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Showing papers on "Negative impedance converter published in 1989"


Proceedings ArticleDOI
26 Jun 1989
TL;DR: In this paper, the authors proposed a control strategy for the matrix converter which allows output voltage of 0.866 times the supply voltage to be generated, while eliminating voltage and current spikes in the commutation.
Abstract: The authors propose a control strategy for the matrix converter which allows output voltage of 0.866 times the supply voltage to be generated. They discuss how to eliminate voltage and current spikes in the commutation. The system operation is examined and confirmed by experiments using a matrix converter with anti-parallel-connected SITs (static induction thyristors). >

160 citations


Patent
Gary L. Pace1, David H. Overton1
24 May 1989
TL;DR: The DC-DC converter as mentioned in this paper operates within a paging receiver and boosts a voltage from a single cell battery to substantially 3.1 VDC in order to operate circuits which require more voltage than that produced by the single-cell battery.
Abstract: A DC-DC converter regulates the maximum current through an inductor. The DC-DC converter operates within a paging receiver and boosts a voltage from a single cell battery to substantially 3.1 VDC in order to operate circuits which require more voltage than that produced by the single cell battery. Such circuits include CMOS microcomputers and code plug. The DC-DC converter is current regulated thus providing for improved power conversion efficiency. The DC-DC converter is active when the voltage is below a minimum voltage and inactive when above a maximum voltage. The DC-DC converter provides for a wide range of load currents from the converted voltage without being controlled by a microcomputer and while delivering the power to the loads with an improved efficiency.

104 citations


Patent
24 Jan 1989
TL;DR: In this paper, a system for regulating the operating point of a direct current power supply comprising a current generator system connected to a pulse width modulation converter is presented, which is applicable to regulation of the electrical power supply circuits of spacecraft, space probes, satellites and the like.
Abstract: A system for regulating the operating point of a direct current power supply comprising a current generator system connected to a pulse width modulation converter includes a circuit for sampling and measuring the voltage and the current supplied by the current generator. A threshold detector circuit responding to stalling of the converter supplies a logic signal representing the stalled or non-stalled state of the converter relative to threshold values. A regulation loop includes a switching device for inverting the sign of the error signal so that the operating point can be moved towards the maximum power point on the output current-voltage characteristic of the current generator. The system is applicable to regulation of the electrical power supply circuits of spacecraft, space probes, satellites and the like.

96 citations


Journal ArticleDOI
TL;DR: In this article, two frequency domain methods were presented to model and identify the equivalent impedance transfer function of a distribution or transmission system using recorded voltage and current transients due to capacitor switching.
Abstract: This paper presents two frequency domain methods to model and identify the equivalent impedance transfer function of a distribution or transmission system using recorded voltage and current transients due to capacitor switching. The first frequency domain method discussed was the fast Fourier transform method of identifying the frequency components of the voltage and current, then using the voltage and current spectra to find the impedance transfer function. The second method first obtains estimates of the sample auto and cross-correlation functions. These functions are then used, via the FFT, to find the respective power spectra of the signals, and finally to find the impedance transfer function. The FFT method was found to produce accurate results when the frequency components signal to noise ratios are large. The power spectral identification method and the coherence function added a measure to reject the frequency components that are contaminated with noise, but this method suffers from spurious cross correlations between the voltage and current. Once the impedance transfer function has been identified, several techniques were investigated that fit a parametric model to the function. Two polynomial transfer functions were fit to the real and imaginary parts of the impedance. These polynomials resulted in accurate representations of the impedance function of the system. The second parametric method discussed used the poles and zeroes identified from the impedance transfer function to develop an equivalent circuit representation of the system. This equivalent circuit did not fit the estimated impedance/frequency characteristics as well as the polynomial transfer function.

83 citations


Patent
15 Jun 1989
TL;DR: Two or more buck converter circuits are cascaded in such a manner that the output of one serves as the input to the next, with the input voltage to each succeeding buck converter stage being reduced in magnitude as mentioned in this paper.
Abstract: Two or more buck converter circuits are cascaded in such a manner that the output of one serves as the input to the next, with the input voltage to each succeeding buck converter stage being reduced in magnitude. The total circuit losses are substantially reduced as compared to the losses generated in a single buck converter having the same input voltage range and the same output voltage and output current. Both positive and negative output terminals may be provided for an output stage.

