Showing papers on "Bridge circuit published in 1985"

DC-AC inverter with overload driving capability

Abstract: A DC-AC inverter includes a bridge converter for converting an input DC into an output AC signal which uses field-effect transistors in the bridge circuit. The characteristics of the field-effect transistors enable the bridge converter to temporarily supply power in significant overload conditions. A DC-DC converter may also be included between the DC power source and the bridge converter to provide voltage boosting, when required. Field-effect transistors are also included in the DC-DC converter for power switching. The duration and amount of overload current output by the bridge converter is monitored and when an overcurrent condition beyond a predetermined amount or duration is detected, the bridge converter is disabled. The bridge converter is reenabled at a predetermined time thereafter. A plurality of field effect transistors may be connected in parallel at each location wherein a solid state power switching device is used in the inverter to thereby multiply the power handling capacity of the inverter as a whole.

DC motor drive control device

Abstract: A DC motor is connected across the mid-points of a bridge circuit which includes a switching device in each leg of the bridge. A forward or reverse motor direction drive current flows through the motor depending on the conducting states of the switching devices. A motor drive control device operates to produce either forward or reverse drive signals for controlling the conductivities of the bridge switching devices to thereby produce a forward or reverse motor direction drive current in response to a forward or reverse drive signal respectively. The drive control device detects and measures the level of the motor drive current and when it exceeds a predetermined target value, orders a gating circuit in the path of the forward and reverse drive signals, to invert the forward and reverse drive signals to thereby reverse the direction of the motor direction drive current. This produces a braking action. The gating circuit is preferably constructed of a plurality of EXCLUSIVE OR circuits.

Capacitance monitoring bridge circuit for an enthalpy responsive device

Abstract: An enthalpy control circuit has a humidity responsive capacitive element in one leg of a bridge circuit and a temperature responsive resistance element in another leg. The circuit is powered by a pulsating DC voltage of 1 kilohertz frequency for providing DC output, from an integrator connected to the output of the bridge circuit, indicative of enthalpy. A feedback from an integrator output to the bridge circuit is provided by chopping the DC output into appropriate AC for rebalance. Another feedback circuit around an amplifier provides a reference point compensated for offset voltages brought about by conditions such as temperature affecting circuit components.

Nmr gradient field modulation.

Abstract: A circuit and method for providing high, constant amplitude sinusoidally modulated NMR gradient fields. A capacitor (56) is connected in parallel with the gradient coil (54), but separated by a switch (51). A predetermined amount of energy is stored in the capacitor (56) and then the switch (51) is closed to permit a sinusoidal oscillation of energy between the capacitor (56) and gradient coil (54). By precharging appropriately, sine wave or cosine wave oscillation can be obtained for the NMR system. The oscillation is terminated by opening the switch (51) at a time when all of the oscillation energy is in the capacitor (56). In a preferred embodiment of the invention, the switch is a bridge circuit (350), each of whose sides is a back-to-back thyristor pair (352, 354, 356, 358), so that the gradient field may be modulated either as a full wave, half-wave rectified or non-rectified sinusoidal oscillation. In one embodiment, a full-wave rectified sine wave is used, and all the oscillating energy is caught in the capacitor (56) during intervals in which 180o RF pulses are applied to generate echoes. Image data is collected during the sinusoidal oscillation.

Snubber circuit for H.F. bridge converter

Abstract: A high-frequency converter of the bridge circuit type includes a snubber circuit connected across the output terminals of the bridge for connecting pairs of charged switching capacitors with an inductor upon the switching of the transistors of the bridge to their OFF conditions. The snubber circuit includes parallel-connected oppositely-poled additional switching devices with reverse blocking characteristic connected in series with the inductor, whereby the energy of the discharging switching capacitors is temporarily stored in the inductor in a substantially loss-free manner, and is pumped in the same direction to assist in the charging of the other capacitors.

Adaptive cancellation bridge circuit

Abstract: The invention relates to an adaptive cancellation bridge circuit (ACB) for use in a single medium full duplex line termination equipment such as modems where signals are transmitted and received simultaneously along a pair of wires, the transmit and receive signal being separated in frequency. The bridge comprises a bridge network including transconductance cells (TC1, TC2 and TC3), to provide resistive, capacitive, and inductive components and these cells are electronically controlled by a current control device CC driven from a received signal (RXS) inphase and quadrature components to adjust the bridge network so that it becomes balanced and cancels a transmit signal (TXB) completely.

