Showing papers on "RLC circuit published in 1988"

A new method for determining the FET small-signal equivalent circuit

Abstract: A method to determine the small-signal equivalent circuit of FETs is proposed This method consists of a direct determination of both the extrinsic and intrinsic small-signal parameters in a low-frequency band This method is fast and accurate, and the determined equivalent circuit fits the S-parameters well up to 265 GHz >

Zero-voltage-switched multi-resonant converters including the buck and forward type

Abstract: A multi-resonant-switching network that operates under switching conditions that are favorable to both the active switch and the diode that constitute the switch. In a zero-current multi-resonant switch, the resonant circuit is formed in a T-network with resonant inductors in series with the switching devices. In a zero-voltage multi-resonant switch, the resonant circuit is formed in a π-network with resonant capacitors connected in parallel with the switch. In this way, the two networks are dual. During operation of a multi-resonant converter, a multi-resonant switches forms three different resonant circuits depending on whether the active switch and diode are open or closed. This results in operation of the converter with three different resonant stages in one cycle of operation. In practicing the present invention, certain rules are applied to derive a ZVS-MRC from a PWM converter. In particular, one resonant capacitor is placed in parallel with the active switch, which may be either uni-directional or bi-directional, another resonant capacitor is placed in parallel with the rectifying diode, and an inductor is inserted in the loop containing the switch and the diode. This loop can also contain voltage sources and filter or blocking capacitors. Improvement in the operation of ZVS-MRCs is obtained with synchronous rectification which is achieved by replacing rectifying diodes in a DC/DC converter with active devices, called synchronous rectifiers.

High-frequency series-resonant DC link power conversion

Abstract: An AC/DC conversion scheme is presented which eliminates the need for self-commutated devices and requires only 12 thyristors for full double bridge AC to AC power conversion. The system utilizes a series resonant DC link between the AC/DC and DC/AC converters. This series resonant scheme is, in effect, the dual of the parallel DC resonant converter. The DC resonant circuit can be essentially considered as a commutating circuit which ensures turn-off of all twelve thyristors by providing the necessary zero-current instants. A significantly improved sinusoidal current waveform can be obtained at both the input and output compared to conventional high-power converters by the use of high-frequency pulse density modulation. >

Static power conversion method and apparatus having essentially zero switching losses and clamped voltage levels

Abstract: A high efficiency power converter is achieved utilizing a resonant DC link between a DC source, such as a converter rectifying power from an AC power system, to a variable frequency voltage source inverter. A resonant circuit composed of an inductor and capacitor is connected to the DC power supply and to a DC bus supplying the inverter and is caused to oscillate stably at a high frequency to provide a uni-directional voltage across the DC bus which reaches zero volts during each cycle of oscillation of the resonant circuit. The switching devices of the inverter are controlled to switch on and off only at times when the DC bus voltage is zero, thereby eliminating switching losses in the inverter. The resonant circuit can be caused to oscillate utilizing pairs of switching devices in the inverter or a separate switching device across the capacitor, which again are caused to switch on and off only at times of zero voltage on the DC bus. For AC to AC conversion, enabling bi-directional power flow, the switching devices of the power source which converts AC power to DC power may have switching devices which are also switched only at the times of zero voltage so that switching losses in these devices is also minimized. A clamp limits the maximum voltage applied to the switching devices, thereby reducing voltage stresses on the devices, and preferably returns energy to the resonant circuit during each cycle of oscillation.

