Abstract: A switching power-supply device, includes a first terminal; a first winding connected to the first terminal; a second winding, which is connected in series to the first winding and is magnetically coupled to the first winding; a first capacitor connected in series to the second winding; a transformer including a primary winding connected in series to the first capacitor and a secondary winding magnetically coupled to the primary winding; a rectifying-and-smoothing circuit connected to the secondary winding; a second terminal, which is connected to an opposite end of the primary winding opposite to a connection end connecting to the first capacitor; a first switching element, which is connected between a connection point of the first winding and the second winding and the second terminal; and a control circuit, which controls first switching element to turn on-and-off.

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 bridge-less step-up switching power supply device includes (i) a first and a second reactor having: a first and a second main winding connected to a first and a second input terminal, respectively; and a first and a second auxiliary winding magnetically coupled to the first main winding and connected to the first and second main windings, the first and second auxiliary windings having a first and a second leakage inductance, respectively; (ii) a first and a second diode connected between the first and second auxiliary windings and a first output terminal, respectively; (iii) a first capacitor connected between the first output terminal and a second output terminal; (iv) a second capacitor connected between a connection point of a third switch and a fourth switch, and the first output terminal; and (v) a controller for controlling turning on/off of first to fourth switches.

Abstract: A switching power-supply device, includes a first terminal; a first winding connected to the first terminal; a second winding, which is connected in series to the first winding and is magnetically coupled to the first winding; a first capacitor connected in series to the second winding; a transformer including a primary winding connected in series to the first capacitor and a secondary winding magnetically coupled to the primary winding; a rectifying-and-smoothing circuit connected to the secondary winding; a second terminal, which is connected to an opposite end of the primary winding opposite to a connection end connecting to the first capacitor; a first switching element, which is connected between a connection point of the first winding and the second winding and the second terminal; and a control circuit, which controls first switching element to turn on-and-off.

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 switching power source apparatus includes a first arm including first and second switching elements, a second arm including third and fourth switching elements, a series circuit connected between a connection point of the first and second switching elements and a connection point of the third and fourth switching elements and including a capacitor and a primary winding, a rectifying-smoothing circuit that rectifies and smoothes a voltage of a secondary winding and provides an output voltage, a reactor connected to a connection point of the first and second switching elements and a DC input end, and a controller that turns on/off the first and second switching elements alternately and the third and fourth switching elements alternately and synchronizes the first and third switching elements with each other and the second and fourth switching elements with each other.

Abstract: A bridge-less step-up switching power supply device includes (i) a first and a second reactor having: a first and a second main winding connected to a first and a second input terminal, respectively; and a first and a second auxiliary winding magnetically coupled to the first main winding and connected to the first and second main windings, the first and second auxiliary windings having a first and a second leakage inductance, respectively; (ii) a first and a second diode connected between the first and second auxiliary windings and a first output terminal, respectively; (iii) a first capacitor connected between the first output terminal and a second output terminal; (iv) a second capacitor connected between a connection point of a third switch and a fourth switch, and the first output terminal; and (v) a controller for controlling turning on/off of first to fourth switches.

Abstract: A gate driver of a switching element Q1 includes transistors Q2 and Q3 that are totem-pole-connected to both ends of a DC power source Vcc1, transistors Q4 and Q5 that are totem-pole-connected to both ends of a DC power source Vcc2 and have emitters connected to the gate of the switching element Q1, and a transformer T1 having a primary winding and a secondary winding. The primary winding is connected to a collector of one of the transistors Q1 and Q2, and through a capacitor, emitters of the transistors Q1 and Q2. The second winding is connected to bases of the transistors Q4 and Q5 and the emitters of the transistors Q4 and Q5. A maximum duty cycle of a pulse signal is determined according to a primary winding voltage of the transformer and a forward base-emitter voltage of the transistors Q4 and Q5.

