Patent ID: 7006363

Claim:
A DC-DC converter circuit comprising: a transformer having a primary winding and a secondary winding, wherein a primary side including the primary winding and a secondary side including the secondary winding are insulated from each other in the DC-DC converter circuit; a switching circuit including a main switching element which is connected to the primary winding in series and has a control terminal for controlling the main switching element, wherein the main switching element is PWM-controlled so as to stabilize an output voltage of the secondary side; a driving circuit for generating a PWM driving pulse signal; and a correction circuit including a resistor and a capacitor which are connected in series, wherein an output of the driving circuit is connected to the control terminal of the main switching element and to the resistor of the correction circuit, the capacitor of the correction circuit is alternately charged and discharged via the resistor in accordance with alternation of an on-state and an off-state of the PWM driving pulse signal, so that an output voltage of the correction circuit has a waveform close to an average of the PWM driving pulse signal, and a period of time of the on-state of the PWM driving pulse signal is in inverse proportion to an input voltage of the DC-DC converter circuit, and the average of the PWM driving pulse signal is in proportion to the period of time of the on-state, so that the correction circuit outputs a voltage whose level is in inverse proportion to the input voltage.