A new family of resonant rectifier circuits for high frequency DC-DC converter applications

Abstract: A family of rectifiers suitable for operation at high frequencies is presented. These rectifiers use naturally occurring component parasitics to control diode switching thereby minimizing parasitic ringing and improving rectification efficiency by reducing the flow of harmonic currents. The input impedance of the resonant rectifier is linear, which makes possible an accurate adjustment of the rectifier to present the proper load impedance to an inverter. When a resonant rectifier is coupled to a resonant inverter in this manner, a fully resonant DC-to-DC converter is produced. With these circuits it is possible to achieve a very low input/output ripple and EMI since voltages and currents seen by the filters are confined to a very narrow frequency range compared to conventional squarewave converters. >

Simple model for the input impedance of coax-fed rectangular microstrip patch antenna for CAD

Abstract: We present a simple model for the input impedance of a rectangular microstrip patch antenna. This model is well suited for computer aided design (CAD). It is based on classical methods: (a) the cavity model determining the frequency and the input resistance at resonance, (b) the dynamic permittivity of a rectangular microstrip patch antenna (to take into account the influence of the fringing field at the edges of the rectangular patch antenna) and (c) the resonant parallel RLC circuit with an inductive reactance. This model is valid for electrically thick substrates. The theoretical results are in good agreement with experimental data.

A resonant DC-to-DC converter operating at 22 megahertz

Abstract: An experimental DC-to-DC converter prototype based on a zero-voltage switching, resonant circuit topology is described. The converter is suitable for mounting directly on a circuit card. The unit provides a regulated 5 V output at power levels up to 50 W with an input between 40 and 60 V. The switching frequency is between 20 and 24 MHz, depending on the input voltage and load. Differential input and output ripple and EMI are extremely low and somewhat difficult to measure. The converter prototype has been designed to demonstrate compatibility with a fully automated assembly process based on surface-mount technology. Solutions are presented to a number of problems, including MOSFET gate-drive and rectifier diode capacitance, that have seriously limited the performance of high-frequency converters operating with useful input and output voltages. >

Half-bridge zero-voltage switched multi-resonant converters

Abstract: A half-bridge zero-voltage-switched multi-resonant converter. The converter basically comprises a device for converting an input voltage signal to a DC output signal to be imposed across a load. The device includes input terminals for receiving the input signal and output terminals for imposing the DC output signal across the load. Serially connected first and second switching assemblies are connected in parallel across the input terminals. Each of the first and second switching assemblies includes a transistor switch, a diode and a capacitor all arranged in parallel. The device further includes a transformer having a primary winding and serially connected first and second secondary windings. A first rectifier in parallel with a first resonant capacitor is used to connect the first secondary winding across the output terminals. Circuitry is provided for connecting the primary winding of the transformer to the input terminals and to the serial connection between the first and second switching assemblies. In order to complete the zero-voltage-switched multi-resonant converter for off-line use, a resonant circuit is formed with the first and second resonant capacitors and the total inductance of the primary winding of the transformer.

Quasi-resonant current mode static power conversion method and apparatus

Abstract: An inverter (30) has a resonant circuit composed of a parallel connected inductor (46) and capacitor (45) and a filter capacitor (47) connected in series with the inductor which has a capacitance substantially greater than the resonant capacitor. A half bridge or full bridge switching circuit formed of pairs (34, 35) of gate controlled switching devices is connected to a DC power supply (31, 32) and to the resonant circuit and filter capacitor (47) with the switching devices (34, 35) being switched to provide a relatively high frequency, e.g., 20 KHz or higher, resonant current in the resonant circuit. The filter capacitor (47) is of a size such that the high frequency component of the current flowing in the resonant circuit does not result in a substantial voltage at the switching frequency appearing across the filter capacitor (47).

Electronic data communications system

Abstract: A data transmission system for the non-contact transmission of data between a station (1) and a portable data card (2), both of which contain resonant circuits (5, 11) tuned to the same frequency The data card (2) receives power from the station (1) via inductive coupling of the two resonant circuits and transmits data to the station by means of a loading circuit (14) on the card which loads the card resonant circuit and hence, by mutual coupling, the station resonant circuit in response to data stored within the card The card also contains a reading circuit (17) containing a pulse generation circuit which generates a pulse whenever the power received by the card resonant circuit is interrupted and then restored Data may thus be transmitted from the station to the card by deactuating the station resonant circuit in response to the data to be transmitted, the resulting pulses generated within the card being interpreted as the transmitted data

