Patent Application
20080129268
Radio frequency identification (RFID) chips typically include circuitry that rectifies a carrier wave to generate a regulated power supply for the chip. The carrier wave is generated by a RFID chip reader. The further the reader is from the RFID chip, the weaker the carrier wave is when it reaches the RFID chip. Consequently, the further the reader is from the RFID chip, the lower the voltage and the amount of power available to the chip from the rectified carrier wave. In order to achieve the longest possible read distance, RFID chips are designed to operate at the lowest possible voltage. Operating at a low voltage also reduces the power consumption of the chip since power consumption on the chip is directly related to the operating voltage.
First energy storage element 4 stores energy for application to the integrated circuit. For instance, first energy storage element 4 may store energy at around 1.2 volts for use by an integrated circuit such as a radio frequency identification (RFID) circuit. The energy stored by first energy storage element 4 may be represented by the voltage VDD with respect to a ground 24 for the integrated circuit.
In one embodiment, first energy storage element 4 includes a capacitive element 4, such as single capacitor, a group of capacitors, or any other single device or group of devices that have suitable capacitive properties. Alternatively, first energy storage element 4 includes any other component or element for storing and releasing energy for application to an integrated circuit.
In one embodiment, the energy stored in energy storage element 4 is directly applied to and powers the integrated circuit. In alternate embodiments, the energy stored in energy storage element 4 powers the integrated circuit, but is applied to the integrated circuit through intervening elements, consistent with the operation of the integrated circuit.
Second energy storage element 6 stores energy at a higher voltage than the energy stored by first energy storage element 4. For instance, second energy storage element 6 may store energy at about 4 to 5 volts. Alternatively, second energy storage element 6 may store energy at any multiple of the voltage level of the energy stored in first energy storage element 4, such as one and a half times or two times the voltage level of the energy stored in first energy storage element 4.
In one embodiment, second energy storage element 6 includes a capacitive element 6, such as single capacitor, a group of capacitors, or any other single device or group of devices that have suitable capacitive properties. Alternatively, second energy storage element 6 includes any other component or element for storing and releasing energy at a voltage higher than the energy stored by first energy storage element 4.
Where the first and second energy storage element each include a capacitive element, the capacitance of second capacitive element 6 is greater than the capacitance of first capacitive element 4. For example, the capacitance of first capacitive element 4 is on the order of 50 picoFarads and the capacitance of second capacitive element 6 is on the order of 500 picoFarads. This allows the second capacitive, or energy storage, element 6 to store a energy at a higher voltage than the energy stored by the first capacitive, or energy storage, element 4.
An antenna 14 feeds a carrier wave signal to rectifying circuitry 8. Rectifying circuitry 8 rectifies the signal of the carrier wave to supply energy to second energy storage element 6.
Regulator 10 interconnects the first and second energy storage elements and controls the flow of energy from second energy storage element 6 to first energy storage element 4 to regulate the voltage level of the energy stored in first energy storage element 4. In one embodiment, regulator 10 includes a MOSFET series regulator 10. The current flowing through series regulator 10 is controlled to maintain a desired voltage level for first energy storage element 4.
Shunt regulator 12 regulates the voltage level for second energy storage element 6. In one embodiment, shunt regulator 12 is a MOSFET shunt regulator operated to maintain a desired voltage level across second energy storage element 6.
Any combination of first 4 and second 6 energy storage elements, rectifying circuitry 8, series regulator 10, and shunt regulator 12 may be embodied within the integrated circuit. Additionally, any combination of first 4 and second 6 energy storage elements, rectifying circuitry 8, series regulator 10, and shunt regulator 12 may be embodied with the integrated circuit on a chip.
First capacitive element 4 and second capacitive element 6 are elements of the integrated circuit having capacitance, such as single capacitor, a group of capacitors, or any other single device or group of devices that have suitable capacitive properties. First capacitive element 4 and second capacitive element 6 are arranged in parallel with one another.
In one embodiment, second capacitive element 6 has a greater capacitance than first capacitive element 4. For example, the capacitance of first capacitive element 4 is on the order of 50 picoFarads and the capacitance of second capacitive element 6 is on the order of 500 picoFarads. This allows the second capacitive element 6 to store energy at a higher voltage than the energy stored by the first capacitive element 4.
