Patent ID: 7522429

Claim:
A DC-DC converter comprising: a DC power supply; a first switching device; a transformer further comprising a primary coil and a secondary coil, the primary coil being connected in series to the first switching device, the series connection of the primary coil and the first switching device being connected in parallel to the DC power supply; a capacitor; a second switching device being connected in series to the capacitor, the series connection of the second switching device and the capacitor being connected to both sides of the primary coil; a rectifying and smoothing circuit being connected to both sides of the secondary coil, the rectifying and smoothing circuit generating a DC output; a first control circuit connected to the first switching device, the first control circuit being configured to control the first switching device, the first control circuit being configured to control an ON-time of the first switching device; and a second control circuit connected to the second switching device, the second control circuit being configured to control the second switching device while the second control circuit being decoupled from the first control circuit, the first and second control circuits being configured to cause the first and second switching devices to alternately turn ON and OFF, the second control circuit being configured to cause the second switching device to turn ON synchronizing with a first time period between after a charge to the capacitor is started and until the charge to the capacitor is ended, the second control circuit being configured to cause the second switching device to turn OFF when a second time period previously set has been elapsed after the second switching device turned ON.