DE102014220394A1 - Transponder arrangement and method for operating a transponder - Google Patents

Abstract

Transponder arrangement with a resonant circuit with an inductance, an ohmic resistance and a capacitance which is connected between a first terminal and a second terminal. The transponder assembly also has a second capacitance connected between the first terminal and a ground terminal. The arrangement is designed to disconnect the second capacitance for a certain period of time from the resonant circuit and to charge it by means of a charging unit and to connect the second capacitance after charging for a certain period of time for discharging the stored charge to the resonant circuit.

Description

The invention relates to a transponder arrangement and a method for operating a transponder, in particular a transponder in a keyless vehicle access and start system.

Many vehicles can be locked or unlocked keylessly today. Keyless vehicle entry and start systems, such as the Passive Start Entry (PASE) system, are automatic systems for unlocking a vehicle without actively using a car key and starting it by merely pressing the start button. Systems for keyless vehicle access are also referred to as keyless entry systems, for example. The driver carries an electronic key with a chip (transponder). The authenticity of this transponder is checked by a base station in the vehicle. For this purpose, data is transmitted between the transponder and the base station.

The data transmission between a base station and a transponder usually takes place by means of inductive coupling between two inductors (antennas). Inductively coupled transponders are usually operated passively. This means that the transponder does not have its own power supply, but the entire energy required for operating the transponder is provided by the base station. From the antenna coil of the base station to a strong high-frequency electromagnetic field is generated. A small portion of this field penetrates the antenna coil of the transponder when it is near the base station. By induction, a voltage is thereby generated at the antenna coil of the transponder, which is used for power supply.

The data transmission from the transponder to the base station can be done for example by means of load modulation. If a transponder is located in the alternating magnetic field of the base station, it deprives the field of energy. The resulting effect of the transponder on the antenna of the base station can be represented as a transformed impedance in the antenna coil of the base station. Turning a load resistor on and off on the antenna of the transponder causes a change in impedance, resulting in voltage changes to the antenna of the base station. To recover the data in the base station, the voltage changes can be evaluated. The transfer of energy from the base station to the transponder takes place continuously in such systems, regardless of the data transmission direction. In this case, full-duplex methods are known in which the data transmission takes place simultaneously in both directions, and half-duplex methods in which the data transmission from the transponder to the base station takes place with a time offset to the data transmission in the other direction.

If the data and energy transmission from the base station to the transponder takes place in a time-delayed manner with the data transmission from the transponder to the base station, this is generally referred to as sequential methods. In this case, the energy transmitted during the data transmission from the base station to the transponder serves to charge a charging capacitor in the transponder as an energy store. The energy stored in the charging capacitor is then used to generate a response to the base station. The transponder generates a weak magnetic alternating field, which is received by the base station.

Such systems are described, for example, in Finkenzeller, Klaus: RFID manual (basics and practical applications of transponders, contactless chip cards and NFC). Munich, 2012, pp. 29-61 ,

However, a disadvantage of known sequential systems is that the energy stored in the transponder is not efficiently used for the subsequent data transmission. Some systems are also very expensive to implement.

The object of the invention is to provide a transponder arrangement and a method for operating a transponder, which are easy to implement and which use the energy stored in the transponder efficiently for data transmission.

The object is achieved by a transponder arrangement according to claim 1 or a method according to claim 14.

The transponder arrangement according to the invention, in particular a keyless vehicle access and start system, has a resonant circuit with an inductance, an ohmic resistance and a capacitance, which is connected between a first terminal and a second terminal. The transponder assembly also has a second capacitance connected between the first terminal and a ground terminal. The arrangement is designed to disconnect the second capacitance for a certain period of time from the resonant circuit and to charge it by means of a charging unit and to connect the second capacitance after charging for a certain period of time for discharging the stored charge to the resonant circuit.

In this way, energy is fed into the second capacity, as long as it is not connected to the resonant circuit. If the capacitance is connected to the resonant circuit, this energy is fed into the resonant circuit. This is possible with little effort and only minor changes to the circuit structure of a transponder. In addition, the energy can be very effectively fed into the resonant circuit.

A switch may be connected between the second capacitance and the first terminal, wherein the switch is configured to connect or disconnect the second capacitance with the resonant circuit.

A series circuit of the charging unit, another switch and an ohmic resistor may be connected in parallel with the second capacitor between the switch and the ground terminal to charge the second capacitor when connected to the charging unit.

