US3778698A - Integrated voltage stabilizer with negative internal resistance - Google Patents

Abstract

An integrated voltage-stabilizing network with grounded substrate has an input terminal, an output terminal and a reference terminal, the latter being held at a fixed potential relative to the output terminal by a regulator also delivering a constant current to that reference terminal which is connected to a tap on a voltage divider inserted between the output terminal and ground. The regulator is connected in the base/emitter circuits of two parallel transistors which lie between the input and output terminals and deliver respective components of an output current, one of these parallel transistors lying in series with a further transistor which is paired with a similar transistor supplying a like current components to the reference terminal.

Description

United States Patent 1 1 [111 3,778,698 Romano Dec. 11, 1973 [54] INTEGRATED VOLTAGE STABILIZER 3,617,859 11/1971 Dobkin et a1. 323/4 WITH NEGATIVE INTERNAL RESISTANCE [75] Inventor: Aldo Romano, Monza, Italy Primary Examiner-Gerald Goldbfirg I Attorney-Karl F. Ross [73] Assignee: Ates Componenti Elettronici, S.p.A.,

Milano, Italy 5 B R C 7 A ST A T [22] Filed: Aug. 24, 1972 1 An integrated voltage-stabilizing network with [21] Appl' 283,423 grounded substrate has an input terminal, an output terminal and a reference terminal, the latter being [30] F i A li i P i i Data held at a fixed potential relative to the output terminal Aug. 25 1971 Italy 27839 A/7l by a regulator also delivering a constant current to that reference terminal which is connected to a tap on [52] us CL 323/4 323/9 323/22 T a voltage divider inserted between the output terminal 323/38 307/297 and ground. The regulator is connected in the base/e- [511 In! CL n 6 1/56 mitter circuits of two parallel transistors which lie be- [58] Field g 9 22 T tween the input and output terminals and deliver reb spective components of an output current, one of these parallel transistors lying in series with a further [56] References Cited transistor which is paired with a similar transistor supplying a like current components to the reference ter- UNITED STATES PATENTS v minaL 3,445,751 5/1969 Easter 323/9 3,509,448 4/1970 Bland 323/22 T X 7 Claims, 2 Drawing Figures Current Sensor i F i T Controller l li'l,

t W l 4 I Q 2 I M 1 I J d'c l 7 yo I :5 4 Constontl l -Voltoge F T H Generator out &1 F 5 (f R 2 R 1 v NV b l I 6 ii Lg Integrated Circuit 3 L I PAIENTEnnu: n ma sum 1 or 2 FlG.l

PATENTED DEC 1 1 I875 SHEET 2 BF 2 INTEGRATED VOLTAGE STABILIZER WITH NEGATIVE INTERNAL RESISTANCE My present invention relates to a voltage stabilizer, particularly one of the integrated type, in which an internal negative resistance compensates for changes in the output voltage due to variations in load current.

Such voltage stabilizers are useful for the energization of low-power d-c motors employed, for example, to drive record players, tape or cassette recorders and similar devices in which the load changes but little during normal use and which can be operated by lowvoltage batteries of, say, 6 V or less.

The general object of my present invention is to provide a system of this character which is of simple construction and lends itself to inexpensive mass production.

A more particular object is to provide an integratedcircuit module of this description having but three live terminals (referred to hereinafter as input terminal, output terminal and reference terminal) to be connected between the current source and the load, thereby minimizing the number of external impedance elements required.

A voltage stabilizer according to my invention comprises, essentially, a constant-voltage generator connected between the output and reference terminals, the latter terminal being tied to a tap on a voltage divider inserted between the output terminal and ground. The reference terminal also receives a current component, proportional to the current emitted by the output terminal, from a current-sensing circuit which is connected between the input terminal on the one hand and the output and reference terminals on the other hand. As will be shownherein'after, this arrangement establishes a negative resistance of a magnitude proportional to the load current.

