NFC system wakeup with energy harvesting
The present invention provides for a system that makes use of a system power supply enable switch controlled by a near field communications (NFC) frontend with energy harvesting. In one embodiment, RF power in the 13.56 MHz band generated by a NFC counterpart (such as a mobile phone) is detected by the energy harvesting unit being part of the battery-unpowered NFC communication device. After activation, the system can perform actions required to communicate to the presented device (i.e., the NFC counterpart). Later, the system can switch itself into the unpowered state again. In another embodiment, this feature can also be used to control an NFC protection circuitry very quickly after the NFC device is exposed to an external HF (high frequency) field.
1. A method comprising:
detecting, by an energy harvesting unit associated with a near field communication (NFC) system, an active external radio frequency (RF) field;
generating, by the energy harvesting unit associated with the NFC system in response to the detecting, an output signal; and
using the output signal to enable a first switch connected to a battery,
wherein the first switch allows for the battery to provide power to the NFC system,
wherein the first switch is disabled when the energy harvesting unit no longer detects the active external radio frequency (RF) field so that power of the battery is conserved;
generating, by a control module of the NFC system, a power enable signal;
using the power enable signal to enable a second switch to the battery,
wherein the control module is activated when the first switch to the battery is enabled, and the second switch to the battery remains enabled even when the energy harvesting unit no longer detects the active external radio frequency (RF) field; and
disabling, by a second system, the second switch to the battery,
wherein the NFC system comprises a NFC frontend and other parts,
wherein the second system is different from the NFC system,
wherein the second system comprises another NFC frontend and other parts, and
wherein the second system transmits a shutdown request signal to the NFC system.
2. The method of claim 1 , wherein the energy harvesting unit is capable of supplying power to the NFC system without using power from the battery.
3. The method of claim 1 further comprising:
using the output signal to enable a second switch to an NFC protection circuit, wherein the second switch allows for the NFC protection circuit to protect the NFC system.
4. The method of claim 1 , wherein the energy harvesting unit comprises:
a bridge rectifier circuit, and
a blocking capacitor.
5. The method of claim 1 , wherein the energy harvesting unit derives a direct current (DC) voltage out of an alternating current (AC) high frequency (HF) field.
6. The method of claim 1 , wherein the battery is a system power supply.
7. The method of claim 1 , wherein the active external radio frequency (RF) field is generated by an NFC counterpart device.
8. The method of claim 7 , wherein the NFC counterpart device is a mobile phone.