The power system for fifth generation of mobile networks (5G) requires a high level of reliability to be able to support critical internet of things. It has been reported that the interaction between power converters in a power-electronic-based power system can cause system performance degradation or even instability. This paper analyzes the interaction of AC/DC and DC/DC converters at -48VDC interface in a telecom power system based on a source-load impedance model and measured impedances. The study shows that impedance mismatch of the AC/DC and DC/DC converters in a telecom power system can introduce current ringing when working with step load. Impedance shaping is a good solution to minimize the ringing. By defining and modifying critical parameters that have the largest impact on the impedance characteristics of AC/DC and DC/DC converters, the impedance mismatch could be fixed, thus the ringing is limited.