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 source device includes a peak current limiting circuit in which peak current flowing through a first switching element is detected, and when the current reaches a predetermined value, transistors are turned on in succession to increase the quantity of an electrical signal whereby the first switching element is rapidly turned off, and an on-time limiting circuit for reducing the on-time using reduction of the output voltage. The switching power source device is operated so as to repeat starting and stopping due to a turn-on delay circuit when the output is shortcircuited for reduction of the shortcircuit current.

Abstract: A switching power supply unit includes a first switching control circuit, which has a first ON-time control circuit, and a second switching control circuit, which has a second ON-time control terminal. The first ON-time control circuit controls the ON-time of the first switching element such that, at light load, before a voltage generated across a first drive winding causes a first switching element to be turned on, a first control transistor is brought into conduction to prevent the first switching element from being turned on and to thereby stop oscillation. The second ON-time control circuit controls the ON-time of the second switching element such that, at light load, after the end of the ON-time of the second switching element, energy release from a secondary winding is completed.

Abstract: A self-excited oscillation type switching power source device is constructed such that when a power source switch is turned on, and the voltage of an input power source increases, the voltage at a point a is increased. When the voltage exceeds a predetermined voltage, a first transistor is turned on, and a second transistor is turned off. Then, a first switching element, when a starting voltage is applied to the control terminal thereof, is turned on, and voltage is developed in a first drive winding. This voltage is fed back to the point a via a feedback circuit. As a result, the transistor is accelerated to reach the on-state. The second transistor is accelerated to reach the off-state. As a result, the first switching element is rapidly turned on, and the oscillation is started.

Abstract: A switching power supply unit includes first and second switching elements which are alternately turned on/off so as to perform self-excited oscillation. An inductor and a capacitor resonate during an OFF-period of the first switching element. After the second switching element is turned on, a resonance current applied to a series circuit including the second switching element and the indictor is interrupted before energy is completely emitted from a secondary winding. Accordingly, a voltage is generated at the inductor and a voltage at a transformer is reversed. The switching power supply unit also includes an ON-time control circuit in which a time constant is set so as to turn off the second switching element accordingly.

Abstract: A switching power supply apparatus comprises a transformer having primary winding and at least two secondary windings, a first switching element connected in series with the primary winding, a control circuit for controlling the output from the first switching element by control of the on-time thereof, a rectification circuit for rectifying at least two outputs from the secondary windings, an output detection circuit for detecting the output voltages and feeding back the output voltages as a control signal for control of the on-time to the control circuit. The output voltage detection circuit comprises a control signal formation section in which the control signal for the on-time is formed, corresponding to a voltage at a voltage comparison terminal, and plural voltage detectors connected between the at least two outputs of the secondary windings and the voltage comparison terminal, respectively.

Abstract: A switching power supply unit includes a first switching control circuit, which has a first ON-time control circuit, and a second switching control circuit, which has a second ON-time control terminal. The first ON-time control circuit controls the ON-time of the first switching element such that, at light load, before a voltage generated across a first drive winding causes a first switching element to be turned on, a first control transistor is brought into conduction to prevent the first switching element from being turned on and to thereby stop oscillation. The second ON-time control circuit controls the ON-time of the second switching element such that, at light load, after the end of the ON-time of the second switching element, energy release from a secondary winding is completed.

Abstract: A switching power source device includes a peak current limiting circuit in which peak current flowing through a first switching element is detected, and when the current reaches a predetermined value, transistors are turned on in succession to increase the quantity of an electrical signal whereby the first switching element is rapidly turned off, and an on-time limiting circuit for reducing the on-time using reduction of the output voltage. The switching power source device is operated so as to repeat starting and stopping due to a turn-on delay circuit when the output is shortcircuited for reduction of the shortcircuit current.

Abstract: A switching power supply device in which a transformer, a first switch circuit, and an input power source are connected in series. A series circuit formed of a second switch circuit and a capacitor is connected to one end of the first switch circuit. The transformer has a driving winding which is wound in the same direction as that of the primary winding of the transformer. A capacitive impedance element including a series circuit formed of a capacitor and an inductive ferrite bead, is connected between the termination of the driving winding and the input power source. The switching power supply device uses a less capacitive impedance and thus provides higher radiation noise reduction performance, thereby preventing switching devices from being damaged due to high voltage increase rate of the switching devices.

Abstract: A transformer including a first magnetic core and a second magnetic core having the shape of a flat plate. In the first magnetic core, a middle leg and substantially L-shaped outer legs whose inner sides are formed as circular-arc-shaped surfaces are provided in a standing manner at the central portion and at the comers of a rectangular flat plate, respectively. In addition, in the first magnetic core, a winding accommodating portion is formed between the circular-arc-shaped surfaces of the corresponding outer legs and an outer peripheral surface of the middle leg. Three coil portions, formed by spiral winding operations in level states, are placed upon each other, and are inserted into the winding accommodating portion of the first magnetic core. Then, from above the coil portions, the second magnetic core is placed thereon in order to form an integral structure.

Abstract: A transformer comprises first and second flat coils stacked with each other. Each of first and second flat coils comprises a conductive wire which is wound in a flat spiral shape having a through hole at a center thereof such that the conductive wire has an inner end and an outer end at an inner periphery and an outer periphery of the spiral shape, respectively. The inner end of the first flat coil passes through the through hole of the second flat coil, thus reducing the overall thickness of the transformer because both inner ends pass over only one flat coil.

