光耦合器的技术特性与应用毕业论文外文翻译.docx

The technical characteristic and application of optical couplerThe optical coupler (OC) also calls the photoelectricity disconnector or the photoelectricity coupler.It transmits the electrical signal component taking the light as the medium.usually the illuminator (infrared light emitter diode LED) and optical receiver (photosensitive transistor) are sealed in the identical shell. When the importation added the electrical signal, the illuminator sends out the light, after accepted the light ,the light rcceiver producing the photoelectric current, flowing out from the exportation, thus realized the “electricity - light - electricity” transformation. The optical coupler，taking the light as medium and coupling importation signal to exportation, because of the slightly volume, the long life, the non-contact, the antijamming ability, between the exportation and the importation insulating, unidirectional transmission signal and so on, obtains the widespread application on the digital circuit. For several years, the new type optical coupler emerged unceasingly, have satisfied each kind of light controlingt.Its application scope expanded the measuring instruments, precision instrument, industrial used electronic instrumentation, computer and external instrumentation, telegraph, semaphore and path intelligence system, electrical power equipment and so on. The optical coupler has used in the system of electrical isolation, like computer, power source supply, communication and controller.The example, the optical coupler is using in the telecommunication equipment, the programmable controller, the cocurrent-Direct-current switch, exchange-Direct-current switch and battery charger and so on. The optical coupler is the heart of an optical communication network core，Using in the electrical isolation of input signal and the corresponding output signal.Playing the roles in the different isolation electric circuits, the needing voltages are very great different.The optical coupler has provided a superiority, that is the electricity isolates between two electric circuits,thus reduced the connection questions.The electrical isolation occurrence is because of the signal transmission through the LED illumination, and by the light responded the transistor receives. When change the size of electric current driving the light emitter diode, the light size also along with it changing proportion, thus the resistor resistance is also changed.In addition,the photoelectricity coupler also may use in controlling the alternating-current circuit power, for example heater circuit。This kind of optical coupler is the silicon-controlled rectifier outputing optical coupler, as the chart shows. Its may used in the low voltage electronic circuit controlling high voltage alternating-current circuit opening.Its principle of working is: Controlling the photosensitive bidirectional switch breakover in the exportation using infrared light in the importation, then triggering the bidirectional silicon-controlled rectifier breakover outside, achieved the goal of controlling the 220V alternating-current circuit. This driver has extremely good input-output insulating property,and may constitutes the solid state relay controlling circuit, and its output controlling power decided by bidirectional silicon-controlled rectifier.Usual photoelectricity coupler because of its non-linearity, is only restricted in the analogous circuit application of the high frequency small signal isolation transmission.The ordinary optical coupler can only transmit the the digital signal(switch), not suitable for transmitting simulation signal. In recent years,the linear optical