Two-Step Bootstrap Control for Spike Current Suppression in Switched-Capacitor Converter

Switched-capacitor converters, renowned for their compact size and high power density, have long being considered as an alternative for integrated circuit power supplies. However, the switched-capacitor generates significant spike current during switching transitions, which becomes more severe with increasing load current. The spike current not only leads to increased output voltage ripple but also poses risks to circuit components, limiting their suitability for high-current applications. To address this issue, this paper proposes a novel Two-Step Bootstrap Control Technique that effectively mitigates the spike current without altering the main architecture of the switched-capacitor converter. The proposed circuit was implemented using the TSMC 0.18μm process to validate its functionality. Experimental results demonstrate that the converter delivers a stable output voltage of 1.5V with an input voltage of 3.3V. It achieves a maximum efficiency of 87% with a load current of 500mA. Furthermore, the spike current is reduced from 3.25A to 1.95A at a maximum load current of 1A. Additionally, the converter exhibits an excellent load regulation rate of 0.2mV/mA by employing variable frequency modulation control.