Abstract: In a switching power supply device with reduced size and increased power conversion efficiency, a first resonant circuit including a series resonant inductor and a series resonant capacitor, and a second resonant circuit including a series resonant inductor and a series resonant capacitor, are caused to resonate with each other to cause sympathetic vibration of each resonant circuit, such that transmission is performed by utilizing both magnetic field coupling and electric field coupling between a primary winding and a secondary winding. Operation at a switching frequency higher than a specific resonant frequency of an overall multi-resonant circuit allows a ZVS operation to be performed, enabling a significant reduction in switching loss and high-efficiency operation.

Abstract: A resonance-type power supply is provided in which no short circuit occurs and driving is performed with a constant switching period by performing switching control using a change of magnetic flux of a magnetic component as a trigger. When the change of magnetic flux of the transformer is detected, the first switching control signal is caused to transition to the Hi level. The detection voltage signal is A/D-converted, a first on-time is determined from the level thereof, and a second on-time is calculated by subtracting the first on-time from the constant switching period. When the first switching control signal is caused to transition to the Low level based on the first on-time, the change of magnetic flux of the transformer is detected, and the second switching control signal is caused to transition to the Hi level and is caused to transition to the Low level after the second on-time has elapsed.

Abstract: A switching control IC outputs a rectangular wave signal from an output terminal thereof to a driving circuit. A feedback circuit compares a value of a divided voltage of a voltage across output terminals of a switching power supply device with a reference voltage, generates a feedback signal, and inputs the feedback signal into a feedback terminal of the switching control IC. A capacitor and a Zener diode are connected between the feedback terminal and a ground terminal. The Zener diode is selectively connected, and a voltage at the feedback terminal is changed in accordance with the presence of the Zener diode. A voltage at the feedback terminal is detected, and one of a latch method and a hiccup method is selected as a method for an overcurrent protection operation in accordance with the detected voltage.

Abstract: A transformer that realizes ZVS operation includes a primary winding and a secondary winding. A control circuit turns switching elements on and off in a complimentary manner in order to repeatedly invert the voltage applied to the primary winding. A conduction path supplies a voltage excited in the secondary winding to a load connected between a high-potential side and a ground side of the secondary winding. A first rectifier diode has a rectification direction extending from the high-potential side toward the ground side of the load and is provided along the conduction path. A second rectifier diode and a capacitor, which are connected in series with each other, are connected in parallel with the secondary winding. An inductor is connected in parallel with the second rectifier diode. A rectification direction of the second rectifier diode matches the direction extending from the high-potential side to the ground side.

Abstract: In a switching control circuit, a length of a soft start period is set in accordance with a time constant of an external circuit connected to a soft start terminal of a switching control IC. A current flowing through a switching element is detected at a current detection terminal. When the value of the current exceeds a first predetermined current value, a second overcurrent protection function is performed, so that a switching operation is stopped. When the value of the current exceeds a second predetermined current value, a second overcurrent protection function is performed, so that the switching element is quickly turned off and a current peak value is limited. On the basis of a voltage at the soft start terminal after the soft start period has elapsed, one of the setting and non-setting of the first overcurrent protection function is selected.

Abstract: In a switching power supply apparatus, a switching element is turned on/off to intermittently conduct current input via an inductor. Current input during a period in which the switching element is turned off is supplied to an electrolytic capacitor via a conduction path. A rectifier diode is provided in the conduction path to face toward the electrolytic capacitor. An inductor is provided in the conduction path to be connected in series with the rectifier diode. A high speed diode has a reverse recovery time shorter than the reverse recovery time of the rectifier diode, and is connected in parallel with the inductor to face toward the electrolytic capacitor.

