Showing papers on "Switched-mode power supply published in 1989"

Power Electronics: Converters, Applications and Design

Abstract: Partial table of contents: Overview of Power Semiconductor Switches Computer Simulation of Power Electronic Converters and Systems GENERIC POWER ELECTRONIC CIRCUITS dc--dc Switch-Mode Converters Resonant Converters: Zero-Voltage and/or Zero-Current Switchings POWER SUPPLY APPLICATIONS Power Conditioners and Uninterruptible Power Supplies MOTOR DRIVE APPLICATIONS dc Motor Drives Induction Motor Drives Synchronous Motor Drives OTHER APPLICATIONS Residential and Industrial Applications Optimizing the Utility Interface with Power Electronic Systems SEMICONDUCTOR DEVICES Basic Semiconductor Physics Power Diodes Power MOSFETs Thyristors Emerging Devices and Circuits PRACTICAL CONVERTER DESIGN CONSIDERATIONS Snubber Circuits Gate and Base Drive Circuits Design of Magnetic Components Index

An active power factor correction technique for three-phase diode rectifiers

Abstract: A novel active power factor correction method for power supplies with three-phase front-end diode rectifiers is proposed and analyzed. The implementation of this method requires the use of an additional single switch boost chopper. The combined front-end converter draws sinusoidal AC currents from the AC source with nearly unity input power factor while operating at a fixed switching frequency. It is shown that when the active input power factor correction stage is also used to regulate the converter DC bus voltage, the converter performance can improve substantially in comparison with the conventional three-phase AC-to-DC converters. These improvements include component count reduction, simplified input synchronization logic requirements, and smaller filter refractive components. Theoretical results are verified experimentally. The proposed method has the disadvantage of substantially increasing the current stresses of the switching devices and the high-frequency ripple content of the prefiltered AC input currents. >

A survey of neutral currents in three-phase computer power systems

Abstract: Neutral current in three-phase power systems is often thought to be only the result of the imbalance of the phase currents. With computer systems, very high neutral currents have been observed even when the phase currents are balanced. Measurements from a sample of computer power systems in the United States are presented to determine the extent of the neutral current problem. The author explores the cause of high neutral currents in three-phase computer power systems, potential problems, and recommended remedies. It is found that, while very high neutral currents are possible due to the additive nature of triple harmonic currents, a low percentage of data-processing sites in the US are actually experiencing neutral currents in excess of the rated phase current. However, recent trends in computer systems make high harmonic neutral currents more likely. Power system problems associated with high harmonic neutral currents include overloaded transformers, voltage distortion, and common-mode noise. It is suggested that whenever three-phase, wye power systems are used to supply power to computer systems or other similar electronic loads, the power system design should allow for the possibility of high harmonic neutral current to avoid potential problems. >

Fluorescent lamp controllers

Abstract: An electronic controller for fluorescent lamps includes a DC to AC converter which supplies high frequency current to the lamps and a preconditioner stage which includes a switched mode power supply connected to accept line power and produce a DC input for the DC to AC converter. The switched mode power supply and the DC to AC converter are synchronized to operate in a fixed phase relationship and/or at the same frequency.

Switch-mode power supply with burst mode standby operation

Abstract: In a switch mode power supply, a first switching transistor is coupled to a primary winding of a transformer for generating pulses of a switching current. A secondary winding of the transformer is coupled via a switching diode to a capacitor of a control circuit for developing a control signal in the capacitor. The control signal is applied to a mains coupled chopper second transistor for generating and regulating supply voltages in accordance with pulse width modulation of the control signal. During standby operation, the first and second transistors operate in a burst mode that is repetitive at a frequency of the AC mains supply voltage such as 50 Hz. In the burst mode operation, during intervals in which pulses of the switching current occur, the pulse width and peak amplitude of the switching current pulses progressively increase in accordance with the waveform of the mains supply voltage to provide a soft start operation in the standby mode of operation within each burst group.

