Showing papers on "Switched-mode power supply published in 1975"

High efficiency switching regulator

Abstract: An improved switching regulator converts an unregulated DC voltage into a regulated DC output voltage and maintains regulation over the entire range from maximum load current through zero load current. The improved regulator employs a plurality of series switching paths connected between the unregulated DC input and a summing node at a filter capacitor output. Each series switching path includes a power switching element, a catch diode and a series inductor. The other end of the summing node is connected through a current limiting circuit to the DC regulated output, and at least a portion of the voltage at the summing node is fed to a voltage error amplifier and used to control the duty cycle of the series switching elements. Feedback from the current limiting circuit can override the voltage error amplifier control should the maximum current limit be exceeded. The switching control means employs pulse-width modulation for adjusting the duty cycle of the series switching elements, and the technique of pulse-width modulation employed in the present invention is of the constant frequency, variable "ON" time variety, as known in the art. The switching element control means utilizes a selecting means whereby different ones of the switching elements in different ones of the series switching paths are sequentially selected such that the selected series switching element is always turned on into a non-conducting inductor and a fully-recovered catch diode so as to minimize or eliminate the power loss associated with switch turn-on; the noise usually associated with switching regulators; and the turn-on transient which is often propagated into the supply line in the switching regulators of the prior art, thereby allowing highly efficient and reliable regulation to be maintained at very low values or even no value of load current.

Effect of Unbalanced Voltage on the Operation of Polyphase Induction Motors

Abstract: Three-phase electric power systems generally provide voltage supply at the generating station that is well balanced in both magnitude and displacement. For varying reasons, however, some degree of voltage unbalance occurs at the point of utilization, and, depending upon the amount of unbalance, this can have an adverse effect upon the operation of polyphase induction motors. A major cause of unbalanced voltage at the point of utilization is that single-phase loads on a system are not uniformly applied to all three phases. This is particularly true for some rural electric power systems, and it can also occur in large urban power systems where heavy single-phase demands are imposed by facilities such as extensive shopping plazas. A large manufacturing plant may have well balanced incoming supply voltage, but unbalance can develop within the plant from its own single-phase power requirements if these are not uniformly spread among the three phases. Regardless of the cause, unbalanced voltage is harmful to three-phase induction motors. The paper to follow concentrates upon that aspect of unbalanced voltage.

Transient Thermal Response Measurements of Power Transistors

Abstract: Differences between the measured thermal impedance of power transistors when determined by the pulsed heating curve and cooling curve techniques are discussed. These differences are shown to result primarily because the power density distributions of these devices change as devicesheat; as a result of these changes the heating curve and the cooling curve are not conjugate. It is shown that the cooling curve technique, when the cooling curve is initiated from the most non-uniform steady-state thermal, distribution, (maximum voltage, maximum power) will indicate a larger value for the thermal impedance than will the pulsed heating curve technique, even for pulses in excess of the dc power level. A one-dimensional model for power transistor cooling is described. The theoretical predictions of the model are shown to be in good agreement for practical applications with three-dimensional computer simulations and experimental results. Using this model, it is possible to estimate an average junction temperature and the area of power generation at steady-state. Both TO-66 and TO-3 encased devices of mesa and planar structures were included in this study.

Lamp power supply using a switching regulator and commutator

Abstract: A power supply for an ac metal halide lamp employs a dc regulator in conjunction with a commutator for supplying the regulated dc power to the lamp with alternating polarity. A feedback circuit senses the dc voltage and current fed to the commutator and cooperates with the regulator to provide substantially constant power to the lamp. The commutator switching times are sufficiently rapid so that flickerless light output is obtained.

Pulse width modulated voltage regulator-converter/power converter having push-push regulator-converter means

Abstract: Disclosed herein is an improved pulse width modulated (PWM) voltage regulator-converter system which can function, alone, as a switched voltage regulator system or in combination with a switched power converter, synchronized therewith to form an improved voltage regulator-converter/power converter system. In the pulse width modulated voltage regulator-converter embodiment of the invention, secondary windings of a "current mode" regulator-converter interstage transformer are coupled to regulator-converter power transistors in a push-push circuit configuration. Signals generated by a system clock means and an error signal, derived from the output of an averaging filter, drive a pulse width modulated control means connected to the primary windings of the regulator-converter interstage transformer to thereby increase the maximum regulated output voltage of the voltage regulator-converter system after conditioning in the averaging filter. In the pulse width modulated voltage regulator-converter/power converter embodiment of the invention, the aforementioned output voltage of the voltage regulator-converter system is coupled directly to a switched power converter connected in a push-pull circuit configuration. In turn, additional signals generated by the system clock means switch the power converter in synchronizm with the voltage regulator-converter system.