An improved resonant DC link invertor for induction motor drives

Abstract: The authors present a bidirectional initial current control concept which solves the voltage overshoot problem in the resonant link and establishes reliable zero-voltage crossing for smooth inverter operation. The resonant circuit is analyzed to establish the criteria for initial current selection. A circuit is proposed to establish the bidirectional initial current. The improved inverter permits successful operation at 50 kHz resonant frequency and can potentially operate up to 100 kHz. The control of the inverter, which involves prediction of the inverter input current, is formulated. A complete inverter-fed induction motor speed control system is simulated using PC-SIMNON. The simulation study at both 50 kHz and 25 kHz resonant frequency indicates the superiority of the inverter at higher resonant frequency. >

Development of active filter with series resonant circuit

Abstract: An active AC harmonic filter, composed of high-frequency inverters and a series-resonant LC circuit turned to the fundamental frequency, is proposed to solve harmonic distortion problems on distribution systems at lower cost and with higher efficiency. The design includes a voltage-source inverter for further decrease of the loss, a static-induction thyristor for instantaneous current response, control logic that takes into account the coupling circuit characteristics, and high-speed harmonic voltage detection to suppress overloading of the customer's LC filter. Operational experience with a prototype filter on a 6.6 kV system is presented, verifying reduction of the operating and improvement of the transient response. In particular, there is a sharp reduction of inverter rating and operating loss about one-third to one-fourth, compared to results for an active filter without a coupling circuit. >

Multiple frequency theft detection system

Abstract: A swept frequency theft detection system for detecting different resonant circuit targets which are resonant at different frequencies. The system comprises arrangements to generate swept frequency transmitter signals centered at different frequencies but which are swept in synchronism. Also provided are antennas formed by offset loops, with the loops of different frequency antennas lying along different diagonal lines.

Resonant p-i-n-FET receivers for lightwave subcarrier systems

Abstract: A theoretical and experimental analysis of narrowband resonant direct-detection p-i-n-FET receivers for subcarrier multiple-access networks is described It is shown how a small inductance can be used to optimize the coupling between the p-i-n and FET, over a range of microwave subcarrier frequencies, minimizing the frequency-dependent thermal noise and leaving shot-noise as the ultimate limitation Shot-noise then establishes a fixed ratio of the total usable bandwidth to the minimum received power per channel, which for the binary FSK system considered is 61 GHz/ mu mW A resonant p-i-n-FET receiver, designed to provide maximum sensitivity between 25 and 50 GHz, has been constructed The measured signal-to-noise ratio is in excellent agreement with that predicted by the noise analysis >

Series resonant inverter with lossless snubber-resetting components

Abstract: A circuit for "resetting" snubbers in a series resonant bridge inverter maintains lossless snubber action during light-load and no-load inverter operation and during operation near resonance Series resonant circuit operation is controlled to be above the resonant frequency to ensure operation at a lagging power factor The snubber-resetting operation is facilitated by a relatively small inductor connected across the output terminals of the series resonant inverter

Electronic device for cosmetic and medical therapy

Abstract: An electronic device and method for use in cosmetic and medical treatment of a person by application of electrodes to a person's skin. The device includes a high frequency oscillating circuit for supplying high frequency current in the range of from 1 to 2 megacycles per second. The high frequency oscillating circuit automatically reduces the supply power when the load impedance of the person is lowered. The high-frequency oscillating circuit includes an oscillating circuit producing an oscillation signal, a preamplifier boosting the oscillating circuit and an amplifier receiving the boosted oscillating circuit and outputting an amplified oscillating signal. Resonance circuit means are provided receiving the amplified oscilliating signal and outputting an oscillating signal with resonance at an operating frequency. An output amplifier is preferably connected to the resonance circuit receiving a signal output by the resonant circuit and outputting an amplified at an operating frequency. A high-frequency transformer is provided having a first and second winding and a center housing adjacent the second transformer winding having an aluminum cylinder for dissipating heat and reducing the load inductance of the first and second winding so as to increase the resonance frequency. The device includes an electrical current application element which is connected to the second winding of the transformer apparatus for transmitting high frequency current capacitively to the epidermis of the person being treated. Both an active electrode and a neutral return electrode are provided to avoid dispersion of electric current flow.

