Abstract: A switching power supply device includes a primary winding of a transformer that is connected in series to a first switching element, and a secondary winding is provided with a rectifier circuit and an output voltage control circuit arranged to detect an output voltage and feed it back to a control circuit. The control circuit is provided with an on-period control circuit arranged to turn off the first switching element in an on-state based on a feedback signal from the output voltage control circuit and an off-period control circuit arranged to control an off-period thereof by delaying turn-on of the first switching element based on the feedback signal.

Abstract: A system and method are described for controlling voltage on discharge capacitors which control light energy from flash lamps, wherein the method includes measuring over time an operational behavior of a flash lamp for performing photothermolysis, wherein a discharge capacitor transfers energy to the flash lamp, empirically deriving a behavior of the flash lamp as a function of operation over time, and using the empirically derived behavior of the flash lamp to control a voltage of the discharge capacitor and thus energy transferred to the flash lamp.

Abstract: A control circuit 8 of a switching power source comprises a voltage detector 31 for detecting a voltage VDC of a DC power supply 1 to produce a detection voltage VDT; a comparator 41 for producing an output signal VCP when detection voltage VDT from voltage detector 31 exceeds a reference voltage VR2; a bottom voltage detector 51 for detecting a bottom point of voltage VDS across a MOS-FET 3 after energy has been discharged from transformer 2; and a switching controller 61 for selectively turning MOS-FET 3 on depending on existence or absence of the output signal VCP from comparator 41. When the input voltage VDC from DC power supply 1 so rises that detection voltage VDT of voltage detector 31 is above the reference voltage VR2, switching controller 61 serves to late turn MOS-FET 3 on at the time bottom voltage detector 51 detects the second or later bottom point of the voltage VDS across MOS-FET 3, extending the off period of MOS-FET 3 to reduce switching frequency of MOS-FET 3.

Abstract: A high-voltage generator includes a high-voltage transformer having a primary coil, a secondary coil, and an auxiliary coil, and a PNP bipolar junction transistor. Based on the self-oscillation theory of a LC oscillator, an oscillating voltage is generated across the primary coil. The oscillating voltage is amplified to a high-level AC voltage through the secondary coil. One end of the auxiliary coil and an emitter of the transistor are coupled to an input DC voltage, and the other end of the auxiliary coil is connected to the base of the transistor through a RC circuit. One end of the primary coil is connected to the collector of the transistor, and the other end of the primary coil is connected to ground.

Abstract: This invention relates to a primary-controlled switched-mode power supply of the type of a free-running flyback converter, which comprises a transformer with a primary-side winding, a secondary-side winding and at least one auxiliary winding. The switched-mode power supply comprises a primary-side switch, which is connected to the primary-side winding, in order to interrupt a current flow through the primary-side winding, a freely oscillating circuit for the generation of switching pulses, which drive the primary-side switch, and a circuit for generating an image voltage between the terminals of the auxiliary winding, in order to generate an image voltage, which on the primary side forms a voltage to be regulated on the secondary side.

Abstract: Method an apparatus for converting the output of a thermoelectric generator to voltages compatible with implantable medical devices is provided. One apparatus includes an implantable thermoelectric generator. The apparatus includes an input terminal for receiving an input voltage generated by a thermoelectric energy converter and a charging inductor connected in series with the input terminal. The apparatus also includes a switching Field Effect Transistor (FET) connected to the inductor, and a capacitor connected to the FET and the input terminal via a diode. The FET is switched with a frequency and duty cycle such that a voltage level at an output terminal is compatible with an implantable medical device. According to various embodiments, the FET is switched using a closed loop feedback system that controls the frequency and duty cycle based on an observed voltage level at the output terminal. Other aspects and embodiments are provided herein.

