Showing papers on "Switched-mode power supply published in 1987"

Modern power devices

Abstract: Carrier Transport Physics Breakdown Voltage Power Junction Field-Effect Transistors Power Field-Controlled Diodes Power Metal-Oxide-Semiconductor Field Effect Transistors Power MOS-Bipolar Devices New Rectifier Concepts Synopsis References Index

Topics in Multiple-Loop Regulators and Current-Mode Programming

Abstract: Some general considerations about multiple-loop feedback are discussed, and it is concluded that incorporation of a current-programmed power stage into a ``new'' power stage model is both justified and useful. A new circuit-oriented model of the current feedback path is derived which augments the well-known power stage canonical circuit model. The current loop gain, though wide-band, is always stable if the conventional stabilizing ramp is employed but has a relatively small low-frequency value. Consequently, the ``new'' power stage is more usefully modeled by a y-parameter model in which the current loop is not explicit. Expressions for the y parameters are given that are extensions of those previously derived. Another form of the model resembles the original canonical form for duty ratio programming, and shows that current programming effectively introduces lossless series damping that separates widely the two poles of the power stage LC filter. Therefore, although current programming tends to make the power stage output behave as a current source, the contol-to-output voltage transfer function exhibits, in addition to the familiar dominant pole, a second pole at the current loop gain crossover frequency, which may lie anywhere from one-sixth to two-thirds of the switching frequency.

Integrated uninterruptible power supply for personal computers

Abstract: A method and apparatus for providing uninterrupted DC and AC power for a desktop personal computer is described. The source of the uninterrrupted DC and AC power is derived from an integrated power supply that is sized to fit within the existing housings of most desktop personal computers as a plug-in replacement for existing power supplies. A high degree of efficiency is obtained using an integrated design with the main power conversion derived from a DC/DC dual primary resonant converter. The main primary of the resonant converter is driven from a high voltage DC bus which is supplied from AC mains when available. When the AC mains is unavailable, the second primary of the DC/DC dual primary resonant converter receives power from a low voltage battery source. Secondaries of the converter produce low voltage DC for driving the personal computer, high voltage DC for augmenting the high voltage DC bus, which in turn is used to drive a DC/AC inverter for supplying uninterrupted AC voltage for powering peripherals such as a monitor, printer, etc. A medium-voltage secondary is also sourced from the converter which drives a battery charger to recharge an internal battery pafck upon restoration of the AC mains.

Start circuit for generation of pulse width modulated switching pulses for switch mode power supplies

Abstract: A start circuit for starting the generation of pulse width modulated switching pulses is disclosed for use in a DC/DC switching converter power supply. The starting circuit is responsive to the initiation of a DC voltage source and starts the operation of a pulse generator. The starting circuit also includes a relaxation oscillator connected to the DC voltage source for periodically generating a start pulse at a predetermined frequency. Ongoing power is coupled to the pulse generator once the generator begins operation. The relaxation oscillator is selectively disabled when the pulse generator is powered by the ongoing power supplied by the power supply during normal operation. The start circuit further includes a delay function for delaying the disabling of the relaxation oscillator for a preselected period after shutdown of the power supply and includes a rapid start function for reducing the time between restoration of input power and the operation of the start circuit.

Uninterrupted power supply system

Abstract: A power supply system for providing uninterrupted AC power includes a first input port to which to couple AC input power at a specified RMS voltage level from a primary power source, a second input port to which to couple DC input power at a specified voltage level from a backup power source, and an output port to which to connect a device to be powered. A fullwave rectifier generates a first direct current from the AC input power, and up-converter generates a second direct current from the DC input power at an RMS voltage level approximately equal to that of the AC input power, and a switching arrangement couples a selected one of the first and second direct currents to the output port according to whether the AC input power is stabilized or interrupted, so that the flow of current to the output port is periodically reversed thereby generate AC output power. Switching may by synchronized with each zero crossing of the AC input power. A microprocessor in one form of the invention generates a reference waveform, compares it to the waveform of the AC input power, and selects one of the first and second direct currents according to whether the AC input power is interrupted or stabilized.