Transfer calibration system

Abstract: A method and apparatus for calibrating a liquid level measurement system of the type having capacitive sensors, by simulating the electrical effects of sensors in an empty condition and their interconnecting cables, at a time when the sensors are full or partially filled. By a sequential balancing technique, using a conventional bridge circuit, a precision, highly stable variable impedance device is adjusted to individually simulate the effects of each sensor and cable combination with the sensor in an empty condition. The settings of the variable impedance device are recorded, and at a later time when the sensors are no longer empty, these settings are reproduced, so as to recreate the electrical effects of each sensor cable combination one at a time. The individual effects are separately transferred into a network having a plurality of variable impedance channels, until each channel simulates the effects of a corresponding sensor and cable. This allows all of the earlier characterized effects to be simultaneously imposed on the measurement system.

Brushless D-C motor system with improved commutation circuit

Abstract: To provide for reliable commutation of a single-strand or single-line winding (25) connected in the diagonal of a transistor bridge circuit (40, 40') having four transistors (70-73) which are alternately rendered conductive in accordance with a Hall-IC rotor position sensor (32) affected by the field of a permanent magnet rotor (13), time delay capacitors (64, 66; 87) are connected to charge current sources, for example high-resistance resistors (59, 63; 88, 90, 95) to delay turn-ON of respective transistors of the bridge permitting current flow through the winding in a first direction after commutation from the other transistors (71, 72) of the bridge which are being turned OFF or blocked, so that a finite time interval or gap of no current flow is provided to reliably prevent possible short-circuit currents across the power supply buses (44, 45) if the inherent switching characteristics of the transistors are longer than the commutation interval. The capacitors are connected to a rapid-discharge circuit, for example through diodes (62) or the inherent semiconductor, such as a transistor (54) in a Hall generator-integrated circuit combination. If transistors of inherent sufficient capacity, and switching delay for switching ON are used, external capacities (87) may not be needed, the internal capacity of the transistor switching providing for sufficient time delay, with the switching-OFF being assisted by the aforementioned diode or discharge circuit (54, 89).

An AC susceptometer from 1.5 to 300K

Abstract: The authors have used an existing design of an inexpensive mutual inductance bridge circuit to build an AC susceptometer from 1.5 to 300K. The simple design of the entire system and the use of low-cost components are the special features of this system. The bridge has a sensitivity of 5*10-7 EMU which can be improved further by using superior electronic components.

A.C. power control for D.C. solenoid actuators

Abstract: An A.C. power control circuit for a D.C. solenoid actuator which may be used for a solenoid operated valve uses a triac circuit to initially apply A.C. line voltage to energize the solenoid coil of the valve to be actuated to provide valve pull-in power. A capacitor in an RC network is concurrently charged to a D.C. level, and the D.C. voltage on the capacitor is used to control the gate of the triac. After a predetermined delay as determined by the RC network charging time of the capacitor, the triac is phase controlled to produce a change in the current applied to the solenoid coil. In one embodiment, the voltage applied to the solenoid coil changes at this time from the full sine wave voltage of the A.C. source to a voltage pulse which is only a portion of the positive half of the input sine wave. This voltage produces a change in the power applied to the solenoid coil to a hold-in power level. This circuit produces a current pulse phase control of up to 90°. In a second embodiment, a phase control of up to 180° can be achieved by using a full wave bridge circuit for rectifying the A.C. to supply D.C. power to a timing circuit operating in the base circuit of a transistor controlling the energization of a photo-triac. The output of the photo-triac is, in turn, used to control the "on" time of the power triac supplying the current to the solenoid coil.

Self-compensating voted logic power interface with tester

Abstract: Each of the either normally closed or normally open switches, in an n out of m voted power interface circuit having parallel connected groups of serially connected switches, is shunted by a high impedance resistor to form a leakage path through each group of switches. A detector associated with each group of switches, and responsive to the change of impedance produced by actuation of a resistor shunted switch in the group, generates an output signal, preferably a one bit digital signal, indicative of the state of the switches in the group in response to a sequence of test signals which selectively actuate fewer switches than are required to actuate the load controlled by the power interface. Compensation for large variations in supply voltage is provided by incorporating each group of switches into a resistance measuring bridge circuit in which the digital output signal is generated by a comparator connected across the bridge. Preferably, the bridge circuits share common reference voltage generating legs.