Ac to dc power supply circuit

Abstract: An electrical power supply circuit for converting alternating circuit power into a direct current output comprises a transformer and rectifier, a filter capacitor across the output terminals and a phase control switching device and a non-saturating inductor in the primary circuit. The circuit arrangement reduces the volt-time integral of the transformer and allows its core to be made of a smaller size, in comparison to the transformer cores of previously known power supplies, without danger of saturation. Other advantages such as low RFI, reduced transformer wire size and overload current protection are obtained. A commutator circuit may also be provided for turning off the phase control switching device before the end of the associated half cycle of input voltage to further reduce the transformer volt-time integral and to accordingly allow a further reduction in its core size.

Automotive power supply

Abstract: An automotive power supply comprising a generator which produces a voltage when an engine is in operation, a main battery which drives a starter motor, an auxiliary battery which functions as a power source for direct current equipment in a vehicle, and a d-c voltage booster circuit which boosts the voltage produced in the generator to supply the auxiliary battery; wherein, in charging the main and auxiliary batteries in parallel by the voltage produced in the generator, the supply voltage to the auxiliary battery is boosted by compensating the line voltage drop between the generator and the auxiliary battery.

PA protection circuit for a single sideband radio

Abstract: A directional power detector mounted between the power amplifier and antenna which supplies audio frequency output signals indicative of forward and reflected power, circuitry for summing and converting the output signals from the power detector means to a DC potential proportional to the magnitude thereof and a transistor connected in shunt at the input of the power amplifier and controlled by the DC potential for controlling the peak envelope power at the antenna.

Series capacitors in power systems

Abstract: The paper reviews the experience obtained with series-compensated power systems, particularly in Sweden, where internally fused capacitor units and simple system designs have contributed to the the good results. It also introduces new approaches for meeting future demands, e.g., optronic protection and a high-speed flip-flop reinsertion system.

Power supply for high power loads

Abstract: A power supply capable of transferring power at high current and voltage levels to a load which may be highly inductive. The power supply includes an inverter for receiving DC power and inverting it to an AC intermediate signal. The intermediate signal is rectified by a converter to provide a DC output voltage to a load. Commutation of the controlled rectifying devices within the inverter and converter are provided by capacitors connected across the output terminals of the inverter. The DC output voltage provided to the load is controlled by the frequency of the firing signals provided to the controlled rectifying devices within the inverter. A large energy storage inductor, which may be superconductive, is connected to the inverter and may be utilized to provided the pulses of power required by the load. A converter connected to an AC power system is provided to supply external power and to recharge the current flowing in the energy storage inductor. Power may be transferred reversibly, from the energy storage inductor to a load inductor and back again.

High efficiency low-loss power supply

Abstract: A synchronized power supply for use with display systems and data processing equipment in general in which information is displayed on a screen such as a cathode ray tube in which the power supply is synchronized to the display such that internal synchronization is maintained regardless of variation in external synchronization. A unique converter arrangement transfers regulated power to the loads at high efficiency such that both improved power supply and display operation result.

Constant power regulator for xerographic fusing system

Abstract: A constant power regulator for a xerographic fuser in which power control is achieved by taking the sum of the load voltage and current. The regulator includes an operational amplifier connected as a voltage adding circuit. The operational circuit amplifier of the power regulator adds the voltage drop across the fuser and a reference resistor connected in series with the fuser and the voltage drop across the fixed reference resistance which represents the current flow through the fuser. The output of this summing circuit is detected by a photodetector that electrically isolates the power regulator from a voltage regulator which has an output for controlling the power supply to the fuser through, for example, a triac, controlled as a function of the power supply signal and the detected voltage generated by the power regulating circuit.

Effects of voltage and reactive power constraints on power system reliability

Abstract: The paper deals with a method for the reliability evaluation of a power generation and transmission system, when considering, together with the constraints on the active power capability of elements, the voltage constraint in network nodes. The approach suggested is an extension of a previous method for the reliability evaluation when considering only the active power capability constraints. The method is based on the approximate evaluation, by means of linear computation methods, of the reactive power flows and of the consequent voltage values in network nodes. This evaluation is performed starting from the approximate evaluation of the active power flow derived with the classic method of d.c. load-flow computation. The system performance, as a consequence of voltage constraints, is quantitatively evaluated by means of two indices: the first being the power disconnected in the nodes as a consequence of unacceptable voltage values or lack of reactive generation, the second being the irregularity of the voltage Service.

