DC-DC converter

摘要

A DC-DC converter comprises: a primary side circuit (3) for allowing a switching device (Q) to perform on/off operations to output energy in a primary coil (N1) of a transformer (1) to a secondary coil (N2); a secondary side circuit (5) for rectifying and smoothing a voltage outputted from the secondary coil (N2) so as to output a DC-DC voltage; a voltage-detecting circuit (8) rectifying and smoothing a voltage outputted from a voltage-detecting coil (N3) provided in the transformer (1) so as to output the voltage as a detected voltage corresponding to a voltage to be outputted from the secondary side circuit (5); a control circuit (10) for applying to the switching device (Q) a pulse control signal used for controlling on/off operation of the switching device (Q) according to the voltage outputted from the voltage-detecting circuit (8); and a primary side current-detecting circuit (12) for converting a working current in the primary side circuit (3), the working current corresponding to a current in the secondary side circuit (5), for performing detection thereof, and for superposing the thus detected voltage corresponding to the working current with the detected voltage outputted from the voltage-detecting circuit (8) so as to compensate for an amount of variation of an output voltage of the secondary side circuit (5), the variation being attributed to a variation of the working current in the secondary side circuit (5), and for applying a voltage according to the superposed voltage to the control circuit (10).