| Isolated DC/DC converters have been moving toward high-frequency,high-efficiency and wide-output range.LLC converter can operate in high frequency and achieve high efficiency because of its ZVS easily achieving.But it has a narrow output voltage range which makes LLC not apply to wide output applications.A phase-shift and PFM multimode control method is introduced in this paper,which applies phase-shift control mode in low voltage output or light load conditions and applies PFM control mode in high voltage output or heavy load conditions,which widen the output range of LLC converter.First the working situation of phase-shift control mode and PFM control mode is introduced and the gain of output voltage is analyzed.This paper presents the control strategy of LLC converter's digital control,and draws flowcharts to make the control process visual and easily understandable.Design method of conventional LLC converter is analyzed in this paper,and optimizing strategy and design method of multimode controlled LLC converter is proposed on the base of it According to the proposed method,a 2.5kW multimode controlled LLC converter is implemented.The experiment results verify the effectiveness of proposed design method,and multimode controlled LLC converter having a better performance than conventional LLC converter. |
PDF Full Text Request