Showing papers on "Flyback transformer published in 1990"

Dual current sensing driver circuit

Abstract: A driver circuit (10) for an inductive load (12), such as a solenoid winding (16), includes flyback and energization current sensors (28, 40) which respectively sense the current through the coil during flyback and energization. The flyback current sensor (28) includes a flyback current resistor (30) disposed in the flyback current path of the winding (16) for producing a flyback signal proportional to the flyback current. The energization current sensor (40) includes an energization current resistor (42) disposed within the energization current path of the winding (16). The energization current resistor (42) is adapted to produce an energization signal in response to the energization current flowing through the winding (16). Control of the solenoid winding (16) is effected by a switch (24) which connects and disconnects the winding (16) from a power source (VB) in response to the duty factor of a control signal. A first summing amplifier (54) receives the flyback and energization signals and produces an actual current signal in response to the received signals. A second summing amplifier (60) receives the actual current signal and a desired current signal and produces an error signal in response to a difference between the actual and desired current signals. A first comparator (68) receives the error signal and produces the control signal responsive to the error signal, wherein the duty factor of the control signal is responsive to the magnitude of error signal. The duty factor of the control signal is constantly adjusted in this manner to maintain the solenoid current at the desired level.

Elimination of the positive zero in fixed frequency boost and flyback converters

Abstract: It is shown how a fixed-frequency, leading-edge modulated pulse width modulation can eliminate the undesirable positive zero in practical boost and flyback converters. This allows a substantial improvement in the closed-loop characteristics. Several techniques are employed to predict this result. The design procedure for elimination of the positive zero is presented. Experimental verification is provided. By providing an effective feedforward of the load current, this technique ensures excellent load transient response and low output impedance. There are several advantages to this technique. Measurement of the control-to-output transfer function cannot be easily performed. Also, the positive zero elimination is dependent on the capacitor ESR value. This technique can be susceptible to noise since the output voltage switching ripple is not filtered in the compensation network. >

Fly back converter switching power supply device

Abstract: An improved regenerative control type power supply device having a higher efficiency is disclosed. The power supply device has: a first switching elements which is connected in series with the primary winding of a transformer (this series circuit is connected to the terminals of a DC power source); a second switching element; a capacitor which is connected in series with the second switching means (this series circuit is connected to the primary winding); a rectifying and smoothing circuit for rectifying and smoothing a flyback voltage which generates in the secondary winding and for outputting a resulting DC voltage; and a drive circuit for driving alternately the first and second switching means with predetermined ON-OFF periods.

Control system for switched reluctance motor operating as a power generator

Abstract: A method for operating a multi-phase switched reluctance motor is a generator mode includes gating switches connected in series with selected ones of the phase windings of the motor into conduction to establish current flow in a selected one of the windings. The switches are thereafter disabled and current is forced to commutate into flyback diodes whereby the current is returned to an associated DC bus. The instant at which the conducting switches are gated out of conduction is selected or measured in angular displacement between an associated stator pole and a corresponding rotor pole by establishing a preselected magnitude of current such that when the current in the winding reaches that magnitude, the switches are disabled. The voltage at the DC bus is regulated during generator mode operation by adjusting the phase angle measured between a stator pole and a corresponding rotor pole at which the switches are gated into conduction. The voltage is alternatively regulated at the DC bus by adjusting the phase angle at which the switches are disabled if the generated current does not reach the preselected magnitude. Overcurrent protection is included to reduce the turn-on angle if the current in the DC bus exceeds another preselected magnitude.

Method of feedback regulating a flyback power converter

Abstract: A method of providing power regulation in power conversion equipment, where power regulation is implemented on the primary side of a transformer used to provide isolation of a power source from the load. The feedback mechanism utilizes current perturbations which are summed with the primary current in the power transformer. These perturbations are transformed with the load current to the primary side of the power transformer and extracted using signal processing means to regenerate a useful signal which is isolated from the load.

