Resonant-type switching power supply device

A resonant-type switching power supply device comprising:

• a first half-wave rectifying circuit being provided with a first switching element and a second switching element both being connected in series to each other and both being connected to a direct current power source, with a first serial resonance circuit being connected to the first switching element or the second switching element and being constituted of a primary winding of a first transformer and a first resonance capacitor connected serially to the first winding, and with a first rectifying element connected to a secondary winding of the first transformer;
• a second half-wave rectifying circuit being provided with a third switching element and a fourth switching element both being connected to the direct current power source and both being connected in series to each other, with a second serial resonance circuit being connected to the third switching element or the fourth switching element and being constituted of a primary winding of a second transformer and a second resonance capacitor connected to the primary winding, and with a second rectifying element connected to the secondary winding of the second transformer;
• a smoothing capacitor being connected commonly to the first rectifying element and second rectifying element and being charged with power energy supplied by the first and second rectifying elements to output a direct current output voltage;
• and
• a control circuit including a voltage comparing unit to calculate a difference between a charging voltage of the first resonance capacitor and a charging voltage of the second resonance capacitor;
• wherein the first switching element and the second switching element are alternately turned on or off according to the direct current output voltage and the third and fourth switching elements are alternately turned on or off according to the direct current output voltage and the difference calculated by the voltage comparing unit.