【正文】 in dog39。 Analyses its scope of application, provide and use the circuit concretely。 ③ In measure and control cycle among the long system, onechip puter spend wait for the peripheral hardware a large amount of time, will be interfered too when carry out and wait for the order. To these situations, we have tried the method restored to the throne voluntarily in practice, alternate pulse of adopting etc or restore to the throne waking according to external terms to the onechip puter up. After being restored to the throne each time, the onechip puter carries out the corresponding procedure, enters dormancy in time after finishing carrying out the task, wait to be restored to the throne neatly. Have solved abovementioned problems well with this method , and has got better result in the agricultural voltage transformer prehensive protector experiment. Now take 51 serial onechip puters as an example and probe into the concrete principle and implementation method, restored to the throne the signal as the high level. principle and implementation method Restored to the throne the law regularly unconditionally Use timer, specialpurpose clock chip or other pulse generator, produce signal of restoring to the throne regularly according to interval that set for. This kind of method is especially suitable for the measuring instrument. In not running actually, sample the analog quantity of introduction with A/D converter often, then store showing. This course is very fast, but steady for reading, the data per second are only upgraded 1 2 times, a large amount of time of CPU is used for waiting. Let CPU carry out and enter dormancy directly after the task , restore to the throne and wake by exter nal world up It carry out the next operation, this is to restore to the throne the law regularly In this way can make antiinterference ability strengthen greatly , have 2 points mainly: ① . At the dormancy, procedure stop run, can appear PC indicator disorderly procedure that causes run and fly. Work time in dormancy proportion 1:9, that is to say 1 s have time of s used for measuring, sending off showing, there is time dormancy of , the probability that the procedure is interfered is 1/10 while running at full speed, whole antiinterference ability raise by 10 times. ② Because every 1s is restored to the throne once unconditionally, once present the system halted during a job, can certainly resume when restored to the throne next time. As to only instrument that show, some reading mistake that 1s appear accidentally there is no memory to the next measurement, be could bear , belong to “pass” mistake. This kind is restored to the throne the advantage of dog39。s trigger to have a facelift。t still enable exporting the change to the valid level within this cycle。s best to take method 1. Restore to the throne cycle probability made mistakes to calculate very little, according to 2 for the 2nd time in succession. 4 output end son that narrate connect treatment method of electric capacity in parallel, can reach kind antiinterference result very. realizes crossing over and is restored to the throne alternate time sequence regularly to control Work in way of restoring to the throne now, start anew and carry out the same procedure repeatedly each time. Can be divided into 2 kinds of situations: ① As to simple to show instrument, carry on measurement ， send off showing after being restored to the throne each time, have causality between restoring to the throne twice . need is it switch over to the dormancy to waiting original only. Should pay attention to, measurement, give total time used to show is it is it restore to the throne low electricity at ordinary times to smaller than to want, otherwise can39。 Hope too every colleague explore together, improve our design level together. semiconductors make it possible to have high speed and high frequency switching in power electronics ??1 . High speed switching causes weight and volume reduction of equipment, but some unwanted effects such as radio frequency interference appeared ??2 . Compliance with electromagic patibility (EMC) regulations is necessary for producers to present their products to the markets. It is important to take EMC aspects already in design phase ??3 . Modeling and simulation is the most effective tool to analyze EMC consideration before developing the products. A lot of the previous studies concerned the low frequency analysis of power electronics ponents ??4 ??5 . Different types of power electronics converters are capable to be considered as source of EMI. They could propagate the EMI in both radiated and conducted forms. Line Impedance Stabilization Network (LISN) is required for measurement and calculation of conducted interference level ??6 . Interference spectrum at the output of LISN is introduced as the EMC evaluation criterion ??7 ??8 . National or international regulations are the references for the evaluation of equipment in point of view of EMC ??7 ??8 . II. SOURCE, PATH AND VICTIM OF EMI Undesired voltage or current is called interference and their cause is called interference source. In this paper a highspeed switching power supply is the source of interference. Interference propagated by radiation in area around of an interference source or by conduction through mon cabling or wiring connections. In this study conducted emission is considered only. Equipment such as puters, receivers, amplifiers, industrial controllers, etc that are exposed to interference corruption are called victims. The mon connections of elements, source lines and cabling provide paths for conducted noise or interference. Electromagic conducted interference has two ponents as differential mo