Techniques to Improve the Performance of Wide Operation Range DC-DC Converters

Abstract

A lot of DC-DC converters need to work with a wide operation range. It is challenging for people to achieve a good performance for wide operation range DC-DC converters because of two major reasons. Firstly, when the operation range is wide, the power stage working condition of the DC-DC converter has a big variation. Secondly, a good technique to improve one part of the performance can be bad for another part of the performance. Many techniques have been proposed in the literature to improve the performance of wide operation range DC-DC converters. However, there are still topics which require more research, and more novel techniques can be proposed to further improve the performance of wide operation range DC-DC converters. This dissertation moves forward along this path and makes the following contributions to this research topic. (1) A solution is proposed for the large output voltage variation problem when the spread spectrum function is enabled. This practical clock and ramp generation circuit can eliminate this problem, and allows both the input voltage feed-forward function and the spread spectrum function to be easily implemented together in common IC processes. (2) An adaptive external ramp control method is proposed to improve the bandwidth of peak current mode controlled Buck converters with wide operation range. The transient response is significantly enhanced. (3) The controller design issues are analyzed and the solutions are proposed and verified for Buck converters with phase shedding and adaptive voltage positioning functions. (4) The adaptive device size method is proposed to be applied to a wide operation range regulated charge pump to improve its light load efficiency without sacrificing the output ripple.