Showing papers on "Inverter published in 1972"

Low cost transistorized inverter

Abstract: Low cost circuit for operation of discharge lamps utilizing a rectifier and a two-transistor inverter to provide high-frequency operation of ballasted discharge lamps from a relatively low frequency power source. An air-core feedback transformer is used to provide high frequency operation of the inverter and voltage-shift-initiated feedback is used to prevent "shoot-through" of the two-transistor inverter. Preferably there is, in series with the load, a series resonant combination having a resonant frequency higher than the inverter frequency, in order to minimize switching losses in the transistor inverter.

1972 Advanced Pulsewidth Modulated Inverter Techniques

Abstract: Since its introduction in the mid 1960' s the pulsewidth modulated (PWM) inverter has offered a number of significant advantages over other inverter types for low and medium frequency applications. The generation of an acceptable waveform at higher frequency, however, was limited by the characteristics of available power thyristors and modulator design. With the advent of the fast turn-off thyristor and advances in PWM modulator techniques, the PWM inverter now offers application advantages to 200 Hz. PWM design considerations are analyzed, with a discussion of second-generation PWM operation provided.

Inverter with electronically controlled neutral terminal

Abstract: A solid state inverter, or other single phase or polyphase power converter, has an electronic neutral to enable direct connection to unbalanced loads without requiring a fundamental frequency output transformer. The electronic neutral terminal circuit is typically an additional single phase inverter operated as a current source or sink to maintain the potential at the neutral terminal at a controlled voltage independent of neutral current flow into and out of the neutral terminal. The preferred embodiment is a three-phase pulse width modulated inverter supplying single phase and polyphase unbalanced loads.

Method of testing mosfet planar boards

Abstract: A technique of testing a MOSFET planar board in which each of the chips on the planar board can be electronically isolated for individual testing. In MOSFET technology there are two off chip inverters between the output logic blocks and the pins. These are the preoff chip inverter and the off chip inverter. A NOR gate is formed by adding an additional input line to each of the preoff chip inverters of each of the chips on the board, and the output of each of the chips which are not to be tested are driven to logical ones by application of a positive logical level to this input line while no input is applied to the NOR gates on the outputs of the chip which is to be tested. In this manner, all inputs to the chip to be tested are at a one or high logical level, and for test purposes each input to the chip can be brought to a low logical level or left at a high logical level in accordance with the test pattern to be applied. Its output or reaction to the input test patterns is monitored in the normal manner by the chip tester. Through utilization of this technique, the same test patterns which might number three thousand can be applied to the chip such that even though it remains on the planar board it can be tested equivalent to new. In this manner, each chip can be tested and a defective chip on a planar board isolated without mechanically isolating the chips by breaking chip interconnections.

Field effect transistor detector amplifier cell and circuit for low level light signals

Abstract: A light sensitive element, typically a phototransistor, diode or the like, is suitably coupled to a load element, typically an FET device suitably biased as a linear load. An output circuit including a high input impedance element, typically an FET inverter, is coupled between the linear load and the diode. Little or no current flows in the input circuit in the absence of light applied to the light sensitive element. When light is applied current flows through the light sensitive element and modulates current flow through the inverter. The output circuit has high sensitivity to low level light signals by reason of the linear load and the absence of "Johnson" or thermal noise. A suitable connection between the light sensitive element and the load element sets the output circuit in a threshold state for immediate response to light signals. Connecting the inverter output to suitable circuitry, i.e., amplifiers, differential amplifiers, level shifters and the like, provides an analog or digital output sensitive to extremely low light levels.

Constant duty cycle control of induction cooking inverter

Abstract: In a solid state cool-top cooking appliance for inductively heating a utensil, an inverter for driving the induction heating coil utilizes a constant duty cycle control circuit to optimize performance with the utensil coupled with and removed from the energized coil. To compensate for the increased period of oscillation when unloaded, the inverter operating frequency is automatically decreased to reduce voltage and current stresses on circuit components. Conversely, the operating frequency increases when loaded to couple more power to the utensil. An on-off sensor continuously senses an inverter circuit parameter indicative of the load condition, such as a voltage divider and associated switch for sensing the thyristor anode voltage. The sensed information is processed by the control circuit in closed feedback loop manner to vary the thyristor gating signal repetition rate. Disclosed with regard to a one-thyristor series resonant inverter, the technique is applicable to inverters generally.

