An Actively Detuned Wireless Power Receiver With Public Key Cryptographic Authentication and Dynamic Power Allocation

This paper presents a CMOS resonant wireless charging receiver with an active detuning mechanism for controlling the received power, without using any passive components being switched in and out. This detuning mechanism is first combined with an on-chip elliptic curve accelerator that achieves $0.77- \mu \text {J}$ /elliptic curve scalar multiplication and in-band telemetry for authenticating a wireless charger using elliptic curve cryptography, with up to $16\times $ rejection at the output of the receiver. Second, equitable power distribution between two receivers coupled to the same charger is demonstrated by controlled detuning of the closer receiver. The system can overcome up to a 4:1 asymmetry in distance to the charger between two receivers. Implemented in 0.18- $\mu \text{m}$ CMOS, the receiver IC delivers 520-mW peak output power and 74% peak end-to-end efficiency in the tuned mode.