Abstract: In a power supply circuit supplying a high voltage charger of an implantable cardioverter-defibrillator (ICD), a changer circuit switches the power source of the power supply circuit between a battery and an output signal of a step-up converter. The signal derived from the boost winding rises to a high voltage when the high voltage charger charges the storage capacitors of the ICD. A system current measurement circuit can be provided in the power supply circuit.

Abstract: A boost circuit effects increasing current flow through an inductor and a switch when the switch is closed, and then, when the switch is open, directs the inductor current through a diode to charge a storage capacitor at the output. A logic circuit operates the switch. The switch is controlled on by sensing low current flow in the capacitor and off by sensing high current flow in the switch, so that inductor current is continuous.

Abstract: A switch-mode power supply which can simplify its circuit construction and reduce its size and manufacturing cost by achieving output supply voltage control and prevention of overcurrent using a single circuit. The switch-mode power supply includes first and second supply voltage conversion sections for converting an input AC supply voltage in a switching mode, and a control section which senses a converted output supply voltage and an output supply current according to the converted output supply voltage provided from the second supply voltage conversion section to provide a control signal corresponding to the sensed voltage and current. The control section is coupled to the first supply voltage conversion section and controls the operation of the first supply voltage conversion section according to the control signal.

Abstract: A regulated power supply having power factor correction control which includes a state variable integrator/error amplifier that provides a low distortion error signal during steady state operation and fast transient response for tight output voltage control.

Abstract: A circuit for improving output voltage regulation of a power factor control stage providing power to a load. The circuit includes a voltage reference generating circuit that produces a voltage signal that is in phase lock with an input alternating current power line signal but is independent of voltage excursions of the alternating current line signal and unwanted voltage harmonics. The circuit also includes a control circuit receiving the voltage reference signal for controlling an electronic switch coupled to an input line providing power to the load. The electronic switch is pulsed on and off by the control circuit to force the current in the input line to the load to follow the reference voltage. The input alternating current line current is thus maintained in a substantially constant predetermined phase relationship with the input alternating current line voltage.

Abstract: A circuit for detecting voltage variations in relation to a set value, for devices, such as a power supply circuit, comprising an error amplifier fed back by a compensating capacitor which, under steady state operating conditions, is not supplied with current, and, in the presence of transient output voltage (V.sub.o) of the device, is supplied with current (DI) proportional to the variation in voltage, the circuit comprising a current sensor connected to the compensating capacitor for detecting the current (DI) through the same; and the output signal of the sensor preferably being supplied to a circuit for limiting the variation in output voltage which, in the event the voltage variation exceeds a given threshold value (V.sub.R1), activates a control stage connected to the output of the device.

Abstract: A method for preventing excessive currents in a welding converter that, by use of power semiconductors, generates a two-phase, pulse-width-modulated a.c current from a rectified mains a.c. current supplied to the primary side of a welding transformer. The method includes the following method steps: detecting the current of at least one phase of the primary circuit by a sensor (20); for each detected current signal, forming the time derivation through differentiation according to the time; comparing the time-derived measured signal with a predetermined maximum value; and if the time-derived measured signal exceeds the predetermined maximum value, emitting a signal that leads to deactivation of the power semiconductors (16).

Abstract: A protective circuit is used in conjunction with a switching power source for protecting the latter from overload and from short circuits. It is detected whether the current at the primary winding current of a switching power source transformer, the load current of the switching power source, or both exceed predetermined reference voltages. If so, supply of power to the switching power source is interrupted for a predetermined period of time, thereby bringing the switching power source into inoperable condition in this duration.

Abstract: A high-power-factor power supply has a full-wave rectifier for rectifying an AC line voltage, a power regulator including switch means responsive to a control signal for controlling the application of the rectifier output to a load; and a control circuit for producing a switching control signal. The control signal includes a pair of AC line detectors: a first connected in a closed-loop automatic gain control arrangement, and the other connected in an open-loop arrangement. The control circuit initially produces a CURRENT DEMAND REFERENCE signal that is directly related to the difference between the power supply DC output voltage and a self-generated constant reference, and to the waveform shape of the AC line voltage, and is inversely related to magnitude changes of the AC line voltage. The control signal then produces the switching control signal in response to both the CURRENT DEMAND REFERENCE signal and the current flowing in the power supply.

