SU1261119A2 - Voltage-to-frequency converter - Google Patents

Abstract

The invention relates to electrical measuring equipment and can be used to measure the effective value of high frequency signals. A voltage to frequency converter containing capacitor 1, first and second current sources 2 and 3,, .J. f7 - W 12 first key 4, first and second comparators 5, 6, trigger 7, integrato 13 8, adder 9, reference voltage source 10, to expand the application area and improve accuracy, the third 11 and fourth 12 current sources are connected, through the second 13 and third 14 keys to the first output of the capacitor 1, the fifth 16 and sixth 17 current sources, the outputs of which through the fourth 18 and fifth fifth keys are connected to the current input of the integrator 8, the third comparator 20, the input of which is connected to the output of the integrator 8, and the output is connected to the control inputs of the third and the fourth keys directly, and to control to the input of the second and fifth keys; - through the element NOT 15. Invention - additional to auth.St. № 966892. 1. f-ly, 2 ill. (L with M

Description

one

1261

The invention relates to electrical measuring equipment, can be used to measure the effective value of high frequency signals, and is an improvement of the known device according to ed. St. No. 966892.

The purpose of the invention is to expand the scope and increase the accuracy of the conversion.

Figure 1 presents the structural diagram of the proposed Converter; figure 2 - timing diagrams.

The converter contains capacitor 1, first current source 2, second current source 3, first switch 4, first 5 and second 6 comparators, trigger 7, integrator 8, adder 9, voltage source 10, third 11 and fourth 12 current sources, second 13 and the third 14 keys, the element NOT 15, the fifth 16 and the sixth 17 current sources, the fourth 18 and the fifth 19 keys, the comparator 20.

The converter works as follows.

The integrator 8 integrates the sum of the voltage to be converted and one of the reference sources 16 or 17 of the current. When closed key 18 to the input of the integrator 8 receives the current source 16 (+1). In this case, at the output of the integrator 8, the voltage is defined as

)) (,

Where

,

oo

- integrating parameters

integrator circuit. In the adder 9, the output signal of the integrator 8 Ug (t) and the reference voltage U is applied to the source 10. Thus, the first input of the first comparator 5 is supplied with the voltage U (t), and the first input of the second comparator 6 - voltage

+ and ..

U, (t)

u, (t)

The conversion cycle consists of two cycles. In the first cycle, the trigger 7 is in the single state, 1Syuch 4 is open, i.e. capacitor 1 is charged with current +1 from the source 2 of the reference current.

The voltage at point C, equal to Uj (t), is applied to the second inputs of comparators 5 and 6 and varies under the action of sources 2, 11 of the current charging and discharging capacitors 1 (Cj), and source 11 is connected

1192

through the closed key 13. At the time when the voltages Ug (t) and Uj, (t) are equal, the second comparator 6 is triggered. The trigger 7 is switched to the zero state. As a result, the key 4 is closed and the second cycle of the device operation starts.

During the second clock cycle, the voltage U |., (T) decreases linearly under the action of sources 2, 3, and 7, since in this case capacitor 1 is recharged with current 1 and the voltage is equal at point C to the integrator’s output voltage triggers the comparator 5, transfer trigger 7 back to a single state. Then the cycle of operation is repeated. During the first cycle T conversion, the increment of the sawtooth voltage

kli- C,

Hi

 Cr

supplied to the second inputs of comparators 5 and 6, is equal to the sum of the reference voltage U and the output voltage of the integrator U | ,, (t). By this time

s, and "(t,);

loT, 1T

"... .j .-.

  1T y

 i ivdVy I

where and is the average value of the input voltage over the interval T, + T. Taking into account the equality of the capacitors C and C, have

-li yilL f II C, RC, o

The comparator 20, on reaching the output voltage, achieves a value equal to its threshold level. As a result of its operation, the opening of the keys 13 and 19, controlled through the element NOT 15, and the closing of the keys 18 and 14 occur. The latter are connected to the capacitor of the source 12 and 16 Current, forming currents of opposite sign relative to the currents of the sources 11 and 17. As a result, describing the integration in the first cycle of the converter, has the form

When the comparator 20 is triggered, its threshold level is automatically

3-

changes the sign to the opposite. Upon reaching this threshold level, the output voltage of the integrator 8 is triggered again, and therefore the switches 19, 18, 14, 13 return to their original position.

From this it follows that the current sources 17, 11, 12 do not affect the result of the formation of the time interval T (equal to the duration of the first conversion cycle. Output frequency

f -L -) l (. s. T, + T ,,

 l (t: ylci

-,

one

“P 2u: i: c:

The introduction of additional current sources, switches and a comparator made it possible to exclude the possibility of integrator 8 coming out of the linear region, and consequently, increased the accuracy of the conversion and made it possible to expand the application of the proposed converter to the region of signals with a constant component.

Claims (2)

1. Voltage to frequency converter according to auth.st. № 966892, about t l and,) s  ABOUT 15 20 25 0 194 in order to expand the field of application and improve the accuracy of the conversion, it introduced the third, fourth, fifth and sixth current sources, second, third, fourth and fifth keys, the element is NOT, and the third comparator, whose input is connected to the output the integrator, the output is connected to the control inputs of the third and fourth keys directly, and through the element NOT to the control inputs of the second and fifth keys, and the third and fourth current sources, respectively, through the second and third keys are connected to the first viewpoint to ndensatora, and fifth and sixth current sources respectively through the fourth and fifth keys are connected to the current input -integratora. 2. The converter according to claim 1, characterized in that the integrator is made on a resistor, an operational amplifier and an integrating capacitor, the first plate of which is connected to the output of the amplifier and is the output of the integrator, the second plate with the inverting input of the one-, radio amplifier, first output the resistor is the integrator current input, the second resistor output is the integrator input, and the non-inverting input of the op amp is connected to a common length. I ue Editor S. Lisin 9ui. g Compiled by V.Makhnanov Tehred I.Polovich Proofreader E.Sirohman Order 5245/58 Circulation 816 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Rauschska nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4