CS210997B1 - Wiring to compensate for the influence of the reference resistance temperature - Google Patents

Abstract

Circuit for compensating the influence of the temperature of the reference resistor. The invention relates to a circuit that eliminates the influence of the temperature of the reference resistor in current stabilizers with an adjustable current value. The invention solves the replacement of complex systems with thermostatic maintenance of the temperature of the reference resistor. The essence of the circuit is that a divider of two resistors is connected in parallel to the reference resistor in series with a reference voltage source, where the center of the divider is connected to the inverting input of the deviation amplifier, while the windings of the first resistor of the divider and the reference resistor are thermally connected. The invention is intended for current sources with high stabilization efficiency.

Description

BACKGROUND OF THE INVENTION The present invention relates to circuitry for compensating the effect of a reference resistance temperature in adjustable current value stabilizers.

In the case of current stabilizers, the load current is controlled by the voltage obtained by comparing the reference voltage with the voltage drop caused by the current flow through a precise, so-called reference resistance. Due to its non-zero temperature coefficient, the stability of the reference resistance is mainly influenced by the warming caused by the power dissipation in the resistance itself. This circumstance is particularly important when it is a source of variable stabilized current. It can be deduced that the relative change in the value of the reference resistance AR / R is proportional to the square of the stabilized current ratio.

This change in resistance takes place with the thermal time constant of the entire system, and this causes an undesired time change in the new stabilized current set point. Therefore, prior methods of eliminating this effect have been to maintain resistance to a circulating liquid thermostat. The disadvantages of this method are that the stabilization of the reference resistance temperature is not only costly, but also requires considerable space from a constructional point of view. Furthermore, considerable time is required to stabilize the temperatures, especially with larger volumes of coolant.

These previous disadvantages are eliminated by the circuitry to compensate for the effect of the reference resistor temperature of the current stabilizer, where the reference resistor connected to the common conductor is connected via a load resistor to the deviation amplifier output. The principle is that parallel to the reference resistor is connected a divider of two resistors in series with the reference voltage source and the center of the divider is connected to the inverting input of the deviation amplifier, the winding of the first resistor of the divider and the reference resistor is thermally coupled, for example and on a common thermally conductive carrier.

The main advantage of the invention is the constructional and circumferential simplicity, which replaces the considerably more complicated and voluminous space constructions with thermostats, thus bringing a considerable reduction in production costs. At the same time, the circuit according to the invention reduces the settling time of the current stabilizer consumption parameters.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated in greater detail by the accompanying drawing, in which the basic connection of the compensating part of the stabilizer is indicated.

The wiring example shows the compensating part of the stabilizer. The deviation amplifier i which supplies the current I is connected to the common conductor via a load resistor & _z and a reference resistor Rp. The non-inverting input of the deviation amplifier 1 is also connected to a common conductor. Its inverting input is connected to the center of the divider of the two resistors Rj. The first resistor Rj is connected to the reference and load resistor node Rp, R _z · Resistor R is simultaneously in thermal contact with the reference resistor Rp. The second resistor Rj of the divider is connected to a reference voltage source 2 Up whose second pole is connected to a common conductor.

The functional operation of the wiring can be justified as follows:

The current I passes through a load resistor R _z and a reference resistor Rp connected in series. Then, at the center of the divider consisting of the resistors R, and Rj, the voltage U shall be:

AU

I ^R r

R, R,

This voltage is very small due to the polarity of the reference voltage and is actually the control voltage for the feedback amplifier 2 of the power stage which controls the current I to the load. Assuming it is approximately AU = 0, then:

-¾

Obviously, if it is ensured that the relative resistance on the first resistor gj coincides with the change in the reference resistor R1, the value of the second fraction remains unchanged and thus the value of the current I remains unaffected by the change in the reference resistor R? with temperature. These common dependencies are shown in dashed lines in the figure.

The joint thermal coupling of the two resistors gj, g ₂ is effected, for example, by winding the two resistors Rj,

R? side by side or on top of one another and on one thermally conductive carrier. In order to ensure a very tight thermal bond between the windings of the two resistors R1 and R1, the windings of each resistor are divided into a plurality of sections. The coil support is formed with the same number of chambers. In each chamber there is a winding of one section of resistor g _p and one section of the first resistor gj of the divider. The resistance wire for both resistors g1, g1 is preferably selected from the same diameter and from the same wire.

This achieves the same temperature dependence for the two resistors R, Rp. In order to satisfy the practical requirements of setting a reference resistance value gp substantially lower than that of the first divider resistor gj, the winding of the sections of the two resistors is connected so that the individual sections of the reference resistor _Rp are connected in parallel. connected serially.

If the temperature of the cell carrier changes due to a change in current I or a change in ambient temperature, the value of the reference resistance gp is changed according to the expression.

where t _fcR - is the temperature coefficient of the resistance wire of the winding R _p

AT _r - is the warming of the reference resistance _R o - the original value of the reference resistance r

A similar expression applies to the resistance gj:

^R 1 = (1 + t kR)

AT ') ^R 1

When using the same wire, it can be assumed that t ^ = t, ^ and due to the tight thermal bonding, the heating is the same for both cases. AT _R = AT _R , then the ratio of the two resistors at the new temperature is equal to the ratio of the original values: ^r '

independently of the temperature as expected. As a result, the current value remains constant and hence the reference resistance warming has no effect on the current value.

Claims (1)

SUBJECT OF THE INVENTION Circuit arrangement for temperature compensation of the reference resistance current stabilizer, wherein the reference resistor is connected to a common conductor is connected via zatěžovaoí resistor to the output of error amplifier, characterized in that parallel to the reference resistance (R _R) is connected to the divider consisting of two resistors (R₁, and Ri) in series with the source (2) of the reference voltage and the center divider is connected to the inverting input of the amplifier (1) offset, wherein the windings of the first resistor (s _1), the divider and the reference resistor _(Η ρ) are thermally connected, for example by winding on itself or side by side and located on a common thermally conductive carrier.