The transponder assembly may further include a third capacitance connected between the second terminal and the ground terminal. The arrangement may be further configured to disconnect the third capacitor for a certain period of time from the resonant circuit and charge by means of the charging unit, and to connect the third capacitor after charging for a certain period of time for discharging the stored charge to the resonant circuit, wherein each time a maximum of one of the two capacitances is connected to the resonant circuit.

The resonant circuit is excited when its inductance is exposed to an electromagnetic field.

A voltage across the first capacitance has a sinusoidal shape when the resonant circuit is excited. The second capacitance may be connected to the resonant circuit when the voltage across the first capacitance is negative and the third capacitance may be connected to the resonant circuit when the voltage above the first capacitance is positive. The voltages across the second capacitance and the third capacitance never become negative.

The second capacitance and the third capacitance may each be connected to the resonant circuit for a half-wave of the voltage across the first capacitance. In the resonant circuit thus a current is always fed at the zero crossing of the voltage across the first capacitance and there is an additional charge equalization between the second capacitor and the third capacitor and the first capacitor. In the other half-wave, the capacities can be loaded.

However, the second capacitance and the third capacitance may also be connected to the resonant circuit only for a quarter wave of the voltage across the first capacitance. The second capacitance may be connected to the resonant circuit when the voltage across the first capacitance reaches a positive maximum, and the third capacitance may be connected to the resonant circuit when the voltage above the first capacitance reaches a negative minimum. The charge balance between the capacitors is then always in the zero crossing of the current through the inductor. The voltage across the first capacity is thereby increased by a certain amount at the respective time.

The resonant circuit may be a parallel resonant circuit in which a series connection of the inductance and the ohmic resistance is connected in parallel to the first capacitance between the first terminal and the second terminal.

However, the resonant circuit may also be a series resonant circuit in which the inductance, the ohmic resistance and the first capacitance are connected in series between the first terminal and the second terminal.

A method of operating a transponder includes charging a second capacitor by means of a charging unit for a first predetermined period of time. After charging, the second capacitance is connected to a resonant circuit for a second predetermined period of time. The resonant circuit has a first capacitance, an ohmic resistance and an inductance and is connected between a first terminal and a second terminal.

The method may further include charging a third capacitance by the charging unit for the second predetermined period of time and, after charging the third capacitance, connecting the third capacitance to the resonant circuit for the first predetermined period of time.

The charging of the third capacitance may take place while the second capacitance is connected to the resonant circuit for the second specific period of time, and the third capacitance may be connected to the resonant circuit while the second capacitance is being charged by means of the charging unit.

The invention will be explained in more detail with reference to the embodiments illustrated in the figures of the drawing.

It shows:

1 in a circuit diagram a transponder arrangement with storage capacities,

2 in a schematic diagram of the transponder arrangement 1 in a first state,

3 in a schematic diagram of the transponder arrangement 1 in a second state,

4 in voltage-time diagrams the course of voltages as well as switching states of switches in the transponder arrangement when driving the first and the third switch,

5 in voltage-time diagrams, the course of voltages and switching states of switches in the transponder assembly when connecting the second and third capacitance with the resonant circuit for each half-wave,

6 in voltage-time diagrams, the course of voltages and switching states of switches in the transponder assembly when connecting the second and third capacitance with the resonant circuit for each quarter-wave, and

7 in a flow chart, a method for operating a transponder.

In 1 a transponder arrangement is shown in a circuit diagram. The transponder arrangement can be, for example, parts of a keyless vehicle access and start system. The transponder arrangement has a resonant circuit with an inductance 1 , an ohmic resistance 2 and a capacity 3 on, which is connected between a first terminal A1 and a second terminal A2. The ohmic resistance 2 can also be the resistance of the inductance 1 be. In 1 is the resonant circuit shown as a parallel resonant circuit, that is, that a series circuit of inductance 1 and ohmic resistance 2 parallel to the first capacity 3 is connected between the first terminal A1 and the second terminal A2. However, the resonant circuit can also be designed as a series resonant circuit, in which the inductance 1 , the ohmic resistance 2 and the first capacitance are connected in series between the first terminal A1 and the second terminal A2. Is the inductance 1 in the electromagnetic field generated by a base station (not shown), the resonant circuit is excited.

