Patent ID: 7660134

Claim:
A DC-DC converter, comprising: a third switching element connected between a terminal to which a third potential is applied and a second intermediate terminal; a fourth switching element connected between said second intermediate terminal and a terminal to which a fourth potential is applied; a fifth switching element connected between said terminal to which the third potential is applied and a third intermediate terminal; a sixth switching element connected between said third intermediate terminal and said terminal to which the fourth potential is applied; a transformer having a primary winding whose terminals are connected to said second intermediate terminal and said third intermediate terminal respectively; a seventh switching element connected between a first terminal of a secondary winding of said transformer and a terminal to which a fifth potential is applied; an eighth switching element connected between a second terminal of said secondary winding of said transformer and said terminal to which the fifth potential is applied; a second inductance element connected between a tap of said secondary winding of said transformer and an output terminal; a second capacitor connected between said output terminal and said terminal to which the fifth potential is applied; a PWM control circuit which detects a voltage of said output terminal, and outputs a pulses signal having a pulse width determined based on the voltage of said output terminal; a second driver circuit which drives said third to eighth switching elements based on the pulse signal; a second pulse skipping detecting circuit which switches off said seventh and eighth switching elements, when detecting that said PWM control circuit has stopped outputting the pulse signal for a predetermined period or longer; and a second light load detecting circuit which switches off said seventh and eighth switching elements, when detecting that a current flowing in said second inductance element becomes equal to or smaller than a predetermined current value, wherein before said second light load detecting circuit switches off said seventh and eighth switching elements, said second pulse skipping detecting circuit switches off said seventh and eighth switching elements.