This is a DC to DC voltage step up switching module, or sometime is called boost regulator. The maximum input current is at 5A and it is based on LM2587 Boost IC (Maximum efficiency is 92%) and the output voltage is adjustable via on board multi-turn potentiometer.
Input voltage can should be lower than output voltage, please turn the multi-turn potentiometer clock wise to increase the output voltage. Since it is not buck converter (step down), you need to make sure the output voltage is higher than input voltage. Input voltage can be vary from 3.5V to 30V and the output voltage can be adjusted from 4.0V to 30V. Continuous output current can be as high as 3A.
Example application is to boost 5V from USB to power 12V devices.