CN201298835Y - Comparator circuit for automatic threshold value adjustment - Google Patents

Abstract

The utility model relates to a comparator circuit for automatic threshold value adjustment, which comprises a general integrated comparator chip and further comprises a detector diode, two voltage dividing resistors and a filter capacitor, wherein, the input terminal of the comparator circuit is connected with the input terminal of a comparator and the anode of the detector diode, the cathode of the detector diode is connected with one end of the filter capacitor and one end of the voltage dividing resistors, the other end of the voltage dividing resistors is connected with the comparator end and one end of the voltage dividing resistors, and the other end of the voltage dividing resistors is connected with the other end of the filter capacitor and the direct-current reference voltage end. The utility model has the advantages that firstly, when the (Vi) amplitude value is very small, the (VO) can be normally turned to operating level; secondly, when the (Vi) is overlapped with low frequency interference and the amplitude fluctuates greatly, the (VY) automatically follows to adjust the threshold value to ensure that the (VO) is normally turned; and thirdly, since the amplitude of the (VY) is automatically adjusted along with the amplitude of the (Vi), and the turning moment of the (VO) is always kept in a definite moment and is little related to the (Vi) amplitude.

Description

Automatically adjust the comparator circuit of threshold value

Technical field

The utility model relates to the electronic circuit of a kind of automatic control or instrument and meter, particularly a kind of comparator circuit of automatic adjustment threshold value of sensing detection circuit.

Background technology

In automatic control or instrument and meter circuit, often run into the signal processing circuit that an interchange aanalogvoltage is shaped as the constant amplitude pulse waveform.Present this shaping circuit mostly uses integrated comparator to realize that commercially available integrated comparator chip has tens of kinds of different models.The comparator circuit that this class chip is barricaded as according to the product description of each model, all needs (or two a) comparative voltage.Wherein single comparator needs a comparative voltage V _Y, it often is bleeder circuit or the formed direct voltage of voltage stabilizing circuit.The typical circuit of this conventional comparator is shown among Fig. 1.Integrated comparator UCOMP five pins commonly used among the figure promptly add the direct current single power supply between VCC and the GND bipod; Two input: X hold to add and are compared analog signal, and the Y end can be a constant direct current comparative voltage V _YTwo voltage amplitudes of going into end are compared, as signal Vi〉V _YThe time, V _OBe high level, on the contrary V _OUpset is low level.In addition, output voltage V _OTake pin OUT.

Generally there is following shortcoming in this conventional comparison circuit:

When the amplitude that be compared voltage Vi hour, promptly the amplitude of Vi always keeps less than V _YSituation under, comparator will stop the upset.

2. when being superimposed with low-frequency interference signal on the Vi, if in a period of time, Vi always is kept above V _YSituation, or Vi always keeps below V _YSituation, should make V in during this _OIn the moment of upset, V will no longer take place _OOverturn, the result of circuit poor anti jamming capability occurs.

3. work as V _YWhen constant, and the amplitude of Vi changes, then V _OUpset also will change (claiming phase shifts again) constantly.This requires very tight index constantly for upset, can not use conventional comparison circuit.

Summary of the invention

In view of the shortcoming that prior art exists, the utility model provides a kind of comparator circuit of automatic adjustment threshold value.This comparison circuit have one can be with the changes in amplitude of input voltage signal Vi self-adjusting comparative voltage (claiming threshold value again), thereby guaranteed that in the very wide cut degree excursion of Vi circuit can both operate as normal.It is very big that this comparison circuit is applicable to that input signal amplitude rises and falls, and perhaps is superimposed with the comparing element of low-frequency disturbance voltage.

For achieving the above object, technical solution adopted in the utility model is: the comparator circuit of adjusting threshold value automatically, comprise respectively and input, positive source, the general integrated comparator chip that power cathode and circuit output end link, it is characterized in that also comprising detector diode, two divider resistances and filter capacitor, wherein, input respectively with the input of described comparator, the positive pole of detector diode links, the negative pole of detector diode connects an end of filter capacitor and an end of divider resistance respectively, the other end of divider resistance links with an end of comparator terminal and divider resistance respectively, and the other end of divider resistance connects with the other end and the DC reference voltage end of filter capacitor respectively.

The beneficial effects of the utility model are: comparative voltage V _YCan not be the Constant Direct Current signal, but the pulsating dc voltage signal, its amplitude have fundamentally changed relatively this upset and the phenomenon of not overturning occurs always within the peak value and valley of Vi, has improved the reliability of circuit.Because comparative voltage V _YBe to the peak value of Vi get after the envelope signal again the pulsating direct current signal, it keeps proportionate relationship with the peak value of Vi, the two passes through after comparison circuit, can find following three advantages, these advantages are that conventional comparison circuit is not available:

When 1.Vi amplitude is very little, V _OOperation level also normally overturns.

