It's a small size (5x10mm) 20mA Step-Up CC LED Driver "Joule Thief" for LEDs.
Small size (5x10mm)
The set current has a tolerance of +/- 3mA, depending on the input voltage, temperature, and component tolerance.
Output Voltage up to 15V (LEDs serial connection)
Maximum power dissipation 0.2W (25°C)! (Due to the small size of the PCB)
Automatic shutdown when voltage drops below 0.8-0.9V (No flashing)
No adjustment possible (voltage, current, frequency)
The switching frequency varies based on the input voltage. Approximately 300-500kHz.