Abstract: A switching power supply circuit includes a switching element, a converter transformer, a secondary-side rectifying and smoothing circuit, a switching element control unit, a choke coil, a primary-side series resonant circuit, a primary-side parallel resonant circuit, and a series circuit. The switching element implements switching for a direct-current (DC) voltage to convert the voltage into an alternating-current (AC) voltage. The choke coil is supplied with the voltage and is connected to one winding end of the primary winding and one terminal of the switching element. The primary-side series resonant circuit connects a primary-side series resonant capacitor, having a resonant frequency dominated by a leakage inductance. The primary-side parallel resonant circuit connects a primary-side parallel resonant capacitor in parallel to the switching element, having a resonant frequency.

Abstract: In a capacitor charger, a transformer has a primary winding connected between an input voltage and a switch for generating a primary current flowing through the primary winding by switching the switch to thereby induce a secondary current flowing through a secondary winding of the transformer and a secondary voltage tapered from the secondary winding, a control apparatus and method adjusts the on-time period for the switch in response to the input voltage. The charging time and charging current are independent of the input voltage, and there is no power loss resulted from current sense to the primary current.

Abstract: A direct current to direct current voltage converter (DC-DC converter) in accordance with the invention comprises a transformer coupled with a voltage source and a self-starting oscillator that includes a secondary winding of the transformer, a capacitor; and a first switch coupled to conduct current from the DC source via a primary winding of the transformer. The first switch is a normally closed switch. The DC-DC converter also comprises a second switch coupled to conduct current in a parallel path with the first switch, the second switch being a normally open switch having a lower saturation resistance than the first switch.

Abstract: This invention is intended to control the amount of power to be supplied to a fusing heater below a maximum applicable current value. The engine controller supplies electricity to both of two heating bodies at the same fixed duty D1. At a phase angle ?1 corresponding to the fixed duty D1, pulse signals ON1 and ON2 are issued in response to a ZEROX signal as a trigger. A current value I1 is detected based on a HCRRT signal from the current detection circuit. The engine controller calculates an upper limit of applicable power duty Dlimit based on the detected current value I1, the fixed duty D1 and the preset applicable current value Ilimit. Then, a PI temperature control is performed at a duty below the upper limit duty Dlimit.

Abstract: A DC/DC converter has a transformer having a primary winding, a secondary winding, and an auxiliary winding, a switching transistor connected in series to the primary winding, a control transistor for turning the switching transistor on or off, and a feedback control circuit connected to the control transistor and the auxiliary winding. The feedback control circuit includes a Zener diode having a substantially zero temperature coefficient. The Zener diode has a Zener voltage which lies in a range between 5 volts and 6 volts. In order to cancel a temperature characteristic of the control transistor, the temperature coefficient of the Zener diode is selected.

Abstract: A switching power device uses a non-capacitor flyback converter circuit not provided with a smoothing input capacitor having a large capacity. Therefore, a power harmonic can be suppressed and a rush current preventing element is not required. A fluctuation in an output current to be supplied to a load is fed back to the non-capacitor flyback converter circuit by a feedback circuit at a lower speed than an input AC frequency. Therefore, it is possible to improve a power factor by causing an input AC current to be proportional to an input AC voltage. A voltage control circuit controls an output voltage so as to have a constant voltage, and the output voltage is dropped in proportion to an output current when the output current exceeds a threshold. Therefore, it is possible to have the same output characteristic as a power device comprising a low frequency power transformer.

Abstract: A drive transformer and associated circuitry for providing power and appropriate delays to primary switches and synchronous rectifiers in switch-mode power converters. The circuitry takes advantage of the leakage inductances of the drive transformer windings as well as the input capacitance of the primary switches (MOSFETs) to provide the necessary delays. No separate circuitry is needed to provide such delays, thereby providing reliability. Exemplary embodiments further disclose means to disable or enable the primary winding from a condition sensed on the secondary side even with a control and feedback circuit located on the secondary side.

Abstract: A switching power source comprises a current comparator 27 for comparing a voltage level of signals acquired by a current detector 9 with a reference voltage level VDT to produce detection signals VCP of first or second level L or H; an edge detector 28a for sensing an edge of drive signal VG supplied to a gate terminal of MOS-FET 3 during the period of transition from turning on to off of MOS-FET 3; and a decision means 28b for receiving a current detection signal VCP from current comparator 27 to produce an output signal VLD when edge detector 28a catches an edge of drive signal VG; wherein decision means 28b produces different output signals VLD of respectively first and second voltage levels L and H under the light and heavy load conditions to precisely and certainly detect on the primary side of transformer 2 the load condition on the secondary side of transformer 2 for improvement in conversion efficiency.