63 citations


Patent
03 Jan 1989
TL;DR: In this paper, techniques for recovery from a low impedance condition during cathodic arc or electric vapor thin film processes are disclosed, followed automatically by active clearing of the cloud to return it to the proper impedance or resistance state.
Abstract: Techniques for recovery from a low impedance conditions during cathodic arc or electric vapor thin film processes are disclosed. Sensing of a low impedance condition is achieved followed automatically by active clearing of the cloud to return it to the proper impedance or resistance state. Active clearing is accomplished by a progressive increase in the output of bias voltage supply. Regulation of the bias voltage supply switches between voltage or power modes and a current mode of regulation. Circuitry disclosed is designed to readily modify existing power supplies to achieve the methods discussed and to linearly increase the current output by it.

46 citations


Patent
26 Jun 1989
TL;DR: In this article, an improved AC-AC series-resonant converters incorporating power pulse modulation with internal frequencies of tens of kHz is applied to a series-reonant converter system for generating synthesized multiphase bipolar waveforms with reversible power flow and low distortion.
Abstract: An apparatus and method is disclosed for an improved AC--AC series-resonant converters incorporating power pulse modulation with internal frequencies of tens of kHz is applied to a series-resonant converter system for generating synthesized multiphase bipolar waveforms with reversible power flow and low distortion. The high pulse frequency allows the application of the principle of modulation and demodulation for fast system response. Switches are required which have bidirectional current conduction and voltage blocking ability. The conventional series-resonant AC--AC converter applies a total of 24 anti-parallel thyristors. The circuit configuration of the present invention is a series-resonant AC--AC converter with only 12 thyristors. Use of the converter results in a higher efficiency and lower costs. The alternative power circuit has three neutrals, related to the polyphase source, the load and the converter, which may be interconnected and the high-frequency component of the source and load currents will flow through the connection between the neutrals.

45 citations


Patent
03 Jul 1989
TL;DR: In this article, a buck/boost converter is driven by a high frequency dc-to-dc flyback converter to provide substantially constant output power, independent of the output voltage, to an inductor to provide current to a load having a v-i characteristic that is suitable for use with a current power source, such as a plurality of parallely connected LEDs.
Abstract: A buck/boost converter is driven by a high frequency dc-to-dc flyback converter to provide substantially constant output power, independent of the output voltage, to an inductor to provide current to a load having a v-i characteristic that is suitable for use with a current power source, such as a plurality of parallely-connected LEDs. The flyback converter repetitively generates a battery-simulated output voltage that is current-limited and which may be used to charge a battery as well as to provide power to the buck/boost converter. The buck/boost converter includes a switching circuit for repetitively transferring current to the load and a current sensor circuit operating in conjunction with the switching circuit to change the state of the buck/boost converter to repetitively open the switching means and initiate release of the current to the load.

39 citations


Patent
13 Nov 1989
TL;DR: In this paper, a power converter circuit directly or indirectly connected to the power distribution network is implemented in a manner as to consent the utilization of at least a portion of the energy associated with the spike by storing portion of said energy in the reactive components of the converter circuit itself instead of dissipating completely the energy through a dissipating element as in prior art arrangements.
Abstract: In a power converter circuit directly or indirectly connected to the power distribution network, the protection from voltage spikes which may occur on the power supply rail is implemented in a manner as to consent the utilization of at least a portion of the energy associated with the spike by storing portion of said energy in the reactive components of the converter circuit itself instead of dissipating completely the energy through a dissipating elements as in prior art arrangements. The novel circuit arrangement utilizes one or two spike sensors the output signal or signals of which are fed to logic gates which determine a certain configuration of the analog switches of the converter circuit. A protection voltage limiting element (zener diode, avalanche diode, voltage-dependent resistor, etc.) is functionally connected across the analog switch connected between the reactive element of the converter circuit and the power supply rail and limits to its intrinsic breakdown voltage the maximum voltage across the switch.

