The viability of grid-connected photovoltaic (PV) energy has improved dramatically in recent years: large increases in manufacturing capacity have driven reductions in cost and higher efficiencies, improving lifetime cost of energy (LCOE). Mismatch loss remains an important consideration in PV systems and a range of power electronic solutions have been proposed to recover losses due to shading, dust/debris, factory mismatch and aging. This paper presents a high-voltage CMOS IC and embedded system based on a resonant switched-capacitor converter. The solution is integrated into the junction box to balance power flow in parallel with sub-module strings of PV cells. A custom dual-core cable and connector extend the balancing function to multiple PV modules connected in series, improving energy production of large-scale PV arrays in the case of shading or mismatch. The converter is based on a resonant switched-capacitor (ReSC) topology that achieves effective conversion efficiency over 99% for a wide range of mismatch, insertion loss below 0.1%, a vertical footprint less than 6 mm, and weight less than 1 Oz.