Abstract: This disclosure relates to a power supply circuit for converting AC energy from an AC source to DC energy for powering a load. The circuit comprises first and second circuit lines and a full wave rectifier connectable to the AC source and to the circuit lines for providing a rectified input voltage on the circuit lines. An inductor is connected in one of the circuit lines and an output capacitor is connected across the circuit lines between the inductor and the load. A control switch including two power terminals and a control terminal has the two power terminals connected across the circuit lines between the inductor and the output capacitor. A sensor responsive to current flow through the inductor provides a current representative signal. A relatively high fixed frequency oscillator closes the control switch in each cycle thereof.

Abstract: A source power coupler for coupling a power source to a first transmission line and a second transmission line. DC power from the power source is conducted by the source power coupler to the first and the second transmission lines while AC signals on the first and the second transmission lines are isolated from the power source by the source power coupler. The source power coupler is comprised of an operational amplifier having a non-inverting input and an inverting input. The gate of a transistor is coupled to an output of the operational amplifier. The transistor's drain is coupled to one of the transmission lines. And the transistor's source is coupled to the inverting input of the op-amp. Thereby, a control loop is formed, which provides an AC impedance between the power source and one of the transmission lines. A resistor is coupled between the source of the transistor and the power source, and a capacitor is coupled between the non-inverting input of the op-amp and the power source.

Abstract: A nonlinear ripple feedback circuit for use with a current-sourced rectifier system with an inductor input filter. The nonlinear ripple feedback circuit eliminates the oscillation of the rectifiers and improves the line-current waveform by sensing of and compensating for any amplitude of ripple appearing in the DC-side current. A sample of the rectified line voltage is multiplied by the product of a voltage feedback control signal times the ripple feedback signal ratio to form the input to the pulse-width modulator which produces the gating waveform for the converter of the rectifier system such that the oscillation and sensitivity of the converter system is reduced, and the AC line current waveform has low distortion, regardless of the DC-side ripple current levels.

Abstract: A device for connecting in series between a source of alternating current power and a direct current load which decouples the power flow from the source to the load and thereby enables efficient modification of the current waveform supplied by the source to reduce current harmonics, improve the current form factor and improve the power factor. Particular uses for the device include battery chargers, off-line switching power supplies as used by computers, electronic ballasts for fluorescent tubes and variable speed electric motor controls.

Abstract: A parallel running control apparatus for two PWM inverters includes a first and a second electric current detector for detecting AC output electric current of the PWM inverters; a first and a second electric current control circuit for outputting, on the basis of the output electric current, three-phase voltage command values of the corresponding inverters; and a first and a second pulse generating circuit for outputting, on the basis of the three-phase voltage command values, command pulses which controllably turn on and off the corresponding inverters.

Abstract: The performance of AC to DC and DC to DC boost preregulators, and the performance of the equipment of which they form a part, can be improved by means of an adaptive boost switching preregulator which can, when used with a load capable of operating over a range of load voltages, increase or optimize the conversion efficiency and reliability of both the preregulator and the load by adaptively controlling the load voltage as a function of the voltage of the input source. Also, a gain-variable current controller can be provided which allows for accurately controlling the waveform and magnitude of the input current of a switching preregulator as the preregulator load (and hence the input current) varies over a wide dynamic range, yet does so by comparing signals whose magnitudes are essentially independent of the magnitude of the load. In this way, second order effects, which cause degradation in control of power factor in other preregulators as load is decreased, are rendered less significant.

Abstract: A digital controlled inverter (100) for inverting an input signal to an alternating current signal having a clock generator (104) for generating a high frequency clock timing signal and a latch (106) for controlling the passage of the clock timing signal to a power stage (102). The power stage (102), which provides a low distortion alternating current signal, is controlled by the latch (106). A control loop (108) is provided for sensing and converting the alternating current signal to a command signal. The command signal controls the state of the latch (106). The latch (106) is reset at the rate of the clock timing signal and updated with the command signal to provide pulse-to-pulse regulation of the alternating current signal. The inverter (100) comprises a transient response to variations in load proportional to the clock timing signal. In a preferred embodiment, the latch (106) functions as a switch for controlling the power output stage (102).

Abstract: The switching power supply has a high output power, high efficiency and extremely high power factor. The input signal may be AC or DC. A charging circuit operates independently, whereby an average sinusoidal input current is obtained. No separate power factor correction circuit is employed. The switching power supply includes a transformer coupled to ground for providing the output signal. A pair of capacitors is coupled to ground for storing a pair of voltages having opposite polarities. Two switches successively apply the capacitor voltages across primary of the transformer. A rectifier applies the input voltage to one capacitor. The charging circuit inverts a polarity of the input voltage and charges the other capacitor.

