The design of modern decentralized power systems in telecommunication applications are increasingly realized by using distributed DC/DC power modules. Power modules are usually characterized by high switching frequencies, which enable the use of small ferrite magnetics and ceramic capacitors to enhance the reliability, the power density, and the possibility of live insertion, all desired features in new power system designs. However, to utilize the advantages of power modules there are a number of considerations to be made in the design. These considerations are addressed focusing on telecom systems with an average power dissipation of <10 W/board, in free convection, i.e., nonforced convection, and <80 W/board, in forced convection cooled cabinets of commonly used mechanical sizes and designs for telecommunication equipment.

Applying distributed power modules in telecom systems

A highly efficient, low-profile 300-W power pack is developed for telecommunications systems. To reduce power loss and component size, the power stage is divided into three 100-W on-board power supply modules, each with a simple and efficient MOSFET synchronous rectifier. Efficiency is 90% at 5 V for 60-A output, and power pack width is less than 10 mm. >

A highly efficient, low-profile 300-W power pack for telecommunications systems

A high-efficiency low-profile 30 W power supply module suitable for telecommunications systems, such as the integrated services digital network (ISDN), has been developed This module has an efficiency of 90% and is only 72 mm high A simple MOSFET synchronous rectifier and a low-profile transformer with a flat E core and planar windings were used Its volume is 37 cm/sup 3/ and its power density is 08 W/cm/sup 3/ (13 W/in/sup 3/) It is half the size of a conventional module under natural convection cooling conditions >

A high-efficiency 30 W board mounted power supply module

A low-profile 60 W power pack has been developed for use in telecommunications systems under natural convection cooling conditions. This power pack consists of four newly developed 15 W onboard power supply modules (OBPs). An OBP volume of 25 cm/sup 3/ and an efficiency of 86% are achieved using a 500 kHz resonant reset single-ended forward converter with low loss diodes and Ag thick-film paste for high current conducting. To achieve the smallest possible OBP temperature increase, four OBPs are placed in parallel on the lower side of a card. Using these techniques yields a power pack only 9.2 mm wide, i.e., half the conventional width. Thus, this power pack can be assembled within a 15.24 mm pitch in a bookshelf unit. The circuit and physical design technologies used in this low-profile power pack are described, with special emphasis on the OBP circuit design and natural convection cooling design. >

N. Murakami

Papers

Low-profile 60 W power pack for telecommunications systems