An innovative digital control architecture for low-voltage, high-current DC-DC converters with tight voltage regulation

This paper describes an innovative digital control architecture for low-voltage, high-current DC-DC converters, based on a combination of current-programmed control and variable frequency operation. The key feature of the proposed architecture is the low-complexity: only two digital-to-analog converters (DACs) with low resolution (7-bit) are used for control. An original control algorithm is used to reduce quantization effects to negligible levels, in spite of the low resolution of the DACs. Thanks to this algorithm, both static and dynamic output voltage regulation are improved with respect to traditional digital solutions. Adaptive voltage positioning and active current sharing are inherently provided by the new architecture. A detailed description of the control strategy is given with reference to a single-phase buck converter. Extension to multiphase converters is straightforward. The digital control architecture is experimentally verified on a FPGA-based four-phase prototype buck converter operating at 350kHz/phase. Output voltage tolerance within +/- 0.5% is experimentally demonstrated, along with negligible quantization effects and fast transient response. The features and the performance of the proposed architecture make it a valuable candidate for the control of next generation voltage regulator modules.