Tutorial
Front-End Power Supplies
Front-end power supplies accept the ac powerline input and convert it to an intermediate switchmode dc voltage that can range from 12 to 48V. The most popular intermediate voltage is 48V that is used by telecommunication systems. The intermediate voltage is bussed throughout the system, connecting to dc-dc converter modules associated with specific subsystems or circuit cards. You can locate the front-end supply either in a card cage or in a convenient place within the system.
One common requirement for front-end supplies is power factor correction (PFC) that lowers the peak currents drawn from the ac line. This reduces the harmonic content fed back into the powerline, which might otherwise interfere with other equipment connected to the same powerline.
Among the features of most front-end supplies are the ability to work over a broad ac input voltage range, for example, 85 to 265Vac. Some front-end supplies may be paralleled to increase the available power. Some paralleled supplies may be combined in a 19-in. rack. Models usually include protection features for overvoltage, overcurrent, short-circuit and overtemperature.
Optional on-board intelligence on some front-end supplies is the ability to communicate with the host computer. Transmitted data can include operational status, such as temperature, current limit, and installation location identification.
Diftributed Power Architecture
The Distributed power architecture (DPA) approach (Fig. 1) converts the incoming ac power to a lower dc bus voltage, normally called a front-end supply. This dc bus voltage can be 12V, 24V, 48V and is usually less than 60V. This bus voltage is distributed throughout the system, connecting to dc-dc converter modules associated with specific subsystems or circuit cards.
The most popular intermediate voltage is 48V used by telecommunication systems. You can locate the front-end supply either in a card cage or in a convenient place within the system.
A typical requirement for front-end supplies is power factor correction (PFC) that lowers the peak currents drawn from the ac line. This reduces the harmonic content fed back into the powerline, which might otherwise interfere with other equipment connected to the same powerline.
Among the features of most front-end supplies are the ability to work over a broad ac input voltage range, for example, 85 to 265Vac. Some front-end supplies may be paralleled to increase the available power. Some paralleled supplies may be combined in a 19-in. rack. Models usually include protection features for overvoltage, overcurrent, short-circuit and overtemperature.
Optional on-board intelligence on some front-end supplies is the ability to communicate with the host computer. Transmitted data can include operational status, such as temperature, current limit, and installation location identification.