Fluorescent lamp system

Abstract: A fluorescent lamp system utilizes boost power factor correction. The fluorescent lamp system includes a power source, a reference voltage and a fluorescent lamp. A resonant circuit supplies power to the fluorescent lamp. A first capacitor is connected between a first end of the resonant circuit and the reference voltage. A second capacitor is connected between the first end of the resonant circuit and the power source. A first switch is connected between a second end of the resonant circuit and the reference voltage. A second switch is connected between the second end of the resonant circuit and the power source. A control module operates the first switch and the second switch so that the resonant circuit operates at near resonant frequency. The control module is integrated on a single integrated circuit. The first switch and the second switch may be also integrated on the single integrated circuit. Alternately, only one of the switches, or neither of the switches may be integrated on the single integrated circuit.

Multi-function modulation and center frequency control port for voltage controlled oscillator

Abstract: A circuit for use in conjunction with a voltage controlled oscillator (VCO). The circuit introduces modulation into a radio system (to create a substantially flat frequency response) at the same VCO port at which VCO frequency centering and negative bias control signals are introduced. A potentiometer is utilized both for providing an adjustable negative bias to the varactor in the VCO resonant circuit and for setting the VCO to the appropriate center frequency. Modulation compensation circuitry is coupled to the control arm of the potentiometer and to the anode of the varactor (via a choke 4). The modulation compensating circuitry is preferably designed to have a transfer function that is substantially the inverse of the closed loop transfer function of the phase locked loop system with respect to the frequency modulation of the VCO.

TV-RF input circuit

Abstract: TV-RF input circuit provided with an RF coupling device via which an aerial input is coupled to first, second and third parallel tunable RF resonant circuits (11, 21, 31) for a parallel selection of a desired frequency in first, second and third TV frequency bands (50 - 160 MHz; 160 - 470 MHz; 470 - 860 MHz) substantially succeeding one another in frequency, said RF coupling device having a high-pass η-­section (C, L2, L3) for suppressing frequencies below the first TV frequency band and being provided with a capacitive series branch and first and second inductive shunt branches, said η-section (C, L2, L3) being coupled via a first series inductance (L1) to the first RF resonant circuit (11). In order to ensure, without extra elements, a substantially reflection-free supply of TV-RF reception signals to each of the said RF resonant circuits, second and third series inductances (L2, L3) of mutually equal order are arranged in the first and second inductive shunt branches, respectively, which inductances are coupled at one end to either side of a capacitor (C) arranged in the capacitive series branch and at the other end to the second and third RF resonant circuits (21, 31), respectively, said first series inductance (L1) being at least several times larger than each of the two other series (L2, L3) inductances.

A flexible detection label

Abstract: A flexible detection label (1) for an electronic detection system, comprising a thin, platelike flexible carrier (2) having on both sides elements made from flexible material, jointly forming at least one resonant circuit. The resonant circuit includes at least two conductor tracks (9, 13) formed as coils (17, 18), said tracks being insulated from one another and disposed on opposite surfaces of the carrier, each track having two ends connected to a conductive region forming a capacitor electrode. The two capacitor electrodes (8, 10) on one surface of the carrier are exactly opposite corresponding capacitor electrodes (11, 12) on the other surface of the carrier, and opposite capacitor electrodes are substantially equally large.

