The new generation of board mounted modules for telecom

The rapidly increased processing density within switches has caused decisive changes in power supply architecture and design. As a result, two main effects can be observed: board-mounted power supplies have gained more ground, since the single system board becomes a closed functional unit; and the increased power density requires highly efficient low profile power modules, optimized for forced cooling. Following comprehensive studies of a suitable power converter topology, the power supply department of Siemens' Public Switch Division designed a new family of board-mounted DC/DC modules. Employing the advanced thick-film hybrid technology based on ceramic substrates, four basic modules for 5 W, 15 W, 30 W and 60 W have been created. This paper presents this circuit topology based on an f-modulated forward-type power converter with a frequency maximum of 700 kHz. For this purpose, a special control IC has been designed. The main goals of high frequency conversion (such as low profile magnetics, ceramic capacitors, light weight, low profile design) have been fully realised. The technological highlights, such as the dice in globe-top-technique, multilayer hybrid design, active and passive laser trimming, are discussed. The practical results of the present module family are commented upon.<>