高线性模拟光耦HCNR201_原理及其在检测

HCNR200和HCNR201模拟光电耦合器SPICE电路仿真应用笔记AN5545Jamshed Namdar Khan，安华高科技(Avago Technologies)隔离应用产品事业部光电耦合器应用工程师介绍本应用笔记的目的是展示PSpice软件如何通过使用安华高科技(Avago Technologies)提供的PSpice宏模型精确预测和仿真Avago公司HCNR200和HCNR201模拟光电耦合器的行为，聚焦集成电路仿真程序(SPICE, Sim-ulation Program with Integrated Circuit Emphasis)目前被认为是模拟电路设计工程师不可或缺的工具。

相对模拟光电耦合器数据表参数或规格，良好的宏模型应该精确预测电路性能，PSpice或SPICE仿真是任何设计工程师成功完成设计项目一个必备并且不可或缺的工具，电路仿真有助于原始设计概念的发想，从而允许工程师调整并优化原型电路取得最佳可能电路性能。

电路仿真的最大优势在于建构实体硬件或进行性能测试前可以先行验证并改善设计，极小化花费在原型测试的时间和相关费用成本。

为何需要仿真？不管电路仿真可以如何进行或带来什么，有一点它绝不可能做到的是为你提供实际的电路设计，因此我们首先列举几个吸引设计工程师进行电路仿真的原因。

进行电路仿真的主要动力是极小化预测目标电路设计性能的时间，相较于实际建立和进行原型测试等效电路的评估，使用SPICE电路进行评估所使用的时间相对上非常微小，另外，这些电路仿真也可以在各种不同温度、偏置条件以及零组件数值和误差条件下多次进行，但耗费时间仅为进行电路试验板设计并于工作台上进行评估的数分之一。

在进行光电耦合器SPICE仿真时，首先应该了解的是软件并无法仿真光电耦合器的两个基本特性，设计工程师使用光电耦合器主要有两个理由，分别是绝缘和隔离，SPICE软件并无法对这两个主要关键光电耦合器功能建立模型。