Analysis and design of a parallel resonant converter including the effect of a high-frequency transformer

Abstract: A high-frequency (HF)-link DC-DC parallel resonant converter (PRC) operating above resonance is analyzed using the state-space approach. The analysis includes the effect of the leakage and magnetizing inductances of the high-frequency transformer. Steady-state solutions are derived and used to obtain the design curves. A method of obtaining an optimum operating point under certain constraints is developed and used as the basis of a simple design procedure. The analysis shows that including an HF transformer introduces a new mode of operation in between the two general steady-state modes. Experimental results obtained with a MOSFET-based PRC for three different transformer turns ratios are presented to support the theory. Efficiencies of about 89% were obtained for 985 W, 115 V, and 230 V output converters, whereas an efficiency of about 86% was obtained for a 15 V, 63 A converter. It was observed that the introduction of the transformer considerably affected the performance, especially in the case of low output voltage and large load current converters. >

Main and auxiliary transformer rectifier system for minimizing line harmonics

Abstract: A polyphase transformer design is presented in which transformer output pors are accurately constructed in both voltage magnitude and relative phase angle. The design incorporates both main and auxiliary transformers that are used in unison to produce the accurately constructed phasors. The main transformer permits rough phasor adjustment to be made with the auxiliary transform permitting phasor fine tuning. Such a design is particularly suitable in transformer approaches that require output phases that are of a number not evenly divisible by three.

An overcurrent protection apparatus

Abstract: A current of an alternating current electric line is detected by a current transformer, the output of the current transformer is rectified by a rectifier, a series connection of a switching means and a resistor is coupled across the output terminals of the rectifier, a control circuit composed of a capacitor, a comparator and a reference voltage generator is coupled in parallel to the switching means through a diode, when the DC output voltage exceeds a predetermined voltage based on the reference voltage of the reference voltage generator, the comparator outputs a signal for closing the switching means, and the voltage which is applied to the control circuit is limited to a predetermined value.

Insulation monitoring system of a direct current power supply system

Abstract: Insulation monitoring of a direct current power supply system is achieved by application of an alternating current and the detector is constituted by a current transformer and a Hall-effect current sensor. This Hall-effect sensor controls a direct current generator, which supplies a compensation winding of the current transformer, so as to prevent saturation of the toroid of this current transformer. When a ground fault occurs, the alternating current generator generates a fault current detected by the transformer.

Electronic electricity meter

Abstract: A meter includes a measuring part (1) and an evaluating part (2). The measuring part (1) contains an open magnetic current transformer (3) of the unloaded transformer type and an integrator (6) connected downstream of the transformer. As a result, no measuring errors caused by saturation occur in the transformer, and the metering of consumption is frequency-independent.

Circuit arrangement for a freely oscillating flyback switching power supply

Abstract: The invention relates to a circuit arrangement for a freely oscillating isolating transformer switched-mode power supply having a control device (IC) for the pulse-width-modulated triggering of an electrical switching element (T1). As control information, this control device (IC) receives, inter alia, on an input terminal (8) a zero passage detector signal (Uzero) and, on a further input terminal (1), a control voltage (UR), which is dependent on the output voltage (UA) of the switched-mode power supply. In order to ensure reliable operation of the circuit arrangement, even in the event of low power consumption and especially in the standby mode with only a few watts no-load power, it is proposed to provide, in addition to a capacitive coupling of the two input terminals (1, 8), a detector device (DE) with whose aid an internal reference voltage (Uref) of the control device (IC) can be reduced in the standby mode. By this means, the increase in the output voltage, which is undesired in the standby mode and is increased even further by the capacitive coupling, can effectively be avoided. … …

Control algorithms and circuit designs for optimally flyback-charging an energy-storage capacitor (e.g. for a flash lamp)

Abstract: Optimum flyback-charging of an energy-storage capacitor is discussed. It charges the capacitor to a specified voltage within a specified time, with minimum peak current in the transistor and a transformer. Recommended methods are hysteretic current-mode control with current sensing in both transformer windings, peak-current-commanding current-mode control with switching frequency or transistor off time varying in a prescribed way during the charging, or valley-current-commanding current-mode control with switching frequency or transistor on time varying in a prescribed way during the charging. >

