The invention relates to a DC-DC power supply conversion device, in particular to a zero-
voltage switch (ZVS) flyback-type DC-DC power supply conversion device with efficient conversion, efficient light-load conversion and low
standby power consumption. An auxiliary switch and an absorption
capacitor are additionally arranged on the flyback circuit; the auxiliary switch and the absorption
capacitor are connected in series so as to form an auxiliary
branch circuit; the auxiliary
branch circuit can be connected in parallel to the two ends of the primary winding of a
transformer or alternatively connected in parallel to the two ends of a primary-side switch; and the auxiliary switch is conductive for a determined period of time before the primary-side switch is conductive. Compared with the prior art, the energy of the circuit leakage
inductor can be absorbed and transferred to the output terminal and a
soft switch for realizing the primary-side switch, so that the invention can greatly improve the circuit efficiency; the
parasitic oscillation caused by the leakage
inductor can be suppressed, so that the EMI (
electromagnetic interference) characteristics of the circuit can be improved; and the circuit can be controlled more easily, thereby improving the light-
load circuit efficiency and reducing the idle-load
energy loss.