US2824276A

US2824276A - Current control regulator

Info

Publication number: US2824276A
Application number: US505889A
Authority: US
Inventors: Stump Harvey
Original assignee: Hughes Aircraft Co
Current assignee: Raytheon Co
Priority date: 1955-05-04
Filing date: 1955-05-04
Publication date: 1958-02-18
Anticipated expiration: 1975-02-18

Description

Feb. 18, 1958 H. sTuMP 2,824,276

CURRENT CONTROL REGULATOR Filed May 4, 1955 CURRENT i GEN. E /4 r -/z l6 IP 5 [4.1 22 l8 I9 2 LOAD 4 L FIG. 2

u 6 E E E E s 5 \3 VC 1p? i 3 3 =2 2 MILLIAMPERES FIG 3 HARVEY STUMP INVENTOR United Stews P t nt 2,824,276 CURRENT CONTROL REGULATOR Harvey Stump, Conoga Park, CaliL, assignor to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Application May 4, 1955, Serial No. 505,889 8 Claims. (Cl. 323-4) This invention relates generally to electronic regulator circuits and, more particularly, to a self-regulating current source using a transistor as a passive control element.

There are many electronic circuits and systems whose satisfactory operation depends upon the current supply being maintained constant at all times. The operating conditions of these circuits are generally such that erratic and unpredictable changes in load impedance and supply voltages may occur.

Regulator circuits of various classes have been developed to meet this requirement. Among these classes are the amperite current regulator or ballast tube which employs a metal filament operated in a vacuum or inert gas at an elevated temperature. This type of regulator depends on heating or cooling of the filament as current flows therethrough to change its resistance and thus provide an error signal This introduces an inherent time lag which may be of the order of magnitude of several seconds, depending on the construction of the ballast tube. As the ballast tubes age, changes occur in their operating characteristics. They must therefore be operated, that is, aged for some time prior to'their use in a circuit in order to stabilize their characteristics.

Other types of current regulators of this class utilize thyrite, which is a material made by General Electric Corporation and composed of silicon carbide with a ceramicbinding component; and thermistors, which are made by Western Electric Corporation and composed of a mixture of metallic oxides with a binding component. Th'yrife has the serious limitation of a high temperature coetficient. If constant voltage is applied, current through the thyrite increases 1 percent per degree centigrade. The thermistor depends upon power dissipated within the element to raise its temperature and lower its resistance for its regulatory operation and thus also introduces a time-lag in regulation.

A class of regulators including vacuum tubes, particularly of the pentode type, are frequently used as constant current sources. However, to obtain the benefits inherent in a pentode, that is, a small change in plate current with changes in plate voltage, the screen grid must be connected to a well-regulated constant voltage source.

Accordingly, it is an object of the present invention to provide a current regulator which automatically supplies a constant current to its load irrespective of changes in supply voltage or the load impedance.

Another object of the present invention is to provide a self-regulating current source which reacts to correct any change in the desired output current with substantially zero lag in time.

A self-regulating. current source in accordance with the present invention comprises a current generator and a transistor, including an emitter, a collector, and a base. The transistor is connected between the current generator and a load impedance device. The normal operating potentialsare applied to the current generator and the to be used for regulating purposes.

2,824,276 Patented Feb. 18, 1958 transistor. A quiescent or normal operating point of the transistor is established by passing a predetermined current through the emitter of the transistor. Thereafter, any change in load impedance will tend to cause a change in current flowing through the load and the transistor. This, in turn, causes a change in voltage across the transistor which is applied to the current generator as an error signal. The error signal causes the current generator to correct for the changed impedance by returning the current flowing through the load to its normal operating level.

The novel features of the present invention are set forth in particularity in the appended claims. Other and more specific objects of the invention will become apparent from a consideration of the following description taken in connection with the accompanying drawing, illustrating embodiments of the invention in which:

Fig. 1 is a schematic circuit diagram partly in block form of the current source of the present invention;

Fig. 2 is a schematic circuit diagram of the preferred embodiment of the current source of the present invention;

Fig. 3 is a graph illustrating the characteristic curves of the transistor used in the circuit of the present invention; and

Fig. 4 is a graph illustrating the characteristic curve of the vacuum tube used in the current source of the present invention.

