Method for a battery and passive power supply to an RFID tag and a switching circuit for carrying out said method

• US 9,239,980 B2
• Filed: 12/16/2009
• Issued: 01/19/2016
• Est. Priority Date: 12/16/2008
• Status: Active Grant

• Current Assignee: ams R&D d.o.o. (Ams-Osram AG)
• Original Assignee: ams R&D d.o.o. (Ams-Osram AG)
• Inventors: Kovacic, Kosta, Pletersek, Anton, Vodopivec, Andrej
• Primary Examiner(s): Phan, Hai
• Assistant Examiner(s): Wu, Zhen Y
• Application Number:
  US13/139,552
• Publication Number:
  US 20110241842A1
• Time in Patent Office: 2,225 Days
• Field of Search: 340/7.32, 340/636.1, 340/635, 340/455, 340/93.2, 320/121
• US Class Current: 1/1
• CPC Class Codes: G06K 19/0702 the arrangement including a battery
• CPC Class Codes: G06K 19/0707 the arrangement being capable of collecting energy from external energy sources, e.g. thermocouples, vibration, electromagnetic radiation G06K19/0702 takes precedence
• CPC Class Codes: G06K 19/0712 the arrangement being capable of triggering distinct operating modes or functions dependent on the strength of an energy or interrogation field in the proximity of the record carrier active means for hindering electromagnetic reading or writing G06K19/07336
• CPC Class Codes: G06K 19/0717 the sensor being capable of sensing environmental conditions such as temperature history or pressure
• 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

Abstract

A controlled switching circuit (csc) comprises two controlled switches (cs1, cs2) fabricated with PINTOS transistors and connected between its output terminal as well as a battery (b) or a rectifier rectifying voltage induced in an antenna. Conditions of the battery voltage and the rectified voltage with a time delay are checked. Only when the battery voltage gets unacceptable and the value of rectified voltage exceeded a preset value tag circuits are supplied by the rectified voltage induced in an antenna.

The invention provides for an automatic selection of a way of supplying an RFID tag in a way that it is stably supplied by a battery as far as still possible, but just according to the invention this is rendered possible for a longer time due to a very low voltage drop across a controlled switching circuit, and that a supply by a radio-frequency radiation field is selected only when the battery gets depleted.

Claims

1. A method for battery power supply and passive power supply to an RFID tag, which is provided with a battery and situated in a radio-frequency radiation field, the method characterized in that the RFID tag comprises a control and memory circuit, and an analog measuring circuit having a sensor, wherein the control and memory circuit and the analog measuring circuit are energized with a battery voltage of the battery and switched to being energized with a rectified voltage obtained by rectifying a voltage induced in an antenna due to the radio-frequency radiation field only when the battery voltage has an unacceptable value and the rectified voltage has reached a preset value,

that a value of the battery voltage is checked

in response to a signal generated for checking the battery voltage, whenever the battery is connected, or

in response to a signal generated by a delay circuit for checking the battery voltage, whenever the rectified voltage reaches the preset value,

that, in case of an acceptable value of the battery voltage,

the control and memory circuit and the analog measuring circuit which are coupled to an output terminal of a controlled switching circuit are energized by the battery through the controlled switching circuit, wherein the controlled switching circuit comprises a first controlled switch fabricated with a first PMOS transistor and a second controlled switch fabricated with a second PMOS transistor,

across which the battery voltage drops by a voltage drop across the conducting first PMOS transistor,

that, in case of an unacceptable value of the battery voltage and after a termination of a time delay after the rectified voltage exceeded the preset value,

the control and memory circuit and the analog measuring circuit are energized by a rectifier rectifying said induced voltage through the controlled switching circuit,

across which the output voltage of said rectifier drop by a voltage drop across the conducting second PMOS transistor,

that a signal indicating good condition of said battery voltage and a signal indicating good condition of said rectified voltage which is time-delayed by the delay circuit are conducted to a logic decision circuit,

and that an output signal of the logic decision circuit either triggers a signal to close the first controlled switch and a signal to open the second controlled switch, when the value of said battery voltage corresponds to said acceptable value, or triggers a signal to open the first controlled switch and a signal to close the second controlled switch, when the value of said battery voltage corresponds to said unacceptable value and the value of said rectified voltage has already reached the preset value, and

wherein a comparator circuit selects a higher voltage between the battery voltage and said rectified voltage and said higher voltage being the highest voltage in the controlled switching circuit is conducted through a logic control circuit to bodies of the PMOS transistors of said first and second controlled switches.

