Secure element having a light emitting diode
A method is for limiting a voltage in the reverse direction of a light emitting diode is disposed on a secure element. The light emitting diode is electrically connected in parallel to a coil and to operating voltage connectors of an integrated circuit. The coil serves for supplying energy to the integrated circuit and to the light emitting diode because an electrical voltage is induced in the coil with an electromagnetic field produced by an external terminal, and for the contactless data transmission between the integrated circuit and the external terminal. The integrated circuit serves for processing data transmitted between the terminal and the integrated circuit. A shunt regulator regulates the operating voltage required for the operation of the integrated circuit to a value within an allowable range and limits the operating voltage, so a maximally permissible voltage in the reverse direction of the light emitting diode is not exceeded.
1. A method for limiting a voltage in the reverse direction of a light emitting diode of a secure element, the method comprising the steps of:
providing a secure element, the light emitting diode being dispose on the secure element,
wherein the light emitting diode is electrically connected in parallel to a coil and to operating voltage connectors of an integrated circuit,
wherein the coil serves both for supplying energy to the integrated circuit and the light emitting diode in that an electrical voltage is induced in the coil by means of an electromagnetic field produced by an external terminal, and for contactless data transmission between the integrated circuit and the terminal,
wherein the integrated circuit serves for processing data which are transmitted between the terminal and the integrated circuit; and
regulating with a shunt regulator the operating voltage required for the operation of the integrated circuit to a value within an allowable range; and
limiting with the shunt regulator said operating voltage such that a maximally permissible voltage in the reverse direction of the light emitting diode is not exceeded,
wherein the shunt regulator is configured to perform at once both the regulating step and the limiting step.
2. The method according to claim 1 , wherein a minimal operating voltage required for the operation of the integrated circuit is smaller than the voltage that drops in the forward direction at the light emitting diode.
3. The method according to claim 1 , wherein to the light emitting diode at least one electronic component is connected in series in order to increase a voltage drop at the current branch containing the light emitting diode.
4. The method according to claim 3 , wherein in addition to the electronic component an ohmic resistor is connected in series for the current limitation of the light emitting diode.
5. The method according to claim 1 , wherein a switching element is employed to switch the light emitting diode on or off.
6. The method according to claim 5 , wherein the switching element is either integrated in the integrated circuit or is present as a separate component.
7. The method according to claim 5 , wherein the switching element is activated by the integrated circuit or activates itself.
8. The method according to claim 5 , wherein the switching element activates itself through a time control.
9. The method according to claim 1 , wherein the switching element is employed to operate the light emitting diode in pulsed fashion.
10. The method according to claim 1 , wherein the shunt regulator is integrated in the integrated circuit or forms a unit that is separate from the integrated circuit.
11. The method according to claim 1 , wherein the shunt regulator is a voltage-dependent resistor.
12. The method according to claim 1 , wherein a portable data carrier is employed as a secure element.