Referring now to the drawing wherein like components are designated by the same reference character and, more particularly, to Fig. 1, there is shown a current generator epresented by rectangle 11 including an input electrode 12, an output electrode 13, and a control electrode 14. A transistor 16 is represented by its accepted schematic symbol and includes an emitter electrode 18, a collector electrode 17, and a base electrode 19. Transistor 16 may be an N-P-N junction type transistor or a point contact transistor having a P-type semiconductive body as indicated by the transistor symbol. Collector 17 is connected to current generator 11 to provide a path for the flow of load current. A load impedance device which is represented by rectangle 24 is connected between emitter 18 and ground. Emitter 18 is also connected to current generator 11 to provide a signal path for the control of load current. 'An adjustable impedance device,'such as resistor 22, is connected to emitter 18, and a source of biasing potential, such as battery 23 has its negative terminal connected to resistor 22 and its positive terminal to base 19. This provides a path for control current to flowthrough transistor 16. Battery 23 is used to bias'emitter 18 in a conducting polarity, while resistor 22 regulates.

the amount of current flowing through transistor 16from base to emitter.

In discussing the operation of the circuit of Fig. 1, reference will be made to Fig. 3 wherein the abscissa represents collector current I in milliamperes (ma.) and the ordinate represents collector voltage V in volts. This family, of curves was taken by establishing emitter current i varying collector voltage in steps and reading" collector current at each step. I in quiescent condition resistor 22 is adjusted so that transistor 16 is operating on its desired curve such as, for

example, that curve 55 of Fig. 3 represented by-emitter current I =2 ma. Assuming then that load 24 is at its optimum value and is stable, that is, not changing at this point, a normal operating value of current is established. This, in turn, establishes the exact operating point of transistor 16 as, for example, point A of curve55. If

then load 24 were to change such as to cause the current flowing through the load to increase, the current flowing through current generator 11 and transistor 16 from emit-- ter to collector will also change. The current flowing;

3 through'transistor 16 will tend to increase toward point BI change in current through transistor 16 is rep resented at 51 in Fig. 3. This increase in current flowing throughtransistor. 16. will cause a,.variation involtage from point Alto. point .B :.a..C1'.OSS..COH6CtOl'- L7 andemitter 1.8,. theerni-tterbeing. negative: with. YESPEiCtzlZO the collector andis representedlat .52 on Big; 3, This change iHiVOltage. is applied. as an .erronsignalto. current generator 11,- the polarity. beingrsuch as totdecrease current flowing throughthe .current generator.. Thiscauses the current to. return .to. its normaLoperating point A..

If loadimpedance, 24-0hanged; such-.as-todecreasev current, fiowingtherethroughras, forexample, along-curve 55v towards pointC, thetcurrent .flowing -fromemitter. to collector. throughtransistor. 16. will .also decrease. This, inin..turn, will cause.,a decrease.in=the voltage drop across the:ernitter,to collectorof thetransistoras representedrat 53 onFig 3. This voltageissuch as to cause. an increase in current flow through. current generator '11. This causes the currentzflowing through the. load to return to -its-normal positionasrepresented at point A of Fig. 3.

It can be seen then. that there: are two paths forcurrent flow through transistor 16. The first path includes the emitter and base electrodes, resistor 22, and battery;23, which establishes the particular .curve of operation: for the transistor, such as curve 55. Thesecond-path includes collector 17, current generator 11, through ground to load-24,- andi'emitter 18.. Current flowingthrough this pathestablishesstheedesiredoperating pointon the selected characteristic curve of transistor 16, such as: point A- on curve -55.' a

It is thus seen that transistor 16is usedas apassive circuit element. Thedynamic collector impedance, that is, the change .in. voltage across the transistorwhich occurs in. responseto a: change in. current gtherethrough, is utilized to supply the error signal for regulatory operation: It is {tov be:noted that aavery small change in current through transistor; 16,.such as-:51,. produces. alarge-change in voltage'across it,-,sucl1*:as:52, thus giving: relatively large triode 31', including-a"cathode-32,: a.:control: 'gridr33, and

