Showing papers on "Precision rectifier published in 1970"

A feedback-controlled ferroresonant voltage regulator

Abstract: A new regulated rectifier which combines a ferroresonant regulator with a simple control circuit is described herein. The voltage regulating function normally provided in a ferroresonant regulator by the saturating core is provided by the control circuit in this new regulated rectifier. The control circuit provides regulation by varying the amplitude of the alternating voltage feeding the rectifier and filter. By incorporating feedback into the control circuit, regulation of better than ±1/2 percent for line, load, frequency, and temperature changes can easily be attained. The new feedback-controlled circuit retains many desirable properties of conventional ferroresonant regulators such as half-cycle transient response, good input power factor, ideal output waveform for rectification and filtering, high efficiency, short circuit protection, and suppression of input voltage spikes. Additional features are level set, improved efficiency, lower stray magnetic fields than observed with conventional ferroresonant regulators, and, primarily, precision regulation. Data on an 800-watt regulated rectifier employing the new circuit are also presented.

Triac motor speed control

Abstract: A motor speed control including a fullwave diode bridge rectifier for rectifying alternating current received from a supply circuit, a triac coupled in a series loop circuit with the bridge rectifier and the supply line for controlling the flow of current through the bridge rectifier during both positive and negative half-cycles of the supply line voltage, and a control circuit for controlling the firing of the triac, the control circuit including a diac coupled in series with a timing capacitor. A speed-setting potentiometer, coupled in series with the timing capacitor, is utilized for selecting the operating speed of the motor.

Switching arrangement for the stabilization and ignition of welding arcs and the like

Abstract: A switching system for the stabilization of alternating-current welding arcs and for the ignition of alternating-current or direct-current welding arcs in which the ignition or stabilization current pulse between electrode and workpiece or between two electrodes is transmitted through a capacitor and at least one semiconductive controlled rectifier (SCR or thyristor) is provided in the discharging circuit of the capacitor. The gate of the controlled rectifier is triggered by a control circuit synchronized with the current source and including a voltage-responsive switching element in circuit with a control capacitor. The voltage-responsive switching element is a DIAC-type trigger diode whose output is connected directly i.e., via only ohmic impedance) with the control electrode or gate of the controlled rectifier.

Auto theft prevention system

Abstract: An improved anti-theft system for a motor vehicle, or the like, which effectively prevents any voltage from being built up across the ignition coil of the vehicle unless a control signal is applied to the system. This is achieved by including a silicon controlled rectifier, for example, in the circuit, the silicon controlled rectifier being fired whenever attempts are made to start the vehicle without the introduction of the control signal to the ignition circuit, the silicon controlled rectifier effectively short-circuiting the primary of the ignition coil as to prevent any build-up of ignition voltage across the secondary. An improved electronic lock circuit supplies the required control signal to the anti-theft system only when a series of switches are closed in a particular pre-selected sequence known only to the owner of the vehicle.

Battery charger using a controlled scr to provide tapering charging characteristics

Abstract: The battery charger comprises a transistorized system comprising a stepdown transformer coupled to a silicon-controlled rectifier, with the power output of the rectifier controlled by a sensing network in circuit with phase shift circuit means. A Zener diode is provided which furnishes a reference voltage applied across a voltage divider in the sensing circuit wherein no current can flow to a battery so long as the battery voltage equals the reference voltage. If the battery voltage drops due to a load or for some other reason, current will bias a transistor into a conduction condition to actuate the phase shift network. The latter is coupled to the silicon-controlled rectifier to gate the rectifier in a manner automatically to charge the battery at a rate inversely proportional to the amount of charge on the battery.

Gate controlled switch transistor drive integrated circuit (thytran)

Abstract: A body of semiconductor material comprises a controlled rectifier switch and a transistor each sharing a common anode. The controlled rectifier provides the base drive which is necessary to keep the transistor in an ''''on'''' condition. Once operating, the transistor functionally does not see the controlled rectifier in the electrical circuit. When it is desired to shut off the transistor, the necessary signal is sent to the gate region of the controlled rectifier and the rectifier is turned off thereby removing the base drive from the base region of the transistor which in turn turns all of the regions of the transistor off substantially simultaneously. This type of device is designated by the term ''''THYTRAN.

