Showing papers on "Flyback converter published in 1987"

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.

Apparatus for controlling electric motor

Abstract: A control apparatus for controlling the main circuit for driving an AC electric motor consisting of a diode converter and a pulse width modulation (PWM) power converting device, in which it is arranged that the DC current as the output of the diode converter is detected by a current detector, the AC component of this DC current is filtered through a high-pass filter, and a pulse-width-modulation control is exercised by a control circuit in response to the output of the high-pass filter so that the DC current as the output of the diode converter may be smoothed out in the main circuit by the PWM power converting device. By such arrangement, this control apparatus of an electric motor is made smaller in size and simplified in structure and enabled to control the power factor of the power source of the diode converter to close to 1.0.

Pseudo-resonant full bridge DC/DC converter

Abstract: This paper proposes a new dc/dc converter topology which combines the ease of control and wide range of conventional dc/dc converters, with low switching losses, low dv/dt and low EMI that is typical of zero voltage switched resonant converters. Consequently, the ratings of these components are substantially lower than for similarly rated resonant topologies. Operation at very high frequencies is possible and is shown with the fabrication of a 200 watt, 1 MHz dc/dc converter.

Three-Phase AC/DC PWM Converter with Sinusoidal AC Currents and Minimum Filter Requirements

Abstract: A pulsewidth modulation (PWM) control technique suitable for fully controlled three-phase ac/dc converters is analyzed, which gives sinusoidal input currents and ideally smoothed dc voltage. The technique allows four-quadrant operation and full-range control of the input power factor. An extension to a simplified converter scheme, capable of one-quadrant operation, is also considered. Operation of the converter is analyzed under both ideal and actual conditions. Control implementation and design criteria are discussed and experimental results are reported.

Development of a Unipolar Converter for Variable Reluctance Motor Drives

Abstract: A new converter concept for driving the switched reluctance motor has been developed. This converter has only one switching device per phase, uses a unipolar dc supply, returns all the trapped energy to the source, and does not require bifilar windings; it is called a C-dump converter because the trapped energy is dumped in a capacitor and then returned to the dc source. The topology for several different C-dump converters is presented. In addition, the design and experimental results for a C-dump converter using a chopper to recover the energy dumped on the capacitor are presented.

High frequency, electronic fluorescent lamp ballast

Abstract: A ballast for controlling the light emitted by fluorescent lamps (25) is disclosed. DC power derived from either a DC source or a rectified AC source is switched on and off at a high frequency rate by a switch (15) to control the flow of current through the primary winding of the transformer of a flyback converter (27). The switched output is rectified and applied by the flyback converter to the filaments of the fluorescent lamps (25) to be controlled. The rectified, switched output is also applied by a π filter (17) to a commutator circuit (21) that controls the starting of the fluorescent lamps (25). The commutator circuit (21) is switched at a lower frequency rate. The bridge input voltage and current are sensed and fed back to a control circuit (23), which includes a regulating pulse width modulator and a bridge switching circuit. The control circuit (23) also receives a pulse current feedback signal from the switch (15) and an external dimming control signal. The control circuit (23) controls the application of high frequency switching signals to the switch (15) that controls the application of power by the flyback converter based on the voltage, current and pulse current feedback signals. Which one of these three signals actually controls is determined by which signal first reaches a reference level. If the magnitude of the feedback voltage first reaches the magnitude set by an open circuit voltage reference, the feedback voltage signal controls. If the magnitude of the feedback pulse current signal first exceeds a predetermined magnitude, the feedback pulse current signal controls. If the feedback current first exceeds a reference magnitude controlled by the external dimming control, the feedback current signal controls.

A new on-chip converter for submicrometer high-density DRAMs

Abstract: The converter described is a feedback-type voltage regulator which supplies a reduced voltage to an entire RAM circuit. A novel timing activation method was introduced to save power. The converter has been implemented on an experimental 4-Mb dynamic RAM. It was found that an even faster access time and higher reliability compared to a conventional design could be achieved by using an on-chip voltage converter and shorter channel transistors. This voltage converter is suitable for high-density, high-speed, and high-reliability DRAMs with submicrometer transistors.

Two transistor flyback switching converter with current sensing for discontinuous operation

Abstract: Disclosed is a dual transistor flyback converter having a pair of synchronously driven switching transistors (20, 36) for switching voltage to a primary (12) of a flyback transformer (10). When driven into a cutoff state, transistor (36) isolates switching transistor (20) from the supply voltage (V1), thereby preventing a transformer reflected voltage from being superimposed on the supply voltage and imposing such voltage across the transistor (20). Clamp diodes (40, 42) maintain the switching transient voltage across the flyback transformer primary (12) between prescribed limits. Capacitor (48) allows the switching transient to pass and be clamped by the diodes (40, 42), but prevents the reflected secondary voltage from being clamped when the input voltage is low. A current sensing circuit (50) in series with the flyback transformer secondary (14) senses current flow during the power conversion cycle, and provides a digital indication to a PWM control circuit (66) to facilitate reliable discontinuous operation of the flyback converter.

