Patent ID: 7304867

Claim:
A DC-DC converter of multi-output type comprising: first and second primary switching elements connected in series to a DC power source; a first rectifying smoother connected to a first secondary winding of a transformer; a primary control circuit for controlling on-off operation of said first and second primary switching elements based on output voltage from said first rectifying smoother; a second rectifying smoother connected to a second secondary winding of said transformer; a secondary switching element connected between said second secondary winding and a smoothing capacitor of said second rectifying smoother; a secondary control circuit for controlling on-off operation of said secondary switching element based on second output voltage from said smoothing capacitor; wherein on-off operation of said first and second primary switching elements generates first and second DC outputs which is taken respectively from said first and second secondary windings of the transformer through said first and second rectifying smoothers; said secondary switching element is turned on the moment the first or second primary switching element is turned on or when a predetermined period of time elapses after said first or second primary switching element is turned on; said first secondary winding, primary winding, and second secondary winding in the one outward order or said second secondary winding, primary winding, and first secondary winding in the other outward order are concentrically wound in around a core in a layered structure, and said first and second secondary windings of the transformer are in the electromagnetic sparse coupling, PWM control is performed by frequency modulation to control the on-period of the first or second primary switching element while the on-period of the second or first primary switching element is set.