SU966892A1 - Voltage-to-frequency converter - Google Patents

Description

(54) VOLTAGE CONVERTER IN FREQUENCY

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 is known with a quadratic conversion function, the principle of which is based on the cyclic charge of the integrator by the sum of the input and reference voltages and the discharge of the same integrator as the differences between these voltages.

This device has a low output frequency and therefore cannot be used to convert high frequency signals. The low output frequency of the FNC is due to the inertia of the amplifier, on which the integrator is made, and the response delay of the switching elements.

A known voltage converter S is a frequency, comprising an integrator, the input of which is connected to the input bus of the converter, and the output to the first input of the first comparator, the source of the reference voltage and the key

The disadvantage of such a converter is the limited frequency range, which is caused by the necessity of periodically resetting the integrator with a frequency equal to the output frequency.

The purpose of the invention is to expand the frequency range.

The goal is achieved by the fact that in a known 10-strand-to-frequency converter, which contains an integrator, the input of which is connected to the input bus of the converter, and the output is connected to the first input of the first comparator, the source

15 of the reference voltage and a key, the adder, the second comparison device, the trigger, the first and second reference current sources and the capacitor are entered; the second comparing device, the second inputs of the first and second comparing devices are connected to the capacitor, the second capacitor terminal is connected to the common bus of the device, the output of the first reference current source and through 30 the key - output of the second source

the reference current, the outputs of the first and second comparison devices are connected respectively to the inputs of setup 1 and O of the trigger, the output of the trigger is connected to the control input of the key.

Figure 1 shows the scheme of the proposed Converter; 2, timing diagrams for his work.

The device comprises an integrator 1 voltage source 2, an adder 3, two comparing devices 4 and 5, a capacitor 6, two current sources 7 and 8, a key 9 and a trigger 10.

The input of the integrator 1 is connected to the input bus device, and the output from the first input of the first comparing device 4 and the first input of the adder 3 ,. the second input of which is connected to the output of the voltage source 2, the output of the adder 3 is connected to the first input of the second comparison device 5, the second inputs of the wallpaper of the comparison devices are connected to one of the terminals of the capacitor b, the second terminal of the capacitor b is connected to the common bus of the device the reference current 7 and through the switch 9 with the output of the second source of reference current 8, the output of the first comparing device 4 is connected to the installation input 1 of the trigger 10, and the output of the second comparing device 5 is connected to the input With the setting O of the trigger 10, the direct output of the trigger 10 is connected to the output bus of the device, and the inverse output of the trigger 10 is connected to the control input of the key 9.

The device works as follows.

In general, the output voltage of the integrator 1 is determined by the expression

A, (t) dt ,, O)

where is the integrator time constant.

When-output Od signal of integrator 1 is a sinusoidal voltage of Family (Fig. 2), in adder 3, the output signal of integrator 1 U is combined with reference voltage U. So, the first input of the first comparator 4 is supplied DC, which is the integral value of the input signal U (t), and the first input of the second comparator device 5 is the voltage

The A Uo conversion cycle consists of

two cycles. In the first cycle, the trigger 10 is in a single state.

Key 9 is open, i.e. capacitor b is charged by current +1 from the current source 7.

The voltage at point C (Fig. 1 and Fig. 2), which is applied to the second inputs of the comparison devices 4, and 5, rises linearly until its output voltage is equal to 3 U. At the time of voltage equality Ug U, the second comparing device 5, switching trigger 10 to the zero state. As a result, the key 9 closes and the second cycle of operation of the device begins.

During the second cycle, the voltage at point С Up linearly decreases, since in this case capacitor b is recharged with current –21 from the second reference current source 8. At the moment of equal voltage at point C, the output voltage of the integrator lUt- Uf comparing device 4, translating again trigger 10 into one state. Then the cycle of operation is repeated.

During the time of the first T conversion cycle (Fig. 2) the increment of the sawtooth voltage U

and

f - (С С

supplied to the second inputs of the comparison devices 4 and 5, is equal to the sum of the reference voltage U and the increment of the integral value of the input voltage during this cycle

I T

(2)

and.

where C is the capacitance of the capacitor b; Uv is the input voltage; Ti - KcS „- constant time

integrator 1.

Dialogically, for the second conversion cycle, we can write the equation

-and...

(3)

Having solved equation (2) and- (3) with respect to T and T.j, an expression is obtained. for the output frequency of the fnp f. -) -felcf- () VV iloUo / C.

(-)

iUoIoC ZloUo-Cj

Q OR, assuming that the capacitors of the capacitor of the integrator (C „) and the capacitor b (C) are equal, receive

x

C) (4)

h

one

where S -711 t g - constant coefficient

 phycent defined by the PNC parameters;

Rw

- resistance of the integrator.

In the proposed converter, the integrator operates only at the input signal frequency and does not participate in the formation of the sawtooth voltage, as a result of which the frequency range is expanded, and the requirements for the integrator are reduced in speed and dynamic range.

Claims (2)

1. US patent number 3780273, -. C 06 G 7/16, 18.12.78. 2. Marg Shin, AI, Shakhov .E.K.,. 5; Ch ndin V.M. Transducers of electrical parameters for the monitoring and measurement system. M., Energie,; 1976, p., Fig.3-31 (prototype). / t V a t / V / g  : 5A Uo