Showing papers on "Negative impedance converter published in 1980"

Switching regulated pulse width modulated push-pull converter

Abstract: A switching regulated push pull converter which includes voltage and current feedback loops to provide a highly regulated output voltage throughout a 100 percent load range. This circuit also provides a semi-regulated auxiliary output voltage which can be loaded beyond 100 percent of its load range with no minimum load requirement on the highly regulated output voltage. A direct current drive circuit for the push-pull power switches provides a transformerless proportional drive and means are provided to compensate for transformer asymmetry.

Solid-state voltage reference providing a regulated voltage having a high magnitude

Abstract: A two transistor voltage reference circuit controls the ratio of the current densities of two transistors by a negative feedback loop. A voltage corresponding to the difference in the base-to-emitter voltages of the two transistors is developed which has a positive temperature coefficient (TC) and which is connected in series with the base-to-emitter voltage of one of the two transistors having a negative TC. The circuit parameters are selected so that the resultant combined voltage has a predetermined, composite TC. A zener diode is included in the negative feedback loop and arranged to have a TC which cancels the predetermined composite TC to develop a reference voltage having a high magnitude that has minimal variation with temperature change.

MOS Comparator circuit

Abstract: A circuit for detecting a difference in the relative magnitudes of two voltages includes a current sensing circuit connected between the first voltage and ground to thereby cause a first current to flow in the current sensing circuit, an amplifier connected between the second voltage and ground and connected to the current sensing circuit to thereby cause a second current to flow, the second current being equal to the first current when the first voltage is equal to the second voltage, and a variable impedance inverter connected to the first voltage and connected to the amplifier, the variable impedance being controlled by the first voltage, the output of the inverter thereby being related to the difference between the first voltage and the second voltage. The invention is particularly useful for controlling a battery backup power supply in a microprocessor having a volatile memory and for creating precision delay circuits.

Arrangement for the generation of a signal in proportion to a capacity

Abstract: An active measuring converter for connection between a two-wire line and an impedance to be measured, wherein an oscillator supplies alternating voltage to the impedance, and the variation in current drawn by the oscillator is in accordance with the value of the impedance. The measurement signal is transmitted together with the power for the active measuring converter via a two-wire line. The oscillator supplies the impedance with stabilized AC voltage independent of its operating current. Electronic switching devices coupled to the impedance either add the alternating current to the measuring signal as an impressed current, or couple it to a resistor-capacitor network for establishing a reference input for the controlled variable voltage. The alternate coupling of the alternating current corresponds to the alternating polarity of the AC current flowing through the impedance. The impedance may be the capacitance of a sonde which varies according to filling level. The converter draws a minimum of current and may be adjusted for any given measurement conditions.

Line hold circuits

Abstract: OF THE DISCLOSURE A single line hold circuit adapted for connection between the tip and ring leads of a telephone line. The circuit comprises variable impedance devices for connection between the tip and ring leads, the impedance devices including a semiconductor element having high and low impedance states, the impedance of the low impedance state being sufficiently small to maintain the telephone line in a hold condition. The circuit further causes the semiconductor to be in its low impedance state following an interruption of a predetermined length of time in loop current. A double line hold circuit is also illustrated.

Negative feedback amplifying circuit having voltage negative feedback and current negative feedback circuits

Abstract: A negative feedback amplifying circuit comprises an amplifier connected to a load, a voltage negative feedback circuit which negatively feeds back the output voltage of the amplifier to the input side of the amplifier maintaining a frequency selection characteristic, and a current negative feedback circuit which negatively feeds back a current signal obtained by detecting the current flowing through the load to the input side of the amplifier maintaining a frequency selection characteristic. The voltage negative feedback circuit has a frequency selection characteristic comprising a dip at a specific frequency f 0 . On the other hand, the current negative feedback circuit has a frequency characteristic comprising a peak at a specific frequency f 0 .

Power source with an electronic impedance changer

Abstract: A circuit arrangement to provide a fixed voltage source in series with an arbitrarily chosen impedance of any magnitude and phase shift having very low power dissipation and capable of being fabricated on silicon integrated chips is disclosed. The circuit arrangement includes a sensing resistor to sense the output current of a power converter which is amplified and fed back with an appropriate phase shift to control the output voltage of the converter. An independent control signal may be combined with the fed back voltage to change the chosen impedance to another type of impedance.

Input optimized FET bias circuit

Abstract: A field effect transistor bias circuit is presented which exhibits a low impedance for small signals and a high impedance for large signals. This circuit uses an operational amplifier to provide a temperature compensated low impedance voltage source for the gate bias which is optimal for small signal operation. In the presence of a large signal, the gate begins to draw current. This causes the operational amplifier to saturate and transforms the bias circuit into a high impedance source, which is optimal for large signal operation.