Design Considerations for Very High Frequency Resonant Mode DC/DC Converters

Abstract: The demand for higher switching frequencies in power converters has rekindled interest in resonant mode topologies. Conventional resonant converter circuits, however, are not optimized for high-frequency operation. A new resonant mode dc/dc converter topology exhibits desirable characteristics including zero switching losses, elimination of snubbers, simple control strategy, and circuit operation that is insensitive to parasitics such as diode reverse recovery. Analysis and design techniques are discussed in detail and are experimentally verified with a 150-W prototype converter operating in the frequency range 500 kHz-1 MHz.

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.

Frequency feedback on a current loop of a current-to-pressure converter

Abstract: A current-to-pressure (I/P) converter (20) provides an output pressure as a function of the magnitude of a variable input DC current. The I/P converter (20) includes a pressure sensor (64) which produces a feedback signal representative of the output pressure. Based upon the feedback signal and the magnitude of the input DC current, an electrical control signal is produced which controls a device (40) for varying the output pressure. The I/P converter (20) also includes a circuit (86) for generating a time-varying signal which is sent back over the current loop wires (28) through which the input DC current flows. The time-varying signal provides an indication of whether the I/P converter (20) is functioning properly. This permits diagnosis of possible causes of control system malfunctions without having to inspect the I/P converter (20) itself.

Modular power supply with variable input voltage and output voltage flyback power modules

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 pulses in the swicthing 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 flyback transformer design having substantially lower leakage inductance using coaxial cable as the wire from which the primary and secondary windings are made.

Phase controlled DC-AC converter with high frequency switching

Abstract: A novel type of the sinusoidal DC-AC converter is presented, where a pair of switches is placed in each side of the primary and the secondary of the isolation transformer. This converter is controlled by the phase difference between the two pairs of switches. As a result, the transformer is miniaturized by making the switching frequency high. This converter is especially suitable for small UPS systems.

Overload-protection methods for switching-mode DC/DC converters: Classification/ analysis/ and improvements

Abstract: Switching-mode DC/DC converters must be protected against overload, to prevent failure of the converter or the external current-carrying hardware. This paper collects, classifies, analyzes, and evaluates the known protection methods, and describes a new negative-feedback frequency modulator which prevents short-circuit-current runaway. Test data prove the effectiveness of the new scheme.

DC to DC converter

Abstract: A DC to DC converter of the switched capacitor kind is described in which controlled solid state switches are used to effect the switching and to limit the current passed to the capacitors in dependence upon that required to match a load.

High efficiency battery adapter

Abstract: Extremely high efficiency is achieved in a DC to DC converter by using a relaxation oscillator in which two transistors alternately conduct current to the primary winding of a step-up transformer. The transistors are interconnected by a resistor and capacitor in series so that when the converter is lightly loaded, the saturable reactor in the circuit will be self-resonant, so as to draw only minimal power from the battery source. The converter also includes a battery charge level monitor circuit that prevents the DC to DC converter from oscillating and thus providing power unless the battery is above a minimum charge level when its voltage is applied to the converter. In a preferred embodiment, the converter provides an output of up to 100 watts.

Power-supply arrangement

Abstract: A flyback converter comprises the series arrangement of a primary winding (n₁), a transistor switch (S₁) and a resistor (R₁) between two input terminals (1, 2) for receiving an input voltage. The series arrangement of a secondary winding (n₂) and a diode (D₁) is arranged between the output terminals (3, 4) for connecting a load (M). The transistor switch (S₁) is controlled by pulses from a pulse-width modulator (10), a sawtooth voltage generated by an oscillator (20) being applied to a first input (11) and a first feedback voltage being applied to a second input (12) via a control amplifier (40), which feedback voltage is proportional to the difference between a referen­ce voltage from a reference source (30) and a fraction of the output voltage, and a second feedback voltage equal to the voltage across the resistor (R₁) being applied to said second input via a capacitor (C₁).

Variable input voltage DC to DC converter with switching transistor drive current regulator

Abstract: The DC to DC converter includes a coupled inductor having a primary winding and a feedback winding. A drive current regulator circuit receives a variable input voltage from the feedback winding but transmits a constant base drive current to the base terminal of the converter switching transistor. The base drive regulator circuit thereby enables the DC to DC converter to operate at high levels of efficiency over wide ranges of DC input voltages such as twelve to forty-eight volts DC.

Inductor with centertap switching transistor for reduced radio frequency emissions

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 pulses 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 flyback transformer design having substantially lower leakage inductance using coaxial cable as the wire from which the primary and secondary windings are made.

A high frequency AC/DC converter with unity power factor and minimum harmonic distortion

Abstract: A new forced commutated ac/dc converter and control strategy is proposed that is able to draw nearly sinusoidal currents at unity power factor from three-phase power lines. The power factor is controlled by adjusting the relative position of the fundamental component of an optimized PWM type voltage with respect to the supply voltage. Current harmonic distortion is minimized by the use of optimized firing angles for the converter at a frequency where GTO's can be used. This feature makes this approach very attractive at power levels of 100 kW to 600 kW. An 8096 microcontroller is used to minimize the interface hardware requirements. This paper presents the theoretical analysis of the converter, the control strategy and experimental results for a low power prototype.