1-418HHigh-Linearity Analog Optocouplers Technical DataHCNR200HCNR201CAUTION: It is advised that normal static precautions be taken in handling and assembly of this component to prevent damage and /or degradation which may be induced by ESD.I FIPD1I PD2NCNC PD2 CATHODEPD2 ANODELED CATHODELED ANODEPD1 CATHODEPD1 ANODEFeatures• Low Nonlinearity: 0.01%• K 3 (I PD2/I PD1) Transfer Gain HCNR200: ±15%HCNR201: ±5%• Low Gain Temperature Coefficient: -65ppm/°C • Wide Bandwidth – DC to >1 MHz• Worldwide Safety Approval-UL 1577 Recognized (5 kV rms/1 min Rating)-CSA Approved -BSI Certified-VDE 0884 Approved V IORM = 1414 V peak (Option #050)• Surface Mount Option Available(Option #300)• 8-Pin DIP Package - 0.400"Spacing• Allows Flexible Circuit Design• Special Selection forHCNR201: Tighter K 1, K 3and Lower Nonlinearity AvailableApplications• Low Cost Analog Isolation • Telecom: Modem, PBX• Industrial Process Control:Transducer IsolatorIsolator for Thermocouples 4mA to 20 mA Loop Isolation • SMPS Feedback Loop, SMPS Feedforward• Monitor Motor Supply Voltage • MedicalDescriptionThe HCNR200/201 high-linearity analog optocoupler consists of a high-performance AlGaAs LED that illuminates two closelymatched photodiodes. The input photodiode can be used tomonitor, and therefore stabilize,the light output of the LED. As a result, the nonlinearity and driftcharacteristics of the LED can be virtually eliminated. The output photodiode produces a photocur-rent that is linearly related to the light output of the LED. The close matching of the photodiodes and advanced design of the package ensure the high linearity and stable gain characteristics of the optocoupler.The HCNR200/201 can be used to isolate analog signals in a wide variety of applications that require good stability, linearity,bandwidth and low cost. The HCNR200/201 is very flexible and, by appropriate design of the application circuit, is capable of operating in many different modes, including: unipolar/bipolar, ac/dc and inverting/non-inverting. The HCNR200/201 is an excellent solution for many analog isolation problems.Schematic5965-3577E1-419Ordering Information:HCNR20x0 = ±15% Transfer Gain, 0.25% Maximum Nonlinearity 1 = ±5% Transfer Gain, 0.05% Maximum NonlinearityOption yyy050 = VDE 0884 V IORM = 1414 V peak Option 300 = Gull Wing Surface Mount Lead Option 500 = Tape/Reel Package Option (1 k min.)Option data sheets available. Contact your Hewlett-Packard sales representative or authorized distributor for information.Package Outline DrawingsFigure 1.MAX."V" = OPTION 050OPTION NUMBERS 300 AND 500 NOT MARKED.1-420Gull Wing Surface Mount Option #300240TIME – MINUTEST E M P E R A T U R E – °C220200180160140120100806040200260(NOTE: USE OF NON-CHLORINE ACTIVATED FLUXES IS RECOMMENDED.)Maximum Solder Reflow Thermal ProfileRegulatory InformationThe HCNR200/201 optocoupler features a 0.400" wide, eight pin DIP package. This package was specifically designed to meet worldwide regulatory require-ments. The HCNR200/201 has been approved by the following organizations:ULRecognized under UL 1577, Component Recognition Program,FILE E55361CSAApproved under CSA Component Acceptance Notice #5, File CA 88324BSICertification according to BS415:1994;(BS EN60065:1994);BS EN60950:1992(BS7002:1992) andEN41003:1993 for Class II applicationsVDEApproved according to VDE 0884/06.92(Available Option #050only)1.78 ± 0.15 MAX.BSCDIMENSIONS IN MILLIMETERS (INCHES).LEAD COPLANARITY = 0.10 mm (0.004 INCHES).Insulation and Safety Related SpecificationsParameter Symbol Value Units ConditionsMin. External Clearance L(IO1)9.6mm Measured from input terminals to output (External Air Gap)terminals, shortest distance through air Min. External Creepage L(IO2)10.0mm Measured from input terminals to output (External Tracking Path)terminals, shortest distance path along body Min. Internal Clearance 1.0mm Through insulation distance conductor to (Internal Plastic Gap)conductor, usually the direct distancebetween the photoemitter and photodetectorinside the optocoupler cavityMin. Internal Creepage 4.0mm The shortest distance around the border (Internal Tracking Path)between two different insulating materialsmeasured between the emitter and detector Comparative Tracking Index CTI200V DIN IEC 112/VDE 0303 PART 1Isolation Group IIIa Material group (DIN VDE 0110)Option 300 – surface mount classification is Class A in accordance with CECC 00802.VDE 0884 (06.92) Insulation Characteristics (Option #050 Only)Description Symbol Characteristic Unit Installation classification per DIN VDE 0110/1.89, Table 1For rated mains voltage ≤600 V rms I-IVFor rated mains voltage ≤1000 V rms I-IIIClimatic Classification (DIN IEC 68 part 1)55/100/21Pollution Degree (DIN VDE 0110 Part 1/1.89)2Maximum Working Insulation Voltage V IORM1414V peak Input to Output Test Voltage, Method b*V PR2651V peak V PR = 1.875 x V IORM, 100% Production Test witht m = 1 sec, Partial Discharge < 5 pCInput to Output Test Voltage, Method a*V PR2121V peak V PR = 1.5 x V IORM, Type and sample test, t m = 60 sec,Partial Discharge < 5 pCHighest Allowable Overvoltage*V IOTM8000V peak (Transient Overvoltage, t ini = 10 sec)Safety-Limiting Values(Maximum values allowed in the event of a failure,also see Figure 11)Case Temperature T S150°C Current (Input Current I F, P S = 0)I S400mA Output Power P S,OUTPUT700mW Insulation Resistance at T S, V IO = 500 V R S>109Ω*Refer to the front of the Optocoupler section of the current catalog for a more detailed description of VDE 0884 and other product safety regulations.Note: Optocouplers providing safe electrical separation per VDE 0884 do so only within the safety-limiting values to which they are qualified. Protective cut-out switches must be used to ensure that the safety limits are not exceeded.1-421Absolute Maximum RatingsStorage Temperature..................................................-55°C to +125°C Operating Temperature (T A)........................................-55°C to +100°C Junction Temperature (T J)............................................................125°C Reflow Temperature Profile...See Package Outline Drawings Section Lead Solder Temperature..................................................260°C for 10s (up to seating plane)Average Input Current - I F............................................................25 mA Peak Input Current - I F.................................................................40 mA (50 ns maximum pulse width)Reverse Input Voltage - V R..............................................................2.5 V (I R = 100 µA, Pin 1-2)Input Power Dissipation.........................................60 mW @ T A = 85°C (Derate at 2.2 mW/°C for operating temperatures above 85°C) Reverse Output Photodiode Voltage................................................30 V (Pin 6-5)Reverse Input Photodiode Voltage...................................................30 V (Pin 3-4)Recommended Operating ConditionsStorage Temperature....................................................-40°C to +85°C Operating Temperature.................................................-40°C to +85°C Average Input Current - I F.......................................................1 - 20 mA Peak Input Current - I F.................................................................35 mA (50% duty cycle, 1 ms pulse width)Reverse Output Photodiode Voltage...........................................0 - 15 V (Pin 6-5)Reverse Input Photodiode Voltage..............................................0 - 15 V (Pin 3-4)1-422Electrical Specifications1-423AC Electrical SpecificationsT A = 25°C unless otherwise specified.TestParameter Symbol Device Min.Typ.Max.Units Conditions Fig.Note LED Bandwidth f -3dB9MHz I F = 10 mAApplication Circuit Bandwidth:High Speed 1.5MHz167 High Precision10kHz177 Application Circuit: IMRRHigh Speed95dB freq = 60 Hz167, 8 Package CharacteristicsT= 25°C unless otherwise specified.Notes:1. K3 is calculated from the slope of thebest fit line of I PD2 vs. I PD1 with elevenequally distributed data points from5nA to 50 µA. This is approximatelyequal to I PD2/I PD1 at I F = 10 mA.2. Special selection for tighter K1, K3 andlower Nonlinearity available.3. BEST FIT DC NONLINEARITY (NL BF) isthe maximum deviation expressed as a percentage of the full scale output of a “best fit” straight line from a graph ofI PD2 vs. I PD1 with eleven equally distrib-uted data points from 5 nA to 50µA.I PD2 error to best fit line is the deviationbelow and above the best fit line,expressed as a percentage of the fullscale output.4. ENDS FIT DC NONLINEARITY (NL EF)is the maximum deviation expressed asa percentage of full scale output of astraight line from the 5 nA to the 50 µAdata point on the graph of I PD2 vs. I PD1.5. Device considered a two-terminaldevice: Pins 1, 2, 3, and 4 shortedtogether and pins 5, 6, 7, and 8 shortedtogether.6. In accordance with UL 1577, eachoptocoupler is proof tested by applyingan insulation test voltage of ≥6000 Vrms for ≥1 second (leakage detectioncurrent limit, I I-O of 5 µA max.). Thistest is performed before the 100%production test for partial discharge(method b) shown in the VDE 0884Insulation Characteristics Table (forOption #050 only).7. Specific performance will depend oncircuit topology and components.8. IMRR is defined as the ratio of thesignal gain (with signal applied to V IN ofFigure 16) to the isolation mode gain(with V IN connected to input commonand the signal applied between theinput and output commons) at 60 Hz,expressed in dB.