2. The method as recited in claim 1, characterized in that said time delay extends between 5 microseconds and 500 microseconds.

3. The method as recited in claim 1, characterized in that said time delay extends between 10 microseconds and 100 microseconds.

4. The method as recited in claim 2, characterized in that said voltage drop across the conducting first PMOS transistor and across the conducting second PMOS transistor amounts to several millivolts.

9. The method as recited in claim 1, characterized in that the sensor is configured for acquisition of a magnitude of a physical quantity related to a tagged article.

10. The method as recited in claim 1, characterized in that the RFID tag is configured to carry out a measurement, to perform an analog-to-digital conversion of a measuring result, and to store digital data in a non-volatile memory of the RFID tag.

5. A switching circuit for battery power supply and passive power supply to an RFID tag, which is provided with a battery and situated in a radio-frequency radiation field, the RFID tag comprising a control and memory circuit, and an analog measuring circuit having a sensor, and wherein the switching circuit is configured to energize the control and memory circuit and the analog measuring circuit with a battery voltage of the battery and is configured to switch to energize the control and memory circuit and the analog measuring circuit with a rectified voltage obtained by rectifying a voltage induced in an antenna due to the radio-frequency radiation field only when the battery voltage has an unacceptable value and the rectified voltage has reached a preset value, the switching circuit comprising:

a first controlled switch, which is fabricated with a first PMOS transistor and whose first terminal is connected to the battery and whose second terminal is connected to an output terminal of a controlled switching circuit wherein a supply voltage is tapped at the output terminal, and

a second controlled switch, which is fabricated with a second PMOS transistor and whose first terminal is connected to a rectifier output terminal at which the rectified voltage is tapped, and

whose second terminal is connected to the output terminal of the controlled switching circuit,

wherein the controlled switching circuit is coupled via its output terminal to the control and memory circuit and the analog measuring circuit,

wherein a signal for checking the battery voltage is generated, when the battery is connected at a first time moment, and the signal for checking the battery is additionally generated by a delay circuit, when said rectified voltage reaches the preset value at a further time moment after the first time moment,

wherein a signal indicating good condition of said battery voltage and a signal indicating good condition of said rectified voltage that is time-delayed by the delay circuit are conducted to a logic decision circuit,

whose output signal causes a logic control circuit either to close the first controlled switch and to open the second controlled switch, when the value of said battery voltage corresponds to an acceptable value, or to open the first controlled switch and to close the second controlled switch, when the value of said battery voltage corresponds to an unacceptable value and the value of said rectified voltage has exceeded the preset value, and

wherein a comparator circuit selects the higher voltage between the battery voltage and said rectified voltage and said higher voltage being the highest voltage in the controlled switching circuit is conducted through the logic control circuit to bodies of the PMOS transistors of said first and second controlled switches.

6. The switching circuit as recited in claim 5, characterized in that said time delay extends between 5 microseconds and 500 microseconds.

7. The switching circuit as recited in claim 5, characterized in that said time delay extends between 10 microseconds and 100 microseconds.

8. The switching circuit as recited in claim 6, characterized in that a dynamic-reset generator is connected to the output terminal of the controlled switching circuit.

11. The switching circuit as recited in claim 5, characterized in that the sensor is configured for acquisition of a magnitude of a physical quantity related to a tagged article.

12. The switching circuit as recited in claim 5, characterized in that the RFID tag is configured to carry out a measurement, to perform an analog-to-digital conversion of a measuring result, and to store digital data in a non-volatile memory of the RFID tag.

