Abstract：This paper proposes a constant frequency PWM controlled unidirectional resonant converter by reusing resonant inductor. To form a flyback auxiliary circuit in series at output, a secondary winding with rectifier diode is added to the resonant inductor. Therefore, the output voltage regulation is achieved by controlling auxiliary switch to reuse resonant inductor operating in flyback mode. Unlike conventional unidirectional resonant converters, the proposed converter adopts constant frequency PWM control. Thus, ZVZCS is realized in full input range. Besides, conduction loss is reduced by increasing magnetizing inductor, and the magnetic components design is simplified. Furthermore, voltage pike caused by leakage inductor is also eliminated due to the clamp capacitor. The topology, control scheme and operating principle are analyzed in detail. The relationship between duty cycle and voltage ratio is calculated. Based on the theoretical analysis, the data obtained by the prototype (41~53V input, 24V/2A output) demonstrate the correctness and feasibility.
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2018, Vol. 33 