*The Input-Output Momentary Withstand Voltage is a dielectric voltage rating that should not be interpreted as an input-output continuous voltage rating. For the continuous voltage rating refer to the VDE 0884 Insulation Characteristics Table (if applicable), your equipment level safety specification, or HP Application Note 1074, “Optocoupler Input-Output Endurance Voltage.”1-4241-425Figure 5. NL BF vs. Temperature.Figure 2. Normalized K3 vs. Input I PD .Figure 3. K3 Drift vs. Temperature.Figure 4. I PD2 Error vs. Input I PD (See Note 4).Figure 6. NL BF Drift vs. Temperature.Figure 7. Input Photodiode CTR vs.LED Input Current.Figure 8. Typical Photodiode Leakage vs. Temperature.Figure 9. LED Input Current vs.Forward Voltage.Figure 10. LED Forward Voltage vs.Temperature.I L K – P H O T O D I O D E L E A K A G E – n AT A – TEMPERATURE – °C D E L T A K 3 – D R I F T O F K 3 T R A N S F E R G A I NT A – TEMPERATURE – °C D E L T A N L B F – D R I F T O F B E S T -F I T N L – % P T ST A – TEMPERATURE – °C N O R M A L I Z E D K 1 – I N P U T P H O T O D I O D E C T RI F – LED INPUT CURRENT – mAV F – L E D F O R W A R D V O L T A G E – VT A – TEMPERATURE – °C-25-555356595125N O R M A L I Z E D K 3 – T R A N S F E R G AI NI PD1 – INPUT PHOTODIODE CURRENT – µAI PD1 – INPUT PHOTODIODE CURRENT – µAI P D 2 E R R O R F R O M B E S T -F I T L I N E (% O F F S )N L B F – B E S T -F I T N O N -L I N E A R I T Y – %T A – TEMPERATURE – °C 1.201000.10.0001V F – FORWARD VOLTAGE – VOLTS 1.30 1.501010.010.001 1.40 1.60I F – F O R W A R D C U R R E N T – m AT A = 25°C1-426Figure 12. Basic Isolation Amplifier.FV I OUTA) BASIC TOPOLOGYFigure 11. Thermal Derating Curve Dependence of Safety Limiting Value with Case Temperature per VDE 0884.V OUTV OUTA) POSITIVE INPUT B) POSITIVE OUTPUTD) NEGATIVE OUTPUTFigure 13. Unipolar Circuit Topologies.T S – CASE TEMPERATURE – °C1-427Figure 15. Loop-Powered 4-20 mA Current Loop Circuits.Figure 14. Bipolar Circuit Topologies.OUTV OUTA) SINGLE OPTOCOUPLERB) DUAL OPTOCOUPLERVOUT+I OUTA) RECEIVERB) TRANSMITTERV -I OUT1-428Figure 18. Bipolar Isolation Amplifier.Figure 16. High-Speed Low-Cost Analog Isolator.VOUTINPUT BNCV +15 V OUTPUT BNCFigure 17. Precision Analog Isolation Amplifier.MAGV IN1-429MAGV INSIGNFigure 20. SPICE Model Listing.Figure 19. Magnitude/Sign Isolation Amplifier..SUBCKT HCNR200Theory of Operation Figure 1 illustrates how the HCNR200/201 high-linearity optocoupler is configured. The basic optocoupler consists of an LED and two photodiodes. The LED and one of the photodiodes (PD1) is on the input leadframe and the other photodiode (PD2) is on the output leadframe. The package of the optocoupler is constructed so that each photo-diode receives approximately the same amount of light from the LED.An external feedback amplifier can be used with PD1 to monitor the light output of the LED and automatically adjust the LED current to compensate for any non-linearities or changes in light output of the LED. The feedback amplifier acts to stabilize and linearize the light output of the LED. The output photodiode then converts the stable, linear light output of the LED into a current, which can then be converted back into a voltage by another amplifier.Figure 12a illustrates the basic circuit topology for implementing a simple isolation amplifier using the HCNR200/201 optocoupler. Besides the optocoupler, two external op-amps and two resistors are required. This simple circuit is actually a bit too simple to function properly in an actual circuit, but it is quite useful for explaining how the basic isolation amplifier circuit works (a few more components and a circuit change are required to make a practical circuit, like the one shown in Figure 12b).The operation of the basic circuit may not be immediately obvious just from inspecting Figure 12a,particularly the input part of thecircuit. Stated briefly, amplifierA1 adjusts the LED current (I F),and therefore the current in PD1(I PD1), to maintain its “+” inputterminal at 0 V. For example,increasing the input voltage wouldtend to increase the voltage of the“+” input terminal of A1 above 0V. A1 amplifies that increase,causing I F to increase, as well asI PD1. Because of the way that PD1is connected, I PD1 will pull the “+”terminal of the op-amp backtoward ground. A1 will continueto increase I F until its “+”terminal is back at 0 V. Assumingthat A1 is a perfect op-amp, nocurrent flows into the inputs ofA1; therefore, all of the currentflowing through R1 will flowthrough PD1. Since the “+” inputof A1 is at 0 V, the currentthrough R1, and therefore I PD1 aswell, is equal to V IN/R1.Essentially, amplifier A1 adjusts I Fso thatI PD1 = V IN/R1.Notice that I PD1 depends ONLY onthe input voltage and the value ofR1 and is independent of the lightoutput characteristics of the LED.As the light output of the LEDchanges with temperature, ampli-fier A1 adjusts I F to compensateand maintain a constant currentin PD1. Also notice that I PD1 isexactly proportional to V IN, givinga very linear relationship betweenthe input voltage and thephotodiode current.The relationship between the inputoptical power and the outputcurrent of a photodiode is verylinear. Therefore, by stabilizingand linearizing I PD1, the lightoutput of the LED is alsostabilized and linearized. Andsince light from the LED falls onboth of the photodiodes, I PD2 willbe stabilized as well.The physical construction of thepackage determines the relativeamounts of light that fall on thetwo photodiodes and, therefore,the ratio of the photodiodecurrents. This results in verystable operation over time andtemperature. The photodiodecurrent ratio can be expressed asa constant, K, whereK = I PD2/I PD1.Amplifier A2 and resistor R2 forma trans-resistance amplifier thatconverts I PD2 back into a voltage,V OUT, whereV OUT = I PD2*R2.Combining the above threeequations yields an overallexpression relating the outputvoltage to the input voltage,V OUT/V IN = K*(R2/R1).Therefore the relationshipbetween V IN and V OUT is constant,linear, and independent of thelight output characteristics of theLED. The gain of the basic isola-tion amplifier circuit can beadjusted simply by adjusting theratio of R2 to R1. The parameterK (called K3 in the electricalspecifications) can be thought ofas the gain of the optocoupler andis specified in the data sheet.Remember, the circuit inFigure12a is simplified in orderto explain the basic circuit opera-tion. A practical circuit, more likeFigure12b, will require a fewadditional components to stabilizethe input part of the circuit, tolimit the LED current, or to1-4301-431second circuit requires two optocouplers, separate gain adjustments for the positive and negative portions of the signal,and can exhibit crossover distor-tion near zero volts. The correct circuit to choose for an applica-tion would depend on therequirements of that particular application. As with the basic isolation amplifier circuit inFigure 12a, the circuits in Figure 14 are simplified and would require a few additional compo-nents to function properly. Two example circuits that operate with bipolar input signals arediscussed in the next section.As a final example of circuit design flexibility, the simplified schematics in Figure 15 illustrate how to implement 4-20 mA analog current-loop transmitter and receiver circuits using the HCNR200/201 optocoupler. An important feature of these circuits is that the loop side of the circuit is powered entirely by the loop current, eliminating the need for an isolated power supply.The input and output circuits in Figure 15a are the same as the negative input and positive output circuits shown in Figures 13c and 13b, except for the addition of R3and zener diode D1 on the input side of the circuit. D1 regulates the supply voltage for the input amplifier, while R3 forms a current divider with R1 to scale the loop current down from 20mA to an appropriate level for the input circuit (<50 µA).As in the simpler circuits, the input amplifier adjusts the LED current so that both of its input terminals are at the same voltage.The loop current is then dividedoptimize circuit performance.Example application circuits will be discussed later in the data sheet.Circuit Design FlexibilityCircuit design with the HCNR200/201 is very flexible because the LED and both photodiodes are accessible to the designer. This allows the designer to make perf-ormance trade-offs that would otherwise be difficult to make with commercially available isolation amplifiers (e.g., bandwidth vs.accuracy vs. cost). Analog isola-tion circuits can be designed for applications that have either unipolar (e.g., 0-10 V) or bipolar (e.g., ±10 V) signals, with positive or negative input oroutput voltages. Several simplified circuit topologies illustrating the design flexibility of the HCNR200/201 are discussed below.The circuit in Figure 12a is configured to be non-inverting with positive input and output voltages. By simply changing the polarity of one or both of the photodiodes, the LED, or the op-amp inputs, it is possible toimplement other circuit configu-rations as well. Figure 13illustrates how to change the basic circuit to accommodate both positive and negative input and output voltages. The input and output circuits can bematched to achieve any combina-tion of positive and negative voltages, allowing for both inverting and non-inverting circuits.All of the configurations described above are unipolar (single polar-ity); the circuits cannot accommo-date a signal that might swing both positive and negative. It ispossible, however, to use the HCNR200/201 optocoupler to implement a bipolar isolation amplifier. Two topologies that allow for bipolar operation are shown in Figure 14.The circuit in Figure 14a uses two current sources to offset the signal so that it appears to be unipolar to the optocoupler.Current source I OS1 provides enough