Showing papers on "Bridge circuit published in 1994"

Bridge circuit magnetic field sensor having spin valve magnetoresistive elements formed on common substrate

Abstract: A magnetic field sensor uses four individual magnetoresistive spin valve elements electrically connected in a bridge circuit. The spin valve elements are lithographically formed on the same substrate with their free layers having their magnetization axes parallel to one another. An electrically conductive fixing layer is formed on the substrate but is insulated from the spin valve elements. The application of current through the fixing conductor during fabrication of the field sensor fixes the direction of magnetization of two of the pinned layers to be antiparallel to the direction of magnetization of the other two pinned layers. The bridge circuit output voltage is responsive to an external magnetic field in the plane of the sensor. By appropriate fixing of the direction of magnetization of the pinned layers during sensor fabrication, and appropriate connection to the input and output leads, the bridge circuit output voltage is a measure of either the magnetic field or field gradient. The fixing conductor, or a separate current strap formed on the substrate, can be used to pass an unknown current over the sensor, in which case the bridge circuit output voltage is a measure of the unknown current.

Low frequency, pulsed, bipolar power supply for a plasma chamber

Abstract: The invention relates to a bi-polar power supply for a plasma chamber including an adjustable DC power supply having a positive output terminal and a negative output terminal. A transistor bridge circuit having two input bridge terminals is coupled to the positive and negative output terminals. Two bridge output terminals of the transistor bridge are coupled to the plasma chamber. A current detector is coupled to the two bridge output terminals for detecting the current flowing to the plasma chamber and controlling the transistor bridge circuit to provide a bi-polar power supply to the plasma chamber.

Piezoresistive input device

Abstract: An input device for computers or electronic games using piezoelectric elements. Four piezoelectric devices are mounted on a base in positions ninety degrees apart. A user actuation element, such as a directional control pad and or a joystick is pivotally disposed on the base above the piezoelectric sensors. A biasing element such as a spring, foam or rubber element is positioned between the actuation element and the base to support the actuation device in a neutral position when no face is being applied by a user to also return the activation element to its neutral position after a user's force is removed. Opposing sensors are connected to a bridge circuit such that in the neutral position of the actuation element the output voltage of the bridge is one half of the input voltage. As the user applies a force to the actuation device, the resistance of one or the other (opposing) piezoresistive device will decrease and accordingly drive the output of the bridge circuit either towards the input voltage or ground, depending on which sensor the user is activated. Additionally a piezoresistive device constructed according to the present invention uses a conductive foam overlayed on top of a series of circuit traces which describe open circuits. As the conductive foam is compressed, it will complete the circuit of the circuit traces and provide an output voltage varying with the compression of the foam.

Apparatus and method for determining the status of data buffers in a bridge between two buses during a flush operation

Abstract: A bridge circuit adapted to be associated with first and second bus circuits which bridge circuit includes a first path including a plurality of buffers for storing data or addresses being transferred from the second bus to the first bus, a circuit arrangement for detecting that an interrupt of a presenting-running operation has occurred, a circuit arrangement for determining the state of the plurality of buffers when an interrupt occurs, and apparatus for flushing only those buffers of the plurality which were storing data for transfer when the interrupt occurred.

Self-sensing control as applied to a PZT stack actuator used as a micropositioner

Abstract: Self-sensing actuation is a control technique that can be applied to many smart materials including piezoceramics. It involves extracting a sensing signal from the actuating material by use of a bridge circuit, then properly feeding this signal back to improve the actuator's performance. The research presented is concerned with the feasibility of applying this technique to a soft PZT stacked actuator used as a micropositioner. The result of applying this control technique was a reduction of the micropositioner's decay time from over 1 ms to under 0.3 ms. A major contributor to the success of this research was the insertion of a nonlinear element in the self-sensing bridge which negated the nonlinear effects of the PZT stack thus enabling an increase in the self-sensing signal-to-noise ratio.