32 citations


Patent
23 Feb 1989
TL;DR: In this article, a self-balancing reflectometer is described in conjunction with a system including an RF source, an RF load, and an RF transmission channel that carries RF signals transmitted by the source to the load.
Abstract: A preferred embodiment of a self-balancing reflectometer is disclosed in conjunction with a system including an RF source, an RF load, and an RF transmission channel that carries RF signals transmitted by the source to the load. The self-balancing reflectometer includes a load current sampler that generates a first sample signal related to load current by a first fixed value of gain and a load voltage sampler that generates a second sample signal related to load voltage by a voltage-responsive second variable value of gain. The first sample signal is subtracted from the second sample signal and the resulting difference signal is applied to the RF port of a double balanced mixer. The RF voltage signal appearing at the load is applied to the LO port of the mixer, which generates an IF signal that varies with both rapid load impedance modulation corresponding to load data and long term basal variations in load impedance unrelated to load data. A high gain amplifier generates output data signals corresponding to the load data and an integrator generates a gain adjustment voltage which varies with the long term variations. The gain adjustment voltage is applied to the load voltage sampler to vary the second variable value of gain in a manner to drive the difference signal to zero, thus automatically balancing the reflectometer. At the balance point, the value of the gain adjustment voltage is related to the value of load impedance by a known formula. The reflectometer is selectably responsive to either the rear or imaginary component of load impedance.

31 citations


Journal ArticleDOI
TL;DR: In this paper, a general configuration for a first order current processing all-pass filter is described, which requires an active element having unity current gain in conjunction with two passive components only (i.e., one resistance and one capacitance).
Abstract: A general configuration for a first order current processing allpass filter is described. It requires an active element having unity current gain in conjunction with two passive components only (i.e., one resistance and one capacitance). Two implementations using the following translinear circuits as active elements: (a) a negative impedance converter with current inversion (I-NIC) and (b) a current controlled current source (CCCS) have been inspected and experimentally compared. Because of the high performances obtained, they appear to be suitable for wideband applications.

Proceedings ArticleDOI
15 Oct 1989
TL;DR: In this article, the DC behavior of a constant-frequency, clamped-mode parallel-resonant converter operating above resonant frequency is characterized and the converter is shown to operate with zero-voltage turn-on for all the switches from no load to full load over a wide input range.
Abstract: The DC behavior of a constant-frequency, clamped-mode parallel-resonant converter operating above resonant frequency is characterized. The converter is shown to be able to operate with zero-voltage turn-on for all the switches from no load to full load over a wide input range. Various circuit operating modes are identified and their corresponding operating regions defined. DC characteristics for the converter design are derived. A 5 V, 50 W prototype converter operating at 104 kHz is breadboarded to show the feasibility of constant-frequency, zero-voltage-switching operation and to substantiate the analytical results. The converter is operated with zero-voltage switching from no load to full load over the entire input voltage range without any external antiparallel diodes and snubbers. The experimental results are in good agreement with the analytical predictions. An efficiency of 85% is achieved. >

Patent
28 Jul 1989
TL;DR: In this article, a split-series resistor with two clamping diodes of different types is used for ESD protection at an input pad, where some impedance is provided before the first hard diode, without causing an excessive total impedance.
Abstract: An integrated circuit which, for ESD protection at an input pad, uses a split series resistor, with two clamping diodes of different types. By splitting up the series resistance in this fashion, some impedance is provided before the first hard diode, without causing an excessive total impedance. When a positive-going transient appears at the pad, the current is limited only by a moderate impedance (which saves area); when a negative-going transient appears, the current is limited by a much higher impedance (which allows a lower leakage current to be achieved).

Patent
12 Apr 1989
TL;DR: In this paper, a DC-to-DC step-up converter is provided which employs high efficiency switching components such as MOSFET switching components in a main converter and provides a low power auxiliary converter to obtain the start up voltage required for operating the low resistance component of the main converter.
Abstract: A DC to DC step-up converter is provided which employs high efficiency switching components such as MOSFET switching components in a main converter and provides a low power auxiliary converter to obtain the start up voltage required for operating the low resistance component of the main converter. A control circuit is provided which utilizes either the start up voltage from the auxiliary converter or a feedback voltage from the main converter output to provide control input to the low resistance switching devices which inputs are operative to maintain the output voltage at a desired level.

Patent
Harold Seidel1
16 May 1989
TL;DR: In this article, a power converter includes an input primary switching system with its output connected to phase shift or impedance inversion circuit, and an output load circuit is connected in parallel with both the output of the impedance-inversion circuit and the input to the secondary switching system so that the capacitor voltage determined by the phase delay is controlling of the output voltage of the OLS.
Abstract: A power converter includes an input primary switching system with its output connected to phase shift or impedance inversion circuit. These two circuits cooperate to function as a current source at the output of the impedance inversion circuit. A secondary switching system is connected in parallel with the output of the impedance inversion circuit and is switched synchronously with a controlled phase delay to the input primary switching system to synchronously charge a charge storage capacitor. The phase delay determines the voltage of the charge storage capacitor. An output load circuit is connected in parallel with both the output of the impedance inversion circuit and the input to the secondary switching system so that the capacitor voltage determined by the phase delay is controlling of the output voltage of the output load circuit.