offset to ensure that I PD1is always positive. The second current source, I OS2, provides an offset of opposite polarity toobtain a net circuit offset of zero.Current sources I OS1 and I OS2 can be implemented simply as resistors connected to suitable voltage sources.The circuit in Figure 14b uses two optocouplers to obtain bipolar operation. The first optocoupler handles the positive voltage excursions, while the second optocoupler handles the negative ones. The output photodiodes are connected in an antiparallel configuration so that they produce output signals of opposite polarity.The first circuit has the obvious advantage of requiring only one optocoupler; however, the offset performance of the circuit isdependent on the matching of I OS1and I OS2 and is also dependent on the gain of the optocoupler.Changes in the gain of the opto-coupler will directly affect the offset of the circuit.The offset performance of the second circuit, on the other hand,is much more stable; it is inde-pendent of optocoupler gain and has no matched current sources to worry about. However, thebetween R1 and R3. I PD1 is equal to the current in R1 and is given by the following equation:I PD1 = I LOOP*R3/(R1+R3).Combining the above equation with the equations used for Figure 12a yields an overall expression relating the output voltage to the loop current,V OUT/I LOOP = K*(R2*R3)/(R1+R3).Again, you can see that the relationship is constant, linear, and independent of the charac-teristics of the LED.The 4-20 mA transmitter circuit in Figure15b is a little different from the previous circuits, partic-ularly the output circuit. The output circuit does not directly generate an output voltage which is sensed by R2, it instead usesQ1 to generate an output current which flows through R3. This output current generates a voltage across R3, which is then sensed by R2. An analysis similar to the one above yields the following expression relating output current to input voltage:I LOOP/V IN = K*(R2+R3)/(R1*R3).The preceding circuits were pre-sented to illustrate the flexibility in designing analog isolation circuits using the HCNR200/201. The next section presents several complete schematics to illustrate practical applications of the HCNR200/201.Example Application CircuitsThe circuit shown in Figure 16 is a high-speed low-cost circuit designed for use in the feedback path of switch-mode power supplies. This application requiresgood bandwidth, low cost andstable gain, but does not requirevery high accuracy. This circuit isa good example of how a designercan trade off accuracy to achieveimprovements in bandwidth andcost. The circuit has a bandwidthof about 1.5 MHz with stable gaincharacteristics and requires fewexternal components.Although it may not appear so atfirst glance, the circuit in Figure16 is essentially the same as thecircuit in Figure 12a. Amplifier A1is comprised of Q1, Q2, R3 andR4, while amplifier A2 iscomprised of Q3, Q4, R5, R6 andR7. The circuit operates in thesame manner as well; the onlydifference is the performance ofamplifiers A1 and A2. The lowergains, higher input currents andhigher offset voltages affect theaccuracy of the circuit, but notthe way it operates. Because thebasic circuit operation has notchanged, the circuit still has goodgain stability. The use of discretetransistors instead of op-ampsallowed the design to trade offaccuracy to achieve goodbandwidth and gain stability atlow cost.To get into a little more detailabout the circuit, R1 is selected toachieve an LED current of about7-10 mA at the nominal inputoperating voltage according to thefollowing equation:I F = (V IN/R1)/K1,where K1 (i.e., I PD1/I F) of theoptocoupler is typically about0.5%. R2 is then selected toachieve the desired output voltageaccording to the equation,V OUT/V IN = R2/R1.The purpose of R4 and R6 is toimprove the dynamic response(i.e., stability) of the input andoutput circuits by lowering thelocal loop gains. R3 and R5 areselected to provide enoughcurrent to drive the bases of Q2and Q4. And R7 is selected so thatQ4 operates at about the samecollector current as Q2.The next circuit, shown inFigure17, is designed to achievethe highest possible accuracy at areasonable cost. The highaccuracy and wide dynamic rangeof the circuit is achieved by usinglow-cost precision op-amps withvery low input bias currents andoffset voltages and is limited bythe performance of the opto-coupler. The circuit is designed tooperate with input and outputvoltages from 1 mV to 10 V.The circuit operates in the sameway as the others. The only majordifferences are the two compensa-tion capacitors and additionalLED drive circuitry. In the high-speed circuit discussed above, theinput and output circuits arestabilized by reducing the localloop gains of the input and outputcircuits. Because reducing theloop gains would decrease theaccuracy of the circuit, twocompensation capacitors, C1 andC2, are instead used to improvecircuit stability. These capacitorsalso limit the bandwidth of thecircuit to about 10 kHz and canbe used to reduce the outputnoise of the circuit by reducing itsbandwidth even further.The additional LED drive circuitry(Q1 and R3 through R6) helps tomaintain the accuracy and band-width of the circuit over the entirerange of input voltages. Withoutthese components, the transcon-ductance of the LED driver would1-432decrease at low input voltages and LED currents. This would reduce the loop gain of the input circuit, reducing circuit accuracy and bandwidth. D1 prevents excessive reverse voltage from being applied to the LED when the LED turns off completely.No offset adjustment of the circuit is necessary; the gain can be adjusted to unity by simply adjusting the 50kohm poten-tiometer that is part of R2. Any OP-97 type of op-amp can be used in the circuit, such as theLT1097 from Linear Technology or the AD705 from Analog Devices, both of which offer pA bias currents, µV offset voltages and are low cost. The input terminals of the op-amps and the photodiodes are connected in the circuit using Kelvin connections to help ensure the accuracy of the circuit.The next two circuits illustrate how the HCNR200/201 can be used with bipolar input signals. The isolation amplifier inFigure18 is a practical implemen-tation of the circuit shown in Figure14b. It uses two opto-couplers, OC1 and OC2; OC1 handles the positive portions of the input signal and OC2 handles the negative portions.Diodes D1 and D2 help reduce crossover distortion by keeping both amplifiers active during both positive and negative portions of the input signal. For example, when the input signal positive, optocoupler OC1 is active while OC2 is turned off. However, the amplifier controlling OC2 is kept active by D2, allowing it to turn on OC2 more rapidly when the input signal goes negative, thereby reducing crossover distortion.Balance control R1 adjusts therelative gain for the positive andnegative portions of the inputsignal, gain control R7 adjusts theoverall gain of the isolationamplifier, and capacitors C1-C3provide compensation to stabilizethe amplifiers.The final circuit shown inFigure19 isolates a bipolaranalog signal using only oneoptocoupler and generates twooutput signals: an analog signalproportional to the magnitude ofthe input signal and a digitalsignal corresponding to the signof the input signal. This circuit isespecially useful for applicationswhere the output of the circuit isgoing to be applied to an analog-to-digital converter. The primaryadvantages of this circuit are verygood linearity and offset, withonly a single gain adjustment andno offset or balance adjustments.To achieve very high linearity forbipolar signals, the gain should beexactly the same for both positiveand negative input polarities. Thiscircuit achieves excellent linearityby using a single optocoupler anda single input resistor, whichguarantees identical gain for bothpositive and negative polarities ofthe input signal. This precisematching of gain for both polari-ties is much more difficult toobtain when separate componentsare used for the different inputpolarities, such as is the previouscircuit.The circuit in Figure19 is actuallyvery similar to the previouscircuit. As mentioned above, onlyone optocoupler is used. Becausea photodiode can conduct currentin only one direction, two diodes(D1 and D2) are used to steer theinput current to the appropriateterminal of input photodiode PD1to allow bipolar input currents.Normally the forward voltagedrops of the diodes would cause aserious linearity or accuracyproblem. However, an additionalamplifier is used to provide anappropriate offset voltage to theother amplifiers that exactlycancels the diode voltage drops tomaintain circuit accuracy.Diodes D3 and D4 perform twodifferent functions; the diodeskeep their respective amplifiersactive independent of the inputsignal polarity (as in the previouscircuit), and they also provide thefeedback signal to PD1 thatcancels the voltage drops ofdiodes D1 and D2.Either a comparator or an extraop-amp can be used to sense thepolarity of the input signal anddrive an inexpensive digitaloptocoupler, like a 6N139.It is also possible to convert thiscircuit into a fully bipolar circuit(with a bipolar output signal) byusing the output of the 6N139 todrive some CMOS switches toswitch the polarity of PD2depending on the polarity of theinput signal, obtaining a bipolaroutput voltage swing.HCNR200/201 SPICEModelFigure 20 is the net list of aSPICE macro-model for theHCNR200/201 high-linearityoptocoupler. The macro-modelaccurately reflects the primarycharacteristics of the HCNR200/201 and should facilitate thedesign and understanding ofcircuits using the HCNR200/201optocoupler.1-433。

