Patent ID: 7111920

Claim:
A circuit for driving a heater set, the heater set comprising a first heater and a second heater, the circuit comprising: a plurality of current paths, each heater of the heater set being electrically connected to the corresponding current path, the current paths comprising a first current path and a second current path; a bias-voltage-selecting unit, for outputting a first control voltage and a second control voltage; a first primary transistor, electrically connected to the first heater, having a first primary transistor equivalent resistance when the first primary transistor being turned on by applying the first control voltage, and allowing a first current flow through the first heater, the first primary transistor, and the first current path; and a second primary transistor, electrically connected to the second heater, having a second primary transistor equivalent resistance when the second primary transistor being turned on by applying the second control voltage, and allowing a second current flow through the second heater, the second primary transistor, and the second current path, the resistance of the first current path being lower than the resistance of the second current path; wherein the first primary transistor equivalent resistance is higher than the second primary transistor equivalent resistance by adjusting the first control voltage and the second control voltage, thereby causing the thermal energy generated by the first and second heaters to be substantially equal.