US2554977A - Electronic voltage regulator - Google Patents

Description

y 29, 1951 w. T. CHAPIN 2,554,977

ELECTRONIC VOLTAGE REGULATOR Filed March 27, 1946 Inventor":

WilliamTChapin,

HI S Attorney.

Patented May 29, 1951 smo -norm VOLTAGE answerer :William T. .Chapin, Schenectady, N .-Y., .assignor .eto :General :Electric Company} a .cotnorationof Applica o Marchfit 4.5% .Ssrie N 5.24"?

1 Claim. '1

lvlyinvention relates to electron tube regulators and more particularly to electron tube-regulators employing a gas discharge device as a source of reference potential.

In accordance with one method of securing regulated unidirectional voltage or other desired controlled quantity the grid'bias of a series connected electron discharge device is controlled in accordanc i h the quan desired to'b m tained constant. In a voltage regulatonior instance, theactual output voltage -is compared with a lrnown constant voltage obtained from a gas discharge device or similar constant voltage source and ied' baok through an amplifier circuit tothe controlled device. This degenerativefeedbaclr causesthe output voltage to remain subtantially constant under all conditions of input volta e and-load current within the operating range of "thesyste n.

In general it has-been found particularly convenient to uses. gas discharge device as asou rce of oonstant reference potential in electron tube regulators. This device'has a-substantially constant voltage drop over a very wide range of operating current I and produces a substantially constant reforence voltage over a large rangeyin current flow. flhe gas discharge device is particularly desirable as compared with batteriesor other sources of reference potential 'because of its small size; low cost, and freedorn from deteriu r ion.

In the application of gas discharge devices to lec ron tub re ulators, maxi il r ae can be achieved if the circuit connectionspermit operation of the gasdischargedevice-in-the optimum portion of its operating characteristic while at "the same time allowing l other circuit components to operate most effectively. particular, the gas discharge deviceshould not-be located at -a point in 'the circuit where its own voltage drop serves to reduce the cathode-anode potential of an amplifying tube in the icedback path. Otherwise theamplificationof that tube will be reduced and the degree --of .regulationobtained thereby limited. --F11 rthermore, the vgas discharge device should be arranged to carryeurrent which is-reasonablyconstant over all conditions of'oporation of the regulating circuit. :In. addition it is highly desirablezthatthegasidischarge device he arranged at a =.-point: in the .circuit .where it is not required to carry a .largecurrent, particularly alarge current which variesdn. accordance with the-operatingconditions-of the regulator.

In addition :to tithe .above considerations applying La gas discharge device to. aneeleotron "-2 tube regulator it is essential to arrangethe device in amanner which provides a maximum degreeof stability. In the region where-the voltage drop across an electron discharge device is nearly constant, there are usually points-wherein the device presents .a negative impedance tothe flow of current. 'That is, under some conditions of operationan increase in current flow -through the gas discharge device results-in a decrease inyoltage drop. At such points, the regulatorhas an inherent tendency to be unstable in .operation and-to pass-from one condition of operation to another in random -fashion. In order to avoid this phenomena it 'is desirable that the gas discharge device belocated in theregulator circuit in amanner whichfidecouples this negative resistancecharacteristic to a maximum degree.

"Itisthe object of my inventiontoprovide an improved electronic voltage regulator.

It is a further object of my invention -to-provide a regulator inmhiohthe current flow through the source of reference potential is nearly constant over all conditions of operation.

Still another object of my inventionis toprovi e-aresu ato wh h c rren aw amen vide a regulator in which amplifying devices in the feedback path operate at maximum amplification and efilciencyeunder all conditions of QW QFi -l l eslql tivne obi tw m invention t provide a regulator havingainaximumidegree of stability.

