Showing papers on "Inductor published in 1987"

Exact analysis of class E tuned power amplifier at any Q and switch duty cycle

Abstract: Previous analytical descriptions of a Class E high-efficiency switching-mode tuned power amplifier have been based on the assumption of an infinite Q or the minimum possible value of Q . This paper presents an exact analysis of the Class E amplifier at any Q and any switch duty cycle D , along with experimental results. The basic equations governing the amplifier operation are derived analytically using Laplace-transform techniques and assuming a constant current through the dc-fed choke. The following performance parameters are determined for optimum operation: the current and voltage waveforms, the peak collector current and collector-emitter voltage, the output power, the power-output capability, the load-network component values, and the spectrum of the output voltage. It is shown that all parameters of the amplifier are functions of Q . Therefore, the high- Q assumption used in previous analyses leads to considerable errors. For example, for Q at D = 0.5 , some errors are up to 60 percent. The results can be used for designing Class E stages at any Q and switch duty cycle D . The measured performance shows excellent agreement with the design calculations. The collector efficiency was over 96 percent at 2 MHz for all tested values of Q from 0.1 to 10.

Linear power control for ultrasonic probe with tuned reactance

Abstract: There is disclosed herein a driver system for an ultrasonic probe for allowing a user to have proportional control of the power dissipated in the probe in accordance with the position of power dissipation controls operable by the user and for automatically tuning upon user request such that the driving frequency is equal to the mechanical resonant frequency of said probe and such that the reactive component of the load impedance represented by said probe is tuned out. The system uses a tunable inductor in series with the piezoelectric crystal excitation transducer in the probe which has a flux modulation coil. The bias current through this flux modulation coil is controlled by the system. It is controlled such that the inductance of the tunable inductor cancels out the capacitive reactance of the load impedance presented by the probe when the probe is being driven by a driving signal which matches the mechanical resonance frequency of the probe. The resulting overall load impedance is substantially purely resistive. The system measures the phase angle and monitors the load current. This information is used to determine the mechanical resonance frequency by sweeping through a band of driving frequencies and finding the peak load current where the slope of the load current versus frequency function is greater than a predetermined constant. After the automatic tuning to the resonant frequency, the system automatically adjusts the bias current flowing through the flux modulation coil to maintain the substantially purely resistive load impedance for changing power levels. There is also disclosed herein an analog circuit to measure the Phase angle for the load driving signal and to adjust the frequency of the driving signal for best performance. This system includes an integrator to eliminate the effect of offset errors caused by operational amplifiers.

Quasi-Resonant Converters-Topologies and Characteristics

Abstract: In designing switching dc-dc converters, the effort to increase operating frequency to reduce weight, size, and cost of magnetic and filter elements is constantly hampered by higher switching stresses and switching losses. To overcome these obstacles, the concept of the "resonant switch" is proposed. By incorporating additional inductor and capacitor elements to shape the semiconductor switch's current waveform, a "zero-current switching" property can be realized. Based on the resonant switch technique, a new host of quasi-resonant converter circuits have been derived, which can be operated in the megahertz range.

Inductive power coupling with constant voltage output

Abstract: A constant voltage inductive power coupling for magnetically transferring electrical power from a power source through an air gap to a load comprising a first electromagnetic inductor connected to a power source to generate a shaped alternating magnetic field, a said inductor with a saturable core separated by an air gap from the first inductor and magnetically coupled thereto to receive the shaped magnetic field, the core being responsive to the field to enter a state of magnetic saturation. A coil is electromagnetically coupled to the saturable core and has output leads connected to the load. A capacitor is in electrical communication with the coil to form a tuned circuit that is below resonance at the coupling operating frequency. The magnetic field induced by the first inductor to the second inductor causes voltage in the coil, whose magnitude is determined by the amount of magnetic flux in the core. The saturable core is responsive to any change in input voltage to magnetically counteract such change so as to maintain the core in its state of saturation thereby tending to keep the output voltage constant. Also any increase in load current is associated with a closer approach of the tuned circuit to a resonant condition tending to maintain the output voltage at a constant level. The invention is particularly useful in battery charging circuits or for other applications where the voltage required must be kept at a constant level.

