Design of an adjustable switching regulator driver for DV-S9 diving flashlight, supporting current up to 1 A and input voltage between 3V and 4.2V, along with low standby current. The driver achieves up to 85% efficiency at maximum current. This design is open source hardware.
Post where the design is esplained: https://luicer.github.io/led%20flashlight/Flashlight-Driver-Switching-Eng/