Abstract: A ripple feedback circuit for use with a current-sourced rectifier system with a resonant load balancing filter. The ripple feedback circuit eliminates the oscillation of the rectifiers and improves the line-current waveform by sensing the low frequency AC components of the output current and by combining such AC components with the control voltage at the input to the multiplier of the pulse width modulator of the rectifier system. A sample of the rectified line voltage is multiplied by the control voltage less ripple feedback to form the input to the pulse-width modulator which produces the gating waveform for the converter of the rectifier system.

Abstract: An adjustable near unity power factor is achieved while reducing harmonics in a switch-mode power supply by replacing the conventional diode bridge in the front end with an H-bridge driver. Two feedback loops are required, one feedback loop is used to regulate a DC bulk voltage by comparing the DC bulk voltage to a reference voltage and generating an error signal therefrom. A programmable offset is applied to the error signal for adjusting the power factor. A second feedback loop samples and scales the AC input voltage for use as a scaled replica of the input current. The actual input current is then compared to the scaled replica current to produce a second error signal. The two error signals are multiplied to determine the desired input current wherein the desired input current follows the AC input voltage. The desired input current is pulse width modulated by a fixed frequency sawtooth waveform for providing switching signals for controlling the H-bridge driver.

Abstract: A voltage source having a current feedback control loop for enhanced source impedance control of the output of the voltage source. Current feedback is used for a voltage-source amplifier wherein the source impedance is increased/decreased and/or reshaped by the voltage source amplifier's closed-loop gain and the additional current feedback. In particular, the enhanced source impedance control is accomplished through feedback of the output current of the voltage source to an analog error amplifier at an input to the voltage control loop. The output impedance Z.sub.desired is then adjusted in accordance with the equation Z.sub.desired =Z.sub.inv1 {1+G(s) H(s)}, where G(s) is the voltage source amplifier's closed-loop transfer function, H(s) is the transfer function of the output current feedback circuit and Z.sub.inv1 is the original source impedance of the voltage controlled voltage amplifier.

Abstract: There is disclosed a power supply device having a transformer including primary and secondary windings, for generating in said secondary winding a high voltage output corresponding to power supplied to said primary winding, a first switch for on-off switching power supplied to the primary winding of said transformer, a first signal generator for supplying a switching signal at a first frequency to said first switch, a rectifier for rectifying the high voltage output generated in the secondary winding of said transformer, and controller including a second signal generator for supplying a modulating signal at a second frequency lower than said first frequency, for modulating the output of said rectifier by means of controlling the power supplied to the primary winding of said transformer in accordance with said modulating signal.

Abstract: A voltage regulator generates an output voltage between an output line and an output reference voltage from an input voltage between an input line and an input reference voltage. The voltage regulator combines a self excited series resonant oscillator and a switching regulator control circuit. The self excited series resonant oscillator includes an oscillator circuit which produces an oscillating signal. The oscillating signal is rectified to produce a rectified signal. The rectified signal is filtered to produce the output voltage on the output line. The switching regulator control circuit switches the self excited series resonant oscillator on and off at a duty cycle which maintains the output voltage on the output line at a predetermined value.

Abstract: A resistive load, such as a discharge lamp, is connected in a circuit which includes a measuring circuit for measuring the instantaneous power absorbed at the terminals of the load. The measuring circuit includes:measuring means for measuring a low voltage at the foot of the secondary of the transformer which supplies a high voltage supply to the load, such that the measured voltage is an analogue of the voltage across the terminals of the load;a second measuring means for measuring the current passing through the transformer secondary in phase with the measured low voltage, this measured current being an analogue of the current passing through the load;rectifier circuits for rectifying the measured current and voltage; anda processing circuit for processing the rectified signals and to produce in response to them an output signal representing the instantaneous power taken by the load.

Abstract: A power factor correction circuit used to improve the ratio of real power to apparent power in an electric power distribution line containing a source of AC sinusoidal voltage and a load. The circuit includes a frequency and amplitude modulated boost converter forcing the input current to have the same wave shape as that of the input voltage.

Abstract: An improved inverter AC power supply includes a chopper providing a DC voltage from an AC source voltage and an inverter providing from the DC voltage a high frequency AC voltage to a load. The chopper incorporates a pair of first and second switching elements operating to turn on and off for obtaining a periodically interrupted AC voltage which is rectified and smoothened to provide the DC voltage to the inverter. The inverter is arranged to share the first and second switching elements in common to the chopper, and operates to drive the same switching elements for switching the DC voltage in order to provide a desired AC voltage to the load. The power supply is provided with an input power sensor monitoring an input power supplied to the chopper and an output power sensor monitoring an output power from the inverter to the load.

