Research On Wide Output Range Resonant Converter With Constant Output Current

With the development of modern power electronics technology, people put forward higher request to the power supply efficiency and power density. Soft switching technique is the most effective way for improving the power efficiency and power density. In traditional hard switching applications, the switching frequency, which is restricted by the switching loss, is difficult to improve. Compared with the traditional hard switching, soft switching technology can greatly reduce switching loss, improve the operating frequency, so as to improve the converter efficiency and power density.Soft switching converter can be divided into soft switching PWM converter and resonant soft converter. The resonant soft switching converter utilizes the resonant inductance, resonant capacitor in the resonant loop to make the circuit voltage or current periodic zero, providing zero voltage or zero current switching conditions for switching device. The resonant soft switching technology has achieved widespread attention at home and abroad.This paper mainly studies the LCC resonant converter and LLC resonant converter of the gain characteristics. Main parameters of LCC resonant converter and LLC resonant converter are designed, which are applied to wide output range applications with constant output current. For LCC resonant converter, this paper focuses on the influence of parallel resonant capacitor Cp, especially on light load conditons. For LLC resonant converter, this paper focuses on the problems at light load condition, while considering the parasitic parameter of the transformer. At last the magnetic integration technique is used in LLC resonant converter, and simulation analysis is done for LLC converter with integrated magnetics.In this paper three prototypes are completed, they are the LCC resonant converter prototype, LLC resonant converter prototype, and LLC resonant converter with integrated magnetics. The final experimental results show that, compared with LCC resonant converter, LLC resonant converter shows better properties all over the operationrange, especially at light load condition. And the operation frequency range of LLC resonant converter is greatly reduced compared with LCC resonant converter. The power density of LLC resonant converter is further increased by using integrated magnetic technology.Finally the detailed loss analysis and calculation are done, the theoretical calculation results is very close to the experimental results.