Solid state switch with over-temperature and over-current protection

An intake air heating system for an internal combustion engine includes an electric heater that heats the intake air, a control circuit that switches a voltage to the electric heater based on a control signal and an over-temperature signal, a temperature sensor that generates a temperature signal based on a temperature of the control circuit, and a temperature sensing circuit that generates the over-temperature signal based on the temperature signal and a predetermined temperature.