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.

Abstract: A switching power-supply apparatus and a switching power supply circuit in which a feedback signal is input from a feedback circuit to a feedback terminal of a switching control IC includes a capacitor and a Zener diode connected between the feedback terminal and a ground terminal. The Zener diode is a selectively connected external circuit. A voltage of the feedback terminal during an overcurrent operation changes depending on whether or not the external circuit is present. A return/latch determination circuit detects the voltage of the feedback terminal to switch between an automatic return system and a latch system in an overcurrent operation state.

Abstract: In a switching power supply device, a first switch element, which defines a main switch element of a DC-DC converter, and a third switch element, which defines a switch element of a power-factor correcting circuit, are controlled such that turn-on timings are synchronized while on-period control is independently performed to thereby prevent an increase in switching frequency and prevent noise by eliminating intermittent oscillation. Thus, it is possible to prevent intermittent oscillation control due to an increase in switching frequency of the first switch element under a light load state or a no load state. This eliminates problems of the frequency of intermittent oscillation that falls within an audible frequency range causing noise and increasing ripple voltage.

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: 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 power factor correction converter includes a diode bridge arranged to perform full-wave rectification on an AC input power supply, a switching element arranged to perform switching on an output voltage thereof, an inductor arranged to pass a current interrupted by the switching element and to accumulate and emit excitation energy, a diode, and a smoothing capacitor defining a step-up chopper circuit. A digital signal processing circuit detects a phase of an input voltage, and a switching frequency of the switching element is modulated in accordance with the phase. Accordingly, the switching frequency can be appropriately modulated without depending on an input voltage, so that a wide range of input voltages can be accepted while suppressing EMI noise with a peak generated in the switching frequency and higher-order frequency components thereof.

Abstract: A switching power-supply unit uses a time when a transformer voltage Vt inverts due to a rectifier diode (Ds1) entering a non-conducting state as a trigger, and a first switching control circuit (CNT1) turns on a first switching element (Q1) after a predetermined delay time passes. A second switching control circuit (CNT2) turns on a second switching element (Q2) using a time when the transformer voltage Vt inverts due to turning off of the first switching element (Q1) as a trigger. A third switching control circuit (CNT3) turns on a third switching element (Q3) using turning off of the second switching element (Q2) as a trigger. The first switching control circuit (CNT1) determines a period ton1 of the first switching element (Q1) such that a first output voltage Vo1 is set to a predetermined value. The second switching control circuit (CNT2) determines an ON-period ton2 of the second switching element (Q2) such that a second output voltage Vo2 is set to a predetermined value.

Abstract: In a switching power supply apparatus, an inductor, a transformer, a first switching circuit, a second switching circuit, and a capacitor are connected to each other so that a first switching element and a second switching element can be alternately turned on and off, an output can be obtained from a secondary winding of the transformer, and an output voltage can be controlled by controlling the ON period of the first switching element. The secondary winding of the transformer is connected to a first rectifying and smoothing circuit. A first control circuit is configured to operate using a DC voltage supplied from a second rectifying and smoothing circuit. After the second switching element has been turned on, the second switching element is forcefully turned off at a predetermined time set by a turn-off circuit included in a second control circuit that operates using an AC voltage.

Abstract: A power factor correction converter includes a diode bridge arranged to perform full-wave rectification on an AC input power supply, a switching element arranged to perform switching on an output voltage thereof, an inductor arranged to pass a current interrupted by the switching element and to accumulate and emit excitation energy, a diode, and a smoothing capacitor defining a step-up chopper circuit. A digital signal processing circuit detects a phase of an input voltage, and a switching frequency of the switching element is modulated in accordance with the phase. Accordingly, the switching frequency can be appropriately modulated without depending on an input voltage, so that a wide range of input voltages can be accepted while suppressing EMI noise with a peak generated in the switching frequency and higher-order frequency components thereof.

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 a switching power supply device, a first switch element, which defines a main switch element of a DC-DC converter, and a third switch element, which defines a switch element of a power-factor correcting circuit, are controlled such that turn-on timings are synchronized while on-period control is independently performed to thereby prevent an increase in switching frequency and prevent noise by eliminating intermittent oscillation. Thus, it is possible to prevent intermittent oscillation control due to an increase in switching frequency of the first switch element under a light load state or a no load state. This eliminates problems of the frequency of intermittent oscillation that falls within an audible frequency range causing noise and increasing ripple voltage.

Abstract: In a switching power supply apparatus, an inductor, a transformer, a first switching circuit, a second switching circuit, and a capacitor are connected to each other so that a first switching element and a second switching element can be alternately turned on and off, an output can be obtained from a secondary winding of the transformer, and an output voltage can be controlled by controlling the ON period of the first switching element. The secondary winding of the transformer is connected to a first rectifying and smoothing circuit. A first control circuit is configured to operate using a DC voltage supplied from a second rectifying and smoothing circuit. After the second switching element has been turned on, the second switching element is forcefully turned off at a predetermined time set by a turn-off circuit included in a second control circuit that operates using an AC voltage.

