Showing papers on "Precision rectifier published in 1984"

Diversity signal strength indicator and site selection apparatus for using same

Abstract: A diversity signal strength indicator for transmission site selection in a cellular-like mobile radio system produces an output strength indication signal which is proportional to the logarithm of the average strength of two diversity input signals. The two input diversity signals are time multiplexed together to form a composite signal, and a log amplifier/envelope detector then produces an intermediate log signal which is proportional to the logarithm of the envelope of the composite signal. The intermediate log signal is then operated on by a peak detector to produce a peak intermediate log signal which is then passed through a low pass filter to produce an output strength detection signal proportional to the average of the intermediate log signal and thus proportional to the logarithm of the average strength of the diversity input signal. The peak detector is preferably comprised of a capacitor charged through a diode for storing the peak levels of the intermediate log signal and a current source for draining the charge on the capacitor at a substantially uniform rate which is independent of the magnitude of the peak signal which is stored during time periods between peak signals. In another embodiment, the time multiplexed composite signal is first detected and then passed through a squaring circuit, a low pass filter and then a log amplifier to produce an output indicator circuit proportional to the logarithm of the average strength of the input diversity signals. The diversity signal strength indicator is employed in combination with a site selection system for selecting suitable ones of a plurality of transceiver sites for actuation and reception of signals to be transmitted to a remote portable unit.

Protection system for immunizing a controlled d-c power supply against a-c line voltage interruptions

Abstract: When a d-c bus voltage is produced by rectifying applied a-c power line voltage in a rectifier bridge (such as a phase-controlled SCR rectifier bridge), controlled by a feedback loop which compares a feedback signal representing the d-c bus voltage with a command signal representing a desired set point level and from the comparison automatically maintains the bus voltage at the set point level, unwanted a-c line voltage interruptions may have a deleterious effect on the rectifier bridge itself and on a load driven by the bus voltage. This occurs because during a power interruption (when the bus voltage drops) the command signal causes the feedback loop to impose a control on the rectifier bridge which attempts to increase the d-c bus voltage back to the magnitude represented by the command signal. When power is subsequently restored, the d-c bus voltage will suddenly increase very sharply and may destroy electrical and/or mechanical components in the system. Immunization against the effects of the power interruptions is obtained by substituting the feedback signal for the command signal, during the occurrence of a power interruption, which will shut the rectifier bridge down and will force it to produce only a minimum amplitude d-c bus voltage when power is later restored. After power resumes, the rectifier bridge will be controlled by an acceleration regulating circuit so that the bus voltage gradually increases, at an adjustable rate, back up to the desired level set by the command signal.

Integrated circuit for driving a D.C. motor having operational modes

Abstract: The present invention relates to an integrated circuit for driving a d.c. motor with radio control comprising a receiving circuit for receiving and detecting certain signals transmitted from a transmitter, an amplifier for amplifying an output signal of said receiving circuit, a peak detector for converting the said amplified audio signal into a d.c. voltage, a comparator which have a hysteresis character dependent on the output level of the peak detector, a voltage regulating circuit supplying a stabilized voltage into all other components, and a direction control circuit to generate logic control signals deciding actual operation mode of the d.c. motor and motor driving circuits to produce motor driving signals by the output signal of the direction control circuit.

Direct current coupled peak to peak detector circuit

Abstract: A peak-to-peak signal detector circuit is disclosed. It can be directly coupled and rejects any d-c component associated with the signal without requiring a coupling capacitor. The input is applied to separate positive and negative peak detectors the outputs of which are subtractively combined in an op-amp. A circuit application as a drop out detector in an optical disc system is detailed.

Frequency-doubling circuit

Abstract: Frequency-doubling circuit for doubling the frequency of a fundamental wave with the aid of a first full-wave rectifier circuit (AD1) in which, to suppress the direct current component and the unwanted harmonics at 4K wherein K = 1, 2, 3, ... times the frequency of the fundamental wave in the output signal of this first full-wave rectifier circuit the fundamental wave is applied in phase-quadrature to a second full-wave rectifier circuit (AD2) whose output signal is subtracted from the output signal of the first full-wave rectifier circuit. An integrable realization of the phase-quadrature relationship between the fundamental waves applied to the full-wave rectifier circuits by means of capacitive loads is described, the amplitude relationship of these fundamental waves being stabilized at mutually the same values by means of a gain control loop.

Overvoltage protection circuit for synchronous machinerotor

Abstract: The rotor of a brushless synchronous machine, such as an alternator exciter machine, includes a field winding and a rectifier for applying full wave rectified power to the field winding. To protect the rectifier from excessive inverse voltages when such voltages are induced in the field winding, for example during motor starting, alternator paralleling, etc., the present invention employs an excessive voltage sensor and a triggerable bypass circuit for bypassing such excessive inverse voltage from the rectifier when the sensor senses such excessive inverse voltage. The sensor preferably includes a solid state relay capable of assuming either of two output conditions, depending on the magnitude, and with a prescribed input circuit, the polarity, as well, of a voltage induced in the field winding. The bypass circuit includes a pair of triggerable switches, such as SCR's or triacs, which operate in response to the output from the relay effectively to short circuit the rectifier when an excessive inverse voltage occurs; and the SCR's preferably are self commutating to open the bypass circuit in response to a polarity change of the induced field winding voltage and/or a prescribed input to the rectifier.