收稿日期:2009-09-30基金项目:国家自然科学基金重大仪器专项项目(40727001)作者简介:杨居朋(1985-),男,山东济宁人,硕士研究生,研究方向为信号采集与智能仪器.・电路与控制・基于线性光耦HCNR201双极性信号隔离电路杨居朋1,2,王军民1,3,刘迪仁1,3(1.长江大学　油气资源与勘探技术教育部重点实验室,湖北　荆州　434023;2.长江大学电子信息学院,湖北　荆州　434023;3.长江大学地球物理与石油资源学院,湖北　荆州　434023) 摘　要:在瞬变电磁勘探中,需要在高压强电磁环境下采集电磁信号进行反褶积运算.如果模拟量与数字量之间没有电气隔离,那么高压很容易窜入低压器件并将其烧毁.设计了一个基于高精度线性光耦器件HCNR201双极性信号隔离转换电路,并介绍了高精度线性光耦器件HCNR201的主要特性及工作原理.应用于实际仪器的实验结果表明,该电路具有良好的线性度、准确度和适用性.关键词:线性光耦;HCNR201;隔离;双极性信号转换中图分类号:T N256 文献标识码:A 文章编号:1673-1255(2009)06-0051-04Design of Isolated Circuit of Bipolar Signal B asedon Linear Optocoupler HCNR 201YAN G J u 2peng 1,2,WAN G J un 2min 1,3,L IU Di 2ren 1,3(1Key L aboratory of Ex ploration Technologies f or Oiland Gas Resources ,M O E (Yangtze U niversity ),Jingz hou 434023,China ;2School of Elect ronics and Inf orm ation ,Yangtze U niversity ,Jingz hou 434023,China ;3School of Geophysics and Oil Resources ,Yangtze U niversity ,Jingz hou 434023,China ) Abstract :Data acquisition in transient electromagnetic method (TEM )is in a high voltage and strong elec 2tromagnetic field.If there is not electric isolation between analog quantity and digital amount ,the high voltage is easy to entry in the low voltage device and destroy it.A bipolarsignal isolation circuit was designed based on the features of the high 2linearity optocoupler HCN201,and the working principle and the features of the high 2linearity optocoupler HCN201were introduced.The experimental results show the circuit has the better lineari 2ty ,high acuracy and practicability in TEM system. K ey w ords :analog optocoupler ;HCNR201;isolation ;bipolarsignal conversion 在瞬变电磁勘探中,需要在高压强电磁环境下采集发射源信号进行反褶积运算.如果模拟量与数字量之间没有电气隔离,那么高压很容易窜入低压器件并将其烧毁.且各干扰信号会随着采集信号进入采集系统,这些干扰信号的叠加会降低信号的信噪比[1,2],不利于以后的信号处理.因此在高压强电磁环境下进行信号采集必须使采集系统与采集信号实现有效的电气隔离.光电隔离可以避免高压窜入低压的采集系统,且光电耦合器输入阻抗小于干扰源的内阻,因而使叠加于被测信号上的干扰信号被极大地衰减,从而保证采集信号的准确度.线性光耦HCNR201为一模拟信号光电隔离器件,可以较好地实现模拟量与数字量之间的隔离,输出跟随输入变化,线性度达0.01%,并且可以避免内部外部电路因接地不同而带来的误差.目前,基于该器件对单极性信号隔离的电路比较多[3-5].双极性信号高线性第24卷第6期2009年12月 光电技术应用EL ECTRO -OPTIC TECHNOLO GY APPL ICA TION Vol.24,No.6December.2009度隔离比单极性信号高线性度隔离复杂,这方面的研究也比较少.基于该器件工作原理特性,设计出一种基于线性光耦HCNR201双极性信号的隔离电路.1　HCNR201简介HCNR201的原理如图1所示.它由发光二极管D1、反馈光电二极管D2、输出光电二极管D3组成.当D1通过驱动电流I f时,发出红外光(伺服光通量).该光分别照在D2、D3上,反馈光电二极管D2吸收光通量的一部分,从而产生控制电流I1图1　HCNR201结构图(I1=0.005I f).该电流用来调节I f以补偿D1的非线性.输出光电二极管D3产生的输出电流I2与D1发出的伺服光通量成线性比例.令伺服电流增益K1=I1/I f,正向增益K2=I2/I f,则传输增益K3=K2/K1=I2/I1,K3的典型值为1.该器件的非线性度为0.01%,带宽大于1MHz,额定隔离电压为8000V.但不可以无限期在任意温度下隔离8000V电压.其连续运行隔离电压为1414V.2　双极性信号隔离电路设计基于HCNR201的特性设计了一种双极性信号隔离电路如图2所示.该电路由互补的两部分组成,光耦1用于正极性信号的隔离,光耦2用于负极性信号的隔离.在隔离电路中,R2调节初级运放A1输入偏置电流的大小,C1起反馈作用,同时滤除了电路中的毛刺信号,避免HCNR201的铝砷化镓发光二极管L ED受到意外冲击.R1可以控制L ED的发光强度,从而对控制通道增益起了一定作用[6].图2　双极性信号隔离电路2.1　隔离电路原理分析该电路由互补电路组成,正极性信号隔离电路与负极性信号隔离电路原理相同,只是信号输入方向和电压极性相反.因此只以正极性信号隔离电路做为分析,其隔离电路如图3所示.在图3中,I1=K1・I f,I2=K2・I f,其中K1、K2为伺服电流增益和正向增益.由电路可知V in=I1・R2=K1・I f・R2(1)V out=I2・R3=K2・I f・R3(2)则电路电压增益为G=V out/V in=(K2・I f・R3)/(K1・I f・R2)(3)在线性光耦HCNR201中K2=K1.所以G=R3/R2(4) 从式(4)可以看出,该隔离电路的电压增益只与电阻R3和R2有关,与光耦的电流传输特性无关,从而实现电压信号隔离.25 光　电　技　术　应　用 第24卷图3　正极性信号隔离电路2.2　运算放大器A 1、A 2的选择HCNR201是电流驱动,其工作电流要求1～20mA ,因此运放A 1的驱动电流必须可以达到20mA.由于隔离信号为双极性,则设计中采用双电源供电的LM358运算放大器,其输出电流可达40mA.运放A 2组成一电压跟随电路,实现输出电路的阻抗匹配.设计中运放A 2也选用双电源供电的LM358运算放大器.2.3　电阻R 1、R 2和R 3的取值由运放A 1(电路图如图3所示)虚断特性知U +=U -=V in(5)由电路图3可知I f =(V out -V d 1)/R 1(6)其中,V d 1为发光二极管D 1的正向压降.I 1=U -/R 2=V in /R 2(7)由于I 1=0.005I f [6],则式(6)、式(7)可化简为V in /R 2=0.005(V out -V d 1)/R 1(8)当R 1=0.005R 2时,V out -V d 1=V in ,即I f =V in /R 1,则R 1=V in /I f(9)设计中V in =-4～+4V ,由于MORNSUN 电源隔离器提供电源,因此V cc =+12V ,V ee =-12V ,为满足I f 取值范围1～20mA ,R 1=V in /I f =4/(20×10-3)=200Ω,R 2=R 1/0.005=40k Ω,R 3=R 2=40kΩ.2.4　隔离电路试验结果该电路首先在protuse 进行仿真实验,其输入信号为峰峰2V 的正弦波,(如图2)当只用光耦1进行信号隔离时,其输出波形如图4所示,由图4知光耦1只隔离正极性的信号,对负极性信号无隔离作用.当只用光耦2进行信号隔离时,其输出波形如图5所示,由图5知光耦2对正极性信号无隔离作用.当用光耦1和光耦2组成的互补电路(如图2)进行信号隔离时,其输出波形如图6所示,由图6知该互补电路可实现对双极性信号的隔离.图4　正极性信号输出图5　负极性信号输出图6　双极性信号输出该电路已用于井中大功率瞬变电磁场采集仪器中,所采集的井中大功率脉冲电磁场源发射电压与35第6期 杨居朋等:基于线性光耦HCNR201双极性信号隔离 图7　井中大功率脉冲电磁场源的发射电压与电流波形电流波形如图7所示,所采电压信号为分压后发射源电压,其分压比例为1000:1.由图7可知最大电压为1.5V,则发射源电压为1500V,所采集最低电压为-0.4V,则发射源电压为-400V.为方便对电流信号的采集,把电流信号经0.5Ω电阻变为电压进行采集,由图7知所采集最高电压20V,流经放电线圈的电流为40A,其电流波形与理论推导的波形相一致.经试验验证在强电压环境(1500～-400V)下,连续对发射源信号进行采集,高压未烧毁采集卡.因此该隔离电路实现了对双极性信号隔离采集,且可隔离瞬变额定电压为8000V.3　结　束　语实验结果表明,应用线性光耦HCNR201组成的双极性信号隔离电路线性度好、电路简单,有效地解决了高压强电磁对高速采集系统的影响,且由于光耦输入阻抗小,极大地衰减了叠加在采集信号上的干扰信号,提高了信号的信噪比,提高了信号处理的精确度.文中所设计的双极性隔离电路以其低成本、高稳定度、高线性度的优点可广泛应用在自动化仪表输入输出隔离、热电偶的隔离、数据通信、电压电流检测和测量、工业控制等领域.参考文献[1]　谭颖琦,范大鹏,陶溢.基于线性光耦HCNR200的DSP采集电路设计与实现[J].电测与仪表,2006(6):46-48.[2]　秦伟刚.光电耦合隔离技术与应用[J].仪器仪表学报,2006(6):2603-2604.[3]　张宝生,王念生.基于高线性度模拟光耦器件HC2NR200模拟量隔离板[J].仪表技术,2005(5):59-60.[4]　AN SAN G HOU.A Wide Bandwidth Isolation AmplifierDesign Using Current Conveyors[J].Analog IntegratedCircuits and Signal Processing,2004,40:31-38. 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基于高线性光耦HCNR201的电压电流测量电路设计模拟信号量值采集的精确度和稳定度决定了整个项目的运行可靠程度，然而，现场环境恶劣，干扰严重，为了对模拟信号的线性转换而不把现场的各种噪声干扰引入到控制系统，必须将被测模拟信号与控制系统之间进行良好的线性隔离。