Abstract: In the case of known switched-mode power supplies with integrated preconditioner, the control curves are largely congruent, but deviate from one another in low-load operation, whereby the unregulated intermediate circuit voltage increases. To improve efficiency in low-load operation, closed-loop control of the burst cycle is effected on the primary side of the voltage transformer. The intermediate circuit voltage is limited to a permissible limit value. The closed-loop control device in the switching stage taps the intermediate circuit voltage at a voltage divider which is arranged between the preconditioner functional unit and the switching stage. An assembly additionally monitors the output voltage, for example by means of an optocoupler. Burst mode comprises one or more burst cycles. A burst cycle is started when the intermediate circuit voltage reaches its limit value. At this time, the voltage transformer is switched off. A burst cycle ends when the output voltage reaches a minimum value.

Abstract: A self-excited switching power supply circuit is provided which reduces a discharge current generated when an oscillating field effect transistor (3) is turned on, whereby it is possible to reduce energy loss and generation of noise when switching is executed. A time constant of an ON-control circuit (12, 23) is set such that when a polarity of a voltage of a feedback winding (2b) has reversed, a gate voltage of the oscillating field effect transistor (3) exceeds a threshold voltage VTH. Accordingly, after a voltage of a primary winding (2a) has become equal to or less than a power supply voltage, the oscillating field effect transistor (3) is turned on, and electrical charge stored in stray capacitance between the windings of the primary winding (2a) and in parasitic capacitance of the oscillating field effect transistor (3) is discharged gradually.

Abstract: The present invention relates to a power unit with a self-oscillating series resonance converter for feeding of a load. The series resonance converter comprises: two transistors TR1, TR2 coupled together, which are arranged to individually be affected by a control transformer T1, a series connection of an inductor L1 and a capacitor C4, and means to change the oscillating frequency of the transistors TR1, TR2 and thereby the output voltage of the power unit. Each transistor TR1, TR2 together with the series coupled discharging capacitor C6, C7 or additional transistor TR3, TR4 belonging thereto is connected in parallel with said inductor L1, capacitor C4 and control transformer T1. The means to change the oscillating frequency of the transistors comprises a control oscillator OSC that in an alternating manner sends pulses that turns off the transistor TR1, TR2 that conducts current and thereby the oscillating frequency of the transistors is controlled by the pulse frequency of the control oscillator OSC.

Abstract: A DC-DC converter circuit for stabilizing the output voltage of the secondary side by correcting the input voltage by using a simple circuit, where no state measurement circuit is necessary at the secondary side. The circuit includes a transformer; a switching circuit including a main switching element which is connected to the primary winding of the transformer in series and has a control terminal for controlling the main switching element, wherein the main switching element is PWM-controlled so as to stabilize an output voltage of the secondary side; a driving circuit for generating PWM driving pulses; and a correction circuit for outputting a voltage whose level is in inverse proportion to an input voltage of the DC-DC converter circuit. An output of the driving circuit is connected to the control terminal of the main switching element and to the correction circuit.

Abstract: A method for operating a switch, which is connected in series with a primary coil of a transformer in a free-running switch mode power supply, includes the provision of a modulation signal and the provision of a drive signal for the switch. The drive signal includes a recurrent pulse sequence which has at least one first switching-on pulse with a first pulse duration and at least one second switching-on pulse with a second pulse duration, and with the pulse duration of at least one of the switching-on pulses being modulated by the modulation signal within a range of valves which is predetermined by the control signal.

