CN102322950A - Mid-infrared detection circuit parameter design method based on bridge principle - Google Patents

Abstract

The invention provides a mid-infrared detection circuit parameter design method based on a bridge principle. The method comprises the following steps: determining an upper limit and a lower limit of detector operating temperature, a corresponding background voltage allowable value and a maximal signal voltage amplitude allowed by an amplification circuit, determining resistance of a bias resistor and bias voltage of a bridge on a bridge detection arm, and resistance of a bias resistor on a bridge balancing arm, and solving an equation set to obtain a balancing resistance, an amplification multiple and check and correction of an amplification circuit amplification multiple. According to the invention, based on parameters of dark resistance, work voltage and the like of a wide temperature range end point of each detector, optimal solutions of the balancing resistance and the circuit amplification multiple are obtained, and an output signal amplitude and a measurement dynamic range of a bridge type mid-infrared detection circuit are raised. The method has the characteristics of concise step and convenient programming, and can be used for designing balancing resistance and circuit amplification multiple parameters of the mid-infrared detection circuit in quantities.

Description

A kind of middle infrared acquisition circuit parameter design method based on electrical bridge principle

Technical field

The present invention relates to a kind of Parameters design of the middle infrared acquisition circuit based on electric bridge, especially adopt the Parameters design of the bridge type detection circuit of infrared detector measurement mid-infrared laser parameter in the guide type.

Background technology

Infrared eye such as mercury cadmium telluride, indium antimonide etc. adopt electric bridge as shown in Figure 1 to add the structure of instrument amplifier when the Laser Measurement parameter usually in the guide type.R among the figure ₁Be feeler arm upper offset resistance, R ₂Be trim arm upper offset resistance, R _DBe detector resistance value, R ₃Be trim resistance, G is the enlargement factor of instrument amplifier.

Receive the influence of mercury-cadmium tellurid detector temperature characterisitic, when operating ambient temperature changes, R _DWill be with the temperature monotone variation, and the variation tendency of different detectors differs greatly.Fig. 2 is typical detector dark resistance temperature characteristics.

Can know that by circuit theory when variation of ambient temperature, the variation of detector dark resistance will cause the drift of detection circuit output background voltage.When detector is operated under the wide temperature environment, when promptly the peripheral temperature variation range is big, the problem that must consider when the background voltage drift is circuit parameter design.Suppressing the background voltage drift, is to select suitable trim temperature spot on the one hand, is the enlargement factor that reduces instrument amplifier on the other hand.Receive the restriction of mercury-cadmium tellurid detector responsiveness; Detector output signal is fainter usually; In order to obtain enough signal amplitudes; Need to improve the enlargement factor of preposition instrument amplifier, so often solve inhibition background voltage temperature and float and improve the contradiction between the signal amplitude through screening to the appropriate design of circuit parameter with to detector performance parameters.

The method for designing that is used for the batch detector amplifying circuit parameter under the wide temperature environment at present comprises following steps:

[1], gage beam and trim arm upper offset resistance R are set according to system requirements ₁, R ₂Resistance;

[2] be chosen in some steady temperature points (often getting 25 ℃ or 0 ℃) and carry out the circuit trim: make that background voltage is 0V, calculate the trim resistance R ₃=R ₂R _DR ₁

[3] according to the signal voltage amplitude and the explorer response rate that design, counting circuit enlargement factor G, computing formula is G=V _Sig/ (P _MaxR), V wherein _SigBe the maximum signal amplitudes of design, P _MaxBe the peak power that incides on the detector photosurface, R is the explorer response rate;

[4] at last according to R ₃Background voltage when working in the environment temperature upper and lower bound with G calculating detection circuit is judged whether the output of background voltage exceeds designed range, as is gone beyond the scope, and thinks that then this detector is undesirable, needs to change detector.

This method needs rule of thumb to confirm in advance the temperature spot of trim; But for most of detection circuits; This trim temperature spot is not best trim temperature spot, that is to say when detector is operated in two end points of wide warm area, and the background signal of detector is not the bound of the detector background level that is operated in measuring system just and allowed; Do not make and export the maximal value that signal reaches permission, dwindled the dynamic range of measuring system.

