For a wireless inductive charger, I understand the basic operating principle. I have a question regarding the operation of such chargers when no "load" is "connected". How do they detect the presence of a "load" so that the transmitter doesn't constantly have to transmit?

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    \$\begingroup\$ I think it's something with the Qi standard. They transmit constantly but not at full power until a device comes in the field and the phones reacts to the field by communicating with it and telling it it's Qi certified so transmit at full power. \$\endgroup\$ – Simeon R Apr 11 '18 at 12:07
  • \$\begingroup\$ Thank you. So the approach is via some form of digital communication? \$\endgroup\$ – bitshift Apr 11 '18 at 12:09

Have you read this article ?

The transmitter transmits bursts and detects the resulting current flow in the transmit coil. Depending on the value/shape of that current the transmitter can detect if there is a load present, nothing present or a foreign object present.

When a load is present the voltage and current in the transmit can be influenced (modulated) by the load. That way communication can take place. It is almost identical to how RFID and NFC work.

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