Impedance generator circuit

Abstract: An improved impedance generator circuit, for use with two-wire transmission systems of the type encountered in telephony, is adapted to be interfaced with the wires and operates in a manner to effectively generate a desired positive or negative impedance across the wires. The impedance generator includes a current source, and generates a positive impedance by drawing from the wires all of the current that would otherwise be required by the positive impedance, or a negative impedance by providing on the wires all of the current that would otherwise be provided by the negative impedance, in response to a metallic voltage applied across the wires by a signal source. At the same time, the impedance generator provides common mode rejection to longitudinal voltages on the wires.

D.C. to d.c. converter with plural feedback loops

Abstract: A d.c. to d.c. converter which produces from a low voltage battery supply a high voltage d.c. output. The converter comprises a step up transformer the primary of which receives current pulses under the control of an oscillator. For each current pulse, the current builds up steadily and is then abruptly cut off so as to induce a high voltage pulse in a secondary of the transformer. The high voltage pulses pass along a voltage multiplier to provide the high voltage d.c. output. Each high voltage pulse has associated with it a low voltage pulse in the primary which is used to control the rate of the oscillator. The oscillator is also controlled as a function of the peak current in the primary by a transistor, and the oscillator is further controlled to limit its maximum rate when the output current exceeds a given level, by means of a feedback loop.

Constant-voltage generator for integrated circuits

Abstract: A constant voltage generator includes means for compensating for deviations of its output voltage that are due to variations in the supply voltage or changes in ambient temperature. The generator features a negative feedback resistor connected in the emitter circuit of a transistor between whose emitter and collector branches said output voltage appears. A current flows through this resistor which is supplied by another transistor whose current varies as a function of supply voltage variations. The generator may be used for supplying bias voltages to logic circuits.

Overload protection for a voltage conversion circuit

Abstract: A voltage converter of the transformer type which incorporates at least one switching transistor coupled to control the application of current to the transformer primary and circuitry for switching the transistor on and off to control the current through the primary winding. When the output of the converter is shorted, the switching rate undesirably increases causing potential damage to the converter. A frequency detecting circuit detects the increase in switching frequency and acts to reduce the input voltage to the converter to prevent damage thereto.

Variable impedance circuit

Abstract: The variable impedance circuit comprising the invention provides a circuit having an impedance which varies in response to an input signal. The invention utilizes a control circuit which samples the load current and compares it to the demand signal to generate a control signal. The control signal is coupled to a load driver circuit to cause the required current to flow through this circuit. The load driver circuit and one or more substantially identical load circuits are series coupled to form a variable impedance circuit having the desired voltage and current capability.

Precision negative impedance circuit with calibration

Abstract: A negative impedance circuit comprising a level shifter and a current mirror, includes calibration circuitry for adjusting the negative impedance to provide the precise amount of current required to compensate for current drain caused by a known impedance at varying voltage levels. A divider/multiplier circuit is connected to the line which has the known impedance and provides a signal which is directly proportional to the voltage level on the line to the level shifter which, in turn, provides a corresponding control current to the current mirror. The current mirror provides a proportional current to the line current supplied by the current mirror and may be measured at a calibration resistor and the divider multiplier circuit may be adjusted to the appropriate ratio until the exact amount of current required to offset the drain to the precision resistor is provided by the current mirror.

Voltage converter for use with solar cells - whose oscillation frequency is regulated by available solar radiation with period of current flow phase determined by timing circuit

Abstract: The circuit is intended to match the load impedance on the solar cell, or other low voltage output energy converter, such as a thermocouple, to the available output energy. The converter works on the principle of a blocking oscillator under the control of a monostable flip flop (7). The frequency of the monostable is set by the state of a photo-sensitive resister (8) which receives the same irradiation as the solar cell (4). The monostable operates a switch, typically a field effect transistor (2), which alternately blocks and re-leases the flow of energy from an inductor (1) to a load, for example an accumulator (5). Increasing irradiation increases the time constant of the monostable which has the effect of decreasing the load impedance connected to the solar cell. During the current flow phase the input voltage generates a magnetic field, whose energy is passed to the load during the blocking phase.

Electronic control and regulating system

Abstract: An electronic control and regulating system for AC-operated appliances, especially universal motors and with symmetrical phase control. The control circuit includes among other things an inductive current-voltage converter 9, the primary side 8 of which is connected to the load current circuit and in which, in addition to the converter function, the inductivity of the secondary winding 10 is used and becomes a component of a resonant circuit 20 which is tuned approximately to the frequency of the AC voltage source. The feedback variable of the control system is formed by the resonant circuit voltage, i.e. the resonant circuit impedance, which depends not only on the magnitude of the load current but also on the phase angle of the load current. This quasi-resonance effect makes possible a direct influence of the trigger circuit which consists customarily of a trigger capacitor 13, a load resistor 11 and a trigger diode 15 and is possible without excessive use of additional circuit elements.

