US2698416A - Voltage regulator - Google Patents

Description

Dec. 28, 1954 s. sHERR VOLTAGE REGULATOR Filed March 9, 1954 IN V EN TOR. SOLOMON SHEER BY W ATTO NEY \7 VOLTAGE souzc:

United States Patent Ofiice 2,698,416 Patented Dec. 28, 1954 VOLTAGE REGULATOR Solomon Sherr, Tuckahoe, N. Y., assignor to General Precision Laboratory Incorporated, a corporation of New York Appiication March 9, 1954, Serial No. 414,957

13 Claims. (Cl. 32322) This invention relates to direct-current power supplies providing regulated output voltages. Such a supply usually comprises an alternating current source, a rectifier, and filter, with an electronic device for maintaining constant output voltage.

One form of regulating device employed in such a supply includes a sensitive control element such as an electronic tube in series with the output terminals, and an amplifier sensitive to the output potential for controlling the sensitive control element. In addition a reference potential is employed such as the potental drop across a voltage regulator tube, and it may be shown that some sort of reference potential is required in every voltage regulator of this kind.

One purpose of voltage regulation is to keep the power supply output voltage constant. This function of regulation, constancy of output voltage, can be defined as the variation of output voltage divided by the nominal or full-load output voltage. Alternatively the input volttage or its change may be the denominator. That is:

dE Regulatwn dB (2) in which E1 is the input voltage.

The smaller the value of the fraction the better the voltage regulation is said to be. Either load current change or input voltage change may tend to change the output voltage. The present invention reduces or substantially eliminates changes in output voltage due to either cause.

It is conventional in a power supply of the type under consideration to employ a high vacuum electronic tube in series with the load, and to apply the regulatory effort to the control grid of this tube. However, obviously any device which controls electrical power by the application of smaller power may be employed, among such devices being transistors, saturable reactors, and amplidynes. It is also conventional in such power supplies to employ an electronic tube negative feed back amplifier. However it is obvious that in place of the electronic tube amplifier a transistor amplifier may be employed with appropriate changes in connections. The instant invention is concerned with the reference voltage required in the voltage regulator. In place of any of the conventional forms of reference voltage the instant invention employs a reference voltage depending on a voltage or current inherently generated within the feedback amplifier. The magnitude of this inherent voltage or current is completely or substantially independent of the magnitudes of all externally applied voltages excepting, in the case of electronic tube amplifiers, of the filament voltage. In general, the magnitude of the inherent voltage or current is dependent only upon the materials employed in the construction of the electronic tube or of the transistor.

The inherent voltage in the case of an electronic tube amplifier may be designated as the initial cathode potential and termed e. This potential is the sum of the initial velocity potential, vi, due to thermal escape of electrons from the cathode, and of the contact potential, Vcp, which is in turn dependent upon the work function of the material of which the cathode is made. That is,

ticular transistor.

The inherent voltage 2 is made to produce a current drop across this resistor which is ence voltage V.

In the case of transistors it is simpler to consider currents rather than voltages, and the inherent current employed to generate the reference voltage is described as the collector cutofi current, Inn. This current is that which flows in the collector circuit when the emitter current is zero, and is the result of an inherent property of the par- The inherent current is made to flow through a fixed resistor, and it is the resulting voltage drop across this resistor which is employed as the reference voltage V0 in the transistor embodiment of this invention.

The general purpose of this invention is to provide a regulated power supply including a feedback amplifier containing an inherent electrical magnitude which serves to generate a reference magnitude.

Another purpose of this invention is to provide a regulated power supply including an electronic tube feedback amplifier having an inherent initial cathode potential, of which the reference potential is a function.

employed as the refer- Another purpose of this invention is to provide a regulated power supply including a transistor feedback amplifier having an inherent collector cutoff current, of which the reference potential is a function.

A further understanding of this invention may be secured from the detailed description and drawings, in which:

Figure 1 depicts a regulated voltage supply employing electronic tubes and embodying this invention.

Figures 2 and 3 depict a voltage regulator employing a transistor feedback amplifier.

Figure 4 depicts a transistor voltage regulator employing a series transistor as the sensitive control element.

Referring now to Fig. 1, a source of voltage 11 in cludes a rectifier energized by alternating current, and emits filtered direct current having a potential E. This potential is applied to the voltage regulator input conductors 12 and 13, conductor 12 being positive. Conductor 12 is connected through a series triode 14 to conductor 16 and thence to the regulated power supply output terminal 17, while conductor 13 is connected directly to the other output terminal 18. A voltage divider 19 and resistor 21 are placed in series across output terminals 17 and 18, so that a desired fraction of the output voltage E0 appears at the voltage divider slider 22 in accordance with its manual adjustment. This voltage divider 19 provides means for manually adjusting the output voltage E0 and also acts to correct for changes in output voltage when replacing tubes, caused by differences in individual tube characteristics.

