DE1270118B - Direct current impedance converter for generating an impressed current proportional to an input voltage - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

Number:
File number:
Registration date:
Display day:

H03f

German class: 21 a2- 18/02

P 12 70 118.7-31 October 29, 1965 June 12, 1968

The invention relates to a direct current impedance converter constructed with transistors for generation an impressed current proportional to an input voltage.

To a z. B. from a potentiometer tapped DC voltage into a correct sign and to convert exactly proportional impressed direct current, direct current measuring amplifiers are used, which work according to the chopper principle, i.e. which chop up the DC voltage into one Convert alternating voltage and then amplify it on the alternating current side. Such impedance converters are relative laborious.

There are amplifier circuits are known in which two complementary, at their bases opposite one first input terminal oppositely biased transistors with their emitters via emitter series resistors are connected to each other and the input voltage with a second input terminal at the connection point of the emitter resistors and where a consumer in one to The common part of the emitter-collector circuits of the two transistors led to the connection point can be switched on. However, this is not an impedance converter for generating an impressed Current, but about normal amplifiers, where the output current is not within wide limits is "impressed" independently of the size of the consumer resistance. The base bias becomes in this amplifier circuit derived in the usual way through a suitable network from the supply voltage of the transistors.

There are also push-pull B amplifier with two similar PNP transistors known, the Bases of the transistors an input AC voltage is supplied in phase opposition. Between the collectors of the transistors, the output transformer with push-pull windings is switched on. One Direct current source supplies the collector side, a second battery with lower voltage is used to open the transistors a little and to avoid distortion with a small signal. Collectors, The emitter and the bases are coupled in a direct current manner by means of resistors. This arrangement is neither determined nor suitable for assigning an impressed current proportional to an input voltage produce.

In contrast, the invention is based on the object of a simply constructed transistor impedance converter for DC voltages to create the detour via a chopping and AC amplification avoids.

DC impedance converter for generating an impressed current proportional to a Input voltage

Applicant:

Remote control devices Zachariä-Oelsch-Meier, ίο 1000 Berlin 47, Jahnstr. 68-72

Named as inventor:

Dipl.-Ing. Klaus Thiele, 8581 Oberailsfeld

The invention is characterized by the combination of the following, each known per se Characteristics:

a) Two complementary, oppositely biased at their bases compared to a first input terminal Transistors are connected to one another with their emitters via emitter resistors, the input voltage is connected to a second input terminal at the connection point the emitter resistors on, and a consumer is in one led to the connection point common part of the emitter-collector circuits of the two transistors can be switched on.

b) for generating the base bias voltage, one or more separate ones are galvanically separated from the supply voltages of the transistors Voltage sources provided.

In such a circuit, one of the transistors is PNP and the other is NPN. The emitter and collector of the two transistors are accordingly connected to opposite supply voltages. The bases are also biased in opposite directions. If now the input voltage to the connection point of the emitter series resistors is applied, the two transistors are driven in opposite directions. The current through one emitter series resistor grows and the current through the other emitter series resistor decreases, and the voltage drop across the emitter series resistors changes accordingly, so that the The connection point of the emitter series resistors follows the potential of the second input terminal. Since the Transistors have a high current gain, the required to drive the transistors can be

809 559/351

3 4

Lent voltage can be practically neglected, so Fl g. 4 shows a modification of the arrangement of FIG

that the change of the au emitter voltage resistors Fig. 3, at which def zero point at one end

falling voltages and the potentiometer lying through it;

flowing currents an exact replica of the input F i g. 5 shows an arrangement of the type of FIG. 3,

voltage are. In that to the connection point s at which the supply voltage of the potentiometer

guided common part of the emitter-collector and the BasisVorspanhüng are stabilized;

Circuits of the two transistors must then have a current F i g. 6 shows a modification of the arrangement

flow, which according to size and sign of FIG. 5;

Difference in the flow in the emitter series resistors. Fig. 7 shows an arrangement similar to Fig. 4

is exactly proportional to the currents. When using io voltages stabilized by Zener diodes,

one of the collector circuit voltages galvanically In FIG. 1, T ₁ and T _{2 are} two complementary ones

separate auxiliary voltage source for generating the transistors. One is a PNP transistor

Base biasing occurs the surprising effect and the other is an NPN transistor. The transistors

that the output current is "impressed", ie in T _1. , T ₂ have emitter series resistors 10 and 12, respectively,

wide limits - roughly between almost 0 and 15 These transistor resistors 10, 12 are at the point

100 ohms - the size of the consumer resistor 14 connected to each other. Between the colleges

status is independent, that is with the mentioned gates of the transistors there is a GieiehStföül food

Previously known push-pull circuits are not the case with a delay source with a 16 »In

and cannot be reached there either. The cause of Fig. 1 is the supply voltage source by two

the load independence of the inventive switch 20 batteries 18, 20 shown, which are connected in series at 16

The main reason for this is that transistors are switched by their nature. In this way, the tears are

Have "pentodic character". According to the sistören T ₁ , T% voltages opposite Polafl -

Base current modulated collector current is so good fäf, based on the »Mitteflaäzapfüng« 16, · at, between

as independent of the points 14 and 16 located on the collector, there is a consumer

Tension. 25 22 ünd / ödef an instrument 24.