Abstract: A push-pull series resonant converter switching power supply includes an inductive transformer with a primary winding and at least one secondary winding. Two semiconductor switches are interconnected at a circuit node and connected in a half-bridge circuit between an input potential and an input ground potential. A series-resonant circuit connected between the connecting node and the input ground potential includes a capacitor and an inductor connected in series with the primary winding of the transformer. Diodes are connected between the input potential and the input ground potential for preventing a potential at the capacitor from significantly exceeding the input potential. An output is connected to the secondary winding of the transformer for supplying an output voltage. A control circuit triggers the two semiconductor switches with turn-on pulses for regulating the output voltage to a constant value as a function of a load to be connected to the output by variation of a turn-on pulse repetition rate.

Abstract: A control system for poly-phase power inverters that uses feedback sensed voltages and currents to control the switching of solid state power switches in the inverter bridges, producing a nearly ideal sinewave voltage output regardless of load induced or switching harmonic voltages. The system operates in combination with the inverter power switches and switch drivers, particularly incorporating a digital programed optimal controller with virtually no delay in implementing the feedback control, and automatically correcting for any sensed line voltage distortions. The system inherently provides a high recovery speed for voltage transients.

Abstract: A PWM converter apparatus having phase detection means including an error detection protection device for outputting an estimate value as a present phase signal when a phase signal in each computation cycle deviates for a predetermined value or more from the estimate value obtained according to the former phase signal, the frequency of a power voltage, and a computation cycle.

Abstract: In an AC to DC power conversion circuit including a boost inductor connected in series between a full-wave rectifier and a DC load, a switch is connected to selectively shunt boost inductor current from the load. Switch conduction is controlled by a pulse width modulator generating switching pulses at a high fixed frequency. The pulse widths are automatically varied as a function of boost inductor current, load voltage, and an ideal sinusoidal waveform derived from the AC input voltage to force the boost inductor current to closely conform to the ideal sinusoidal waveform and thus minimize harmonic distortion, while achieving load voltage regulation and near unity power factor.

Abstract: A power factor correction circuit in which a divided-down version of a rectified input waveform is sampled approximately at its peak by a sample-and-hold circuit. The peak value is then processed to produce a correction signal which is subtracted from the original divided down rectified signal. This produces a reference signal which is then multiplied by the output of an error amplifier to produce a sinusoidal reference signal for the input current. The output of the error amplifier which is used is that which is sampled periodically when the divided-down rectified signal approaches zero volts. The sinusoidal reference is used by peak and valley comparators whose other inputs come from a current sense amplifier. The outputs of the comparators are used to switch a shunting transistor which controls the input current to achieve near unit y power factor.

Abstract: A corrective device for an inverter output voltage error in which a current sensor is connected in series with the output of an inverter, the polarity of current detected by the current sensor is discriminated by a polarity decision current, a value corresponding to an input D.C. voltage is found by a D.C. voltage sensor, a signal with the polarity of the value inverted according to the discriminated result delivered from the polarity decision current is generted by a polarity inverter circuit, and the signal is applied as a correction signal to the PWM (pulse-width modulation) circuit of the inverter so as to correct the output voltage error.

Abstract: An AC to DC power converter comprises an input filter for filtering the alternating current input and an output filter for filtering and smoothing the direct current power output to a load. The output alternating current of the input filter is rectified and electronically switched by buck and boost switching circuits at a frequency much higher than the frequency of the alternating line current input. The rectified line current is sensed and provided to a control circuit which controls the operation of the buck and boost switching such that the power line current will follow a predetermined reference voltage waveform.

Abstract: The switching power supply has a high output power, high efficiency and high power factor. The input signal may be AC or DC. The input current may be substantial even when the input voltage is 0V (zero volts). In order to minimize any distortions, the average input current is sine wave with DC superimposed thereon. No separate power factor correction circuit is employed. Inrush, surge currents and voltage spikes are completely eliminated.The switching power supply includes a transformer for providing the output signal. At least one capacitor is coupled to ground for storing a voltage. Two switches successively apply voltages of opposite polarities, i.e. the input voltage and capacitor voltage, across primary of the transformer. A charging circuit inverts a polarity of the input voltage and charges the capacitor.