Patent
13 Apr 1989
TL;DR: In this article, a voltage divider network scales an input voltage for conversion to a linear current by a cascode current mirror and a gain resistor, which determines the transconductance of the conversion from voltage to current.
Abstract: A voltage to current converter circuit manufactured with a MOS process generates a linear reference current over a wide bandwidth and operates with an input signal that varies to either supply rail. A voltage divider network scales an input voltage for conversion to a linear current by a cascode current mirror and a gain resistor. The value of the gain resistor determines the transconductance of the conversion from voltage to current. A second current mirror provides feedback to keep the reference current accurate. An output stage makes available high impedance source and sink current output terminals wherein a source current and a sink current relative to the reference current are provided. Several voltage to current converter circuits may be coupled together to provide a addition, subtraction, multiplication, and other circuit and system functions.

Patent
20 Mar 1989
TL;DR: In this paper, a binary-to-ternary converter with an amplitude of 2.37 V± 10% was proposed to protect against high voltage-pulses from outside by serially connecting a protective resistance to the output.
Abstract: For a binary-to-ternary converter fed from a standard TTL supply of 5 V ± 5%, a minimum 4.75 V supply voltage is available. According to the amplitude requirement of the CCITT Recommendation G703, the positive and negative output pulses should have an amplitude of 2.37 V± 10%. A binary-to-ternary converter should be protected against high voltage-pulses from outside. This is achieved by serially connecting a protective resistance to the output. An unacceptable voltage loss will then develop through this arrangement. The binary-to-ternary converter according to the invention satisfies the abovementioned requirements without utilizing a transformer, despite the fact that the overall voltage swing for the ternary output signal corresponds with a higher value than the worst-­case 4.75 V supply voltage which is available.

Patent
24 Oct 1989
TL;DR: In this article, the phase currents of a frequency converter are measured by storing, in memory, signals corresponding to the current of the d.c. circuit of the converter and by producing a current value correspond to the phase current from the previous and the momentary signals.
Abstract: A procedure and apparatus for the measurement of the currents in a frequency converter, provides that the phase currents of the frequency converter are measured by storing, in memory, signals corresponding to the current of the d.c. circuit of the converter and by producing a current value corresponding to the phase current from the previous and the momentary signals.

Patent
24 Feb 1989
TL;DR: In this paper, a bipolar analog voltage is converted into a digital signal by sensing the polarity of the voltage and selectively supplying a bias voltage to an analog-to-digital converter, which can preferably be a charge balanced voltage to frequency converter, as a function of the sensed polarity.
Abstract: A bipolar analog voltage is converted into a digital signal by sensing the polarity of the voltage and selectively supplying a bias voltage to an analog-to-digital converter, which can preferably be a charge balanced voltage to frequency converter, as a function of the sensed polarity. The voltage to frequency converter has a double valued variable frequency output with a discontinuity at zero volt such that the converter derives a maximum output frequency for a maximum positive voltage and also for a negative value slightly displaced from zero; the voltage to the frequency converter minimum output frequency is derived from positive voltages slightly greater than zero and for maximum negative voltages. The converter output frequency and the sensed polarity are supplied to a frequency to digital converter which derives an output signal having a bit representing the polarity of the analog voltage and additional bits indicative of the magnitude of the analog voltage.

Patent
26 Dec 1989
TL;DR: In this article, a method of synthesizing a system which forces a finite value of an impedance to zero comprising positive current feedback of exactly specified nature and value of its transfer function and an internal negative voltage feedback ensuring inherent stability of the system is presented.
Abstract: A method of synthesizing a system which forces a finite value of an impedance to zero comprising positive current feedback of exactly specified nature and value of its transfer function and an internal negative voltage feedback ensuring inherent stability of the system. The converter is used to synthesize electric motor drive systems, incorporating any kind of motor, of infinite disturbance rejection ratio and zero-order dynamics and without position and velocity feedback.

