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

摘要

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.

主权项

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.