Voltage regulation of near field communication communicators
View Patent ↗A NFC enabled device to couple inductively to the H field of an RF signal and a regulator to regulate a voltage derived from an RF signal inductively coupled to the inductive coupler. The regulator has at least one voltage controlled impedance having a switch on voltage. A regulator controller provides a control voltage to each voltage controlled impedance such as that the control voltage is not less than the switch on voltage of the voltage controlled impedance.
1. A near field communications (NFC) enabled device, comprising:
a rectifier configured to rectify an output of an antenna circuit to provide a rectified output; and
a regulator configured to regulate an output of the antenna circuit based upon the rectified output, the regulator comprising:
an amplifier configured to determine a difference between the rectified output and a reference voltage to provide a control signal, the amplifier comprising:
a differential transistor pair, wherein each transistor of the differential transistor pair configured to be a respective amplifier input,
a first transistor and a second transistor configured to draw a bleed current,
a first current mirror configured to couple the differential transistor pair to a voltage source;
a second current mirror and a third current mirror respectively coupled to the first transistor and the second transistor; and
a voltage setter configured to combine the bleed current with the control signal; and
a plurality of voltage controlled impedances configured to regulate the output of the antenna circuit based upon an output of the voltage setter, wherein:
the bleed current causes the plurality of voltage controlled impedances to be active; and
each of the plurality of voltage controlled impedances couples a respective output of an antenna circuit to ground.
2. The NFC enabled device of claim 1 , wherein each of the plurality of voltage controlled impedances comprises:
a metal oxide semiconductor field-effect transistor (MOSFET); or
a bipolar junction transistor (BJT).
3. The NFC enabled device of claim 1 , wherein the voltage setter comprises:
a third transistor and a fourth transistor configured as a current mirror, the fourth transistor being configured to mirror a reference current that flows through the third transistor to provide the bleed current.
4. The NFC enabled device of claim 3 , wherein the voltage setter further comprises:
a fifth transistor configured to cause the reference current to flow through the first transistor.
5. The NFC enabled device of claim 4 , wherein the output of the voltage setter is greater than a threshold voltage of the fifth transistor.
6. The NFC enabled device of claim 5 , wherein thresholds of the plurality of voltage controlled impedances are substantially equal to the threshold voltage of the fifth transistor.
7. The NFC enabled device of claim 4 , wherein the voltage setter is further configured to ensure that a voltage difference between the control signal and an electrode of one of the plurality of voltage controlled impedances is not less than a threshold voltage of the fifth transistor.
8. The NFC enabled device of claim 1 , wherein the amplifier comprises:
a differential amplifier configured to determine the difference between the rectified output and the reference voltage.
9. The NFC enabled device of claim 1 , wherein the antenna circuit is configured to receive an inductively coupled communication to provide a recovered communications signal.
10. The NFC enabled device of claim 9 , wherein the regulator is further configured to regulate a power level of the recovered communications signal.
11. The NFC enabled device of claim 10 , further comprising:
a demodulator configured to demodulate the recovered communication signal to provide recovered information.
12. The NFC enabled device of claim 1 , wherein the amplifier further comprises:
a current source configured to set the bleed current and a tail current in the amplifier;
a fourth current mirror configured to draw a current from the second and third current mirrors; and
a third transistor coupled between the third current mirror and the fourth current mirror.
13. A near field communications (NFC) enabled device, comprising:
a receiver configured to receive a communications signal;
a rectifier configured to rectify an output of the receiver to provide a rectified output; and
a regulator configured to regulate an output of the receiver based upon the rectified output, the regulator comprising:
an amplifier configured to a difference between the rectified output and a reference voltage to provide a control signal, the amplifier comprising:
a differential transistor pair, wherein each transistor of the differential transistor pair is configured to be a respective amplifier input,
a first transistor and a second transistor configured to draw a bleed current,
a first current mirror configured to couple the differential transistor pair to a voltage source;
a second current mirror and a third current mirror respectively coupled to the first transistor and the second transistor; and
a voltage setter configured to combine a bleed current with the control signal; and
a plurality of voltage controlled impedances configured to regulate the output of the receiver based upon an output of the voltage setter, wherein:
the bleed current causes the plurality of voltage controlled impedances to be active; and
each of the plurality of voltage controlled impedances couples a respective output of an antenna circuit to ground.
14. The NFC enabled device of claim 13 , wherein each of the plurality of voltage controlled impedances comprises:
a metal oxide semiconductor field-effect transistor (MOSFET); or
a bipolar junction transistor (BIT).
15. The NFC enabled device of claim 13 , wherein the receiver is configured to receive an inductively coupled communication to provide a recovered communications signal.
16. The NFC enabled device of claim 15 , wherein the regulator is configured to regulate a power level of the recovered communications signal.
17. The NFC enabled device of claim 16 , further comprising:
a demodulator configured to demodulate the recovered communication signal to provide recovered information.
18. The NFC enabled device of claim 13 , wherein the amplifier further comprises:
a current source configured to set the bleed current and a tail current in the amplifier;
a fourth current mirror configured to draw a current from the second and third current mirrors; and
a third transistor coupled between the third current mirror and the fourth current mirror.
19. A near field communications (NFC) enabled device, comprising:
a host device; and
a NFC device coupled to the host device, the NFC device comprising:
a rectifier configured to rectify an output of an antenna circuit to provide a rectified output; and
a regulator configured to regulate an output of the antenna circuit based upon the rectified output, the regulator comprising:
an amplifier configured to determine a difference between the rectified output and a reference voltage to provide a control signal, the amplifier comprising:
a differential transistor pair, wherein each transistor of the differential transistor pair is configured to be a respective amplifier input,
a first transistor and a second transistor configured to draw a bleed current,
a first current mirror configured to couple the differential transistor pair to a voltage source;
a second current mirror and a third current mirror respectively coupled to the first transistor and the second transistor; and
a voltage setter configured to combine a bleed current with the control signal; and
a plurality of voltage controlled impedances configured to regulate the output of the antenna circuit based upon an output of the voltage setter, wherein:
the bleed current causes the plurality of voltage controlled impedances to be active; and
each of the plurality of voltage controlled impedances couples a respective output of an antenna circuit to ground.
20. The NFC enabled device of claim 19 , wherein the host device comprises a mobile telephone.
21. The NFC enabled device of claim 19 , wherein the host device comprises a portable computer.
22. The NFC enabled device of claim 19 , wherein the host device comprises:
a long range communicator configured to transmit or receive a communications signal outside a maximum operable range of NFC.
23. The NFC enabled device of claim 19 , wherein the amplifier further comprises:
a current source configured to set the bleed current and a tail current in the amplifier;
a fourth current mirror configured to draw a current from the second and the third current mirrors; and
a third transistor coupled between the third current mirror and the fourth current mirror.