I have a bench power supply, that can handle 0-30V up to 5A. It's simple to construct a cable that allows me to connect an USB Type A female plug to the bench supply (or directly a male Micro USB B, or whatever).
However, this will not charge anything with more than 500mA. To let the to-be-charged device know that it can pull more current (or voltage), one of the many signaling standards must be used:
- Fixed voltages on D+ and D-
- USB Battery Charging Specification 1.1 or 1.2
- USB Power Delivery specification
- Qualcomm Quick Charge 2.0 or 3.0
What I would like to see is a universal device that can signal using any of these standards downstream. For the signaling and UI part a micro controller should be used. Voltage regulation and current limitation must also be built. Possibly more than one downstream port could be provided, each one individually controlled.
The actually used D+ and D- values should be displayed; The actual voltage and current as well, plus both integrated over time (to measure e.g. how much mAh go into a power bank in what amount of time).
A subset of this functionality is available in the form of various "YZX Studio" USB Power Meters, by the way.
The device can be used as a simple charger, but would also be very useful for testing purposes.
I can't build one of these, so this is merely an idea for a project 