Patent ID: 7075801

Claim:
A direct-current converter which alternately switches on/off a main switch and an auxiliary switch, thereby rectifying and smoothing a voltage of a secondary winding of a transformer, thus obtaining a direct-current output, the main switch being connected in series to a primary winding of the transformer, and the auxiliary switch being of a series circuit connected to both ends of the primary winding of the transformer or both ends of the main switch and composed of a capacitor and the auxiliary switch, comprising: bottom detection means configured to detect a minimum voltage of the main switch after the auxiliary switch is switched off; control signal generation means configured to generate an ideal control signal which switches on the main switch at a time of the minimum voltage of the main switch based on an output of the bottom detection means; error calculation means configured to calculate an error output between the ideal control signal generated by the control signal generation means and an actual control signal which switches on the main switch; and delay control means configured to control a delay of an ON time of the main switch by the actual control signal based on the error output of the error calculation means, thereby performing control to make the actual control signal approach the ideal control signal.