Patent ID: 9274739
Filing Date: 2016-03-01
CPC Classification: G06F,G09G,H04N

Claim Text:
1. A source device configured to communicate with a sink device through an HDMI cable, the source device comprising: an energy management circuit configured to charge a battery and provide regulated power to other circuits in the source device; handshaking circuitry configured to measure a voltage level on a hot plug detect (HPD) line of the HDMI cable when initially connected to the sink device and configured to determine, using only the HPD line and a power line of the HDMI cable, whether the sink device can be configured to supply external power on the power line of the HDMI cable to the source device; an internal power supply coupled to provide internal power to the power line when a first switch is closed; and switching circuitry connected to the handshaking circuitry, the switching circuitry comprising the first switch, a second switch and a third switch, the switching circuitry configured to open the first switch to uncouple the internal power supply from the power line when it is determined by the handshaking circuitry that there is a first voltage level on the HPD line and that the sink device can be configured to supply external power to the power line of the HDMI cable, the switching circuitry is further configured to close the second switch to couple to the power line a current measuring circuit configured to determine whether the sink device can supply a supply current to the power line at a current level that is greater than a first predetermined current amount, the switching circuitry is further configured to close the third switch to couple the energy management circuit to the power line when the current measuring circuit determines that the supply current is greater than the first predetermined current amount, the switching circuitry is further configured to switch the first switch to re-couple the internal power supply to the power line when it is determined by the handshaking circuitry that there is a second voltage level on the HPD line, and the switching circuitry is further configured to switch the first switch to re-couple the internal power supply to the power line when the current measuring circuit determines that the sink device is supplying the supply current to the power line at a level that is less than the first predetermined current amount.