Llc resonant power converter with current-circulating circuit for enabling light-load regulation

An LLC resonant power converter with a current-circulating circuit for enabling light-load regulation, comprising:

• a half-bridge circuit composed of two power switches connected in series, the half-bridge circuit being connected in parallel to an input voltage;
• a transformer composed of a primary winding and two secondary windings;
• an LLC resonant circuit composed of a resonant inductor, a magnetic inductance, and a resonant capacitor connected in series, wherein the magnetic inductance is inherent in the primary winding, the LLC resonant circuit being connected in parallel to one of the power switches;
• the current-circulating circuit composed of two rectifiers connected in series, the current-circulating circuit being connected in parallel to the half-bridge circuit;
• an auxiliary winding of a same polarity as the primary winding, the auxiliary winding having a first end connected to a line between the two rectifiers and a second end connected to the LLC resonant circuit;
• and
• a full-wave rectification circuit connected to the secondary windings and configured for generating an output voltage across an output capacitor;
• wherein when the power switches are switched, the auxiliary winding senses a voltage across a parasitic capacitance of the primary winding and activates the rectifiers of the current-circulating circuit separately, so as to guide a current through the resonant inductor and cause the current to circulate through the auxiliary winding, thereby preventing the voltage across the parasitic capacitance of the primary winding from exceeding a difference obtained by subtracting a voltage across the resonant capacitor from the input voltage or exceeding the voltage across the resonant capacitor.