In the preferred embodiment described hereinafter, the constant-voltage generator supplies to the reference terminal a substantially constant reference current which supplements the proportional current component delivered by the sensing circuit. The latter advantageously includes two main transistors connected in parallel branches between the input and output terminals for respectively controlling the magnitude of a first and a second component of the load current, the two transistors being so interconnected that these current components are identical or otherwise maintain a predetermined ratio. A further transistor, in series with one of the two main transistors, is paired with an image transistor with draws a matching current and supplies it to the reference terminal as the current component proportional to the output current. The constantvoltage generator is common to the base/emitter circuits of the two main transistors.

All the components referred to, with the possible exception of the voltage divider, may be incorporated in an integrated circuit whose substrate (e.g. a silicon wafer) may be grounded.

The above and other features of my invention will now be described in detail with reference to the enclosed drawing in which:

FIG. I is a circuit diagram showing a voltage stabilizer embodying the present invention; and

FIG. 2 is a more detailed diagram of a component of the stabilizer shown in block form in FIG. 1.

The voltage stabilizer depicted in FIG. 1 comprises an integrated-circuit network CI with grounded substrate including a control circuit A and a currentsensing circuit B. A supply voltage V, from a nonillustrated source of direct current is applied between ground and an input terminal 1; a load, shown as a d-c motor M, is energized by a current I at a voltage V on being connected between ground and an output terminal 2. A reference terminal 3 is tied to a tap of a voltage divider inserted between output terminal 2 and ground, this voltage divider consisting of a resistor R, in series with a preferably adjustable resistor R Terminals 1 and 2 are interconnected by two circuit branches 4, 5 including respective main NPN transistors T and T, along with associated emitter resistors R and R Transistor T though shown included in the control circuit A, may also be considered part of sensing circuit B along with its physically identical mate T,. The sensing circuit includes a further transistor T with emitter resistor R in series with transistor T and an image transistor T lying with its emitter resistor R in the current path 6 between terminals 1 and 3; transistors T and T are of PNP type. The two identical transistors T and T have their bases connected to the collector of transistor T so as to be traversed by identical currents I and 1 whose magnitude bears a predeter-v mined relationship with that of the output current I issuing from terminal 2. This output current splits into the actual load current I and a branch current I traversing voltage divider R R A constant-voltage generator CV, more futly described below with reference to FIG. 2, has two output leads 7, 8 respectively connected to terminals 2 and 3. Generator CV develops a substantially invariable voltage V across these two leads and energizes lead 8 with a substantially constant current I Thus, the current I issuing from terminal 3 represents the sum of currents l and 1 Since 1 V /R we can write out 0 u ('3 o/ o) Also, with I," K1 (K being a constant) in view of the pairing of transistors T T on the one hand, and T T on the other hand,

From equations (1) and (2) we obtain the following value for the load voltage V Under the assumed conditions, the first two terms of equation (3) are independent of input voltage V and load current 1 the amplitude of this constant voltage component being adjustable with the aid of resistor R,,.

The third term KR I of equation (3) is a voltage component proportional to load and is the equivalent of the voltage drop generated by current I across a negative resistance of amplitude KR The value of KR, should be less than or at most equal to the effective load resistance R in order to avoid instability. Since the constant K is independent of the setting of resistor R,,, adjustment of the latter varies the load voltage V without affecting the negative resistance.

As illustrated in FIG. 2, constant-voltage generator CV comprises a number of transistors T T and associated resistors R R Transistors T and T T and T as well as T and T represent successive 2- transistor amplifier stages generating a modified replica of voltage V which is to be held constant, this voltage being fed bck from lead 7 to the base of transistor T in series with transistor T and to the base of the latter transistor by way of resistor R The two transistors of each amplifier stage are connected in cascade, with the emitter of one transistor tied directly to the base of the other transistor. Transistors T T whose base/emitter resistances are of large value compared with resistor R form part of a temperature-compensating chain which neutralizes the effect of temperature variations upon the base/emitter resistances of the circuit as far as their effect upon the input voltage of amplifier stage T T is concerned. For a detailed mathematical analysis, reference is made to my copending application Ser. No. 283,421 filed on even date herewith.

