A Hybrid-Hysteresis-CFM Control Method Recursive Switched-Capacitor DC-DC Converter with ripple reduction and load transition enhancement

Abstract

Switched-capacitor power converters (SCPCs) have emerged as promising alternatives to traditional inductive power converters due to their CMOS integration capability and configurable conversion ratios. However, challenges such as output ripple, power efficiency, and transient response have hindered their widespread adoption. This article presents a novel Hybrid Hysteresis-CFM (HHC) control strategy that effectively addresses these issues.

The HHC strategy combines the best of both worlds, integrating hysteresis control and Continuous Frequency Modulation (CFM) control. During transient moments, the system utilizes a coarse/fine frequency tuning approach to rapidly reach the target frequency. Simultaneously, hysteresis control ensures that overshoot and undershoot are kept within predefined limits, significantly reducing output ripple during load transitions.

To enhance performance and versatility, the proposed system employs a Recursive Switched Capacitor (RSC) topology with adaptive capacitor sizing and 10-phase time-interleaving. This configuration enables configurable voltage-conversion ratios (VCRs) and high power conversion efficiency (PCE) across a wide input-output range.

Experimental results validate the effectiveness of the HHC SCPC. It demonstrates minimal overshoot and undershoot during load transition, maintains a low output voltage ripple during steady-state operation, and achieves high PCE. Comparative analysis with state-of-the-art DC-DC converters underscores the superior performance of the proposed system.

In summary, the Hybrid Hysteresis-CFM (HHC) control strategy offers a promising solution to enhance the capabilities of switched-capacitor power converters. Its ability to address output ripple, power efficiency, and transient response challenges makes it a valuable innovation for diverse applications requiring efficient power conversion.