Patent
18 Dec 1989
TL;DR: In this paper, the current output type digital-analog converter and a current/voltage converter are connected to an output terminal of the current-output type digital/analog converters.
Abstract: A digital-analog converter circuit comprising a current output type digital-analog converter and a current/voltage converter connected to an output terminal of the current output type digital/analog converter, the current/voltage converter including bias application means to always apply a bias voltage having a predetermined set value to the output terminal of the digital/analog converter.

Patent
Yoshihiro C1, Shozo C1, Mitsuhiko C
29 Nov 1989
TL;DR: A side tone preventive circuit for telephones is proposed in this paper, which prevents the output of the transmitter on the speaker's side from being transmitted to the receiver on the same side.
Abstract: A side tone preventive circuit for telephones which prevents the output of the transmitter on the speaker's side from being transmitted to the receiver on the same side. The balance of the impedance bridge in a bridge circuit for separating a transmission signal and a reception signal is automatically adjusted in accordance with the circuit impedance at the location at which a telephone is installed. An impedance measuring circuit measures the impedance of the telephone circuit, and a balance adjustment circuit the impedance of which is adjustable is provided in the bridge circuit. The impedance of the telephone circuit is measured at the time of installation of a telephone, and the imped­ance of the balance adjustment circuit is adjusted in correspondence with the result of measurement. Thus, the impedance balance of the bridge circuit is adjusted in correspondence with the circuit impedance, thereby effec­tively preventing a side tone.

Journal ArticleDOI
26 Jun 1989
TL;DR: In this paper, a single-stage current-fed DC-DC converter structure and control strategy is described, which allows simultaneous control of both output voltage and current flowing in the input inductor.
Abstract: A single-stage current-fed DC-DC converter structure and control strategy is described which allows simultaneous control of both output voltage and current flowing in the input inductor. This solution is well suited for high-power-density applications, since it results in very reduced converter size and power loss. Moreover, a very fast control-to-output response is obtained, together with stable operation even for large load and reference variations. Static and dynamic converter performance is investigated, and design criteria are given. Experimental results obtained on a prototype are reported. >

Patent
11 May 1989
TL;DR: In this paper, a method and apparatus to avoid commutation failure in a regenerative converter of a supply reversible converter of the voltage-source converter, in case of dynamic voltage depression, is presented.
Abstract: A method and apparatus to avoid commutation failure in a regenerative converter of a supply reversible converter of a voltage-source converter, in case of dynamic voltage depression. A firing control of the reversible converter is a function of the value of a link current setpoint of the voltage-source converter. The link current setpoint is determined from a measured link voltage actual value and from a determined link voltage setpoint. A measured link current actual value is monitored for overcurrent. Control signals are supplied to the reversible converter even when there is an overcurrent status message, when the reversible converter is switched over. The reversible converter of the voltage-source converter is thereby protected from commutation failure.

Patent
18 Dec 1989
TL;DR: In this article, an ohmic dissipation resistor (R), and a load impedance (ZL) of the resistive and/or capacitive type, through a negative impedance converter are used to modify the mechanical properties of the piezo-electric element.
Abstract: Conditioning of piezo electric elements. The conditioning process according to the invention consists in connecting in parallel, between the two terminals of the piezo electric element: . an ohmic dissipation resistor (R), . and a load impedance (ZL) of the resistive and/or capacitive type, through a negative impedance converter to modify the mechanical properties of the piezo- electric element. Application to the attenuation of vibrations.

Patent
22 Feb 1989
TL;DR: In this article, a power amplifier driven in the switching mode is started into oscillation by a pulse from an auxiliary oscillator when it is first activated, which produces the switching in of a feedback circuit, after which the amplifier oscillates in a self-excited mode, at a frequency determined by tuning of the resonant circuits.
Abstract: A power amplifier driven in the switching mode is started into oscillation by a pulse from an auxiliary oscillator when it is first activated. Reactive currents thereby resulting in an output filter network, containing a series resonant circuit followed by a parallel resonant circuit which is connected across a load impedance, then produce the switching in of a feedback circuit, after which the amplifier oscillates in a self-excited mode, at a frequency determined by the tuning of the resonant circuits. Branch circuits connected to the output filter network determine whether the load impedance is above or below the characteristic impedance value, which is a function of the inductance in the series resonant circuit and the capacitance in the parallel resonant circuit, and control an electronic switch which enables current-driven feedback when the load impedance is below the characteristic value and enables voltage feedback when the load impedance is above the characteristic value, thus providing the more stable type of feedback consistently, even though the load may fluctuate greatly. The electronic switch preferably operates with some hysteresis. This high frequency power oscillator adjusts itself automatically to mistuning of the output filter network as well as to large fluctuations of load impedance. The loss power in the amplifying elements of the power amplifier is very low and the efficiency very high.