Automatic balancing of linear AC bridge circuits for capacitive sensor elements

Abstract: Conventional bridge circuits are balanced by means of mechanical changes of trimming capacitances and resistances. It is a well known fact that this can be very difficult in many situations, e.g. due to electrical interference between the bridge circuit and the human body or some mechanical part of the screwdriver used. There may also be physical constraints prohibiting mechanical changes of some bridge elements. To avoid these problems, the balancing procedure should be automatized. In this article an automatic method for bridge circuit balancing, based on a digital control signal, is presented. Ordinary ac-bridge circuits are nonlinear with respect to changes of the capacitive sensor element. Using some standard operational amplifiers it is easy, however, to obtain a linear bridge circuit output. A theoretical model of the linear bridge circuit is derived. The excellent performance of the linear bridge circuit predicted by theory is verified by practical experiments. >

The use of capacitance in the measurement of angular and linear displacement

Abstract: This paper describes the use of capacitor bridges in instrumentation for the measurement of relatively large angular and linear displacements. The particular feature of interest lies in the use of printed circuit board technology which allows repeatability at low cost associated with a rugged overall structure. Two possible electronic configurations are described, one being direct and the other using feedback in which the output depends only on the ratio of the capacitances. Experimental results are given for examples of angular and linear devices. They show that this approach readily yields devices with an accuracy of /spl plusmn/1% and indicates that results considerably better than this are ultimately possible. >

Pulse width modulation speaker amplifier

Abstract: An open-loop speaker amplifier and a dynamic range reduction circuit are disclosed. The speaker amplifier includes a bridge driver and a bridge circuit. The bridge circuit includes a first set of switches and a second set of switches. When the first set of switches are activated, a positive current flows through a speaker load. When the second set of switches are activated, a negative current flows through the speaker load. The bridge driver generates a pulse width modulated signal and a delayed pulse width modulated signal to drive the first and second set of switches of the bridge circuit responsive to a modulation signal. The modulation signal may be, for example, a plurality of pulse code modulated samples representing sound. The dynamic range reduction circuit modifies a selected signal to reduce the dynamic range of the sound reproduced based on the modulation signal. The selected signal is either the modulation signal or a reference signal. In one embodiment, the dynamic range reduction circuit modifies the selected signal by processing the selected signal based on a smooth saturating function. In another embodiment, the dynamic range reduction circuit modifies the amplitude of the reference signal based on an envelope size of the modulation signal.

Power transistor module wiring structure

Abstract: In packaged bridge circuit modules with power switching transistors such as IGBT's, internal wiring inductance can cause switching voltage spikes and imbalance between switching transistors. Upon inclusion of suitably arranged and configured inductance elements, internal wiring inductance can produce a counter-electromotive force during switching. To this end, an internal connecting terminal may branch from an output terminal, a bridge-shaped internal connecting terminal may be connected between an emitter circuit pattern of one power transistor and a collector circuit pattern of another power transistor, or signal terminals as auxiliary emitter terminals of two power transistors may be connected to an inductance providing region in a current path of an emitter circuit pattern.

Mass flow sensor

Abstract: A mass flow sensor is capable of accurately measuring a mass flow irrespective of changes in the ambient temperature. The mass flow sensor includes at least one heating resistor disposed on a portion of a sensor pipe through which a fluid to be measured flows and a housing for the sensor pipe. The heating resistor and a temperature sensitive resistance constitute a bridge circuit. The temperature sensitive resistance is disposed in the housing. The resistance of the sensor changes in accordance with the change in the temperature of the housing to thereby adjust the change in the resistance of the heating resistor. Further, an improved temperature sensitive matching resistor is suitably used in the mass flow sensor, in which a plurality of temperature sensitive resistances having equal characteristics are integrated.