coupler published could transmit the continuously variety simulation voltage or the simulation electric current signal, caused its application domain becoming widely greatly. It is widely used in the level transforming, the signal isolation, the interstage isolation, the switching circuit, the remote signal transmission, the pulse enlarges, solid state relay (SSR), the instrument measuring appliance, the communication facility and in the microcomputer connection.The input impedance of optical coupler is smaller than general noise source s impedance l, therefore, the disturbing voltage on importation is small .It can only provide small electric current , not easy to cause the semiconductor diode illumination; Because the photoelectricity coupler outer covering is sealed, it is not affected by exterior light。The photoelectricity couplers isolation resistor is very big (approximately 1012) and the isolation electric capacity is very small (approximately several pF) ,therefore, it can reject the electromagnetic interference of circuit coupling. When the linear photoelectricity couplers importation added the control voltage, there is a proportion voltage in the exportation using to control the further level electric circuit.The linear photoelectricity coupler is composed by the light emitter diode and the photosensitive triode,.when the light emitter diode shines, the photosensitive triode connects.The photoelectricity coupler is the electric current actuation, which needs enough big electric current to be able to cause the light emitter diode breakover. If the input signal is too small, the light emitter diode will not be able the breakover, and the output signal to distort.The optical coupler technical parameter mainly has light emitter diode forward voltage VF, forward current IF, the electric current transmission CTR, the dielectric resistance between the the input and the output ,collecting electrode - emitter electrode back breakdown voltage V(BR)CEO, collecting electrode - emitter electrode saturated voltage VCE(sat).In addition, when transmission digital signal also must consider parameters of rising time, fall time, delay time and storage time and so on.The optical coupler for transmitting the simulated signal，the illuminator isthe diode, and the optical receiver is the photosensitive triode.When there is the electric current through the light emitter diode, then forms a photosource,.This photosource shines on the surface of photosensitive triode , causing the photosensitive triode to produce the collecting electrode electric current.This electric current and the illumination are proportional. Between the importation and the exportation , optical signal transmits, thus between two parts isolates completely on the electricity, with no electrical signal feedback and disturbance, therefore, the performance is stable,and the antijamming ability is great. Between photo tube and photosensitive tube,the coupling capacity is small (about 2pf), and resistance voltage is high (about 2.5KV), therefore the CMRR is very great.The electricity isolation between input and output is decided by the dielectric resistance between two part of electric power .In addition, its input resistance is small (approximately 10), and is equal to pipe nipple to high interface resistance source noise.Therefore, the simulated signal isolation electric circuit which constitutes by the optical coupler has the fine electrical specification.In fact, the optical coupler is one kind electric current shift component by the photoelectric current controlling.Its input level is similar with the ordinary double pole transistor , thus may take it as the ordinary amplifier plotting