An USB Cable Based Extended Conversion Range L-First Hybrid-Converter using Valley-Virtual-Inductor-Current-Mode Control with Auto-Tracking Slope Compensation against ±50% Inductance Variation

This paper introduces an L-first hybrid converter with extended conversion ratio that uses an USB cable as the power inductor to maximize power density both on-chip and on-PCB. The inductor current, reduced by the conversion ratio, naturally equals the input current, enabling the USB cable to function effectively as an inductor despite its parasitic resistance. The converter achieves an estimated power density of 3.3 W/3mm³ with a peak efficiency of 95%. To accommodate varying USB cable lengths, a valley-virtual-inductor-current mode control with auto-tracking slope compensation is proposed. This scheme eliminates the need for inductor current sensing and adjusts slope compensation based on changes in voltage and inductance. A 5 V input and 1.8–3.3 V output prototype, implemented in a 180 nm BCD process, covers inductances from 500 nH to 1 μH, corresponding to USB cable lengths of 1 to 2 meters.