Patent ID: 8440942
Filing Date: 2013-05-14
Classification: G05D,H05B

Abstract:
1. A circuit arrangement for protecting from overheating a heating element whose resistance value is a function of its temperature, the circuit arrangement comprising: a switch means; a power supply coupled to the heating element for supplying a current to the heating element by means of the switch means; a switch control circuit with an output for controlling the switch means such that the switch means is switched to a conducting state when the switch control circuit is in a first state and the switch means is switched to a non-conducting state when the switch control circuit is in a second state; a current sensor means coupled to the heating element, the output of the current sensor means providing a signal proportional to the current flowing through the heating element; a first scaling means whose output provides a signal proportional to a supply voltage of the heating element; a first detector means having inputs each coupled to an output of a respective one of the current sensor means and the first scaling means, the first detector means having an output that provides a difference signal formed from the signals of the current sensor means and the scaling means; and an evaluation circuit operable to compare the difference signal determined by the first detector means with a reference signal, wherein the evaluation circuit comprises: