NFC-based enclosure access using passive energy harvesting

A method of unlocking a door of a vehicle having a body, the door, a door actuator, and a remote keyless entry (RKE) control unit, the method comprising:

• inducing an electric current in an inductor coil of an NFC chipset of an NFC entry device, via electromagnetic induction, using an NFC signal from an external NFC-enabled mobile device, wherein the NFC entry device is mounted to the body and includes an NFC receiver integrated circuit (IC) that is coupled to the inductor coil, and wherein the NFC receiver IC includes a steering diode and a voltage regulator;
• storing energy in a capacitor of the NFC chipset of the NFC entry device as passively harvested energy, the capacitor being coupled to the NFC receiver IC;
• establishing near-field communication (NFC) between the NFC entry device and the external NFC-enabled mobile device;
• confirming, via the NFC entry device, that the external NFC-enabled mobile device is an approved device;
• in response to confirming that the external NFC-enabled mobile device is the approved device, selectively powering a radio frequency (RF) antenna of an RF transmitter chipset of the NFC chipset using the energy in the capacitor, via a microcontroller connected to the NFC receiver IC and the capacitor, when a voltage level of the capacitor exceeds a calibrated threshold voltage to thereby transmit a control signal to the RKE control unit, the control signal being indicative of a request to unlock the door from a previously locked state.

A system for remote keyless entry (RKE) into a vehicle having an RKE control unit, a body, a door, and a door actuator configured to unlock and lock the door, the system comprising:

• (i) a near field communication (NFC) entry device configured to permit ingress to and egress from the vehicle via the door in a first manner, the NFC entry device comprising:
• a housing defining a cavity and configured to mount to the body of the vehicle;
• and
• a printed circuit board assembly (PCBA) enclosed within the cavity, comprising:
• a radio frequency (RF) transmitter chipset having an RF antenna;
• an inductor coil;
• an NFC receiver integrated circuit (IC) coupled to the inductor coil, and including a steering diode and a voltage regulator;
• a capacitor coupled to the NFC receiver IC;
• a standby battery;
• a first semiconductor switch;
• a DC-DC converter coupled to the capacitor;
• and
• a microcontroller connected to the NFC receiver IC, the capacitor, and the first semiconductor switch, wherein the NFC entry device is configured to passively harvest energy from an NFC-enabled mobile device in proximity to the NFC entry device, via the inductor coil by operation of the microcontroller, store the energy in the capacitor, and thereafter selectively use the energy in the capacitor when a voltage level of the capacitor exceeds a calibrated threshold voltage to communicate an access control signal to the RKE control unit via the RF antenna and thereby activate the door actuator, and to direct battery energy stored in the standby battery through the first semiconductor switch to thereby communicate the access control signal to the RKE control unit via the RF antenna when the voltage level of the capacitor is less than the calibrated voltage level;
• and
• (ii) an alphanumeric keypad connected to the body of the vehicle and connected to the RKE control unit, the alphanumeric keypad being configured to permit ingress to and egress from the vehicle via the door in a second manner.