If the resonant circuit is excited, it forms above the first capacitance 3 a voltage Uc, which has a sinusoidal profile. That is, the voltage Uc applied between the first terminal A1 and the second terminal A2 initially increases until it reaches a (positive) maximum. Thereafter, the voltage Uc decreases again until it reaches a (negative) minimum. Subsequently, the voltage Uc increases again, etc.

The transponder arrangement furthermore has a first switch S1 and a second switch S2. The first switch S1 is in parallel with a series circuit of the second switch S2 and a second capacitor 4 connected between the first port A1 and mass M.

A third switch S1 'is parallel to a series connection of a fourth switch S2' and a third capacitor 6 connected between the second terminal A2 and ground M.

By closing the corresponding switches S2, S2 'can the second capacity 4 and the third capacity 6 be connected to the resonant circuit. By opening the corresponding switches S2, S2 'can the second capacity 4 and the third capacity 6 be separated from the resonant circuit.

A series connection of a second resistor 5 and a fifth switch S3 is between the common node of the second capacity 4 and the second switch S2 and a first terminal of a charging unit 8th connected. A series connection of a third resistor 7 and a sixth switch S3 'is between the common node of the third capacity 6 and the fourth switch S2 'and the first terminal of the charging unit 8th connected. With its second connection is the charging unit 8th connected to mass M. The loading unit 8th For example, a power source, a current-limited voltage source or similar. be, and be trained, the second capacity 4 and the third capacity 6 to charge when this (by closing the respective switch S3, S3 ') with the charging unit 8th are connected.

By correspondingly driving the first switch S1 and the third switch S1 ', it can be achieved that a voltage Ucts between the first terminal A1 and ground M and a voltage Ucts' between the second terminal A2 and ground M never become negative. One possible control of the switches S1, S1 'is shown in the diagrams in FIG 4 shown. First, the voltage Uc is positive, for example. The first switch S1 is closed, which is represented by an H level, while the third switch S1 'is opened, which is represented by an L level. At a time t1, the voltage Uc becomes negative. The first switch S1 is now opened (L level) and the third switch S1 'closed (H level). At a second time t2, the voltage Uc is again positive and the first switch S1 is closed again and the third switch S1 'opened, until a third time t3, the voltage Uc again becomes negative. In this way, the two voltages Ucts and Ucts' never become negative.

Further possible types of control of the switches will be described below also with reference to 2 . 3 . 5 and 6 described.

2 shows in a circuit diagram of the transponder arrangement 1 in a first state. The first switch S1, the fourth switch S2 'and the fifth switch S3 are closed in the first state. The second switch S2, the third switch S1 'and the sixth switch S3' are open. That is, the third capacity 6 connected to the resonant circuit while the second capacitance 4 with the charging device 8th is connected and loaded by them.

Subsequently, the first switch S1, the fourth switch S2 'and the fifth switch S3 can be opened, while the second switch S2, the third switch S1' and the sixth switch S3 'are closed, so that subsequently the second capacitor 4 connected to the resonant circuit while the third capacity 6 with the charging device 8th is connected and loaded by them. This second state of the circuit is shown in the diagram in FIG 3 shown.

For example, the switches can each be closed or opened for the duration of one half-wave of the voltage Uc. This is in the diagrams in 5 shown. From a time t0 to a time t1, the first switch S1 and the third switch S2 'are closed, as in FIG 2 shown. The arrangement is thus in the first state as long as the voltage Uc is positive. The fifth switch S3 is initially still open at time t0 in the present example and is closed only after a short delay time. The voltage Ucts' between the second terminal A2 and ground M and the voltage Uct ', between the common node of the fourth switch S2' and the third capacitor 6 and mass M are positive as long as the assembly is in the first state. The voltage Ucts between the first terminal A1 and ground M is zero, while the voltage Uct between the common node of the second switch S2 and the second capacitor 4 and ground (ie the voltage across the second capacitance 4 ) rises slowly.

At the time t1, when the voltage Uc becomes negative, the device changes to the second state. That is, the first switch S1, the fourth switch S2 'and the fifth switch S3 are opened. The second switch S2 and the third switch S1 'are closed. The sixth switch S3 'is also closed after a short delay time. The voltage Ucts' between the second terminal A2 and ground M is zero. The voltage Ucts between the first terminal A1 and ground M, however, is positive. The voltages Uct and Uct 'are also positive. While the voltage Uct corresponds to the voltage Ucts while the device is in the second state, the voltage Uct 'rises above the third capacitance 6 slowly after closing the sixth switch S3 '.

