Switching power converting apparatus

A switching power converting apparatus comprising:

• a transformer including a first primary winding, a second primary winding, and a secondary winding, each of said first and second primary windings and said secondary winding having a dot-marked terminal and a non-dot terminal;
• a secondary side control module including
• an output capacitor for providing an output voltage thereacross,
• a rectification switch unit coupled between said secondary winding of said transformer and said output capacitor, said rectification switch unit being operable in one of an OFF state, where said rectification switch unit permits current flow through said secondary winding of said transformer from said dot-marked terminal to said non-dot terminal, and an ON state, where said rectification switch unit permits current flow through said secondary winding of said transformer from said non-dot terminal to said dot-marked terminal,
• a zero current detecting unit coupled to said secondary winding of said transformer for detecting a current flowing through said secondary winding of said transformer so as to output a zero-current indication signal upon detecting that the current becomes zero, and
• a first control unit coupled to said output capacitor, said rectification switch unit, and said zero current detecting unit, configured to receive the zero current indication signal from said zero current detecting unit, and configured to detect the output voltage across said output capacitor, said first control unit being operable to enable said rectification switch unit to operate in the ON state for a predetermined time period upon detecting that the output voltage is less than a predetermined target voltage and upon receipt of the zero current indication signal from said zero current detecting unit;
• and
• a primary side control module including
• a second control unit coupled to said second primary winding of said transformer, and configured to detect a potential at said non-dot terminal of said second primary winding of said transformer and a current flowing through said first primary winding of said transformer, and
• a switching unit coupled to said non-dot terminal of said first primary winding of said transformer and said second control unit, and being operable in one of an ON state and an OFF state in response to a control voltage from said second control unit;
• wherein said second control unit of said primary side control module is operable to
• enable said switching unit to operate in the ON state upon detecting, based on the potential at said non-dot terminal of said second primary winding, one of a condition that the output voltage is less than a predetermined start voltage and the current flowing through said secondary winding of said transformer becomes zero, and a condition that the output voltage is greater than the predetermined start voltage and less than the predetermined target voltage, and
• enable said switching unit to operate in the OFF state upon detecting that the current flowing through said first primary winding of said transformer is greater than a predetermined target current.