US3510754A - Series voltage regulator employing a constant current impedance branch and means for maintaining said constant current - Google Patents

Description

May 5, 1970 F. BARNES 3,510,754

H. SERIES VOLTAGE REGULATOR EMPLOYING A CONSTANT CURRENT IMPEDANCE BRANCH'AND MEANS FOR MAINTAINING SAID CONSTANT CURRENT Filed June 21, 1967 INVENTOR. HAROLD F. BARNES ATTORNEY United States Patent 3,510,754 SERIES VOLTAGE REGULATOR EMPLOYING A CONSTANT CURRENT IMPEDANCE BRANCH AND MEANS FOR MAINTAINING SAID CON- STANT CURRENT Harold F. Barnes, RR. 1, Box 115-3, Oviedo, Fla. 32765 Filed June 21, 1967, Ser. No. 649,077 Int. Cl. Gf 1/56 US. Cl. 323-9 3 Claims ABSTRACT OF THE DISCLOSURE A constant current device is provided for supplying error signals to a DC. sensing amplifier and a series regulator responsive to voltage changes for maintaining a constant voltage across a load. A compensating circuit is utilized for maintaining a constant flow of current through an impedance circuit so that error signals are supplied to the D.C. sensing amplifier undiminished.

The invention described herein was made by an employee of the United States Government and may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The invention relates to a constant current device for supplying error signals to a DC. amplifier and series regulator responsive to voltage changes for maintaining a constant voltage across a load.

Heretofore, devices manufactured to produce a constant voltage across a load which utilized constant current devices were complicated, and used many components to achieve adequate results.

In many electronic circuits it is desired to maintain a substantially constant voltage across a load at all times. Frequently, such is difficult due to changing load currents and variations in the input voltage power supply. In order to overcome these problems, as previously mentioned, complicated electronic circuits have been utilized.

In accordance with the present invention, it has been found that the foregoing difiiculties may be overcome by providing a novel regulator for producing a constant voltage across a load even when the load current varies or the input power supply varies. This regulator includes the following basic parts: (1) a DC. power supply, (2) a pair of leads connecting the power supply to the load across which a constant voltage is desired, (3) a series voltage regulator interposed in one of the leads between the power supply and the load, (4) a reference voltage junction interposed in the other lead between the power supply and the load, (5) a constant current impedance branch having one end connected to the reference voltage junction and the other end connected to a second junction, (6) a sensing transistor having base, emitter and collector electrodes with the base electrode being connected to the second junction for sensing voltage changes at the reference voltage junction through the impedance branch; the series voltage regulator is connected to one of the collector and emitter electrodes for responding to current changes through the sensing transistor as the voltage on the base electrode changes to maintain a constant voltage across the load, and (7) a compensating transistor circuit connected to the second junction responding to changes in the. voltage at the reference junction for main- 3,510,754 Patented May 5, 1970 taining a constant current flow through the impedace branch. Thus, by maintaining a constant current flow through the impedance branch small voltage variations at the reference voltage junction are imparted to the base electrode of the sensing transistor causing such to operate the series voltage regulator to maintain a constant voltage across the load.

The circuit constructed in accordance with the present invention is designed to eliminate the undesirable loading effect of the emitter base current of a transistor used in an error sensing circuit of a regulated DC. power supply. Such eiiect causes poor regulation of the power supply.

Accordingly, it is an important object of the present invention to provide a regulator which utilizes a constant current circuit for maintaining a constant voltage across a load.

Still a further important object of the present invention is to provide a regulator which produces a constant voltage across a load, while minimizing the number of electronic components in the circuit.

A further important object of the present invention is to eliminate the undesirable loading effect of the emitter base current of a transistor used in an error sensing circuit of a regulated DC. power supply circuit.

Still a ufrther important object of the present invention is to provide a regulator which utilizes a constant current circuit which allows the entire error signal created by a change in voltage to be applied to the base electrode of a transistor of a sensing circuit.

Other objects and advantages of this invention will become more apparent from a reading of the following detailed description and appended claims taken in conjunction with the accompanying drawing wherein:

The sole figure is a schematic diagram of a regulator for producing a constant voltage across a load constructed in accordance with the present invention.