CMOS power-on reset circuit

Abstract: The output signal of a CMOS power-on reset circuit changes state upon detecting a predetermined threshold of the power supply voltage during the start-up transient. During the power-up of the power supply voltage, the output signal of the power-on reset circuit ramps up with the power supply voltage until the latter reaches a first predetermined level whereat a control signal begins to track the increasing power supply voltage, less two diodes potentials. Upon reaching the turn-on potential of a transistor, the control signal activates an inverter to substantially reduce the output signal signifying that the power supply voltage level is sufficient for the operation of external circuitry. The output signal then disables the current flowing through the power-on reset circuit to save power consumption.

System for regulating the operating point of a direct current power supply

Abstract: A system for regulating the operating point of a direct current power supply comprising a current generator system connected to a pulse width modulation converter includes a circuit for sampling and measuring the voltage and the current supplied by the current generator. A threshold detector circuit responding to stalling of the converter supplies a logic signal representing the stalled or non-stalled state of the converter relative to threshold values. A regulation loop includes a switching device for inverting the sign of the error signal so that the operating point can be moved towards the maximum power point on the output current-voltage characteristic of the current generator. The system is applicable to regulation of the electrical power supply circuits of spacecraft, space probes, satellites and the like.

A line voltage regulator/conditioner for harmonic-sensitive load isolation

Abstract: A technique is presented for the isolation of harmonic-sensitive loads from harmonic-producing loads, such as rectifiers and power converters. The solution, referred to as a line voltage regulator/conditioner (LVRC), utilizes a combination of a series and a parallel active power filter. The series filter isolates the sensitive loads on the output side of the LVRC from the nonlinear, distortion-producing loads on the input side by correcting for the harmonic voltage distortion present at the input. In addition, the series filter is utilized to regulate the output voltage. The parallel filter acts to generate the harmonic current required by the loads connected on the output side, therefore reflecting a linear load to the source. >

Switching power supply device

Abstract: PURPOSE:To cope with a wide range of input voltage by providing a tap on the primary winding of a transformer and making a tap changing-over when DC supply voltage is less than a specific value. CONSTITUTION:An output transformer 11 has a primary winding 11p, a secondary winding 11s and a feedback winding 11b. A tap 11t is provided on the primary winding 11p, and connected to a positive side terminal of a DC power supply 12 through a normally open type relay switch 14. Accordingly, the primary winding 11p changes the number of windings according to ON/OFF of the relay switch 14. In addition, DC power is supplied to a load 17 from the secondary winding 11s through a rectifying diode 15 and capacitor 16. A supply voltage detection circuit 25 is provided between both positive and negative bus bars of the DC power supply 12, and an excitation coil 32 for the said relay switch 14 is driven through a voltage comparator 26. Accordingly, by connecting to the tap 11t of the primary winding 11p when the voltage of the DC power supply 12 is less than a specific value, the number (N) of the primary windings is reduced, and discharged energy can be maintained at the same level.

Brushless doubly-fed generator control system

Abstract: An energy conversion generation system receives energy from a resource and converts the energy into electrical power for supply to a polyphase electric power grid operating at a system frequency A prime mover driven by the resource energy and a converter, such as a power electronic converter, for produces excitation power from power received from a converter power source A brushless doubly-fed generator has a rotor with rotor windings and a stator with stator windings comprising first and second polyphase stator systems The rotor is driven by the prime mover The first stator system supplies the electrical power to the grid, and the second stator system receives the excitation power from the converter A sensor senses a parameter of the electrical power output supplied to the grid and produces a sensor signal corresponding to the sensed parameter A controller controls the converter in response to the sensor signal The controller establi This invention was made with government support under Grant No 79-85BP24332, awarded by the Bonneville Power Administration The United States government has certain rights in this invention

Large scale integrated circuit for low voltage operation

Abstract: Disclosed is a one-chip ULSI which can carry out fixed operations for a wide range of power supply voltages (1 V to 5.5 V). This one-chip ULSI is composed of a voltage converter circuit(s) which provides a fixed internal voltage for a wide range of power supply voltages, an input/output buffer which can be adapted to several input/out interface levels, a dynamic or volatile RAM(s) which can operate at a power supply voltage of 2 V or less, etc. This one-chip ULSI can be applied to compact and portable electronic devices such as a lap-top type personal computer, an electronic pocket note book, a solid-state camera, etc.