Device for regulating rotary speed of an alternating current electric motor

Abstract: A device for independently regulating rotary speed and torque of an alternating current electric motor whose armature winding is connected as a branch of a bridge circuit balanced for a fixed rotary speed and a fixed operational voltage of the motor. The motor is controlled by a current phase adjuster having an input electrode. A polarity dependent resistive circuit including two anti-parallel diodes each connected in series with an adjustable resistor, forms a branch of the bridge circuit. A comparator in the form of an operational amplifier has its inputs connected to a diagonal of the bridge circuit and its output connected to the control input of the current adjuster. The rotary speed and torque are controlled independently by adjusting the resistors in the polarity dependent resistive means.

Fast amplitude control in twin-T bridge RC oscillators

Abstract: When a sinusoidal voltage is applied to the symmetrical twin-T bridge, the voltages at the inner nodes of the bridge have equal amplitudes and are shifted by 90°. If they are squared and summed, the resulting DC voltage can be used to control the gate of a field-effect transistor connected to the bridge. The oscillator with such a control system simultaneously has low distortion and fast amplitude transient response.

Integrated N-channel power MOS bridge circuit

Abstract: The disclosed bridge circuit is fabricated using power MOS technology. Common terminals of the bridge circuit are integrated into common regions in the implementation. Electrodes, typically coupled together in the bridge circuit, are implemented by a shared conducting region in the integrated circuit of the semiconductor chip. By integrating the elements of the circuit, less area of the semiconductor chip is required as compared to an implementation involving 4 (four) discrete elements. Diodes are fabricated across the transistors to protect the elements against reverse biasing.

Bridge circuit system

Abstract: A sensing circuit system including circuitry for sensing impedsnce variations of a variable impedance element (12). As disclosed, a bridge circuit system (11) includes a bridge circuit to which the variable impedance element (12) is coupiable. The bridge circuit system (11) further includes circuitry for detecting open circuit or short circuit fauit oonditions (16,17,18) of the variable impedance element. The variable Impedance element (12) is coupled to the bridge circuit by a connector, having two connector components (13,14), which is also operable to couple the fauit detection circuitry to the bridge circuit only when the two components (13,14) of the connector are connected together.

A self-balancing bridge for in-circuit resistance measurement

Abstract: This letter deals with a novel and versatile bridge setup for the direct measurement of in-circuit resistance. Unlike other directreading bridges, it is a balanced, active bridge. It basically employs an active RC integrator, a fixed standard resistance, and a reference voltage source. The steady-state output voltage of the integrator is found to be directly proportional to the unknown resistance. Test results show the accuracy of measurement to be of the order of 1 percent in the range of 0.4 to 60 kΩ.

Load-weighing apparatus for an elevator car

Abstract: The load-weighing apparatus faultlessly detects even smallest load variations in the lower load range. For this purpose wire strain gauges are mounted at structural parts or components of the elevator car and these structural parts or components are subjected to bending under the load to be weighed. The wire strain gauges are interconnected to form a bridge circuit. An amplifier circuit is connected at the output side of the bridge circuit and has a higher gain in the lower load range. When an input voltage corresponding to a predetermined load occurs at the amplifier circuit, the gain of the amplifier circuit is switched to a lower value. It is thus possible to detect loads throughout a greater range of loads.

Adjustment of the frequency-temperature characteristics of crystal oscillators

Abstract: The frequency-temperature characteristic of the piezoelectric resonator in a temperature compensated crystal oscillator is adjusted by the inclusion of an equivalent inductive reactance connected in series with a piezoelectric crystal resonator coupled to an oscillator circuit, with the equivalent inductive reactance being realized in the form of an inductorless Maxwell type bridge circuit containing the resonator. Such an arrangement provides a much larger variation in the temperature-frequency characteristic than can be realized with a conventional capacitor in series with the piezoelectric resonator.

Device for transformers and inductors, connected to a voltage, for measuring the clamping force for windings

Abstract: This clamping force is frequently taken by tension elements which bear against core limbs (3), for example by tensioning cover plates (11) or by tie-rods, and transferred to the windings (5). In order to measure the clamping force, use is made according to the invention of strain sensors (17) mounted in the tensioning direction on a tension element (11) on both sides of at least one core limb (3) and of strain sensors (18) mounted at right angles thereto. In each case the four strain sensors (17, 18) mounted on the tension elements (11) of the same core limb (3) are electrically interconnected to form a quadrilateral bridge circuit. Measuring leads (19) connected to the corner points of the quadrilateral bridge circuit are led out in an electrically and magnetically screened (20) fashion from a tank surrounding the core (3) and the windings (5). The device according to the invention is chiefly suitable for use in generator transformers and line transformers and guarantees timely detection of a readjustment of the clamping force for the windings possibly rendered necessary following a series of short circuits.