At a time t2, when the voltage Uc becomes positive again, the device changes back to the first state, etc. Whenever one of the capacitances 4 . 6 connected to the resonant circuit, performs the respective capacity 4 . 6 the resonant circuit to the charge stored in it. Will be the charged capacity 4 . 6 at the zero crossing of the voltage Uc connected to the resonant circuit, an additional current (in addition to the through the inductance 1 in the capacity 3 fed current) fed into the resonant circuit. This allows very efficient power to be fed into the resonant circuit.

In the above example, the second and the third capacity become 4 . 6 each connected to the resonant circuit for a half-wave of the voltage Uc. However, it is also possible, for example, that the switches are switched such that the capacitances 4 . 6 only for a quarter wave of the voltage Uc are connected to the resonant circuit. This is exemplary in the diagrams in 6 shown.

In this case, the third capacity is initially from a time t0 6 through the loading unit 8th loaded (S3 'closed, S2' opened). At time t1, the third capacity becomes 6 connected to the resonant circuit (S3 'open, S2' closed). At a next time t2, a quarter wave after time t1, becomes the third capacity 6 again separated from the resonant circuit (S2 'open). The first switch S1 is closed during the entire period from t0 to t2.

Already shortly before time t1, the fifth switch S3 is closed to the second capacity 4 with the loading unit 8th to connect and charge. From a time t3 to a time t4, a quarter wave after the time t3, the second capacity 4 then unload. With the in 6 shown driving the switch is each of the capacities 4 . 6 every fourth quarter wave for each quarter wave connected to the resonant circuit.

The voltage Uc makes one jump each, if one of the two capacities 4 . 6 is connected to the resonant circuit. The voltage Ucts' between the second terminal A2 and ground M corresponds to the voltage Uc as long as the Voltage Uc is positive. If the voltage Uc is negative, the third switch S1 'is closed and the voltage Ucts' zero. The magnitude of the voltage Ucts between the first terminal A1 and ground M corresponds to the magnitude of the voltage Uc when the voltage Uc is negative. The voltage Ucts is always positive. When the voltage Uc is positive, the first switch S1 is closed and the voltage Ucts is zero.

The voltages Uct and Uct 'over the second capacitor 4 or the fourth capacity 6 begin to increase when the respective switch S3, or S3 'is closed and the charging process begins. Will the respective capacity 4 . 6 from the loading unit 8th disconnected, the respective voltage Uct, Uct 'drops abruptly at first and then drops further to zero during a quarter wave. The charge balance between the first capacity 3 and the second capacity 4 or third capacity 6 takes place in this example in each case at the zero crossing of a current in the first capacity 3 ,

The second and the third capacity 4 . 6 can be dimensioned such that the resonant circuit is tuned to its resonant frequency. The resonance frequency depends on the inductance and the capacitance in a resonant circuit and can be influenced by a change of one of the two variables.

7 shows a flowchart of a method for operating a transponder. Here, first, a second capacity 4 charged for a first period of time (step X1). Subsequently, the second capacity 4 for a second period of time connected to a resonant circuit (step X2). The resonant circuit has an inductance 1 , an ohmic resistance 2 and a first capacity 3 and is connected between a first terminal A1 and a second terminal A2. Optionally, the method may continue to charge a third capacity 6 for the second time period (step X3). Subsequently, the third capacity 6 be connected to the resonant circuit for the first time (step X4). This can be the charging of the third capacity 6 done while the second capacity 4 connected to the resonant circuit for the second period of time. Likewise, the third capacity 6 be connected to the resonant circuit while the second capacitance 4 is charged for the first period of time.

LIST OF REFERENCE NUMBERS

1

 inductance

2

 ohmic resistance

3

 first capacity

4

 second capacity

5

 ohmic resistance

6

 third capacity

7

 ohmic resistance

8th

 charging unit

A1

 first connection

A2

 second connection

M

 Dimensions

Uc

 Voltage above the first capacity

ucts

 Voltage between the first terminal and ground

uct

 Voltage across the second capacitor

ucts'

 Voltage between the second terminal and ground

uct '

 Voltage across the third capacitor

S1

 first switch

S2

 second switch

S1 '

 third switch

S2 '

 fourth switch

S3

 fifth switch

S3 '

 sixth switch

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• Finkenzeller, Klaus: RFID manual (basics and practical applications of transponders, contactless chip cards and NFC). Munich, 2012, pp. 29-61 [0006]

