CN1063608A

CN1063608A - The stopping direct current technology and the circuit of no low-frequency distortion

Info

Publication number: CN1063608A
Application number: CN 92108356
Authority: CN
Inventors: 方祖祥; 余建国
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-03-19
Filing date: 1992-03-19
Publication date: 1992-08-19
Anticipated expiration: 2007-03-19
Also published as: CN1047511C

Abstract

The present invention utilizes and dynamically presets DC potential and come the higher DC potential that may exist in the offset input signal, and obtains the ac small signal that is present in the high DC potential with dynamic tracking, has solved the low-frequency distortion that resaistance-capacity coupling circuit commonly used brings.Bioelectrical signals and some are had big DC potential ac small signal be a kind of ideal stopping direct current front end circuit every straight extraction.The present invention also can obtain simultaneously isolating transmission and realize significantly output in limited out-put dynamic range corresponding to the AC signal high accuracy of no DC potential.

Description

The stopping direct current technology and the circuit of no low-frequency distortion

The invention belongs to Signal Pretreatment technology in the electronic circuit.

For the ac small signal that has higher DC potential every straight extraction, electrocardio in the biological example medical science signal of telecommunication, brain electricity, myoelectricity etc., prior art all is to adopt partiting dc capacitor to remove these DC potential more much bigger than useful signal, because biological medical signal low side frequency is often very low, therefore adopt electric capacity every directly causing low-frequency distortion inevitably.Simultaneously, when electrode potential changed, (when helical pitch was switched during for example electrocardio detected) direct current was longer recovery time, also can cause pen offscale (because DC potential changes significantly, causing exceeding dynamic range), and figure is lost, even breaks pen.

The present invention comes the high DC potential in the offseting signal and plays every straight effect with dynamically presetting DC potential, can not have stopping direct current technology and the circuit that the low-frequency distortion transmission has the ac small signal of high DC potential thereby provide a kind of.

Technical scheme of the present invention as shown in Figure 1.

Specifically describe as follows:

Clock pulses CK passes through gating circuit 5 under the control of switching signal K, signal tracking circuit 3 and DC level balancing circuitry 4 are replaced counting, the output signal of circuit 3 and circuit 4 compares with input signal Vi after by add circuit 2 additions, output signal U/the D of comparator 1 is as the reversible counting control signal of circuit 3 and circuit 4, to follow the tracks of and to approach ac small signal and the DC potential among the input signal Vi.In this technical scheme, clock pulses Ck at first counts circuit 4, and make circuit 3 zero clearings, so that the output of add circuit 2 reaches the DC potential among the Vi, change-over switch signal K then, it is fixing that this DC potential is preset, and make clock pulses CK carry out reversible counting to circuit 3, makes the output signal Vo of circuit 3 follow the tracks of Vi.At this moment, the Vo signal of circuit 3 outputs is the Vi signal that is removed flip-flop, and the digital signal D of its output is the digital quantity corresponding to Vo.

The stopping direct current technical scheme of the no low-frequency distortion that the present invention proposes can be realized by following circuit.As shown in Figure 2, this circuit is by comparator circuit 6, adder circuit 7, and D/A converting circuit 8, forward-backward counter circuit 9, D/A converting circuit 10, forward-backward counter circuit 11 and control circuit 12 are formed.The operation principle of this circuit is described below:

Clock pulses CK is under the control of switching signal K, at first forward-backward counter 11 is counted (simultaneously by control circuit 12, forward-backward counter 9 zero clearings), the output of enumerator 11 is as the digital input signals of D/A converting circuit 10, and is converted into analogue signal.Sending into comparator circuit 6 by adder circuit 7 with input signal Vi compares, the control signal that the output U/D of comparator 6 counts as the addition or the subtraction of forward-backward counter 11, thus make the output level of digital to analog converter 10 approach DC level big relatively in the input signal.By change-over switch signal K, make clock pulses CK count forward-backward counter circuit 9, and stop forward-backward counter 12 is counted, then to keep this DC potential by control circuit.The output of counter circuit 9 is as the digital quantity input of D/A converting circuit 8, the output of D/A converting circuit 8 compares with input signal Vi input comparator circuit 6 after the output addition of D/A converting circuit 10 by adder circuit 7, the output of comparator circuit 6 is simultaneously as the control signal of the addition or the subtract counter of forward-backward counter circuit 9, thereby makes the output Vo of digital to analog converter 8 approach ac small signal relatively little in the input signal rapidly.The output Vo of digital to analog converter 8 is exactly the input signal Vi that has been removed DC potential like this.The output of unison counter circuit 9 also can be used as the digital quantity output corresponding to Vo.This circuit can be used as the preceding discharge road of general biomedical electronic machine.

