Converter adaptable to wide range output voltage and control method thereof

A method for controlling a converter suitable for delivering a wide range output voltage to a load, comprising:

• providing a converter, wherein the converter comprises a PWM half-bridge circuit, and the PWM half-bridge circuit comprises:
• a primary circuit comprising a primary switching bridge arm formed by a first power switch and a second power switch connected in series;
• a transformer comprising a primary coil coupled to the primary circuit, and a secondary coil;
• a secondary rectifier circuit comprising at least two synchronous rectifiers, and each of the at least two synchronous rectifiers having an input end coupled to the secondary coil;
• and
• an output filter circuit comprising an output inductor and an output capacitor, and coupled between an output end of the secondary rectifier circuit and the load;
• controlling the PWM half-bridge circuit to enter into a discontinuous conduction mode by regulating a switching frequency;
• when the PWM half-bridge circuit operates in the discontinuous conduction mode, oscillation occurs among the output inductor, a magnetizing inductor of the transformer and a parasitic capacitor of the PWM half-bridge circuit, and when a midpoint voltage of the primary switching bridge arm reaches a valley or a peak, turning on the corresponding first power switch or second power switch.