Claims (15)

Transponder arrangement with a resonant circuit with an inductance ( 1 ), an ohmic resistance ( 2 ) and a capacity ( 3 ) connected between a first terminal (A1) and a second terminal (A2) and a second capacitance ( 4 ), which is connected between the first terminal (A1) and a ground terminal (M), wherein the arrangement is adapted to the second capacitor (A1) 4 ) for a certain period of time to separate from the resonant circuit and by means of a charging unit ( 8th ) and the second capacity ( 4 ) after charging for a certain period of time to deliver the stored charge to the resonant circuit. Transponder arrangement according to Claim 1, in which a switch (S2) is connected between the second capacitor ( 4 ) and the first terminal (A1) is connected, wherein the switch (S2) is adapted to the second capacitor ( 4 ) to connect to the resonant circuit or to separate from this. Transponder arrangement according to claim 2, wherein a series circuit of the charging unit ( 8th ), another switch (S3) and an ohmic resistor ( 5 ) parallel to the second capacity ( 4 ) is connected between the switch (S2) and the ground terminal (M). Transponder arrangement according to claim 1, 2 or 3, further comprising a third capacity ( 6 ), which is connected between the second terminal (A2) and the ground terminal (M), and wherein the arrangement is further adapted to the third capacitor ( 6 ) for a certain period of time to separate from the resonant circuit and by means of the charging unit ( 8th ) and the third capacity ( 4 ) after charging for a certain period of time to deliver the stored charge to the resonant circuit, at any one time maximum one of the two capacitances ( 4 . 6 ) is connected to the resonant circuit. Transponder arrangement according to one of the preceding claims, wherein the resonant circuit is adapted to be excited when the inductance ( 1 ) is exposed to an electromagnetic field. A transponder arrangement according to claim 5, wherein a voltage (Uc) across the first capacitance (Uc) 3 ) has a sinusoidal profile when the resonant circuit is excited, and wherein the second capacitance ( 4 ) is connected to the resonant circuit when the voltage (Uc) above the first capacitance ( 3 ) is negative. Transponder arrangement according to claim 6, wherein the third capacity ( 6 ) is connected to the resonant circuit when the voltage (Uc) above the first capacitance ( 3 ) is positive Transponder arrangement according to claim 6 or 7, wherein the second capacitor ( 4 ) and the third capacity ( 6 ) are each connected to the resonant circuit for a half-wave of the voltage (Uc). Transponder arrangement according to claim 6 or 7, wherein the second capacitor ( 4 ) and the third capacity ( 6 ) are each connected to the resonant circuit for a quarter wave of the voltage (Uc). Transponder arrangement according to claim 9, wherein the second capacitor ( 4 ) is connected to the resonant circuit when the voltage (Uc) above the first capacitance ( 3 ) reaches a positive maximum, and the third capacity ( 6 ) is connected to the resonant circuit when the voltage (Uc) above the first capacitance ( 3 ) reaches a negative minimum. Transponder arrangement according to one of the preceding claims, wherein a series circuit of the inductance ( 1 ) and the ohmic resistance ( 2 ) parallel to the first capacity ( 3 ) is connected between the first terminal (A1) and the second terminal (A2). Transponder arrangement according to one of claims 1 to 10, wherein the inductance ( 1 ), the ohmic resistance ( 2 ) and the first capacity ( 3 ) are connected in series between the first terminal (A1) and the second terminal (A2). A method of operating a transponder comprising charging a second capacity ( 4 ) by means of a loading unit ( 8th ) for a first predetermined period of time, after charging, connecting the second capacitor ( 4 ) with a resonant circuit for a second specific period of time, wherein the resonant circuit between a first terminal (A1) and a second terminal (A2) is connected and an inductance ( 1 ), an ohmic resistance ( 2 ) and a first capacity ( 3 ) having. The method of claim 13, further comprising charging a third capacity ( 6 ) by means of the charging unit ( 8th ) for the second predetermined period of time, and after the third capacity has been charged ( 6 ), Connecting the third capacity ( 6 ) with the resonant circuit for the first specific period of time. The method of claim 14, wherein the charging of the third capacitor ( 6 ), while the second capacity ( 4 ) is connected to the resonant circuit for the second predetermined period of time, and the third capacity ( 6 ) is connected to the resonant circuit while the second capacitance ( 4 ) by means of the charging unit ( 8th ) is charged.

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