Abstract: A DC-DC converter achieves a high level of a signal superimposed in an AC manner onto the output of an insulator such as a photocoupler, and there are very few limitations in the aspects of constant design, phase correction, starting characteristics, and short-circuit protection. A secondary-side control circuit detects an output voltage, and feeds back a control signal to a drive control circuit on the primary side via a photocoupler. The photocoupler insulates the primary side of a DC-DC converter from the secondary side thereof, wherein the control signal output from the secondary-side control circuit is transmitted to the primary side. The output signal of an auxiliary power-supply circuit is superimposed in an AC manner onto the control signal via a coupling capacitor. The drive control circuit has a configuration in which a pulse control signal is applied to a switching element in order to stabilize the output voltage of a secondary-side circuit on the basis of the control signal.

Abstract: A switching power converter and method of controlling an output voltage thereof using predictive sensing of magnetic flux provides a low-cost switching power converter via primary-side control using a primary-side winding. An integrator generates a voltage that represents flux within a magnetic element by integrating a primary-side winding voltage. A detection circuit detects the end of a half-cycle of post-conduction resonance that occurs in the power magnetic element subsequent to zero energy level in the power magnetic element. The integrator voltage is stored at the end of the half-cycle and is used to determine a sampling point prior to or equal to the start of post-conduction resonance in a subsequent switching cycle of the power converter. The primary-side winding voltage is then sampled at the sampling point, providing an indication of the output voltage of the power converter by which the output voltage of the converter can be controlled.

Abstract: A switching power supply circuit includes a converter transformer in which an output obtained by switching a direct current voltage of a converter through resonance is transmitted from the primary side to the secondary side. The switching power supply circuit further includes, on the secondary side of the converter transformer, a secondary step-up winding wound on a portion of a core together with a primary winding, and a low voltage secondary winding wound on another portion of the core. On the secondary side of the converter transformer, an alternating voltage obtained from the step-up winding is utilized to produce a direct current high voltage, and an alternating voltage obtained from the low voltage secondary winding is utilized to produce a direct current low voltage. Consequently, two different direct current outputs including the direct current high voltage and the direct current low voltage are obtained from the converter transformer.

Abstract: A regulated, switch mode power converter is described. An embodiment of the present invention provides regulated, switch mode power conversion from alternating current to direct current utilizing a single transistor and associated switching scheme. Embodiments of the present invention are useful in a variety of applications, including, for example, photo control applications.

Abstract: This switching circuit includes a transformer having primary and secondary windings insulated from each other; a voltage-driven switching element which is connected in series to one of the primary and secondary windings and has a control terminal for controlling a switching operation thereof; a drive circuit which has an output connected to the control terminal and drives the main switching element; and an auxiliary winding which is provided in parallel to the primary winding of the transformer and has an output connected to the control terminal via a capacitor with positive feedback.

Abstract: A switching power supply unit includes a transformer including a primary winding, a secondary winding, and a feedback winding; an input power supply and a first switching element that are connected in series with the primary winding; a control circuit provided between one end of the feedback winding and a control terminal of the first switching element; a rectification circuit connected to the secondary winding; and an output voltage detection circuit for detecting output voltage output from the rectification circuit and for sending a feedback signal to the control circuit. The control circuit includes an on-period control circuit for stabilizing the output voltage by turning off the first switching element in an on-state in accordance with the feedback signal. The control circuit also includes an off-period control circuit for stabilizing the output voltage by delaying turning on of the first switching element in accordance with the feedback signal.

Abstract: The invention concerns a control circuit for controlling a power switch by means of a galvanic insulation transformer, the transformer being produced in the form of planar conductive windings on an insulating substrate (20) whereon are integrated passive components constituting a high frequency excitation oscillating circuit for a primary winding of the transformer, the transformer substrate being directly mounted on a wafer (24) whereon is mounted a circuit chip (40) integrating the power switch.

Abstract: There is provided a power supply apparatus that can raise the power supply efficiency while an appliance in which the power supply apparatus is installed is in a standby state, with a simple construction, without performing complicated control, and can reliably achieve improved power consumption due to the raise in the power supply efficiency, as well as noise reduction. According to the power supply unit, Conduction and interruption of a current flowing in the primary winding 103 of the transformer T21 is controlled. A voltage generated in the secondary winding 104 of the transformer T21 is rectified and smoothed by the rectifier and smoothing circuit 101. An output voltage of the rectifier and smoothing circuit 101 is compared with a reference voltage and a voltage corresponding to a difference between the output voltage and the reference voltage is outputted by error detection circuit 102.