Temperature responsive transmitter

Abstract: A temperature responsive transmitter is provided in which frequency varies linearly with temperature. The transmitter includes two identically biased transistors connected in parallel. A capacitor, which reflects into the common bases to generate negative resistance effectively in parallel with the capacitor, is connected to the common emitters. A crystal is effectively in parallel with the capacitor and the negative resistance. Oscillations occur if the magnitude of the absolute value of the negative resistance is less than the positive resistive impedance of the capacitor and the inductance of the crystal. The crystal has a large linear temperature coefficient and a resonant frequency which is substantially less than the gain-bandwidth product of the transistors to ensure that the crystal primarily determines the frequency of oscillation. A high-Q tank circuit having an inductor and a capacitor is connected to the common collectors to increase the collector current flow which in turn enhances the radiation of the oscillator frequency by the inductor.

Digitally controlled A.C. to D.C. power conditioner

Abstract: An A.C. to D.C. power conditioner, which draws sinusoidal input current utilizes digital proportional-integral control to provide output voltage regulation by adjusting the gain of a current program loop. The current program loop controls the state of a power switch to force the instantaneous average current in an inductor to follow the instantaneous rectified line voltage. Variable hysteresis control provides noise immunity by increasing the ripple current in an iron-cored filter inductor when the instantaneous input voltage is high. Digital proportional-integral (PI) control provides output voltage regulation by adjusting, in discrete steps, the gain of the current program loop. A multiplying digital-to-analog converter serves as an interface between the voltage regulation loop and the current program loop. The sampling rate of the PI controller is determined by the input line frequency, which allows good transient response to be obtained. The current program loop forces the current drawn by the power conditioner to follow the input A.C. line voltage, thereby electronically emulating a resistor.

Inductor current control circuit

Abstract: A DC to DC power converter having reduced switching loss for operation at high frequencies. As disclosed, a buck, or forward, converter includes a first FET as the switching device in series with an inductor and a second FET as the flywheel device. At the common node to which the two FET's and the inductor are connected, there is sufficient capacitance that the FET's may be turned off without appreciable voltage change across the FET's. The value of the inductor is chosen, with respect to the input and output voltages and frequencies of operation involved, to insure that the inductor current polarity reverses each cycle, raising the node voltage to the level of the input voltage, substantially eliminating turn-on losses of the first FET. Control circuitry is provided for regulation of the power converter to control the peak-to-peak current in the inductor and to insure that at least a selected minimum value of the inductor current is present for each cycle of operation of the converter. An over-voltage protection circuit for the output of the converter is also provided.

Apparatus for converting DC to DC having non-feed back variable hysteretic current-mode control for maintaining approximately constant frequency

Abstract: An hysteretic current-mode controlled DC to DC converter has an input voltage, an output voltage and a control switch. The switch alternately coupled the input voltage into an energy storage inductor. It is controlled by an hysteretic conparater sensing the current of the inductor and having turn-on and turn-off limits. The limits are symmetrical about an average inductor current. The limits are adjusted by simple non-closed-loop methods to maintain an approximately constant frequency of oscillation. The average inductor current is controlled by an error amplifier to maintain a constant output voltage. The two controls are independent.

A comparison of resonant topologies in high voltage DC applications

Abstract: Because of their tolerance of transformer non-idealities, resonant converters appear well-suited to high voltage applications. In this paper, the series and parallel resonant topologies, as well as a newly discovered hybrid resonant topology are compared for high voltage applications. Design criteria which incorporate transformer nonidealities are deloped, and are employed in the construction of high voltage prototypes for each topology. It is found that the parallel topology leads to the lowest peak switch current and the most ideal behavior.

A novel miniature planar inductor

Abstract: The conventional inductor consists of cores and wound wires, which are obstacles for the integration with other devices. The planar inductor, which has planar coils and magnetic layers in place of cores and wires, is fabricated on a substrate. Therefore it can be integrated with other devices, and it will be a fundamental element for the future magnetic IC. In this paper two kinds of planar inductors are described. One is the outer type, which has the larger inductance than any other planar inductor. The other is the inner type, which has the possibility for a variable inductor.

