Appliance with an IC card reader and overload protection
The appliance comprises an IC card reader for an operation with an IC card and a power supply for providing a supply voltage, in particular for the IC card. The appliance comprises further an overload protection circuit, which simulates an IC card extraction in case of an overload of the supply voltage. The power supply is then immediately switched off to avoid any damage for the power supply. In a preferred embodiment, the IC card reader is equipped with a card presence switch for indicating to a micro-controller of the appliance, that an IC card has been inserted into the card reader. The micro-controller provides then a control signal for switching on the power supply for the operation with the IC card. The protection circuit is coupled between the supply voltage for the IC card and the signal line of the card presence switch and provides a detection of a short circuit. The protection circuit may comprise a diode, a comparator or a transistor, which switches off the power supply via a logic circuit.
1. An apparatus comprising:
a micro-controller;
an IC card reader including a card presence switch, said card reader supplying an IC card detect signal to said micro-controller when an IC card is inserted into said card reader;
a power supply for providing a supply voltage to said IC card via a mechanical contact terminal of said IC card reader when said IC card is inserted into said card reader, and
an overload protection circuit coupled to said supply voltage which simulates IC card extraction by switching off said supply voltage when an overload of said supply voltage occurs.
2. The apparatus according to claim 1 wherein said overload protection circuit changes said card detect signal from positive to negative when an overload of said supply voltage occurs.
3. The apparatus according to claim 2 wherein said overload protection circuit is further coupled to said card presence switch.
4. The apparatus according to claim 3 wherein said overload protection circuit comprises a diode and a component selected from the group comprising a comparator and a switch, said circuit being arranged for detecting a voltage breakdown of said supply voltage.
5. The apparatus according to claim 1 further including a switching means responsive to a supply voltage “ON/OFF” command provided by said micro-controller for switching on said power supply only when said card detected signal is positive.
6. The apparatus according to claim 5 wherein said switching means is a logic circuit gate.
7. The apparatus according to claim 1 wherein said overload protection circuit provides an error signal when an overload of said supply voltage occurs, said error signal changing via a logic circuit said card detect signal from positive to negative for simulating said IC card extraction.
8. The apparatus according to claim 1 wherein said supply voltage is a supply voltage for said IC card reader.
9. The apparatus according to claim 1 wherein said apparatus is selected from the group comprising: a digital set-top box and a digital satellite receiver, said apparatus including an IC card reader for authorizing reception of pay television broadcast.