US2956172A

US2956172A - Voltage regulator

Info

Publication number: US2956172A
Authority: US
Inventors: Robert A Torkildsen
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1959-07-13
Filing date: 1959-07-13
Publication date: 1960-10-11
Anticipated expiration: 1977-10-11

Description

Oct. 11, 1960 R. A. TORKILDSEN 2,955,172

vaumcz: REGULATOR Filed July 1:. 1959 FIG. 1

LOW VOLTAGE 36 0.0. 1. 37 SUPPLY LOW 46 36 VOLTAGE 0.0. 37 SUPPLY INVENTOR.

ATTORNEY claims.

United States Patent VOLTAGE REGULATOR Robert A. Torkildsen, Milwaukee, Wis., assignor to General Electric Company, a corporation of New York Filed July 13, 1959, Ser. No. 826,626 6 Claims. (Cl. 307-31) This invention relates to voltage regulators and in particular to a circuit for maintaining the ratio of the voltages developed across two series connected impedances connected across a source of operating potential substantially constant, independent of wide variations in the values of such impedances.

It is an object of this invention to provide an improved stable voltage regulator.

It is another object to provide a stable voltage regulator adaptable for use with a low direct current voltage supply.

It is another object to provide a stable voltage regulator for maintaining the ratio of voltages developed across series connected impedances relatively constant, independent of the variation in values of such impedances.

Generally speaking, and in accordance with the invention, there is provided a voltage regulator comprising a pair of transistors of respective opposite conductivity types connected in complementary symmetry arrangement. A pair of series connected impedances across which it is desired to maintain the ratio of the developed voltage'outputs constant is connected across the collectors of the transistors. The junction of the impedances is connected to the junction of the emitters of the transistors. Connected between the terminals of a unidirectional potential source is a series arrangement of a plurality of resistances. Connected between one of the transistors and one terminal of the source is a first resistance of the plurality for providing biasing potentials thereto to render it operative and connected between the other transistor and the other terminal of thesource is a second resistance of the plurality for providing operating biasing potentials to the other transistor whereby the ratio of the voltage developed across the respective impedances is maintained at the ratio of the values of the resistances independent of wide variations in the values of the impedances.

The features of this invention, which are believed to be new, are set forth with particularity in the appended The invention itself, however, may best be understood by reference to the following description when taken in conjunction with the accompanying drawing which shows embodiments of a voltage regulator according to the invention.

In the drawing,

Fig. 1 is a schematic depiction of an embodiment of the invention; and

Fig. 2 is a diagram of another embodiment of the invention. I

Referring now to Fig. 1, a first transistor 10, which is depicted as a PNP conductivity type, comprises an emitter electrode 12, a base electrode 14 and a collector electrode 16. A second transistor 20, which is shown as being of the NPN conductivity type, comprises an emitter electrode 22', a base electrode 24 and a collector electrode 26. Collector electrode 16 is directly connected to the negative terminal of a low direct current voltage supply source 30, collector electrode 26 being connected to the positive terminal of source 30. Connected across source 30 is a series combination of a resistor 32 and a resistor 34, the junction point of

re sistors

32 and 34 being connected to base electrode 14 and base electrode 24. Connected between collector electrode 16 and collector electrode 26 is a series combination of a load impedance 36 and a load impedance 38. The junction 37 of

load impedances

36 and 38 is connected to the junction 39 of

emitters

12 and 22.

In considering the operation of the device of Fig. 1, let it be assumed that the ratio of the value of resistor 32 to the value of resistor 34 is equal to the ratio of the value of impedance 36 to the value of impedance 38. In this situation, junction point 39 will be at the same potential as junction point 33. No current will flow through

transistors

10 and 20 and current will flow from the positive terminal of source 30 through

resistors

34 and 32 to the negative terminal and from the positive terminal of source 30 through impedance 38 and impedance 36 to the negative terminal of source 30, the quantity of current flowing through the series combination of

resistors

34 and 32 and the quantity of current flowing through the series arrangement of

impedances

38 and 36 depending upon the respective values thereof. In this situation, therefore, the voltages developed across

impedances

36 and 38 have a ratio equal to the ratio of the values of

resistors

32 and 34.

