| Photoelectric couplers are widely used in the aerospace field.Their transmission,isolation and switching characteristics have great effect on the function,performance and reliability of spacecraft.At present,domestic imitation products referring to foreign optoelectronic couplers have been successfully developed,and the feature parameters are almost kept at the same level with the imitated products.But compared with foreign devices,there are still gaps in some key parameters,especially the current transmission ratio and the rate of change of the current transmission ratio over the full temperature range that users generally care about.With the temperature changing,the CTR fluctuations of domestic products are much greater than those imitated products.It can't meet the user's requirements,which resulting to the limitation of optoelectronic couplers application.Therefore,it is necessary to research how to improve the CTR temperature stability of photoelectric coupler.Photoelectric coupler is composed of light emitting diode and the photosensitive triode,the key factors affecting the current transfer ratio is analyzed by analyzing the working principle and parameters of light emitting diode and the photosensitive triode.Mainly through the analysis of the luminous efficiency of leds and the β of photosensitive triode,which relate with temperature change,to analyze the influence of the temperature on photoelectric coupler current transfer ratio.In addition,the theoretical model of the circuit transmission ratio CTR is established by using the function equation,and the corresponding temperature point of the maximum current transmission ratio at the whole temperature is calculated.At present,light emitting chips used in domestic photoelectric couplers mainly depend on outsourcing,leading to products' designing,improvement and performance improvement are limited.In the paper,the structure of the photoelectric couplers' several LED-chips were analyzed,physical structure includes the distribution function,the positive electrode surface morphology and composition,the back electrode surface morphology and composition,the electrode section morphology and composition and side morphology and composition.Through the SEM,energy spectrum analysis,spectral analysis,spectral response,we can understand the technology,structure and materials and other informations of the foreign light-emitting chips.Also we perform a series of test on the several chips used,to verify how do the leds luminous efficiency impact on the photoelectric coupler's current transfer ratio.Thus,it provides guidance for the selection of light emitting chips and the design of photoelectric couplers,also can promote the development of domestic independent photoelectric coupler controlled.We matched different infrared light-emitting chips with photosensitive triodes which have different β,and test.Using spectral response analysis of photosensitive chip matching degree,verify the β of photosensitive triode influence on photoelectric coupler current's transfer ratio.The larger the β of photosensitive triode,the greater the influence of temperature.Finally,through the process reliability validation of photoelectric coupler,adjusting the value of photoelectric coupler's current transmission ratio,we can make the CTR's min-value under full temperature range equal to that of foreign products. |
