Design of pulse width modulation based smart switch controller for automotive applications

This paper presents an improved design of a Pulse Width Modulation (PWM) controller for controlling the blower motor in the Heat Ventilation and Air Conditioning (HVAC) applications of an automobile. The design employs a smart switch instead of the conventional power MOSFET. This smart switch is a monolithic device with built-in protection features such as thermal shutdown, linear current limitation, short circuit protection and over-voltage clamp. This switch thus eliminates the protection circuitry required around the power MOSFET. The computer models generated for both the design methodologies (with power MOSFET and with smart switch) in SABER simulation package are presented. These models have been validated against experimental data. The paper contains a comparison of the two design schemes in terms of the size and number of components required.