Drive circuit for electroluminescent lamp

Abstract: A circuit for providing AC power to an electroluminescent lamp powered by a battery comprises a high frequency oscillator through a control to drive a fly back voltage regulator comprising an inductor powered by a relatively low battery voltage and coupled to ground through a switching transistor. A capacitor coupled to the inductor through a diode is charged by the repetitive charge and discharge of the inductor when the transistor is switched ON and OFF at high frequency by the high frequency oscillator. The charge in the capacitor is dithered about a high DC voltage, such as 100 VDC, by sensing the charged voltage for periodically turning the transistor ON and OFF accordingly. A bridge circuit receives two pairs of like lower frequency square wave pulse signals of opposite polarity from a low frequency oscillator. Each signal is applied to a different one of two series connected legs of two opposite like branches, each branch coupled between the high DC voltage and ground, each leg containing two switching FET transistors and a current source. An electroluminescent lamp is connected between the legs in each branch. One of the legs in each branch is alternately turned ON and the other leg turned OFF by the square wave signals to provide the equivalent of an AC signal to the electroluminescent lamp in opposing directions, thus doubling the value of the peak stepped up DC voltage.

Analysis, design, and implementation of an AC bridge for impedance measurements

Abstract: The paper reviews the digital AC bridge. A more accurate and thorough analysis of the bridge is presented. Based on the analysis a simple adaptive algorithm is proposed in order to ensure fast conversion. In addition, a new design of the bridge, based on the TMS 320C25, is given. The system is implemented with the Dalanco Spry model 25 DSP board, on a software system designed whereby an IBM PC host computer provides control of the bridge. Experimental results are presented. >

Thermal-type flow sensor

Abstract: A heater-heat sensor type thermal flow sensor including a substrate installed in a fluid path, a channel formed on a part of the substrate; a bridge suspended over the channel; a heater constructed with an electric resistor formed on the bridge; a temperature sensor for measuring the temperature of the heater which is constructed with another electric resistor situated on the bridge and measuring the temperature of the heater; and a fluid temperature sensor constructed with still another electric resistor formed on a position of the substrate not thermally affected by the heater There is a bridge circuit including the temperature sensor for measuring the temperature of the heater, the fluid temperature sensor, and first and second resistors both installed outside of the fluid path A control circuit is provided to control the voltage applied to the heater in accordance with the output of the bridge circuit The heater and the heat sensor are superposedly formed on the bridge through an interlayer insulating film in order to substantially eliminate the difference between the temperatures of the heater and heat sensor A temperature compensating circuit is connected to the output stage of the control circuit

Improved semiconductor bridge explosive device

Abstract: This invention discloses a method of fabricating an electroexplosive device which utilizes a semiconductor bridge (292) as an ignition element. The semiconductor bridge (292) is electrically connected to a metal header (100) by a small, low resistance contact to the extension of bridge material and through an insulating silicon substrate (270) to a eutectic bond (260) created by gold plating (350) on the metal header (100) and the silicon. The second electrode (360) of the bridge circuit is connected via wire bonds (130) to one or two conducting pins (110) which penetrate the metal header (100) and are insulated by surrounding glass (120). The design allows the use of standard semiconductor assembly methods. Since small pads of electrical material are used for electrical contact, the die size is small. A redundant connection via two conducting pins (110) insulated from the header (100) to one electrode (360) of the semiconductor bridge allows a post assembly test of the integrity of the wire bonds.

Bridge circuit for driving an inductive load with a shoot-through prevention circuit

Abstract: A bridge circuit, intended for use as a PWM driver of an inductive load, includes at least one source driver transistor connected in series totem-pole fashion with a sink driver transistor. A base resistor is connected from base to emitter of one of the driver transistors. This totem pole circuit is connected across a pair of DC supply conductors. A protective fly-back diode is connected across the one driver transistor. An auxiliary resistor is connected from the base of the auxiliary transistor to the emitter of the one driver transistor. When a fly-back diode across the one driver transistor conducts, the one driver transistor tends to conduct in the reverse direction and to store charge that in a subsequent period leads to shoot-through currents through the source and sink drivers. The auxiliary transistor turns on only when the fly-back diode conducts and shunts the base-collector of the source transistor, preventing its turning on and storing charge, and thus preventing potentially damaging shoot-through current through the driver transistors. The added auxiliary components do not cause additional power being drawn from the supply source, and therefore do not cause additional heating in the integrated circuit in which the bridge circuit may be formed. A pair of such half wave totem pole circuits may be paralleled to form a full wave bridge.

