US2912637A - Electronic voltage regulator - Google Patents

Description

NOV 10, 1959 G. H. BARNES ErAL 2,912,637

ELECTRONIC VOLTAGE REGULATOR 2 Sheets-Sheet 1 Filed Sept. 50, 1957 ERL ONEU Y TRYH NAEC N WBMS R O NHJ.A T 1 n ELE GAM

+I EMITTERS OF F/Q-3 IIC) TRANSISTORSOeII I I Nov. 10, 1959 G. H.BARNEs ETAL 2,912,637

ELECTRONIC VOLTAGE REGULATOR Filed Sept. 30, 1957 2 Sheets-Sheet 2 G) BASE OF T V- I TRANSISTOR 5o b) BASE OF I I TRANSISTOR 5I I I I PHASE DETECTOR JFI (dI OUTPUTIUNFILTEREDI (e) CONTROL VOLTAGE I I I (G) BASE OF TRANSISTOR 50 TRANSISTOR 5I C EMITTERS OF I I TRANSISTORSSOSSI I I L I (d PHASE DETECTOR I I OLITPIITIIINPILTERED) (e) CONTROL VOLTAGE o kG) BASE OF TRANSISTOR 50 1 I (b) BASE OF TRASISTOR 5I I EMITTERS OF +I I I I I I F/g, 5 ICI TRANSISTORS 50a5I l I I I I I I +I I I I I I I (d) PHASE DETECTOR o I OUTPLITTUNEILTEREDI I I I I I I I I I +I I I I I I I (e) CONTROL VOLTAGE OI I I v I I I I I k y INVENTORS MIA/ILM I Q ATTORNEY United States Patent ELECTRONIC VOLTAGE REGULATOR George H. Barnes, Berwyn, Albert J. Meyerholf, Wynnewood, and Merle A. Schultz, Berwyn, Pa., assignors to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Application September 30, '1957, Serial No. 687,252 4 Claims. (Cl. 323-22) This invention relates tov power supply systems and more particularly to an improved electronic voltage regulator.

Electronic voltage regulators are most frequently employed with D.C. power supplies in order to maintain a substantially constant output voltage across the load, in spite of large changes of load current drawn from the supply or changes in the input Voltage. These regulators usually take the form of a variable resistance in series or shunt with the output. Since for the series case the Variable resistance and load resistance form a voltage divider, the regulator must control the variable element so that the voltage across the load is held constant. Present day series regulators supply the variable voltage drop in many Ways but such regulators have one characteristic in common, namely, the use of a standard voltage with which the output voltage is compared. The regulation provided by such devices is dependent upon the accuracy and stability of the reference voltage element. In order to achieve such stability over long periods of time, and particularly under environmental conditions, present day regulators utilize complicated circuits which waste space, are ineicient, and ultimately lessen the overall dependability of the system in which they are used.

In accordance with the present invention voltage regulation is achieved without the use of the conventional voltage reference element. Instead, an oscillator, whose frequency is a function of the voltage applied to it, is connected across the load circuit of a D.C. supply. The oscillator frequency signal output is converted into two signal components having a phase difference dependent upon the instantaneous frequency of the oscillator. The two signal components are compared by a phase-sensitive detector which produces a control voltage whose magnitude varies with the oscillator frequency. This control voltage is used to vary the impedance of a series circuit element in such a manner that the Voltage applied to the load circuit remains substantially constant.

Although not limited thereto, a preferred embodiment of the instant invention utilizes solid state electronic devices, namely, transistors and a magnetic core possessing a rectangular hysteresis loop characteristic for accomplishing voltage regulation. The advantages inherent in the solid state components themselves include saving in space, efficiency, dependability, and longevity. Another feature of the instant invention is that the temperature characteristic of the device may be accurately predicted and easily modified if necessary to compensate for the temperature characteristic of the load circuits with which it is associated. This is especially advantageous when extreme accuracy is desired from simple load circuits which have not been temperature stabilized. Where the additional space and weight required by temperature compensating circuits cannot be tolerated, as in telemetering applications, the instant voltage regulator is particularly useful.

