USB power

USB as a power supply: a 5 V USB-C or micro-USB breakout, or a PD trigger at 9 to 20 V.

A PD trigger board asks a PD charger for 9, 12, 15 or 20 V. Aliases: USB-C breakout, VBUS, PD trigger, CH224K, IP2721, ZY12PDN.

Pins

Pin	What it does
VBUS	The USB supply.
GND	Ground.

Properties

kind is usb-c, micro-usb, pd-9v, pd-12v, pd-15v or pd-20v.

source is what the cable is plugged into, for the 5 V boards: charger or computer.

kind	source	volts	current
usb-c or micro-usb	computer	5 V	0.5 A, a USB 2.0 port's limit
micro-usb	charger	5 V	1.5 A, a USB Battery Charging 1.2 charger
usb-c	charger	5 V	3 A, a charger offering USB-C current at 3 A
pd-9v to pd-20v	a PD charger	9 to 20 V	3 A

While it runs

The readout is VBUS above GND.

What the model gets right

It is a supply with a limit. The bench supply's model with its knobs fixed at the volts and amps above: the voltage behind 10 milliohm until the load asks for more than the port gives. A 5 ohm load on a computer's port would draw an amp at 5 V; the port holds half an amp and the rail falls to 2.5 V.

What it does not model

Not every trigger chip offers every voltage. The CH224K asks for 5, 9, 12, 15 or 20 V; the IP2721 only for 5, 15 or 20 V, so a 9 V or 12 V board is a CH224K or similar. A PD trigger only gets its voltage from a USB PD charger. Plugged into a computer port or an older charger it stays at 5 V, which the part does not do: source does not apply to the PD kinds, and they always give what they ask for. The negotiation itself, data, a long cable's voltage drop, and the way a real port switches off when it is overloaded are not modeled either.

Common mistakes

Powering a motor or a strip of LEDs from a computer's USB port. Half an amp is not much: use a charger, or a separate supply.

Setting a PD trigger to 20 V and wiring it to a 5 V part. The trigger gives what it was set to as soon as the charger agrees.