Strain gage sensor with integral temperature signal

Abstract: A strain gage pressure sensor (12) having a resistive bridge circuit (76, 78, 80, 82) from which is measured both the applied pressure and the temperature of the pressure sensor (12). A constant voltage (VBRIDGE) is provided across the bridge circuit (76, 78, 80, 82) such that any temperature caused changes in the resistance of the bridge circuit (76, 78, 80, 82) are reflected in the flow of a bridge current (IBRIDGE) through the bridge circuit (76, 78, 80, 82). A sense resistor (36) is electrically coupled to the bridge circuit (76, 78, 80, 82) such that any change in the bridge current (IBRIDGE) causes a change in the voltage drop across the sense resistor (36). The voltage drop and the pressure output signal are digitized and suitably processed resulting in a highly accurate, corrected pressure output for use with suitable pressure instrumentation.

Circuit arrangement for a power steering system with motor drive

Abstract: A circuit arrangement for a power steering system with motor drive can be reduced in size in order to lower production costs. A shunt resistor (43) and a bridge circuit (44) which has semiconductor steering devices (Q1-Q4) on the wiring pattern (P) can be arranged on a metal baseplate (10) on which a wiring pattern (P) is formed with the interconnection of an insulating layer. A microcomputer (55) and a peripheral device, preferably a drive circuit (47), a motor current detection device (48) and the like can be mounted on an insulated printed circuit board (2, 2A). The metal baseplate (10) and the printed circuit board (2, 2A) overlap one another with a predetermined distance being maintained between them. The heat which is output by the semiconductor switching devices and the wiring pattern is conducted away via the metal baseplate.

Hysteresis-free current sensor - has soft magnetic core for coupling prim. and sec. coils, generator for periodically magnetising to positive and negative saturation and sample=and=hold circuit for acquiring sec. current to form average voltage drop

Abstract: The current sensor has an unslotted magnetically-soft core, a primary coil (1) carrying the measurement current, and a secondary coil (2) coupled with the primary via the core. A circuit is provided for the periodic magnetisation of the core to saturation, and a sample and hold circuit (4) which detects and stores a voltage drop proportional to the secondary current and a stage which forms the mean of two voltage drop measurements. The voltage sampling frequency is at least three times the frequency of the measurement current and the core magnetisation system is a bridge circuit generator. USE/ADVANTAGE - For measuring a.c. and d.c. currents. Measurement errors caused by hysteresis of magnetic core are eliminated using device having small dimensions achieved.

Apparatus for reproducing sound with a reduced dynamic range

Abstract: An open-loop speaker amplifier and a dynamic range reduction circuit are disclosed. The speaker amplifier includes a bridge driver and a bridge circuit. The bridge circuit includes a first set of switches and a second set of switches. When the first set of switches are activated, a positive current flows through a speaker load. When the second set of switches are activated, a negative current flows through the speaker load. The bridge driver generates a pulse width modulated signal and a delayed pulse width modulated signal to drive the first and second set of switches of the bridge circuit responsive to a modulation signal. The modulation signal maybe for example, a plurality of pulse code modulated samples representing sound. The dynamic range reduction circuit modifies a selected signal to reduce the dynamic range of the sound reproduced based on the modulation signal. The selected signal is either the modulation signal or a reference signal. In one embodiment, the dynamic range reduction circuit modifies the selected signal by processing the selected signal based on a smooth saturating function. In another embodiment, the dynamic range reduction circuit modifies the amplitude of the reference signal based on an envelope size of the modulation signal.

Hybrid circuit and data communication apparatus

Abstract: The balancing bridge circuit is provided between a four-wire circuit and a two-wire circuit, to provide a thin-type balancing bridge circuit having satisfactory transmission characteristics and a MODEM and an exchange and a repeater of a telephone circuit having this balancing bridge circuit built therein. The transmitting terminals of the four-wire circuit and the connection points of the balancing bridge circuit are connected together through the photo-coupler. The receiving terminals of the four-wire circuit and the connection points of the balancing bridge circuit are connected together through the photo-coupler. The terminals of the two-wire circuit are connected to the connection points of the balancing bridge circuit. By the presence of the compact photo-couplers, it is possible to ground the transmitting terminal and the receiving terminal together. Common-mode noise reaching the terminals is not transmitted to the receiving terminals.