Abstract: The invention involves systems and methods of providing energy to land-based telemetry devices wherein the energy storage and power conditioning system is comprised of an input power supply, an energy storage element, an output supply and a control system. The input power supply provides energy to the output power supply and charges the energy storage element. The energy storage element is comprised of one or more UltraCaps and supplies energy to the output power supply at times of peak need and when the primary energy source to the input power supply is removed. The control system adjusts the voltage supplied to the energy storage element by the input power supply according to changes in the ambient temperature to compensate for changes in the internal equivalent series resistance of the UltraCaps caused by the change in ambient temperature. The output power supply provides energy to the land-based telemetry device.

Abstract: An overcurrent output protector is electrically connected to a constant-voltage switching power supply provided with a switching transistor which converts a DC voltage obtained by smoothing an AC voltage supplied from an AC power source into a cyclic pulse signal. In the overcurrent output protector, duty ratio monitor judges whether an ON duty ratio of the cyclic pulse signal is a predetermined ratio or more. A deactivator turns off the switching transistor in a case where the duty ratio monitor judges that the ON duty ratio is the predetermined ratio or more.

Abstract: Disposed in a secondary side circuit and is connected to a constant voltage control circuit (22), to an overcurrent detection circuit (24), and to an overvoltage detection circuit (26), a photocoupler control circuit (28) controls a photocoupler (IC1) so as to feed a constant voltage detection control signal as a feedback signal back to a primary side circuit. The photocoupler control circuit (28) controls the photocoupler (IC1) so as to turn it off when the photocoupler control circuit is supplied with at least one of an overcurrent detected signal and an overvoltage detected signal. A voltage detection circuit (18) makes a latch circuit (16) operate when the voltage detection circuit detects a voltage induced in an auxiliary winding (NSLD) of a transformer with the photocoupler turned off, thereby making a switching operation of a switching type AC adapter circuit stop.

Abstract: Self-oscillating, current controlled switching power supplies, used for example, as energy storage device charging circuits, and related methods are provided herein. In one implementation, a switching power supply comprises a power transformer having a primary and a secondary, a switching element that switches a voltage source to the primary, and a control circuit that controls the operation of the switching element in response to the measured primary current and secondary current. The switching element disconnects the voltage source from the primary when the primary current reaches a first threshold, causing the secondary current to conduct. The switching element switches back to the primary when the secondary current drops to second threshold. The switching power supply oscillates between charging and discharging the power transformer. In one embodiment, a high value energy storage capacitor is coupled to the secondary and is charged with the secondary current.

Abstract: This invention relates to a digital time mirrored pulse width modulate controller. The controller is electrically connected to a converter unit in which it comprises at least one comparator unit. The comparator unit outputs/inputs a voltage (Vo) and a preset voltage (Vset), and outputs a phase signal having low-level and high-level standards and a core digital processing unit, wherein the core digital processing unit outputs a pulse width modulate signal, through the units mentioned above. The characteristics of the invention can be summed up as follows: the elapsed time of the phase signal in high-level and in low-level is equal, and the root mean square of the output voltage in converter unit is equal to the preset voltage (Vset).

Abstract: A complex resonance type switching converter provided with a self-excited voltage resonance type converter has a conduction controlling device Q2 connected in series with a control winding Nc of a drive transformer CDT in which a detecting winding NA, a driving winding NB of a self-oscillation driving circuit, and the control winding Nc are wound on an identical core. An amount of current conducted in the conduction controlling device Q2 is varied, whereby a level of a base current flowing from the self-oscillation driving circuit to a base of a switching device Q1 is changed and switching frequency of the switching device Q1 is variably controlled. Thereby a conduction angle and the switching frequency of the switching device are changed simultaneously, and consequently constant-voltage control is effected on a direct-current output on the secondary side of the converter. Use of such a drive transformer CDT makes it possible to prevent variations of the self-oscillation driving circuit and reduce size.