Electronic load for testing transformers

Abstract: An adjustable electronic load for testing current transformers and/or voltage transformers, the load having connected, between its input current terminals, a series connection including the input of a current-to-voltage converter and the output of a controlled generator, and having connected, between its input voltage terminals, the input of a voltage-to-voltage converter. The outputs of the current-to-voltage converter and the voltage-to-voltage converter are each connected via an impedance to a control input of the controlled generator. The voltage-to-voltage converter and the current-to-voltage converter each comprise at least one amplifier with adjustable amplification. The amplifications of the two adjustable amplifiers are adjustable jointly in opposite directions. In the case of a load for testing a current transformer, with the rated secondary power of the current transformer being predetermined, the amplification of the current-to-voltage converter is reduced or increased and the amplification of the voltage-to-voltage converter is increased or reduced respectively, so as to increase or reduce the rated secondary current, respectively. In the case of a load for testing a voltage transformer, with the rated secondary power of the voltage transformer being predetermined, the amplification of the voltage-to-voltage converter is reduced or increased and the amplification of the current-to-voltage converter is increased or reduced respectively, so as to increase or reduce the rated secondary voltage, respectively.

Single-ended flyback converter or forward converter having a low blocking voltage, for the switching transistor

Abstract: A single-ended flyback or forward converter having a low blocking voltage for the switching transistor. Transistorised converters and forward converters produce a high flyback voltage in the phase when the transistor is switched off, which flyback voltage must be reduced to less than the maximum permissible transistor reverse voltage Uce by means of damping components (C,CR or RCD elements). The new solution (see figure) allows the flyback voltage to be limited without any power losses in separate damping elements by arranging two diodes and a capacitor as a collector network.

DC to DC converter with overvoltage protection circuit

Abstract: An overvoltage protection circuit limits the output voltage of a DC to DC converter to a maximum desired output voltage. An output voltage sensing circuit includes a semiconductor device such as a sidac having a normal resistive region of operation as well as a negative resistance region of operation which begins at a breakover voltage and extends into a foldback region. One terminal of the sidac is coupled to sense the converter output voltage while the second terminal opposite end of the sidac is coupled to a biasing device in the form of a resistor which generates an overvoltage signal when the sidac conducts current. The overvoltage signal from the biasing resistor is coupled to a converter switching transistor disabling circuit which reduces the converter output voltage to a level below the maximum desired output voltage in response to the overvoltage signal.

DC power transmission system

Abstract: In a DC power transmission system wherein two AC systems are interconnected by a first converter, a DC transmission line and a second converter to transmit power from one of the AC systems to the other of the AC systems via the DC transmission line, the DC power transmission system is provided wherein at least one of said first and second converters operating as an inverter is a current type self-commutated converter capable of being pulse-width controlled, the reactive power of the current type self-commutated converter is regulated by controlling a phase difference angle between its AC voltage and current, the DC voltage is regulated by pulse-width controlling the current type self commutated converter, and the DC current is regulated by the converter operating as a rectifier.

A computer-aided design and simulation tool for switching converters

Abstract: A fully automated computer-aided design approach is presented which results in an optimal power stage and control circuit design. The design meets all dc, small signal and large signal closed-loop performance specifications. The proposed approach is very efficient; it can help in reducing component and manufacturing costs as well as design time and is successfully demonstrated on a multiple-output flyback converter breadboard.

Current-type converter protecting apparatus

Abstract: In a current-type converter system in which a DC current is fed to a load through a pulsating current suppressing DC reactor from a current-type converter constituted by self-extinction elements connected in a bridge circuit, a converter protection apparatus is arranged such that when a fact that a terminal voltage of the DC reactor becomes an overvoltage is detected, the self-extinction elements are turned on so as to form a closed circuit including the DC reactor, the load, and the converter so that the overvoltage can be suppressed and continuous operation of the converter can be carried out.

High voltage protecting circuit

Abstract: A high voltage protecting circuit in a cathode ray tube apparatus which comprises a main power switch adapted to be connected in series with an electric power source, a flyback transformer having primary, secondary and third windings, a rectifying circuit connected with the main power switch for rectifying a power source voltage originating from the power source and to be supplied to the flyback transformer, a switching device connected between the main power switch and rectifying circuit and provided with a control terminal, and a high voltage detecting and controlling device for comparing an output voltage, produced across the third winding of the flyback transformer, with a reference voltage and for generating a control signal when the output voltage exceeds the reference voltage. The control signal is utilized to hold the switching device in an OFF position.

Ringing choke type DC/DC converter

Abstract: A ringing choke-type DC/DC converter comprising a transformer having a primary winding, a secondary winding, and a feedback winding, an input DC power source connected through a transistor to the primary winding of the transformer, a DC power output connected through a diode to the secondary winding of the transformer, a base circuit having a first capacitor and connected between the base of the transistor and the feedback winding of the transformer, a branch circuit branching from the base circuit and having a Zener diode connected in series with a second capacitor, and an impedance provided in series between the transistor and the branch circuit for preventing the transistor from intermittently operating, thereby stabilizing the DC power output.