Abstract: A switching power supply apparatus includes a first inductor that is serially connected to a primary winding of a transformer, and a second inductor that is arranged so as to apply a voltage of a capacitor with sine waves obtained by rectifying an AC input voltage for an on-period of a first switching circuit. A diode for preventing the inverse current to the second inductor and a capacitor that is charged by excitation energy charged to the second inductor and applies a voltage to the primary winding for on-period of the first switching circuit. Further, a capacitor is arranged so that the inductor, the primary winding, and a second switching circuit define a closed loop. Switching control circuits control the on-period of a first switching element to control an output voltage Vo, and further control an input voltage Vi by controlling the on-period of a second switching element.

Abstract: A switching power supply apparatus includes first and second switch circuits (S1) and (S2) including switch devices (Q1) and (Q2), diodes (D1) and (D2), and capacitors (Cds1) and (Cds2), and a transformer (T). A first inductor (Lr) is connected in series with a primary winding (Lp) of the transformer (T), and a second inductor (Li) is arranged so that a voltage of a third capacitor (Ca) is applied during an on-period of the first switch circuit (S1). A diode (Di) preventing a reverse current from flowing in the second inductor (Li), and a capacitor (Ci) that is charged by excitation energy stored in the second inductor (Li) and that applies a voltage to the primary winding (Lp) during the on-period of the first switch circuit (S1) are further provided. A capacitor (Cr) is further provided so as to define a closed loop together with the inductor (Lr), the primary winding (Lp), and the second switch circuit (S2).

Abstract: A switching power-supply unit uses a time when a transformer voltage Vt inverts due to a rectifier diode (Ds1) entering a non-conducting state as a trigger, and a first switching control circuit (CNT1) turns on a first switching element (Q1) after a predetermined delay time passes. A second switching control circuit (CNT2) turns on a second switching element (Q2) using a time when the transformer voltage Vt inverts due to turning off of the first switching element (Q1) as a trigger. A third switching control circuit (CNT3) turns on a third switching element (Q3) using turning off of the second switching element (Q2) as a trigger. The first switching control circuit (CNT1) determines a period ton1 of the first switching element (Q1) such that a first output voltage Vo1 is set to a predetermined value. The second switching control circuit (CNT2) determines an ON-period ton2 of the second switching element (Q2) such that a second output voltage Vo2 is set to a predetermined value.

Abstract: A switching power supply apparatus includes a first inductor that is serially connected to a primary winding of a transformer, and a second inductor that is arranged so as to apply a voltage of a capacitor with sine waves obtained by rectifying an AC input voltage for an on-period of a first switching circuit. A diode for preventing the inverse current to the second inductor and a capacitor that is charged by excitation energy charged to the second inductor and applies a voltage to the primary winding for on-period of the first switching circuit. Further, a capacitor is arranged so that the inductor, the primary winding, and a second switching circuit define a closed loop. Switching control circuits control the on-period of a first switching element to control an output voltage Vo, and further control an input voltage Vi by controlling the on-period of a second switching element.

Abstract: A switching power supply apparatus includes first and second switch circuits (S1) and (S2) including switch devices (Q1) and (Q2), diodes (D1) and (D2), and capacitors (Cds1) and (Cds2), and a transformer (T). A first inductor (Lr) is connected in series with a primary winding (Lp) of the transformer (T), and a second inductor (Li) is arranged so that a voltage of a third capacitor (Ca) is applied during an on-period of the first switch circuit (S1). A diode (Di) preventing a reverse current from flowing in the second inductor (Li), and a capacitor (Ci) that is charged by excitation energy stored in the second inductor (Li) and that applies a voltage to the primary winding (Lp) during the on-period of the first switch circuit (S1) are further provided. A capacitor (Cr) is further provided so as to define a closed loop together with the inductor (Lr), the primary winding (Lp), and the second switch circuit (S2).

Abstract: A switching power supply apparatus includes a first commutation inductor which is provided in a path of current flowing from a power supply input unit through a first switching circuit and an inductor during an ON period of a first switching circuit, and a second commutation inductor provided in a path of current flowing through the inductor during an OFF period of the first switching circuit. The first and second commutation inductors and the inductor are connected to a first junction point. One end of a clamping series circuit, which includes a second switching circuit and a series capacitor connected in series, is connected to a second junction point, which connects the first commutation inductor and the first switching circuit, and the other end thereof is connected so that the first and second commutation inductors and the series capacitor constitute a resonance circuit. Accordingly, first and second switching elements can be turned on at a zero voltage.

Abstract: A switching power supply apparatus includes a first commutation inductor which is provided in a path of current flowing from a power supply input unit through a first switching circuit and an inductor during an ON period of a first switching circuit, and a second commutation inductor provided in a path of current flowing through the inductor during an OFF period of the first switching circuit. The first and second commutation inductors and the inductor are connected to a first junction point. One end of a clamping series circuit, which includes a second switching circuit and a series capacitor connected in series, is connected to a second junction point, which connects the first commutation inductor and the first switching circuit, and the other end thereof is connected so that the first and second commutation inductors and the series capacitor constitute a resonance circuit. Accordingly, first and second switching elements can be turned on at a zero voltage.