Efficient and Cost Effective Driver for HVAC Blower

The Heating, Ventilation and Air Conditioning system (HVAC) blower is present in every car today. In most vehicles and especially in the mid to low cost segment, typically 250W blower motor is driven by a MOSFET used as a variable resistance. Generally seen as cost effective solution, this linear driving mode will generate a peak power loss of 80W to 100W. A more efficient way to drive a motor is to use PWM control. This solution already exists today but was always seen as too expensive for blower motors and thus reserved for mid to high range vehicles.

A PWM controlled solution able to replace the existing linear module will be presented. The system cost is kept similar because no microcontroller is needed in the module embedded in or very close to the blower motor. Electrical, thermal and EMC characterization will also be shown. The benefits for the OEM and the car buyer are clear, a system improvement that will help to reduce electrical power consumption and thus reduce fuel consumption helping to save potential CO₂ emission non compliance cost.