Patent ID: 6038144
Filing Date: 2000-03-14
Classification: H02M

Abstract:
A DC-DC converter comprising:a primary-side circuit performing LC resonance synchronously with ON/OFF operations performed by a switching device by using a DC input voltage for generating a primary-side pulse in a period when the switching device is OFF to output energy to a secondary side, the switching device having two main terminals for switching a switched current, an application voltage being applied to one of said main terminals thereof and a pulse control signal being applied to a control terminal thereof;an oscillation circuit outputting the pulse-control signal that controls the ON/OFF operations of the switching device, wherein variable control is performed for an ON period of the pulse-control signal outputted from said oscillation circuit to stabilize current and voltage outputted from the secondary side, said oscillation circuit comprising a multivibrator having at least two logical elements; anda zero-voltage switching control circuit that detects reduction of the primary-side pulse-control signal to be applied to the switching device in a period when the switching device is OFF and after detecting the application voltage for the switching device from an OFF-period voltage level which is higher than the level of the input voltage to an input voltage region, reverses a level of the pulse-control signal outputted from the multivibrator to a higher level in order to turn ON the switching device.