13. A method for battery power supply and passive power supply to an RFID tag, which is provided with a battery and situated in a radio-frequency radiation field,

the method characterized in that the RFID tag comprises a control and memory circuit, and an analog measuring circuit having a sensor, wherein the control and memory circuit and the analog measuring circuit are energized with a battery voltage of the battery and switched to being energized with a rectified voltage obtained by rectifying a voltage induced in an antenna due to the radio-frequency radiation field only when the battery voltage has an unacceptable value and the rectified voltage has reached a preset value,

that a value of the battery voltage is checked

in response to a signal generated for checking the battery voltage, whenever the battery is connected, or

in response to a signal generated by a delay circuit for checking the battery voltage, whenever the rectified voltage reaches the preset value,

that, in case of an acceptable value of the battery voltage,

the control and memory circuit and the analog measuring circuit which are coupled to an output terminal of a controlled switching circuit are energized by the battery through the controlled switching circuit, wherein the controlled switching circuit comprises a first controlled switch fabricated with a first PMOS transistor and a second controlled switch fabricated with a second PMOS transistor,

across which the battery voltage drops by a voltage drop across the conducting first PMOS transistor,

that, in case of an unacceptable value of the battery voltage and after a termination of a time delay after the rectified voltage exceeded the preset value,

the control and memory circuit and the analog measuring circuit are energized by a rectifier rectifying said induced voltage through the controlled switching circuit,

across which the output voltage of said rectifier drop by a voltage drop across the conducting second PMOS transistor,

that a signal indicating good condition of said battery voltage and a signal indicating good condition of said rectified voltage which is time-delayed by the delay circuit are conducted to a logic decision circuit,

and that an output signal of the logic decision circuit either triggers a signal to close the first controlled switch and a signal to open the second controlled switch, when the value of said battery voltage corresponds to said acceptable value, or triggers a signal to open the first controlled switch and a signal to close the second controlled switch, when the value of said battery voltage corresponds to said unacceptable value and the value of said rectified voltage has already reached the preset value,

wherein a comparator circuit selects a higher voltage between the battery voltage and said rectified voltage and said higher voltage being the highest voltage in the controlled switching circuit is conducted through a logic control circuit to bodies of the PMOS transistors of said first and second controlled switches, and

wherein a battery type of the battery is determined and the analog measuring circuit having the sensor is adjusted at a time when the battery is connected to the RFID tag.

14. A switching circuit for battery power supply and passive power supply to an RFID tag, which is provided with a battery and situated in a radio-frequency radiation field, the RFID tag comprising a control and memory circuit, and an analog measuring circuit having a sensor, and wherein the switching circuit is configured to energize the control and memory circuit and the analog measuring circuit with a battery voltage of the battery and is configured to switch to energize the control and memory circuit and the analog measuring circuit with a rectified voltage obtained by rectifying a voltage induced in an antenna due to the radio-frequency radiation field only when the battery voltage has an unacceptable value and the rectified voltage has reached a preset value, the switching circuit comprising:

a first controlled switch, which is fabricated with a first PMOS transistor and whose first terminal is connected to the battery and whose second terminal is connected to an output terminal of a controlled switching circuit wherein a supply voltage is tapped at the output terminal, and

a second controlled switch, which is fabricated with a second PMOS transistor and whose first terminal is connected to a rectifier output terminal at which the rectified voltage is tapped, and

whose second terminal is connected to the output terminal of the controlled switching circuit,

wherein the controlled switching circuit is coupled via its output terminal to the control and memory circuit and the analog measuring circuit,

wherein a signal for checking the battery voltage is generated, when the battery is connected at a first time moment, and the signal for checking the battery is additionally generated by a delay circuit, when said rectified voltage reaches the preset value at a further time moment after the first time moment,

wherein a signal indicating good condition of said battery voltage and a signal indicating good condition of said rectified voltage that is time-delayed by the delay circuit are conducted to a logic decision circuit,

whose output signal causes a logic control circuit either to close the first controlled switch and to open the second controlled switch, when the value of said battery voltage corresponds to an acceptable value, or to open the first controlled switch and to close the second controlled switch, when the value of said battery voltage corresponds to an unacceptable value and the value of said rectified voltage has exceeded the preset value,

wherein a comparator circuit selects the higher voltage between the battery voltage and said rectified voltage and said higher voltage being the highest voltage in the controlled switching circuit is conducted through the logic control circuit to bodies of the PMOS transistors of said first and second controlled switches, and

wherein a battery type of the battery is determined and the analog measuring circuit having the sensor is adjusted at a time when the battery is connected to the RFID tag.