SU750673A1 - Scale dc voltage converter - Google Patents

Description

(54) SCALING CONSTANT INVERTER The invention is intended to proportionally vary the magnitude of the input voltage and can be used in precision measuring instruments, control and regulating electrical devices. The known passive large-scale DC-DC converters on resistors have the following disadvantages: their transfer coefficient is less than unity, they have low accuracy and stability of the conversion even when using thermostats. Active scale voltage converters are also known, which contain a measuring amplifier and a resistor voltage divider, forming a series negative voltage feedback circuit of voltage 2. Such converters also have a large error and instability due to manufacturing inaccuracy and unstable voltage divider resistors. This disadvantage is further aggravated by the need for high-power resistors to obtain high voltages. In particular, precision resistors such as MRH and MVSG have an accuracy of no more than O, O2%, and printing resistors cannot be used at high voltages. Both those and others have insufficient stability. The aim of the invention is to improve the accuracy and stability of the large-scale DC voltage conversion. This goal is achieved by the fact that a known converter includes: an inductive divider, the primary winding of which is connected to an alternating voltage generator, and two secondary windings connected oppositely and in series, the first of which are connected by the ends of the measuring amplifier, and the second - in the input circuit; . the mismatch amplifier, the input of which is connected to the branch, is formed by the successive connection of the second winding of the inductive divider and the shoulder of the resistor divider common to the input and output circuit of the measuring

an amplifier, an actuator connected to the output of the error amplifier and a common shoulder of a resistor divider, which is made variable.

The drawing shows a constant voltage converter. The converter contains input terminals 1 and 2, an inductive AC voltage divider (IDPN) 3 with a primary winding 4 fed from an alternating voltage generator S, and secondary windings 6 and 7 having a common point and connected in opposite and in series. The measuring amplifier 8 contains a two-arm voltage divider of resistors 9 and 10 in the negative feedback (OOS) circuit. One arm 9 of the divider is fully adjustable and connected to the common point of the secondary windings IDPN and the common point of the measuring amplifier 8, and the other arm 1O - unregulated . Amplifier 8 is encompassed by a series of OOS over voltage. Between the shoulders 9 and 1O of the resistor divider, the winding 6 of the IDPN is connected, which together with them forms the output circuit of the amplifier. In the input circuit of the amplifier between the input terminal of the converter and the adjustable shoulder 9 is included the second winding 7 IDPN.

The adjustable shoulder 9 of the resistor voltage divider is connected with the actuator, an extension body 11, which is connected to the output of the error amplifier 12, and the latter is connected to the branch formed by the series connection of the adjustable shoulder 9 and the second winding 7 of IDPN.

Converter output terminals

marked 13 and 14.

Since the converter is covered by a series negative voltage feedback, with a sufficiently large input, the resistance of the amplifier 8 by a drop in the DC voltage on the winding 7 can be neglected, and then the relationship between the output and input DC voltages will be by relation

and .i (1)

R, - respectively

U t)

resistance of resistors 9,10

and windings 6.

Since the windings 6 and 7 of the inductive divider 3 are connected in opposite, the alternating voltage of the resistor 9 will be switched in antiphase to the EMF on the winding 7.

The difference between them D U 9,3 J 2) will be amplified by the error amplifier 12 and fed to the executive body 11. The latter affects the resistance value of the resistor 9 as long as. will not be close to zero.

Since for the output circuit of amplifier 8 of inductive divider 3, the following ratios are valid

and"-.

(3)

(four)

where Wj, and NX / is the number of turns in the coils. 6 and 7, respectively, and Е, is the EMF in coil 6, substituted the first parts of these equalities into equation (2), counting the difference Л Ur ,, equal to zero and reducing by F, get

RC

t

(five)

L,

Substituting the opposite inverse of equality (5) to equality (1), we get

:

 , (6)

Njv

Thus, the output voltage of the converter is directly proportional to the ratio of the number of turns IDPN, KOTojioe can be performed with very high accuracy and is resistant to destabilizing factors: temperature change, supply voltage, aging, etc. Accuracy and stability are determined mainly by the parameters of the input signal.

The mode of operation of the measuring amplifier 8 is chosen so that its AC resistance on the output terminal side is close to zero. This circumstance, as well as the high input resistance of the amplifier and the reduction of the difference in the input circuit to zero, practically exclude the influence of the alternating voltage on the accuracy of the large-scale conversion of the constant voltage, and

Claims (1)

Claim 1. A large-scale dc voltage converter • comprising a measuring amplifier, a two-arm resistor divider, one of the arms of which is common to the input and output circuits of the amplifier, and a series negative voltage feedback circuit formed by the arms of the resistor divider, characterized in that, in order to increase accuracy and stability, the converter contains an inductive divider, the primary winding of which is connected to an alternating voltage generator 5, and two secondary circuits the swings are connected in an opposite and sequential manner, one of which between the arms of the resistor divider is in the output circuit of the measuring amplifier, and the second is in its input circuit 10, as well as a mismatch amplifier connected by an input to the serial branch of the input circuit of the measuring amplifier formed by the common arm of the resistor divider and a second winding of the inductive divider, and an actuator connected to the output of the mismatch amplifier and the common arm of the resistor divider, which is made variable. 20 2. The converter according to π. 1, distinguished by the fact that, in order to set different values of the scale conversion, the secondary windings of the inductive divider of an alternating voltage are made sectionalized and the sections are equipped with switching elements.