Could HDMI be potentially used as a power supply alternative for smartphones?

Question

I understand that HDMI's pin 18 carries a +5V charge. Similarly, USB carries 5 volts and this is used to charge many smartphones with a micro/usb connector.

Could it possible to build a smartphone that charges with an HDMI port? Would that be completely impractical currently?

Answer 1

The specification of the +5V charge is 50mA(according to wikipedia) This is even lower as USB before enumeration(100mA) Any device wouldn't be able to charge , or it will be very slow at 50mA (10x slower than normal USB port at full power, 500mA)

I don't think the HDMI connectors are specified for high currents in excess of 0.5A. Furthermore, the +5V is probably used in the monior to power some small circuits for identification of itself to the PC/television/etc. , even if it's turned off.

Answer 2

Not really possible right now, HDMI spec shows 55mA on that line. Mostly used to connect to I2C devices on the bus to read the identifier of what the host connected two while the device itself is off: http://www.hdmi.org/learningcenter/kb.aspx?c=13#42

If your device can charge from that low, then yeah it would be possible, but its not what the host would be expecting to happen. Most devices need more than 55mA to power/charge a device at 5V. There may be another rev of the spec in the future to allow more current since more and more devices will likely be using HDMI.

Answer 3

well, for starters +5v 55mA is required to be provided by source device and not receiver - which means your phone would have to act as receiver - for example display what comes from computer on it's screen - etc. No phone I know of acts like that - all of them are source - which means they are ones providing 5v current ;]

Answer 4

Yes it can be. But not with just the HDMI standard. There is the MHL http://en.wikipedia.org/wiki/Mobile_High-Definition_Link standard, which uses HDMI connectors. v1.0 has 5V/500mA, V2.0 has 5V/900mA. It's designed to allow a phone or other device to charge from the main device (TV/Projector) while providing a high bandwidth video/audio link.

Your phone and the source device would have to support MHL to take advantage of that, as there is physical routing inside the phone that needs to be in place.