Accordingly it is an object of the instant invention to provide an improved electronic voltage regulator whose operation is based upon a signal frequency rather than the conventional voltage reference element.

A more specific object of this invention is to provide an efficient and dependable voltage regulator utilizing solid state electronic components.

A further object of this invention is to provide a voltage regulator whose operational characteristics under environmental conditions can be adjusted to suit the requirements of the load.

Fig. l is a block diagram illustrating the mode of operation of the instant invention;

Fig. 2 is a schematic diagram illustrating a preferred embodiment of the instant invention;

Fig. 3 shows a diagrammatic representation of the voltage pulses appearing at various points in the phase detector circuit when the load voltage is less than the design voltage;

Fig. 4 depicts the voltage pulses appearing in the detector circuit when the load voltage is correct;

Fig. 5 shows the voltage pulses appearing at various points in the detector circuit when the load voltage is higher than the design voltage.

In the embodiment of Fig. 2 the binary magnetic storage element is shown as a circle and it is assumed that this circle represents a magnetic core having an essentially rectangular hysteresis loop. Although the magnetic element is depicted herein as being toroidal in form, it is understood that the invention is not limited to elements of this particular geometry, but may include other forms of magnetic storage elements. The transistor elements depicted in Fig. 2 are junction PNP-type but, likewise, the invention is not restricted to the use of this type of transistor, but may employ other types in accordance with established design procedures well known to those skilled in the art.

In an embodiment of the instant invention, as illustrated bythe block diagram of Fig. l, the D.C. voltage produced in power supply A is coupled via series impedance element B to the parallel combination of oscillator C and the load circuit L. Oscillator C generates a signal voltage whose frequency is dependent upon the voltage across said parallel combination. A lirst portion of the oscillator output signal is fed directly to a phase-sensitive detector D. A second portion of the signal is shifted in phase by network E, reshaped and clipped by limiter F, and is also fed to the phase-sensitive detector D. The function of the detector is to compare the phase of the first signal with that of the second and thereby to produce a control voltage whose amplitude and polarity varies in accordance with the oscillator frequency and the Voltage across the load. This control voltage is fed to `amplifier G which functions in a manner to vary the impedance of series element B. As the impedance of element B varies in response to the control voltage, the voltage drop across element B varies proportionately, land the voltage across the load is thereby adjusted to the desired value. The reference letters employed in Fig. l Will be used in conjunction with Fig. 2 to designate like portions of the circuit.

In consideration of Fig. 2 there is shown an embodiment of the invention comprising a square wave oscillator C having a magnetic storage element 20, collector windings 22, 24, and output windings 23, 25 and 27, coupled to said magnetic element, transistors 30 and 31, and two parallel resistance- capacitance networks 32 and 34. Such an oscillator circuit employing solid state electronic components is described and claimed by Robert M. Tillman in copending application Serial No. 636,740, filed January 28, 1957, and has been assigned to the assignee of the instant application. Power is supplied to the oscillator circuit via current limiting resistor 72 and transistor 70 by a rectifier-type power supply A. The switching of Patented Nov. 10, 1959l Vmagnetic element from one of its magnetic remanent states to the other, as hereinafter described, induces a voltage in output windings 23, and Z7. The signal voltage induced in winding-27 is shifted in phase by a network comprising an inductor 86 and capacitor 85, and is applied via coupling resistor 42 to the base electrode of transistor 4t). Transistor 4l) limits the amplitude of the phase-shifted signal. In order to detect differences in the phase of signals applied to it, a phase-sensitive detector comprising transistors 5u and 51, capacitor 55 and load resistors 52 and 53 is employed. The phase-shifted output of transistor 4G developed across collector load resistance 44 is fed to the emitter electrodes of transistors 50 and 51. The signal voltages induced in windings 23 and 25 during the switching of magnetic core 20l are coupled via resistors 56 and 57 to the base electrodes of transistors 50 and 5l respectively. The collector supply voltage, V, is preferably a negative potential independent from that available directly Yfrom power supply A. In actual practice, a second oscillator of the type hereinbefore described may be connected across the supply voltage and its output rectified and filtered to provide a relatively well regulated, isolated D.C. collector supply voltage of `any desired magnitude. vCapacitor 55 filters the pulse output of the transistors and provides a D.C. control voltage. This control voltage is amplified by transistor 60 and is fed to transistor 70 which is connected in series with the load resistance 92. Current limiting resistors 62` and 74 are included in the base circuits of transistors 6% and 70 respectively. The application of the control voltage to transistor 7G varies its series impedance to the flow of the load current, thereby changing its instantaneous voltage drop and automatically compensating for variations in the design load voltage.