Synthesis of load-independent switch-mode power converters

Abstract: A method of synthesizing load invariant switch-mode power converters comprising positive current feedback of an exactly specified nature and value of its transfer function is presented. The system transfer function independent of load is realized while the stability and dynamics of the system are controlled by an additional voltage loop. The development of the proposed method, computer simulation results, and experimental results are also presented. >

Switched power supply with current mode regulation

Abstract: A switched mode power supply operating with current mode regulation comprises an output switch coupled to a first winding of a transformer and to a source of input supply voltage. The switch is responsive to a control signal for initiating a pulse width modulated pulse voltage in a second winding of the transformer. A supply circuit coupled to the second winding generates an operating voltage. A feedback signal source monitors both current flowing through the first winding and the operating voltage. A control circuit coupled to the feedback signal source includes an oscillator for generating the control signal at a substantially constant frequency during normal operation and at a variable frequency during abnormal operation. The control circuit is responsive both to the current and to variations of the operating voltage over a regulating range, in a negative feedback loop. The control signal varies the on-time conduction of the output switch in each cycle to stabilize the operating voltage. The oscillator has a frequency control responsive to variations of the operating voltage outside of the regulating range, in a positive feedback loop. The on-time conduction of the output switch is limited to a maximum value by comparing the current to an error signal related to the operating voltage. The error signal varies when the operating voltage is within the regulating range but is limited in magnitude when the operating voltage falls below the regulating range. A DC feedback voltage forms a part of both the negative and positive feedback loops.

High voltage high power DC power supply

Abstract: A high voltage, high power DC power supply includes a single turn primary winding driven through a resonating capacitor by an AC source having a frequency in excess of about 100 kHz The primary winding includes a pair of concentric cylindrical metal walls having opposite ends electrically connected to each other A volume between the walls includes plural secondary winding assemblies, having different axial positions along the walls Each of the assemblies includes an annular magnetic core surrounding the interior wall, a winding on the core and a voltage doubler rectifier DC voltages developed across each secondary winding assembly by the rectifier are added together to provide the high voltage, high power output The power supply energizes an X-ray tube having a grounded anode and a cathode at a DC voltage of approximately -150 kV, with a power requirement of between 15 and 60 kW The power supply and X-ray tube are mounted on a rotatable gantry including a slip ring assembly for coupling a relatively low voltage excitation source to the power supply

Current mode switching regulator with programmed offtime

Abstract: A current mode switching regulator power supply with an improved regulator system achieves a constant operating period by predetermining the off time of the switching transistor. The off time is programmed by the input and output voltages acting on a resistor-capacitor timing circuit enabled by a current mode controller.

A new topology for single phase UPS systems

Abstract: A power converter topology suitable for online single-phase uninterruptible power supply (UPS) systems is presented. The converter uses only four switches, five if a low-voltage battery and resonant link operation are required, to realize very desirable features. These include independent control of the input and output currents a common neutral connection, line conditioning, sinusoidal input currents independent of load current, and battery charge/discharge regulation. Detailed simulation results and experimental results are included. >