The plate 23 of a triode 24 is connected to the positive regulated conductor 16, while its grid 26 and cathode 27 are connected to slider 22. The plate 28 of a triode amplifier 29 is connected to the positive conductor 16 through-a resistor 31, and the cathode 32 is connected to slider 22. Grid 33 is grounded" to conductor 13. The output from plate 28 is coupled through resistor 34 to the control grid 36 of an amplifier-inverter pentode 37. The cathode 38 of pentode 37 is connected to the slider 39 of a voltage divider 41 for adjustment of bias voltage and plate current. The plate 42 is connected through resistor 43 to the positive conductor 16. The output derived from the plate 42 is applied to the control grid 46 of triode 14 through conductor 44.

In the operation of this circuit, changes of the potential of output terminal 17 relative to terminal 18, whether due to changes in load current or to changes in input voltage, change the potential at the slider 22. This potential change is amplified in triode 29, amplified and inverted in pentode 37, and applied to the control grid 46 of triode 14 in such sense that the voltage drop through of the voltagedrop Ed across the resistor 31 having resistance R which is due to e. That is:

in which lb is'the plate current of tube 29 and is a function of e. This is conventionally expressed as in which Eb is the plate potential, ,0. is the amplification constant and EclS the grid-cathode potential. The plate current lb thus is due to three causes, and that part due to the-initial cathode potential e may be termed la. It is the potential drop V in theplate resistor 31 due to la, which is-employed as the reference potential in this circuit. That V=IeR The quantity e has the magnitude of a volt or so. Although this is small compared to usual values of plate voltage, it is found that this fixed primary reference po tential is large enough tolserve as the' source of a reference voltage V in highly practical voltage'regulators.

The cathode of pentode ,37 of course generates an initial cathode potential, but since it is in the second stage of amplification its effect is negligible. The function of this tube is principally to invert the signal, an even number of stages being necessary to apply the signal to the sensitive control tube 14in the right sense for regulation of the output voltage.

The contact potential, Vcp, being dependent on the work function of the material of the cathode 32, is highly dependent on the cathode temperature. It is therefore desirable, in order to stabilize V, to secure constancy of Vcp and therefore of e. In order to secure constancy of the contact potential Vcp in spite of fluctuations of filament voltage and other causes of temperature variation the triode 24 is employed.

' In the operation the filament correction triode 24, is adjusted so that its plate current is considerably higher than the plate current of triode29, and causes a selected potential drop in voltage divider 19 between slider 22 and conductor 13. If for any reason, suchas by increase of filament current, the cathode 32 should increase in temperature, its potential will become more negative. But since cathode 27 is heated by the same filament circuit its potential will also decrease and triode 24 will draw more current. The resulting increased potential drop through the lower part of voltage divider 19 will then, raise the potential of cathode 32 to neutralize the change made by the temperature change. If the temperature of cathode 32 should decrease, the reverse effects will neutralize itstendency to increase in potential.

Instead of returning the control grid 26 to the slider 22, it'may be found desirable to return it to some other point on the voltage divider 19, depending on the relations between the characteristics of the particular tubes employed as triodes 24 and 29.

The principles of this invention are embodied in the circuit of Fig. 2, in which unregulated filtered direct-current potential E1 is applied to input terminals 47 and 48. A triode 49 in series with input terminal 47 and output terminal 51 is employed as the sensitive control element, and input terminal 48 is connected to output terminal 52'. A voltage divider 3 and resistor 54in series across tthe output terminals 51 and 52 reduce the output potential E0 to a fraction suitable for feeding back to the sensitive control element 49, and provide means of adjustment. The negative feedback voltage amplifier is an n-p-n junctionjtransistor 56 connected as a grounded or common emitter amplifier. One input is connected from slider 57 of'v'oltage' divider 53 to the base terminal 58 and the other input is through conductor 59 to the emitter terminal '61.' Positive potential is applied to the collector terminal 62 through the collector resistor 63, and output potential is taken from the collector terminal and applied through conductor 64 to thecontrol grid 66 of triode 49.