Because in biomedical electronic surveying, often need instrument and human body electricity are isolated, therefore, the present invention also can add the output signal that is received above-mentioned front end circuit by D/A converting circuit 13 and the complete isolated data receiver circuit of forward-backward counter circuit 14 front end circuits of forming that form and above-mentioned.

Its operation principle as shown in Figure 3, the input signal Ck ' of D/A converting circuit 13 and forward-backward counter circuit 14 and U/D can obtain by transmission ways such as optocoupler, magnetic coupling or electromagnetic coupled.As can be seen from Figure 3, the structure of this circuit is identical with the structure of D/A converting circuit among Fig. 28 and forward-backward counter circuit 9, in fact work as circuit 8 and circuit 9 and following the tracks of ac small signal simultaneously, circuit 13 is also followed the tracks of input signal simultaneously with the data receiver circuit that circuit 14 is formed, this moment, the output signal Vo from digital to analog converter 13 was the input signal Vi that is removed the direct current composition, and the output number of forward-backward counter circuit 14 is pairing digital quantity D.

Fig. 4 is the schematic diagram of a kind of embodiment of the present invention.

Comparator comp is the comparator circuit 6 of Fig. 2, operational amplifier OA3 and resistance R ₂, R ₄, R ₅The add circuit 7 of pie graph 2, operational amplifier OA1, resistance R ₁Reach the DAC1 in the resistor network pie graph 2 that is made of R-2R resistance, OA2, resistance R are amplified in computing ₁And the DAC2 in the resistor network composition diagram 2 that constitutes by R-2R resistance, Count1 and Count2 be the forward-backward counter of routine, also circuit such as available trigger is combined into required forward-backward counter circuit.By with door AND1, AND2 and phase inverter INT have formed control circuit 12 as shown in Figure 2.Vref1 is the reference voltage of DAC1, and the size of this voltage and the figure place of DAC1 have determined the dynamic range and the quantified precision of signal trace.Vref2 is the reference voltage of DAC2, and the size of this voltage and DAC2 figure place have determined the dynamic range of the DC potential that quilt is preset and preset precision.Vref3 is the reference voltage of DAC3, and the size of this voltage and the figure place of DAC3 have determined the gain of system, i.e. amplitude and the dynamic range of the output Vo of receiving circuit.

By resistance R 6, operational amplifier OA4 and formed DAC3 and Count3 as shown in Figure 3 by the resistor network that R-2R constitutes and constituted data receiver circuit as shown in Figure 3 together.

Be used for signal when transmission, can be with the circuit shown in Fig. 4 A as transmitting element, and with circuit shown in Fig. 4 B as receiving element.Output signal U/the D of transmitting element is one group of pulse train by 0,1 yard composition, and its pulse period is the period T of clock CK.But this pulse train modulated RF, magnetic field or light intensity are transmitted.And at receiving terminal, then available relevant detection element to modulation signal received, demodulation and supply Count3 and import as U/D.Ck ' the signal of receiving terminal can be separated from above-mentioned pulse train.Certainly also can be transmitted with another autonomous channel from transmitting terminal.

The present invention is applicable to and consists of high-precision preamplifier, useful ac small signal situation about being covered by the useless DC level of high-amplitude particularly, it can be eliminated or reduce significantly DC level to the impact of amplifier, and useful signal is amplified realistically and transmits. At biomedicine signals, as more useful in the preposition amplifications such as electrocardio, brain electricity, myoelectricity. For these application scenarios, it has following several outstanding advantage at least:

1, as aforementioned, it can cancellation because electrode potential (often big hundreds of times than useful signal) to the adverse effect of amplifier, and does not exist the low-frequency distortion of signal (can will hang down half power points and move to 0Hz from the 0.05Hz of routine electrocardiogram.