Abstract: An AC to DC power converter comprises an input filter for filtering the alternating current input and an output filter for filtering and smoothing the direct current power output to a load. The output alternating current of the input filter is rectified and electronically switched at a frequency much higher than the frequency of the alternating line current input. The rectified line current is sensed and provided to an integrator circuit whose output provides one control signal input of a pulse width modulator circuit. The pulse width modulator circuit drives the electronic switching an at the same time, provides an output to a discharge circuit for discharging the integrator circuit.

Abstract: A direct coupled switched mode power supply designed for the AC to DC power conversion in for example CAT TV systems and equipment. The power supply is constructed to have a conversion efficiency of between 85 and 90%. It achieves these efficiencies by utilizing a pulse transformer having a duty cycle of greater than 50% in conjunction with an output control circuit, a driver circuit and an output filter circuit all designed to work together to effect increased efficiency.

Abstract: In an ISDN network, terminals connected to an S-bus (4) are fed via this S-bus (4) by a d.c. supply arrangement (6, 7, 20). The d.c. supply arrangement comprises a main supply unit (7) and an emergency supply unit (6) which are coupled with opposite polarity to the S-bus (4) via a coupling circuit (20). Consequently, the emergency supply unit (6) needs to supply only those terminals which are also made suitable for voltages with opposite polarity, and which generally present only elementary telecommunications functions. An electrically arranged coupling circuit (20) includes a monitoring circuit which monitors the value of the main supply unit output voltage and inhibits the output from the main supply unit and connects the emergency supply unit when the output voltage drops below a predetermined threshold.

Abstract: A double-switched flyback power-converter has a primary winding of a power transformer connected between the output terminals of a high voltage DC power supply. A first switch is connected between the positive terminal of the power supply and a first end of the primary winding. A second switch is connected between the negative terminal of the power supply and a second end of the primary winding. During a primary conduction cycle, a current monitor senses the primary winding current and signals a control logic circuit at a predetermined current level. The control logic circuit turns off the second switch, forcing the power transformer into a flyback cycle. During the flyback cycle, energy stored in the primary winding of the power transformer is coupled over to the secondary windings. A major portion of the energy goes to a power output circuit, where it is rectified and filtered for output power use. The remainder of the energy is transferred to a charge pumping circuit at each switch.

Abstract: A highly innovative new technique of developing AC to DC power sources for various applications has been described. Such technique of generating DC power is different from the conventional linear and switching power conversion techniques and this new technology has been called the Solid State Power Supply (SSPS) Technology. The principle of operation depends upon high-frequency pulsed power switching followed by high energy charge-discharge principles as applied to power conversion technology. The use of fast turn-on power MOSFETs enables the application of high frequency switching on this power technology. While the non-isolated SSPS is claimed to be transformerless, the isolated SSPS requires the use of a transformer for input-output isolation. The input and output filtering is reduced tremendously, thereby reducing the size of such power supplies.

Abstract: A switching power amplifier circuit has the functions of a power inverter and a switching amplifier embodied into one integral circuit. Two high frequency switching inverter circuits are connected back to back sharing the same inverter power transformer. One switching inverter circuit processes power from an input rail to an output capacitor while the other switching inverter circuit processes power from the output capacitor to the input rail. The output capacitor voltage is regulated with respect to a signal input in order to obtain the desired output signal waveform. A blocking capacitor in the output absorbs the DC component of the output capacitor voltage and allows a pure AC ringing signal to be applied to the load. In an application as a ringing generator circuit the signal input is supplied by a ringing signal oscillator circuit.

Abstract: A switching type DC/DC converter wherein a switching control circuit is disposed at the primary winding thereof, and a detection signal, in a secondary winding, is insulated by a transformer and fed back to stabilize output voltages. Current consumption is reduced by using a transformer to act as an insulator, and the size of a stabilizing feedback circuit is reduced by using resistors and diodes so that the rate of production thereof is improved. A switching signal in a secondary winding of a main transformer is used as an excitation energy for an insulating transformer of the stabilizing feedback circuit, the excitation energy being supplied through an impedance device. The output voltage supplied to a load is supplied as a stabilizing signal to a primary winding of an insulating transformer by means of the stabilizing feedback circuit.

Abstract: The synchronous switching power supply can be employed in power supply system requiring multiple outputs and extremely high efficiency. The input signal may be AC or pulsating DC. A switching power supply with flyback converter includes an inductor coupled to ground for attaining a current. A switch is coupled between the AC input signal and inductor for selectively applying the AC input signal of one polarity to the inductor. A rectifier is coupled to the inductor for conducting the current and providing a first DC signal. Another converter converts the AC input signal of the opposite polarity into a second DC signal having the same polarity as the first DC signal. The first and second DC signals are applied to a capacitor which provides a DC output signal.

