Patent ID: 8687390

Claim:
An active clamp DC-DC converter, comprising: a transformer having a primary coil and a secondary coil; a main switching device connected in series to the primary coil of the transformer, the main switching device and the primary coil being connected in parallel to a DC power source; a reset capacitor; a reset switching device connected in series to the reset capacitor, the reset switching device and the reset capacitor being connected in parallel to the primary coil of the transformer; a rectifying circuit connected to the secondary coil of the transformer; a smoothing circuit connected to the rectifying circuit; and a control circuit turning off the reset switching device while the main switching device is on, and turning on the reset switching device while the main switching device is off, the control circuit controlling duty of a drive signal for driving the main switching device thereby to keep an output DC voltage from the smoothing circuit constant, wherein the control circuit adjusts a dead time that elapses from the time when the reset switching device is turned off until the time when the main switching device is turned on, based on a voltage across the main switching device, wherein the control circuit calculates the voltage across the main switching device just before the reset switching device is turned off, by adding a voltage between one end of the secondary coil and ground of the secondary coil while the main switching device is on to a voltage between the other end of the secondary coil and the ground while the main switching device is off.