2, realize simultaneously two kinds of amplification outputs of simulation and numeral, put before making and realized simultaneously analog-to-digital function, be convenient to use the computer processing signals.

3, be conducive to consist of isolated amplifier. Because but the nationality data signal is carried out the information transmission between sending and receiving, therefore than the optocoupler of routine, magnetic coupling isolated amplifier transmission distortion is little, precision is high.

4, compare with the data transfer mode of pulse code modulation PCM. Under same channel transmission rate, transmissible signal frequency can improve n doubly (n is the code length of PCM).

5, compare with the bioelectric amplifier of routine, if utilize in the input as logger of the signal of receiving element DAC3 output, then because the out-put dynamic range of DAC3 is fixed, do not run off recording interval and impaired phenomenon so pen can not occur.

6, because DAC3 is controlled by the counter Count3 that has to location number, if run into excessive bioelectrical signals, then overflowing may appear in the highest order of Count3, low level then is the Continuous Approximation signal. Therefore the bioelectric amplifier that utilizes this principle to consist of such as electrocardiograph, can not take place to make the phenomenon that is recorded signal drop-out owing to baseline drift surmounts recording interval.

7, be digital signal transfers owing to what adopt between the send and receive, transmission gain can be set and be regulated very easily. The reference voltage Vref that changes DAC3 can change gain. So the bioelectric amplifier that utilizes this principle to consist of can arrange main amplifier again.

Fig. 1 is technical scheme figure of the present invention

Fig. 2 is a schematic block circuit diagram of the present invention

Fig. 3 is complete isolated data receiver circuit

Fig. 4 is for being a kind of embodiment schematic diagram of the present invention

Claims

1, a kind of usefulness dynamically arranges DC potential and offsets useless direct current composition to obtain the technical scheme that is present in small-signal in the high DC potential, it is characterized in that clock CK passes through gating circuit 5 under the control of switching signal K, can count signal tracking circuit 3 or DC potential balancing circuitry 4 selectively, circuit 3, the output of circuit 4 compares with input signal Vi after by add circuit 2 additions, output signal U/the D of comparison circuit 1 as circuit 3 and circuit 4 just/the negative sense counting controling signal, the output of circuit 3 can be followed the tracks of the small-signal of the alternation among the input signal Vi under the effect of CK, and the output of circuit 4 can approach the direct current (current potential) among the Vi.In this technical scheme, at first circuit 4 is counted, and made circuit 3 zero clearings, so that the output of add circuit 2 approaches the DC potential among the Vi by K control enable clock pulse CK.Change-over switch signal K then is fixed on the preset value DC potential and allows circuit 3 countings, under the continuous action of CK, owing to relatively constantly carry out by shooting, can make the output signal V of circuit 3.Follow the tracks of the variation of Vi.At this moment, the output Vo of circuit 3 is the useful AC signal that is eliminated useless direct current composition.The state of enumerator is the digital quantity D corresponding to Vo in the while circuit 3.

2, a kind of usefulness dynamically presets DC potential and comes every directly, to obtain the electronic circuit that is present in ac small signal in the high DC potential, it is characterized in that, it is by comparator circuit 6, adder circuit 7, D/A converting circuit 8, forward-backward counter 9, number is touched change-over circuit 10, and forward-backward counter circuit 11 and control circuit 12 are formed.

3, electronic circuit according to claim 2, it is characterized in that also can adding complete isolated data receiver circuit, transmit, accept and revert to analogue signal with data communication mode, it is made up of D/A converting circuit 13 and reversible counting circuit 14, and the output signal CK ' of the output signal U/D of comparator circuit 6 and control circuit 12 can transmit and as the input of forward-backward counter 14 by methods such as optocoupler, magnetic coupling or electromagnetic coupled.Corresponding digital quantity output D can obtain from the output of circuit 14.Analog quantity output can obtain from digital to analog converter 13.