Abstract: A switching power-supply circuit includes a transformer, a first switching element, a first rectifying/smoothing circuit generating a first output voltage by rectifying and smoothing the output of a first secondary winding, a second rectifying/smoothing circuit generating a second output voltage by rectifying and smoothing the output of a second secondary winding, a first feedback circuit generating a feedback signal according to the first output voltage, and a first switching control circuit. When the voltage of the second secondary winding is greater than the second output voltage and the second output voltage is less than the voltage of a reference-voltage circuit, a second rectifier circuit turns on a rectifier switch element, and stabilizes the second output voltage by controlling the number of pulses per unit time in a pulse current flowing through the second rectifier circuit.

Abstract: A switching power-supply circuit includes a second rectifying/smoothing circuit arranged to generate a second output voltage by rectifying and smoothing the output of a second secondary winding, and the second rectifying/smoothing circuit includes a second rectifier circuit and a capacitor, connected to the second secondary winding. A second switching control circuit operates in response to an alternating-current winding voltage occurring in the second secondary winding, and includes a time constant circuit causing a switch mechanism connected to the control terminal of a rectifier switch element to operate, and a second feedback circuit arranged to detect and feed back the second output voltage to the time constant circuit.

Abstract: In a power supply apparatus driving circuit, at startup, an input voltage of a switching power supply is used as a driving power supply, and loss generated in a starting circuit is reduced. The starting circuit and the driving circuit are configured as a single driver. A control IC generates a switching control signal to control a first switching element and a second switching element. A driving circuit in a high breakdown voltage driver IC generates gate drive voltage signals for the first switching element and the second switching element based on the switching control signal inputted from the control IC. A starting circuit supplies the partial voltage of a voltage inputted to a starting power supply terminal, to each of the driving circuit in the high breakdown voltage driver IC and the control IC that is externally provided, and shuts off a switching element after startup.

Abstract: In an ON/OFF type isolated DC-DC converter that stores electromagnetic energy in a main transformer during an ON period of a power switch and releases the electromagnetic energy to an output during an OFF period of the power switch, high-speed, highly stable output voltage control without the need for a photocoupler, for which the allowable temperature range is relatively narrow and the current transfer ratio changes over time, is performed. An integrating circuit including a resistor and a capacitor generates a ramp wave, and the ramp wave is superposed on a reference voltage of a reference voltage source Vref through a capacitor. A comparator compares a voltage Vo that is proportional to an output voltage of a converter with the reference voltage on which the ramp wave has been superposed, and transmits an inversion timing signal through a pulse transformer.

Abstract: A switching control IC conducts on-off control on a first switching element. A second switching control circuit is provided between a high-side driving winding of a transformer T and a second switching element. The second switching control circuit discharges a capacitor in a negative direction with a constant current during an on period of the first switching element, and then after the second switching element is turned on, charges the capacitor in a positive direction with a constant current. A transistor controls the on period of the second switching element in accordance with the ratio of a charging current to a discharge current such that the ratio of the on period of the second switching element to the on period of the first switching element is substantially always constant.

Abstract: In a switching power supply apparatus, a first switching element is controlled by a driving voltage output from a switching control IC. A second switching control circuit controls the on-time of a second switching element so that the time ratio of the on-time of the second switching element to the on-time of the first switching element becomes almost constant with respect to a change in a load current. In a normal load state, since a square wave output from a frequency setting unit within the switching control IC is output with no change, a converter operates in a current-continuous mode. In a light load state, a driving signal generation unit within the switching control IC is subjected to blanking with the period of a signal output from a maximum frequency setting unit and an oscillation frequency is reduced. Accordingly, the converter operates in a current-discontinuous mode.

Abstract: A digital signal processing circuit which performs average current control is disposed on a secondary side of a transformer of an isolated DC-DC converter, and a switching control signal output from the digital signal processing circuit is transmitted to a switching element included in a power factor correction converter through an isolated drive circuit. The digital signal processing circuit obtains an average value of currents supplied to an inductor in accordance with a voltage output from a bias winding of the inductor or an output from a secondary side of a current transformer which detects a drain current of the switching element. Furthermore, the average value of the currents corresponds to a waveform (full-wave rectification sine wave) of an input voltage Vi.

