Design Of Medical Power Supply Based On Half-Bridge Resonant Circuit

With the rapid development of medical electronic equipment, more and more medical power will be used. There are some high requirements in performance and reliability for the special applications. At present some problems are valuble of researching such as long dead time, shortage in soft start, and so on.Firstly, this paper builds steady-state model of LLC resonant converter in FHA, then gets its dc gain characteristics. For the MOSFET of half-bridge, the best dead time is welcome. The traditional method is simple in topology but hard to realize the best dead time because of lagging. On contrast, the method based on resonant current is complex in topology and easy to realize dead time controlling. But the reliability of the second method is less than the former.Secondly, this paper finds a new method of APFC compensate circuit. The voltage of traditional compensation circuit rises slowly, along with noise. On the contrary, new circuit makes compensating voltage rise quikly to steady-state value. In that case, the time of over-voltage protecting decrease greatly. At the same time, the new circuit can put compensation voltage down quickly when the output voltage is big lower than steady-state value.Thirdly, this article completes main parameter designing which is the base of futher design. These parameters contain work frequency, resonant inductor and so on. Then, this paper analysis the steady-state and dynamic performance based on LLC small signal model. Here I chooseⅢnetwork as the feedback circuit. Simulation analysis and real circuit experiment get good result.Finally, in consideration of efficiency, this paper proposes an optimized circuit of traditional synchronous tectifier drived by primary signals. Because of setting RC circuit, the off-time of MOSFET was delayed, decreasing conduction time of diode.Through the simulation analysis, ideal result was got. Further more, this paper used a modified clamp circuit to solve miller effect. Simulation analysis and the result of real experiment proved the scheme.