Power supply device, a power receiving device and power supply and receipt methods

A device for receiving power from a remote device over first and second communication lines and for communication with the remote device over the first and second communication lines, comprising:

• a power harvesting circuit for harvesting power from the first and/or second communication lines;
• a first driver for implementing a first communications protocol which comprises coupling the first and second communication lines together to encode a first signal level and isolating the first and second communication lines from each other to encode a second signal level;
• a second driver for implementing a second communications protocol which comprises modulating the first communication line with a signal having a modulation depth below 100%, such that a voltage difference between the first communication line and the second communication line is never zero;
• wherein the second driver comprises a current limiter circuit between power supplied over the first communication line and a shorting circuit for bypassing the current limiter circuit to thereby enable modulating voltage on the first communication line to occur while permitting continuous current supply to the remote device.

A method of transmitting power to a remote device over first and second communication lines and for communication with the remote device over the first and second communication lines, comprising:

• providing power to the first and/or second communication lines;
• and
• selecting between:
• a first communications protocol which comprises coupling the first and second communication lines together to encode a first signal level and isolating the first and second communication lines from each other to encode a second signal level;
• and
• a second communications protocol which comprises modulating the first communication line with a signal having a modulation depth below 100%, such that a voltage difference between the first communication line and the second communication line is never zero;
• thereby enable modulating voltage on the first communication line to occur while permitting continuous current supply to the remote device.

A method for receiving power from a remote device over first and second communication lines and for communication with the remote device over the first and second communication lines, comprising:

• harvesting power from the first and/or second communication lines;
• and
• selecting between:
• a first communications protocol which comprises coupling the first and second communication lines together to encode a first signal level and isolating the first and second communication lines from each other to encode a second signal level;
• and
• a second communications protocol which comprises modulating the first communication line with a signal having a modulation depth below 100%, such that a voltage difference between the first communication line and the second communication line is never zero;
• thereby enable modulating voltage on the first communication line to occur while permitting continuous current supply to the remote device.