Continuous phase shifter for a phased array hyperthermia system

Abstract: A continuous microstrip phase shifter suitable for use in a phased array microwave hyperthermia system operating at 915 MHz is provided. The phase shifter utilizes a three dB quadrature hybrid coupler in conjunction with microstrip lines to change the phase of a transmitted wave. The phase change is introduced through the reflection ports of the coupler which are loaded with identical parallel resonant circuits. An abrupt junction varactor capacitance in parallel with a distributed inductance forms a voltage-tunable resonant circuit. The resonant element values are chosen to give a specified continuous phase variation with minimum transmission loss. This is accomplished without additional microwave circuit elements.

Dual resonant frequency arc lamp power supply

Abstract: An apparatus for starting and operating an arc lamp used in health care applications includes means for producing a rectangular wave AC signal with a frequency controlled by external resistive and capacitive networks. Parallel-connected inductor and capacitor means form a resonant circuit to receive the rectangular wave AC signal. Additional capacitor means connected in series with the arc lamp is closed into the circuit when the arc lamp begins to conduct, thereby changing the resonant frequency of the parallel inductor-capacitor resonant circuit. The detection of current flow in the arc lamp causes a resistor to be switched into the resistive network controlling the frequency of the pulse-width modulated signal, thereby changing the frequency of the rectangular wave AC signal.

Control circuit for resonant converters

Abstract: An improved control circuits is disclosed for use with a resonant converter having a resonant circuit and a first and a second plurality of switches for transferring electrical power between first and second terminals. The improved control circuit comprises a power transfer control or an outer control loop and a resonant circuit control or an inner control loop with the resonant circuit control having a predictor circuit. The power transfer control regulates the electrical power transferred between the first and second terminals through selective conduction of the first and second plurality of switches for selectively initiating oscillation of the resonant circuit to provide resonant pulses of the resonant circuit. A predictor circuit instantaneously monitors the operation of the resonant converter and instantaneously and continuously predicts prior to the completion of each resonant portion when the initiation of conduction of one of the switches will produce a resonant portion having a final waveform in conformity with a pre-established standard. The resonant circuit control compares an output of the predictor circuit to the pre-established standard for initiating conduction of the switches within each resonant portion to conform each resonant portion to the pre-established standard.

Bandpass filter circuit arrangement

Abstract: A bandpass filter circuit arrangement in which a pair of parallel-resonant circuits (1, 2) are reactively intercoupled has a pair of signal input terminals (16, 17) connected to one of the resonant circuits (1) and a pair of output terminals (18, 19) connected to the other resonant circuit (2). Tuning of the filter is accomplished by varying the capacitive component of each circuit by varying the output of a tuning voltage source (20). In order to compensate for the deviation from the optimum intercoupling which would otherwise occur with change of tuning frequency the capacitive component of each resonant circuit is formed by two pairs (5, 7 and 6,8, or 9,11 and 10, 12) of capacitors in series, each series-connected pair effectively forming a varaible capacitive voltage divider to the tap on which the reactive intercoupling means (15) is connected. One capacitor (5, 6, 9 or 10) of each pair is variable, and all these are adjusted at the same rate. The other capacitor (7, 8, 11 or 12) is fixed, and the ratio between the capacitances of the fixed capacitors of each capacitive component are chosen so that the required degree of compensation is obtained. As an alternative the fixed capacitors may be replaced by short circuits and the variable capacitors of each capacitive component may be varied at different rates.

Inverter capable of controlling operating frequency

Abstract: An inverter is made up of a parallel circuit as a voltage resonance circuit, and a first diode, which are connected in series between both ends of a power source. The parallel resonance circuit includes the primary winding of an output transformer of the leakage type, and a resonance capacitor. The first diode is connected at the cathode to the primary winding of the output transformer. The secondary winding of the output transformer is coupled with a load such as a discharge lamp. The cathode and anode of the first diode are respectively connected to the collector and emitter of a transistor. A series circuit of a second diode and capacitor is connected across the collector-emitter path of the transistor. The second diode is forwardly arranged with respect to the transistor. A voltage detector comprises the capacitor and two resistors which are connected in series, and connected across the capacitor. The output voltage is derived from the node of those resistors. An error amplifier compares the output voltage of the voltage detector and an output voltage from a reference voltage source. A VCO oscillates at a switching frequency based on the comparison result. The oscillation output signal is applied to the base of the transistor.

