Abstract：In order to address the issue of large output voltage variation from self-powered current transformer

in smart measurement switch，ultra wide input voltage range post-stage DC-DC module is required to generate

stable system voltage rails. A ultra wide input DC-DC module based on constant on-time control and asynchronous

Buck circuit operating in discontinuous mode was proposed. Accroding to the gap between intput voltage and

output voltage，variable frequency control and quasi-fixed freqency control were combined. With large voltage gap

conversion realized，this DC-DC module also features super fast dynamic response. PSIM software was used to

analyze and verify the characteristics of the propsed DC-DC module. A 5 W hardware prototype was fabricated and

tested to produce key experimental waveforms. The experimental results demonstrate that the proposed DC-DC

module has features of ultra wide input range，super fast dynamic response and high stability.

      Key words：smart measurement switch；ultra wide input range；constant on-time；discontinuous conduction

mode；DC-DC module