Sensor arrangement for magnetoresistive sensor element

Abstract: The sensor arrangement includes a bridge circuit (B) with four, paired diagonal bridge elements (Eij) in two parallel-switched bridge branches (21,22) between connection points (A1,A2 for the current (Io). At least one of the bridge elements (E11,E11') is formed as a sensor element with a large magnetoresistive effect. The sensitivity of at least one of the bridge elements (E11,E11') w.r.t. the external magnetic field is different w.r.t. the magnetic sensitivity of the other bridge element (E22,E21').

Temperature detector for power converter

Abstract: PURPOSE:To accurately detect the temp. of a semiconductor switching element (IGBT) so as to follow the instantaneous fluctuations thereof. CONSTITUTION:Fly wheel diodes 25, 26 are integrally incorporated in the IGBTs 23, 24 of the inverter bridge circuit constituting an inverter device. The forward direction current of the diode 26 is detected by a current transformer 33 and forward direction voltage is detected by an insulating amplifier 28 and a diode 29. Since the forward direction current/voltage characteristics of the diode 26 are changed according to temp., the temp. of the diode 2b is contrarily estimated from those values by a function operator 32 to estimate the temps. of the IGBTs 23, 24.

CATV signal splitter

Abstract: A signal splitter circuit accepts an input signal and conveys the input signal to two output ports The circuit operates with minimal attenuation, throughout a very wide bandwidth, and also effectively isolates the output ports from each other The signal from the input port is coupled to an autotransformer, and the ends of the autotransformer are connected to the respective output ports A bridge load circuit which includes a transformer winding and a load connected in parallel, is inductively coupled to the autotransformer The bridge load circuit has no connection to the splitter circuit, other than through the inductive coupling The splitter circuit also includes inductors in series with the output ports and capacitors in parallel with the output ports The circuit provides a balanced bridge circuit which cancels signals traveling between the output ports, and the inductors and capacitors provide impedance matching between the input port and output ports The arrangement of the bridge load circuit places the leakage inductance of the autotransformer outside the effective path of the bridge load circuit, so that the leakage inductance cannot cause unwanted and unpredictable phase shifts at high frequencies

Forced, resonant degaussing system and method

Abstract: A degaussing system for color monitors is disclosed. During a degaussing cycle, the system successively reverses the coupling in a bridge circuit between a degaussing coil and a storage capacitor so as to generate oppositely directed degaussing currents through the coil. To insure that the residual magnetism after degaussing is substantially zero, feedback signals are developed in a feedback circuit and applied through a control circuit to the bridge circuit to successively decrease the coil's current magnitudes until they reach a predetermined threshold. Simultaneously, the feedback signals are adjusted to cause the time-integrated current in one direction of the coil to substantially equal the time-integrated current in the other coil direction.

One switch multi-phase modulator

Abstract: An electrical apparatus comprises a bridge circuit (10) having a plurality of rectifier legs (12a-c) electrically connected in parallel. Each of the rectifier legs (12a-c) comprises a first and second rectifier (18a-c, 19a-c) coupled in series and having an input node (22a-c) therebetween. The electrical apparatus further comprises a switch (24), having a control input (26), a power input (28), and a power output (30), coupled in parallel with the bridge circuit (10), and a controller (32) having a control output (34) coupled to the control input (26) of the switch (24) for regulating the opening and closing of the switch (24). When the bridge circuit (10) is coupled to the disassociated neutral terminals (38a-c) of a wye wound electrical device (36), the controller (24) modulates the switch (24) to provide a current controlled soft start of the device (36) including acceleration and breaking of the device.