Reverse polarity flyback switch

Abstract: The subject invention provides a coil driver circuit having protection against a reverse-polarity battery connection and is suitable for use in such control modules. The driver circuit controllably actuates N coils in response to control signals supplied by the control module. The driver circuit includes N control switches, each coupled in series between a first terminal of an associated one of the coils and a first common junction. The first common junction is normally connected to a positive reference terminal of the electrical power source. The control switches are adapted to controllably connect the coil first terminals to the power source positive reference terminal in response to externally supplied control signal. The coils have second terminals connected at a second common junction, and the second common junction is normally connected to a negative reference terminal of said power source. N flyback diodes, each having a cathode connected to a respective coil first terminal and an anode connected to a third common junction. The third common junction is normally connected to the power source negative reference terminal. A circuit is provided for sensing a reverse-polarity battery connection and responsively disconnecting the diodes from the third junction.

Power supply circuit featuring minimum parts count

Abstract: A full reset flyback regulator includes a power transformer having a primary winding and at least one secondary winding coupled to a load. A single control winding on a primary side of the power transformer is coupled through control circuitry to a gate electrode of a switching device that is connected to the primary winding. The voltage polarity on the control winding alternates so that if the switching device is "ON" a drive voltage is provided on its gate electrode and if the switching device is "OFF" a bias voltage is provided to the error amplifier control circuit. Each cycle of the regulator is initiated via a sync pulse which is provided from the high voltage flyback transformer of a display or monitor subsystem.

TV-VTR compound set

Abstract: Disclosed is a TV and VTR compound set in which a holder for supporting TV's printed circuit board in a space between the inside surface of the cabinet and TV's Braun tube vertically and TV's flyback transformer laterally is newly introduced, by which holder TV's flyback transformer and VTR's picture recording and reproducing head come to be placed apart from each other at the farthest distance possible in the cabinet and the transformer's noise comes to be prevented from interfering with the head and by which not only is TV's transformer's noise prevent from entering VTR's head as mentioned above but also the dimension of the cabinet can be made smaller than that of the conventional cabinet similarly housing TV and VTR and the production cost of the set can be reduced.

Disabling arrangement for a circuit operating at a deflection rate

Abstract: Active turn-off or disabling circuits respond to control signals from a control unit which defines the mode of operation of a receiver. In response to a designation of a standby mode of operation the active disabling unit actively disables a pulse width modulator to prevent pulses from being produced based upon an input of ringing signal. In addition, the active disabling circuits prevent such ringing signal from negatively effecting pincusion protection circuits. The ringing signal is produced in a horizontal flyback transformer during a transition interval that follows a transition to standby mode of operation.

High frequency heating apparatus with abnormal condition detection

Abstract: A microwave oven includes a step-up transformer having primary and secondary windings, an inverter inducing a high frequency oscillating current at the primary winding of the transformer by an on-off operation of a switching element, a magnetron to which a DC voltage is applied by the transformer, a current transformer detecting an input current to the inverter, a control circuit for controlling "on" and "off" periods of the switching element so that a magnetron anode current is controlled, and a detecting winding arranged in the transformer so as to be magnetically connected to the primary winding. The detecting winding detects an induced voltage which indicates either a short-circuit or open-circuit in the secondary circuit of the transformer. The control circuit detects an abnormal condition of the secondary circuit of the transformer based on the induced voltage detected by the detecting winding. Upon detection of the abnormal condition, the control circuit operates to interrupt the operation of the switching element.

High voltage stabilization circuit for video display apparatus

Abstract: A horizontal deflection circuit output stage generates a retrace pulse in a tertiary winding of a flyback transformer. A flyback pulse that is substantially wider than the retrace pulse is produced in a winding of a second transformer that is coupled in series with the tertiary winding such that the retrace pulse occurs when a peak portion of the flyback pulse is already relatively "flat". The amplitude of the flyback pulse is controlled in a negative feedback loop for stabilizing an ultor voltage.

Intrinsically safe power supply unit

Abstract: An intrinsically safe power supply unit, more particularly for face supports in mining, comprising an ac transformer connected to a rectifier and power resistors for limiting the current and connected to the dc voltage output, wherein the ac voltage transformer is a resonance transformer which stabilizes the secondary voltage, and the dc voltage occurring behind the power resistors is kept constant by three voltage limiters connected in parallel.