It is a property of transistors that a small current called the collector cutoff current, 100, flows when the emitter current is zero. This collector cutolf current can be thought of as flowing at all times in addition to other collector currents which flow in accordance with input and output circuit potentials. The collector cutoff current magnitude is nearly independent of all applied potentials, and is ernployed in this circuit as the source of the reference p'otentiali The collector cutoff current, flowing through the resistor 63, causes a potential drop Vc therein. It is this potential drop which is employed in this. circuit as the reference potential, existing at all times as a part of the potential applied to control grid 66.

In operation, if the output potential E0 should decrease, the emitter-to-base potential of transistor 56 is decreased. This causes the collector current to decrease, reducing the potential drop in resistor 63 and making control grid 66 less negative. The voltage drop across triode 49 is thereby decreased, neutralizing the drop in output potential. If the output potential EU should tend to increase the reverse action ensues, against neutralizing the change in output voltage.

The reference potential dependent upon the collector cutoff current is small, so that in some cases one feedback transistor amplifier is not sutficient to provide good regulation. In such cases more than one stage of feedback amplification may be used, an odd number of stages being required if all transistors are of the same type or an even number if they are alternately of the n-p-n and p-n-p types. Fig. 3 illustrates the latter situation.

In Fig. 3 the input terminals 47 and 48 are connected to the output terminals 51 and 52 through series triode 49 as in Fig. 2, and the voltage divider 53 and resistor 54 reduce the feedback signal. A p-n-p junction transistor 67 has its base terminal 68 connected to the slider 69 of voltage divider 53. The collector 71 is connected through a collector resistor 72 to output terminal 52 and the emitter 73 is connected to output terminal 51. The output potential taken from the collector 71 contains not only the amplified signal applied to the base but also the reference potential consisting of the potential drop in resistor 72 due to the collector cutoff current. This output potential is applied to the base terminal 74 of an n-p-n junction transistor 76 having its collector 77 connected to output terminal 51 through resistor 78 and its emitter 79 connected directly to output terminal 52. Connection is made between collector 77 and the control grid 81 of triode 49.

A transistor may be substituted for the series triode employed in Figs. 1, 2 and 3 as the sensitive control element, and when the series transistor is combined with a transistor feedback amplifier a voltage regulator employing only transistors results. Such a regulator is depicted in Fig. 4. The input terminals 47 and 48 are connected to the output terminals 51 and 52 in series with an n-p-n junctiontransistor 82, the collector 83 being connected to terminal 47 and the emitter 84 being connected to output terminal 51. An n-p-n transistor 86 serves as'the negative feedback amplifier, its base 87 being connected to the slider 88 of voltage divider 89. Its emitter 91 is connected to output terminal 52 and its collector 92 is connected through collector resistor 93'to the positive input terminal 47. Connection of this resistor to the input terminal instead of to the output terminal 51 is preferable because the potential between base and emitter of transistor 82 is very low, which would necessitate a small value of collector resistor. By connecting the collector resistor to the collector 83 a large value of resistance can be employed resulting in greater amplification and better regulation.

What is claimed is:

1. A voltage-regulated power supply comprising, a

source of direct-current potential, a load circuit connected to said source, a control device having a control electrode for controlling an electrical quantity existing between a pair of other electrodes, one of said pair of electrodes being connected to said source and the other of said pair of electrodes being connected to said load circuit, an amplifying device, a source of fixed primary reference potential, said source being an inherent part of said amplifying device, an impedance connected in series with said amplifier and a source of potential for developing a potential drop in said impedance a portion of which results from the application of said fixed primary reference potential, said portion of potential drop constituting the reference potential utilized by the said power supply, means for applying a potential to said amplifying device proportional to the potential applied to said load circuit, and means for applyingthe potential of said impedance to the control electrode of said control device.

2. A voltage-regulated power supply comprising, a source of direct-current potential, a load circuit connected to said source, a control transducer having several electrodes including a controlelectrode for controlling an electrical quantity existing between a pair of other electrodes, said pair of electrodes being interposed in series between said source and sail load, an electrical amplifying device having at least one stage generating a fixed inherent electrical quantity, an impedance connected in series with said stage and a source of direct current whereby a potential drop is developed in said impedance which is dependent on said fixed inherent electrical quantity, the portion of said potential drop due to said fixed inherent electrical quantity constituting the reference potential of said power supply, voltage-dividing resistor means for applying a potential to said stage proportional to the potential existing across said load circuit, and means for applying the potential existing across said impedance to the control electrode of said control transducer.