Amping voltage on series compensating capacitor series parallel compensated current source inverter with means for cl

Abstract: In a current source inverter including a series compensating capacitor for supplying energy to a tank load and associated control circuit establishing a start up mode and a steady state mode of inverter operation, the former being a transitory mode of operation during which the inverter changes from a non-operating state to steady state operation, circuity is provided for clamping the voltage on the compensating capacitor to a very low magnitude at the end of the start up mode and during the steady state mode.

Ac-dc generating system

Abstract: An induction machine driven as a generator has its output connections coupled to the output connections of a static inverter circuit, connected to operate not as an inverter but as a switching system. A capacitor is coupled to the bus conductors of the switching system. D-c excitation is furnished to the induction generator system only for starting, and is then disconnected. At rated speed the static inverter circuit operates as a switching system to regulate connection of the capacitor to the induction generator on a time-sharing basis, replacing the directly connected capacitor bank in known systems. In multiphase systems the capacitor is not required, as the switching system periodically directs the flow of reactive energy from one phase to another of the inductive machine. By regulating the frequency of the switching operation the overall system can be made to generate effectively over a wide range of input speeds. An a-c output voltage is available from the common terminals between the induction generator and the switching system, and a d-c output voltage is also available from separate conductors of the switching system.

Peripheral circuitry for dynamic mos rams

Abstract: Improved circuits for a dynamic MOS RAM having a storage array of inverting storage cells, including an improved input buffer, an improved write circuit, and a sense circuit. The input buffer circuit includes a dynamic latch circuit clocked by the first clock complement signal and is compatible with TTL logic levels. The cross coupled gate nodes of the dynamic latch are conditionally discharged by circuitry which includes a ratio type first address inverter, and a second ratio type address inverter followed by a third ratioless inverter, whose output conditionally discharges one of the cross coupled gate nodes of the dynamic latch. A separate write circuit drives each digitsense column bus line, and includes a push-pull driver clocked by the third clock input signal. The pull-up and pull-down field effect transistors of the push-pull driver each have an exclusive OR type circuit for conditionally discharging the prepcharged gate electrodes of the pull-up and pull-down field effect transistors, depending on the voltages on the data input signal and the data control signal. The ratioless data control inverter and the data input inverter provide the complement signals required by the two exclusive OR type circuits.

Induction heating equipment having protective arrangements

Abstract: Herein disclosed is an induction heating equipment having a self-exciting chopper type inverter unit having a combination of a silicon controlled or otherwise gate-controlled rectifier and a diode connected in parallel to a d.c. power source for generating heat in a material to be heated through creation of eddy current and hysteresis losses in the material by building up a changing magnetic field induced by a current having suitable frequencies. Protective means are provided in such equipment so that the inverter unit, especially the silicon controlled rectifier of the unit, is protected from incurring a damage when the inverter unit is to be actuated or in the event an unusually increased voltage is produced in the inverter unit during operation. A typical application of the equipment is a cooking equipment using the induction heating process.

Fundamentals of a Pulsewidth Modulated Power Circuit

Abstract: This paper describes the practical design and operating principles of the pulsewidth modulated (PWM) inverter. The use of this power circuit in a variable voltage, variable frequency ac motor drive is emphasized. A comparison with the conventional adjustable voltage input inverter is made with respect to input-output characteristics as well as the effect of the unit on the input supply. This paper demonstrates the ability to design and produce a practical system using state of the arts components.

Instantaneous current control for static inverters

Abstract: An improvement is made to stepped wave static inverters in the form of an instantaneous current control circuit. In case of overload of faults on the inverter output, this circuit acts to limit current in the power switching devices of the inverter. Its performance is an improvement over previous current limit circuits in that it acts instantly to limit overload current and instantly to release that limit so that normal output voltage is restored immediately when the overload is removed. A furtheperformance improvement results because this circuit acts to limit current in the individual power switching devices without necessarily reducing the output voltage of all phases of the inverter.