A universal power supply integrated circuit for TV and monitor applications

Abstract: A switching mode power supply circuit which operates according to the master-slave concept and is located in the primary side of a TV set or monitor offline flyback power supply is described. The circuit ensures the starting function, the standby function according to the primary regulation principle, and the normal operating mode in association with a switching regulator located in the secondary side of the power supply. The circuit provides the base drive of the power switch without external boosters. It ensures various safety functions, such as power transistor current limitation and under- or overvoltage detection. Although mainly designed for the master-slave concept, the circuit can also be used alone, according to the primary regulation concept, or in association with an optocoupler. The circuit layout is presented. >

Switched mode vertical deflection system and control circuit

Abstract: A deflection system comprises: a signal generator, an amplifier stage, a negative feedback path and a vertical rate waveform generator. The signal generator is coupled to a source of flyback pulses for developing from energy in the flyback pulses a horizontal rate drive signal having a predetermined and substantially constant DC voltage reference level. The amplifier has a first input coupled for receiving the horizontal rate drive signal and an output coupled to a deflection coil. The amplifier output has a DC voltage reference level corresponding to the DC reference level of the horizonatl rate drive signal. A DC feedback signal on the negative feedback path is related to deflection current. The feedback path is coupled between the coil and a second input of the amplifier. The vertical rate waveform is also coupled to the second input of the amplifier for modulating the horizontal rate drive signal. The output of the amplifier is a pulse width modulated control signal for a switching element, for example a silicon controlled rectifier. In a switched mode vertical deflection system, the horizontal rate drive signal and the vertical rate waveform are ramp signals and the flyback pulses are horizontal flyback pulses. The signal generator is DC coupled between the source of flyback pulses and the amplifier. The signal generator comprises a Zener diode, a capacitor and a resistor connected in parallel.

Partial discharge amplitude distribution of power transformer oils

Abstract: The most commonly used criteria for PDIV (partial-discharge inception voltage) determination are examined using three synthetic transformer oils as test fluids. It is shown that the PD amplitude distribution changes both with increasing applied voltage and with test duration. The use of a multichannel analyzer was shown to be most helpful in rendering the PDIV statistically more meaningful. It is noted that both the number and amplitude of PDs are random phenomena the occurrence of which is hard to predict. Close to the breakdown voltage the PD activity increases and its amplitude spectrum approaches a quasi-exponential shape. >

High voltage generator for television receiver

Abstract: A high voltage generator using a flyback transformer to generate high voltage pulses and including a control switching transistor inserted in a power supply circuit in a manner to be turned off during a trace interval. The amount of electric energy accumulated in a resonance circuit is intermittently controlled by the on-off action of such switching transistor, so that the level of the high pulse voltage outputted via the transformer can be maintained constant to consequently enhance the response characteristic in the voltage regulation while minimizing the number of required component elements.

Resonance transformer power conditioners

Abstract: Designs for power conditioning systems based on the resonance transformer have been developed for applications requiring compact, lightweight power supplies ranging from average power levels of 10 kW to over 1 MW. The resonance transformer is a patented concept which depends on a set of resonant LC circuits to produce transformer-like voltage or current gain. Because this approach does not require the magnetic core material associated with a conventional transformer, significant savings in both size and weight can be realized, particularly at higher power levels. Technical issues associated with the conventional transformer, such as coupling of the primary and secondary windings at both high voltages and high frequencies and thermal management of heat generated in the transformer core are also avoided. Several designs have been generated and tested, including a 20 kHz, 10 to 15 kW average power system. This power supply will provide a voltage gain of 50 and weighs less than 100 lb. >

Circuit for stabilizing high voltage according to the change of horizontal oscillating frequency

Abstract: There is disclosed a circuit for stablizing the high voltage of the high voltage generating circuit in a CRT according to the change of the horizontal oscillating frequency, comprising a diode, the cathode of said diode being connected to the intermediate terminal of a flyback transformer (FBT), the anode of said diode being connected to first resistor and a variable resistor, a first transistor, the base of the said first transistor being connected to the intermediate terminal of said variable resistor, a second transistor, a third transistor, the collector of said first transistor being connected through a grounded second resistor to the base of said third transistor, the collector of said third transistor being connected to the base of said second transistor, the collector of said second transistor being connected to a direct current source, and a fourth transistor, the emitter of said second transistor being connected through the primary coil of said flyback transformer to the collector of said fourth transistor, the base of said fourth transistor being connected to a horizontal oscillating circuit.

