Output Voltage Ripple Analysis and Design Considerations of Intrinsic Safety Flyback Converter Based on Energy Transmission Modes

For the purpose of designing an intrinsic safety Flyback converter with minimal output voltage ripple based on a specified output current, this paper first classified the energy transmission modes of the system into three sorts, namely, the Complete Inductor Supply Mode-CCM (CISM-CCM), the Incomplete Inductor Supply Mode-CCM (IISM-CCM) and the Incomplete Inductor Supply Mode-DCM (IISM-DCM). Then, the critical secondary self-inductance assorting the three modes are deduced and expressions of the output voltage ripples (OVR) are presented. For a Flyback converter with constant loads and switching frequency, it is shown that the output voltage ripple in the CISM-CCM is the smallest and that it has no relationship with the secondary self-inductance. Otherwise, the OVR of the other two modes are bigger than the previously mentioned one. It is concluded that the critical inductance between the CISM-CCM and the IISM-CCM is the minimal secondary self-inductance to ensure the smallest output voltage ripple. At last, a design method to guarantee the minimum OVR within the scales of the input voltage and load are analyzed, and the minimum secondary self-inductance is proposed to minimize the OVR. Simulations and experiments are given to verify the results.