Digital control of synchronous buck converter with multi-mode for wide load range

Abstract

This paper proposes digital frequency modulation control scheme of synchronous buck converter with boundary conduction mode and digital control strategy for high efficiency over wide load range. Synchronous converter, which can reduce conduction loss through diode, is preferred in high current application. However, this is inefficient at light load condition. Therefore, to achieve the high efficiency over wide range, multi-mode strategy is proposed using digital control. Modes are classified four types, from continuous conduction mode to boundary conduction mode, discontinuous conduction mode and pulse skipping mode as load decreases. The proposed method is implemented by TI's TMS320F28335 DSP chip. For the experimental verification, a 100W synchronous buck converter with 38V input and 20V/5A output is implemented.