Switching regulator with rapid transient response

Abstract: A switch-mode power supply includes the series combination of an inductor and a controllable switch adapted to be coupled to a voltage source for producing a succession of increasing and decreasing ramp currents through the inductor. The average value of the ramp currents is controlled by a feedback loop. A second controllable switch arrangement is coupled for causing the current leaving the inductor to recirculate through the inductor during those intervals in which the second switch is conductive. An integrator is coupled to the inductor for integrating ramp current from the inductor during those intervals in which the second switch is nonconductive, for generating load voltage. A second feedback arrangement senses the load voltage and controls the average conduction of the second switch to control the load voltage. In one embodiment, an inverter receives ramp current from the inductor and generates alternating current, which are transformed and rectified before application to the integrator.

Scheme for rapid adjustment of network impedance.

Abstract: A static controlled reactance device (10) is inserted in series with an AC electric power transmission line (6, 8) to adjust its transfer impedance. An inductor (X, 20)(reactor) is serially connected with two back-to-back connected thyristors (24, 26) which control the conduction period and hence the effective reactance of the inductor (21). Additional reactive elements are provided in parallel with the thyristor controlled reactor to filter harmonics and to obtain required range of variable reactance. Alternatively, the static controlled reactance device (10) discussed above may be connected to the secondary winding of a series transformer (12) having its primary winding connected in series to the transmission line. In a three phase transmission system, the controlled reactance device (10) may be connected in delta configuration on the secondary side of the series transformer (12) to eliminate triple harmonics. With series transformer (12), secondary windings to which the controlled reactances are connected could be arranged for six-pulse or twelve-pulse operation.

Method of monitoring induction heating cycle

Abstract: A method of monitoring a heating cycle of an induction heating system wherein an inductor encircles a metal workpiece and an alternating current is applied through the inductor from a power supply during the heating cycle This method comprising the steps of generating an analog signal representative of the voltage across said inductor, as the voltage varies during said heating cycle by changes in the electromagnetic characteristics of the workpiece as the workpiece is being heated; digitizing the voltage representative analog signal; creating a trace of the digitized voltage representative analog signal, with the trace being indicative of the electromagnetic characteristic of the workpiece as sensed by the inductor voltage during the heating cycle; and, comparing the created trace with a preselected pattern This method can be performed with the workpiece moving through the inductor during said heating cycle and when the heating cycle includes a number of sub-cycles when the power supply is energizing the inductor separated by periods when the power supply is not energizing the inductor

Self-regulated transformer-inductor with air gaps

Abstract: The transformer comprises a three-limbed magnetic core having two outer limbs each defining a central air gap. Two windings, an alternating current one and a direct current one, are wound around each outer limb. Primary and secondary windings are disposed on the center limb, the primary one being supplied with alternating current from a source, and the secondary one supplying with alternating current an external load. The two alternating current windings are connected in series and supplied with alternating current by the source, possibly through an additional winding wound around the center limb, while the two direct current windings are connected in series and supplied by the current in the alternating current windings rectified through a diode bridge. The current in the two direct current windings induces a magnetic flux in a closed circuit defined by the outer limbs. The alternating currents in the primary winding and in the two alternating current windings are coupled to first and second alternating current magnetic fluxes assisting each other in the center limb and respectively flowing in two closed magnetic circuits defined, on the one hand, by the center limb and one outer limb, and, on the other hand, by the center limb and the other outer limb. The transformer supplies the external load with electric energy from the source while regulating the source and supply voltages.

Circuit for starting and operating a gas discharge lamp

Abstract: A circuit is disclosed which is capable of positively shifting a gas discharge lamp from its off-state to its on-state without emitting light flashes and further positively maintains the gas discharge lamp in its on-state when first ignited. The circuit contains an oscillator device which generates and supplies an oscillator signal of a specific oscillator frequency from two output terminals of the oscillator device. It also contains a current limiting device an a parallel-resonance circuit comprising a capacitor and an inductor. The parallel resonance circuit has a frequency of resonance substantially identical to the oscillator frequency. The current limiting device and parallel-resonance circuit are connected in a series configuration across the output terminals of the oscillator device. Further, the gas discharge lamp is connected across or in parallel with the parallel-resonance circuit. The current limiting device preferably constitutes an inductor of a series-resonance circuit, the resonance frequency of which is lower than the oscillator frequency of the oscillator device. The oscillator device is preferably tuned to the frequency of resonance of the parallel-resonance circuit.