Flyback current dampening apparatus

Abstract: An apparatus (16) for dampening current in a coil (22) is provided. A switchable member (28) having 'ON' and 'OFF' states controls the current level in the coil (22) and a flyback circuit (48) allows current in the coil (22) to slowly dissipate when the switchable member (28) changes from the 'ON' to the 'OFF' state thereby preventing damaging voltage spikes. The flyback circuit (48) has a high resistance when the switchable member (28) changes from the 'ON' to the 'OFF' state so that the coil (22) current is dampened as quickly as possible without creating a destructive voltage and low resistance when the switchable member (28) is in the 'ON' state to conserve energy. A signalling device (60) creates a voltage signal as a function of current passing through the flyback circuit (48) and a receiving device (44) varies the resistance of the flyback circuit (48) in response to the voltage signal. The apparatus (16) is particularly suited for use in a motor control circuit (10).

D.C. current network insulation monitoring system

Abstract: The insulation of a DC network is monitored by injecting an alternating current into the network. The detector consists of a current transformer (38) and a Hall effect current sensor (28). The Hall effect sensor controls a DC generator (46) which supplies a current to a compensation winding (42) on the current transformer (38) in such a way as to avoid saturating the core (36) of the current transformer (38). When an earthing fault (24) occurs, the AC generator (22) produces a fault current which is detected by the transformer (38).

Contact sensor module

Abstract: A single module for relay, limit switch or related devices for self-powering the set of contacts and sensing the state of the contacts, compatible with Opto 22 and related I/O systems interfacing microprocessors and industrial processes and the like and with further features, if desired, of a single isolation device for both power and signal isolation such as a transformer, preferably employing conversion to D.C. in the transformer output and optional resonant mode flyback pulses to step up the primary drive voltage.

Power regulation during start up and shut down

Abstract: A switched mode power supply and horizontal deflection system comprises a first oscillator circuit for generating horizontal rate synchronizing trigger pulses, having a voltage supply input terminal; a horizontal output stage; and, a second oscillator circuit for driving the output stage, operable at a horizontal rate responsive to the trigger pulses and free running at a different rate absent the trigger pulses An overcurrent protection circuit for the horizontal output stage responds to an overcurrent condition which can occur during free running of the second oscillator circuit A flyback transformer is coupled to the horizontal output stage and has a secondary side voltage supply coupled to the voltage supply input terminal for energizing the first oscillator circuit during operation of the output stage An energy storage device, for example a large value capacitor, is coupled to the voltage supply input terminal for energizing the first oscillator circuit for a period of time after the horizontal deflection system is deactivated The capacitor and a resistor form a timing network for the first oscillator circuit The first oscillator circuit continues generating synchronizing trigger pulses and prevents operation of the second oscillator circuit at the free running frequency A quick charging path for the energy storage device, for example a Zener diode in parallel with the resistor, minimizes operating time of the second oscillator circuit at the free running rate prior to the initiation of the synchronizing trigger pulses when the power supply and horizontal deflection system is activated

Generator for operating a rotating anode x-ray tube

Abstract: A power generator drives a rotating anode of an X-ray tube via a stator-rotor in which the stator receives the anode side high voltage potential. An isolating transformer is connected to an alternating current source which converts DC voltage to AC voltage via a rectifier bridge, a regulator and a switching inverter. The secondary winding of the isolating transformer is coupled to a second rectifier bridge for applying rectified voltage to a second switching inverter that generates the alternating currents for the stator windings. The second inverter receives the high voltage which is also applied to the tube to generate X-rays.