Patent
06 Jan 1989
TL;DR: In this paper, an integrated circuit consisting of a switching circuit, a high impedance tail current source, and a pair of low impedances is disclosed for performing a current steering logic function.
Abstract: An integrated circuit, having applicability to GaAs circuitry, is disclosed for performing a current steering logic function. The integrated circuit comprises a switching circuit, a high impedance tail current source, and a pair of low impedances respectfully coupled to the tail current source through a respective one of the switching transistors. The resistors in the tail current source and in the load resistance are formed from sheet resistor material so that any process-induced variation in the resistivity of the sheet material causes a mutual but compensatory variation in both the load and current source resistors, maintaining a match between the current capability of the current source and the resistance of the loads. The follower circuit, on the other hand, comprises a low impedance FET and a follower current source having an active load whose current is primarily dependent on its threshold voltage. Accordingly, process factors which affect the threshold voltage of the low impedance FET also affect the threshold voltage of the active load in a mutually compensatory manner without adversely affecting the output levels of the logic level signals from the current steering circuit.

Patent
25 Dec 1989
TL;DR: In this paper, a voltage/current converter and a differential amplifier are used to process the addition and subtraction at one time by using an emitter negative feedback resistance and differential amplifier set at the output stage of the converter.
Abstract: PURPOSE:To process the addition and the subtraction at one time by using a voltage/current converter containing an emitter negative feedback resistance and a differential amplifier set at the output stage of the voltage/current converter. CONSTITUTION:A voltage/current converter A which converts the input signal voltage into a logarithmic function is provided together with a differential amplifier B having high gains which secures the single output from the output of the converter A. Thus an operational amplifier circuit is obtained. A signal input stage converts the input signal voltage into a differential current via the emitter negative feedback resistances R1 and R2 and supplies the differential current to a diode D2. Then a transistor differential pair is biased with the forward voltage of the diode D2. Thus the single output is obtained. Thus an accurate operation is secured despite a high impedance of a signal source.

Patent
10 Jul 1989
TL;DR: In this article, a ringing choke converter power supply device consisting of an indirect feedback system, a variable impedance element provided on a primary or secondary side of the power supply, and a control circuit for transmitting a control signal to the variable impedance elements in such a direction that an error signal obtained by comparing the output voltage of a power supply with a predetermined reference voltage becomes zero.
Abstract: A ringing choke converter power supply device comprising a ringing choke converter power supply for stabilizing an output voltage by an indirect feedback system; a variable impedance element provided on a primary or secondary side of the power supply; and a control circuit for transmitting a control signal to the variable impedance element in such a direction that an error signal obtained by comparing the output voltage of the power supply with a predetermined reference voltage becomes zero. The variable impedance element, which is preferably a saturable reactor, is interposed between a voltage detection winding and a feedback diode or between the feedback diode and a capacitor when the element is provided on the primary side; and is interposed between a transformer secondary winding and a rectifier circuit, when the element is provided on the secondary side.

Patent
26 Jun 1989
TL;DR: In this article, the authors proposed a method to prevent an output terminal voltage of a generator from decreasing and to efficiently control an effective power by calculating a torque current set value and a magnetic flux current set values.
Abstract: PURPOSE: To prevent an output terminal voltage of a generator from decreasing and to efficiently control an effective power by so calculating a torque current set value and a magnetic flux current set value that the output voltage of a synchronous generator becomes constant, and controlling a forward converter from the calculated values. CONSTITUTION: A lead current to lag current are freely regulated by using a converter formed of a GTO thyristor, etc., as a forward converter 2 connected to a permanent magnet type synchronous generator 1, the current to be output from the generator 1 is divided into a torque current component proportional to the effective power and a magnetic flux current component proportional to a terminal voltage by a controller 4 by using a polar coordinates conversion theory to be controlled. Accordingly, the output terminal voltages of the generator 1 can be controlled constantly. Thus, if the load of the generator 1 is increased, it can prevent the terminal voltage from decreasing. The effective power and the terminal voltage can be regulated at a high speed. COPYRIGHT: (C)1991,JPO&Japio