Capacitance type converter

Abstract: PURPOSE:To remove the influence of stray capacitance by connecting a variable capacitor corresponding to a capacitor to be measured and a reference capacitor to the 1st rectifying circuit, controlling the oscillators of both the capacitors by the output of the 1st rectifier circuit, and obtaining an output from the 2nd rectifier circuit for the reference capacitor. CONSTITUTION:Respective fixed electrodes 16, 17 of variable and reference capacitors 11, 12 in a detecting part 10 are connected to the inverted input terminals of operational amplifiers A1, A2 of detecting circuits 51, 52 constituting the 1st and 2nd rectifier circuits respectively and the positive input terminals are connected to a common electrode 15 in the detecting circuit 10 through a reference point oscillator 20. On the other hand, the outputs of the amplifiers A1, A2 are fed back to respective inverted input terminals through feedback circuits consisting of resistors R3, R4, etc. respectively. A DC voltage from the amplifier A1 and a negative reference voltage are inputted to the inverted input terminal of an operational amplifier A3, the oscillator 20 is controlled by the output of the amplifier A3 and an output EOUT related to a capacitance value of the capacitor 11 corresponding to the capacitance to be measured is extracted from the circuit 52.

Converter having a DC voltage intermediate circuit for supplying a rotating-field machine

Abstract: In the case of the converter according to the invention, the DC voltage intermediate circuit (2) is connected to the mains (R, Y, B) via an uncontrolled rectifier (1). An invertor (7) is connected in parallel with the rectifier (1) for energy feedback, which invertor (7) is connected to the mains via an autotransformer (8). In order to reduce the outlay for the invertor (1) and in order to improve the efficiency, the connecting lead between the rectifier (1) and the DC voltage intermediate circuit (2) is to be interrupted, using a switch (6a, 6b), during energy feedback when the rotating-field machine is being operated as a generator.

Circuit for the driving mode and braking mode of electrical traction vehicles

Abstract: A power-system compatible multi-power system current convertor which is capable of feedback and uses only one convertor stage is aimed for. It is based on a fully-controllable power system rectifier bridge, which can be pulsed, in a Graetz configuration with a quenching bridge in a Graetz rectifier. This circuit is to be, in addition, universally applicable for DC voltage mode and also as a power-system or resistance brake for braking mode. For this purpose, a further pair of thyristor branches (13.2/13.1) are arranged in the same direction in parallel with the two pairs of thyristor branches (4.1/4.2 and 4.3/4.4). At the divider point (A') of said second pair of thyristor branches (13.2/13.1), a braking resistor (14) with a further connection to one of the AC voltage terminals (C) of the power-system rectifier bridge is located. The second pair of thyristor branches (13.2/13.1) is connected on the negative side to the negative DC voltage terminal (D) of the power-system rectifier bridge and on the positive side is connected to the connection, which can be disconnected by means of a switch (9), of the positive DC voltage terminals (B) of the two pairs of thyristor branches of the power-system rectifier bridge downstream of the switch (9).

Reference voltage generating circuit for a/d conversion

Abstract: PURPOSE:To attain the reproduction having more natural black and white contrast, by detecting the highest potential and the lowest potential from an input analog signal to be A/D-converted for extracting them, and using a voltage obtained by resistor-dividing a potential difference between both potentials with as a reference voltage for A/D conversion. CONSTITUTION:A video signal Vg is given to a high level peak detecting circuit 7 comprising a diode 9, resistor 10, and a capacitor 11, and a low level peak detecting circuit 8 comprising a diode 13, resistor 14 and a capacitor 15. An output of the high level peak detecting circuit 7 is inputted to a buffer amplifier comprising a transistor (TR) 12 and an output of the low level peak detector 8 is inputted to a buffer amplifier comprising a TR16. Resistance dividing resistors R01,R1,R2...Rk-2,R0 to quantize the video signal into k-set are connected between the emitters of the TRs 12 and 16.

Starting circuits for discharge lamps

Abstract: A starting circuit for discharge lamps includes a current limit device, a full wave rectifier circuit and a Cockcraft-Walton's circuit which are connected between a d.c. discharge lamp having a cathode and an anode and the input terminals of an a.c. power source. Moreover, the Cockcraft-Walton's circuit is constructed by sharing a rectifier with the full wave rectifier circuit and a preheating circuit is provided for the cathode and includes another rectifier of the full wave rectifier circuit and a switching device.

Optical indicator device

Abstract: An optical indication circuit in which a light-emitting diode is included in the feed current path of an IC which is energized via a dissipation resistor and a rectifier diode directly from the alternating voltage supply.