Shunt arrangement with power overload protection by a voltage responsive bidirectional switch

Abstract: A shunt arrangement for processing the output current of an inductive current transformer having a wide dynamic range in which, in order to provide high-precision conversion with smaller currents, a power shunt is connected in series with a precision shunt which is connected in parallel with an overvoltage protection circuit containing a switchable semiconductor rectifier and a control circuit. The rectifier changes to a conductive state if the voltage at the precision shunt reaches a limit value. The control circuit contains a symmetric voltage limiting element which is constructed as a pair of limiting diodes or as a fullwave rectifier, the output of which is connected to a reference diode. In order to check the switching state of the overvoltage protection circuit, the series circuit including the power shunt and the precision shunt is connected in parallel with a series circuit consisting of a first bridge resistor and a second bridge resistor which, together with the shunts, form a balanced bridge circuit whereby, when the overvoltage protection circuit is inhibited, bridge circuit is monitored by a window discriminator.

Device for monitoring and counting the response of a non-spark gap overvoltage arrester

Abstract: 1. Sparkover counting and monitoring device for spark-gap-less surge arresters (8), comprising a voltage-dependent resistor (1) connected into the connection, established by a conductor (9), between spark-gap-less surge arrester (8) and earth, particularly a silicon carbide resistor, a counting mechanism (5), a spark gap (2) connected in parallel with the voltage-dependent resistor (1), and a rectifier bridge circuit (3), connected in parallel with the voltage-dependent resistor (1) via a series resistor (R1), for a current meter (7), characterized in that the inputs of the rectifier bridge circuit (3) are conductively connected to the terminals of an additional resistor (R2) and the outputs of the rectifier bridge circuit (3) are conductively connected to the counting mechanism (5), a monostable flip flop (4) being connected between one of the outputs and the counting mechanism (5) and the entire circuit being accommodated in an earthed housing (10) which has two outer terminals for the conductor (9) establishing the connection between spark-gap-less surge arrester (8) and earth and preferably exhibits a window in the housing cover for reading the count and the quiescent arrester current.

Differential receive booster amplifier for telephone instruments

Abstract: An amplifier having properties of natural side tone balancing based on the utilization of a bridge arrangement, high efficiency with resulting high gain, high AC impedance and compatibility with electret microphones and electret microphone amplifiers. A matched pair of differential transistors arranged as part of a bridge circuit form a detector of the receive signal at one input versus a transmit signal which appears at both inputs in the same phase and therefore is rejected as a common mode signal. The resultant balancing of side tone and high gain finds particular application in telephone networks where the characteristics dictate the need for higher than usual receive gain or for use by auditorially handicapped users over a normal telephone network.

Low leakage, solid state a-c power contact

Abstract: A power contact with low off current for switching a-c loads in response to a logic signal includes a rectifier bridge circuit in a series with the load and the a-c power source, a MOSFET connected across the d-c terminals of the bridge, and a series RC filter circuit in parallel with the MOSFET A metal oxide varistor connected across the d-c side of the bridge protects the MOSFET from transients in the a-c circuit While this power contact is capable of switching sizable a-c currents, the leakage current with the MOSFET off is less than 1/10 of a milliamp so that it can also be used to switch loads which draw very low level currents The MOSFET is electrically isolated from the logic signal by an opto-isolator which has a unique switchable output which permits the power contact to be readily adapted for use with normally energized or normally deenergized loads

Engine control device

Abstract: PURPOSE:To simplify circuit construction in a device and decrease its error factor, by constituting the device such that an engine control system processes in its computer part a function of the control circuit of a hot-wire type air mass flow sensor (HW sensor). CONSTITUTION:A hot-wire (HW) sensor is constituted by a bridge circuit 20 consisting of a heater resistor 15, temperature detecting registor 17 and balancing resistors 16, 18 set in an intake manifold, and a difference between a set of output signals generated from this sensor is obtained by a comparator 19 and input with a crank angle signal 2 and a throttle signal 3 to a digital 1g in a microcomputer 1. While the above described set of output signals are input with a cooling water temperature signal 6 to an A/D converter 1d. And a central processing unit (CPU)1a, both controlling a proportion of electrifying time for a power supply applied to the HW sensor and applying a feedback correction to the proportion of electrifying time in accordance with a sensor output after its A/D conversion, calculates an air mass flow in accordance with the proportion of electrifying time after its correction.