Power supplying apparatus

Abstract: This invention concerns to a power supply arrangement which comprises, substantially, a power source circuit, a voltage converter circuit for converting a direct current voltage from the direct current power source circuit into an alternating current voltage, and a rectifier circuit for rectifying the alternating current voltage to a high direct current voltage to be applied to a load. The voltage converter circuit includes an oscillating transformer and an oscillation switching element. The oscillating transformer is provided with only two windings, and these windings are effectively employed to activate the voltage converter circuit.

Voltage compensation for an A-C network supplying a rapidly-changing load

Abstract: A circuit for controlling the voltage of a network which supplies electrical power to a load having a rapidly varying impedance. The circuit contains a pair of controlled electric valves which are connected in parallel between two conductors of the network and poled for condition in opposite directions. A voltage transformer produces a signal corresponding to the network voltage, which signal is conducted to an integrator and subsequently compared to a preset mean value. The preset mean value corresponds to a desired amplitude at which the positive and negative half-wave cycles of the network voltage are desired to be maintained. In one embodiment, the controlled electric valves are caused to conduct current during respective half-waves of network voltage so as to maintain the amplitudes of the half-waves at the present mean value. Other features are described for compensating for long term drift of the network voltage and for controlling the controlled electric valves by means of logic circuitry.

Hybrid integrated impedance converter circuit

Abstract: A hybrid integrated impedance converter circuit comprising a frequency dependent negative resistance circuit, in which two operational amplifiers are included Each of the two operational amplifiers has an output terminal and an inverting input terminal, with a negative feedback capacitor being connected between these terminals The negative feedback capacitor is formed by a stray capacitance which arises between conductors connected to the output and inverting input terminals, which conductors are placed in close proximity to each other

Battery type scale

Abstract: PURPOSE:To reduce the power consumption of each circuit and to prolong the life of batteries by providing a timer which operates on the start of the application of a power voltage and the start of metering operation, and by stopping feeding to each circuit when a metering state is held. CONSTITUTION:The voltage of a battery 1 is made constant by a constant voltage circuit 3 and the constant voltage is applied to a load cell 17, an A/D converter 20 and a display device 22; and a voltage signal outputted from the cell 17 corresponding to a load is converted by the converter 20 into a digital value, which is further converted 25 into a weight value to display it on the display device 22. In a processor 25, a timer is provided, and this timer is started in response to the start of the application of the battery voltage and reset and restarted in response to the start of metering operation. Then, the supply of the battery voltage to the circuit 3, cell 17, converter 20, and display device 22 is stopped a certain time after the time is started.

Switched mode regulated DC to DC converter

Abstract: A switched mode regulated DC to DC converter for supplying a regulated voltage to a load includes a switching frequency generator of a switching cycle having positive and negative portions. A device, responsive to the outputs of the switching frequency generator, accumulates a voltage during the positive and negative portions of the switching cycle. The demand for voltage by a load is sensed and circuitry generates a first and second trigger otuput during the respective positive and negative portion of the switching cycle when the accumulated voltage equals the sensed load voltage demand, the time required to generate the second trigger output being equal to the time required to generate the first trigger output. A transformer apparatus, responsive to the first and second generated trigger outputs, generates currents of positive and negative polarity during the positive and negative portions of the switching cycle. A first electronic switch, responsive to the generated currents of positive polarity, connects a load voltage source to a load during the positive portion of the switching cycle. Similarly, a second electronic switch, responsive to the generated currents of positive polarity, connects the load voltage source to the load during the negative portion of the switching cycle.

Signal converter circuit

Abstract: PURPOSE:To reduce asymmetrical distortion by forming a negative feedback path, for example, when a single end signal is converted into a differential signal by the use of a current mirror. CONSTITUTION:Diode D1 is connected to the current path of transistor Q2 and fed back to Q3 and diode D2 of bias circuit 2 via feedback path l. At half the positive cycle of input signal current (i) to terminal 3, positive current (i1') which is (DELTAi) greater than the peak value of negative current (i1) flowing to Q1 flows to Q2 and another equation is satisfied. On the other hand, current (i1'') of Q3 becomes equal to 1/2 i1' and also equal to 1/3i+1/2DELTAi. Since (i) equals to (i1)+(i1''), the current flowing to Q1 through the action of the feedback loop decreases and the decrement of the voltage between the base and emitter of Q1 also decreases. The increment of the voltage between the base and emitter of Q2, therefore, decreases and (DELTAi) is reduced. As a result, currents i1 and i1' of Q1 and Q2 are controlled to be equal, thereby making it possible to obtain signals Sa and Sb with a little asymmetrical distortion.

