-on and turn-off instants were provided for the main switch. The synchronous rectifier switch turned on under zero-voltage switching, and the auxiliary switch turn-on and turn-off were under zero-current condition. Experimental results of a 100 W?100 kHz prototype are provided to justify the validity of the theoretical analysis. Moreover, the conducted electromagnetic interference of the proposed converter is measured and compared with its hard-switching counterpart.
Keyword Coupled inductor, Electromagnetic interference (EMI), High step-down converter, Synchronous rectifier, Zero-voltage transition (ZVT), Zero-current transition (ZCT)
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