Circuit arrangement for operating electric arc discharge devices

Abstract: Electric arc discharge device operating apparatus includes rectifier means and an inverter circuit connected to said input terminals and having first and second output terminals. An autotransformer has a main winding across which is connected a capacitor. A drive transformer has a core of linear low loss characteristics, a primary winding and two secondary windings. The primary winding is connected across a portion of the main autotransformer winding between one terminal and an adjacent tap, and each secondary winding is connected to the control terminal of one of the inverter switching devices. The saturation characteristics of the drive transformer are coordinated with the saturation characteristics of the autotransformer so that drive transformer saturation causes switching of the inverter circuit switching devices without saturation of the autotransformer.

Apparatus for limiting instantaneous inverter current

Abstract: The invention relates to a technique for limiting the peak transient currents in the power switches of an inverter wherein a current control circuit compares the current flow in the power switches of the inverter to a reference value and provides protective ON-OFF control of the power switches to prevent overload of the power switches. In the event the current flow through a power switch exceeds a predetermined value, the current control circuit overrides the main power switch ON-OFF control circuit and generates an inhibit signal which turns the power switch off for a period of time required to allow the current magnitude to decrease a predetermined amount at which time the current control circuit inhibit signal is removed and the main power switch ON-OFF control circuit resumes control of the power switch conduction.

Battery protective circuit for emergency lighting systems

Abstract: This invention provides improved circuitry for holding an inverter of an emergency lighting system in an off condition until a normal power source falls below a predetermined voltage level and circuitry to protect a battery from deep discharges when it is called upon to deliver auxiliary power to a lighting system via said inverter. The protective circuitry includes the short circuiting of one of a plurality of windings of a transformer of the inverter upon the battery voltage falling below a predetermined level. The shorting of one winding causes the inverter, which includes other windings of the transformer, to cease oscillation, and therefore substantially cease to draw power from the battery. The battery can thereby recover in substantially unloaded condition, prolonging its useful life. Means are provided for allowing the battery to repower the inverter when the battery has recovered sufficiently. This results in a cyclical operation of the emergency lighting system causing the lights to flash as the battery recovers and discharges. This recovery and discharge cycle prolongs the operating time of the lighting system when under emergency power and prolongs the life of the battery.

Several Modulation Techniques for a Pulsewidth Modulated Inverter

Abstract: Pulsewidth modulation of a six-step inverter can be accomplished in different ways. Comparisons between different modulation techniques are based primarily on harmonic content in the output waveform and circuit constraints imposed by semiconductor characteristics. Adaptive ratio is a modulation scheme which combines the beneficial features of several available techniques and makes the necessary compromises to optimize the operating characteristics of a modulated six-step inverter.

Field effect transistor detector amplifier cell and circuit providing a digital output and/or independent of background

Abstract: A light sensitive element, typically a photo-transistor, diode or the like, is suitably coupled to a load element, typically an FET device suitably biased as a linear load An output circuit including a high input impedance element, typically an FET inverter, is coupled between the linear load and the diode Little or no current flows in the input circuit in the absence of light applied to the light sensitive element When light is applied current flows through the light sensitive element and modulates current flow through the inverter The output circuit has high sensitivity to low level light signals by reason of the linear load and the absence of ''''Johnson'''' or thermal noise A suitable connection between the light sensitive element and the load element sets the output circuit in a threshold state for immediate response to light signals Connecting the inverter output to suitable circuitry, ie, amplifiers, differential amplifiers, level shifters and the like, provides an analog or digital output sensitive to extremely low light levels

