A DC-DC converter includes an ON-timing delay circuit in which, when an ON signal is output from a power switch driving circuit in a control IC to a power switch, the ON timing of the power switch is delayed by hindering the start of the ON operation of the power switch. An early turnoff circuit is provided in which, during delay of the ON timing of the power switch, a commutating synchronous rectifier has an ON and OFF switching operation that is inverse with respect to that of the power switch. A delay eliminating circuit is provided which promptly stops the delay operation of the ON-timing delay circuit when detecting the turnoff of the commutating synchronous rectifier which is caused by a drop in the gate of a commutating synchronous rectifier. When the delay operation of the ON-timing delay circuit continues after the turnoff the commutating synchronous rectifier, a loss caused by the continuation of the delay operation occurs. The problem can be prevented by the delay eliminating circuit.
A synchronous rectification circuit with dead time regulation being adapted for a forward power supply to regulate a dead time of a switch circuit is described. The synchronous rectification circuit has a first switch control circuit connected with a first switch to control ON/OFF of the first switch, a dead time regulation circuit connected with the first switch control circuit to produce a dead time regulation signal, and a second switch control circuit connected with a second switch and the dead time regulation circuit to control ON/OFF of the second switch.
A boost converter includes a first boost conversion unit and a second boost conversion unit. Coils of the first boost conversion unit and the second boost conversion unit are coupled with each other. Due to coupling of the coils, the second boost conversion unit releases energy while the first boost conversion unit stores energy in a period of time. Furthermore, due to coupling of the coils, the first boost conversion unit releases energy while the second boost conversion unit stores energy in another period of time. The two boost conversion units operate alternately, thereby adjusting switching loss and averaging output power of components. Furthermore, as switching frequency increases, the coil inductance, as well as the capacitance required in the two boost conversion units can be reduced correspondingly, thus substantially enhancing responses of the two boost conversion units as a whole.