Although the oscillator C depicted in Fig. 2 is described in detail in the aforementioned Tillman application, a brief explanation of the operation of this oscillator follows. The output frequency of the oscillator C is a function of the D.C. voltage appearing across its terminals 36 and 37, and likewise across the load. Assume that initially transistor is On or conducting while transistor 31 is Off or non-conducting. The collector current owing through-winding 22 of the On transistor has switched the magnetic element 20 into a heavily saturated condition. Thus, to keep transistor 30 saturated, or bottomed, increasingly larger current is required from its collector electrode to maintain the feedback flux-linkage between windings 22 and Z4, the voltage induced across winding 24 being applied to the base of transistor Bil through the network 34. A point is reached where the On transistor i can no longer supply the required current. When this occurs the voltage across the On transistor collector winding 2-2 starts to fall. This reduced voltage causes the regenerative base current of transistor 3l) to decrease, which causes an even greater decrease in its collector winding voltage. Very quickly the net voltage at the base of the On transistor 30 goes positive owing to the charge on the capacitor in network 34. This causes inverse base current to flow in transistor 30 and hence a rapid decrease in its collector current. The iiyback of core liuX associated with the decline of collector current in transistor 39 results in a driven ilyback voltage induced in the collector winding 24 of the Off transistor 3l. This iiyback voltage causes the collector of the Off transistor 31 to become positive.

At the same time the base of the Off transistor is negative. The Off transistor therefore becomes saturated in the inverse direction. This inverse conduction of the Otf transistor clamps the flyback voltage to a value very nearly equalV to the supply voltage. By inverse conduction transistor 31 is pre-supplied with holes so that it can take on its load extremely rapidly when transistor 30 shuts off. Once properly started, regeneration will maintain an unbroken waveform and the switching action will be repetitive. The frequency of this switching action, as-

suming the other circuit parameters remain unchanged, will depend upon the voltage applied to the terminals 36 and 37.

Although the oscillator C shown in Fig. 2 is a preferred form, it is understood that any oscillator having a frequency dependent upon voltage may be substituted therefor.

The waveform diagrams of Figs. 3, 4 and 5 illustrate three separate conditions encountered in the regulation process. Referring to the waveform diagrams of Figs. 3, 4 and 5, in combination with the schematic of Fig. 2, the signal voltages appearing on the base electrodes of transistors 50 and 51 as a result of the switching voltages induced in output windings 23 and 25 respectively, are shown in Figs. 3a, 4a, 5a and 3b, 4b and 5b. The output windings 23 and 25 are arranged such that the voltages induced therein are l out of phase with each other. As hereinbefore mentioned the signal voltage induced in output winding 2.7 is shifted in phase by inductor S6 and capacitor 35 which are tuned to resonance at the oscillator frequency corresponding to the design voltage across thev load. This arrangement produces a phase difference between the input voltage pulse applied to the phase shift network and the output signal obtained therefrom when the voltage across the load is at its design value. The output of-the phase shift network is a sinusoidal voltage of considerably greater amplitude than the input square wave pulse. This sinusoidal voltage is applied to transistor dll which is biased such that when the input signal applied to its base electrode goes negative the transistor saturates and its collector voltage approaches that of its emitter electrode; and when the input voltage goes positive the transistor cuts off and the voltage on its collector approaches the collector supply potential, V. The phaseshifted voltage signal which now appears -as a square voltage pulse on the collector of transistor 40 is applied simultaneously to the emitters of both detector transistors Si) and 5l. This signal is shown in Figs. 3c, 4c and 5c. The negative portion of the voltage cycle appearing on the common emitters of transistors 50 and 51 is suticient to bias the transistors cut off in the presence of the signals appearing on their respective bases. However, when the phase-shifted signal on the emitters becomes more positive, the transistor having a base potential which is negative with respect to its emitter is biased to conduction, and the collector potential of such transistor approaches its emitter potential. The output of the detector circuit (before filtering by capacitor 55) is illustrated in Figs. 3d, 4d and 5d. As the oscillator frequency varies directly with deviations in the load voltage from its design value, the degree of phase-shift imparted to the component of oscillator frequency passed through the phaseshift network varies correspondingly. Thus it will be observed that while there is a 90 phase difference between the signals on the emitter and base electrodes of transistors 50 and 51 for an oscillator frequency corresponding to the design load voltage, as depicted in Fig. 4,