Let it now be assumed that the ratio of the value of resistor 32 to the value of resistor 34 is greater than the ratio of the value of impedance 36 to the value of im pedance 38. In this situation, junction point 39 tends to go negative with respect to junction point 33, to cause conduction in NPN transistor 20. The current from source 30 flowing through impedance 36 is augmented by the current from transistor 20. The net result is for an increase in the voltage developed across impedance 36. The amount of current supplied by transistor 20 is that amount which will just about bring

junction points

37 and 39 back to potential of junction point 33.

In the condition where the ratio of the value of resistor 32 to the value of resistor 34 is less than the ratio of the value of impedance 36 to the value of impedance 38, the same phenomena ensue except that, since in'this

situation junction points

37 and 39 tend to go positive with respect to junction point 33, it is PNP transistor 10 which is rendered conductive. The current through impedance 38 is augmented. The system also stabilizes when the potential at

junction points

37 and 39 is substantially equal to the potential at junction point 33.

Referring now to Fig. 2, there is shown a circuit substantially similar to the circuit depicted in Fig. 1 and accordingly like elements have received the same designating numerals. In the circuit of Fig. 2, there is provided the PNP transistor 10 comprising emitter electrode 12, base electrode 14 and collector electrode 16 and NPN transistor 20 comprising emitter electrode 22, base electrode 24 and collector electrode 26. .Collector electrode 16 is connected to the negative terminal of direct current supply source 30 and the collector electrode of transistor 20 is connected to the positive terminal of direct current supply source 30; Connected across source 30 is a series arrangement of a resistor 40, a resistor 42 and a resistor 44, base 14 being connected to the junction point 41 of

resistors

40 and 42 and base 24 being con nected to the junction point 43 of

resistors

42 and 44.

' shown connected in shunt with

load impedances

36 and 38. The resistors comprising the bleeder are suitably chosen to have relatively small values and the arrangement is provided for balancing the transistors, i.e., in the event that the l the collector current with zero emitter current, is different in one transistor from the other, such difierence can be eliminated.

In the circuit of Fig. 2, similar to that of Fig. 1, it is desired to maintain the ratio of the voltages developed across

output impedances

36 and 38 equal to the ratio of the values of

resistors

40 and 44.

In operation, the value of resistor 42 is chosen to be small relative to the values of

resistors

40 and 44 and is so chosen that when the ratio of the values of

impedances

36 and 38 is equal to the ratio of the values of resistors 49 and 44, junction point 39 is slightly negative With respect to junction point 43 and slightly positive with respect to junction point 41. Accordingly, with such arrangement, both transistors and 20 are normally slightly conductive and a balanced condition maintained in the currents flowing through the respective loops due both to the source current through

impedances

38 and 36 and the transistor currents flowing therethrough.

Let it now be assumed that the ratio of the value of resistor 40 to the value of resistor 44 is greater than the ratio of the value of impedance 36 to the value of impedance 38. In this situation, junction point 39 tends to become more negative than it is in the balanced condition. The results that ensue from such a situation is that conduction in transistor 20 is increased and conduction in transistor 10 is decreased and possibly rendered at cut-off. The increase of current from transistor 20 flowing through impedance 36 together with the source current flowing therethrough causes an increase in the voltage developed across impedance 36 and the system stabilizes at that increase of level of current from transistor 20 when the potential at

junction points

39 and 37 substantially approaches the potential they assume when the system is in the balanced condition. In the situation where the ratio of the values of

resistors

40 and 44 is less than the ratio of the value of impedance 36 to the value of impedance 33, junction point 39 tends to rise to a potential more positive than its potential when the system is in a condition of balance. In this situation, due to increased current flow through transistor 10, current flow is enhanced in the same direction through impedance 38 as the flow of source current therethrough. Simultaneously, current flow through transistor 20 is decreased and depending upon the diiference in ratios of the resistors and the output impedances, possibly cut-off. Thus, the "oltage developed across impedance 38 increases. The system again attains a balance at that point where the potential at

junction points

39 and 37 substantially equals the potential thereat when the system is in the balanced condition. Here again, the net result is for the ratio of the output voltages developed across .

impedances

36 and 38 to be equal to the ratio of the value of

resistors

40 and 44.

