The aerosol-generating device includes a housing, and a power supply configured to supply electrical power to a heating element by way of a transformer assembly within the housing. The transformer assembly includes a magnetic flux guide, a primary circuit including a primary winding extending around a first portion of the magnetic flux guide and electrically connected to the power supply, and a secondary circuit including a secondary winding inductively coupled to the primary winding and extending around a second portion of the magnetic flux guide. The number of turns in the primary winding is greater than the number of turns in the secondary winding. The secondary circuit includes at least two electrical contacts configured to form an electrical connection with the heating element.