` the phase difference for lower or higher oscillator frequencies is other than 90 as depicted in Figs. 3 and 5 respectively. The phase detector output corresponding to these phase differences is filtered by capacitor 55 to produce a DC control voltage shown schematically in Figs. 3e, 4e and 5e, This control voltage is impressed between the base andemitter electrodes of transistor'amplitier 60. As the current drawn by transistor 60 varies in response to the control voltage applied thereto, its emitter to collector impedance also varies. Since transistor 60 is in the base circuit of transistor 70, variations in the impedance of transistor 66 result in changes in the base current of transistor 70. The emitter to collector impedance of transistor 70 varies inversely With its base current. Consequently, the impedance of transistor 70 and the voltage drop thereacross is controlled in such a manner that a lesser or greater proportion of the Voltage available from the Supply appears across the load resistance,l 92.

From the foregoing description of the invention it is evident that the present technique of employing solid state electronic components and a frequency standard in place of the conventional voltage reference results in eicient and dependable voltage regulation. Temperature compensation of the regulator is readily achieved by selecting a phase-shift capacitor 85 having the proper negative temperature coeiiicient for the desired temperature range, or alternately, by controlling the oscillator frequency with thermistors or other temperature sensitive elements. It must be understood that while a preferred embodiment of the present invention has been shown, this embodiment is meant to be illustrative only, and is not limitative of the invention. Many modifications will be suggested to those skilled in the art, and all such variations as are in accord with the principles discussed previously are meant to fall within the scope of the appended claims.

What is claimed is:

1. An electronic voltage regulator for use with a direct current power source in maintaining a substantially constant design voltage across a load circuit comprising: an oscillator for generating oscillations having a frequency which is a function of the voltage applied thereto, said oscillator being connected in parallel across two terminals of said load circuit whereby the same voltage is applied to both said oscillator and said load circuit, said oscillator including a magnetic core having two stable states of magnetic remanence, a first and second switching winding and a plurality of output windings coupled to said magnetic core, each of said windings having two terminals, a rst and second transistor each having a base, a collector and an emitter electrode, one terminal of said first switching winding being connected to the collector electrode of said first transistor and one terminal of said second switching winding being connected to the collector electrode of said second transistor, a first base resistor connecting the collector of said rst transistor to the base of said second transistor, a first capacitor shunting said iirst base resistor, a second base resistor connected between the collector of said second transistor and the base of said rst transistor, a second capacitor shunting said second base resistor, the other terminals of said iirst and second switching windings being connected in common to one of said load circuit terminals, said emitter electrodes being connected in common to the other of said load circuit terminals, the switching of said magnetic core from one remanent state to the other inv ducing oscillation voltages in each of said plurality of output windings coupled thereto; means for deriving from said oscillations a signal shifted in phase from said oscillations by a number of electrical degrees determined by the instantaneous frequency of said oscillator; means for detecting the phase difference between said oscillations and said phase-shifted signal and for producing a control voltage which is =a function of said phase difference; variable impedance means interposed between said power source and said load, means for applying said control voltage to said variable impedance means, said impedance means varying in response to the magnitude of the control voltage applied thereto, such variation in said impedance means resulting in a corresponding change in the voltage drop thereacross so as to allow a lesser or greater proportion of the voltage available from said source to appear across the load.