Method and apparatus for sensing an input current with a bridge circuit

Abstract: A current sensor includes first and second branches interconnected by a center conductor magnetically coupled to an annular current comparator for producing an output signal related, in magnitude and phase, to an input current. The input current divides, according to a predetermined relationship, between the first and second branches such that the current in the center conductor interconnecting the first and second branches is also related to the input current. A current is induced in the annular current comparator in relation to the current in the center conductor and, thus, in relation to the input current. Secondary windings are wound about and magnetically coupled to the annular current comparator for producing an output signal responsive to the current induced within the annular current comparator.

A Suitable Single-phase PWM Current Source Inverter for Utility Interactive Photovoltaic Generation System

Abstract: A suitable single-phase inverter for the utility interactive photovoltaic generation system is proposed. The single-phase PWM current source inverter has a novel circuit configuration which is added a auxiliary branch to the normal single-phase bridge circuit. In order to reduce the size and weight of the dc reactor, a double frequency parallel resonance circut (LC tank circuit) is inserted in the dc side of the inverter. In result, the double frequency voltage appeared in the dc side of the inverter due to the pulsation of the single-phase instantaneous power is perfectly suppressed by the tank circuit. The constant dc current without pulsation is supplied from PV array to the inverter. The inverter provide a sinusoidal ac current for domestic loads and the utility line with unity power factor.The virtual maximum power of the PV array can be obtained without any feedback control. In the system, the PV array can play an important role as a current-limitter by its V-I characteristics. Computed waveformes by simulation are shown. The excellent inverter equipment will be realized with smaller size and lighter weight than a conventional inverter.

Balanced bridge saw filter

Abstract: The invention relates to a SAW filter comprising a first and second pair of substantially equivalent SAW transducers electrically coupled to form a bridge circuit. Each of the transducers of the first pair of transducers have a center frequency which is slightly different to the center frequency of each of the transducers of the second pair of transducers. The product of the static capacitance of the first pair is the same as the product of the static capacitance of the second pair. In use, signals input to the filter and having a frequency within the passband of the filter are coupled to the output of the bridge circuit via one or other or both arms of the bridge, as in normal bridge circuit operation. However, out of band signals are blocked since all the transducers are equivalent capacitors having the same capacitance (i.e., static capacitance). Thus, transmission of out of band signals through the filter is inhibited by the balanced nature of the bridge.

Boost-buck rectifier bridge circuit topology with diode decoupled boost stage

Abstract: A boost-buck rectifier bridge circuit topology having two diode decoupled boost stages is formed as an H-shaped bridge with the alternating voltage source comprising the center leg and the first and second H-shaped bridge arms comprising a series connected SCR and bridge diode in each of the legs and a third and fourth bridge diode in the respective third and fourth arms of the H-shaped bridge The first boost stage is coupled between the junction of the first SCR and first bridge diode and the negative polarity DC voltage bus and a second boost stage is coupled between the positive polarity DC voltage bus and the junction of the second SCR and second bridge diode in the second arm of the H-shaped bridge so that the first boost stage is decoupled by the first bridge diode and the second boost stage is decoupled by the second bridge diode whereby the load current delivered by the circuit is carried solely by the bridge diodes and not the boost stage switching devices

Inclination and acceleration detector with fluid sensor element - has high sensitivity temp.-responsive resistors in fluid-filled capsule with bridge circuit signal evaluation

Abstract: An inclination and acceleration sensor is formed by three parallel resistive elements (1, 2) supported by contact pillars and aligned in a common plane with equidistant spacing. The assembly is enclosed in a sealed capsule filled with an inert gas and the central resistor (1) is maintained at a constant temperature via a regulated electrical supply. The outer resistors (2) form two arms of a bridge circuit which receives a constant input voltage (Ukonst) and whose out-of-balance condition is registered by a galvanometer (3) when the initially isothermal field is disturbed by a gravitational or inertial field. USE/ADVANTAGE - Has many applications in safety devices and for determination of critical parameters, e.g. impact registration, inertia forces relevant to land, sea, air and space vehicles, vibration in machines, automatic braking, seismology etc.