Abstract: In an isolated switching power supply apparatus, by performing on/off control of a first switching device and a second switching device, energy is transmitted from the primary side to the secondary side using a second primary winding and a second secondary winding while the first switching device is on, and energy is transmitted by a first primary winding and a first secondary winding while the second switching device is on. The first secondary winding and the second secondary winding are connected in series with one another, and an inductor is inserted in series to the second secondary winding. An output current is made to flow through the inductor irrespective of whether the first switching device is on or the second switching device is on.

Abstract: In a switching power supply apparatus, a comparator outputs a first determination criterion signal based on a saw-tooth wave signal whose level fluctuates with a constant period and a detection voltage signal. An inverter subjects the first determination criterion signal to reverse processing, and outputs a second determination criterion signal. The comparator outputs a first switching judgment-use signal from a monitor signal and a threshold value, and the comparator outputs a second switching judgment-use signal from the monitor signal and the threshold value. An AND circuit outputs the first switching control signal from the first determination criterion signal and the first switching judgment-use signal, and the AND circuit outputs the second switching control signal from the second determination criterion signal and the second switching judgment-use signal.

Abstract: A resonance-type power supply is provided in which no short circuit occurs and driving is performed with a constant switching period by performing switching control using a change of magnetic flux of a magnetic component as a trigger. When the change of magnetic flux of the transformer is detected, the first switching control signal is caused to transition to the Hi level. The detection voltage signal is A/D-converted, a first on-time is determined from the level thereof, and a second on-time is calculated by subtracting the first on-time from the constant switching period. When the first switching control signal is caused to transition to the Low level based on the first on-time, the change of magnetic flux of the transformer is detected, and the second switching control signal is caused to transition to the Hi level and is caused to transition to the Low level after the second on-time has elapsed.

Abstract: In an ON/OFF type isolated DC-DC converter that stores electromagnetic energy in a main transformer during an ON period of a power switch and releases the electromagnetic energy to an output during an OFF period of the power switch, high-speed, highly stable output voltage control without the need for a photocoupler, for which the allowable temperature range is relatively narrow and the current transfer ratio changes over time, is performed. An integrating circuit including a resistor and a capacitor generates a ramp wave, and the ramp wave is superposed on a reference voltage of a reference voltage source Vref through a capacitor. A comparator compares a voltage Vo that is proportional to an output voltage of a converter with the reference voltage on which the ramp wave has been superposed, and transmits an inversion timing signal through a pulse transformer.

Abstract: A transformer includes a first secondary winding, a second secondary winding, and a third secondary winding. The second secondary winding and the third secondary winding are wound to include the same number of turns and to have opposite magnetic polarities. A low-pass filter includes a second inductor defined by a leakage inductance of the second secondary winding connected in series with the second secondary winding, a second inductor defined by a leakage inductance of the third secondary winding connected in series with the third secondary winding, and a second capacitor. An output voltage is output from an output terminal of the low-pass filter.

Abstract: A switching control IC outputs a rectangular wave signal from an output terminal thereof to a driving circuit. A feedback circuit compares a value of a divided voltage of a voltage across output terminals of a switching power supply device with a reference voltage, generates a feedback signal, and inputs the feedback signal into a feedback terminal of the switching control IC. A capacitor and a Zener diode are connected between the feedback terminal and a ground terminal. The Zener diode is selectively connected, and a voltage at the feedback terminal is changed in accordance with the presence of the Zener diode. A voltage at the feedback terminal is detected, and one of a latch method and a hiccup method is selected as a method for an overcurrent protection operation in accordance with the detected voltage.

Abstract: In a switching power-supply apparatus, a primary-side power converter circuit includes a half bridge system and a synchronous rectifier circuit is provided as a rectifier circuit of a secondary-side power converter circuit. An on time ratio of the on time of a first switching element to the on time of a second switching element is controlled so as to provide an operation mode in which energy is regenerated from the secondary side to the primary side when the load is light.