CN203287105U

CN203287105U - Circuit capable of realizing preamplification and automatic measuring range conversion and used for light intensity detection

Info

Publication number: CN203287105U
Application number: CN201320324906XU
Authority: CN
Inventors: 朱惠宗; 许四云; 张兵; 倪新龙; 邓焯泳; 冯金垣
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2013-06-07
Filing date: 2013-06-07
Publication date: 2013-11-13
Anticipated expiration: 2023-06-07

Abstract

The utility model discloses a circuit capable of realizing preamplification and automatic measuring range conversion and used for light intensity detection. The circuit specifically includes a photoelectric detector, a dark current compensating circuit, a preamplification circuit, a measuring range converting circuit and the like. The circuit provided by the utility model employs a PIN photoelectric diode for converting light intensity signals to photo-current signals and adopts a precision chopper-stabilized operational amplifierfor converting the photo-current signals to voltage signals. The measuring range converting circuit is capable of converting automatically among four measuring ranges under the control of a single-chip microprocessor. Influence caused by dark current of the photoelectric diode can be reduced through the adjustment of the dark current compensating circuit. The circuit capable of realizing preamplification and automatic measuring range conversion and used for light intensity detection provided by the utility model has advantages that the circuit is low in noise, high in gain, high in common mode rejection ratio, low in offset, large in detectable light intensity dynamic range and the like.

Description

A kind of preposition amplification and range automatic switching circuit for the light intensity detection

Technical field

The present invention relates to the light intensity detection field.

Background technology

Owing to needing the light intensity of the surveying dynamic change scope may be very large, and should consider resolution while measuring in the light intensity detection system, take into account again measurement range, use Automatic Conversion Technology of Measuring Range just can address this problem preferably.

Existing light intensity signal amplifying circuit is only pursued high-gain mostly, but has ignored the consideration to measurement range, and exist temperature to float, the problem such as noise is bigger than normal, offset voltage is bigger than normal, can not meet the practical application request of light intensity detection system.Therefore, work out, high performance preposition amplification that detect, that can take into account resolution and measurement range for light intensity signal and range automatic switching circuit and just seem very necessary.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, proposed a kind of high performance preposition amplification and range automatic switching circuit for the light intensity detection.

a kind of preposition amplification and range automatic switching circuit for the light intensity detection, comprise for the PIN photodiode of surveying light intensity signal, also comprise preamplifier and analog switch, the positive pole of photodetector connects power supply ground, the negative pole of photodetector is connected with the reverse input end of preamplifier, the reverse input end of preamplifier is connected to power supply ground by the first resistance and the first electric capacity successively, the in-phase input end of preamplifier is connected with power supply ground, two external capacitor ends of preamplifier take back end by the electric capacity that the second electric capacity and the 3rd electric capacity are connected to preamplifier respectively, the negative supply termination negative voltage source of preamplifier, the positive supply termination positive voltage source of preamplifier, the reverse input end of preamplifier successively is connected to power supply ground by the second resistance and the 3rd resistance, as two stiff ends of variable-resistance the 5th resistance respectively with just, negative supply is connected, the moved end of the 5th resistance is connected to power supply ground by the 4th resistance and the 3rd resistance successively, the reverse input end of preamplifier is connected to the output terminal of preamplifier by the 4th electric capacity, described analog switch is double four-way imitating switch, the X passage first input end of analog switch is connected to the reverse input end of preamplifier by the 6th resistance, the X passage first input end of analog switch is connected with its Y passage first input end, X passage second input end of analog switch is connected to the reverse input end of preamplifier by the 7th resistance, X passage second input end of analog switch is connected with its Y passage second input end, X passage the 3rd input end of analog switch is connected to the reverse input end of preamplifier by the 8th resistance, X passage the 3rd input end of analog switch is connected with its Y passage the 3rd input end, the X passage four-input terminal of analog switch is connected to the reverse input end of preamplifier by the 9th resistance, the X passage four-input terminal of analog switch is connected with its Y passage four-input terminal, the ground end of analog switch is connected with power supply ground, the negative power end of analog switch is connected with negative voltage source, the positive power source terminal of analog switch is connected with positive voltage source, the X public output of analog switch is connected with the output terminal of preamplifier, the Y public output of analog switch is connected to power supply ground by the tenth resistance and the 5th electric capacity successively, the positive pole of the 5th electric capacity is connected with the tenth resistance, the negative pole of the 5th electric capacity is connected with power supply ground, draw the output voltage of whole circuit from the positive pole of the 5th electric capacity, the first electric capacity, the second electric capacity, the 3rd electric capacity and the 4th electric capacity are polarity free capacitors, the 5th electric capacity is electrochemical capacitor.

Further, preamplifier adopts chip IC L7652, and analog switch adopts chip 74HC4052.