Automatic overvoltage protection circuit

Abstract: An automatic overvoltage protection circuit is provided for an electrical power supply of the type comprising a variable speed three phase alternator (50) having a permanent magnet rotor and three stator output windings (51, 52 and 53), a gated three phase rectifier bridge (60) connected to the three stator output windings and producing a d.c. output voltage, and a control circuit (120) for supplying gating signals at controlled firing angles to the gated three phase rectifier bridge. The control circuit includes first, second and third reference circuits (73, 74 and 75) each including a resonant LRC circuit and connected to a respective one of the three stator output windings, a gating logic circuit (135) connected to the first, second and third reference circuits and providing six outputs, feedback means (122) connected to receive the d.c. output voltage for generating an error voltage, and comparator and isolation means (140 and 145) connected to the gating logic circuit and to the feedback means for generating firing signals for the gated three phase rectifier bridge. The automatic overvoltage protection circuit limits the firing angle of the firing signals at high speed of the alternator to ≅59° while allowing the firing angle of the firing signals at low speed to be ≅0°. This is accomplished by deliberately selecting the Q and resonant frequency of the reference circuits to achieve this beneficial result.

High voltage DC power supply

Abstract: A DC power supply for a traveling wave tube having cathode, collector and helix electrodes responds to a DC power source and a high frequency switching source. A switch controlled by the switching source is opened and closed at a fixed frequency and variable duty cycle determined by the helix-cathode voltage. A flyback choke is connected to the switch and DC power supply so current flows between the power source via the choke to the switch and a series resonant circuit while the switch is closed. First and second capacitors in separate branch circuits of the resonant circuit are respectively connected to first and second AC to DC converter and voltage multiplier stacks; each multiplier in the stacks includes a pair of branches with oppositely poled plural signal switching diodes and a capacitor. The cathode and helix are respectively connected to output terminals of the first and second stacks, while the collector is connected to a terminal between the first and second stacks. The resonant circuit is connected with the switch, flyback choke and voltage multipliers so that while the switch is closed a half-wave rectified current waveform at the resonant circuit resonant frequency flows in the resonant circuit and a ramping current having a first polarity direction flows in the choke. A ramping current having a second plurality direction flows in the choke and resonant circuit while the switch is open.

The graphical D-Q transformation of general power switching converters

Abstract: A novel circuit d-q transformation concept is introduced to analyze AC converters such as inverters, rectifiers and cycloconverters with ease The equivalent linear time-invariant circuit is obtained by substituting switches with equivalent turn-ratio variable transformers and changing balanced AC reactors into equivalent DC reactors combined by gyrators This circuit allows the utilization of power linear system analysis techniques such as Laplace transforms, which otherwise could not be applied to time-varying switching systems The modeling procedure is shown for a controlled rectifier-inverter circuit An analysis example is given for a buck-boost inverter, and the result is compared with that of the conventional approach This approach is applicable to all AC converter families to determine the AC transfer function and the DC operating points It is determined that the switching systems are equivalent to RLC filter circuits with transformers and gyrators >

Inductive proximity switch oscillator having same activating range for ferrous and nonferrous metals

Abstract: An inductive proximity switch including an oscillator circuit with a frequency resonant circuit (1) determining the frequency and with an impedance member (7) determining the amplification, this impedance member containing an impedance resonant circuit with a sensor coil (9) that can be influenced by the approach of a metallic trigger. In order to provide that the proximity switch has the same activating range for ferrous and nonferrous trigger metals, the resonant frequency (fo) of the frequency resonant circuit (1) and the critical impedance value (Zo) of the impedance member (7) are tuned, according to this invention, to the coordinates (fo,Zo) of the point of intersection (Po) of the impedance/frequency characteristics (II, III), resulting for respectively identical activating range, for an NF trigger and for an FE trigger.