SU1515343A1 - D.c. amplifier - Google Patents

Abstract

The invention relates to electronics. The purpose of the invention is to improve accuracy by suppressing impulse noise. Achieving this goal is achieved by using a change in the switching frequency and suppressing low-frequency pulsed electrical noise. An additional advantage of the amplifier is the gating of the frequency control of the reference signal generator during the duration of the impulse noise, which prevents the possibility of tuning the switching frequency caused by the impulse rather than the narrowband interference. 1 hp f-ly. 3 il.

Description

The invention relates to electronics and can be used in amplifier technology to amplify DC signals.

The purpose of the invention is to improve the accuracy by suppressing impulse noise.

FIG. Figure 1 shows a structural electrical circuit of a DC amplifier; in fig. 2 is a timing diagram of the operation of the DC amplifier; in fig. 3 is a frequency converter - voltage diagram, an example of implementation.

The DC amplifier contains a modulator 1, an AC amplifier 2, a demodulator 3, a low-pass filter 4, a generator of 5 reference signals, a switch 6, an amplifier 7, an attenuator 8, a comparison block 9, a frequency-voltage converter 10, an input 11 low pass filter.

a first band-pass filter 12, a first amplitude detector 13, a second band-pass filter 14, a second amplitude detector 15, a comparison unit 16 and an output switch 17.

The DC amplifier operates as follows.

The input signal (Fig. 2a) is fed to modulator 1, where it is modulated in amplitude by a signal with a frequency f. ,, supplied to modulator 1 with a geter.

Nerator 5. The amplitude modulated signal is applied to the AC amplifier 2 (Fig. 2d). From the amplifier output, an alternating voltage signal is applied to demodulator 3 and to rectifier 7 with a constant time D constant of filter 4 time. The output signal of rectifier 7 and “a” (Fig. 2e) is fed through an attenuator 8 to one block input 9 comparisons, on the second input of which

ate

ate

with

4 WITH

output signal Up is received from filter 4 Fig. 2) with the help of an attenuator 8 the value Ujj, ri is set less than Ugi, x the value dU U gj ,, - KU

all

where K is the attenuation coefficient of the attenuator 8, and K 1.

Tsa FIG. 26 shows the interference; FIG. 2c - input signal + noise.

The AI value determines the response threshold of the comparator unit and, in order to increase the noise immunity of the amplifier, varies in proportion to the change in the input signal. The output signal of the comparator unit 9 is fed to the control input of the key 6. The output signal of the generator 5 of the reference signals is fed through the key 6 to the control input of the demodulator 3 with the frequency of the demodulation.

The modulated signal is fed to a low-pass filter 4 to amplify the amplified signal in proportion to the input signal.

The device with deGstvii and fflylnyh interference (see the timing diagram of Fig. 2 t t, - t, t t - t) works as follows. The input signal (Fig. 2c) is fed to the modulator

15343,)

The control signal is applied to the frequency-voltage converter 10 at the converter and shuts it down for the duration of the impulse noise.

When termination of the interference (fig, 2, t tj), the output signal is higher than 7 U g ,,, then

ki

Ubu

 . In this case, block 9 of the comparison) Q not return to the initial state. The output signal of comparator 9 is supplied to key 6. As a result, key 6 connects demodulator 3 to the input of filter 4 and the amplifier returns to its initial state of operation when the output signal of demodulator 3 is fed to filter 4 for allocation. signal proportional to the input.

20 Thus, in the proposed

The device provides for the suppression of effective impulse noise.

Suppression of narrow-band dc amplifier acting

25 interference occurs as follows.

The output signal from the demodulator is fed to the converter 10 frequency - voltage, where it is analyzed by the values of the interfering signal at

1, where it is modulated by the amplitude of sig-a-s of various frequencies. If narrowband frequency f,

served on

modulator 1 from oscillator 5. The amplitude modulated signal is applied to ac amplifier 2 (Fig. 2d t, - t-d). From the output of the amplifier, a signal is applied to the demodulator 3 and to the output driver 7 s of a constant time. Under the action of interference, the output signal of Yrcp V1-1Pr miter.h 7 (Fig. 2e), even attenuated by attenuator 8, becomes larger than the signal

Off

at the output of the amplifier (Fig. 2e),

uin Bu.v As a result

and

with KTJg, and

block 9 comparison is triggered. At the output of the comparator unit 9, an output signal appears (Fig. 2g), which switches the key 6.

