Abstract: A transformer includes a magnetic core, a first coupling terminal, a second coupling terminal, a first winding, and one or multiple second windings. The magnetic core includes two opposed base parts, and five leg parts including first to fifth leg parts disposed within opposed surfaces of the base parts and magnetically coupling the base parts. The second and third leg parts are disposed with the first leg part interposed therebetween in a first direction. The fourth and fifth leg parts are disposed with the first leg part interposed therebetween in a second direction. The first winding is, in a direction from the first coupling terminal to the second coupling terminal, wound around the first to third leg parts in a first winding direction, and around the fourth and fifth leg parts in a second winding direction. The second winding/windings is/are wound around the leg parts except the first leg part.

Abstract: The switching power supply device includes an AC voltage input unit, a filter, a first inductor, a switching unit, a first rectification unit that includes first and second rectifier elements, in which the first and second rectifier elements are connected in series, in which a second output terminal of the AV voltage input unit is electrically connected to a transmission line, which connects the first and second rectifier elements, via the filter, and that is connected in parallel to the switching unit, a first capacitor, an inverter, a second rectification unit that includes an input terminal which is connected to a secondary coil, a smoothing unit that is connected between the output terminals of the second rectification unit, a control unit, a second capacitor that is connected between a transmission line, which connects the first and second rectifier element, and the smoothing unit, and a twentieth capacitor.

Abstract: A FET driving circuit includes: inputs into which a DC voltage is inputted; outputs connected to gate and source electrodes of a FET; a switch; a capacitance connected across the switch; and an LC resonance circuit connected in series with the switch across the inputs. A voltage generated across the switch during switching is outputted to drive the FET. The LC resonance circuit has a first connector connected to one input and a second connector connected to the switch, and is configured with a path including an inductance and a path including an inductance and a capacitance. An impedance between the first and second connectors has two resonant frequencies. The impedance has a local maximum at the lower resonant frequency, which is higher than a switching frequency, and a local minimum at the higher resonant frequency, which is around double the switching frequency.

Abstract: The switching power supply device includes an AC voltage input unit, a filter, a first inductor, a switching unit, a first rectification unit that includes first and second rectifier elements, in which the first and second rectifier elements are connected in series, in which a second output terminal of the AV voltage input unit is electrically connected to a transmission line, which connects the first and second rectifier elements, via the filter, and that is connected in parallel to the switching unit, a first capacitor, an inverter, a second rectification unit that includes an input terminal which is connected to a secondary coil, a smoothing unit that is connected between the output terminals of the second rectification unit, a control unit, a second capacitor that is connected between a transmission line, which connects the first and second rectifier element, and the smoothing unit, and a twentieth capacitor.

Abstract: A zero current detection circuit includes: one detection winding that is magnetically coupled to a boost inductor of a bridgeless totem pole PFC for converting an AC input voltage to a DC output voltage, has one end connected to ground, and generates a zero current detection signal, which changes in proportion to a boost inductor voltage, at another end; a resistor with one end connected to the other end of the detection winding; a clamp composed of two diodes connected to each other in series with a same forward direction, which clamps the inputted zero current detection signal to the ground potential and a positive power supply voltage to convert to a rectangular signal; and a pulse outputter with a comparator which compares the rectangular signal and a comparison voltage and outputs detection pulses with falling edges that are synchronized with an inductor current reaching zero.

Abstract: A switching power supply includes a power converter with an inductor and first and second switches that converts a voltage Vac to a voltage Vdc, a detector with a winding that detects zero timing of an inductor current, and a driving signal generator that switches on the second switch based on the zero timing and then switches on the first switch. The driving signal generator ends a period T2 before the zero timing by executing a measuring process for an on period T1 of the second switch, a process that calculates the period T2 from T2=T1×|Vac|/(Vdc?|Vac|)?Tc using a correction time Tc, a process that switches on the first switch for only the period T2, a process that measures an elapsed time between the periods T2 and T1, and a process that changes the correction time Tc so that the elapsed time becomes a target time.

Abstract: A power converter includes: two DC input terminals that input a DC input voltage; two DC output terminals that output a DC output voltage; an isolation transformer with a primary winding and a secondary winding; a switch that is connected across the two DC input terminals in a state where the switch is connected in series to the primary winding and that switches the DC input voltage; an LC resonance circuit that includes an inductance and a capacitance and is connected in parallel to the primary winding; a first resonant capacitance that is connected in parallel to the switch; a second resonant capacitance that is connected in parallel to the secondary winding; and a rectifying and smoothing circuit that rectifies and smoothes a voltage generated across both ends of the second resonant capacitance and outputs as the DC output voltage across the two DC output terminals.