A voltage-regulated power supply comprising, a source .of direct-current potential, a load circuit connected to said source, an electronic discharge tube having at least a grid, cathode and anode, said cathode and anode being interposed in series between said source and said load, an electrical amplifying device having at least one stage generating a fixed inherent electrical quantity, an impedance connected in series with said stage and a source of direct current whereby a potential drop is developed in said impedance which is dependent on said fixed inherent electrical quantity, the portion of said potential drop due to said fixed inherent electrical quantity constituting the reference potential of said power supply, voltage-dividing resistor means for applying a potential to said stage proportional to the potential existing across said load circuit, and means for controlling said grid by the potential existing across said impedance, the sense of control being such as to tend to maintain constant potential across said load circuit.

4. A voltage-regulated power supply comprising, a source of direct-current potential, a load circuit connected to said source, an electronic discharge tube having at least a grid, cathode and anode, said cathode and anode being interposed in series between said source and said load, the anode being more positive than the cathode, an electronic amplifier stage including discharge tube means having at least a grid, cathode and anode, a source of fixed primary reference potential, said source of fixed primary reference potential being an inherent part of the electronic discharge tube means of said amplifier stage, an impedance connected in series with said electronic discharge tube means and a source of direct current for developing a potential drop in said impedance which is dependent in par-t on said fixed primary reference potential, that potential drop due to said fixed primary reference potential constituting the reference potential of said power supply, voltagedividing resistor means for applying a potential to said amplifier stage proportional to the potential existing across said load circuit, and means for applying the potential of said impedance to the grid of said electronic discharge tube in such sense as to tend to maintain constant potential across said load circuit.

5. A voltage-regulated power supply comprising, a source of direct-current potential, a load circuit connected to said source, a control transducer having several electrodes including a control electrode for controlling an electrical quantity existing between a pair of other electrodes, said pair of electrodes being interposed in series between said source and said load, an electronic amplifier stage including discharge tube means having at least a grid, cathode and anode, said discharge tube means generating a fixed inherent potential, an impedance connected in series with said stage and a source of direct current for developing a potential drop in said impedance which is dependent in part on said fixed inherent poten tial, that portion of said potential drop due to said fixed inherent potential constituting the reference potential of said power supply, voltage-dividing resistor means for applying a potential to said stage proportional to the potential existing across said load circuit, and means for applying the potential across said impedance to the control electrode of said control transducer is such sense as to tend to maintain constant potential across said load circuit.

6. A voltage-regulated power supply comprising, a source of direct-current potential, a load circuit connected to said source, an electronic discharge tube having at least a grid, cathode and anode, said cathode and anode being interposed in series between said source and said load, the anode being more positive than the cathode, an electronic amplifier stage including discharge tube means having at least a grid, cathode and anode, a source of fixed primary reference potential, said source of fixed primary reference potential being an inherent part of the electronic discharge tube means of said amplifier stage, an impedance connected in series with said discharge tube means and a source of direct current for developing a potential drop in said impedance which is dependent in part on said fixed primary reference potential, that portion of said potential drop due to said fixed primary reference potential constituting the reference potential of said power supply, a triode discharge tube having anode, cathode and control grid, a circuit interconnecting the anode of said triode and said last-named source of direct current, the cathode of said triode and said discharge tube means being connected together and the control grid of said triode being connected to said cathodes whereby changes in the temperature of the cathode of said discharge tube means which tend to vary said fixed primary reference potential are compensated by equal but opposite variations due to similar temperature changes in said triode, voltage-dividing resistor means for applying a potential to said amplifier stage proportional to the potential existing across said load circuit, and means for applying the potential of said impedance to the grid of said electronic discharge tube in such sense as to tend to maintain constant potential across said load circuit.

7. A voltage-regulated power supply comprising, a source of direct-current potential, a load circuit connected to said source, a control transducer having several electrodes including a control electrode for controlling an electrical quantity existing between a pair of other electrodes, said pair of other electrodes being interposed in series between said source and said load circuit, a transistor amplifier stage including a transistor having at least three electrodes, said transistor generating a fixed inherent collector cutoff current, an impedance connected in series with said stage and a source of direct current for developing a potential drop in said impedance which is dependent in part on said collector cutoff current, that portion of said potential drop due to said fixed inherent collector cutoff current constituting the reference potential of said power supply, voltage-dividing resistor means for applying a potential to said stage proportional to the potential existing across said load circuit, and means for applying a potential in accordance with the potential across said impedance to the control electrode of said control transducer in such sense as to tend to maintain constant potential across said load circuit.

