A boost converter can only raise the voltage. The output is always at least the input minus a small drop.
What the message means
These small boards have a trim pot that sets the output. Many arrive set low, and the input voltage passes straight through when it is above the set value.
Fix it in this order
- Check the input polarity and the input voltage range of your module.
- Turn the trim pot slowly while you watch the output with a multimeter.
- Make sure the target output is above the input voltage.
- Keep the load current within the rating at your input voltage, since a boost draws more input current than it delivers.
- Use thick wires on the input and keep them short.
- Check the module for heat.
Why it happens
The MT3608 module is a boost converter. It can only raise the voltage, so the output cannot be lower than the input. The output is set with a small trimmer, and many modules arrive set to a low value.
Check that the input is below the voltage you want, turn the trimmer slowly while watching the output with a multimeter, set the voltage before you connect the load, and check the input current rating and polarity.
If you see this, do this
| You see | Do this |
|---|---|
| Output equals input | Trim pot set too low. |
| No output | Polarity or input too low. |
Related
buck converter sag, set the voltage first.
Last reviewed: November 2026. These are the usual causes and the order that finds them fastest. Test on your own board; clones and cables differ.