A whirling hot-wire anemometer with optical data transmission

Abstract: Previous whirling hot-wire anemometers have relied on slip rings to connect the sensor to the bridge circuit. An alternative arrangement is described where a low power consumption anemometer circuit rotates with the hot wire, with direct connection to the sensor. The bridge output signal is transmitted optically by an LED to a fixed receiver, decoded and then processed normally. The system is tested in a simple experiment with homogeneous grid turbulence. The design may also be useful for remote anemometry.

Ballast circuit for a fluorescent lamp

Abstract: The fluorescent lamp (14) is connected in a bridge circuit of electronic switches T1 to T4. This bridge circuit is supplied via a series circuit consisting of an electronic switching element (TS), a current sensor (I) and an inductor (L). The signals from the current sensor (I) are compared with threshold values in a comparator (16). The switching element (TS) is alternately opened and closed so that the lamp current (iL) remains constant within a predetermined band width. The reversing of the polarity of the lamp (14) is carried out by the control mechanism (15) at relatively large time intervals of e.g. one hour. The time integral of this current is formed during one half period of the lamp current. The current of opposite polarity is maintained until its integral has reached the same value. In this way, electrophoresis on the lamp 14 is avoided. The balanced circuit can be operated equally well at different supply voltages and with lamps of different power, without having to carry out any changeovers.

Detector for absolute humidity

Abstract: PURPOSE:To make it possible to use an absolute humidity sensor having an inferior zero balance by connecting a low resistance in series to two thermistors constituting the absolute humidity sensor to adjust a difference of temperature characteristics between thermistors. CONSTITUTION:A DC constant voltage source E is connected between input terminals B1 and B2, and an output terminal B3 is connected to the input terminal of a DC amplifier 16, and an output terminal B4 is connected to the positive input terminal of the DC amplifier 16. If a temperature drift to the positive side is generated in an absolute humidity sensor 10 in case of a variance of temperature, a low resistance RC is inserted in series to a thermistor resistance R2 between the compensating thermistor R2 of a bridge circuit and the input terminal B2. If a temperature drift to the negative side is generated in the absolute humidity sensor 10, the low resistance RC is inserted in series to a thermistor R1 between the input terminal B1 of the bridge circuit and the detecting thermistor R1. Thus, the absolute humidity sensor 10 is compensated into a superior zero balance state.

Electronic circuit for the control construction of a transistor bridge circuit

Abstract: The essence of the electronic circuit for the control construction of a transistor bridge circuit of a four-quadrant speed controller on DC motors is that the best opening and closing responses of the transistors are made possible by virtue of its design, by means of which reliable and accurate response of the motor, linearity of the motor current during the transition processes, a low ripple level on the motor current and low switching losses are ensured The circuit for the control construction of a transistor bridge circuit operates in such a manner that a second transistor (T2) is always open when the motor is rotating in the first direction, and its complementary third transistor (T3) is always switched off, while a first transistor (T1) is pulse-width controlled in the required method of operation of the motor and a fourth transistor (T4) is controlled in a complementary manner with respect to the first transistor (T1) In the other rotation direction, the fourth transistor (T4) is always open, the first transistor (T1) is always switched off, the third transistor (T3) is pulse-width controlled and the second transistor (T2) is controlled in a complementary manner with respect to the third transistor (T3)

Temperature compensating circuit

Abstract: PURPOSE:To compensate for the inclination and the curve of temperature characteristics at a zero point, by superimposing the output component of a resistance bridge, wherein temperature-dependent resistors are provided on both sides of neighboring arms on an output of a strain gage bridge. CONSTITUTION:A resistor R1 and a resistor RA having large temperature dependency are connected in series. A resistor R2 is connected to the series-connected resistors R1 and RA in parallel, and Ralpha is formed. A resistor RB having large temperature dependency is connected to a resistor R3 in series. A registor R4 is connected to the series-connected resistors R3 and RB in parallel, and Rbeta is formed. A bridge circuit is formed by Ralpha, Rbeta, and the resistor R5 and R6. A feedback resistor R8 is connected between the inverted input terminal and the output terminal of an operation amplifier OP1. A differential amplifier is formed by an operation amplifier OP2 and resistor R9-R12. By selecting suitable values for the resistors R1-R4, temperature characteristics can be imparted to an output voltage VL of the operation amplifier OP1, so that the inclination and curve of the temperature characteristics in an output voltage Vin of a strain gage bridge are offset to each other. Thus temperature compensation can be performed.