If one ensures that the distribution of the I _{n is} similar to a Späünuügsqüelle with

Collector voltages are not provided by a counter-coupling of a center tap 26, - the between

Resistances of the circuit on the Basisvorspannund the bases of the transistors T ^ T ₂ lies. In Fig. 1

gene can have an effect, this constant current remains - this voltage source is provided by two batteries 28,

property of the transistor. This rear 30 30 shown, which are connected in series at 26 iü, so

effect is according to the invention by biasing that _a n defl bases of the two transistors T ₁ and T ₂ -

of the bases by means of a polarity opposite to that of the supply voltage

galvanically separated separate power source connected to point 26.

avoided. The circuit is largely independent

The second of the characteristics of the transistors and the ₃₅ 32 Eiägängsspännung a U verbünden.-

Supply voltages, as there is a very strong counter-coupling ElügangskletHine 34 of the Em'gäügs Späünung

treatment takes place. Accordingly, the achievable is the Püüktl4 alliances.

^ Voltage gain at most one. It acts when the input span is zero - thin

sicfihalso just an impedance converter. msä Completely symmetrical relationships. · Since the

In contrast to the previously mentioned 40 Tiäfisistoren Z ^ and T ₂ complementary to each other

When the push-pull B amplifier works, the circuit types are

According to the invention with complementary transistors voltages controlled in the same way. By

(PNP and NPN), carries input current and input the EmitteirvöfWidersiäüde 10, 12 flowing currents

voltage in phase to the bases, switches the are equal * with one current to point 14 MH-

Outgoing consumers not to the Kollekforelek- 45 and the other from point 14 is directed away, Deffl-

Troden, but closes it between the foot - stream flows wiggle in the Voüt consumer

point of two collector direct voltage sources and 22 formed common part of the "Effiitter-KöHek-

the middle of the emitter series resistors. In addition, the gate circuits of the transistors T ₁ , T ₂ .

are the basic DC voltages in the invention, If äff the terminals 32, 34 an Ekgäfigsspan-

which open the pair of Köllektorpaar in terms of power in 50 mffig Ü _{e is} put, so the transistors T ₁

ner way with the two collector-emitter circuits and T _ä driven in opposite directions. Def current, e.g. B.

coupled. through the resistance IO becomes less; and the

The von def Veisorgüngsäpännüng galvanically gestfötii by the resistor 12 becomes stronger, and

The separated auxiliary voltage can, if necessary, be divided into two ζ ^ _{3Γ so} that you see the potential of the point '14

Capable of being explored in ways. Namely, it can shift 55 speaking of the Mngängsspanäüng U _e .

m a * to generate the Bäsis pre-tension die- ^ a _0n i _S t the tension on the Bäsis-EMtter line

nenden DC source a transmitter potentiometer of the transistor again errs essentially zero, ways

äidiegeny that not its tap on the said high current gain of the transistor of both

Connection point. for example 100 are the basis emitter stream and the

Some exemplary embodiments of the invention are practical too

ift de «drawings shown and in the following, the changes to the voltage

Bescfefieben, äbfälles äö deü resistors 10, 12 are therefore a

1 shows the principle of the true image of the input voltage U. Weüö according to the invention

Circuit; the Siforn dufcb the resistance 10 mine and the

Fig, 2 shows a circuit with a power supply? 65 dutch the resistance 12 becomes greater, then must

F ί g. 3 shows a circuit in which the on-one corresponds to the difference * current / overf. the

gäögsspäünuflg tapped at a potentiometer consumer 22 and the instrument 24 flow », Di © -

id this current is proportional to the applied voltage

U ₆ and - within the limits of the switching elements - regardless of the resistance R of the consumer 22 or the instrument 24,

T __

Ue re

(R _e = size of the emitter series resistor).

The voltage between the collectors of the transistors T ₁ and T ₂ will be at least to

Select.

The voltage U ₂ between the bases of the transistors T ₁ , T _{2 is} chosen at least

"2 ⁼ '■ max' ** - e ?

where I _{max is} the maximum expected applied current.

A voltage that opens the transistors must always be present at the bases, and the The voltage drop at the consumer cannot be greater than that at the emitter-collector circuit applied voltage.

F i g. 2 shows a circuit according to the invention including a specific embodiment of the power supply unit. The circuit shows the types and dimensions of the switching elements. Same parts are denoted by the same reference numerals as in FIG. 2.

The power supply 35 contains a mains transformer 36 with a primary winding 38 and a first secondary winding 40 as well as a second secondary winding 42. The winding 40 has a center tap 44, so that two winding halves result. The voltages tapped thereon are rectified by rectifiers 46, 48 and charge capacitors 50, 52, which are thus connected to one another at the center tap 44. The tap 44 corresponds to point 16 of FIG. 1. The DC supply voltages of the transistors T ₁ , T _{2 are} taken from the capacitors 50, 52.

