Abstract: Provided is a switching power supply device capable of easily realizing multi-phase operation and current balancing with the number of operation phases depending on the amount of load.

Abstract: Provided is a switching power supply device capable of easily realizing multi-phase operation and current balancing with the number of operation phases depending on the amount of load.

Abstract: Provided is a synchronous rectifier circuit which, even if a synchronous rectification element having a low on-resistance is used, can perform a synchronous rectifying operation without being influenced by the inductance component. It is a synchronous rectifier circuit having a synchronous rectification element QSR1 and a synchronous rectification control circuit IC1 for turning on/off the synchronous rectification element QSR1 in accordance with the current iSR flowing through the synchronous rectification element QSR1, including a current detection circuit for detecting the current iSR flowing through the synchronous rectification element QSR1 during an on-period of the synchronous rectification element QSR1 as a synchronized voltage waveform, the synchronous rectification control circuit IC1 being configured so as to turn off the synchronous rectification element QSR1 on the basis of the voltage waveform detected by the current detection circuit 1a.

Abstract: Provided is a current detection circuit which can reduce the resistance loss for a current transformer, meeting the requirements for size and cost thereof. The current detection circuit includes a current transformer and a capacitor connected across a secondary winding of the current transformer, the capacitor making a phase adjustment such that the primary side current flowing through the primary winding of the current transformer and the voltage across the capacitor are in phase with each other. With this configuration, the primary side current can be detected as the voltage across the capacitor with no need for using a matching resistor, with which, if the winding ratio of the current transformer is small, the resistance loss will be large, whereby a current detection circuit of low loss using a current transformer which is small in size and low in cost can be configured.

Abstract: Provided is a synchronous rectifier circuit which, even if a synchronous rectification element having a low on-resistance is used, can perform a synchronous rectifying operation without being influenced by the inductance component. It is a synchronous rectifier circuit having a synchronous rectification element QSR1 and a synchronous rectification control circuit IC1 for turning on/off the synchronous rectification element QSR1 in accordance with the current iSR flowing through the synchronous rectification element QSR1, including a current detection circuit for detecting the current iSR flowing through the synchronous rectification element QSR1 during an on-period of the synchronous rectification element QSR1 as a synchronized voltage waveform, the synchronous rectification control circuit IC1 being configured so as to turn off the synchronous rectification element QSR1 on the basis of the voltage waveform detected by the current detection circuit 1a.

Abstract: A resonant converter includes: a first switching element and a second switching element, which are connected in series; a series resonant circuit, which includes a primary coil of a transformer having leakage inductance and a current resonant capacitor, and which is connected in parallel to one of the first switching element and the second switching element; a rectifying-and-smoothing circuit, which is connected to a secondary coil of the transformer, wherein an output voltage is to be supplied to a load; and a clamp circuit, which clamps a voltage between both ends of the current resonant capacitor to a predetermined voltage value, wherein, when an output current supplied from the rectifying-and-smoothing circuit to the load is higher than the predetermined current value, an output characteristic is set so that, as the output current is increased, the output voltage is decreased.

Abstract: A current balancing apparatus includes a power supply unit 10 to output an alternating current and a plurality of series circuits connected to an output of the power supply unit. Each of the series circuits has at least one winding N1 (S1) and a voltage multiplier rectifier having rectifiers D1 and D11 (D2 and D12) and capacitors C1 and C11 (C2 and C12). Outputs of the voltage multiplier rectifiers are connected to loads LD1 and LD2, respectively. Each of the loads has loads LED1a to LED1e (LED2a to LED2e). Currents passing through the loads are balanced by electromagnetic force occurring on the at least one winding.