The novel features which-.1believe to be characteristic,.of my inyentionar eset forth withparticularity in the I n dediolaim. Myinvention itself, however 13 as to its organization and method of pe together with further obl- 1'e s;ens-a reeing.-thre ;m b s i rstood by reference to the following disclosure ta en q et ei with h ecoiribsliyihg drawingsdngyhioh Fig. l illustrates one/embodimentpf invention and Fjig. 2 is an explanaes dia rsm re s i i ths idtteierringnow tofiignl which. shows a schematic diagramofa voltage regulator embodying the teatur es of unvention, kl .represents ia transformer having its primary winding 3 conr te t .te rmi l fi u i chi a comlfited so cc of -alternatingvoltage. Secondary ll .of mem am v l a i-andss99nderv5 t n orme Lsuilnl anode .vsltsseiuth .swedeyiqev. .;l9 fi ter compr sin sm oth n charge device l2. Grid bias for device I2 is supplied from the auxiliary control circuit comprising gas discharge device 15, potentiometer l4, resistance l3, resistance l6, and condenser 19, the operation of which is explained in further detail below.

Considering now the auxiliary control circuit, condenser I9 is periodically charged through rectifier 20 to the full value of voltage across one section of secondary winding 5 of transformer l. Inasmuch as the capacity of this condenser is made relatively large, the charging action of condenser IS provides a relatively constant voltage across that condenser which is nearly equal in magnitude to, the peak voltage across condenser 1.; Hence, the series circuit comprising gas discharge device l5, resistance 16, and condenser 19 maybe regarded as including two sources of voltage (device l5 and condenser [9) and a series resistance (resistance It) connected across the voltage developed between terminals I1 and i8. Inasmuch as the voltage across device l5 may be regarded as constant, current flow must take place through resistance Hi to cause the voltage difference between the negative terminal of device l5 and the negative load terminal 18 .to equal the difference between these two volt ages. Designating the load voltage as as and the voltage of device H: as er, the total grid bias applied to device I2 then becomes:

Eg=eoer+ker Where:

Eg is the applied grid bias.

7c is the portion of the voltage across device i5 between the roving terminal of potentiometer l4 and the negative terminal of device 15.

Since the valueof k is always less than one, the term 1-4:: will always be positive and can be regarded as a new constant K. Then:

'Hence the grid voltage applied to device I2 is proportional to the difierence between the regulator output voltage and a selected portion of the voltage across electron discharge device I5, the value of the selected portion being determined by the setting of potentiometer [4.

Operation of the circuit of Fig. 1 is based on the principle of inverse feedback with respect to the difference between the voltage across terminals l1 and I8 and a selected portion of the voltage across 'gas discharge device 15. It is well known that a high degree of amplification in the feedback path will reduce this'voltage diiference substantially to zero even though the applied voltage at terminals 2 and the impedance across terminals 1! and [8 are changed. In the circuit of Fig. 1, this high degree of amplification is provided by electron discharge device l2 acting in conjunction with resistance In to control the effective internal resistance of electron discharge device ll. With the circuit of the figure, these components may be chosen to provide a maximum degree of amplification for in practical regulator applications the voltage across condenser 9 will not vary over a large range. The relatively constant voltage drop across gas discharge device does not reduce the effective anode voltage at" device 12 because device I5 is located in an entirely separate circuit where it does not infiuence device l2.

. Further features of my invention will now be explained with reference to Fig. 2 which shows a modified equivalent schematic diagram of a por- :;tion of the circuit of 'Fig. 1. In Fig. 2 battery 2| indicates schematically the constant voltage which appears across condenser 19. Inasmuch as rectifier 29, Fig. 1, is connected to charge condenser IS in a manner causing the condenser electrode connected to terminal 18 to be positive, battery 2| is shown as having its negative terminalat point-a. For purposes of illustration, the peak potential appearing across half of the sec-. ondary winding 5 of transformer l is shown as 400 volts, thereby causing point a to have a po- -tential of 400 volts negative with respectto the potential of terminal 18. This voltage also appears across condenser l but the voltage drops across inductor 8 and device il reduce the voltage at terminals [1 and I8 to a lower value. For purposes of illustration, this value is taken as 300 volts. Preferably a gas discharge device [5 is employed which provides a voltage drop which is greater than the voltage across terminals l1 and l 8. In the voltage regulator herein described, for instance, a device giving 400 volts drop, may be used thereby causing point b to be 400 volts nega tive with respect to terminal H or volts negative with respect to the potential of terminal l8.

