An improved Buck converter with high frequency and high step-down ratio for auxiliary power supply applications

Abstract

Buck converter is a good candidate for the non-isolated auxiliary power supply (APS) due to its simple structure and high efficiency. However, it can hardly be adopted in applications that required a very high step-down ratio due to the difficulty to realize an ultra-low duty cycle, especially when the switching frequency becomes higher and higher. Here, an improved Buck converter is proposed for high-frequency and high-step-down-ratio APS application. With the control method based on energy extraction, the proposed topology can achieve an ultra-low equivalent duty cycle. Thus, a high step-down ratio can be achieved under a high switching frequency. Moreover, the proposed structure can be applied on several types of the main power stage through the power switch sharing technique. Finally, the prototype with the switching frequency of 1 MHz and the step-down ratio of 18:1 is verified by the experimental results.