Patent ID: 8411466

Claim:
A DC-to-DC converter comprising: a plurality of switching elements connected together in series and connected between two ends of a DC power supply; a first control circuit configured to alternately turn on and off the plurality of switching elements in response to a constant oscillation frequency signal; a series circuit in which a primary winding of a transformer and a capacitor are connected together in series, the series circuit being connected to a connecting point between the plurality of switching elements, and to an end of the DC power supply; a rectifying/smoothing circuit configured to rectify and smooth a voltage which occurs in a secondary winding of the transformer, thus to output a DC voltage; a full wave rectifier connected to two ends of either the primary or the secondary winding of the transformer, includes a first rectifying element and a second rectifying element; a control switching element connected to two ends of either the primary or the secondary winding of the transformer through the full wave rectifier, short-circuits two ends of either the primary or the secondary winding of the transformer; and a second control circuit configured to control the DC voltage at a predetermined voltage by turning on and off the control switching element, wherein the secondary winding of the transformer includes a first winding and a second winding, a first series circuit including the first rectifying element and the control switching element is connected to two ends of the first winding, a second series circuit including the second rectifying element and the control switching element is connected to two ends of the second winding, and the second control circuit controls the DC voltage at the predetermined voltage by turning on and off the control switching element based on a voltage of the first winding, a voltage of the second winding, and the DC voltage, wherein an anode of the first rectifying element is connected to one end of the first winding, a cathode of the first rectifying element is connected to one end of the control switching element, an anode of the second rectifying element is connected to one end of the second winding, a cathode of the second rectifying element is connected to the one end of the control switching element, and other end of the control switching element is connected to a connection point of the first winding and the second winding.