Summary of the invention

The object of the invention provides a kind of Parameters design that is used for bridge type infrared acquisition circuit under the wide temperature; Can be under the situation that does not change circuit structure; Make the background signal of detector be operated in the bound of the detector background level that measuring system allows; Improve the amplitude output signal of detection circuit, guarantee that measuring system has the dynamic range of broad.

Technical solution of the present invention is:

A kind of middle infrared acquisition circuit parameter design method based on electrical bridge principle may further comprise the steps:

[1], confirms the bound of detector working temperature, corresponding background voltage permissible value V according to the temperature environment and the technical requirement of measuring system practical application _{Bk_max}And V _{Bk_min}Peak signal voltage amplitude V with the amplifying circuit permission _{Sig_max}

[2] confirm electric bridge feeler arm upper offset resistance R ₁Resistance, the bias voltage V of electric bridge _Bias, electric bridge trim arm upper offset resistance R ₂Resistance;

[3] group of solving an equation obtains the trim resistance R ₃Enlargement factor G with amplifying circuit:

$\left\{\begin{array}{c}G=\frac{(V_{\mathrm{bk}\_\max }-V_{\mathrm{bk}\_\min })(R_1+R_{D\_\max })(R_1+R_{D\_\min })}{V_{\mathrm{bias}}{R}_1(R_{D\_\min }-R_{D\_\max })}\\ R_3=\frac{R_2}{R_1}\frac{V_{\mathrm{bk}\_\min }{R}_{D\_\max }(R_1+R_{D\_\min })-V_{\mathrm{bk}\_\max }{R}_{D\_\min }(R_1+R_{D\_\max })}{V_{\mathrm{bk}\_\min }(R_1+R_{D\_\min })-V_{\mathrm{bk}\_\max }(R_1+R_{D\_\max })}\end{array}\right.;$

Wherein:

R ₁Be feeler arm upper offset resistance,

V _Bias=R ₁I _DBias voltage for electric bridge;

R ₂=V _Bias/ I ₁Be the biasing resistor on the electric bridge trim arm;

R _{D_max}Be the detector dark resistance value of prescribing a time limit on the working temperature;

R _{D_min}Be the detector dark resistance value of prescribing a time limit under the working temperature;

I ₁Be working current on the trim arm.

Above-mentioned steps also comprises checking and revising of amplifying circuit enlargement factor G; The step of checking and revise of described amplifying circuit enlargement factor G is:

According to formula:

V _sig＝GP _maxSDR _{T_max}

Calculating detector works in the signal voltage V that detection circuit is exported when maximum power density laser incides on the detector photosurface on the environment temperature in limited time _Sig

If | V _Sig|＞| V _{Sig_max}|, then should the refresh circuit enlargement factor be:

$G=\frac{V_{\mathrm{sig}\_\max }}{P_{\max }{S}_D{R}_{T\_\max }}$

If | V _Sig|≤| V _{Sig_max}|, then enlargement factor G value is constant,

Wherein:

P _MaxBe the maximum laser power density that incides on the detector photosurface,

S _DBe detector photosurface area,

R _{T_max}Be that detector works in the laser responsiveness of prescribing a time limit on the environment temperature.

Above-mentioned middle infrared eye is an infrared eye in mercury cadmium telluride, indium antimonide, vulcanized lead or the tin lead.

The beneficial effect that the present invention has:

1, the present invention is according to the dark resistance value of every detector at the wide temperature range end points, and parameters such as WV obtain the optimum solution of trim resistance and circuit enlargement factor, have improved the amplitude output signal of infrared acquisition circuit in the bridge type, have improved the measurement dynamic range;

2, to have step succinct in the present invention, and the characteristics of convenience of calculation can be used for Batch Design infrared acquisition circuit trim resistance and circuit enlargement factor parameter.

Description of drawings

Fig. 1 is the middle infrared acquisition circuit diagram that the present invention is based on electrical bridge principle;

Fig. 2 is that typical mercury-cadmium tellurid detector dark resistance is with temperature variation curve.

Embodiment

As shown in Figure 1, detector R _DThe output signal can be expressed as

$V_{\mathrm{out}}=G(V_{\mathrm{bias}}\frac{R_3}{R_2+R_3}-V_{\mathrm{bias}}\frac{R_D}{R_1+R_D})$

R wherein ₁Be feeler arm upper offset resistance, R ₂Be trim arm upper offset resistance, R _DBe detector resistance value, R ₃Be trim resistance, G is the enlargement factor of instrument amplifier.Receive the influence of middle infrared eye temperature characterisitics such as mercury cadmium telluride, when operating ambient temperature changes, R _DWill be with the temperature monotone variation, and the variation tendency of different detectors differs greatly.Then when variation of ambient temperature, the variation of detector dark resistance will cause the drift of detection circuit output background voltage.