Abstract: A FET driving circuit includes: two inputs for inputting a DC voltage; two outputs respectively connected to gate and source electrodes of a FET; a switch; a resonant capacitance connected between both ends of the switch; and an LC resonance circuit connected between the inputs and both ends of the switch. When the two inputs are shorted, frequency characteristics of an impedance of the LC resonance circuit include, in order from a low to a high-frequency side, first to fourth resonant frequencies. The first resonant frequency is higher than a switching frequency of the switch, the second resonant frequency is around double the switching frequency, the fourth resonant frequency is around four times the switching frequency, and the impedance has local maxima at the first resonant frequency and the third resonant frequency and local minima at the second resonant frequency and the fourth resonant frequency.

Abstract: A switching power supply device generates a DC output voltage, which is to be outputted to a load and is based on a DC input voltage. The switching power supply device includes n converter units and a control unit. The DC output voltage is compared with a voltage range selected out of a first voltage range and a second voltage range set in advance and the control unit executes one of first driving control to fourth driving control depending on the present driving control and the comparison result for the DC output voltage. By switching between the first to fourth driving control, the control unit changes the number of converter units to be driven.

Abstract: A switching power supply includes a power converter with an inductor and first and second switches that converts a voltage Vac to a voltage Vdc, a detector with a winding that detects zero timing of an inductor current, and a driving signal generator that switches on the second switch based on the zero timing and then switches on the first switch. The driving signal generator ends a period T2 before the zero timing by executing a measuring process for an on period T1 of the second switch, a process that calculates the period T2 from T2=T1×|Vac|/(Vdc?|Vac|)?Tc using a correction time Tc, a process that switches on the first switch for only the period T2, a process that measures an elapsed time between the periods T2 and T1, and a process that changes the correction time Tc so that the elapsed time becomes a target time.

Abstract: A zero current detection circuit includes: one detection winding that is magnetically coupled to a boost inductor of a bridgeless totem pole DEC for converting an AC input voltage to a DC output voltage, has one end connected to ground, and generates a zero current detection signal, which changes in proportion to a boost inductor voltage, at another end; a resistor with one end connected to the other end of the detection winding; a clamp composed of two diodes connected to each other in series with a same forward direction, which clamps the inputted zero current detection signal to the ground potential and a positive power supply voltage to convert to a rectangular signal; and a pulse outputter with a comparator which compares the rectangular signal and a comparison voltage and outputs detection pulses with falling edges that are synchronized with an inductor current reaching zero.

Abstract: A power converter includes: input terminals for inputting a DC voltage; output terminals for outputting an AC voltage; a switch; a first resonant capacitance connected between both ends of the switch; a first LC resonance circuit connected in series with the switch between the output terminals; and a second LC resonance circuit connected between the input terminals and the switch. The first LC resonance circuit includes an inductance and a capacitance in series. When the input terminals are shorted, frequency characteristics of an impedance of the second LC resonance circuit include first to fourth resonant frequencies. The first resonant frequency is higher than a switching frequency of the switch. The second and fourth resonant frequencies are around double and four times the switching frequency. The impedance has local maxima at the first and third resonant frequencies and local minima at the second and fourth resonant frequencies.

Abstract: A power converter includes: two DC input terminals that input a DC input voltage; two DC output terminals that output a DC output voltage; an isolation transformer with a primary winding and a secondary winding; a switch that is connected across the two DC input terminals in a state where the switch is connected in series to the primary winding and that switches the DC input voltage; an LC resonance circuit that includes an inductance and a capacitance and is connected in parallel to the primary winding; a first resonant capacitance that is connected in parallel to the switch; a second resonant capacitance that is connected in parallel to the secondary winding; and a rectifying and smoothing circuit that rectifies and smoothes a voltage generated across both ends of the second resonant capacitance and outputs as the DC output voltage across the two DC output terminals.