Switching regulator with rapid transient response

Abstract: A switch-mode power supply includes the series combination of an inductor and a controllable switch adapted to be coupled to a voltage source for producing a succession of increasing and decreasing ramp currents through the inductor. The average value of the ramp currents is controlled by a feedback loop. A second controllable switch arrangement is coupled for causing the current leaving the inductor to recirculate through the inductor during those intervals in which the second switch is conductive. An integrator is coupled to the inductor for integrating ramp current from the inductor during those intervals in which the second switch is nonconductive, for generating load voltage. A second feedback arrangement senses the load voltage and controls the average conduction of the second switch to control the load voltage. In one embodiment, an inverter receives ramp current from the inductor and generates alternating current, which are transformed and rectified before application to the integrator.

Winchester disk drive motor circuitry

Abstract: An improved switching regulator .Iadd.DC-DC power converter or .Iaddend.power supply with a variable duty cycle is disclosed which forms part of a compact Winchester disk drive system having a storage capacity in excess of 380M bytes of information. The switching regulator is designed for frequencies in excess of 80 kilocycles per second and may therefore be construced using smaller capacitive and inductive elements. Also, very low heat dissipation and high regulator efficiency may be achieved by the improved .Iadd.power converter or .Iaddend.power supply to drive a brushless D.C. motor encased within a hard disk assembly where no separate fan or cooling system is used to aid in heat removal. Circuitry is provided to control the motor speed while simultaneously limiting the motor current to a predetermined level. This is a achieved by controlling the voltage applied to the motor by suitably adjusting the duty cycle of the switching regulator. A filter is provided to ensure that the switching regulator current fluctuations are not reflected in the current drawn from the power supply. At the start when the D. C. motor E.M.F. is zero, the switching regulator causes significantly higher current to flow through the motor than is drawn from the power supply through a current multiplying effect. These unique features provides significant advantages in a Winchester disk drive using thin film media whose overcoming high level of initial stiction-friction forces .Iadd.between the read/write heads and the recording media .Iaddend.is important and desirable.

Uninterruptible power supply apparatus and power path transfer method

Abstract: An uninterruptible power supply capability is provided for line regulators of a variety synthesizing a desired waveshape for presentation to a critical load. A static switch is active intermediate the input of the line regulator and the line power supply to provide a power path during normal operation. Upon the occurrence of a line defect, a stand-by power path is provided which includes a source of d.c. stand-by energy such as rechargeable batteries which supply input to an unregulated inverter which, in turn, provides an unregulated input through an inductance to the input of the line regulator. Transfer is achieved by preliminary voltage level adjustment at the inverter and the inverter itself is employed to assure commutation off of the switching components of the static switch. Detection of line fault is made by detecting any instantaneous phase shift in the line input.

Switching power supply

Abstract: A switching power supply, in which a series circuit consisting of a primary winding of a transformer (4) and a controllable switch (3) is connected with a DC power source (l0) and a secondary winding of the trans­former is connected with a first voltage source (50) outputting the voltage developed across the secondary winding during the on-period of the controllable switch and a second voltage source (60) storing the exciting energy of the transformer during the off-period of the controllable switch by using the exciting inductance of the transformer as a current source, a series circuit consisting of the first and the second voltage sources being connected with a load (70). Owing to this construction, even if voltage-current characteristic of a load having constant voltage chracteristic, such as a magnetron, vary due to variations in the temperature, etc., the output voltage is automatically compensated and a stable electric power can be supplied to the load.

Power supply system having improved input power factor

Abstract: A circuit and method using a low frequency active switch for improving input power factor in power supplies utilizing a full wave rectifier and capacitor filter for supplying a filtered DC voltage from an AC power source. A switch control activates and deactivates an active switching once in each half cycle of the alternating voltage input. The switch control is connected to the active switching for operating the circuit providing high power factor.