Abstract: The present invention provides a worldwide compatible switching power supply unit of an RCC system in which by reducing the number of components or parts, reduction of cost can be realized and the mounting space can be reduced. In a high input voltage and in a light load, an inductance of a primary winding of a transistor is set high but in the range of not exceeding a rated value of a main switching element, and in a low input voltage and in a heavy load, an inductance of a primary auxiliary winding and values of a control resistor and a capacitor of the main switching element are set low but in the range of not deteriorating the starting characteristics of the main switching element.

Abstract: A switching power supply unit includes a transformer, a switching circuit disposed on a primary side of the transformer, a self-driven type synchronous rectifier circuit disposed on a secondary side of the transformer and including a rectifier switch, and a self-oscillation stop circuit disposed on the secondary side of the transformer and adapted to turn off the rectifier switch when a voltage between opposite ends of the rectifier switch exceeds a predetermined value.

Abstract: A commercially available power source is rectified by a diode bridge and a capacitor and supplied to a transformer via a terminal. One end of a primary coil is connected to the terminal and the other end is connected to a switching device. One end of a feedback coil is connected to the switching device and the other end is connected to the terminal. A negative feedback circuit is provided between the switching device and the terminal. A rectifying circuit comprising a diode and a capacitor is provided on a secondary coil. A node of the coil and the capacitor is connected to the terminal via a resistor. In detecting circuits, a voltage across the terminal is detected and a current across the resistor is detected. When the detected voltage and current are equal to predetermined values, a control signal is supplied to a feedback circuit.

Abstract: A power source including a transformer having a primary coil, a secondary coil, and a feedback coil; a resonance capacitor connected in parallel with the primary coil of the transformer in parallel, a switching unit having an input terminal which receives an input voltage input from the feedback coil of the transformer and which controls a current through the primary coil of the transformer according to the input voltage; and a current detection unit which detects the current in order to turn off the switching unit when the detected current is higher than a predetermined current. An output voltage stabilization circuit controls the input voltage at the input terminal of the switching unit, proportional to a voltage output by the secondary coil of the transformer.

Abstract: The present invention relates to a method and an apparatus for controlling an electric motor by regulating at least the current Iout, the voltage Uout and the frequency fout to an input of said motor, where the number of revolutions of said electric motor is proportional to said frequency fout. If an available power Pin from an energy source is greater than or equal to the nominal requested power Pnom of said electric motor, the current Iout, voltage Uout and frequency fout are set to there corresponding nominal values Inom, Unom and fnom, respectively, to achieve said requested power Pnom and frequency fnom. If said available power Pin is less than the requester power Pnom, the voltage Uout and the frequency fout are reduced such that the relation between the voltage Uout and the frequency fout is essentially constant while said current Iout is kept at its nominal value Inom.

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 power supply circuit improves the power factor when the load is light, and incorporates a starting circuit for reacting quickly to the changes in the output from the power supply circuit and a short-circuit detecting means for detecting the short-circuit of the feedback signal. The apparatus includes: an error amplifier; a comparator that monitors the output from the error amplifier and generates an offset regulating current ISO; a multiplier; a sensing current comparator that compares the output signal from the multiplier and the AC line current and generates a reset signal; a timer that directly monitors the inputted zero-cross signal; and a comparator for short-circuit detection, that facilitates reducing the exterior parts and components.

Abstract: A circuit configuration for pulsed application of a first supply voltage to a load includes a first switch, connected in series with the load, a first control connector, a control circuit for control of the first switch and having a first output terminal connected to the control connector of the first switch and first and second voltage supply terminals, a second switch connected between the load and the first voltage supply terminal of the control circuit and having a second control connector to which a control signal is supplied. The invention also includes a method for actuating the first and second switches and use of the inventive circuit configuration in a switched-mode power supply or a power factor controller.