For overcoming in the existing batch detector application, select the problem of the circuit parameter design method existence of constant working temperature point trim for use, concrete steps of the present invention are:

One, confirm the conventional parameter and the designing requirement of circuit:

1) the environment temperature bound of confirming detection circuit work and corresponding background voltage V _{Bk_max}And V _{Bk_min}And the peak signal voltage amplitude V of design _{Sig_max}, these are confirmed according to the requirement of measuring system itself;

2) confirm the bias voltage V of electric bridge _Bias

Bias voltage depends on detector working current I _DAnd the resistance on the gage beam.In order to make the photoconductive detectors working current be approximately constant current, generally selecting R ₁Shi Yaoqiu R ₁R greater than 10 times _{D_max}, the bias voltage of electric bridge then, estimation equation is V _Bias=R ₁I _D, I wherein _DBe the detector operation electric current, the recommended current of every kind of detector is provided by producer, is 4mA such as the recommended current of mercury-cadmium tellurid detector.

3) R on the trim arm ₂

Working current I on the trim arm is set ₁, the resistance of estimation trim arm upper offset resistance, estimation equation is R ₂=V _Bias/ I ₁The trim arm is by the trim resistance R ₃With biasing resistor R ₂Form, the current requirements of trim arm is much larger than the bias current of instrument amplifier.The bias current of instrument amplifier is in the 10nA rank, so the bias current of trim arm can be arranged on μ A magnitude.As far as multichannel measuring system, lower bias current is set on the trim arm can effectively reduces system power dissipation.Confirm that the electric current of trim arm can estimate the resistance R of trim arm upper offset resistance afterwards ₂

Two, calculate the trim resistance R ₃With enlargement factor G:

Dark resistance value and corresponding background voltage according to detector working temperature upper and lower bound are set up following system of equations:

$\left\{\begin{array}{c}{V}_{\mathrm{bk}\_\max }=V_{\mathrm{bias}}G(\frac{R_3}{R_2+R_3}-\frac{R_{D\_\max }}{R_1+R_{D\_\max }})\\ V_{\mathrm{bk}\_\min }=V_{\mathrm{bias}}G(\frac{R_3}{R_2+R_3}-\frac{R_{D\_\min }}{R_1+R_{D\_\min }})\end{array}\right.$

V wherein _{Bk_max}And V _{Bk_min}Background voltage when representing the working temperature upper and lower bound respectively, R _{D_max}And R _{D_min}Detector dark resistance value when representing the working temperature upper and lower bound respectively, G is the enlargement factor of instrument amplifier, R ₁And R ₂Represent the biasing resistor on feeler arm and the trim arm respectively, R ₃Be the trim resistance.

According to top system of equations, can be following in the hope of the analytical expression of trim resistance and enlargement factor:

$\left\{\begin{array}{c}G=\frac{(V_{\mathrm{bk}\_\max }-V_{\mathrm{bk}\_\min })(R_1+R_{D\_\max })(R_1+R_{D\_\min })}{V_{\mathrm{bias}}{R}_1(R_{D\_\min }-R_{D\_\max })}\\ R_3=\frac{R_2}{R_1}\frac{V_{\mathrm{bk}\_\min }{R}_{D\_\max }(R_1+R_{D\_\min })-V_{\mathrm{bk}\_\max }{R}_{D\_\min }(R_1+R_{D\_\max })}{V_{\mathrm{bk}\_\min }(R_1+R_{D\_\min })-V_{\mathrm{bk}\_\max }(R_1+R_{D\_\max })}\end{array}\right.$

Generally, above-mentioned steps can satisfy the detector operation requirement, and in order to ensure perfectly safe, this method also comprises checking and revising of circuit enlargement factor G, and its step is following:

Work in the signal voltage that detection circuit is exported when maximum power density laser incides on the detector photosurface on the environment temperature in limited time according to explorer response rate calculating detector, computing formula is:

V _sig＝GP _maxS _DR _{T_max}

P wherein _MaxBe the maximum laser power density that incides on the detector photosurface, S _DBe detector photosurface area, R _{T_max}Be that detector works in the laser responsiveness of prescribing a time limit on the environment temperature.