Stabilizing the Frequency of Hysteretic Current-Mode DC/DC Converters

Abstract: A systematic investigation of methods to stabilize the operating frequency of hysteretic current-mode dc/dc converters through control of the current hysteresis is presented. The control laws for every power stage are derived, and two open-loop and two closed-loop circuits are shown and analized in detail. The interaction of the major voltage control loop and the frequency control circuitry is also investigated for buck converters. It is shown that, if the average inductor current is programmed, the two mechanisms are independent, while if the peak inductor current is programmed, they are not. The frequency control circuitry in the latter case decreases the phase margin of the voltage control loop and can lead to instability. Simple circuits are developed to implement the superior average inductor-current programming. As a consequence of being controlled via the current hysteresis, the operating frequency cannot be stabilized in the light mode, where VO/RL < IH/2. In the special case, where the frequency of the converter is stabilized by a phase-locked loop, a method and circuit are shown to solve this problem and achieve constant frequency operation at any load.

Stabilized welding power source including a series-resonant current-regulated converter using a transformer having an air-gapped core

Abstract: A pulse arc welding power supply incorporating one or more series resonant converters (SRC) for converting D.C. power to A.C. power which is then rectified to supply welding current. Each series resonant converter includes a series resonant tank circuit consisting of a capacitor, an inductor and the primary winding of a transformer whose secondary winding supplies current to the welding arc. The undesirable secondary output capacitor of the prior art is eliminated, as all the capacitance in the series resonant circuit is located on the primary side of the transformer. Current sensors sense the ringing current in the resonant circuit and also the load current and produce respective feedback signals which are used to control the switching frequency of an SCR bridge in the tank circuit, thereby maintaining the welding current at a desired value. Inner and outer current regulating loops, including a ramp generator, compensate for non-linearity in the continuous conduction mode of the SRC by limiting the switching frequency of the SCRs. a fault-predicting circuit also further limits the switching frequency in the continuous current mode for additional protection.

Modular electrical connector

Abstract: A modular jack comprising an insulating body member wherein a plurality of electrical contacts engaged capacitors and which also may be provided with ferrite inductors to produce series inductance

Design Considerations for Very High Frequency Resonant Mode DC/DC Converters

Abstract: The demand for higher switching frequencies in power converters has rekindled interest in resonant mode topologies. Conventional resonant converter circuits, however, are not optimized for high-frequency operation. A new resonant mode dc/dc converter topology exhibits desirable characteristics including zero switching losses, elimination of snubbers, simple control strategy, and circuit operation that is insensitive to parasitics such as diode reverse recovery. Analysis and design techniques are discussed in detail and are experimentally verified with a 150-W prototype converter operating in the frequency range 500 kHz-1 MHz.

Two-inductor boost and buck converters

Abstract: The derivation, analysis and design of a coupled inductor boost converter is presented. Aspects of the qualitative ac behavior of coupled inductor converters are discussed. Considerations for the design of the magnetics for such converters is addressed.

Output impedance considerations for switching regulators with current-injected control

Abstract: The output Impedance of current-Injected controlled (CIC) buck regulators can be significantly reduced by deriving the current control signal from the output capacitor Instead of the Inductor. This technique Is shown to be mathematically equivalent to CIC with load-current feedforward. Performance comparisons with normally Implemented CIC and voltage control are given.

Switching power supply filter

Abstract: A filter for a switching power supply The filter includes a common mode inductor with coil configurations allowing differential mode current from a dc source to pass through but attenuating common mode noise from the power supply so that the noise does not reach the dc source The invention also includes the use of feed through capacitors at the switching power supply input terminals to provide further high-frequency noise attenuation

A 3-phase inductor fed SMR converter with high frequency isolation, high power density and improved power factor

Abstract: A novel two stage Inductor fed Switch Mode Rectifier (SMR) topology has been developed and presented In this paper. Its advantages over other SMR topologies Include; high Input power factor; Improved reliability; high power density; minimum Input line current harmonic distortion; elimination of the Input filter AC capacitors and elimination of of the DC link capacitor.