an'anode 34. The current generator 11 ofithisffigurexalso includes an input electrode-12', an output electrode 13 and a-control'electrode 14'. A source-of'plate supply voltage such as :battery 35 is connectedbetween-anode 34 and ground. A transistor41, including an emitter .43, acollector 42, and a base 44,.isshown by its accepted schematic symbol and may be either a P N-P junction transistor or a point contact transistor having an N-typev semiconductive body asindicated by the symbol. Base 44 is connected to cathode 32 while collector 42 isaconnected to control grid 33. A- biasingesource-of potential such as battery 23 has its positive terminal connected to emitter 43. An; adjustable impedance-element, .such asresistor 22, is -conn'ected: between. the negative terminal of battery 23 and base'44. Load. impedancedevice24 shown as a variable resistor 37 is connectedbetween. collector 42 and groundi In discussing the operation o the preferred embodimentofthe present invention, asshown in Fig. 2, reference' will'b'emade'to-Fig. 3'-and also to Fig;'4 wherein the abscissa representsplate voltage E involts and the ingpl'at'e voltage andreading plate current I; A load 4. line which is determined in the usual manner is shown by line 61.

Battery 23 is poled to cause current to flow through a first path comprising emitter 43, base 44, resistor 22, and battery 23. Resistor 22 is adjusted as in the circuit of Fig. 1 to regulate the amount .of current flowing in this path. This establishes the d'sired curve of operation for transistor 741,:as forzexamplefthe-icurve '55tofrFig. 3.

Assuming, as before, that load 24 is at its optimum value and-" d oes not 'change', the current flowing through a' second path comprising-load 2 4; collector42;,b'aseh44, cathode 32, anode 34, battery 35, and ground establishes the operatinglrpointssofitransistor 41; andzofi triode 31. The operating point of triode 31 is assumed to be at the intersection of load'line' 61With thecurve E =2 volts, point A of Fig. 4, while that of transistor 41 is at point A of Fig. 3.

If load 2.4rnow-.changes so;asetotincrease:currentflowing-therethIough; that is, if :the value. ofvariable resistor. 37 were-to decrease;.plate currentthroughtriode-'31-wi1'lv tendato increaseralong; load line-6150f Fig. 4 irom point A toward.- point. C. Thisawill cause current flowingthrough'. transistor; 4:1v .to 5 increase :along curve .55 :toward' point This causes-.thervoltage .app'earing :across collec: tor 42 -311(1:bQSGrzM {GLiDBISES as'shown. at 52 on'l igz. 3. This increase in voltage is applied across-cathode 32 andcontrol-. grid:33f of=..triode;-31;. thus-increasing the-bias :on control gridi33 as; for example,: the-voltage-level thereon: would gQ tOWaId JEgL 4: This increased biascauses: the current flowingdhnoughntriodefil: =todecrease; thus causing; it to: returnrto' itsm'ormaloperating vpointat A.

If. the value ofir resistor I 37 should: increase, current flowing.througlr;tr-iode- 31..wouldftend to: decrease along;-

loadxlinezdl -towardrpoint-B3 This, in 'turn, willzcause the: currentaflowin'g .through:transistor'- 41-. to decrease -to wardrpoint (Lot. Fig;; 3 The decrease. in; current will again:causeraachangeain voltage as shown; at: 53 OfliF'igg 3. Thisis appliedsacross controlugrid r33 and-.-cathode-.-32,- decreasing; ther bias on controb grid; 33 and increasing.

theacurrentziflowingzthrough triode 31: The CUFIeIlt2flDW"' ing through triode 31 will then return to its normal open atirigpoinhiA". I

lfi-rthe plate; supply voltagerwchangemc similar reactions 1 will occur. For-example, if plate 'voltageE variesfrom'w A; towardBt 01 2C. on:Fig.-4,.-,this.will causeaa change. in plate ,cur-rent. 1 being the-same -current which. flows throughload 24 andtransistor 41.. Thus,.the voltage drop across transistor 41 will change. appliedracrosstthe control grid and cathode of the tube, thus causingcurrent flowing through thetube and the load.to change back toward its normal level.

It will be understood that 'ci'rcuit specifications .forf'the'= constant current source shown in Fig.12 may vary according to the design for any-particular application; The following circuit,specifications'are included by' way of example only.

Although ajunctionatransistor is given as'the reference element in the cirucit-of- Fig; 2,. it is. to be understood.

that anytransiston may-be:used; It a point contact transistor is utilized; anresistancerelernent must beplaced in; the-base circutto overcome. the negative resistancecharacteristics inherent in point contact transistors.

Although? a triodeeiszshown: as-theaamplifier. in Fig, 2, iti is to be understbod: that. any). other vacuum. :tube 11-01:

transistor may ibezused .zassa: current generator for. the:

purposes of thisinvcntion.