Transient voltage protection circuit for a DC power supply

Abstract: A protection circuit for a DC power supply which protects the power supplynd its load against transient over voltages which may exist at the input to the power supply. The device also includes circuitry for protection of the power supply elements against short circuiting due to load failure. The circuit provides rapid and positive disconnect at the power supply input when a transient overvoltage is impressed, and an effective shut down of the entire power supply in the event of a short-circuit load. The device includes a transient voltage sensor network connected to a temperature stabilized powerload disconnect switch utilizing semi-conductive elements capable of extremely high switching speeds. The circuit switching is sufficiently fast such that the load operation and performance is not noticeably affected in the presence of fast transients impressed at the input to the power supply. Power dissipation in the device is confined to extremely fast turn on and turn off switching losses and saturation losses.

A controllable secondary multikilowatt dc current source with constant maximum power factor in its three phase supply line

Abstract: A type of industrial size dc converters for submegawatt applications is described and illustrated with the characteristics of a small scale 10 kW model. High conversion efficiency near 97 percent is maintained at full power and with an internal frequency of operation near 10 kHz. The system is characterized by the behavior of a true current source with inherent short circuit capability of its output terminals. All power is processed via a firmly controlled high Q series resonant circuits. Feasibility of power densities in excess of 1 kW/kg component weight is demonstrated. This high power density reflects itself in low quantities of material needed for construction of these systems. Operation of the dc converter as part of a rectifier-filter-converter system, powered from a three phase supply line is described. Test data demonstrate a high power factor p.f. ≃ 0.95 for all conditions of converter loading. Data obtained from a thyristor bridge-filter system are presented and subjected to comparative analysis.

High power factor ac to dc converter circuit

Abstract: A high power factor AC to DC converter circuit includes a rectifier circuit coupled to an AC potential source and providing a full-wave rectified pulsating DC potential to a switching regulator circuit with a radio frequency current filter connected in circuit with the rectifier and switching regulator circuits to provide a pulsating DC current in phase with and of at least 50% duration of said pulsating DC potential whereby a power factor of at least 90% is effected.

Automatic V-I crossover regulator

Abstract: In order to achieve the capability to operate a plurality of identical power supplies in parallel, whereby the drawbacks of the conventional master-slave regulator relationship are avoided, the regulator of each power supply is provided with a load current sensor and a secondary differential amplifier circuit responsive to a predetermined load current for controlling the normal reference voltage supplied to the primary, voltage regulating differential amplifier. As a result of the inevitable, within-tolerance differences in the characteristics of two paralleled regulators, one supply will assume constant current operation at the predetermined load current while the other supply will operate at constant voltage and will carry the remainder of the actual load current. As many identical power supplies as necessary for a given application may be operated in parallel, and a single one will automatically operate in the constant voltage mode while the rest operate in the constant current mode.

Power supply with chopping circuit

Abstract: An improved power supply apparatus for providing a stabilized low voltage d.c. output from the a.c. mains, comprises two distinct chopper stages, each having its regulation control loop which operates by duty cycle control. The first loop includes a current limiter and provides a rough regulation of the output voltage as a function of the mains variations, whereas the second loop provides a fine regulation of the output voltage as a function of the load variations, and isolation with respect to the load.

Standby power supply system

Abstract: A standby power supply system utilized for continuously supplying alternating current power at a regulated value to a load independent of the line power amplitude of continuity. The standby power supply includes an inverter utilizing a direct current source. Direct current feedback circuitry is provided for improving the AC - DC synchronization, minimizing the drain on the source and for holding the direct current relatively constant thereby reducing the requirements of the direct current source.

Geophysical energy source utilization circuit

Abstract: A conversion means converts the energy available from a source, such as the wind or sun, into a corresponding amount of d.c. electrical power. A switching circuit, typically a thyristor bridge, is connected between the conversion means and an a.c. load and across a.c. power mains energizing the load. The switching circuit is operable to periodically connect the conversion means to the a.c. load in a power supplying manner. The a.c. mains impart suitable voltage and frequency characteristics to the electrical power so supplied. In the event the supplied power exceeds the power required by the a.c. load, the difference is taken by the a.c. power mains.