Each of first 4 and second 6 capacitive elements has first 16, 20 and second 18, 22 terminals. First terminals 16, 20 of first 4 and second 6 capacitive elements are interconnected with circuit ground 24. Second terminal 18 of first capacitive element 4 is applied to the integrated circuit for providing power to the integrated circuit. The power provided to the integrated circuit may be represented by the voltage VDD with respect to a ground 24 for the integrated circuit.
Antenna 14 feeds a carrier wave signal to rectifying circuitry 8. Rectifying circuitry 8 rectifies the signal of the carrier wave to supply energy to second energy storage element 6. In the embodiment illustrated in
Series regulator 10 is interposed between second terminals 18, 22 of first 4 and second 6 capacitive elements. Series regulator 10 is operated to control the flow of energy from second capacitive element 6 to first capacitive element 4 to regulate the voltage level of the energy stored in first capacitive element 4. In one embodiment, series regulator 10 includes a MOSFET series regulator 10. The current flowing through series regulator 10 is controlled to maintain a desired voltage level for first capacitive element 4. Any type of suitable control means 26 may be used to control the gate of MOSFET series regulator 10 in order to control the current flowing through series regulator 10. For example, a feedback control means 26 using as input the voltage VDD may be used to control the gate of series regulator 10.
Shunt regulator 12 regulates the voltage level of the energy stored in second capacitive element 6. Shunt regulator 12 is arranged in parallel with second capacitive element 6 for regulating the voltage level of the energy stored in second capacitive element 6. In one embodiment, shunt regulator 12 is a MOSFET shunt regulator operated to maintain a desired voltage level across second energy storage element 6.
The current flowing through shunt regulator 12 is controlled to maintain a desired voltage level for second capacitive element 6. Any type of suitable control means 28 may be used to control the gate of MOSFET shunt regulator 12 in order to control the current flowing through shunt regulator 12. For example, a feedback control means 28 using as input the voltage across second capacitive element 6 may be used to control the gate of shunt regulator 12.
Any combination of first 4 and second 6 capacitive elements, rectifying circuitry 8, series regulator 10, and shunt regulator 12 may be embodied within the integrated circuit. Additionally, any combination of first 4 and second 6 capacitive elements, rectifying circuitry 8, series regulator 10, and shunt regulator 12 may be embodied with the integrated circuit on a chip.
Energy is stored 36 for application to the integrated circuit. For instance, the stored energy may be stored at around 1.2 volts for use by an integrated circuit such as a radio frequency identification (RFID) circuit. The stored energy may be represented by the voltage VDD with respect to a ground 24 for the integrated circuit. In one embodiment, the energy stored for application to the integrated circuit is stored in first energy storage element 4.
In one embodiment, the energy is stored 36 for direct application to the integrated circuit. In alternate embodiments, the energy is stored 36 for application to the integrated circuit, but is applied to the integrated circuit through intervening elements, consistent with the operation of the integrated circuit.
Energy is stored 38 at a higher voltage than the energy stored 36 in first energy storage element 4. In one embodiment, the energy stored 38 at the higher voltage is stored 38 in second energy storage element 6. In one embodiment, the energy is stored 38 at about 4 to 5 volts. Alternatively, the energy is stored 38 at any multiple of the voltage level of the energy stored in first energy storage element 4, such as one and a half times or two times the voltage level of the energy stored in first energy storage element 4.
The voltage level of the energy stored 38 in second energy storage element 6 is regulated 40. In one embodiment, the voltage level of the energy stored 38 in energy storage element 6 is regulated by shunt regulator 12.
The flow of energy is controlled 42 from second energy storage element 6 to first energy storage element 4 to regulate the voltage level of the energy stored in first energy storage element 4.
In practice, when the carrier wave signal is received by antenna 14, it is rectified by rectifying circuitry 8. The rectified carrier wave signal charges second energy storage, or capacitive, element 6 to a desired voltage level. Series regulator 10 allows current to flow to first energy storage, or capacitive, element 4. The current flow charges first energy storage, or capacitive, element 4 to a desired voltage level. The integrated circuit operates from the voltage VDD across first energy storage, or capacitive, element 4. When the carrier wave signal is no longer received on the antenna, second energy storage, or capacitive, element 6 discharges to maintain the voltage level across first energy storage, or capacitive, element 4. Second energy storage, or capacitive, element 6 is able to discharge from voltage level down to the voltage level of voltage VDD with little or no effect on the voltage VDD across first energy storage, or capacitive, element 4.
The foregoing description is only illustrative of the invention. Various alternatives, modifications, and variances can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention embraces all such alternatives, modifications, and variances that fall within the scope of the described invention.
