Near field RF communicators having refined energy sharing characteristics utilizing improved shunt current control

• US 9,197,059 B2
• Filed: 10/11/2013
• Issued: 11/24/2015
• Est. Priority Date: 11/15/2007
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Broadcom Europe Ltd (Broadcom, Inc.)
• Inventors: Wilson, Robin
• Primary Examiner(s): HSIEH, PING Y
• Application Number:
  US14/051,538
• Publication Number:
  US 20140036395A1
• Time in Patent Office: 774 Days
• Field of Search: 455/41.1, 455/41.2, 455/41.3, 343/866, 343/867, 343/895, 340/572.1, 323/267
• US Class Current: 1/1
• CPC Class Codes: G05F 1/46 wherein the variable actually regulated by the final control device is dc G05F1/625 takes precedence
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0715 the arrangement including means to regulate power transfer to the integrated circuit
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/10237 the reader and the record carrier being capable of selectively switching between reader and record carrier appearance, e.g. in near field communication [NFC] devices where the NFC device may function as an RFID reader or as an RFID tag
• CPC Class Codes: H02H 7/22 for distribution gear, e.g. bus-bar systems; for switching devices detecting mechanical or electrical defects in gas-insulated switchgears H02B13/065
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/24 Inductive coupling
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

A near field RF communicator has an inductive coupler to enable inductive coupling with a magnetic field of an RF signal; a rectifier to rectify an AC voltage derived from an RF signal inductively coupled to the inductive coupler; and a regulator to regulate a voltage derived from an RF signal inductively coupled to the inductive coupler, the regulator having a voltage-controlled impedance and a regulator controller to provide a control voltage for the voltage controlled impedance and to vary the control voltage in dependence upon a current flowing through the voltage controlled impedance. To prevent the voltage regulator from drawing excess current and energy from an RF field in which the communicator is present the voltage regulator is controlled to provide a chosen impedance characteristic.

Claims

1. A regulator, comprising;

a variable impedance configured to shunt an alternating current in response to a control voltage to regulate a rectified voltage;

an amplifier configured to generate the control voltage in response to the rectified voltage and a feedback voltage; and

a voltage scaler configured to measure the shunted alternating current and to scale the control voltage to provide the feedback voltage such that the rectified voltage is proportional to the shunted alternating current.

2. The regulator of claim 1, wherein the voltage scaler is further configured to measure the shunted alternating current based on a proportionality between the control voltage and the shunted alternating current.

3. The regulator of claim 1, wherein the voltage scaler is further configured to measure the shunted alternating current based on a voltage across a resistance coupled in series with the variable impedance.

4. The regulator of claim 1, wherein the variable impedance comprises:

a first and a second voltage-controlled impedance corresponding to each polarity of the alternating current.

5. The regulator of claim 1, further comprising:

a current mirror configured to sink a current through a resistor in response to the shunted alternating current to provide a node voltage, and

wherein the amplifier is further configured to receive the node voltage at its non-inverting input.

6. The regulator of claim 5, wherein the amplifier is further configured to receive the feedback voltage at its inverting input.

7. The regulator of claim 6, wherein the voltage scaler is coupled between the non-inverting input and an output of the amplifier.

8. The regulator of claim 1, further comprising:

a modulator that effects load modulation by changing a voltage threshold of a voltage regulator.

9. A regulator, comprising:

a variable impedance configured to shunt an alternating current in response to a control signal to provide a regulated rectified voltage from a rectified voltage when operating in a regulating state;

a voltage drop element configured to maintain a proportionality between the rectified voltage and the regulated rectified voltage to provide a rectified current when the variable impedance is operating in a non-regulating state;

an amplifier configured to generate the control signal based on a measurement of the shunted alternating current; and

a demodulator configured to demodulate data based on the control signal when the variable impedance is operating in the regulating state, and to demodulate data based on the rectified current when the variable impedance is operating in the non-regulating state.

10. The regulator of claim 9, wherein the rectified voltage is proportional to the shunted alternating current when the variable impedance is operating in the regulating state.

11. The regulator of claim 9, wherein the voltage drop element comprises:

a second variable impedance configured to provide the regulated rectified voltage in response to the rectified voltage and a second control signal;

a second amplifier configured to provide the second control signal in response to the regulated rectified voltage and a node voltage; and

a current source configured to drive a current through a resistor to provide the node voltage.

12. The regulator of claim 11, wherein the current source is further configured to drive the current through the resistor to hold the node voltage at a predetermined voltage level.

13. The regulator of claim 11, wherein the voltage drop element further comprises:

a current follower circuit configured to provide a follower current that substantially tracks a current through the second variable impedance.

14. The regulator of claim 13, wherein the current follower circuit is further configured to provide the follower current in response to the regulated rectified voltage and the second control signal.

15. The regulator of claim 14, wherein the current follower circuit is further configured to provide the follower current proportional to the rectified current, and wherein the demodulator is further configured to demodulate data utilizing the follower current.

16. A regulator, comprising:

a variable impedance configured to shunt an alternating current in response to a control voltage to regulate a rectified voltage;

a current mirror configured to sink a current through a resistor in response to the shunted alternating current to provide a node voltage;

an amplifier configured to generate the control voltage in response to the node voltage and a feedback voltage; and

a voltage scaler configured to measure the shunted alternating current and to scale the control voltage to provide the feedback voltage such that the rectified voltage is proportional to the shunted alternating current.

17. The regulator of claim 16, wherein the amplifier is further configured with an inverting and a non-inverting input, the non-inverting input being coupled to a first node at the node voltage, and the inverting input being coupled to a second node at the feedback voltage.

18. The regulator of claim 17, wherein the voltage scaler is coupled between the non-inverting input and the second node.

19. The regulator of claim 18, wherein the resistor is coupled between the first node and a third node at the rectified voltage.

20. The regulator of claim 16, wherein the variable impedance comprises:

a first and a second voltage-controlled impedance corresponding to each polarity of the alternating current.

21. The regulator of claim 16, wherein the voltage scaler is further configured to measure the shunted alternating current based on a proportionality between the control voltage and the shunted alternating current.