A Feedback-Controlled Ferroresonant Voltage Regulator

Abstract: A new regulated rectifier which combines a ferro- resonant regulator with a simple control circuit is described herein. The voltage regulating function normally provided in a ferro- resonant regulator by the saturating core is provided by the control circuit in this new regulated rectifier. The control circuit provides regulation by varying the amplitude of the alternating voltage feeding the rectifier and filter. By incorporating feedback into the control circuit, regulation of better than f1/2 percent for line, load, frequency, and temperature changes can easily be attained. The new feedback-controlled circuit retains many desirable properties of conventional ferroresonant regulators such as half- cycle transient response, good input power factor, ideal output waveform for rectification and filtering, high efficiency, short circuit protection, and suppression of input voltage spikes. Additional features are level set, improved efficiency, lower stray magnetic fields than observed with conventional ferroresonant regulators, and, primarily, precision regulation. Data on an 800-watt regulated rectifier employinz the new cir- cuit are also presented.

Ambient light variation detector

Abstract: Disclosed is a method and apparatus for supplying a control signal in response to an abrupt change in ambient light level and for maintaining such control signal for a controlled time period irrespective of subsequent light level changes during such controlled time period, such apparatus including a photo-resistor coupled by an input transistor amplifier stage to the trigger input of a silicon controlled rectifier. The silicon controlled rectifier is coupled to an output transistor amplifier stage which provides such control signal.

Pulse generator for a variable load

Abstract: A transmission line is charged by means of a floating power supply and is discharged through a silicon controlled rectifier into a variable load. A second silicon controlled rectifier, disposed in shunt relation with the line, is employed for insuring pulse termination.

Rectifier circuit including transistors

Abstract: A rectifier circuit which uses transistors, is unaffected by changes in ambient temperature and frequency, and shows a linear relation between input AC and output DC. In the invention, the diode or diodes of a rectifier circuit are replaced by the emitter-collector path of a transistor (Q) and the base electrode of the transistor is connected to one of the output terminals 3 by means of a resistor R1 having a high resistance compared to the base input resistance of the transistor.

Control circuits for an electric tractor

Abstract: The main current conduction path of a controlled rectifier and a starting network therefore are connected in parallel across a source of unidirectional potential through a single pole, double throw switch. With the switch in the start position with the pole engaging one contact the starting network is connected in circuit with the source of operating potential and in the other position with the pole engaging the other contact, circuit is completed through the controlled rectifier. The triggering voltage developed by the starting network decays rapidly with time the starting network is out of circuit. Accordingly, after conduction has been established in the controlled rectifier by switching the pole of the switch from the start to the operate position, should conduction be interrupted by a safety switch in the main conduction circuit of the controlled rectifier conduction cannot be reestablished therein by simply closing the safety switch but requires the return of the single pole, double throw switch to the start position to establish triggering potential for the controlled rectifier.

Battery charging system with reverse battery protection

Abstract: A circuit prevents a generating machine from being operatively connected to a battery whenever the battery has been connected with a reverse polarity. The machine is coupled through the anode-cathode path of a silicon-controlled rectifier to the battery and the rectifier is switched on in response to current pulses in the field winding of the machine. A primary winding of a pulse transformer and the secondary winding of the pulse transformer are employed to supply gating pulses to the controlled rectifier. The transformer has a saturating winding which is energized when the battery is connected in a reverse direction so that no gating pulses are coupled through the transformer to the gate of the controlled rectifier to turn on the controlled rectifier.

Precision rectifier with improved transient response

Abstract: A precision rectifier circuit rectifies voltage signals near zero without a loss in transient response. This is accomplished by reducing the gain of the amplifier with an additional feedback resistor. The error in the output current caused by this resistor is canceled by supplying additional current from the amplifier to the rectifier output through a second rectifier and a resistor.