Automatic switching and short circuit protection circuit

Abstract: A circuit for use with standby power systems requiring automatic starting. One portion of the circuit is for use with silicon controlled rectifier (SCR) inverters and another portion is more general in nature, for use with loads requiring high initial starting current, or presenting short circuits. The circuit provides for recycling and restart in the event of commutation failure in the SCR inverter and recycles automatically and remotely. Commercial power failure produces switching which places a DC power source on a trigger circuit and a switching sequence circuit. The switching sequence circuit provides a low impedance connection from the DC power source to the SCR inverter only in the event that proper commutation occurs and no internal SCR inverter faults are present. Inverter output is directed to a load through an instantaneously acting surge and short circuit protection circuit which automatically removes the load from the output of the inverter in the event a load short circuit occurs and also limits high surge current requirements on the inverter by the load which might otherwise cause commutation failure in the SCR inverter. The surge and short circuit detection circuit automatically connects the load back to the inverter output after a predetermined period of time once having made a disconnection. The circuit ensures proper functioning of the SCR inverter in spite of temporary internal inverter or external load faults by recycling the inverter start until proper commutation occurs and by recycling the load connection until normal load conditions exist.

Inverter circuit and switching means

Abstract: An inverter suitable for use as a fluorescent light ballast is disclosed. The inverter has a constant output regardless of load. Good efficiency at high frequency is provided by minimizing the transistor switching losses by means of a resonant storage means and a unique feedback and magnetic structure.

Induction heating coil arrangement in induction heating equipment

Abstract: Herein disclosed is an inverter device for use in an induction heating equipment in which an oscillating current having a suitable frequency is fed to an induction heating coil which is placed in proximity to a material to be heated, whereby eddy current and hysteresis loses are invited in the material to be heated so that heat is generated in the material. The inverter device features provision of noise preventive means, adapted to dampen out the high-frequency field built up by the component elements of the inverter circuit, leak current preventing means adapted to prevent leakage of current from the material to be heated to ground, and a variable inductor arrangement adapted to vary the apparent inductance of the induction heating coil. A typical application of the inverter device is an induction heating cooking equipment.

Three-phase inverter control circuit

Abstract: A three-stage shift register circuit, responsive to the output signals of a variable frequency oscillator, produces a repeating series of six equally spaced electrical timing signals A differentiating circuit corresponding to each electrical timing signal is responsive to the leading edge of each corresponding electrical timing signal to produce a corresponding gate signal pulse Each gate signal pulse is amplified by a corresponding amplifier, the output of which is connected across the primary winding of a pulse transformer having three secondary windings, a respective secondary winding of each pulse transformer is connected across the gate-cathode electrodes of each the extinguishing silicon controlled rectifier of a three-phase inverter circuit through which a three-phase motor may be energized from a direct current supply potential source which corresponds to the inverter silicon controlled rectifier to be extinguished, the inverter silicon controlled rectifier next to be triggered conductive and the inverter silicon controlled rectifier last triggered conductive

Micro-miniature high efficiency power supply

Abstract: A micro-miniaturized high efficiency power supply utilizing the principle of open loop voltage regulation. The circuit employs full-wave rectification at the input followed by filtering, preregulation, inverter isolation and final saturated series regulation with noise suppression and energy storage filters at appropriate strategic places. A hold up circuit initially supplies power to control circuitry. When a pre-regulator attains a predetermined value the hold up circuit is turned off and a pre-regulator then supplies power to the control circuitry.

Radiation-Hardened Complementary MOS Using SiO2 Gate Insulators

Abstract: This paper reports the results of a study in which commercially-proven metal-oxide-semiconductor (MOS) processes are modified to provide radiation-hardened complementary MOS (CMOS) circuits. Typical silicon-dioxide (SiO2) gateinsulator processes are used, in conjunction with chromium doping, to fabricate hardened MOS capacitors, n and p channel transistors, and CMOS inverter circuits. The resulting CMOS circuits exhibit excellent electrical and performance characteristics and stability, while accumulating more than 107 rads(Si) ionizing-radiation dose, under worst-case conditions. Observable radiation effects are essentially independent of static bias and are minimum under normal, dynamic operating conditions. The approach is not only compatible with commercial SiO2 processes but appears adaptable to dielectric-isolation, such as silicon-on-sapphire (SOS). Hence, the demonstrated technology represents a "breakthrough" in the development of cost-effective, stable CMOS devices for use in advanced military systems.

