Accurate reduced order model to predict temperature for DC/DC driver in convection

DC/DC driver provides the power supply and current to front lighting applications designed in VLS for several LED optical functions. The main power output ranging from 20W to 120W is achieved by several BOOST and BUCK converter stages. The cooling of the different electronic components is mandatory for the reliability under the different operating loads needed. In order to predict accurately and faster the temperature under the different operating points of the driver in voltage input, ambient temperature, a reduced order model based on electro thermal simulations has been defined in natural and forced convection. In order to achieve accurate temperature prediction a new processus has been set up. First the electrical simulation based on the electrical schematics calculates the power losses for the conduction and switching losses for a wide range of components from MOS, diode, IC controller, micro controller and inductors. The power losses predicted by the electrical simulation on MOS have been evaluated with the Rogowski probe. The accuracy on those power loss inputs is then validated by comparing 3D thermal simulation for a PCBA in two different conditions with thermal measurements. Important factors impacting the accuracy of the prediction are identified such as the switching frequency, and the EMC filters. Finally based on the accurate thermal simulation, a reduced order model of a PCBA and driver was then calculated for natural convection and in forced convection. The reduced order model is based on a transient thermal impedance of the PCBA or driver having from 8 to 20 dissipating components. The reduced order model provides a fast and accurate prediction of temperature for all components within 5°C. The temperature evolution as a function of the different output load can be calculated accurately and much faster than 3D thermal simulation.