Supply voltage processing circuit and a data carrier with a supp

Details Supply voltage processing circuit and a data carrier with a supp Supply voltage processing circuit and a data carrier with a supp

1997-06-24

1999-02-23

Wong, Peter S.

Electricity: power supply or regulation systems

Output level responsive

Using a three or more terminal semiconductive device as the...

323281, 363 46, G05F 156

Patent

active

058748296

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a supply voltage regulating circuit, which is intended notably for contactless, passive, inductive data carriers and includes a rectifier, a sustaining capacitor and a direct parallel regulator stage which is connected parallel to the sustaining capacitor; the invention also relates to a contactless, passive, inductive data carrier with an antenna and a supply voltage regulating circuit.
Data transmission systems for the transmission of data between a normally stationary write/read station and a plurality of data carriers are known. The data carriers serve as intelligent, mobile data stores which are used for the writing or reading of data in the near field of write/read stations. Such systems are used with a wide variety of transmission ranges, data transmission speeds, degrees of integration, storage capacities and levels of intelligence of the data carriers etc. for a wide variety of applications such as access control, industrial and commercial object identification, inhibition of ignition, automatic logbook checking etc. A further example in this respect is automatic payment of toll when a vehicle-installed data carrier passes a write/read station of a toll station.
There are data transmission systems with active data carriers (having their own power source), but also data transmission systems with passive data carriers which are powered inductively by an RF signal from the write/read station. After appropriate division, the frequency of the RF signals can be used as the clock signal, so that it is not necessary to transmit an own clock signal. For the transmission of data from the write/read station to the data carrier it is possible to interrupt the RF signal for very brief periods of time: Whether a "0" or a "1" is transmitted is then dependent on the interval between the interruptions; this can be readily determined by the data carrier by counting the clock pulses between two interruptions. The transmission of data from the data carrier to the write/read station can take place by load modulation of the RF signal transmitted by the write/read station. Using only a single signal, it is thus possible to transmit power as well as clock signals from the write/read station to the data carrier and to transmit information in both directions. This system is disclosed in Austrian Patent 395 224.
When a conventional supply voltage regulating circuit, comprising a rectifier, a sustaining capacitor and a direct parallel regulator stage (for example, in the form of a zener diode) connected parallel to the sustaining capacitor, is used for powering the data carrier, the problem is encountered that comparatively long interruptions of the RF signal are required so as to ensure reliable recognition of the interruptions by the data carrier. As has been found in the context of the present invention, such long interruptions are necessary because of the fact that when the RF signal is interrupted, the power supply for the data carrier is provided exclusively by the sustaining capacitor; consequently, the antenna coil is not loaded in any way so that it continues to oscillate for a prolonged period of time because of resonance phenomena. It is a further drawback that the parallel regulator stage must take up comparatively large currents when the data carrier is fed past the write/read station at a very short distance therefrom. Therefore, its regulating speed inherently is comparatively low, so that the voltage regulation is not satisfactory.
It is an object of the present invention to avoid the described drawbacks and to provide a data carrier which is also capable of detecting very short interruptions of the RF signal, so that the speed of transmission of data from the read/write station to the data carrier can be increased. It is another object of the invention to provide a supply voltage regulating circuit which delivers a better stabilized supply voltage. Furthermore, the reliability of the data carrier should be enhanced, notably its insusceptibility to static charges.
According to

REFERENCES:
patent: 5045770 (1991-09-01), Brooks
patent: 5202838 (1993-04-01), Noue
patent: 5262712 (1993-11-01), Klotzig et al.
patent: 5726875 (1998-03-01), Hirabayashi et al.

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