Starting circuitry for series/parallel compensated, current-fed inverter

Abstract: In a thyristor-composed, current-source, inverter including a series compensating capacitor for supplying energy to a tank load, means are provided for starting the inverter from a nonoperating state. To that end the compensating capacitor is charged by direct current flowing through a path formed by the conduction of certain inverter thyristors and at the first time after the commencement of such conduction certain other thyristors are rendered conductive to enable the magnitude of the direct current to build up. At a second time after the commencement of conduction of said other thyristors, alternate triggering of the inverter thyristors is commenced and alternating current flows through the load. The voltage on the compensating capacitor commutates inverter current until the load is charged sufficiently to commutate current on its own.

Inverter with controlled rectifiers and a regulable direct voltage supply

Abstract: An inverter arrangement including controlled rectifiers, the inverter being supplied by a regulatable direct voltage supply which includes an on-off switchable element and a filter. A control circuit connected to the output of the supply generates and directs first control pulses to the switchable element, and a pulse generator also connected to the output of the supply generates and directs second control pulses to control the rectifiers in the inverter. The control circuit includes a step regulator having an amplifier, a feedback path and apparatus for producing an oscillation, the step regulator having the effect of altering both the frequency and the width of the first control pulses when the voltage at the output of the supply changes.

Driving circuit for liquid crystal displays

Abstract: A driving circuit for liquid crystal displays is disclosed. The circuit comprises a single field effect transistor which operates in two different modes to drive the display. The field effect transistor (FET) is connected between a high voltage inverter and the display while a second high voltage inverter is also connected to the display. When input signals are fed to the FET, it acts as an inverter in one direction and as a source follower in the other direction driving the liquid crystal display with AC voltage.

Method of controlling a pulse inverter for an induction machine

Abstract: A method controls a pulse inverter for controlling the speed of induction machines such as asynchronous machines. To provide the control signals for the inverter, the point of intersection of a periodic reference curve whose frequency corresponds to the desired fundamental oscillation frequency of the output voltage of the inverter is provided with a determinable number (l to n) of DC voltage levels (al to an). The DC voltage level positions are controllable according to a desired rule or principle in dependence on a control voltage (USt) whose level depends on the desired amplitude of the fundamental oscillation.

Driver circuit using diodes to control the minority carrier storage effect in switched transistors

Abstract: An improved driver circuit for a pair of switching transistors in a DC-DC converter or a DC-AC inverter is shown. The illustrated circuit includes a switchable constant current source coupled through a transformer and semiconductor diodes to the switching transistors. The diodes are arranged so that, as long as minority carrier current flows in either one of the switching transistors, the other is prevented from responding to a switching signal from the constant current source.

Linear motor propelled air cushion vehicle

Abstract: 1280148 Control of motors TRACKED HOVERCRAFT Ltd 9 Oct 1969 [16 Oct 1968] 49017/68 Heading H2J A track-guided hovercraft is driven by a linear induction motor 15 whose double-sided stator straddles a reaction rail, air being supplied to cushion devices on the vehicle by fans which are driven by D.C. motors 9. Themotor 15 is supplied through an inverter 20. If the track power supply fails when the vehicle is at speed, the fan motors 9 continue to turn due to inertia and the regenerated voltage therefrom is maintained by unit 43 at an appropriate value to provide, through storage capacitors 31, the initial reactive volt-amperes for the linear motor which regenerates A.C. under the vehicle momentum. This A.C. is rectified by diodes 28, 29, to restore the power supply to the fan motors which provide lift and guidance pressure during the braking period. A floating battery 40 excites the fan motors when the main power supply fails. A firing circuit for thyristors 26, 27, comprises controller 50 which automatically adjusts the inverter relative to vehicle speed to obtain the desired braking thrust. In another arrangement, the storage capacitors 31 are sufficiently charged at the moment of failure whereby the inverter 20 itself provides the reactive volt amperes for the linear motor to begin to regenerate A.C.