In-Vehicle Electric Control Systems Using Intelligent Power Modules

January 15, 2015 // By Matt Tyler, On Semiconductor
The number of motors used in cars is expected to surpass 200 per car in 2015. As reduced size, weight, and cost will therefore become increasingly important, further integration will be critical.

Increasingly stringent fuel-efficiency regulations and growing concerns about environmental impact have meant that the mechanical systems within vehicles are being supplanted by electrical alternatives.

These enable far higher degrees of efficiency and operational performance to be delivered.

Use of DC motors, for example, is becoming more and more common in the design of in-vehicle control systems (other than the main motor) so that the vehicle's overall weight can be reduced and consequently improvements in fuel economy can be derived. In the case of power steering systems, changing from a hydraulic-actuated system to an electrical one can improve fuel efficiency levels by 3% to 5%.

For in-vehicle systems, brush-less DC (BLDC) motors are seeing wider proliferation as they offer much better reliability than conventional DC motors with brushes and commutators. BLDC motors are incorporated not only into the vehicle's electric power steering system (EPS) but also into its water pumps, oil pumps, fuel pumps, radiator fans, HVAC, seat fans, etc.

Requirements & considerations for in-vehicle motor control

Among the key requirements for in-vehicle motor control circuits are high-temperature operation.

The capability to operate at a Ta of 150 °C and a Tj of 170 °C is essential. High reliability of the entire control circuit in difficult environments is also required.

The more frequently discrete components need to be employed, the larger printed circuit boards will have to become - with increasing number of soldering works, which simultaneously lowers the reliability and increases weight, as well as posing difficulties when taking measures against heat and overall cost. Combatting noise, such as electro-magnetic interference (EMI) -- is also important.

As already outlined, BLDC motors are superior to motors with brushes in terms of their efficiency, maintainability, service life and safety, however they do have the disadvantages of being heavier and higher cost (because BLDC motors require larger mounting space due to inclusion of external control circuits).

As a result, there have been challenges

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