一般情况下，直流隔离措施可采用专用隔离运算放大器（ISO124 系列）加配一个高精度隔离直流电源，通过电气耦合的方式来实现被测模拟信号与控制系统的线性隔离，但这种方法成本较高而且温漂较大。

本文采用线性光耦HCNR201 实现了被测模拟信号与控制系统之间的线性隔离。

线性光耦的隔离原理与普通光耦没有太大差别，只是将改变了普通光耦的单发单收模式，增加一个用于反馈的光电二极管并且增大了线性区域。

两个光电二极管都是非线性的，但其非线性特性都是一样的，所以可以通过反馈通路的非线性来抵消直通通路的非线性，从而实现了信号的线性传递。

HCNR201 的工作原理HCNR201 是Avago 公司推出的高线性光耦器件，通过外接不同的分立器件，可以实现交直流电流和电压的光电隔离转换电路，其内部结构如图1 所示。

HCNR201 由高性能的AlGaAs 型发光二极管及两个具有严格比例关系的光电二极管PD1 和PD2 构成。

当发光二极管中流过电流IF 时，其所发出的光会在光电二极管中PD1、PD2 感应出正比于LED 发光强度的光电流IPD1、IPD2，其中IF、IPD1、IPD2 满足以下关系：(1) (2) (3)式中K1、K2 分别为发光二极管PD1、PD2 的电流传输比，其典型值为0.48，范围为0.36～0.72；K3 为该光耦的传输增益，其典型值为1，范围为0.95～1.05。

图1 HCNR201 内部结构图光电二极管PD1 接入输入回路，用于检测和稳定AlGaAs 型发光二极管的发。

1. 线形光耦介绍光隔离是一种很常用的信号隔离形式。

常用光耦器件及其外围电路组成。

由于光耦电路简单，在数字隔离电路或数据传输电路中常常用到，如UART协议的20mA电流环。

对于模拟信号，光耦因为输入输出的线形较差，并且随温度变化较大，限制了其在模拟信号隔离的应用。

对于高频交流模拟信号，变压器隔离是最常见的选择，但对于支流信号却不适用。

一些厂家提供隔离放大器作为模拟信号隔离的解决方案，如ADI的AD202，能够提供从直流到几K的频率内提供0.025%的线性度，但这种隔离器件内部先进行电压-频率转换，对产生的交流信号进行变压器隔离，然后进行频率-电压转换得到隔离效果。

集成的隔离放大器内部电路复杂，体积大，成本高，不适合大规模应用。

模拟信号隔离的一个比较好的选择是使用线形光耦。

线性光耦的隔离原理与普通光耦没有差别，只是将普通光耦的单发单收模式稍加改变，增加一个用于反馈的光接受电路用于反馈。

这样，虽然两个光接受电路都是非线性的，但两个光接受电路的非线性特性都是一样的，这样，就可以通过反馈通路的非线性来抵消直通通路的非线性，从而达到实现线性隔离的目的。

市场上的线性光耦有几中可选择的芯片，如Agilent公司的HCNR200/201，TI子公司TOAS的TIL300，CLARE的LOC111等。

这里以HCNR200/201为例介绍2. 芯片介绍与原理说明HCNR200/201的内部框图如下所示其中1、2引作为隔离信号的输入，3、4引脚用于反馈，5、6引脚用于输出。

1、2引脚之间的电流记作IF，3、4引脚之间和5、6引脚之间的电流分别记作IPD1和IPD2。

输入信号经过电压-电流转化，电压的变化体现在电流IF上，IPD1和IPD2基本与IF成线性关系，线性系数分别记为K1和 K2,即K1与K2一般很小（HCNR200是0.50%），并且随温度变化较大（HCNR200的变化范围在0.25%到0.75%之间），但芯片的设计使得 K1和K2相等。