A 580 kHz switching regulator using on-off control

Abstract: The analysis and design of a 580 kHz switching regulator incorporating a series-resonant converter is described. On-off control is used in the feedback loop of the regulator to achieve regulation of the output voltage. An easy-to-use graphical method of analysis of transient currents is introduced as a tool for the analysis and design of the regulator. The 40W regulator circuit which has been built shows exceptionally good transient load regulation and high efficiency.

Unique computer power system with backup power

Abstract: A computer power system comprises an AC-to-DC power supply for providing DC power to the computer during the presence of AC line power and a backup power supply for providing DC power from batteries directly to the DC operated components of the computer system, completely bypassing the AC to DC power supply, when AC line voltage is absent or low.

Power source using high-frequency phase control

Abstract: A power source using high-frequency phase control possessing an ability to cause the transfer of electric power between a power source side and a load side to be made through a high-frequency transformer and to effect control of the output voltage by subjecting the power source side and the load side circuits to on-off control with a certain phase difference. This power source can be used as an uninterruptible power source, a device for controlled drive of a motor, a DC constant-voltage power source, or a constant-current device, for example.

Floating driver circuit and a device for measuring impedances of electrical components

Abstract: A floating driver circuit. A power supply is connected through a signal source to an amplifier's input terminal. The power supply is also connected to a pair of power supply terminals of the amplifier, via at least one resistor for each power supply terminal, so that direct current flows from the power supply into the power supply terminals. Further, at least one capacitor is connected to each power supply terminal. A cable, preferably coaxial, has first and second conductors. The first conductor is connected to a signal output terminal of the amplifier. The second conductor is connected to the power supply terminals through the capacitors. A pair of these circuits is combined at opposite ends of an electrical component to enable measurement of the impedances thereof.

Shielded electrical wire construction, and transformer utilizing the same for reduction of capacitive coupling

Abstract: A current carrying wire is provided with a tubular shield construction which essentially covers the wire with conductive material, and preferably emulates a classical Faraday shield. The shield is formed of a multiplicity of insulated shield wires for minimized eddy current loss. When such a shielded wire construction is formed into a primary winding of a power transformer for a switching power supply, the secondary circuit is protected from electric shock hazards while enabling use of a gap free toroidal core for close coupling between primary and secondary windings. In another embodiment, such shields are used on both the primary and secondary windings of a matching transformer and are arranged for common mode rejection of noise associated with low power data signals.

Unity power factor single phase power conditioning

Abstract: This work presents the results of a detailed theoretical and experimental analysis of an elementary switched power conditioning system with unity power factor. The line current stays sinusoidal and in phase with the bus voltage while its amplitude can be varied within a wide range. The introduction of a Penalty Factor (cents/kWh) enabled to define the most cost effective operation in the context of a given resistive load and maximum allowable amplitude of the ripples in the line current.

Power controller for circuits with battery backup

Abstract: A power controller for selectively coupling the voltage from a primary power source to a power output terminal or coupling the voltage from a battery backup input terminal to the power output terminal includes circuitry for receiving a reset or isolation signal. After receipt of the isolation signal when the primary power source is above a first threshold voltage, the primary power source and the backup battery source will be isolated from the output power terminal on the next occurrence of the removal of the voltage from the primary power source.

"The merged P-I-N Schottky (MPS) rectifier: A high-voltage, high-speed power diode"

Abstract: Experimental confirmation of the theoretically predicted superior characteristics of the MPS rectifier for high voltage, high frequency power switching applications has been obtained by the fabrication of devices with aluminum Schottky barriers. These devices exhibit a 6 to 8 fold smaller reverse recovery stored charge and operate at 1.5 to 3 times the forward current density when compared with the P-I-N rectifer. Typical applications are in motor drive and switch mode power supply circuits.

Off-line switcher with battery reserve

Abstract: An off-line switcher includes an auxiliary winding on the secondary side of the power transformer coupled by a power switch to a secondary voltage source in order to provide uninterruptible power to the output from either a primary AC or a secondary DC source. The power switches coupling both primary and secondary source voltages to the power transformers are driven at identical duty cycles by a common regulation control. Differing transformation ratios between primary and secondary sources of power define different operational ranges and determine flow of power based on the magnitude of the primary source of power.