Abstract: A switching power supply circuit including a transformer having a primary winding, a secondary winding, and a feedback winding; a direct-current power supply of which one end is connected to one end of said primary winding; a switching element connected in series between the other end of said direct-current power supply and the other end of said primary winding; a control circuit provided between the control terminal of said switching element and said feedback winding; a rectifying circuit connected to said secondary winding; and a constant-current circuit provided between the one end of said primary winding and the control circuit or the control terminal of said switching element.

Abstract: A switching power supply unit includes first and second switching elements which are alternately turned on/off so as to perform self-excited oscillation. An inductor and a capacitor resonate during an OFF-period of the first switching element. After the second switching element is turned on, a resonance current applied to a series circuit including the second switching element and the indictor is interrupted before energy is completely emitted from a secondary winding. Accordingly, a voltage is generated at the inductor and a voltage at a transformer is reversed. The switching power supply unit also includes an ON-time control circuit in which a time constant is set so as to turn off the second switching element accordingly.

Abstract: A switching power supply unit includes first and second switching circuits which alternately turn first and second switching elements on and off with an intermediate period in which both are turned off, and energy is stored in a primary winding of a transformer during an ON period of the first switching element and the energy is discharged from a secondary winding of the transformer during an OFF period of the first switching element. A control circuit includes an OFF period extending circuit connected to a control terminal of the first switching element, such that a transistor remains turned on for a desired period even after the energy has been discharged from the secondary winding, extending the OFF period of the first switching element for the desired period. In a light load operation, a phototransistor in the second control circuit is turned on so that the ON period of the second switching element will be shorter than the time required to discharge the energy from the secondary winding.

Abstract: A self-excited oscillation type switching power source device is constructed such that when a power source switch is turned on, and the voltage of an input power source increases, the voltage at a point a is increased. When the voltage exceeds a predetermined voltage, a first transistor is turned on, and a second transistor is turned off. Then, a first switching element, when a starting voltage is applied to the control terminal thereof, is turned on, and voltage is developed in a first drive winding. This voltage is fed back to the point a via a feedback circuit. As a result, the transistor is accelerated to reach the on-state. The second transistor is accelerated to reach the off-state. As a result, the first switching element is rapidly turned on, and the oscillation is started.

Abstract: A switching power supply device that can reduce switching loss to obtain high efficiency. Additionally, the number of components of control circuits and the cost of switching elements can be reduced, with a transformer made compact and lightweight. In this switching power supply device, one end of a series circuit comprising a primary winding of the transformer, an inductor, and a capacitor is connected to a junction of a first switching circuit and a second switching circuit. The other end of the series circuit is connected to an input power source. A secondary winding of the transformer is connected to a rectifying and smoothing circuit including a rectifying element. In addition, in order to perform a self-excited oscillation, there are arranged first and second control circuits.

Abstract: A switching power supply apparatus comprises a transformer having primary winding and at least two secondary windings, a first switching element connected in series with the primary winding, a control circuit for controlling the output from the first switching element by control of the on-time thereof, a rectification circuit for rectifying at least two outputs from the secondary windings, an output detection circuit for detecting the output voltages and feeding back the output voltages as a control signal for control of the on-time to the control circuit. The output voltage detection circuit comprises a control signal formation section in which the control signal for the on-time is formed, corresponding to a voltage at a voltage comparison terminal, and plural voltage detectors connected between the at least two outputs of the secondary windings and the voltage comparison terminal, respectively.

Abstract: A switching power supply unit includes first and second switching circuits which alternately turn first and second switching elements on and off with an intermediate period in which both are turned off, and energy is stored in a primary winding of a transformer during an ON period of the first switching element and the energy is discharged from a secondary winding of the transformer during an OFF period of the first switching element. A control circuit includes an OFF period extending circuit connected to a control terminal of the first switching element, such that a transistor remains turned on for a desired period even after the energy has been discharged from the secondary winding, extending the OFF period of the first switching element for the desired period. In a light load operation, a phototransistor in the second control circuit is turned on so that the ON period of the second switching element will be shorter than the time required to discharge the energy from the secondary winding.

Abstract: A switching power supply device that can reduce switching loss to obtain high efficiency. Additionally, the number of components of control circuits and the cost of switching elements can be reduced, with a transformer made compact and lightweight. In this switching power supply device, one end of a series circuit comprising a primary winding of the transformer, an inductor, and a capacitor is connected to a junction of a first switching circuit and a second switching circuit. The other end of the series circuit is connected to an input power source. A secondary winding of the transformer is connected to a rectifying and smoothing circuit including a rectifying element. In addition, in order to perform a self-excited oscillation, there are arranged first and second control circuits.

Abstract: A switching power supply device in which a transformer, a first switch circuit, and an input power source are connected in series. A series circuit formed of a second switch circuit and a capacitor is connected to one end of the first switch circuit. The transformer has a driving winding which is wound in the same direction as that of the primary winding of the transformer. A capacitive impedance element including a series circuit formed of a capacitor and an inductive ferrite bead, is connected between the termination of the driving winding and the input power source. The switching power supply device uses a less capacitive impedance and thus provides higher radiation noise reduction performance, thereby preventing switching devices from being damaged due to high voltage increase rate of the switching devices.