Abstract: A method of improving modulation resolution in a flyback converter by pulsewidth- and/or position-modulation of a subtractive constant current with specific timing considerations is applicable to boost or buck/boost topologies. A typical system of this type uses a pulsewidth-modulated (PWM) circuit to provide a control pulsewidth in response to an incoming data stream. The control pulsewidth is used to drive a switching device which, when energized, charges an inductor. When the switching device is released the energy stored in the inductor “flies back” through a diode into a capacitor and load resistance. According to this invention, a constant current sink, gated under control of the PWM controller, is used to improve modulation resolution through pulsewidth- and position-modulation of a subtractive constant current with specific timing considerations. In the preferred embodiment, the constant current sink is implemented using a transistor in conjunction with a resistor network.

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 device for monitoring the flow of a current in a load powered by a DC voltage source and a method for the implementation of the device. The device includes, series-connected with the load, a first device to detect the presence of an alternating current and a second device to interrupt the current flowing in the first device while keeping the current substantially direct in the load. Advantageously, the second device includes at least one first electronic switch series-connected with the load and with the first device, the first electronic switch being controlled so as to set up the alternating current in the first device. A method of implementing the device cyclically opens and closes the electronic switch while making the second device operable or inoperable, also cyclically, to keep the current substantially direct in the load and let the current flowing in the load pass through the second device only periodically.

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 voltage converter including a transformer having a primary winding connected in series with a switch for cutting-up a supply voltage and having a secondary winding associated with a capacitor providing a D.C. low voltage, and a self-oscillating control circuit of the switch for detecting the end of the demagnetization of an auxiliary winding of the transformer, to turn the switch on, and for detecting the current in the on-state switch to turn it off when this current reaches a reference point. The reference point is made variable according to the voltage across the auxiliary winding.

Abstract: A power conversion apparatus capable of reducing the conduction loss to achieve high efficiency yielding a downsized and weight-reduced apparatus and a method for driving such a power conversion apparatus is disclosed. A power conversion apparatus comprising a switching-element driving circuit which includes a current transformer having a primary coil connected to an current control type switching element, and a driving-current generating circuit formed of a secondary coil of the current transformer and a rectifying circuit connected to the secondary coil, wherein an output current generated in the driving-current generating circuit is supplied to the switching element as a driving current of the switching element, and a method for driving the switching element of such a power conversion apparatus are disclosed.

Abstract: A switched-mode power supply has primary and secondary sides, and a transformer (M1) with a primary winding, a secondary winding and an auxiliary winding. The primary winding and the auxiliary winding are connected to the primary side, and the secondary winding is connected to the secondary side. A switch element (T3) is connected to the primary winding in order to interrupt a current flowing in the primary winding. The switched-mode power supply contains a freely oscillating circuit (R5, C3, R7, T1, T2, R8, R9, R10, R11) for generating switching pulses to the switch element (T3). A rectifying and charge storing coupling (D4, C5) is connected between the terminals of the auxiliary winding in order to generate such an image voltage which on the primary side represents a certain voltage of the secondary side.

Abstract: A switching power supply unit includes a control circuit including a turn-off circuit for turning of a first switch element Q1, which has been in an ON state, and an off-period control circuit for, based on a feedback signal from an output-voltage detecting circuit, controlling the turning-on of the first switch element to be further delayed as a load is lighter. The off-period control circuit includes a transistor as a second switch element which is provided in series between a feedback winding and the control terminal of the first switch element and which is controlled to be turned on and off based on the feedback signal from the output-voltage detecting circuit. A switching frequency is set to be lower as the load is lighter, such that power consumption at the light load is reduced.

Abstract: A method and a circuit for detecting a light load mode of a switching power supply system are provided. The switching power supply system has a first winding, a second winding, a third winding having a voltage being in proportion to an output voltage of the second winding, and a signal converting device electrically connected to the third winding. The method includes steps of measuring a voltage of the signal converting device, and determining the switching power supply system being under the light load mode when the voltage of the signal converting device is smaller than a predetermined threshold voltage.