Heating assembly and method for inductively heating an aerosol-forming substrate

An inductive heating assembly configured to heat an aerosol-forming substrate to an operating temperature, the heating assembly comprising:

• a DC power supply configured to provide a DC supply voltage and a DC supply current;
• an induction source connected to the DC power supply and configured to generate an alternating electromagnetic field;
• a susceptor assembly configured to inductively heat the aerosol-forming substrate under influence of the alternating electromagnetic field generated by the induction source, the susceptor assembly comprising a first susceptor including a first susceptor material and a second susceptor including a second susceptor material having a Curie temperature at least 50 degrees Celsius below the operating temperature, wherein the first and the second susceptor materials are chosen such that during pre-heating of the susceptor assembly starting at room temperature a resistance-over-temperature profile of the susceptor assembly has a minimum value of an apparent resistance in a temperature range of ±5 degree Celsius around the Curie temperature of the second susceptor material;
• and
• a controller operatively connected to the induction source and the DC power supply and configured to
• determine from the DC supply voltage and the DC supply current drawn from the DC power supply an actual apparent resistance of the susceptor assembly indicative of an actual temperature of the susceptor assembly,
• determine a minimum value of the apparent resistance occurring during pre-heating of the susceptor assembly starting at room temperature towards the operating temperature, and
• control operation of the induction source in a closed-loop configuration such that the actual apparent resistance corresponds to the determined minimum value of the apparent resistance plus a pre-determined offset value of the apparent resistance to control heating of the aerosol-forming substrate to the operating temperature.