Power supply voltage level sensing circuit

Abstract: A power supply voltage level sensing circuit on an integrated circuit generates a reset signal that holds the components of the integrated circuit in a defined state when the power supply voltage level drops below a predetermined voltage. The reset signal is released when the power supply voltage level returns to above the predetermined voltage. The voltage level sensing circuit is comprised of two inverters and a filter circuit. The inverters start to conduct at different power supply voltage levels and have different trigger point characteristics. The power supply voltage level sensing circuit may be coupled with a power-on reset circuit to create a voltage sensing power-on reset circuit which generates a reset signal not only when the power supply voltage is first supplied to the circuit, but also when the power supply voltage level temporarily falls below a selected value.

Inrush-current limiter for switching regulator power supply

Abstract: A DC voltage power supply circuit for suppressing turn-on transients applied to a switching voltage regulator circuit includes a relatively high impedance current suppression element connected in series between a rectifier circuit and a capacitive load, means for sensing a voltage drop developed across the suppression element, a diode network for developing a reference potential, and a silicon-controlled rectifier having a gate electrode responsive to the voltage drop developed across the current suppression element and the reference potential developed across the diode, for energizing a relay having contacts for disabling the switching regulator from supplying the load during the initial turn-on phase, and for shunting the current suppression element and activating the switching regulator after the capacitive load is substantially charged.

Backup power switch

Abstract: A P-channel field-effect transistor includes an inherent junction diode. As it is normally used, the inherent diode is back-biased and therefore effectively out of circuit. An uninterruptible power supply arrangement including primary and backup voltage sources supplies uninterrupted power to a load by way of two or more P-channel field-effect transistors connected so that their inherent diodes conduct to provide an OR function, independent of field-effect operation of the field-effect transistors. A control circuit controls the gate voltage relative to the source voltage of each transistor to selectively short-circuit the inherent diode of that one transistor which is connected to the power supply which is to energize the load. This reverse-biases the other inherent diodes and effectively removes the other power supply from the circuit, so that power for the load is drawn only from the selected power supply, there is no diode forward junction potential reducing the load voltage, and no excess dissipation. Certain embodiments of the invention use commercially available integrated circuits to provide many of the required functions for the uninterruptible supplies.

Power Electronics: Devices, Drivers and Applications

Abstract: Provides a wide range of indepth coverage of both semiconductor device theory and device application in power electronics. Material covered gives the reader a sound appreciation of the device types, their operating mechanisms and limitations -- all of which is required for correct device selection. Focusing on high-power devices, the book considers how device structure and construction are related to its terminal electrical and thermal construction. Also covered are the circuitry required to use power devices, interfacing and control requirements, and the structure and electrical characteristics of a device as they relate to its drive and protection. Features numerous diagrams and problems with numerical answers.

Switching mode power supply start circuit.

Abstract: A start circuit (70) for a DC-DC switching converter (10) includes a relaxation oscillator (72-76) powered by a voltage input source (+VDC IN). The oscillator (72-76) generates start pulses which are coupled to a switch (16) and cause switch (16) to close during each pulse, thereby activating primary winding (12) of transformer (14). A secondary winding (34) generates a voltage which gradually charges a capacitor (78) coupled to a pulse generator (60). When sufficient energy has been stored in capacitor (78), the pulse generator (60) is activated and begins to modulate switch (16) to generate desired DC outputs across one or more capacitors (42, 50). Actuation of pulse generator (60) also causes start circuit (70) to shut off via a transformer (18) and elements (90-94). Thus, the primary winding and the secondary winding sides of transformer (14) are kept mutually isolated during start-up.

Control circuit used for a power conversion apparatus

Abstract: A control circuit for a power conversion apparatus, e.g., inverter and cycloconverter, which produces sinusoidal alternating current (AC) power through multiple switching operations of switching devices within a cycle and supplies the power to a load. The control circuit includes a current control minor loop for controlling the instantaneous value of the output current of the power conversion apparatus in compliance with a current reference value which is determined as the sum of the load current component determined basing on the detected value of load current, and the modification current component produced by a voltage controller to current error of output line voltage of said power conversion apparatus with respect of a sinusoidal voltage reference, whereby the output voltage of the power conversion apparatus is controlled accurately to have less distortion against harmonics of the load.