The present invention can take into account the relation of resolution and measurement range, can realize very high performance under lower cost.Photodetector D1 is used for surveying input light intensity Pi, and light signal is converted into photo-signal, and the effect of pre-amplification circuit is exactly that the faint light electric current that effectively photodiode is produced is converted into larger voltage signal; The first capacitor C 1 is used for the high frequency noise that the filtering light-intensity variation produces, the second capacitor C 2 and the 3rd capacitor C 3 are used for the periodic dynamic compensation of chip offset voltage, and the filtering circuit that the tenth resistance R 10 and the 5th capacitor C 5 form is used for the copped wave spike noise of elimination preamplifier ICL7652; The second resistance R 2, the 3rd resistance R 3, the 4th resistance R 4 and the 5th resistance R 5 have formed dark current compensation circuit, can produce with the electric current of dark current equal and opposite in direction, opposite direction and compensate by standardsizing rheostat the 5th resistance R 5; The 6th resistance R 6, the 7th resistance R 7, the 8th resistance R 8, the 9th resistance R 9 have determined the enlargement factor of four ranges of double four-way imitating switch U2, and being certain multiple between adjacent resistor increases.After circuit powered on, range change-over circuit range automatically was set to the most high-gradely, i.e. the gain of pre-amplification circuit is maximum, and A/D converter reads an output voltage V o at set intervals to carry out outrange or owe the range judgement; Discrimination standard use A/D converter the input upper limit 95% as its upper threshold value Vmax, use the A/D converter upper limit 9% as lower threshold value Vmin, Vo Vmax is outrange, Vo＜Vmin is for owing range; If outrange, external microprocessor program control signal control range changes from high to low, until output voltage V o is between Vmax and Vmin; If input optical power Pi causes existing range improper after changing, circuit determines the increase and decrease of range automatically according to the variation tendency of Pi, until range is again suitable.The present invention has the advantages such as low noise, high-gain, high cmrr, little, the detectable light intensity dynamic range of imbalance be large.

Description of drawings

Fig. 1 is circuit theory diagrams of the present invention.

Embodiment

The chip IC L7652 that the present invention relates to is the accurate chopper stabilization type operational amplifier of American I ntersil company, except the characteristics with common operational amplifier, also have high-gain, high cmrr, imbalance is little and the advantage such as low of drifting about, be commonly used in the prime amplifier of measuring feeble signal and carry out data acquisition.1 pin of ICL7652 is external capacitor end CEA, and 2 pins are inverting input-IN, and 3 pins are in-phase input end+IN, 4 pins are negative power end-V, and 5 pins are that electric capacity takes back end CR, and 6 pins are output terminal OUTPUT, 7 pins are positive power source terminal V+, and 8 pins are external capacitor end CEB.

The chip 74HC4052 that the present invention relates to is the two-way 4 tunnels analogy demultplexer/MUX of Fairchild semiconductor company, with public selection logic.1 pin of 74HC4052 is the first input end Y1 of Y passage, 2 pins are the 3rd input end Y3 of Y passage, 3 pins are Y public output Y, 4 pins are four-input terminal Y4 of Y passage, 5 pins are second input end Y2 of Y passage, 6 pins are to forbid holding INH, 7 pins are negative power end VEE, 8 pins are held GND with being, 9 pins are address end CNTL IN B, 10 pins are address end CNTL IN A, 11 pins are X passage four-input terminal X4, 12 pins are X passage first input end X1, 13 pins are X public output X, 14 pins are X passage second input end X2, 15 pins are X passage the 3rd input end X3, 16 pins are positive power source terminal VDD.While only having 6 pin INH to be low level, the 74HC4052 chip could work.74HC4052 selects one of 4 inner passages according to the control signal of CNTL IN B, two address wires of CNTL IN A, when CNTL IN B, CNTL IN A were inputted 00,01,10,11, the switch that corresponds respectively on 1,2,3,4 passages was in closure state.

