Switching power supply device and battery charger including the same

A switching power supply device comprising:

• a full-bridge circuit comprising a first series connection which includes a first switching device and a second switching device and a second series connection which includes a third switching device and a fourth switching device;
• a transformer comprising a primary coil and a secondary coil, one end of the primary coil being connected between the first and second switching devices, and the other end of the primary coil being connected between the third and fourth switching devices;
• a rectifier circuit comprising a third series connection which includes a first diode and a third diode and a fourth series connection which includes a second diode and a fourth diode, the rectifier circuit being connected to the secondary coil to rectify a voltage outputted from the secondary coil;
• and
• a snubber circuit comprising a first snubber diode connected to an intermediate point of the secondary coil, a second snubber diode connected in series with the first snubber diode, the second snubber diode being connected to one end of an output capacitor, and a snubber capacitor connected between a node between the first and second snubber diodes and a positive side output of the rectifier circuit, wherein
• the first series connection, the second series connection, the third series connection and the fourth series connection are connected in parallel to each other,
• the first and third switching devices and the first and second diodes are paired to form an upper arm, and the second and fourth switching devices and the third and fourth diodes are paired to form a lower arm, and
• one end of the secondary coil is connected between the first and second diodes, and the other end of the secondary coil is connected to between the third and fourth diodes.

A battery charger comprising:

• a switching power supply device, wherein the switching power supply device comprises:
• a full-bridge circuit comprising a plurality of switching devices;
• a transformer comprising a primary coil and a secondary coil, the primary coil being connected to an output of the full-bridge circuit;
• a DC/DC converter comprising a plurality of diodes and a rectifier circuit, the rectifier circuit being connected to the secondary coil to rectify voltage outputted from the secondary coil;
• and
• a snubber circuit comprising a first snubber diode connected to an intermediate point of the secondary coil, a second snubber diode connected in series with the first snubber diode, the second snubber diode being connected to one end of an output capacitor, and a snubber capacitor connected between a node between the first and second snubber diodes and a positive side output of the rectifier circuit;
• and
• an AC/DC converter connected to an alternating power supply, wherein the AC/DC converter rectifies AC power into DC direct current power and supplies the rectified DC power to an input of the DC/DC converter.