Device for controlling the voltage between two conductors of an a.c. supply mains for a rapidly changing load

Abstract: Between the conductors an AC plate 7 is arranged, the valve controller includes a voltage converter 11 with, preferably downstream function generator 12, an integrator 13 and at least one threshold detector 16, 18th The limit indicator is the integrator output voltage and a target value M for the voltage-time area of ​​the positive switched (with respect to the Durchlasrichrung of the associated valve) voltage half-oscillation or the integral of the function generator output size. As soon as the voltage-time area formed by means of the integrator exceeds the set value, the voltage is by ignition of lying in the forward valve shorted (FIG. 1).

Energy saving DC-DC converter circuit

Abstract: An energy saving DC-DC converter circuit is disclosed having two energy efficient means which operate in tandem, an energy conserving means (30, 8, 1) and a voltage doubling means (26). These energy efficient means are applied in combination with elements commonly found in DC-DC converter circuits, namely an AC voltage generator (2), a transformer (3) for stepping up the generated AC voltage, and means (31) for storing the converted DC voltage. The energy conserving means is connected to the DC voltage storage means (31). It comprises a resettable inhibit circuit (1) which cuts off the provision of DC voltage for conversion for a predetermined interval when the output of the converter exceeds a predetermined level. The voltage doubling means is reponsive to outputs of the inhibit circuit (1) of the energy conserving means and the AC voltage generator (2). It provides a phase inverted waveform of the generated AC voltage on one of two leads to the AC voltage step-up transformer (3).

Rectifier system earth fault protection circuit - has parallel amplifiers for negative and positive lines supplying rectifier connected to relay

Abstract: The protection circuit for a rectifier system with a converter but without a separating transformer for the power supply system with earthed protective conductors has shunt connections in the positive and negative lines at the output of the converter. These are connected to two parallel d.c. separating amplifiers with voltage dividers at their outputs. The dividers are connected across a rectifier bridge followed by a d.c. relay. A d.c. voltage proportional to a fall in voltage at the converter output is thus applied to the relay, being amplified by the separating amplifiers. The polarity of the output voltage shows whether an earthing fault occurs in either the positive or negative line at the converter output.

Apparatus and method for use in a power supply connected to a load

Abstract: A high-voltage crowbar circuit (16, 18, 20) continually senses the load impedance and crowbars the output voltage (36) applied to a load if the load impedance falls below a selected value. A differentiator circuit (92) at the load (BR) senses variations in load voltage (36) and can trigger the crowbar operation if the voltage variation as a function of time exceeds a preselected value.

Voltage tester with alternating to direct voltage changeover - contains battery-powered circuit including integrated circuit and diodes

Abstract: The two-pole voltage tester has a digital voltage level indicator, has an additional polarity display for direct voltages and an automatic switch over and indicator for when an alternating voltage is detected. A circuit contg. integrated circuit components, transistors, and passive components is contained in one of the two test probes. The circuit identifies the voltage type and controls the display accordingly without the use of mechanical switching elements. It is a small conveniently handleable device. Faulty operation is excluded despite the use of electronic switching. The measured voltage is rectified and fed to an analogue-to-digital converter consisting of an integrated circuit also detecting the voltage polarity. The polarity indicator is driven by a circuit section which also corrects the converter sensitivity.

A D.C. to D.C. converter

Abstract: A d.c. to d.c. converter which produces from a low voltage battery supply a high voltage d.c. output. The converter comprises a step up transformer the primary (Lp) of which receives current pulses under the control of an oscillator (5). For each current pulse, the current builds up steadily and is then abruptly cut off so as to induce a high voltage pulse in a secondary (L s ) of the transformer. The high voltage pulses pass along a voltage multiplier (6) to provide the high voltage d.c. output. Each high voltage pulse has associated with it a low voltage pulse in the primary (Lp) which is used to control the rate of the oscillator (5). The oscillator (5) is also controlled as a function of the peak current in the primary (Lp) by a transistor TR3, and the oscillator is further controlled to limit its maximum rate when the output current exceeds a given level, by means of a feedback loop (R3, C4, R4, IC4, TR3).

Restore circuit for a semiconductor storage

Abstract: Disclosed is a restore circuit for restoring an integrated semiconductor storage array having storage cells consisting of bipolar transistors. The restore circuit includes a reference voltage generator, an impedance converter, and switches to connect the reference voltage generator and the impedance converter to the storage array. The reference voltage generating circuit includes a current source and at least one reference storage cell identical in construction to the storage cells of the array. The reference voltage generating circuit provides a reference voltage to the impedance converter which supplies a second reference voltage to the array at a greatly reduced impedance. The equivalent circuit of the storage cells is that of a capacitor in parallel with a diode. Thus, the impedance converter provides an initial surge of capacitive current which restores the cells, followed by a standby current which is a function of the diode characteristics of the cell equivalent circuit.