Tolerable voltage control circuit

Abstract: With capacitive commutation, the controlled rectifiers of an inverter can be subjected to large voltages at the time of firing. To inhibit firing until the voltage across each controlled rectifier has decreased to safe levels, the present invention employs a switchable amplifier for each controlled rectifier which is responsive to the voltage across the controlled rectifier. The amplifier has two thresholds for switching from a firing-inhibit state to a permit-to-fire state. One threshold, established by a reference voltage and resistor divider, is set to the maximum tolerable voltage for the controlled rectifier. The second threshold permits lower level firing and because it is established by the positive amplifier feedback, this threshold is removed when the amplifier switches. Thus, the amplifier contains switching hysteresis enabling firing of the controlled rectifier at a low voltage, but insuring that if the voltage across the controlled rectifier rises above the low threshold it can still be fired within the maximum tolerable level.

Inverter commutation voltage limiter

Abstract: A voltage-limiting circuit to limit the voltage accumulated on a capacitor. The capacitor is connected serially with a controllable switching device such as a controlled rectifier and an alternating-current source, and energy is transferred from the capacitor through the controlled rectifier to the alternating current source to limit the voltage across the capacitor by gating the controlled rectifier at predetermined times. This voltage limitation system can be used to limit the voltages on commuting capacitors in inverter arrangements which include controlled rectifiers and in this application is useful to ensure against the application of excessive voltages to inverter controlled rectifiers.

Supervisory device for rectifier having semiconductor valve-type components

Abstract: A thermal replica has an RC component having a variable resistance and a capacitor connected to the resistance. The variable resistance is dependent upon the operating frequency of a rectifier having semiconductor valve-type components to an extent that the median value of the resistance increases with decreasing operating frequency when the variable resistance is connected in parallel with the capacitor and decreases with decreasing operating frequency when the variable resistance is connected in series with the capacitor. A current proportional to the current supplied to the rectifier is supplied to the thermal replica. A signal generator coupled to the capacitor responds when the voltage of the capacitor reaches a specific critical level.

A high-current metal—Semiconductor rectifier

Abstract: Schottky-barrier diodes have been in use for some time, but, in the main, only for small-signal applications. Now a large area (17K mils2) Schottky-barrier diode has been successfully fabricated for use as a high-current rectifier. The device has a rated Io of 50 amperes. Measured values of forward voltage drop at 50 amperes (dc) are typically less than 500 mV. The inherent speed characteristics of this majority carrier device were indicated in the measurement of rectification efficiency versus frequency. The efficiency of the device remained unchanged through 500 kHz. A brief theoretical review of metal-semiconductor junctions is presented and applied to the empirical characteristics of the rectifier. Chip geometry, fabrication techniques, and complete device characteristics are discussed. Specific device applications are covered with emphasis on performance and limitations.

Circuit providing fast pulse rise and fall times

Abstract: A pulse circuit for generating a pulse of square waveform at substantial current levels utilizing a power source to charge a capacitor bank which is discharged through a load and a first silicon controlled rectifier in series with the load upon the gating on of the first silicon controlled rectifier. A second silicon controlled rectifier is connected to shunt both the load and first silicon controlled rectifier after the correct pulse width is obtained and after being gated on by a delay device whose time characteristics correspond to the desired pulse width.

Direct current motor circuits

Abstract: A direct current motor circuit in which power in the motor is controlled by a main controllable rectifier whose condition is terminated by an auxiliary controllable rectifier fed with trigger signals alternately with the main rectifier. A winding coupled to a magnetic circuit inhibits the triggering of the auxiliary rectifier when the magnetic flux density in the magnetic circuit is high. The actual flux density is a balance between a flux produced by the field current of the motor, an opposing flux from an adjustable magnet and a flux produced by the armature current of the motor.

Three-phase static dc welding machine

Abstract: Three-phase static dc welding machine.. G7-. For arc-, hand- and automatic welding comprises a three-phase transformer, a rectifier with diodes and thyristors, a pulse generator, a control circuit with a feed circuit, a shunt, a choke and an operating circuit, and contains electrodes. The rectifier is connected as a three-phase, half-bridge circuit, with an auxiliary load resistor for the diode and has an auxiliary load resistor for the half bridge, an auxiliary diode rectifier and a charging choke circuit. The synchronising circuit of the pulse generator is connected to the secondary winding of the transformer and the outputs of the pulse generator are connected to the control electrodes of the thyristor group. The generator is supplied from a replenishing circuit which has a diode group and a choke. The control circuit contains a current characteristics, a nominal value display and stabilization circuit. The current regulator is connected to the shunt and the current for the working circuit of the electrodes is passed through a choke.