Modular constant current power supply

Abstract: A power supply employing a clock-driven D.C.-A.C.-D.C. converter having a current transformer in the A.C. section to develop a trapezoidal current feedback pulse train which is then converted to a trapezoidal voltage pulse train. A comparator compares the trapezoidal voltage pulse train to a voltage reference level set such that it is normally crossed by the ramp portion of each trapezoidal voltage pulse. Upon occurrence of a ramp crossing, which varies with the level of the output current, a control pulse is produced by the comparator and supplied to gating logic which develops driving pulse trains for the D.C.-A.C.-D.C. converter and cuts off each driving pulse upon occurrence of a control pulse. The resulting power supply constitutes a voltage-controlled constant current power supply which may be connected with an arbitrary number of other such supplies to a power bus and to a common feedback-controlled voltage reference source.

Drive circuit for power switching device

Abstract: A transformer-coupled transistor base drive circuit is disclosed wherein the transformer primary control circuit includes a switching transistor, a bias supply, and a RC biasing network arrangement. The biasing arrangement is designed to ensure that the transformer core will never enter the positive saturation region of its hysteresis characteristic; regardless of variations in the power transistor duty cycle. The base drive circuit also features provision of high sweep-out current in the power transistor base during turn-off, reverse base-emitter voltage during the power transistor off state, and regenerative current drive to minimize storage time and to control the bias power drain.

Wide dynamic current range switching regulator

Abstract: A switching regulator is adaptable for connection to a DC power source to serve as a power supply. A self-oscillating switching regulator has an output voltage feedback circuit connected thereto which interrupts the self-oscillating circuit when the output voltage rises above a prescribed level. The current that flows through a power switch of the regulator is sensed and when it gets beyond a predetermined amount, a Schmidt trigger circuit is turned off. The Schmidt trigger circuit then turns off the power switch, permitting the inductor in the switching regulator circuit to supply current to an output filter capacitor. When the voltage across the capacitor builds up to a prescribed level, the feedback circuit detects the level and deactivates the Schmidt trigger which turns off the power switch.

Triggered transistor switching regulator

Abstract: A switched-mode power supply in which disturbing oscillations which are produced by the associated (auto) transformer are eliminated by means of a clipping circuit, a supply voltage being generated for the driver stage which controls the switch. This measure saves an expensive resistor and ensures a better operation of the circuit at a varying input voltage.

Power supply for realistic control of model railroad engines

Abstract: A power supply for realistically controlling a model railroad engine. For engine acceleration, the power supply provides an output signal having a linear ramp with pulses superimposed thereon. For constant speed operation, the supply produces a constant output voltage. For deceleration, the power supply produces a decreasing linear ramp signal with pulses superimposed thereon. Adjustment circuitry is provided for modifying the output waveshape so that realistic control can be achieved for different model engines having different operating characteristics.

Distributed power switch for modular systems

Abstract: Power is fed from a pair of power supplies to each one of a plurality of load circuits through a distributed power switch. A plurality of switch means are each associated with a respective one of the load circuits for connecting it to one of the power supplies in a primary manner and to the other power supply in a secondary manner. Upon failure of its primary source of power, each switch means is effective for automatically connecting its load circuit to its secondary source of power.

Fast turn-off circuit for power transistor

Abstract: In a system for energizing the load from a voltage source there is provided a power transistor and regenerative feedback means coupled between a collector and base of the power transistor for only feeding back to the base a signal responsive to an increasing potential sensed at the collector to reduce the time necessary to turn off the power transistor.

Power on demand beam deflection system for CRT displays

Abstract: A cathode ray tube linear beam deflection system capable of operation over a wide range of beam deflection rates providing automatic power supply voltage switching to maintain linear operation and provide minimum power dissipation. Information for the automatic switching is obtained by continuously monitoring the yoke voltage, the power supply voltage being switched to a voltage of higher magnitude when the yoke voltage exceeds a predetermined level and returned to the power supply voltage of lower magnitude when the higher magnitude voltage is no longer required.

Solid state power controller

Abstract: A solid state control system for controlling a high voltage primary power pplied to a plurality of power supplies by means of a TTL voltage level. Circuit means are provided to sense the power supply whose DC voltage goes to zero volts due to circuit anomalies, or other reasons. Upon sensing the anomaly the indicator means indicate via a storage device which power supply has failed, before interrupting the primary power.