SU1385285A1 - Pulse-width modulator - Google Patents

Abstract

The invention relates to a pulse technique and can be used in measuring transducers of an analog signal. The invention makes it possible to increase the conversion accuracy by stabilizing the frequency of the output signal with changes in the input signal. For this purpose, an input signal conversion unit and two additional resistors, one of which is controlled, are added to a pulse-width modulator (W1-1). The PWM contains an integrator 1, a comparator 2, a controlled resistor 3, a resistor 4, an input signal conversion unit 5. Comparator 2 can be made at the operational amplifier, and the controlled resistor 3 can be in the form of a field effect transistor. The input signal conversion unit is in the form of a rectifier, which provides the possibility of converting a bipolar input signal. The device is provided with frequency independence from the size of the input signal, which causes high accuracy and speed of the proposed modulator. 1 hp f-ly, t il. § (L

Description

l // i / y

MuRetepne. refers to the impu- ation of the iicui technique and can be used in the AND-I (1 in the context of HT.TibFibix converters of the analog sitel.

The goal of H-foripeiIe is to improve the accuracy of the conversion: by stabilizing the frequency of the output signal during input

The drawing shows a functional diagram of a pulse width modulator.

The pulse width modulator (PWM) contains integrator 1, comparator 2, a controlled resistor 3, a resistor 4, an input signal conversion unit 5. In this case, integrator 1 and comparator 2 are connected in series, the output of comparator 2 is connected to the output device iiiHiioft and the first input of integrator 1, the second input of which is connected to the input bus and the input of the input signal conversion unit 5, the output of which is connected to the control input a controlled resistor 3 connected between the common bus and the second input of the comparator 2, which is connected through the resistor 4 to the output bus, and the controlled resistor 3 can be made in the form of an FET Integrator 1 can be made and an operational amplifier, whose input is invertiruyuschi soedi- yen through resistors to the input and vpsodnoy tires, and through a capacitor to its output. Comparator 2 can be made on an operational amplifier, the non-inverting input of which is connected through the first resistor to the integrator output, through the second resistor to its output, and the inverting input to the common bus through controlled resistor 3 and to the output 111 bus. The input signal conversion unit 5 can be made in the form of a rectifier, a scaling node, a quadrator, an adder. Performing an input signal conversion unit 5 in the form of a rectifier, and a controlled resistor 3 in the form of a field effect transistor, provides the ability to convert a two-pole input signal.

11IHM works as follows. The output voltage of the integrator 1 under the influence of the sum of the input voltage and alternating output

legs of the voltage of the computer apparatus of the sonar 2, the oscillations according to the linear pressure law between two levels of voltage -1 p and + and given by the resistive divider and the output voltage of the comparator 2.

The modulator operation algorithm is described by the following mathematical expressions.

and YOU BV t 9 ,,. ---. 1 - and „,

(one)

and OUT + UBX „, J.-:

-t, - Un,

- constant integrator time;

- the duration of the positive and negative half cycles of the output QIHM pulses; - output voltage and

input device. eni (1) we find the period of the pulses:

t - t + t - 2up L 1sh -.

(2)

2 Un-f

in their

 I -

and Dtl. to determine the voltage e and e on the inverting and non-inverting inputs of the comparator 2 we write

 e

.ii. R2

-th-U1x R3 R4

where R1, R2,

R3, R4 is the resistance value of the resistors of the comparator 2 and the resistors 3, 4. Then for e you can write

4 Bl - Ur, R2,. Rr + R2

The voltage at the inverting input of the comparator 2 at R3.; R4 is

R

I, x

 RV

/ -J -., G „. KZ

Equal l (P and, that SOGGVRT-s moment at the geger. P; in the form of output south () of the voltage of paraparator 2, we obtain the expression of a mode / 1 Op,

those.

Ueb.x-RI - Un-R2 and R3

, -.

Due to the fact that 4141 field-effect transistor, on which a controlled resistor is made, has a natural quadraticity of its characteristic and the control input of the controlled resistor 3 is connected to the input bus of the device, the following equality

R3 К-и, (6)

where K is the coefficient of gross proportional transistor.

Substituting expressions (3) and (6) into (2), we have:

-cBL and b 1c11b2)

2G R4 J

- I - fc l

Provided

R1 - R4

to

L

with

Formula (7) sgzodits to glory

(9)

T 2C.- | f

with

ten

15

20

those. As can be seen from formula (9), if equality (8) is observed, the period; 1, and hence the frequency of operation, fie depends on the input signal's vetichin. The independence of the UIKM frequency from the size of the input signal is determined by the high accuracy and speed of the SW.

Claims (1)

1. A pulse width modulator containing an integrator and a comparator connected in series, the output of which is connected to the output bus and the first input of the integrator, the second input of which is connected to the input bus, distinguishing, SI topics 25 7) 35 that, in order to increase accuracy, an input signal conversion unit and two additional resistors, one of which is made controllable, are additionally introduced, the input bus is connected to the control input of the controlled resistor through the input signal conversion unit, the comparator output is connected via the second additional a resistor with its second input, which through a controlled resistor is connected to the common bus. 2, The modulator according to claim 1, of which is a control resistor in the form of a field-effect transistor.