HCNR200和HCNR201模拟光电耦合器SPICE电路仿真应用笔记AN5545Jamshed Namdar Khan，安华高科技(Avago Technologies)隔离应用产品事业部光电耦合器应用工程师介绍本应用笔记的目的是展示PSpice软件如何通过使用安华高科技(Avago Technologies)提供的PSpice宏模型精确预测和仿真Avago公司HCNR200和HCNR201模拟光电耦合器的行为，聚焦集成电路仿真程序(SPICE, Sim-ulation Program with Integrated Circuit Emphasis)目前被认为是模拟电路设计工程师不可或缺的工具。

相对模拟光电耦合器数据表参数或规格，良好的宏模型应该精确预测电路性能，PSpice或SPICE仿真是任何设计工程师成功完成设计项目一个必备并且不可或缺的工具，电路仿真有助于原始设计概念的发想，从而允许工程师调整并优化原型电路取得最佳可能电路性能。

电路仿真的最大优势在于建构实体硬件或进行性能测试前可以先行验证并改善设计，极小化花费在原型测试的时间和相关费用成本。

为何需要仿真？不管电路仿真可以如何进行或带来什么，有一点它绝不可能做到的是为你提供实际的电路设计，因此我们首先列举几个吸引设计工程师进行电路仿真的原因。

进行电路仿真的主要动力是极小化预测目标电路设计性能的时间，相较于实际建立和进行原型测试等效电路的评估，使用SPICE电路进行评估所使用的时间相对上非常微小，另外，这些电路仿真也可以在各种不同温度、偏置条件以及零组件数值和误差条件下多次进行，但耗费时间仅为进行电路试验板设计并于工作台上进行评估的数分之一。

在进行光电耦合器SPICE仿真时，首先应该了解的是软件并无法仿真光电耦合器的两个基本特性，设计工程师使用光电耦合器主要有两个理由，分别是绝缘和隔离，SPICE软件并无法对这两个主要关键光电耦合器功能建立模型。

高线性模拟光耦 HCNR201 原理及其在检测电路中的应用摘要：HCNR201 是HP 公司生产的高线性度模拟光电耦合器，它具有很高的线性度和灵敏度，可在检测系统中精确地传送电压信号。

文中介绍了高线性度模拟光耦HCNR201 的内部结构和工作原理，给出了用 HCNR201 和运算放大器实现检测电压的隔离传输电路。

关键词：光电耦合器件；隔离；测量电路；HCNR2011前言在测试系统中，为了减少环境噪声对测试电路的影响，确保测量结果的准确性，往往将被测电路与测试电路在电气上进行隔离，这就需要光电耦合器。

普通光电耦合器具有非线性电流传输特性，这对于数字量和开关量的传输不成问题，但对于模拟量的传输精度则很差。

本文介绍了 HP 公司生产的一种高线性度模拟光电耦合器 HCNR201 主要结构和工作原理。

笔者曾在某随动检测系统中使用 HCNR201 来精确地传送检测板所需的电压信号。

并进行前向信道与后向信道的隔离，取得了满意的效果。

2HCNR201 的结构及工作原理HCNR201 光电耦合器是一种由三个光电元件组成的器件，主要技术指标如下：●具有±5％的传输增益误差和±0．05％的线性误差；●具有 DC～1MHz 的带宽；●绝缘电阻高达 1013Ω，输入与输出回路之间的分布电容为 0．4pF；●耐压能力为一分钟 5000V，最大绝缘工作电压为 1414V；●具有 0～15V 的输入／输出范围。

HCNR201 光电耦合器的内部结构如图 1 所示，其中 LED 为铝砷化镓发光二极管，PD1、PD2 是两个相邻匹配的光敏二极管，这种封装结构决定了每一个光敏二极管都能从 LED 得到近似的光照，因而消除了LED 的非线性和偏差特性所带来的误差。

当电流流过 LED 时，LED 发出的光被耦合到 PD1 与PD2，从而在器件输出端产生与光强成正比的输出电流。

在使用时，可将第 3、4 输出端与第 1、2 输入端一起接入控制回路，其中第 3、4 端的光敏二极管起反馈作用，它可将产生的输出电流再反馈到第 1、2 端的LED 上，以对输入信号进行反馈控制。