If | V _Sig|＞| V _{Sig_max}|, wherein, V _{Sig_max}Be the maximum signal amplitudes of design, then should the refresh circuit enlargement factor, its computing formula is:

$G=\frac{V_{\mathrm{sig}\_\max }}{P_{\max }{S}_D{R}_{T\_\max }}.$

Statistical study according to systematic parameter design and experimental data generally can't occur | V _Sig|＞| V _{Sig_max}|.

Through above calculating, drawn under the wide temperature condition, the best trim resistance of electric bridge amplifying circuit and the enlargement factor of amplifying electric power.

This method is not limited to circuit connecting mode shown in Figure 1, and the IN+ that can connect instrument amplifier such as feeler arm holds, and the trim arm connects the IN-end of instrument amplifier.Under this connected mode, this method stands good.The detector that the present invention is suitable for is equally applicable to other photoconductive detectors such as vulcanized lead, tin lead etc. except mercury cadmium telluride, indium antimonide.More than change, all in protection scope of the present invention.

Claims (3)

1. middle infrared acquisition circuit parameter design method based on electrical bridge principle is characterized in that: may further comprise the steps:

[1], confirms the bound of detector working temperature, corresponding background voltage permissible value V according to the temperature environment and the technical requirement of measuring system practical application _{Bk_max}And V _{Bk_min}Peak signal voltage amplitude V with the amplifying circuit permission _{Sig_max}

[2] confirm electric bridge feeler arm upper offset resistance R ₁Resistance, the bias voltage V of electric bridge _Bias, electric bridge trim arm upper offset resistance R ₂Resistance;

[3] group of solving an equation obtains the trim resistance R ₃Enlargement factor G with amplifying circuit:

$\left\{\begin{array}{c}G=\frac{(V_{\mathrm{bk}\_\max }-V_{\mathrm{bk}\_\min })(R_1+R_{D\_\max })(R_1+R_{D\_\min })}{V_{\mathrm{bias}}{R}_1(R_{D\_\min }-R_{D\_\max })}\\ R_3=\frac{R_2}{R_1}\frac{V_{\mathrm{bk}\_\min }{R}_{D\_\max }(R_1+R_{D\_\min })-V_{\mathrm{bk}\_\max }{R}_{D\_\min }(R_1+R_{D\_\max })}{V_{\mathrm{bk}\_\min }(R_1+R_{D\_\min })-V_{\mathrm{bk}\_\max }(R_1+R_{D\_\max })}\end{array}\right.;$

Wherein:

R ₁Be feeler arm upper offset resistance,

V _Bias=R ₁I _DBias voltage for electric bridge;

R ₂=V _Bias/ I ₁Be the biasing resistor on the electric bridge trim arm;

R _{D_max}Be the detector dark resistance value of prescribing a time limit on the working temperature;

R _{D_min}Be the detector dark resistance value of prescribing a time limit under the working temperature;

I ₁Be working current on the trim arm.

2. the middle infrared acquisition circuit parameter design method based on electrical bridge principle according to claim 1 is characterized in that: also comprise checking and revising of amplifying circuit enlargement factor G; The step of checking and revise of described amplifying circuit enlargement factor G is:

According to formula:

V _sig＝GP _maxS _DR _{T_max}

Calculating detector works in the signal voltage V that detection circuit is exported when maximum power density laser incides on the detector photosurface on the environment temperature in limited time _Sig

If | V _Sig|＞| V _{Sig_max}|, then should the refresh circuit enlargement factor be:

$G=\frac{V_{\mathrm{sig}\_\max }}{P_{\max }{S}_D{R}_{T\_\max }}$

If | V _Sig|≤| V _{Sig_max}|, then enlargement factor G value is constant,

Wherein:

P _MaxBe the maximum laser power density that incides on the detector photosurface,

S _DBe detector photosurface area,

R _{T_max}Be that detector works in the laser responsiveness of prescribing a time limit on the environment temperature.

3. the middle infrared acquisition circuit parameter design method based on electrical bridge principle according to claim 1 and 2 is characterized in that: infrared eye is an infrared eye in mercury cadmium telluride, indium antimonide, vulcanized lead or the tin lead in described.

Images