The output voltage of transistor T is developed across resistor R, which is also connected to lead 7 so as to carry the voltage V Transistor T connected as a diode, is inserted between'ground and the emitter of transistor T in series with resistor R whose magnitude may therefore be reduced.

The collector of final transistor T is connected to the base of transistor T and through resistor R to the emitter thereof which in turn is tied to a conductor 9 interconnecting the bases of transistors T and T (the latter not having been illustrated in FIG. 2); resistor R lies between conductors 4 and 9 so that the series combination of this resistor and transistor T shunts the transistor T and its emitter resistor R Any change in the voltage V is communicated by way of the feedback loop including transistors T T to the base of transistor T which is of PNP type, in contradistinction to all the other transistors shown in FIG. 2; the polarity of the control voltage delivered by this feedback loop to the base of transistor T is such that the base/emitter voltage of transistor T varies in a sense minimizing the change in voltage V Thus, at least in first approximation, voltage V can be considered constant along with the current I traversing the transistor T It will be seen that the system according to my invention does not require the use of a constant-voltage and- /or constant-current source extraneous to the integrated network Cl.

Emitter resistors R R and R R are not essential but serve to reduce the effect of any residual disparity between the paired transistors T T or T T I claim:

1. A voltage stabilizer comprising:

an input terminal, an output terminal and a reference terminal, said input terminal being energizable by a grounded source of direct current, said output terminal being connectable to a grounded load;

a voltage divider inserted between said output terminal and ground, said reference terminal being tied to a tap on said voltage divider;

a generator of constant voltage connected between said output and reference terminals; and

current-sensing means connected between said input terminal on the one hand and said output and reference terminals on the other hand for supplying to said reference terminal a current component proportional to an output current issuing from said output terminal.

v 2. A voltage stabilizer as defined in claim I wherein said generator and said current-sensing means are part of an integrated network.

3. A voltage stabilizer as defined in claim Zwherein said integrated network is carried on a grounded substrate.

4. A voltage stabilizer as defined in claim I wherein said current-sensing means includes a first and a second transistor connected in two parallel branches between said input and output terminals for respectively delivering a first and a second component of the output current bearing a predetermined relationship, and a matching circuit in the second of said branches for supplying said proportional current component as the image of said second component.

5. A voltage stabilizer as defined in claim 4 wherein said matching circuit includes a further transistor in series with said second transistor and an image transistor connected in parallel with said further transistor.

6. A voltage stabilizer as defined in claim 4 wherein each of said first and second transistors has a base/emitter circuit connected across said generator.

7. A voltage stabilizer as defined in claim I wherein said generator includes circuitry for delivering a substantially constant reference current to said reference terminal.

Claims (7)

1. A voltage stabilizer comprising: an input terminal, an output terminal and a reference terminal, said input terminal being energizable by a grounded source of direct current, said output terminal being connectable to a grounded load; a voltage divider inserted between said output terminal anD ground, said reference terminal being tied to a tap on said voltage divider; a generator of constant voltage connected between said output and reference terminals; and current-sensing means connected between said input terminal on the one hand and said output and reference terminals on the other hand for supplying to said reference terminal a current component proportional to an output current issuing from said output terminal.

2. A voltage stabilizer as defined in claim 1 wherein said generator and said current-sensing means are part of an integrated network.

3. A voltage stabilizer as defined in claim 2 wherein said integrated network is carried on a grounded substrate.

4. A voltage stabilizer as defined in claim 1 wherein said current-sensing means includes a first and a second transistor connected in two parallel branches between said input and output terminals for respectively delivering a first and a second component of the output current bearing a predetermined relationship, and a matching circuit in the second of said branches for supplying said proportional current component as the image of said second component.

5. A voltage stabilizer as defined in claim 4 wherein said matching circuit includes a further transistor in series with said second transistor and an image transistor connected in parallel with said further transistor.

6. A voltage stabilizer as defined in claim 4 wherein each of said first and second transistors has a base/emitter circuit connected across said generator.

7. A voltage stabilizer as defined in claim 1 wherein said generator includes circuitry for delivering a substantially constant reference current to said reference terminal.

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