Referring in more detail to the schematic diagram wherein a regulating circuit for efiectively maintaining a substantially constant voltage across a load is illustrated, a DC. power supply 10 is connected between a pair of leads 11 and 12, respectively. A positive side of the voltage supply 10 is connected to the lead 11, while the negative side of the voltage supply 10 is connected to the lead 12. The voltage supply 10 is shown as a battery, however, such could be any suitable DC. power supply. A constant current impedance branch, generally designated at 13, is connected to a reference voltage junction 14 interposed in lead 11 between the power suppy 10 and a load 15. The constant current impedance branch 13 includes a variable resistor 16 which has one side connected to the reference voltage junction 14. A wiper arm 17, which controls the resistive value of the variable resistor 16, is connected via lead 18 to a second junction 19.

A base electrode 20 of a P.N.P. sensing transistor 21 is connected to junction 19. The base electrode 20 of the sensing transistor 21 senses voltage changes at the reference voltage junction 14 through the impedance branch 13. Also, connected to the junction 19 is a collector electrode 22 of a compensating N.P.N. transistor 23. The sensing transistor 21 has a collector electrode 24 which is connected by means of lead 25 to a control element 26 of any suitable series voltage regulator, such as shown in block form at 27. In one particular embodiment a conventional Darlington regulator is utilized. An input terminal 28 of the regulator 27 is connected to the negative lead 12 and an output terminal 29 is connected via lead 30 to a junction 31. An emitter electrode .32 of the sensing transistor 21 is connected by means of lead 33 to the junction 31. Junction 34 is connected to junction 31 via lead 35 and junction 36 is connected to junction 34 via lead 37. Connected between an emitter electrode 38 of the compensating transistor 23 and the junction 34 is a bias power supply generally designated at 39. The bias power supply 39 includes a Zener diode 40 having its anode connected to the emitter electrode 38 and its cathode connected via lead 41 to junction 34. A DC. voltage supply 42 is connected in shunt with the Zener diode 40 and has its negative terminal connected to the emitter 38 of the compensating transistor 23 and its positive terminal connected to junction 34 through lead 41. A base electrode 43 of the compensating transistor 23 is connected by means of lead 44 to a Wiper blade 45 of a variable resistor 46. The other side of the variable resistor 46 is connected by means of lead 47 to junction 36. The load 15 across which it is desired to maintain a constant voltage is connected by means of lead 48 to the reference voltage junction 14, and by means of lead 49 to junction 36.

One of the primary purposes of the subject invention is to maintain a constant voltage across the load 15 as the impedance of such varies, or if the voltage of the power supply varies. The bias supply shown generally at 39 supplies the base to emitter flow of current of sensing transistor 21, as well as the emitter to collector flow of current of compensating transistor 23. A complete return path is also provided for the collector to base (ICBO) flow of current which results in the stabilization of sensing transistor 21. If the impedance of load decreases, the current flow through the load would tend to increase. Such causes the voltage at junction 14 to tend to decrease. The decrease in voltage at junction 14 causes the voltage on the base electrode of the sensing transistor 21 to decrease accordingly. When the voltage on the base electrode 20 decreases such tends to approach the value of the voltage on the collector electrode 24. Such, in turn, causes an increase in the flow of current through the emitter electrode 32, the collector electrode 24, lead to the control electrode 26 of the series voltage regulator 27. Such increase in current causes the voltage drop between the input terminal 28 and the output terminal 29 of the series voltage regulator to decrease. The decrease in voltage across the series voltage regulator 27 causes the voltage across the load 15 or between junction 14 and junction 36 to remain constant.

