Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
1999-09-29
2001-04-17
Wong, Peter S. (Department: 2828)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S274000
Reexamination Certificate
active
06218819
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority from prior French Patent Application No. 98-12199, filed Sep. 30, 1998, the entire disclosure of which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electronic circuits, and more specifically to a voltage regulation device for supplying a regulated voltage to integrated circuits in radio-frequency applications.
2. Description of Related Art
In some radio-frequency (RF) applications, an integrated circuit is powered from the RF wave that is transmitted to it. An example of an application of this type is the “contactless smart card”. In this particular application, the card is powered from the RF wave transmitted by a card reader. The microcircuit (i.e., the integrated circuit chip or chips contained in the card) includes particular RF transmission/reception means for communications with a reader, and processing means for processing data such as that contained in the microcircuit memory. These various means must be supplied with a regulated voltage.
The voltage supplied to the internal circuitry must have a certain level that is as stable as possible. This is conventionally obtained by means of a shunt circuit that enables the discharging of the output node if necessary, so as to maintain the level at the output. With such a circuit, the load on the extraction device is permanent. This has an impact on the operable distance of communication between the card and the reader. The greater the power that must be extracted from the RF wave, the smaller the allowable distance between the card and the reader.
SUMMARY OF THE INVENTION
In view of these drawbacks, it is an object of the present invention to overcome the above-mentioned drawbacks and to provide a voltage regulation device with reduced power consumption in order to increase the distance allowed for transmission between a card and a reader.
Another object of the present invention is to provide a voltage regulation device with a reduced power requirement. This reduces the load on the voltage extracted from the RF wave. Thus, the reduced power consumption increasing the operable transmission distance.
One embodiment of the present invention provides a voltage regulation device of the type that receives a voltage transmitted by radio-frequency at an input node and supplies a regulated voltage to electronic circuitry at an output node. The device includes a switching circuit that is coupled between the input node and the output node, and a control circuit that is coupled to the switching circuit. When the voltage level at the output node is below a threshold voltage, the control circuit controls the switching circuit so as to substantially short-circuit the input node and the output node. On the other hand, when the voltage level at the output node is not below the threshold voltage, the control circuit controls the switching circuit so as to substantially isolate the input node from the output node. In a preferred embodiment, the switching circuit includes an NMOS transistor, and the control circuit includes a differential amplifier that supplies a control signal to the gate of the NMOS transistor.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only and various modifications may naturally be performed without deviating from the present invention.
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patent: 5686821 (1997-11-01), Brokaw
patent: 5811861 (1998-09-01), Nunokawa
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patent: 5828206 (1998-10-01), Hosono et al.
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“Sender und Empfänger für die optische NF-Übertragung”, vol. 45, No. 12, Dec. 1, 1996, pp. 70-71, XP000682249.
Preliminary Search Report dated Jun. 23, 1999 with annex on French Application No. 9812199.
Bongini Stephen C.
Fleit Kain Gibbons Gutman & Bongini P.L.
Galanthay Theodore E.
STMicroelectronics S.A.
Vu Bao Q.
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