March 2001

Electronic design engineers at Delphi Delco Electronics Systems, specialists in mobile multimedia products for automotive use, have solved the problem of solar heating impacting the reliability of their in-car roof-mounted DVD player using Flotherm thermal management software from Flomerics. Housed just 25 mm below the roof of the car, the DVD player was particularly vulnerable to solar heating in stationary vehicles.

The rear-seat system consists of a DVD player in a sheet-metal wraparound housed in a plastic enclosure, which forms part of the roof-mounted console. A fan removes heat from inside the wraparound, cooling the DVD and the four board-mounted linear regulators on the main board.

Using Flotherm to assess the venting system and to predict the airflow path around the DVD's optics, electronic design engineers at Delphi Delco were able to determine the most efficient cooling solutions for the device, which dropped steeply in reliability at temperatures greater than 80°C. It was also important for the regulator junction temperature to stay below 125°C during steady state operation.

Analysis and experiments showed that the thermal resistance of the DVD player depended strongly on the nature of venting, and that system level modelling of the entire airflow path was the best way to estimate optics temperatures.

Using Flotherm from Flomerics, engineers from Delphi Delco were able to predict heat transfer by conduction, convection and radiation simultaneously. Flotherm's SmartParts, such as blocks, resistances, fans and vents, helped Delphi Delco to create a complete system level thermal model quickly.

When the original design was tested, the DVD player ran too hot. Several different design configurations featuring different orientations of baffles and fans were tested before settling on a hybrid approach of reducing power and adding vents. The final optimized design kept the DVD running below its maximum temperature even on a hot sunny day. The final design involved adding a switcher to the circuit, which added to the cost, but eliminated the need to investigate exotic cooling solutions.

"Flotherm simulations guided the design of the enclosure surrounding the mechanism, and extensive experimental studies helped corroborate the results of the analysis", concluded Arvind Krishna from Delphi Delco Electronics Systems.