It is desired that a constant current be maintained through the impedance branch 13 which includes the variable resistor 16 so that for every change in voltage at junction 14, such change will be felt undiminished on the base electrode 20 of the sensing transistor 21. In order to accomplish such, the decrease in voltage, which was initially felt on base 20 of transistor 21, is also applied to the collector electrode 22 of the compensating transistor 23. The decrease in voltage on the collector electrode 22 of the compensating transistor 23 tends to approach the value of base electrode 43. Such, in turn, causes an increase in the flow of current through emitter electrode 38 and collector electrode 22. This increase in flow of current is substantially the same as the increase in the flow of current through base electrode 20 and emitter electrode 32 of sensing transistor 21. The current flow through the variable resistor 16 remains constant. The variable resistor 46, which is connected to the base electrode 43 of the compensating transistor, is adjusted to control the current flow through the compensating transistor 23 so that the current flow through the variable resistor 16 will remain constant as the impedance of the load 15 varies. Such would also be true if the input voltage from the power supply 10 varied. A reference D.C. power supply 39 is connected between the emitter electrode 38 of the compensating transistor 23 and junction 34. This potential is also the same potential applied to the emitter electrode 32 of the sensing transistor 21.

The above describes the operation of the regulating circuit When there is a decrease in load impedance or a decrease in the input voltage. When there is an increase in load impedance the voltage at the reference voltage junction 14 would tend to increase and suchincrease is felt on the base electrode 20 of the sensing transistor 21. This causes the conduction of the sensing transistor 21 to decrease allowing less current flow to the control electrode 26 of the regulator 27. Such increases the voltage drop between the input and output terminals ofthe regulator 27. The increase in voltage drop across the regulator 27 causes a decrease in voltage drop across load 15 resulting in a constant voltage across the load. During this operation the compensating transistor 23 would conduct less, allowing the current flow between the emitter electrode 32 and the base electrode 20 of the sensing transistor 21 to decrease a corresponding amount, thus the current flow through the variable resistor 16 remains constant.

It is noted that the bias on the base of transistor 23 is controlled by the variable resistor or potentiometer 46. A setting towards one end of the variable resistor will cause the output votlage at reference voltage junction 14 to rise with an increase of load current. A setting towards the other end of the variable resistor 46 will have the opposite effect, i.e., an increase of load current will cause the output voltage at junction 14 to drop. Therefore, a correct setting of variable resistor 46 will result in no change in the output voltage at junction 14.

While the changes in current and voltages have been positively stated in describing the operation of the regulator for the purpose of clarity, such operation acts so instantaneously that these changes are mere tendencies, and as a result, a substantially constant output voltage across the load 15 is maintained for wide impedance changes in the load.

Whie a preferred embodiment of the invention has been described using specific terms, such description is or illustrative purposes only, and it is to be understood that changes and variations may be made.

What is claimed is:

1. A regulating circuit for effectively maintaining a substantially constant voltage across a load comprising:

(A) a DC. power supply;

(B) a pair of leads connecting said power supply to said load;

(C) a voltage regulator interposed in one of said leads between said power supply and said load;

(D) a reference voltage junction interposed in one of said leads;

(E) a variable impedance branch having one end connected to said reference voltage junction;

(F) a second junction connected to the other end of said impedance branch;

(G) a sensing transistor circuit connected between said second junction and said voltage regulator for supplying a control signal to said regulator responsive to changes in voltage at said reference voltage junction;

(H) a compensating transistor circuit connected to said second junction for maintaining the current flow through said constant current impedance branch substantially constant as the voltage at said reference voltage junction varies;

(I) said compensating transistor circuit including a variable resistor for maintaining a constant current through said impedance branch; and

(J) said control signal operating said voltage regulator causing such to maintain a constant voltage across said load as the voltage at said reference voltage junction varies.

2. The regulating circuit as set forth in claim 1 wherein:

(A) said compensating transistor circuit includes a compensating transistor having base, emitter and collector electrodes, said collector and said emitter electrodes being connected between said second junction and one of said leads; and

5 6 (B) said variable resistor connected between said base 2,942,174 6/1960 Harrison. electrodes and one of said leads. 2,981,884 4/ 1961 Tighe. 3. The regulating circuit as set forth in claim 2 wherein: 3,072,841 1/ 1963 Saunders.

(A) said compensating transistor circuit includes a 3,305,764 2/1967 Todd.

diode and a DC. power supply connected in shunt 5 therewith; and LEE T. HIX, Primary Examiner (B) said diode and DC. power supply being connected between said emitter electrode and one of said leads. GOLDBERG, Asslstallt EXammeI References Cited US 10 UNITED STATES PATENTS 307297; 32322, 38

2,932,783 4/1960 Mohler.

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