The .1 current :regulator .o the ,present invention may also: be. utilized.;in-.;circuitsswhere; ann-alternatingpurrent.

This change .will be waveform is to be maintained constant irrespective of load impedance changes, for example, where the current source is used to control an alternating-current motor under all load conditions. For such a purpose the control current flowing through emitter and base of the transistor reference element would be modulated with a sample of the current waveform to be regulated.

There have been thus disclosed two embodiments of a self-regulating current source for reducing undesired variations in current flowing through the load irrespective of impedance changes in the load or changes in supply voltage. The circuit will react substantially instantaneously to either of these changes.

What is claimed is:

l. A self-regulating current source comprising: a current generator including an output electrode, an input electrode, and a control electrode; a transistor including an emitter, a collector, and a base; means for selecting the operating curve of said transistor connected between said emitter and said base; a load impedance device connected between said transistor and a point of fixed potential; and said transistor being connected between said input and control electrodes of said current generator, whereby variations of the voltage drop across said transistor are used to automatically control the current flowing through said current generator to maintain the current flowing through said load impedance device at a predetermined level irrespective of changes of the impedance of said load impedance device.

2. A self-regulating current source comprising: a current generator including an output electrode, an input electrode, and a control electrode; a transistor including an emitter, a collector, and a base; a first conducting path including said emitter and base of said transistor for establishing the operating curve of said transistor; a load impedance device connected between said transistor and said output electrode of said current generator; a second conducting path including said transistor, said current generator, and said load impedance device for establishing the desired operating point on said operating curve for said transistor and for establishing the operating point for said current generator; and said transistor being connected between said input and control electrodes of said current generator, whereby variations of the voltage drop across said transistor are used to automatically control the current flowing through said current generator to maintain the current flowing through said load impedance device at a predetermined level irrespective of changes of the impedance in said load impedance device.

3. A self-regulating current source comprising: a current generator including an input electrode, an output electrode, and a control electrode; a transistor including an emitter, a collector, and a base; a load impedance device; a first conducting path through said transistor including said emitter and base and including means providing a substantially fixed current flow therethrough for establishing the operating curve of said transistor; and a second conducting path through said transistor including said collector, said base, said current generator and said impedance device having a normal desired current flow, whereby a change in impedance of said load impedance device causes a variation of the normal desired current flowing through said second path which produces a change in voltage across said collector and base that is applied across said input and control electrodes to maintain the current flowing through said load impedance at the desired value.

4. The self-regulating current source defined in claim 3 wherein said means included in said first conducting path includes a bias source of potential for biasing said emitter in a relatively conducting polarity and an adjustable impedance element for establishing the amount of current which flows in said first path.

5. The self-regulating current source defined in claim 4 wherein said transistor is a junction transistor of the N-P-N type and said bias source is poled to maintain said emitter negative, with respect to said base.

6. The self-regulating current source defined in claim 3 wherein said current generator includes a space discharge device having a cathode, an anode, and at least one control grid.

7. A self-regulating current source comprising: a space discharge device having an anode, a cathode, and at least one control grid; a junction transistor having an emitter, a collector, and a base; a source of operating potential connected between said anode and a point of fixed potential; said base being connected to said cathode, said collector being connected to said control grid; a load impedance device connected between said collector and said point of fixed potential; :a bias source of potential; and an adjustable impedance element connected in series with said bias source, said base, and said emitter, whereby a change in voltage is produced across said collector and base in response to a change in impedance of said load, and is applied across said cathode and grid to maintain the current flowing through said load at a predetermined value.

8. A self-regulating current source comprising: a space discharge device including an anode, a cathode, and at least one grid; a junction transistor of the P-N-P type having an emitter, a collector, and a base; a source of operating potential connected between said anode and a point of fixed potential; said base being connected to said cathode, said collector being connected to said grid; a load impedance device connected between said collector and said point of fixed potential; said collector being connected to said cathode, said base 'being connected to said grid; a load impedance device connected between said base and said point of fixed potential; a bias source of potential having its positive terminal connected to said emitter; and an adjustable resistor connected between said bias source and said base, whereby a change in voltage is produced across said collector and base in response to a change in impedance of said load, and is applied between said cathode and grid to maintain current flowing through said load at a predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 2,576,056 Wannamaker Nov. 20, 1951 2,693,568 Chase Nov. 2, 1954 2,698,416 Sherr Dec. 28, 1954