Abstract: An improved regulator circuit for a pulse width modulated power supply having an input switch and a plurality of different output voltages. A precision reference voltage is connected to one or more op-amplifiers and/or divider networks, each of which is connected to an output voltage for translating the outputs to ground when the voltages are properly regulated. A differential amplifier is connected to each of the operational amplifiers and divider networks. When the absolute value of any voltages goes low, the corresponding input to the differential amplifier rises and diverts drive current from an optoisolator for increasing the duty cycle of the input switch.

Abstract: This invention relates to a bi-polar power supply regulator. A regulator is shown and described which prevents undesirable and potentially dangerous power supply build-up in a power amplifier of the standard totem pole configuration. The regulator also enables one to construct a multi-amplifier system in a cost effective manner since the regulator controls the build-up in the bi-polar power supply which is used to drive several power amplifiers in the totem pole configuration.

Abstract: A clocked direct voltage converter has a controlled output at which a controlled voltage is produced. The converter also produces an uncontrolled voltage at an uncontrolled output. The latter voltage, is obtained by coupling to one of the energy storage elements in the converter. In order to avoid the "idling"mode of operation in such a clocked direct voltage converter, a threshold value detector is provided which connects, through a switch, a base load to the controlled output when the uncontrolled voltage output falls below a given threshold.

Abstract: An AC to DC power converter comprises an input filter for filtering the alternating current input and an output filter for filtering and smoothing the direct current power output to a load. The output alternating current of the input filter is rectified and electronically switched at a frequency much higher than the frequency of the alternating line current input. The rectified line current is sensed and provided to an integrator circuit whose output provides one control signal input of a pulse width modulator circuit. The pulse width modulator circuit drives the electronic switching and at the same time, provides an output to a discharge circuit for discharging the integrator circuit.

Abstract: A permanent magnet rotor type electrical alternator-SCR power supply having a unique series resonant LC circuit connected to the alternator and resonant close to the lowest expected frequency of the alternator.

Abstract: The present invention discloses a speed control apparatus for an AC motor which vector-controls, for example, a drive current of the AC motor such as an induction motor, synchronous motor and AC commutator motor with a feedback current control loop providing an inverter utilizing a semiconductor element for power amplification such as power transistor and compensates for non-linear current characteristic of the drive current generated by dead time resulting from ignition delay of a semiconductor element with a current compensation control element provided within the current control loop, thereby controlling the rotation speed and command response speed of an AC motor.

Abstract: An inverter having an output connected to a load through a reactor and an output filter capacitor terminal voltage of the capacitor is monitored, and an interlock operation for interrupting the delivery of the inverter transistor drive signals is released when the terminal voltage does not exceed a predetermined level. When the interlock operation for cutting off the drive signals of the transistors has started and continued for a predetermined time, it is further continued when the terminal voltage of the output filter capacitor does not drop below a set level and is released for the first time when the output filter capacitor is sufficiently discharged to render the terminal voltage the set level or below.

Abstract: A flyback power supply is disclosed which includes a sample and hold feedback path. A pulse width modulation circuit provides control signals for a drive device that determines current excitation pulses for a primary winding of a transformer. A secondary winding of the transformer is connected to a rectifier circuit and provides a DC voltage signal at an output terminal. A selective feedback path is provided between the output terminal and a sense input terminal of the pulse width modulation circuit. The selective feedback path comprises a sample and hold circuit which provides for effectively coupling the output terminal to the sense input terminal at times during the storage of energy in the transformer, corresponding to an increase in transformer flux, and wherein at other times when the transformer flux is decreasing and energy is being transferred from the transformer to the rectifier circuit the feedback path effectively disconnects the output terminal from the sense input.

Abstract: A single phase, full wave diode bridge circuit is connected with a chopper on its DC output side. An output voltage of the chopper is smoothed by a smoothing capacitor and thereafter supplied for a load. A current control apparatus forms a current reference signal which is synchronized with an AC voltage applied to the bridge circuit and has a magnitude corresponding to a current flowing through the load and produces a deviation signal between the current reference signal and an actual AC input current of the bridge circuit. The chopper is controlled in accordance with the deviation signal so that the AC input current follows the current reference signal, whereby the power factor and the waveform of the AC input current in the bridge circuit are improved.