Method for detecting overheating of a heating device, and corresponding control unit

A control unit for an electrical heating device comprising a plurality of resistive elements configured to be electrically supplied by an electrical voltage source, the control unit being configured to generate a pulse-width modulated drive signal for driving the electrical supply of the resistive elements depending on a power setpoint, or a temperature setpoint, or a resistance setpoint for an amplitude of an electrical current, the control unit comprising at least one computer configured for:

• noting the setpoint;
• noting a duty cycle of the pulse-width modulated drive signal of a predefined number of resistive elements;
• defining a detection threshold value of the duty cycle of the pulse-width modulated drive signal of the predefined number of resistive elements, the detection threshold value being representative of overheating of the electrical heating device, depending on the setpoint or on a value of at least one parameter for monitoring overheating of the electrical heating device;
• comparing the noted value of the duty cycle to the detection threshold value;
• detecting a cold state with a thermal probe, and
• detecting overheating when the noted value of the duty cycle reaches the defined duty-cycle detection threshold value,
• wherein the at least one parameter is measured with a sensor;
• wherein the sensor comprises at least one of a current sensor and a voltage sensor, and
• wherein the control unit is configured to verify whether a criterion of the electrical heating device is representative of the cold state of the electrical heating device, and inhibit at least the step of detecting the overheating based on the verification,
• wherein at least one of the plurality of resistive elements comprises a positive temperature coefficient (PTC).