收稿日期:2010-02-23基金项目:河南省科技厅资助项目(022*******)作者简介:李培建(1980-),男,河南许昌人,助理工程师,主要从事测控系统开发等方面的研究.#电路与控制#线性光耦HCNR201原理及其在轴承故障检测中的应用李培建1,蔡海潮2(1.空军驻安顺地区军代表室,贵州 安顺 561000,2.河南科技大学机电工程学院,河南 洛阳 471003)摘 要:因铁路货车轴承故障检测现场工况复杂,各种电磁干扰信号极易随被测信号进入测量系统.针对这个问题,设计了用高线性度模拟光耦HCN R201和运算放大器实现的电压隔离硬件电路.该电路中,线性光耦的前端用一个运算放大器构成一个负反馈放大器,用来检测模拟电压信号;线性光耦后端的运算放大器进行电流与电压之间的转换,最终输出电压信号,实现电压信号的1:1隔离传输.实验结果表明:该方法测量电压线性度好、精度高.关键词:线性光耦;隔离;电压信号;HCNR 201中图分类号:TN 256;TN 75 文献标识码:A 文章编号:1673-1255(2010)02-0051-03Principle of Linearity Optocouplers HCNR 201and ItsApplications in Bearing Fault DetectionLI Pe-i jian 1,CAI H a-i chao 2(1.A ir Force M ilitar y Rep r esentativ e Of f ice in A nshun area ,A nshun 561000,China;2.Electromechanical Engineering College,H enan Univ er sity of Science &T echnology ,Luoy ang 471003,China )Abstract:Because railway trucks bearing fault detection field conditions are extremely complicated,every electromagnetic interference signals can easily enter the measurement system along w ith the measured signal.To address this issue,the voltage isolation hardw are circuit achieved by hig h linearity analog optocoupler HCNR201and operational amplifier w as designed.In the circuit,one operational amplifier is used as a neg ative feedback amplifier in front of the linear optocoupler,w hich is used to detect analog voltage signal;the operational amplif-i er at the end of linear optocoupler makes a conversion betw een the current and voltage,outputs finely voltage signal and achieves the 1:1isolation transm ission of voltage signal.The experimental results show that the mea -suring method can realize the good voltage linearity and high accuracy. Key words:linear optocoupler;isolation;voltage signal;HCNR201 在铁路货车轴承故障检测系统中,因现场工况复杂,在进行现场测量时,各种电磁干扰信号都会随着被测量信号进入测量系统,这些干扰信号叠加在有用的被测信号上会使测量的准确度降低[1,2].另一方面,测量系统与被测信号/共地0引入的干扰也会造成测量系统的不稳定,从而影响检测系统的正常工作.故须设法将干扰信号源与测量系统隔离,仅允许被测量信号进入测量系统.因此,找到一种有效的方法运用于现场检测系统进行模拟信号的隔离是至关重要的.常用的隔离方法有隔离放大器法和光电隔离法[3].光电耦合是以光信号为媒介来实现电信号的耦合和传递的,其抗干扰能力强[4].普通光电耦合器具有非线性电流传输特性,这对于数字量和开关量的传输不成问题,但对于模拟量的传输精度则很差.介绍了HP 公司生产的一种高线性度模拟光电耦合器HCNR201的主要结构和工作原第25卷第2期2010年4月光电技术应用EL ECT RO -OPT IC T ECHNO LOG Y AP PLI CAT IONVo l.25,No.2Apr il.2010理,并且设计了基于H CNR201的电压隔离测量电路,并通过实验对电路进行了验证[5].1 HCN R201的结构及工作原理HCNR201光电耦合器的内部结构如图1所示,其中LED 为铝砷化镓发光二极管,PD 1、PD 2是2个相邻匹配的光敏二极管,这种封装结构决定了每一个光敏二极管都能从LED 得到近似的光照,因而消除了LED 的非线性和偏差特性所带来的误差.当电流流过LED 时,LED 发出的光被耦合到PD 1与PD 2,从而在器件输出端产生与光强成正比的输出电流.在使用时,可将第3、4输出端与第1、2输入端一起接入控制回路,其中第3、4端的光敏二极管起反馈作用,它可将产生的输出电流再反馈到第1、2端的LED 上,以对输入信号进行反馈控制.HCNR201的最大非线性为0.05%,最大带宽在1MH z 以上,耐压指标为5kV/min [6].图1 HCNR 201结构原理图2 HCN R201典型应用电路在应用H CNR201构成隔离放大器时,首先应当用一个运算放大器构成一个负反馈放大器,然后利用PD 1检测LED 的光输出量,并自动调整通过LED 的电流,以补偿LED 光输出的变化及任何其他原因引起的非线性,因此该反馈放大器主要用于稳定LED 的光输出并使其线性化.另外,还需要一个运算放大器进行电流与电压之间的转换,以将输出光敏二极管PD 2输出的稳定的、线性变化的电流转换成电压信号并输出.图2是利用HCNR201光耦构成的一个简单隔离放大器的原理图.图2中的运算放大器A 1构成负反馈放大电路,运算放大器A 2为电流电压转换电路.PD 1接在放大器A 1的输入端,以完成对LED 输出光信号的检测.流经PD 1的电流为I PD 1=V i n /R 1,可见,当R 1确定后,I PD 1只正比于输入电压V i n .当其他因素引起LED 的电流I F 变化时,PD 1的负反馈作用将抑制I F 的变化,从而保证了LED 输出光强度正比于输入电压V in .HCNR201在结构设计上可保证照射在2个光敏二极管上光强度的比例为K ,因此,当LED 发光时,流经2只光敏二极管的电流之比应当为K ,即K =I PD 2/I PD 1.由于A 2的输出为V o ut =I PD 2R 2.因此可得到:V out /V i n =K R 2/R 1.可见,该隔离放大器电路的输出电压与输入电压之间的关系图2典型应用电路图3 实际应用电路52光 电 技 术 应 用 第25卷是线性变化的,而且与LED的输出光强无关.其增益可通过改变R2/R1来调整.R3为LED的限流电阻,C1、C2用于改善电路的高频特性.3信号隔离应用电路及实验结果分析图3电路实现电压信号隔离传输的功能,通过调整电位器R4和电位器R5,最终实现直流电压输入与输出1:1的关系.实验中,输入电压在直流0~ 10.66V之间变化,表1是具体的实验数据.如图4所示,其中/*0表示实测、对应的数据点,连线是最小二乘法对所测数据进行拟合所得曲线.最小二乘法算出曲线的最佳斜率为1.0005,另通过计算机算出电路的非线性度为0.01869%.表1输入电压、输出电压数据/V V in00.09460.247660.380860.590160.811161.22551.69551.92082.2548 V out00.09510.247650.380710.589910.810941.22521.69481.92062.2545 V in2.49062.77722.98993.20963.50603.61743.79354.07354.40814.7358 V out2.49072.77772.98973.20873.50703.61733.79364.07424.40794.7368 V in5.07295.38695.69006.11516.36066.69207.00627.40297.69557.8780 V out5.07415.38745.69086.11686.36206.69347.00717.40457.69757.8807 V in8.29598.61558.97939.25619.61539.915310.089310.351010.527110.6549V out8.29878.62078.98329.26169.61889.919810.094110.355610.531810.6595图4V in与V out对应曲线5结束语针对在轴承故障现场检测中所需信号受到各种电磁信号干扰的特点,给出了利用线性光耦HC-NR201进行模拟电压电气隔离的基本原理和硬件电路.经实验证明,该方法测量电压线性度好,测量精度高,有效地隔离检测现场各种干扰,可应用于轴承故障检测系统,以提高故障诊断率.参考文献[1]姜诚君,李孟源.声发射技术用于重载滚动轴承故障诊断的实验研究[J].矿山机械,2004,32(1),69-71. [2]江涛,李孟源,李云峰.货车轴承段修在线故障诊断[J].轴承,2002(2):22-24.[3]赵昕,刘洪涛.高线性模拟光耦HCNR201原理及其在检测电路中的应用[J].国外电子元器件,2003(2):24 -25.[4]童诗白,华成英.模拟电子技术基础[M].北京:高等教育出版社,2001.[5]HCN R200/201T echnical Data[Z].A gilent T echnolo-gies.[6]张维,石铭德,刘隆祉.一种高精度信号调理电路[J].自动化仪表,2001(12):56-58.欢迎刊登广告53第2期李培建等:线性光耦HCN R201原理及其在轴承故障检测中的应用。

HCNR201/200高线性度模拟光电耦合器 评估电路板使用手册硬件指南介绍HCNR200/201高线性度模拟光电耦合器包含一个用来照射两个紧密匹配光电二极管的高性能铝砷化镓(AlGaAs, Aluminium Gallium Arsenide)发光二极管(LED, Light Emitting Diode)，输入光电二极管可以作为监测从而稳定LED 的光输出，因此基本上可以消除LED 的非线性和漂移特性，输出光电二极管则可产生线性相关于LED 光输出的光电流，光电二极管间的紧密匹配和先进的封装设计可以确保光电耦合器的高线性度和稳定增益特性。

HCNR200/201可以使用于需要良好稳定性、线性度、带宽和低成本等各种广泛的模拟信号隔离应用，HCNR200/201具备高灵活度，通过适当的应用电路设计，可在多个不同的模式下工作，包括单极/双极、交流/直流以及反向/非反向等，HCNR200/201是许多模拟隔离问题的良好解决方案。

HCNR201/200评估电路板可以帮助设计工程师快速评估这些高线性度模拟光电耦合器，图1为评估电路板的结构电路，图2则是电路板的照片。

除了HCNR201/200外，这个电路板还分别在输入侧和输出侧加入两个运算放大器，请参考电路操作说明了解电路的详细工作原理。

这个评估电路板可以立即应用于电机控制设计中的电流感应，虽然评估电路板面向特定应用设计，但功能多样的高线性度模拟光电耦合器HCNR200/201适合许多应用，如电压电流感应和模拟信号耦合等。

图1：评估电路板的电路结构。

輸入側輸出側D1VCC2 (+3 to +5V)GND22评估电路板的连接和操作1. 输入侧电源：连接+15V 电源到连接器J1的脚位1，-15V 到J1的脚位4，0V 电源到J1的脚位2或3，电机驱动电路板中±15V 电源非常普遍，也可由实验室工作环境取得这些电源。

2. 输出侧电源：连接VCC2电源到评估电路板输出侧J2的脚位1，GND2到J2的脚位2，VCC2可以接受3V 到5V 的灵活电源电压范围以满足电机控制电路板上3.3V 或5V 的微控制器系统，VCC2同样也可以连接到实验室电源。