Abstract: A wireless power transmission system includes a power feeding device and a power receiving device, wherein the power feeding device includes: a power feeding coil which receives an electric power to generate an AC magnetic field; an inverter for supplying an alternating-current power under a predetermined driving frequency to the power feeding coil; a current detection circuit for detecting a peak value of an alternating current flowing in the power feeding coil; and a controller for controlling the alternating current flowing in the power feeding coil. The power receiving device includes: a power receiving coil for receiving electric power wirelessly via the AC magnetic field; a power receiving side resonance capacitor which configures a power receiving side LC resonance circuit together with the power receiving coil; and a rectifier for rectifying the electric power received by the power receiving coil.

Abstract: A power conversion apparatus includes: DC input terminals for inputting a DC voltage; AC output terminals for outputting an AC voltage; a switching element; a first resonant capacitance connected across the switching element; a first LC resonance circuit that has an inductance and a capacitance connected in series and is connected together with the switching element between the AC output terminals; and a second LC resonance circuit connected in series together with the switching element between the DC input terminals. The second LC resonance circuit includes a first connector portion connected to one DC input terminal and a second connector portion connected to the switching element, and has a first current path, which includes an inductance, and a second current path, which includes a series circuit with an inductance and a capacitance, formed between the first connector portion and the second connector portion.

Abstract: A control circuit according to an embodiment of the present invention is configured to control a switching element of a switching power supply. The control circuit includes a comparator having a first input terminal configured to receive an output voltage of the switching power supply. The comparator has a second input terminal that is connectable to a positive terminal of a reference voltage source. The comparator has an output. The output brings the reference voltage to a first voltage while the output signal takes a first voltage level. The output brings the reference voltage to a second voltage while the output signal takes a second voltage level. The constant voltage source has a positive terminal connected to a negative terminal of the reference voltage source and a ground of the comparator.

Abstract: A FET driving circuit includes: inputs into which a DC voltage is inputted; outputs connected to gate and source electrodes of a FET; a switch; a capacitance connected across the switch; and an LC resonance circuit connected in series with the switch across the inputs. A voltage generated across the switch during switching is outputted to drive the FET. The LC resonance circuit has a first connector connected to one input and a second connector connected to the switch, and is configured with a path including an inductance and a path including an inductance and a capacitance. An impedance between the first and second connectors has two resonant frequencies. The impedance has a local maximum at the lower resonant frequency, which is higher than a switching frequency, and a local minimum at the higher resonant frequency, which is around double the switching frequency.

Abstract: A power converter includes: input terminals for inputting a DC voltage; output terminals for outputting an AC voltage; a switch; a first resonant capacitance connected between both ends of the switch; a first LC resonance circuit connected in series with the switch between the output terminals; and a second LC resonance circuit connected between the input terminals and the switch. The first LC resonance circuit includes an inductance and a capacitance in series. When the input terminals are shorted, frequency characteristics of an impedance of the second LC resonance circuit include first to fourth resonant frequencies. The first resonant frequency is higher than a switching frequency of the switch. The second and fourth resonant frequencies are around double and four times the switching frequency. The impedance has local maxima at the first and third resonant frequencies and local minima at the second and fourth resonant frequencies.

Abstract: A FET driving circuit includes: two inputs for inputting a DC voltage; two outputs respectively connected to gate and source electrodes of a FET; a switch; a resonant capacitance connected between both ends of the switch; and an LC resonance circuit connected between the inputs and both ends of the switch. When the two inputs are shorted, frequency characteristics of an impedance of the LC resonance circuit include, in order from a low to a high-frequency side, first to fourth resonant frequencies. The first resonant frequency is higher than a switching frequency of the switch, the second resonant frequency is around double the switching frequency, the fourth resonant frequency is around four times the switching frequency, and the impedance has local maxima at the first resonant frequency and the third resonant frequency and local minima at the second resonant frequency and the fourth resonant frequency.

Abstract: A switching power supply device generates a DC output voltage based on a DC input voltage, and includes n converter units and a control unit. The control unit executes first driving control that drives k1 (where 0?k1<n) out of the n converter units when the DC output voltage has risen to an upper limit value of the reference voltage range and second driving control that drives k2 (where k1<k2?n) out of the n converter units when the DC output voltage has fallen to a lower limit value of the reference voltage range. During the first driving control, if the DC output voltage Vo reaches a first value above the upper limit value, k1 and k2 are decreased by a value k0. During the second driving control, if the DC output voltage Vo reaches a second value below the lower limit value, k1 and k2 are increased by the value k0.