Patent ID: 8724346

Claim:
A DC/DC converter, comprising: a transformer comprising a primary coil, a secondary coil, and an auxiliary coil which is disposed in a primary coil side, the auxiliary coil comprising: a first port configured to generate a first voltage which is obtained by multiplying a voltage generated in the secondary coil and a first coefficient; and a second port configured to generate a second voltage which is obtained by multiplying the voltage generated in the secondary coil and a second coefficient greater than the first coefficient; a first output capacitor including a first end and a second end, the first end of the first output capacitor having a fixed electric potential and the second end being connected to an output port of the DC/DC converter; a first diode disposed in a direction where a cathode of the first diode faces toward the first output capacitor, between the second end of the first output capacitor and one end of the secondary coil; a switching transistor disposed on a path of the primary coil; a second output capacitor including a first end and a second end, the first end of the second output capacitor having a fixed electric potential; a second rectification element disposed in a direction where a cathode of the second rectification element faces the second output capacitor, between the second end of the second output capacitor and the first port of the auxiliary coil; a third rectification element disposed in a direction where a cathode of the third rectification element faces toward the second output capacitor, between the second end of the second output capacitor and the second port of the auxiliary coil; a selection circuit configured to select a first path comprising the second rectification element in a first mode where an output voltage of the output port has a first level, and select a second path comprising the third rectification element in a second mode where the output voltage has a second level lower than the first level; and a control circuit configured to receive a voltage which is generated in the second output capacitor through a power supply port and control turn-on or turn-off of the switching transistor.