A capacitor 56 is also connected to the winding 42 via a rectifier 54. In parallel with that Capacitor 56 are two resistors 58, 60, between which one corresponding to point 26 Center tap 62 is formed. This is where the first input terminal for the input voltage is located.

Since the arrangement is largely insensitive to mains voltage fluctuations or the like, you get along with a very simple power supply, as described.

In the arrangement according to FIG. 3 the function of the resistors 58,60 to form the virtual Center tap 62 and the function of a transmitter potentiometer for the input voltage with each other united. In parallel with the capacitor 56 is a potentiometer 64 with upstream and downstream Fixed resistors 66 and 68. When the potentiometer wiper 70 connected to point 14 turns is in its central position, then one has the conditions as in FIG. 2 with one input voltage zero. A shift of the potentiometer wiper 70 out of this central position corresponds to the application a corresponding input voltage. The "first input terminal" in the sense of the invention is the center of the potentiometer 64, the "second input terminal" is the tap 70.

According to FIG. 4, however, the arrangement can also be so be taken * that the potentiometer wiper 72 in the balanced state at one end of the potentiometer 74 stands. This is useful if only input voltages one polarity occur and you then of course the entire travel of the potentiometer slider 72 wants to exploit. For this purpose, the potentiometer 74 is a resistor 76 in front of and a resistor 78 is connected, and the size of the resistor 76 plus the resistance of the potentiometer 74 is equal to the size of resistor 78.

If, according to FIG. 3 and 4 the encoder potentiometer 64 and 74 directly also for formation the center tap 26 is used, then it makes sense to stabilize the voltage from the capacitor 56. This is done according to FIG. 5 by means of a Zener diode 80 and a stabilization resistor 82. The Zener diode 80 is parallel to the potentiometer 64 with the resistors 66 and 68 connected upstream and downstream.

Instead of a single Zener diode parallel to the entire resistor arrangement, you can do that too Potentiometer 64 is provided with a center tap 84, which corresponds to point 26, and two Zener diodes 86 and 88 parallel to each half of the potentiometer 64 and one of the series resistors 66 or 68 provide.

F i g. 7 shows an arrangement with a potentiometer 90, the slider of which is in the starting position is at the bottom of the potentiometer. A series resistor is designated by 92. The potentiometer 90 with resistor 92 corresponds to potentiometer 74 and resistor 76 of FIG. 4. A Zener diode 94 stabilizes the voltage applied to it. A resistor 78 corresponding to Resistance can be dispensed with. For this purpose, a corresponding voltage is applied to a second Zener diode 96 held.

Claims (4)

Patent claims: 1. Direct current impedance converter built with transistors to generate an impressed Current proportional to an input voltage, characterized by the combination of the following, each individually known features: _{a) Two complementary transistors (T 1} , T ₂ ) which are biased in opposite directions at their bases with respect to a first input terminal (32) are connected to one another with their emitters via emitter resistors (10, 12), The input voltage (U _e ) is connected to a second input terminal (34) at the connection point (14) of the emitter resistors (10, 12), and a consumer (22) is in a common part of the emitters that is led to the connection point (14) -Collector circuits of the two transistors (T ₁ , T ₂ ) can be switched on; b) one or more separate voltage sources (28, 30; 42) which are galvanically separated from the supply voltages (18, 20; 40) of the transistors (T ₁ , T _{2) are provided for generating the base bias voltages.} 2. Impedance converter according to claim 1, characterized in that one for generating the Base bias DC power source a transmitter potentiometer (64) is present, which has its tap (70) at said connection point (14) is applied. 3. Impedance converter according to claim 2, characterized in that as a voltage source for generation the base bias a separate winding (42) of a power transformer with a Rectifier (57) and smoothing capacitor (56) is provided that this voltage source has two Zener diodes (86, 88) connected in series are connected in parallel and that the transmitter potentiometer (64) parallel to the Zener diodes on the voltage source and with a center tap (84) is connected to the connection point of the Zener diodes (Fig. 6). 4. Impedance converter according to claim 2, characterized in that as a voltage source for generation the basic preload a separate one Winding of a mains transformer with rectifier and smoothing capacitor is provided that two series-connected Zener diodes (94, 96) are connected in parallel to this voltage source and that the transmitter potentiometer (90) is parallel to one of the Zener diodes (94) (Fig. 7). Considered publications: German Patent No. 1,042,028; British Patent No. 778,460; Book R. F. Shea, "Transistortechnik", 1960, p. 123; "Funk-Technik" magazine, No. 6, 1963, March, p. 179; Electronic Industries magazine, June 1961,
P. 163; Radio & Television News magazine, 1956,
February, p. 40. 1 sheet of drawings 809 559/351 5.68 © Bimdesdruckerei Berlin