Chaos: a real phenomenon in power electronics

Abstract: An introductory tutorial on chaotic behavior in DC-DC convertors is presented. Chaos is characterized by an emipirical spectrum which has a continuous component, and may even have no discrete components. Chaotic behavior frequently occurs when a power converter operates in a protective mode such as in a short-circuit or overload condition. Chaotic behavior in power converters is described in terms of phase-plane (state-space) trajectories. A description is given of a particular form of buck regulator circuit without PWM (pulse-width modulation) drive and without current sensing, i.e. a form of ripple-regulator. Simulation and experimental data for the circuit are presented and discussed. Two other similar circuits exhibiting chaotic behavior are also considered. >

Universal power supply, independent converter stages for respective hardware components of a computerized system

Abstract: In a point of sale terminal it was desired to incorporate a variety of input/output devices, e.g. CRT display, disk drives and a printer in a compact hosuing, e.g. about 16 inches wide by 12 inches in depth (without frontally projecting keyboard) by about 11 inches high. The illustrated switching power supply occupies a rectilinear space of less than 155 cubic inches and has the capability of operating from either 110 or 220 VAC, 50 or 60 hertz, or from battery power, with essentially constant volt-second product, while supplying a maximum average output power greater than 120 watts, and a peak output power of greater than 280 watts.

Hybrid high speed voltage regulator with reduction of Miller effect

Abstract: A linear regulator employing a field effect transistor (FET) pass element to supply a pulsed load is programmed by a cooperating switching regulator such that an increased voltage differential is maintained across the FET to reduce response time during the leading edge of the load pulse and to thereafter reduce the voltage differential to achieve reduced power consumption and increased efficiency during the remainder of the load pulse.

Method and apparatus for controlling a power converter.

Abstract: The invention controls a power converter (34) for interchanging power between first and second electric sources (30, 32). In the preferred embodiment, one of the power sources is a high power DC source (32), such as storage batteries, and the second source is a standard utility bus (30). A static power converter (34) controls power interchanges between the two power sources (30, 32) and a controller responsive to the utility voltage, a command specifying the required power interchange, a feedback responsive to the actual power interchange, a command specifying the reactive power interchange, and a feedback specifying the reactive power interchange to generate signals which control the static converter to assure the required power interchange.

Analysis and design of a novel 3- phi solid-state power factor compensator and harmonic suppressor system

Abstract: A novel three-phase solid-state power factor compensation scheme is presented and analyzed. This scheme employs a PWM voltage-source inverter and has two important features. First, it can maintain a near-unity mains input power factor without sensing and computing the associated reactive power component, and second, it can substantially reduce any line current harmonics generated by nonlinear types of load. The proposed scheme is discussed in terms of principles of operation, power system design, and analysis under unbalanced operating conditions. Predicted results are verified experimentally. >

Automatically switching multiple input voltage power supply

Abstract: A power supply which automatically adapts to different input power sources. A double pole, double throw, latching relay switches the primaries of the rectifier transformer to a series or to a parallel configuration depending upon the output voltage of the rectifier, thus adapting the circuit to either a nominal 220 VAC source or a nominal 120 VAC source. The control circuit also derives power from the rectifier transformer and is designed to operate even under the worst possible undervoltage or overvoltage conditions. The additional choice of 24 VDC power is available by the use of a diode OR circuit. When a 24 VDC source is connected to the DC input, it is also connected to the rectifier output through a diode, so that power is furnished to the load by whichever source has the higher voltage. In this configuration, a battery pack can be connected to the DC input to supply automatic backup power.

Electronic wristwatch with generator

Abstract: An electronic wristwatch including an a.c. generator having an output which is rectified using a half-wave rectifier. The half-wave rectified output of the generator is stored in a capacitor serving as a secondary power supply. Booster circuitry is operable for increasing and decreasing the voltage of the secondary power supply which is then applied across an auxiliary capacitor used for powering the wristwatch. Additional circuitry provides a suitable voltage across the auxiliary capacitor for driving the watch when the voltage across the secondary power supply is at or below a predetermined level. A pair of detecting circuits detect the maximum and minimum permissible voltage levels of the secondary power supply and auxiliary capacitor.