Abstract: A power factor correction circuit includes reactors L1 and L2 to accumulate energy of an AC power source and discharge the accumulated energy, a hybrid bridge switch having two diodes D1 and D2 and two switching elements Q1 and Q2 to switch the energy accumulation and energy discharge of the reactors from one to another, a controller 3 to conduct ON-control of the two switching elements according to currents passing through the reactors and OFF-control of the two switching elements according to currents passing through the two switching elements, and a mode changer 11 to change an operation mode of the power factor correction circuit between a discontinuous mode and a critical mode according to a voltage of the AC power source.

Abstract: A switching power source circuit includes a first reactor having coils L1-1 and L1-2 connected in series, a second reactor connected in series with the first reactor, a series circuit connected with a DC power source and including the first reactor, the second reactor, a capacitor C1, a diode D1, and an output capacitor, a switching element Q1 connected between a connection point of the coils and the DC power source, a series circuit including a switching element Q2 and a capacitor C2 and connected to a connection point of the coils and to a connection point of the capacitor C1 and diode D1, a reactor L2 connected between a connection point of the capacitor C1 and diode D1 and the DC power source, and a controller controlling ON/OFF of the switching element Q2 so that the switching element Q1 carries out zero-volt switching when turned on.

Abstract: A gate driver of a switching element Q1 includes transistors Q2 and Q3 that are totem-pole-connected to both ends of a DC power source Vcc1, transistors Q4 and Q5 that are totem-pole-connected to both ends of a DC power source Vcc2 and have emitters connected to the gate of the switching element Q1, and a transformer T1 having a primary winding and a secondary winding. The primary winding is connected to a collector of one of the transistors Q1 and Q2, and through a capacitor, emitters of the transistors Q1 and Q2. The second winding is connected to bases of the transistors Q4 and Q5 and the emitters of the transistors Q4 and Q5. A maximum duty cycle of a pulse signal is determined according to a primary winding voltage of the transformer and a forward base-emitter voltage of the transistors Q4 and Q5.

Abstract: A switching power source apparatus includes a first arm including first and second switching elements, a second arm including third and fourth switching elements, a series circuit connected between a connection point of the first and second switching elements and a connection point of the third and fourth switching elements and including a capacitor and a primary winding, a rectifying-smoothing circuit that rectifies and smoothes a voltage of a secondary winding and provides an output voltage, a reactor connected to a connection point of the first and second switching elements and a DC input end, and a controller that turns on/off the first and second switching elements alternately and the third and fourth switching elements alternately and synchronizes the first and third switching elements with each other and the second and fourth switching elements with each other.

Abstract: The present invention includes: a first series circuit which is connected between one end and the other end of a DC power supply, and in which a reactor, a first diode, and a first capacitor are connected in series; a first switching element connected between the one end of the DC power supply and a connection point between the reactor and the first diode; a second series circuit which is connected to the first diode in parallel, and in which a second switching element and a second capacitor are connected in series; and a control circuit configured to control the on and off of the second switching element in order that turn on of the first switching element becomes to zero-voltage switching.

Abstract: A DC conversion apparatus includes a plurality of current resonant converters. Each of the current resonant converters has two switching elements connected in series, a transformer having primary and secondary windings, a series resonant circuit including a resonant reactor, the primary winding of the transformer, and a resonant capacitor, and a rectifying circuit to rectify a voltage generated by the secondary winding of the transformer. The DC conversion apparatus also includes a smoothing circuit having a reactor L3 and a smoothing capacitor C and arranged after connection points to which output terminals of the rectifying circuits of the plurality of current resonant converters are commonly connected. The DC conversion apparatus further includes a controller to control, according to an output voltage from the smoothing circuit, ON/OFF of the two switching elements of each of the plurality of current resonant converters.

Abstract: A power factor correction circuit includes reactors L1 and L2 to accumulate energy of an AC power source and discharge the accumulated energy, a hybrid bridge switch having two diodes D1 and D2 and two switching elements Q1 and Q2 to switch the energy accumulation and energy discharge of the reactors from one to another, a controller 3 to conduct ON-control of the two switching elements according to currents passing through the reactors and OFF-control of the two switching elements according to currents passing through the two switching elements, and a mode changer 11 to change an operation mode of the power factor correction circuit between a discontinuous mode and a critical mode according to a voltage of the AC power source.