The above described regulating circuit hasa number of advantages. In particular, the grid of device l2 can be maintained at a negative potential relative to the cathode over any desired voltage range by properly proportioning the values of the circuit components. This prevents flow of grid current in device l2, thereby enabling it to operate in the most effective region of its characteristics and at a point where overheating will not occur. Furthermore, variation in output voltage across terminals I! and I8 has a reduced effect on current flow through device I5 by reason of the auxiliary voltage source 2|. If, for instance, potentiometer 14 is adjusted to provide output voltage across terminals l1 and iii of volts the total effective voltage acting in the circuit comprising device 15, resistance [6, and voltage source 2!, is 400+150 or 550 volts. This represents about 80 per cent of the 700 volts applied to this circuit for 300 volts output. Obviously, greater voltage at source 2| provides an even smaller change in voltage across this circuit when load voltage is varied.

Inasmuch as the value of grid voltage applied to device 12 is proportional to the difference between a pre-selected portion of the voltage across gas discharge device l5 and the output voltage across terminals l1 and IS, the exact value of voltage at source 2|, Fig. 2, does not influence regulator performance. Hence, this voltage may be obtained from an unregulated source, such as transformer 1, Fig. l,'without influencing performance of the regulator.

While I have described herein the application of my invention to a voltage regulator, it will be apparent to those skilled in the art that it may be applied to other regulators as well. If, for

5 instance, it is desired to maintain the speed of a direct current motor constant, the circuit comprisin device l5, potentiometer l4, resistance I6 and condenser l9, may be connected directly across the motor terminals. This will cause the regulator to maintain substantially constant the counter-electromotive force of the motor and hence regulate the motor speed. In a similar manner the circuit may be applied to maintain constant load current or other load quantity which may be represented by a voltage capable ofactuating the control circuit.

While I illustrated and described a particular embodiment of my invention, it will of course be understood that I do not wish to be limited thereto since various modifications both in the circuit arrangement and the instrumentalities employed may be made, and I contemplate by the appended claim to cover any such modifications as fall within the true spirit and scope of my invention. 1 What I claim as new and desire to secure by Letters Patent of the United States is:

A regulated power supply system comprising, in combination, a transformer adapted to be energized from an alternating voltage and having a secondary winding, a load circuit energized fromsaid secondary winding and serially consisting of a rectifier and the anode-cathode path of a grid-controlled discharge device and a load device, a second grid-controlled discharge device having its anode-cathode path connected across said load device and said first device, means for varying the grid voltage of said first device in accordance with the space current in said second 6 device, a control circuit connected directly across said load device and responsive to the load voltage, said control circuit serially including a potentiometer, a series regulating resistor and a capacitor, means comprising a voltage-stabilizing glow discharge device connected directly across said potentiometer for maintaining a constant voltage thereacross, the grid of said second tube being connected to an adjustable tap point on said potentiometer, and means comprising a second.rectifier energized from said transformer for independently charging said capacitor to a voltage proportional to the voltage across said secondary winding, the polarity of said last voltage being such as to aid the flow cf current through said regulating resistor due to the load voltage, the resultant variations in the grid voltage of said first device being in polarity to minimize variations in said load voltage.

WILLIAM T. CHAPIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,323,857 Trevor July 6, 1943 2,377,500 Johnson June 5, 1945 2,414,122 Potter Jan. 14, 1947 2,414,242 Potter Jan. 14, 1947 2,466,874 Bixby Apr. 12, 1949

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