Dual switched mode power converter

Abstract: A dual power converter is introduced which addresses the problem of output ripple and switching losses in a switched power converter. One stage of the power converter is a conventional PWM (pulse-width modulated) converter, and the other stage is a linear source. The linear source controls the voltage directly, and the output current of the linear stage is used to generate the control signal for the switching stage. This scheme is modeled as a two-stage control system, and the overall response is obtained in terms of the individual transfer functions. The PWM converter supplies most of the current, while the linear source supplies the reverse of the ripple current. Two DC-to-DC buck converters have been designed and implemented, giving excellent ripple suppression and high efficiency at very low switching frequencies. >

Digital input power supply and method

Abstract: A full-wave rectifier circuit is coupled to a pair of differential signal lines emanating from a computer. The differential signal lines which carry digital data information having a serial protocol scheme is tapped by the full-wave bridge rectifier to provide a power supply voltage to power various circuits coupled to the power supply. This scheme permits an interface unit to a serial protocol scheme of a computer to power itself from the data lines.

Towards a zero-output impedance UPS system

Abstract: A categorization of loads requiring clean uninterruptible power is provided, a thorough analysis of their effects is given, and presently used partial solutions are examined. The topology of a low-impedance 3- phi high-power inverter stage, designed to alleviate substantially the current difficulties faced by interruptible power supplies (UPSs) when dealing with unbalanced and/or nonlinear loads, is described. On the basis of theoretical and extensive experimental results, it is concluded that the low-output-impedance 3- phi UPS presented performs well under both unbalanced and nonlinear load application. >

Parallel electric power supplies with current sharing and redundancy

Abstract: An electric power system having power supplies connected in parallel to a common bus includes a voltage feedback and current feedback loop for each supply A voltage feedback signal and a current feedback signal are combined with a reference signal to produce an error signal The output voltage of each supply is controlled in response to its corresponding error signal, to achieve current sharing and redundancy without interconnections among the control circuits of the various supplies

EL operating power supply circuit

Abstract: In a power supply circuit for operating an electroluminescent (EL) element comprising a DC power supply, an inverter connected across the power supply, and the EL element connected to the inverter, an inductor is inserted between the inverter and the EL element wherein an AC voltage is applied from the inverter through the inductor to the EL element to emit light. Another EL operating circuit includes a DC power supply, an inverter, a transformer, and a bipolar capacitor connected in this order and an AC power output on a secondary winding of the transformer is applied to an EL element to generate light. Both the circuits enables a noticeable luminance increase and power saving.

Regulator for inductively coupled power distribution system

Abstract: A regulator circuit for use with a connectorless power supply system in which power is inductively supplied to a plurality of remote loads. A sinusoidal current, at a frequency of 38 kHz, is provided by a power distribution system (10), and circulates through a supply loop (68), which is disposed under the floor of an aircraft cabin. Three parallel connected capacitors (78, 80, and 82) and a multi-turn coil (70) that is inductively coupled to the supply loop comprise a resonant tank circuit in which current circulates. The voltage developed across the tank circuit is half wave rectified, filtered, and supplied to a load connected circuit. An op-amp (134) compares the potential across the load to a regulated voltage. The output of the op-amp is used to control the period of time during which an N channel FET (96) shunts current to regulate the output voltage. Because the N channel FET is only permitted to shunt current to control the output voltage when the potential of the AC current flowing in the tank circuit passes through zero with a negative slope, the regulator circuit produces minimal EMI. The regulator circuit controls the output voltage with respect to variations in the inductive coupling between the supply loop and the pickup coil, and with respect to variations in the connected load.

Current limited quasi-resonant voltage converting power supply

Abstract: A voltage converting power supply having current limiting characteristics wherein a flyback converter is operated in a load dependent half-wave mode. Constant pulse width switching at a variable rate is utilized for regulation and, by setting the maximum switching frequency, current limiting is achieved.