In this paper, we present a load-current-regulating OLED driver for wearable light therapy devices. The driver is based on a single-stage DC-DC hybrid step-up converter architecture achieving high efficiency at a high conversion ratio. The hybrid topology building up the energy through two parallel paths - one with an inductor and the other with a flying capacitor (GFLY1) - reduces the power loss induced by a large DC resistance (R-DCR) of the inductor. Another flying capacitor (C-FLY2), which drives a negative voltage, reduces switching loss by lowering the voltage stress of power switches at a high conversion ratio. More importantly, the proposed single-stage architecture directly regulates the load current to improve efficiency by eliminating the additional current-regulation element, such as a sense resistor or a current source. 93.21% peak efficiency is achieved even with a large R-DCR of 200m Omega at a high conversion ratio of 4.1.