Patent ID: 6985369

Claim:
A DC-DC converter comprising: a primary-side circuit for outputting energy of a primary coil of a transformer to a secondary coil side in accordance with an on/off operation of a switching element; a secondary-side circuit for rectifying and smoothing a voltage output from the secondary coil of said transformer and for outputting a DC voltage; an auxiliary power-supply circuit for rectifying and smoothing the voltage output from an auxiliary power-supply coil provided in said transformer; a secondary-side control circuit for detecting the DC output voltage of said secondary-side circuit and for outputting a control signal; a drive control circuit for outputting a pulse control signal for controlling the on/off operation of said switching element on the basis of the control signal output from said secondary-side control circuit; an insulator for transmitting the control signal output from said secondary-side control circuit to said drive control circuit; and a coupling device for superimposing, in an AC manner, the output of said auxiliary power-supply circuit onto the control signal transmitted to said drive control circuit; wherein the output of said auxiliary power-supply circuit and said coupling device are directly connected to each other electrically.