Cooktop appliance with improved power control

Abstract: A cooking appliance adapted for energization by a standard domestic household power supply employs a power control arrangement which accommodates electric resistive heating units designed for operation at a maximum RMS voltage level less than the RMS voltage level of the output power signal of the domestic power supply. The power control system couples power pulses from the external power supply to the heating unit at one of a plurality of available pulse repetition rates, each repetition rate establishing a corresponding RMS voltage level for application of power to the heating unit. The repetition rate associated with the maximum user selectable power setting for the appliance is effective to apply an RMS voltage level to the heating unit which corresponds to the voltage level for which the heating unit was designed. When a heating unit is turned from Off to On the power control system overdrives the unit at full supply voltage for a brief transient heat up period to rapidly heat the unit to its radiant temperature. The duration of this heat up period is controlled as a function of the elapsed time since the unit was last turned Off.

Switching power supply filter

Abstract: A filter for a switching power supply The filter includes a common mode inductor with coil configurations allowing differential mode current from a dc source to pass through but attenuating common mode noise from the power supply so that the noise does not reach the dc source The invention also includes the use of feed through capacitors at the switching power supply input terminals to provide further high-frequency noise attenuation

High power flyback, variable output voltage, variable input voltage, decoupled power supply

Abstract: There is disclosed herein a modular, high power, flyback transformer based power supply with step up and step down capability. The power supply uses multiple flyback transformers having switching transistors which may be either connected to one terminal of the primary winding or which may be placed in the center of the primary winding. The switching transistors are driven by pulse trains which are out of phase with each other. This results in lowered RMS values for ripple current through the input and output capacitors. The flyback voltage transients may be used to step up or step down the input voltage by varying the pulse width of the pulse in the switching pulse trains. In embodiments where the switching transistors are placed in the middle of the primary windings, better suppression of radio frequency emissions and current in safety ground wires is achieved. There is also disclosed a combination of such power supply modules in series or parallel on either the input or output to deliver higher power or higher output voltage or to be able to handle higher levels of D.C. input voltage. There is also disclosed an improved an improved flyback transformer design having substantially lower leakage inductance using coaxial cable as the wire from which the primary and secondary windings are made.

Variable speed constant frequency power system with boost converter auxiliary output

Abstract: A DC link variable speed constant frequency power system is provided with a voltage boost circuit connected to receive voltage from a pair of DC link conductors and to supply voltage to an auxiliary supply bus. During normal system operation, the voltage boost circuit transfers the DC link voltage to the auxiliary supply bus. When a system fault occurs, such that the DC link voltage is reduced, the voltage boost circuit is activated to boost the reduced DC link voltage level and supply that boosted voltage level to the auxiliary supply bus.

Regulated rectifier d.c. power supply

Abstract: A control circuit for controlling a known active harmonic filter operating as a step-up converter in a power supply with sinusoidal network current input and a power factor of almost unity. The step-up converter comprises: a main rectifier, a storage inductance (LS), a cross-connected high-speed transistor (TQ), a diode (D1) and a power storage capacitor (CL). The high-speed transistor (TQ) is controlled by a first threshold switch (STc) whose input is controlled by a control capacitor (C12) coupled to receive a signal representative of instantaneous rectified d.c. output voltage (UE), instantaneous power output voltage (Uo) and a signal representative of the charge state of the inductance. The inductance charge signal is obtained from a voltage jump (ringing voltage) between the inductance and the diode (D1) by sensing a flank of an oscillation voltage occurring at the diode by a RC circuit (R8, C10), which triggers a second threshold switch (STa) to control charge reversal and recharge of the capacitor (C12), thus determining the time instants of operation of the first threshold switch to control the cross-connected electronic switch (TQ) to conduction, and hence re-storing of electrical energy in the inductance.