2.Vi be superimposed with low-frequency disturbance, and amplitude is when having than great fluctuation process, the V of the utility model circuit _YAutomatically follow the adjustment threshold value, guarantee V _ONormal upset.

3. because V _YAmplitude is adjusted automatically with the Vi amplitude, V _OUpset constantly always remain on one and determine constantly, almost irrelevant with the Vi amplitude.

Description of drawings

Fig. 1 is traditional conventional comparison circuit figure.

Fig. 2 is a circuit diagram of the present utility model and as Figure of abstract.

Fig. 3 is an application circuit of the present utility model.

Embodiment

As shown in Figure 2, adjust the comparator circuit of threshold value automatically, comprise respectively and input Vi, positive source VCC, power cathode GND and circuit output end V _OThe general integrated comparator chip that links also comprises detector diode D, divider resistance R1, R2 and filter capacitor C,

General integrated comparator chip UCOMP, in its five wiring pins, the X termination goes into to be compared voltage Vi; The Y termination is gone into and the peak value of Vi or the pulsating dc voltage V of proportionate relationship _Y(threshold value), i.e. V _YRelevant with the Vi amplitude.

The VCC termination of general integrated comparator chip UCOMP is gone into the positive pole of external power, and the negative pole of GND termination power also is the common ground of circuit, output OUT connection circuit output V _OIn two inputs of comparator, the X end directly meets input Vi; Y terminal circuit connection is: Vi links with the positive pole of detector diode D again, the negative pole of D connects an end of peak filtering capacitor C and the end of divider resistance R1 respectively, the other end of R1 links with the input Y of comparator and the end of divider resistance R2 respectively, and the other end of the other end of R2 and C all is associated in DC reference voltage end B end, B termination reference voltage V _B, its value is VB=VCC/2-0.2V.V _OBe the output voltage to GND, Vi is the input voltage for VCC/2.

The principle of circuit is as follows: input analog signal Vi is an alternating voltage, and it directly send the X end to compare.And Vi has obtained a positive peak envelope signal through detection of D half-wave and C peak filtering, and this envelope signal is sent comparator Y end again after R1 and the R2 dividing potential drop.As seen the Y end is a pulsating direct current signal of adjusting comparative voltage (threshold value) with the Vi changes in amplitude automatically.V in other words _YAlways at peak value and the V of Vi _BScope within, so UCOMP can always keep normal operating conditions.When the amplitude of Vi was 0, comparator output kept high level state constant.

Application example

Fig. 3 has provided a cover component parameters and an application circuit of the utility model circuit.

The voltage signal at X and Y two ends compares mutually in the general integrated comparator chip of MAX998 type as shown in Figure 3, and comparative result makes V _OFor+2.8V or 0V, the adding of X end is compared AC signal Vi, and the comparative voltage of Y end is the positive peak envelope voltage of Vi, and its amplitude is attenuated to 5/8 gradual voltage signal again.The power supply of MAX998 type comparator chip use+2.8V power supply.Vi is the AC signal that the mid-point voltage 1.4V for power supply imports.It is a sinusoidal signal string, and sine wave freuqency is that 50kHz is constant, and per 32 sinusoidal period are a string, and the string cycle is 1 second.The B point voltage is an impressed DC voltage among the figure, and amplitude is than the little 0.2V of VCC/2.

Experiment shows that Vi will be shaped as the pulse train that amplitude is 2.8Vpp.When the amplitude of Vi changed in 0.3～2.7Vpp scope, circuit can both operate as normal.During design circuit, the value of capacitor C is relevant with the frequency of Vi, and its value can be calculated according to the ratio of 50kHz/0.01 μ F.R1 and R2 sum are about 80k Ω, and the ratio of the two resistance is generally 3:5, in particular cases, and according to the actual adjustment of demand of circuit parameter.Press the shaping of signal except being used for sinusoidal crosstalk, this circuit can also be used for the amplitude shaping of other analog signal and compare.

Claims (1)

1. comparator circuit of automatically adjusting threshold value, comprise the integrated comparator chip, it is characterized in that, also comprise detector diode (D), divider resistance (R1, R2) and filter capacitor (C), wherein, input (Vi) respectively with (X) of described comparator end, the positive pole of detector diode (D) links, the negative pole of detector diode (D) connects an end of filter capacitor (C) respectively, one end of divider resistance (R1), the other end of divider resistance (R1) respectively with (Y) of comparator end, one end of divider resistance (R2) links, and the other end of divider resistance (R2) connects with the other end and DC reference voltage (B) end of filter capacitor (C) respectively.

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