simulation enlargement electric circuit directly, and the input-output may realize the electricity isolation. However, this kind enlarge electric circuit working stability is bad, with no practical value. Its reasons mainly have two points: First the optical coupler linearity operating region is narrow, also changing along with the temperature changing; Scond the optical coupler common emitter electric current transmission factorand collecting electrode reverse saturation current ICBO (dark current) is affected obviously by the temperature changing.Therefore, in the practical application, except elected with the linear scope width, the linearity high optical coupler realizes outside the simulated signal isolation, but also must take the effective action on the electric circuit, eliminating the influence oftemperature changing to enlarge electric circuit status as far as possible.Seen from the relation between shift characteristic and the temperature of optical coupler, making the simulation isolateion circuit stable and practical，it should eliminate the influence of dark current (ICBO) as far as possible, enhancing the linearity, achieving the static operating point IFQ automatic controlling along with the temperature changing, causing the output signal maintenance symmetry, causing the input signal dynamirange to change automatically along with the temperature changing, counterbalancing the influence of value along with the temperature changing, guaranteing the stability of electric circuit active status. 光耦合器的技术特性与应用光耦合器（optical coupler,英文缩写为OC）亦称光电隔离器或光电耦合器,简称光耦。它是以光为媒介来传输电信号的器件,通常把发光器（红外线发光二极管LED）与受光器（光敏半导体管）封装在同一管壳内。当输入端加电信号时发光器发出光线,受光器接受光线之后就产生光电流,从输出端流出,从而实现了“电光电”转换。以光为媒介把输入端信号耦合到输出端的光电耦合器,由于它具有体积小、寿命长、无触点,抗干扰能力强,输出和输入之间绝缘,单向传输信号等优点,在数字电路上获得广泛的应用。十几年来，新型光耦合器不断涌现，满足了各种光控制的要求。其应用范围已扩展到计测仪器，精密仪器，工业用电子仪器，计算机及其外部设备、通信机、信号机和道路情报系统，电力机械等领域。光耦合器已用于系统中的电气隔离，如计算机，电源供应器，通讯和控制器。举例来说，光耦合器应用于如电信设备、可编程序控制器、直流-直流转换器、交流-直流转换器和电池充电器等。光电耦合器是一个光通信网络的核心。用于电气隔离输入信号与相应的输出信号。在不同的电路起到隔离作用，其需要的电压也有很大的不同。光耦合器提供了一个优势，那就是电气隔离两电路，从而减少了接口的问题。电气隔离的发生是因为信号传递通过LED发光，并由光反应晶体管所接收。当改变驱动发光二极管的电流大小，光的强弱也随之按相应的比例改变，从而电阻器的阻值也就改变了。除此之外，光电耦合器还可以用于控制交流回路功率，例如加热电路。这种光耦合器是可控硅输出型光耦合器，如图所示。 它可应用在低电压电子电路控制高压交流回路的开启。它的工作原理是：利用输入端红外光控制输出端的光敏双向开关导通，进而触发外接双向可控硅导通，达到控制负载接入交流220V回路的目的，本驱动器有非常好的输入与输出绝缘性，可构成固态继电器的控制电路，其输出的控制功率由可控硅允许功率决定。通常的光电耦合器由于它的非线性,因此在模拟电路中的应用只限于对较高频率的小信号的隔离传送。普通光耦合器只能传输数字（开关）信号,不适合传输模拟信号。近年来问世的线性光耦合器能够传输连续变化的模拟电压或模拟电流信号,使其应用领域大为拓宽。它广泛用于电平转换、信号隔离、级间隔离、开关电路、远距离信号传输、脉冲放大、固态继电器(SSR)、仪器仪表、通信设备及微机接口中。由于光电耦合器的输入阻抗与一般干扰源的阻抗相比较小,因此分压在光电耦合器的输入端的干扰电压较小,它所能提供的电流并不大,不易使半导体二极管发光;由于光电耦合器的外壳是密封的,它不受外部光的影响;光电耦合器的隔离电阻很大（约1012）、隔离电容很小（约几个pF）所以能阻止电路性耦合产生的电磁干扰。线性方式工作的光电耦合器是在光电耦合器的输入端加控制电压,在输出端会成比例地产生一个用于进一步控制下一级的电路的电压。线性光电耦合器由发光二极管和光敏三极管组成。当发光二极管接通而发光,光敏三级管导通。光电耦合器是电流驱动型,需要足够大的电流才能使发光二极管导通,如果输入信号太小,发光二极管不会导通,其输出信号将失真。光耦合器的技术参数主要有发光二极管正向压降VF、正向电流IF、电流传输比CTR、输入级与输出级之间的绝缘电阻、集电极-发射极反向击穿电压V(BR)CEO、集电极-发射极饱和压降VCE(sat)。此外,在传输数字信号时还需考虑上升时间、下降时间、延迟时间和存储时间等参数。用于传递模拟信号的光耦合器的发光器件为二极管、光接收器为光敏三极管。当有电流通过发光二极管时，便形成一个光源，该光源照射到光敏三极管表面上，使光敏三极管产生集电极电流，该电流的大小与光照的强弱，亦即流过二极管的正向电流的大小成正比。由于光耦合器的输入端和输出端之间通过光信号来传输，因而两部分之间在电气上完全隔离，没有电信号的反馈和干扰，故性能稳定，抗干扰能力强。发光管和光敏管之间的耦合电容小（2pf左右）、耐压高(2.5KV左右)，故共模抑制比很高。输入和输出间的电隔离度取决于两部分供电电源间的绝缘电阻。此外，因其输入电阻小（约10），对高内阻源的噪声相当于被短接。因此，由光耦合器构成的模拟信号隔离电路具有优良的电气性能。事实上，光耦合器是一种由光电流控制的电流转移器件，其输出特性与普通双极型晶体管的输出特性相似，因而可以将其作为普通放大器直接构成模拟放大电路，并且输入与输出间可实现电隔离。然而，这类放大电路的工作稳定性较差，无实用价值。究其原因主要有两点：一是光耦合器的线性工作范围较窄，且随温度变化而变化；二是光耦合器共发射极电流传输系数和集电极反向饱和电流ICBO(即暗电流)受温度变化的影响明显。因此，在实际应用中，除应选用线性范围宽、线性度高的光耦合器来实现模拟信号隔离外，还必须在电路上采取有效措施，尽量消除温度变化对放大电路工作状态的影响。 从光耦合器的转移特性与温度的关系可以看出，若使光耦合器构成的模拟隔离电路稳定实用，则应尽量消除暗电流（ICBO）的影响，以提高线性度，做到静态工作点IFQ随温度的变化而自动调整，以使输出信号保持对称性，使输入信号的动态范围随温度变化而自动变化，以抵消值随温度变化的影响，保证电路工作状态的稳定性。 附录B 系统原理图