2. An electronic voltage regulator for use with a direct current power source in maintaining a substantially constant design voltage across a load circuit, comprising; a voltage-controlled, frequency-modulated square-wave oscillator, -said oscillator being connected in parallel across two terminals of said load circuit whereby the same voltage is applied to both said oscillator and said load circuit, said oscillator including a magnetic core capable of assuming bistable states of magnetic remanence, a first and second switching winding and a plurality of output windings coupled to said magnetic core, each of said windings having two terminals, a rst and a second transistor, each transistor having a base, a collector, and an emitter electrode, circuit means connecting the collector of said first transistor to one terminal of said first switching winding, means connecting the collector of said second transistor to one terminal of said second switching winding, the terminal of said first switching winding which is connected to the collector of said first transistor being chosen so that normal collector current flowing through said first Switching winding drives said magnetic core toward one of its stable remanent states, the terminal of said second switching winding which is connected to the collector of said second transistor being chosen so that the normal collector current flowing through said second switching winding drives said magnetic core toward the other of its stable remanent states, a rst resistor-capacitor network connecting the collector of said iirst transistor to the base of said second transistor, a second resistor-capacitor network connecting the collector of said second transistor to the base of said first transistor, the other terminal of said first and second switching windings being connected in common to one of said load circuit terminals, said emitter electrodes being connected in common to the other of said load circuit terminals, the switching of said magnetic core from one remanent state to the other inducing oscillation voltages in each of said plurality of output windings coupled thereto; a phaseshift network tuned to resonance at the oscillator frequency corresponding to said design voltage, means for applying the oscillations induced in one of said plurality of output windings to said phase-shift network, said network deriving frorn said oscillations an output signal voltage shifted in phase from said oscillations by a number of electrical degrees determined by the instantaneous frequency of said oscillator; means for shaping the wave form of said phase-shifted signal; a phase-detector for sensing the phase diierence between said oscillations and said phase-shifted signal and for producing a control voltage corresponding to said phase difference; variable impedance means connected in series with said power source and said load; amplilier means interposed between said phase-detector and said impedance means, means for applying said control voltage to said amplier means, the output of said amplifier means being applied to said impedance means, the instantaneous value of said impedance means being a function of the magnitude of said control voltage, the voltage drop across said variable impedance means resulting from the source current owing therethrough being such as to allow a lesser or greater proportion of the voltage available from the source to appear across the load.

3. An electronic voltage regulator for use with a direct current power source in maintaining a substantially constant design voltage across a load circuit comprising: an oscillator for generating oscillations having a fre quency which is a function of the voltage applied thereto, said oscillator being connected in parallel across two terminals of said load circuit whereby the same voltage is applied to both said oscillator and said load circuit, said oscillator including a magnetic core having two stable states of magnetic remanence, a rst and second switching winding and a plurality of output windings coupled to said magnetic core, each of said windings having two terminals, a rst and second transistor each having a base, a collector and an emitter electrode, one terminal of said iirst switching winding being connected to the collector electrode of said first transistor and one terminal of said second switching winding being connected to the collector electrode of said second transistor, a first base resistor connecting the collector or said first transistor to the base of said `second transistor, a rst capacitor shunting said first base resistor, a second base resistor connected between the collector of said second transistor and the base of said first transistor, a second capacitor shunting said second base resistor, the

