Thermal and acoustic management of DVD video recorder

This paper describes the cooling concept of a DVD Video Recorder from both thermal and acoustic point of view. The DVD recorder consists of a cabinet with DVD engine, power supply and analogue and digital boards. In order to guarantee long life it is best to cool the DVD engine by clean air. But free convection cooling is not an option due to temperature problems of the DVD laser and other critical components in the set. A solution to this problem is to supply cool, filtered air to the DVD engine by means of a fan-filter assembly and to cool the rest of the cabinet with appropriate cooling slots in the bottom plate and a fan on the back-plate of the cabinet. While it is not difficult to meet the temperature specification of the DVD laser by appropriate fan choice usually the sound level will be too high. To bring this level down sound power measurements were done in a reverberant room for different combinations of fan voltages. These results are combined with temperature measurements of the delta T of the DVD laser. From the resulting noise-temperature curves an appropriate choice of fan voltages could be made. A temperature sensor in the cabinet senses the outside ambient. At high ambient temperatures the fans ran at higher speed. At lower ambient the fan speed is reduced to keep the noise level of the set as low as possible. A reduction of 10 dBA is obtained up to 28/spl deg/C ambient.