AC/DC converter extracting a forward voltage and a flyback voltage from the secondary winding

An AC-DC converter comprising:

• a primary winding to which an alternating-current input voltage is applied;
• a secondary winding which is magnetically coupled with the primary winding;
• a bidirectional switch which is connected in series with the primary winding;
• a resonance capacitor which is connected in parallel with at least one of the bidirectional switch and the primary winding;
• a resonance inductance component;
• a full-wave rectification circuit which performs full-wave rectification on an induced voltage that appears in the secondary winding;
• and
• a smoothing capacitor which smoothes an output of the full-wave rectification circuit,
• wherein
• the AC-DC converter converts the alternating-current input voltage directly into a direct-current output voltage by extracting both a forward voltage and a flyback voltage from the secondary winding,
• the AC-DC converter further comprises a switch which switches either a number of turns of the primary winding or both the number of turns of the primary winding and a capacitance value of the resonance capacitor,
• the primary winding includes a first primary winding and a second primary winding, and
• the bidirectional switch is connected in series between the first and second primary windings.