The Reliability Design Of Output Type Optocoupler Based On The Photoelectric Transistor

High-reliability military optocouplers are widely used with the development of electronic components and weaponry.How to guarantee the reliability of products in basically design and avoid the early malfunction have been attracted considerable attention.The structure of the optocouple rand function of each part are systematically introduced in this paper.In general,infrared emitting diode is used for the input terminal,and Light-emitting diodes(LED)for the output terminal.The tube encapsulate the input and output terminal together to an optocoupler,and photovoltaic conversion of the two parts transport through a correlation type or an plane reflection type.Based on the basic principle of the LED,we investigated the relation between luminous power and positive output current.And the relationship of current transfer ratio(CTR),the collector current(IC),the base current(IB)and the ? have been derived according to the principle of photoelectric triode.The creepage path and the main factors of influencing the isolation voltage(VISO)are investigated on the basis of the process structure.It has been found that the VISO is gradually increased with heighten of the distance from the top of outer lead and inside cavity of ceramic package.With the perfection of material and process technology,the minimum VISO has been improved to 1.5kV and the maximum value to 2.1kV.The average VISO of 1.75 kV could meet the requirements of the project which indicating the isolation voltage is higher than 1000 V.And the improvement of VISO effectively enhance the reliability of the products.The connection between the related time parameter of optocouplers with CTR and the input current are verified according to the relationship of time parameter of double based transistor.Under the same condition,with an increase of input current,the delay time,the rise time and the turn-on time decrease.Besides,with the increasing of CTR,the rise time and the fall time and storage time are increased.And the turn-on time and the turn-off time are increased at the same time,which means that the speed of turn-on and turn-off are slow down.In this artical,the MATLAB modeling and simulation of the photoelectric coupler were made,and at the same time the different luminous chips and photo transistor chips which used in the photoelectric coupler were tested..The results of the tests provide the basis of the relations between IB and IC,the output current and IB,and the CTR and current amplification.The practical experimental results show that the CTR of the photo electric coupler is gradually increased with the increasment of the luminescence power of LED chips and the increasing of current amplification.According to the analysis of theoretical and simulation,and the matching and screening of the luminous chips and the receiver chips,the CTR has improved from 120.59% to 256.36%.The relationship between the time parameters and the input current and the CTR are analyzed through the MATLAB modeling.And the actual test results are in an agreement with the simulation results.Under the condition of ensuring the minimum CTR of 200%,there is also a wide margin of the the time parameters between actual test result and criterion of protocol,which ensures the reliability of the product in the time parameter.In this paper,the radiation-hardened situations of luminous chips of different structures and materials and the existing phototriode products have been studied by a great deal of experiments.We come to the conclusion that the seriously decrease of the parameters of optocouplers comes from the change of light current of phototriode.Therefore the perfection to the optocoupler mainly aimed at radiation-hardened reinforcement to the chips of phototriode.In this paper,the process control of the radiation-hardened LED and photoelectric triode are briefly stated.And the matching design of the luminous chips and photoelectric triode chips is conducted simultaneously.It's verified by experiments that the products' ability of tatal dose radiation hardness comes within the limit of 300Gy(Si)to 1000Gy(Si)which can meet the design requirements.The conditions of key processes which influencing the reliability of the products are systematically investigated by a series of process experiments.According to the reliability design and forming of each process,the technology reliability of the products are guaranteed,which avoids quality problems basically from the failure of technological parameters and assures the parameters consistency meet the requirements.