CN1047511C

CN1047511C - No low-frequency distortion DC isolating tech. and circuit thereof

Info

Publication number: CN1047511C
Application number: CN92108356A
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: 1999-12-22
Anticipated expiration: 2007-03-19
Also published as: CN1063608A

Abstract

The present invention uses a dynamic state pre-set DC potential to counteract a higher DC potential which possibly exists in an input signal. Dynamic state tracking is used for obtaining AC small signals which exist in the higher DC potential. The present invention solves the problem of low-frequency distortion brought by a common resistance capacity coupling circuit. The present invention is an ideal DC isolating pre-set circuit for isolating extraction of biologic electrical signals and AC small signals with a larger DC potential. The present invention can simultaneously obtain high precision isolating transmission corresponding to AC signals of the non-DC potential, and can realize the output of an enlargement range in a limited output dynamic range.

Description

The partiting dc 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 object of the present invention is to provide a kind ofly can not have the partiting dc circuit that low-frequency distortion transmission has the ac small signal of high DC potential.

The present invention comes the high DC potential in the offseting signal and plays every straight effect with dynamically presetting DC potential, and its technical scheme specifically describes as follows as shown in Figure 1:

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 3 output signal Vo of circuit 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 comparison 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 l0, 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 addition or the subtraction of forward-backward counter ll, 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 l0 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.

Comparator comp is the comparator circuit 6 of Fig. 2, operational amplifier OA3 and resistance R 2, R4, the add circuit 7 of R5 pie graph 2, operational amplifier OA1, the DAC1 that resistance R 1 reaches in the resistor network pie graph 2 that is made of R-2R resistance, OA2 is amplified in computing, DAC2 in resistance R 1 and 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 makes up 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, promptly receives amplitude and the dynamic range of the output Vo of circuit.

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

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 from another independently logical first road of transmitting terminal.

Description of drawings:

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 a kind of embodiment schematic diagram of the present invention

The present invention is suitable for consisting of high-precision preamplifier, and particularly useful ac small signal is by high-amplitude Useless DC level situation about covering, it can be eliminated or reduce significantly DC level to the shadow of amplifier Ring, and useful signal is amplified realistically and transmit. At biomedicine signals, before electrocardio, brain electricity, myoelectricity etc. Put big-and-middle more useful. For these application scenarios, it has following several outstanding advantage at least:

1. as aforementioned, it can cancellation since electrode potential (often big hundreds of times than useful signal) to amplifying The adverse effect of device, and do not exist signal low-frequency distortion (can will hang down half power points from routine electrocardiogram 0.05Hz move to OHz.

2. realize simultaneously two kinds of amplification outputs of simulation and numeral, put before making and realized simultaneously analog-to-digital merit Can, 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 the signal conduct of exporting at receiving element DAC3 The input of logger is then because the out-put dynamic range of DAC3 is fixed, so pen can not occur Exceed recording interval and impaired phenomenon.

6. owing to 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, and low level then is the Continuous Approximation signal. Cause The bioelectric amplifier that this utilizes this principle to consist of such as electrocardiograph, can not take place because baseline drift is super Get over recording interval and make the phenomenon that is recorded signal drop-out.

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

Claims

1. one kind is come every directly with dynamically presetting DC potential, 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), D/A converting circuit (10), forward-backward counter circuit (11) and control circuit (12) are formed, input signal Vi directly is connected to an end of comparator circuit (6), the other end of comparator circuit (6) is connected to the output of adder circuit (7), two inputs of adder circuit (7) are connected to D/A converting circuit (8) respectively, (10) output, D/A converting circuit (8), (10) input is connected to forward-backward counter (9) respectively, (11) output, forward-backward counter (9), (10) clock input is connected to the output of control circuit (12), and the output signal U/D of comparator circuit (6) is as forward-backward counter (9) simultaneously, (11) reversible control signal.

2. electronic circuit according to claim 1, it is characterized in that also can adding complete isolated data receiver circuit, transmit with data communication mode, accept and revert to analogue signal, it is made up of D/A converting circuit (13) and reversible counting circuit (14), the output signal CK ' of the output signal U/D of comparator circuit (6) and control circuit (12) can pass through optocoupler, methods such as magnetic coupling or electromagnetic coupled transmit and as the input of forward-backward counter (14), corresponding digital quantity output D can obtain from the output of circuit (14), and analog quantity output can obtain from digital to analog converter (13).