Abstract: A PFC (Power Factor Correction) circuit improves the power factor of rectified power. Upon receiving output of the PFC circuit, a first DC-DC converter generates a voltage to be supplied to a load. Upon receiving output of the PFC circuit, a second DC-DC converter and a third DC-DC converter generate a control voltage. The second DC-DC converter and the third DC-DC converter are cascade-connected. An input terminal of the third DC-DC converter is connected to both an output terminal of the second DC-DC converter and an output terminal of the first DC-DC converter.

Abstract: In a full bridge type DC-DC converter, a first protective diode is connected between a first node between a first resonance inductor on a primary side and one terminal of a primary winding of a transformer, and a power line on a high voltage side of a power supply. A second protective diode is connected between the first node and a power line on a low voltage side of the power supply. A third protective diode is connected between a second node between a second resonance inductor and the other terminal of the primary winding, and the power line on the high voltage side of the power supply. A fourth protective diode is connected between the second node and the power line on the low voltage side of the power supply.

Abstract: A PFC (Power Factor Correction) circuit improves the power factor of rectified power. Upon receiving output of the PFC circuit, a first DC-DC converter generates a voltage to be supplied to a load. Upon receiving output of the PFC circuit, a second DC-DC converter and a third DC-DC converter generate a control voltage. The second DC-DC converter and the third DC-DC converter are cascade-connected. An input terminal of the third DC-DC converter is connected to both an output terminal of the second DC-DC converter and an output terminal of the first DC-DC converter.

Abstract: There is disclosed a current balancing circuit for use in a switching power supply unit that operates in parallel with one or more other switching power supply units with current balancing terminals connected to each other. The current balancing circuit comprises a first resistor that receives a detection signal of the output current input via a diode and outputs an output current detection voltage; a second resistor connected between the current balancing terminal and a connection point between the first resistor and the diode; an operational amplifier that outputs a signal corresponding to the different between the output current detection voltages; and a switching circuit.

Abstract: There is disclosed a current balancing circuit for use in a switching power supply unit that operates in parallel with one or more other switching power supply units with current balancing terminals connected to each other. The current balancing circuit comprises a first resistor that receives a detection signal of the output current input via a diode and outputs an output current detection voltage; a second resistor connected between the current balancing terminal and a connection point between the first resistor and the diode; an operational amplifier that outputs a signal corresponding to the different between the output current detection voltages; and a switching circuit.

Abstract: A synchronous rectifying type DC-DC converter including an auxiliary winding, provided on a secondary side of a transformer, for supplying voltages assuming polarities opposite to each other to control terminals of a rectifying switch and of a fly wheel switch, and the rectifying switch and the fly wheel switch are so constructed as not to be turned ON/OFF by a voltage generated on a supply path of an electric current to a load from a secondary winding of the transformer. When connecting a plurality of DC-DC converters in parallel and operating these converters in parallel, an output of any one of the converters stops, and, even if outputs of the other DC-DC converters are inputted to the DC-DC converter concerned and the electric current flows into the current supply path, a voltage based on the above current is not applied to control terminals of the rectifying switch and of the fly wheel switch. The rectifying switch and the fly wheel switch are not therefore turned ON.

Abstract: A DC--DC converter unit includes a power conversion transformer, a switching device for switching a DC voltage supplied to a primary winding of the power conversion transformer, a rectifying circuit for synchronously rectifying a AC voltage generated on a secondary winding of the power conversion transformer so that a DC voltage is obtained, and a reset circuit for resetting excitation energy which has been stored in the power conversion transformer by an on-operation of the switching device, so that the voltage which is switched has a square waveform.

Abstract: Disclosed is a synchronous rectifier type DC-to-DC converter capable of preventing an increase in losses occurring when a rectifier synchronous rectification switch and a flywheel synchronous rectification switch, which are responsible for rectification on the side of a secondary winding of a transformer, are turned on simultaneously, and the destruction of FETs or windings due to large currents. The DC-to-DC converter comprises a transformer, a primary switching device connected in series with a primary winding of the transformer, a control circuit for controlling turning on or off of the primary switching device, a rectifier synchronous rectification switching device, and a flywheel synchronous rectification switching device, and converts a voltage of a DC power source into another voltage.