' Y other terminals of said first and second switching windings being connected in common to one of said load circuit terminals, said emitter electrodes being connected in common to the other of said load circuit terminals, the switching of said magnetic core from one remanent state to the other inducing oscillation voltages in each of said plurality of output windings coupled thereto, a first and a second of said output windings being connected such that the oscillationrvoltages appearing respectively on one terminal of said latter windings are of opposite polarity, the other terminals of said first and second output windings being connected in common to a suitable reference potential, a third of said output windings coupled to said magnetic core, a phase shift network tuned to resonance at the oscillator frequency corresponding to said design voltage, means for applying the oscillations induced in said third output winding to said phase-shift network, said network deriving from said oscillations an output signal voltage shifted in phase from said oscillation -voltages by a number of electrical degrees determined by the instantaneous frequency of said oscillator; a phase-sensitive detector `comprising a third and fourth transistor each having an input electrode, an output electrode, and a common electrode, means for respectively applying said opposite polarity voltages induced in said first and second output windings to said common electrodes, means for applying the output signal derived from said phase-shift network concurrently toV said input electrodes of said third and fourth transistors, the concurrence of said oscillations and said phase-shifted signals on said common and input electrodes of each of said third and fourth transistors establishing respectively therein an instantaneous bias condition whereby either Asaid third or fourth transistor is made to conduct or is age to said impedance means whereby variations in said impedance means result in a corresponding change in the voltage drop thereacross and allow a lesser or greater proportion of the voltage available from the source to appear across the load.

'4. An electronic voltage regulator for use with a direct current polwer source in maintaining a substantiallyv constant design voltage across a load circuit comprising: a voltage-controlled, frequency-modulated, squarewave oscillator, said oscillator being connected in parallel across two terminals of said load circuit whereby the same voltage is applied `to both said oscillator and said load circuit, said oscillator including a magnetic core capable of assuming bistable states of magnetic remanence, a first and second switching winding and a plurality of output windings coupled to said magnetic core, each of said windings having two terminals, a first and a second transistor, each transistor having a base, a collector, and an emitter electrode, circuit means connecting the collector of said first transistor to one terminal of said first switching winding, means connecting the collector of said second transistor to one terminal of said second switching winding, the terminal of said first switching winding which is connected to the collector of said first transistor being chosen so that normal collector current flowing throughtsaid first switching winding drives said magnetic core toward one of its stable remanent states, the terminal of said second switching winding which is connected to the collector of said second transistor being chosen so that the normal collector current fiowing through said second switching winding drives said magnetic core toward the other of its stable remanent states, a first resistor-capacitor network connecting the collector of said first transistor to the base of said second transistor, a second resistor-capacitor network connecting the collector cf said second transistor tothe base of said first transistor, the other terminal of said first and second switching windings being connected in common to one of said load circuit terminals, said emitter electrodes being connected in common to the other of said load circuit terminals, the switching ofsaid magnetic core from one remanent state to the other inducing oscillation voltages in each of said plurality of output windings coupled thereto, a first and a second of said output wind- V.ings being connected such that the oscillation voltages appearing respectively on one terminal of said latterV windings are of opposite polarity, the other terminals ofV said first and second output rwindings'being connected in common to a suitable reference potential, a third of said output windings coupled to said magnetic core; a phaseshift network tuned to resonance at the oscillator frequency corresponding to said design Voltage, means for applying the oscillations induced in said third output winding to said phase-shift network, said network deriving from said oscillations an output signal shifted in phase from said oscillations by a number of electrical degrees determined by the instantaneous frequency of said' oscillator; a phase-sensitive detector comprising a third and fourth transistor each having an input electrode, an output electrode, and a common electrode, means for respectively applying said opposite polarity voltages induced in said first and second output windings tot said common electrodes, means for applying the output signal derived from said phase-shift Vnetwork concurrently to said input electrodes, the concurrence of said oscillations and said phase-shift signals on said common and input electrodes of each of lsaid third and fourth transistors establishing respectively therein an instantaneous bias condition whereby either said lthird or fourth transistor is made to conduct or is held cutoff, the output signal of said phase-sensitive detector being a function ofthe instantaneous bias condition of each of said third and fourth transistors; filter means connected between the output electrodes of said third and fourth transistors for converting said detector output signal toV a unidirectional control voltage; variable impedance means interposed between said power source and said load; and means for applying said control voltage to said impedance means whereby variations in said impedance means result in a corresponding change in the voltage drop thereacross and allow a lesser or greater proportion of the voltage available from the source to appear across the load.

References Cited in the file of this patent UNlTED STATESL PATENTS Chase June 19, 1956 DNelly et al lan. 14, 1958 OTHER REFERENCES

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