Patent ID: 7336060

Claim:
A DC-DC converter comprising: a main switching transistor for receiving an input voltage; a synchronous rectification transistor connected in series to the main switching transistor; a choke coil connected to a node between the main switching transistor and the synchronous rectification transistor, with output voltage of the DC-DC converter generated at an output node of the DC-DC converter based on the input voltage by activating the main switching transistor and the synchronous rectification transistor in a complementary manner; a smoothing capacitor having a first terminal connected to the choke coil and a second terminal connected to a predetermined voltage, for smoothing the output voltage; and a control circuit, connected to the main switching transistor and the synchronous rectification transistor, for determining whether the input voltage decreases below a threshold and for inactivating the main switching transistor and activating the synchronous rectification transistor when the control circuit detects that the input voltage decreases below the threshold.