as shown in Figure 1, a kind of preposition amplification and range automatic switching circuit for the light intensity detection, comprise for the PIN photodiode D1 that surveys light intensity signal, it is characterized in that: the positive pole of photodetector D1 connects power supply ground, the negative pole of photodetector D1 is connected with reverse input end-IN of preamplifier U1, the reverse input end of preamplifier U1-IN successively is connected to power supply ground by the first resistance R 1 and the first capacitor C 1, in-phase input end+IN of preamplifier U1 is connected with power supply ground, two external capacitor end CEA of preamplifier U1, the electric capacity that CEB is connected to preamplifier U1 by the second capacitor C 2 and the 3rd capacitor C 3 respectively takes back end CR, the negative power end V-of preamplifier U1 meets negative voltage source-VCC, the positive power source terminal V+ of preamplifier U1 meets positive voltage source+VCC, the reverse input end of preamplifier U1-IN successively is connected to power supply ground by the second resistance R 2 and the 3rd resistance R 3, as two stiff ends of variable-resistance the 5th resistance R 5 respectively with positive voltage source+VCC, negative voltage source-VCC is connected, the moved end of the 5th resistance R 5 successively is connected to power supply ground by the 4th resistance R 4 and the 3rd resistance R 3, reverse input end-IN of preamplifier U1 is connected to the output terminal OUTPUT of preamplifier U1 by the 4th capacitor C 4, the second chip U2 is a double four-way imitating switch, the X passage first input end X1 of analog switch U2 is connected to reverse input end-IN of preamplifier U1 by the 6th resistance R 6, the X passage first input end X1 of analog switch U2 is connected with its Y passage first input end Y1, X passage the second input end X2 of analog switch U2 is connected to reverse input end-IN of preamplifier U1 by the 7th resistance R 7, X passage the second input end X2 of analog switch U2 is connected with its Y passage the second input end Y2, X passage the 3rd input end X3 of analog switch U2 is connected to reverse input end-IN of preamplifier U1 by the 8th resistance R 8, X passage the 3rd input end X3 of analog switch U2 is connected with its Y passage the 3rd input end Y3, the X passage four-input terminal X4 of analog switch U2 is connected to reverse input end-IN of preamplifier U1 by the 9th resistance R 9, the X passage four-input terminal X4 of analog switch U2 is connected with its Y passage four-input terminal Y4, the ground end GND of analog switch U2 is connected with power supply ground, the negative power end VEE of analog switch U2 is connected with negative voltage source-VCC, the positive power source terminal VDD of analog switch U2 is connected with positive voltage source+VCC, analog switch U2 forbids holding INH and two address end CNTL IN A, CNTL IN B is connected with three input/output end ports of external microprocessor respectively, the gating that is used for analog switch, the X public output X of analog switch U2 is connected with the output terminal OUTPUT of preamplifier U1, the Y public output Y of analog switch U2 successively is connected to power supply ground by the tenth resistance R 10 and the 5th capacitor C 5, the positive pole of the 5th capacitor C 5 is connected with the tenth resistance R 10, the negative pole of the 5th capacitor C 5 is connected with power supply ground, draw the output voltage V out of whole circuit from the positive pole of the 5th capacitor C 5, the first capacitor C 1, the second capacitor C 2, the 3rd capacitor C 3 and the 4th capacitor C 4 are polarity free capacitors, the 5th capacitor C 5 is electrochemical capacitors.

Claims

1. one kind is used for preposition amplification and the range automatic switching circuit that light intensity detects, comprise for the PIN photodiode of surveying light intensity signal, it is characterized in that: also comprise preamplifier and analog switch, the positive pole of photodetector connects power supply ground, the negative pole of photodetector is connected with the reverse input end of preamplifier, the reverse input end of preamplifier is connected to power supply ground by the first resistance and the first electric capacity successively, the in-phase input end of preamplifier is connected with power supply ground, two external capacitor ends of preamplifier take back end by the electric capacity that the second electric capacity and the 3rd electric capacity are connected to preamplifier respectively, the negative supply termination negative voltage source of preamplifier, the positive supply termination positive voltage source of preamplifier, the reverse input end of preamplifier successively is connected to power supply ground by the second resistance and the 3rd resistance, as two stiff ends of variable-resistance the 5th resistance respectively with just, negative supply is connected, the moved end of the 5th resistance is connected to power supply ground by the 4th resistance and the 3rd resistance successively, the reverse input end of preamplifier is connected to the output terminal of preamplifier by the 4th electric capacity, described analog switch is double four-way imitating switch, the X passage first input end of analog switch is connected to the reverse input end of preamplifier by the 6th resistance, the X passage first input end of analog switch is connected with its Y passage first input end, X passage second input end of analog switch is connected to the reverse input end of preamplifier by the 7th resistance, X passage second input end of analog switch is connected with its Y passage second input end, X passage the 3rd input end of analog switch is connected to the reverse input end of preamplifier by the 8th resistance, X passage the 3rd input end of analog switch is connected with its Y passage the 3rd input end, the X passage four-input terminal of analog switch is connected to the reverse input end of preamplifier by the 9th resistance, the X passage four-input terminal of analog switch is connected with its Y passage four-input terminal, the ground end of analog switch is connected with power supply ground, the negative power end of analog switch is connected with negative voltage source, the positive power source terminal of analog switch is connected with positive voltage source, the X public output of analog switch is connected with the output terminal of preamplifier, the Y public output of analog switch is connected to power supply ground by the tenth resistance and the 5th electric capacity successively, the positive pole of the 5th electric capacity is connected with the tenth resistance, the negative pole of the 5th electric capacity is connected with power supply ground, draw the output voltage of whole circuit from the positive pole of the 5th electric capacity, the first electric capacity, the second electric capacity, the 3rd electric capacity and the 4th electric capacity are polarity free capacitors, the 5th electric capacity is electrochemical capacitor.

2. preposition amplification and range automatic switching circuit for the light intensity detection according to claim 1, is characterized in that preamplifier adopts chip IC L7652.

3. preposition amplification and range automatic switching circuit for the light intensity detection according to claim 1, is characterized in that analog switch adopts chip 74HC4052.