Static inverter circuits

Abstract: A method of regulating the output voltage of a complementary impulse commutated inverter which incorporates two silicon controlled rectifiers and has a commutation circuit which is arranged such that when the one silicon controlled rectifier is nonconductive and the other silicon controlled rectifier is conductive, firing of the nonconductive silicon controlled rectifier with a short trigger pulse of duration less than the turnoff time of each of the two silicon controlled rectifiers turns off both silicon controlled rectifiers in succession. A series of substantially similar signals are applied alternately to the gate of the one and the other silicon controlled rectifier, each signal comprising a short trigger pulse of a duration less than the turnoff time of each of the silicon controlled rectifiers followed after an interval of time by a long control pulse of duration longer than the turnoff time of each of the silicon controlled rectifiers and proportional to the required amplitude of the output voltage of the inverter. The one silicon controlled rectifier is fired when it is nonconductive and the other silicon controlled rectifier is conductive by application of the short trigger pulse of a signal to the gate of the one silicon controlled rectifier, thereby to turn off both silicon controlled rectifiers in succession. The one silicon controlled rectifier is subsequently refired by application of the long control pulse of the signal. The duration of the long pulse is varied to regulate the output voltage of the inverter. Also apparatus for carrying out the method comprising an inverter of the type stated, pulse-generating means operative to apply signals as specified alternately to the gate of the one and the other silicon controlled rectifier, and control means associated with the pulse-generating means and operative to vary the duration of the long control pulse of each signal.

Free running l-c oscillator using silicon-controlled rectifier

Abstract: There is described an oscillator circuit utilizing a tank circuit and a silicon-controlled rectifier connecting a portion of the tank circuit across a DC potential source. The gate electrode of the silicon-controlled rectifier is controlled from a voltage taken off the tank circuit through a delay network to provide the correct phase relationship between the triggering of the silicon-controlled rectifier and the voltage across the tank circuit.

Improvements in or relating to Circuit Arrangements including a Colour Display Cathode Ray Tube of the Index Type

Abstract: 1,186,067 Colour television MULLARD Ltd 16 June, 1967, No 27918/67 Heading H4F Fluctuations in the amplitude of the beam indexing signal, which is derived from a colour cathode-ray display tube 1 by means of photoelectric cell 4, are reduced by cutting off the video signal to the tube via gate 3 for a period at the beginning of each field, eg for lines 1 to 5 or 3 to 10, and deriving a signal proportional to the tube current via a gate 7, which signal is then compared with a reference potential from a source 10 in a circuit 9 to obtain a control signal which is applied to the tube via video amplifier 2 to reduce the fluctuations throughout the whole of the field In effect the control signal functions to stabilize the tube black level current at a value such that the beam indexing signal does not cease Gates 3 and 7 are controlled by a pulse generator system 8 (explained more fully with reference to Figs 3 and 5, not shown) which is triggered by both the field flyback pulses on lead 11 and the index signal from photo-electric cell 4 As illustrated, the signal representative of the tube current is derived from the indexing signal at the output of amplifier 5 In alternative arrangements, Fig 2 (not shown), the signal is obtained from (1) the output of photo-electric cell 4, (2) the output of a frequency divider in the indexing signal circuit, (3) the output of an amplifier in the indexing signal circuit which transmits the " run-in " frequency signal produced at the beginning of each scan line, or (4) the cathode circuit of the cathode-ray tube Circuit 9 includes a first peak detector which incorporates a comparator for comparing the detector output with an adjustable reference potential from source 10 The detector has an integration time long compared with the line scan period The comparator output is fed to a second peak detector having an integration time long compared with the field scan period The resulting DC control potential is applied through a DC amplifier to video amplifier 2 which is DC coupled to the cathode-ray tube A diode clipping circuit is provided to prevent the system establishing a high level of tube current when gate 7 first opens in the absence of an indexing signal Gate 5 may also be blocked for field flyback suppression Detailed transistor circuit (using known circuit techniques) for pulse generator system 8 and circuit 9 are described with reference to Figs 4 and 7 (not shown)