Automatic sensitivity adjustment and audio muting for aircraft marker beacon receiver

Abstract: An improved aircraft marker beacon receiving and indicating system is provided, which automatically responds to the amplitude of the received signals to provide reduced sensitivity and muting of audio output after initial sensing and indication of proximity to the beacon and during a timed period of passing over the beacon in closest proximity thereto. The improved system employs an electrically controllable radio frequency attenuator between the antenna and the input of the receiver. The attenuator is controlled by a control voltage of predetermined duration from a trigger actuated, timed control signal generator. The control signal generator is triggered by direct current trigger pulse signals from an audio frequency peak detector. The peak detector derives its input from an operational amplifier coupled to receive audio frequency signals from the demodulator output of the tuner portion of the receiver. The control voltage from the timed control signal generator is applied to the reference input terminal of the operational amplifier to mute the loudspeaker or headphones coupled with the output of the operational amplifier, as well as to the attenuator to reduce the sensitivity of the receiver.

Active full-wave rectifier detector circuit

Abstract: Active full-wave rectifier circuit for a current transformer used for example in an earth leak detector circuit and comprising active components such as operational amplifiers and transistors to detect and process relatively weak output voltages.

Active double-sided rectifier circuit

Abstract: Active double-sided rectifier circuit for a current transformer used for exemple in an earth leak detector circuit and comprising active components such as operational amplifiers and transistors to detect and process relatively weak output voltages.

Stability of Controlled Rectifiers: Phenomena and Experiment

Abstract: A new approach to the experimental investigation of the steady-state stability of controlled rectifiers based on the measurement of the angle between sequential ignitions of the valves is discussed. The statistical treatment of the experimental data shows a special dependence on the deviation of the firing impulses and the amplifier gain factor. Such a dependence provides a physical definition for the rectifier stability and its boundaries. The experimental investigation of the increasing of the impulse deviation with an increase of the gain factor has shown that the physical reason for such deviation change and rectifier instability is an increase of a varying component in the control voltge of the firing system input. Analyzing the data about the well-known forms of the rectifier's instability?harmonic, ripple, and low-frequency?it can be concluded that the physical reason for the stability loss is the same: increase of alternating component in the firing control voltge. In conclusion, a new classification of rectifier instability forms is discussed.

Impedance converting amplifier

Abstract: A transimpedance amplifier allows an optical transmitter and receiver to be in close proximity to each other without fear of overloading the receiver. The improvement increases the dynamic range of the transimpedance amplifier and thereby the operating range of the receiver. A peak detector (22) at the output of an inverting amplifier (11) within the transimpedance amplifier turns on a field effect transistor (FET) circuit (23) when an AC component of an electrical signal becomes so large than the inverting amplifier would otherwise go into saturation whereby the FET circuit (23) acts as an AC shunt impedance at the input of the inverting amplifier and diverts the excess AC current to ground (30). Also, the FET circuit (23) acts as a DC resistance in concert with sense and sink current mirrors (21) and (24) to effectively divert an excessive DC component of the electrical signal away from the input of the inverting amplifier (11). Although the dynamic range of the transimpedance amplifier is increased, the optical sensitivity and the performance of the receiver remain unchanged.

Variable gain control circuit

Abstract: PURPOSE:To make the circuit operation stable with no adjustment, by providing a switch circuit sonstituting with differential pair transistor (TR) to an output side of a differential amplifier so as to change one of control signals to an avalanche photodiode and a varable gain control circuit in response to an output voltage of the amplifier. CONSTITUTION:The variable gain control circuit is provided with the avalanche photodiode APD receiving an optical signal, a variable gain control amplifier AGCA to which the output of the APD is applied and a post-stage amplifier PSA. A feedback circuit comprising a peak detector PD, a comparison amplifer OPA, a switch SW and a control converter DC-DC is connected to the amplifier PSA. The switch SW is provided with DFT1, DFT2 of a differential pair comprising TRs Q5-Q8 and the bases of the TRs Q6-Q7 are connected in common. Further, one of output voltages V2, V3 applied to the converter DC-DC and the amplifier AGCA is changed depending on the relation between an output voltage V1 of the amplifier DPA and a reference voltage Vth and the circuit operation is made stable without any adjustment.

Stabilizing circuit for an inverse rectifier motor control

Abstract: The invention relates to a stabilizing circuit for an inverse rectifier motor control which includes a D.C. voltage supply having a D.C. voltage regulator followed by a smoothing intermediate circuit. A frequency control circuit converts the supply voltage from the intermediate circuit to a frequency control voltage. Following the frequency control circuit is a generator for converting the frequency control voltage to control signals for the inverse rectifier motor control.

Digital control device for an inverse rectifier

Abstract: The invention relates to a digital control device for an inverse rectifier having controllable switching elements for driving an A.C. motor operable at a variable frequency. The device has a pulse generator for producing timing pulses at a multiple of the frequency of the inverse rectifier frequency and a location counter 26 controlled by the timing pulses. A control store in the form of a ROM has at least two storage zones occupied by different controlling tables of which the data characterizes the periodically changing signal pattern for the ignition and extinction signals of the controlled switching elements of the inverse rectifier. A table selecting apparatus which, depending on setting and operating parameters, delivers a preparatory selecting signal for the desired control table and, after a change in this selecting signal, appropriately switches the storage zone over.