Losses in high-power bipolar transistors

Abstract: The calculation of power losses in high-power bipolar transistors is examined for several of the commonly encountered types of power circuits. The magnitude of switching and conduction losses is dependent on the type of circuit in which they are used, the type of load, switching frequency, and characteristics of the transistor itself. Curves, based on computer simulation and mathematical analysis, are presented to aid in the calculation of these losses. Parameters taken into account are dynamic saturation voltage, load power factor, effect of snubbers, and recovery characteristics of circuit associated diodes.

Coupled-Inductor Magnetics in Power Electronics

Abstract: Leakages are inseparably associated with magnetic circuits and are always thought of in three different negative ways: either you have them and you don't want them (transformers), or you don't have them but want them (to limit transformer short circuit currents), or you have them and want them, but you don't have them in the right amount (coupled-inductor magnetic structures). The methods of how to introduce the leakages at appropriate places and in just the right amounts in coupled-inductor magnetic structures are presented here, in order to optimize the performance of switching dc-to-dc converters.

Quasi-linear controllable inductor

Abstract: A magnetic structure consisting of two ferromagnetic cores and three windings is shown to behave as a quasi-linear electronically controllable inductor. Together with the controllable resistor and capacitor it constitutes a complete set of components with electronically variable fundamental electrical properties: resistance, capacitance, and inductance. In contrast to the other two components, the power-handling capability of a controllable inductor is not limited a priori. Because of this, the spectrum of its potential applications is extremely wide.

Guidance system for inductively coupled electric vehicles

Abstract: An automatic guidance device for an electrically driven vehicle inductively coupled by a power receiver core to a roadway core connected to power source. The device which is attached to the power receiver core or to a ferrous bar connected to the underside of the vehicle comprises at least two sensor coils equally spaced from the midpoint of the power receiver core which is on the vehicle centerline. End portions of the vehicle core or bar which extend beyond the coils comprises magnetic poles which receive flux from the roadway inductor. Flux through the coils produces voltages which vary in proportion to their distance from the roadway inductor centerline and are compared to produce error signals used to control a steering servo on the vehicle. In event of roadway power failure a circuit is provided to enable the utilization of battery power to produce sufficient flux to maintain the production of error signals and thus steering control.

Dc to dc converter current pump.

Abstract: A DC to DC power converter designated a synchronous current pump (13) and operated in the preferred mode in synchronization with a discharge circuit (11) and using a capacitor (28) as the energy storage element, and in the preferred embodiment has in series with said capacitor the battery supply (10), an inductor (30), a diode (27a), and the primary winding (31a) of a transformer (31); and across said storage capacitor is an energy transfer FET switch (33) which is used for discharging said capacitor and transferring its stored energy to an output load capacitor (4) connected through a diode (32) to the secondary winding of said transformer In operation, the current pump supplies power efficiently and smoothly to a load discharge capacitor in synchronization with operation of the discharge circuit

Design considerations for very high frequency resonant mode dc/dc converters

Abstract: The demand for higher switching frequencies in power converters has rekindled interest in resonant mode topologies. Conventional resonant converter circuits, however, are not optimized for high-frequency operation. A new resonant mode dc/dc converter topology exhibits desirable characteristics including zero switching losses, elimination of snubbers, simple control strategy, and circuit operation that is insensitive to parasitics such as diode reverse recovery. Analysis and design techniques are discussed in detail and are experimentally verified with a 150-W prototype converter operating in the frequency range 500 kHz-1 MHz.

Current measuring and magnetic core compensating apparatus and method

Abstract: DC magnetic flux bias imposed on a magnetic core of a current transformer is compensated in response to an indication of the amplitude and duration of opposite polarity secondary winding current components. In a second embodiment, the magnetic bias is compensated by responding to the integral of the secondary current. The integral of the secondary current is a measure of the magnetic core flux variations. The durations of the positive and negative flux variations are compared.