With the introduction of the USB Power Delivery (USB-PD) specification, the USB bus can be used to power devices that require high power, such as laptops or mobile phones.
If you take a look at the label of a USB-PD power supply, you will find that it supports different voltage and current values: this is because the specification allows the connected device to negotiate, i.e. request the voltage it needs from those available. I therefore thought about the possibility of using a USB-PD power supply as a basis for building a variable voltage bench power supply.
On the market (Aliexpress) there are modules – named PDC005 – able to “talk” with the power supply and request the right voltage:
By connecting the USB-PD power supply to this module, we can obtain a fixed voltage of 20V. We now need a device to make that voltage adjustable. I chose to use the ZK-4KX module (Aliexpress):
All this, enclosed in a case made with my 3d printer and whose project is available on Thingiverse.
In the following video you will find a detailed explanation of how to build the power supply and how it works… enjoy!