At the same time, the control 1 input of the demodulator 3 through 1 SPS 6 sends a control signal, which opens the keys of the demodulator 3. This causes the output signal of the amplifier 2 nepeMeiinoro current from the input of the amplifier 4 to turn off. at time t, which ensures attenuation of the output signal caused by interference. Simultaneously with the opening of the keys to the demod

the interference acts at frequencies close to or equal to the frequencies Kf, where K 1, 3, 5, ..., fK is the switching frequency, the dispersion of the interfering signal at the amplifier output has a local extremum. In this case, the output signal from the frequency converter - the voltage tunes the frequency of the generator 5 until the dispersion of the interfering signal at the output of the device accepts the smallest value in the frequency tuning range. Quantitatively, the value of the dispersion of the interfering signal can be estimated by the formula

four

1/2

K1

1 +: L ± () 2

T2 co

where T is the time constant of filter 4; 1 - switching period; 4U) - detuning, 4w o-oO

 2ff (f - f J;

K - ko1} to |) the transfer of the amplifier amplifier 2 AC. Thus, the value of the output noise signal is inversely proportional to the magnitude of the frequency detuning at which narrowband interference operates,

51515343

relative to the switching frequency.

When changing noise conditions, i.e. when the frequency of the active 5 narrowband interference changes, the frequency to voltage converter tunes the frequency of the generator 5 of the reference signals to obtain the lowest dispersion value of the interfering signal in the frequency tuning range. In this way, the operation of the device in an varying disturbance environment is adapted.

Improving the accuracy of the proposed amplifier under the conditions of low-frequency electrical noise is provided by using a change in the switching frequency and suppressing low-frequency pulsed, electrical noise.

Frequency converter 10 is the voltage shown in FIG. 3, works as follows.

A filter 1 with a cut-off frequency equal to the highest value of the switching frequency filters high-frequency noise filtering. The interfering signal is then applied to the band-pass filters 12 and 14. The first band-pass filter 12 on

and the second is full frequency 2 f.

35

From the outputs of the band-pass filters 12 and 14, the interfering signal is fed to the inputs of the amplitude detectors 13 and 15. On. The output of each amplitude detector is separated by a voltage proportional to the dispersion of the interfering signal at frequencies f, and 2f, respectively. The excess of one voltage over another triggers the comparison unit 6 and the control signal sets the frequency of the generator 5 reference signals, at which the variance 45

The interference signal si is the smallest.

The sampling control of the frequency of the reference signal generator during the duration of the impulse noise operation prevents the possibility of perestroot) 5 10

50

five

0

five

five

0

ki switching frequency f, caused by .., the action of a pulse, rather than a narrowband interference.

Claims (2)

1. A DC amplifier containing a series-connected modulator, an AC amplifier, a demodulator and a low-pass filter, as well as a reference signal generator, the output of which is connected to the control input of the modulator, so that, in order to increase accuracy by suppressing low-frequency impulse noise, a rectifier, an attenuator, a comparison unit, a key, a frequency-voltage converter are introduced, while the output of the AC amplifier is through a series-connected rectifier and attenuator The torus is connected to one input of the comparison unit, the other input of which is connected to the output of the low-pass filter, and the output to the input of the key control and the control input of the frequency converter -. the output of which is connected to the output of the AC amplifier, and the output to the control input of the reference signal generator, the output of which is connected via a switch to the control input of the demodulator. 2. The amplifier according to claim 1, characterized in that the frequency-voltage converter is provided on an input low-pass filter, the output of which is connected through a serially connected first bandpass filter and first amplitude detector to one input of a comparator unit, and through series-connected second bandwidth the filter and the second amplitude detector with another input of the comparator unit, the output of which is connected to one input of the output switch, the other input of which is the input for supplying the reference voltage, and the output is the output transducer frequency - voltage. fie, 1 (fJa.Z figs Uynp.