Circuit arrangement and method for supplying power to a transponder

• US 20060187049A1
• Filed: 02/09/2006
• Published: 08/24/2006
• Est. Priority Date: 02/09/2005
• Status: Active Grant

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Germany GmbH (Microchip Technology Incorporated)
• Inventors: Moser, Daniel, Moser, Helmut
• Granted Patent: US 7,535,362 B2
• Time in Patent Office: Days
• US Class Current: 340/572.500
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card

Abstract

A circuit arrangement is provided for a power supply to a transponder including an antenna resonant circuit and a downstream rectifier circuit for receiving and for rectifying an electromagnetic signal, a charging capacitor connected downstream on the output side of the rectifier circuit to provide a first supply voltage, with a tuning circuit for tuning the antenna resonant circuit to its resonance frequency, and with an auxiliary voltage source, which is designed to provide a second supply voltage, lower than the first supply voltage, for supplying the tuning circuit. A method is also provided for supplying power to a transponder with a first supply voltage, as well as a transponder having a circuit arrangement for a power supply.

Claims

1. A circuit arrangement for a power supply to a transponder, the circuit arrangement comprising:

an antenna resonant circuit and a downstream rectifier circuit for receiving and for rectifying an electromagnetic signal;

a charging capacitor connected downstream of an output side of the rectifier circuit to provide a first supply voltage;

a tuning circuit for tuning the antenna resonant circuit to a resonance frequency; and

an auxiliary voltage source for providing a second supply voltage that is lower than the first supply voltage to the tuning circuit.

2. The circuit arrangement according to claim 1, wherein the auxiliary voltage source has an auxiliary capacitor which is provided between outputs of the rectifier circuit and inputs of the tuning circuit, and which has a lower capacitance than the charging capacitor.

3. The circuit arrangement according to claim 1, wherein the charging capacitor has a capacitance in the range of 0.5 μ

F to 5 μ

F and/or the auxiliary capacitor has a capacitance in the range of 50 pF to 500 pF.

4. The circuit arrangement according to claim 1, wherein an at least two-phase charging circuit is provided that has a first charging phase for charging an auxiliary capacitor to the second supply voltage and a second charging phase for charging the charging capacitor to the first supply voltage, the second charging phase charging the charging capacitor only when a predefinable charging threshold of the second supply voltage is exceeded.

5. The circuit arrangement according to claim 4, the charging circuit has at least one controllable switch, which is placed in series between an output connection of the rectifier circuit and an electrode connection of the charging capacitor.

6. The circuit arrangement according to claim 4, wherein the charging circuit has a drive circuit, which has a control signal for turning a digitally operated controllable switch on and off on the basis of the second supply voltage and the predefinable charging threshold.

7. The circuit arrangement according to claim 4, wherein the charging circuit has a bandgap control circuit that has a reference potential for triggering a controllable switch, which is formed as a transistor and operated in an analog characteristic region, depending on the second supply voltage and depending on a switching potential of the transistor.

8. The circuit arrangement according to claim 1, wherein the antenna resonant circuit has at least one antenna coil and a first capacitive element in a parallel connection.

9. The circuit arrangement according to claim 1, wherein the tuning circuit has a memory or an EEPROM, in which information for tuning a first capacitive element of the antenna resonant circuit is stored.

10. The circuit arrangement according to claim 1, wherein the tuning circuit has at least one additional capacitive element, which is connectable via at least one switching device and is arranged parallel to one another and to the first capacitive element and of which at least one can be connected to the first capacitive element.

11. A method for supplying power to a transponder with a first supply voltage, the method comprising the steps of:

tuning, during a first operating mode, a first capacitive element of a receiving-side antenna resonant circuit to its resonance frequency and during which a charging capacitor remains inactive; and

charging, during a second operating mode, the charging capacitor to provide the first supply voltage.

12. The method according to claim 11, further comprising the steps of:

(a) providing an at least partially discharged, inactively connected charging capacitor of a transponder;

(b) receiver-side receiving and rectification of an electromagnetic signal;

(c) charging an auxiliary capacitor with a rectified current signal for providing a second supply voltage lower than the first supply voltage;

(d) tuning a receiver-side antenna resonant circuit to its resonance frequency based on the second supply voltage until the antenna resonant circuit is tuned;

(e) connecting the charging capacitor; and

(f) charging the charging capacitor to provide the first supply voltage of the transponder.

13. The method according to claim 11, wherein, to activate the charging capacitor, a controllable switch is switched on only if the second supply voltage has reached and/or exceeded a predefinable charging threshold.

14. The method according to claim 11, wherein the antenna resonant circuit is tuned to the resonance frequency of the antenna resonant circuit by parallel connection or disconnection of additional capacitive elements.

15. The method according to claim 12, wherein the tuning in step (d) occurs with the use of previously stored tuning information.

16. The method according to claim 12, wherein the tuning information is stored before process step (c) and/or particularly before the first and second operating mode, the tuning information being determined transmitter-side from the frequency of the transmitted electromagnetic signal received by the transponder.

17. The method according to claim 11, wherein the antenna resonant circuit is activated by an LF signal or by a 125-kHz frequency signal.

18. A transponder for a tire pressure control system, the transponder comprising:

a receiving path in which a circuit arrangement is located for power supply to the transponder, the circuit arrangement comprising;

an antenna resonant circuit and a downstream rectifier circuit for receiving and for rectifying an electromagnetic signal;

a charging capacitor connected downstream of an output side of the rectifier circuit to provide a first supply voltage;

a tuning circuit for tuning the antenna resonant circuit to a resonance frequency; and

an auxiliary voltage source for providing a second supply voltage that is lower than the first supply voltage to the tuning circuit.

19. The transponder according to claim 18, wherein the transponder further comprises:

a sensor for detecting tire-specific parameters;

an analog-digital converter, which converts an analog signal with the tire-specific parameters into a digital signal;

an encoder, which encodes the digital signal; and

a modulator, which modulates the encoded signal.

20. The transponder according to claim 19, wherein the sensor is a capacitive pressure sensor for tire pressure measurement.