It is thus seen that with this invention, there-is provided a voltage regulator for maintaining the ratio of the voltage developed across series connected impedances at a chosen value independent of the current drawn from a direct current voltage supply source, i.e., independent of the actual ratio of the values of the impedances. Such regulator is particularly valuable where it is desired to maintain such constant ratio from a low direct current voltage source. I

While there have been shown particular embodiments of this invention, it will, of course, be understood that it is not wished to be limited thereto since difierent modifications may be made both in the circuit arrangements and in the instrumentalities employed, and it is contemplated in the appended claims to cover any such modifications as fall within the true spirit and scope of the invention.

between, said first collector being connected to one terminal of said source, said second collector being connected to the other terminal of said source, a series arrangement of first and second output impedances having a second junction therebetween connected between said collectors, said first and second junction being connected whereby said impedances are connected across said source and whereby said first impedance is included in the output of said first transistor and said second impedance is included in the output of said second transistor, a series arrangement of a plurality of resistances connected between said terminals of said source, said first base electrode being connected to said one terminal through a first resistance of said plurality, second base electrode being connected to the other terminal of said source through a second resistance of said plurality whereby the potential at said second junction is maintained at the potential that said second junction attains when the ratio of the values of said first and second resistances is equal to the ratio of the values of said output impedances.

2. A voltage regulator comprising a source of unidirectional potential, at first transistor of one conductivity type having first emitter, base and collector electrodes, a second transistor of the opposite conductivity type having second emitter, base and collector electrodes, said emitters being connected to form a first junction therebetween, said first collector being connected to one terminal of said source, said second collector being connected to the other terminal of said source, a series arrangement of first and second output impedances having a second junction therebetween connected between said collectors, said first and second junctions being connected whereby said impedances are connected across said source and whereby said first impedance is included in the output of said first transistor and said second impedance is included in the output of said second transistor, a series arrangement of first and second resistances having a third junction therebetween connected between the terminals of said source, said base electrodes being connected to said third junction whereby said second junction is maintained at the potential that said second junction assumes when the ratio of the values of said impedances is equal to the ratio of the values of said resistances.

3. A voltage regulator as defined in claim 2 wherein said first transistor is of the PNP conductivity type, wherein said second transistor is of the NPN conductivity type, wherein said first collector is connected to the negative terminal of said source and wherein said second collector is connected to the positive terminal of said source.

4. A voltage regulator comprising a source of unidirectional potential, at first transistor of one conductivity type having first emitter, base and collector electrodes, 2 second transistor of the opposite conductivity type having second emitter, base and collector electrodes, said emitters being connected to form a first junction therebetween, said first collector being connected to one terminal of said source, said second collector being connected to the other terminal of said source, a series arrangement of first and second output impedances having a second junction therebetween connected between said collector, said first and second junctions being connected whereby said impedances are connected across said source and whereby said first impedance is included in the output of said first transistor and said second impedance is included in the output of said second transistor, a series arrangement comprising first, second and third resistances connected between the terminals of said source, said first base electrode being connected to the junction of said first and second resistances, said second base electrode being connected to the junction of said second and third resistances whereby the potential at said second junction is maintained at the potential that said second junction assumes when the ratio of the values of said impedances is equal to the ratio of the values of said first and third resistances.

5. A voltage regulator as defined in claim 4 and further including means for balancing thet respective I, in said transistors.

6. A voltage regulator as defined in claim 5 wherein said first transistor is of the PNP conductivity type wherein said second transistor is of the NPN conductivity type, wherein said first collector is connected to the negative terminal of said source and wherein the said second collector is connected to the positive terminal of said source.

References Cited in the file of this patent UNITED STATES PATENTS