8. A voltage-regulated power supply comprising, a source of direct-current potential, a load circuit connected to said source, an electronic discharge tube having at least a grid, cathode and anode, said cathode and anode being interposed in series between said source and said load, the anode being more positive than the cathode, a transistor amplifier stage including a transistor having at least three electrodes, said transistor generating a fixed inherent collector cutoff current, an impedance connected in series with said stage and a source of direct current for developing a potential drop in said impedance which is dependent in part on said collector cutoif current, that portion of said potential drop due to said fixed inherent collector cutoff current constituting the reference potential of said power supply, voltage-dividing resistor means for applying a potential to said stage proportional to the potential existing across said load circuit, and means for applying a potential in accordance with the potential across said impedance to the grid of said electronic discharge tube in such sense as to tend to maintain constant potential across said load circuit.

9. A voltage-regulated power supply comprising, a source of direct-current potential, a load circuit connected to said source, a triode discharge tube having grid, cathode and anode electrodes, said anode being connected to the positive terminal of said source and said cathode being connected to said load circuit to interpose the anode-cathode circuit of said triode in series with said source and said loadcircuit, a transistor amplifier stage including a transistor having emitter, collector and base electrodes, said transistor generating a fixed inherent collector cutoif current having a specific value for a selected collector bias potential when the emitter current is zero, a resistor connected between the collector of said transistor and a source of direct current for developing a potential drop therein which is dependent in part on said collector cutoff current, that portion of said potential drop due to said collector cutoff current constituting the reference potential of said power supply, a resistive voltage divider having terminals connected across the input terminals of said load circuit, a connection from the slider of said voltage divider to the base electrode of said transistor for applying a potential thereto proportional to the potential applied to said load circuit, and means for applying a potential representing the potential drop across said resistor to the grid of said triode discharge tube in such sense as to modify its anode-cathode current in such direction and amount as to tend to neutralize changes in load circuit potential due either to changes in load or to changes in the potential of said source of direct-current potential.

10. A voltage-regulated power supply in accordance with claim 9 in which said transistor is of the n-p-n type having a common emitter circuit, in which said source of direct current is the positive input terminal of said load circuit and in which said last-named means is a conductive connection from said collector electrode to the grid of said triode.

11. A voltage-regulated power supply in accordance with claim 9 in which said transistor is of the p-n-p type having in a common emitter circuit, inwhich said source of direct current is the negative input terminal of said load circuit and in which said last-named means is a transistor amplifier containing an odd number of stages.

12. A voltage-regulated power supply comprising, a source of direct-current potential, a load circuit connected to said source, a transistor having collector emitter and base electrodes, two of said electrodes being interposed in series between said source and said load and the third of said electrodes serving as a control electrode to control the passage of currrent between the first two electrodes, an electrical amplifying device having at least one stage generating a fixed inherent electrical quantity, an impedance connected in series with said stage and a source of direct current for developing a potential drop in said impedance which is dependent in part on inherent electrical quantity, the portion of said potential drop due to said fixed inherent electrical quantity constituting the reference potential of said power supply, voltage-dividing resistor means for applying a potential to said stage proportional to the potential existing across said load circuit, and means for applying a potential representing .the potential across said impedance to the control electrode of said transistor in such polarity as to control the transistor current in such sense and magnitude as substantially to neutralize changes in potential across said load whether dueto changes of load or change of potential of said source of direct-current potential.

13. A voltage-regulated power supply comprising, a source of direct-current potential, a load circuit connected to said source, an n-p-n series transistor having collector, emitter and base electrodes, said collector electrode being connected to the positive terminal of said source of direct-current potential and said emitter electrode being connected to said load interposing the transistor in series between source and load, an amplifying n-p-n transistor having emitter, collector and base electrodes, said amplifying transistor generating a fixed inherent collector cutoff current having a specific value'for a selected collector bias potential, a resistor connected between the collector of said amplifying transistor'and the positive terminal of said source of direct-current potential for developing a potential drop therein which is dependent in part on said fixed inherent collector cutoff current, that portion of said potential drop dueto said collector cutoff current constituting the reference potential of said power supply, the emitter terrninal'of said amplifying transistor being connected to the negative terminal of said source of direct-current potential, a resistive voltage divider connected across the input terminals of said load circuit, a connection from a silder adjustably positioned on said voltage divider to the base electrode of said transistor for applying a potential proportional to that applied to said load circuit, and means for applying a potential representing the potential, drop across said resistor to the base electrode of said series transistor, the applied potential being in such sense as to control the current of said series transistor to' neutralize changes in load circuit potential; I

No references cited.

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