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Application Bulletin AB-28
Power Conversion for the Data
Communications Market
Abstract
This application bulletin discusses the transition from tradi-
tional telephony to converged voice and data over Internet
Protocol (IP) and its implications for the power conversion
of such systems. A few power conversion examples are pro-
vided complete of applications schematics.
Migration to Converged Voice/
Data IP
Fig. 2 shows the envisioned converged Voice/Data/Video
system over IP. At the center of this new universe is the
Internet Protocol Wide Area Network, with all the services,
including voice, data, video and wireless communications
gravitating around it.
Introduction
The arm wrestling between voice and data has concluded in
favor of the latter with all the major players now posturing
for leadership of the migration from traditional voice to
Internet Protocol (IP) telephony. On the short term the huge
investments in both traditional telephony infrastructure and
data over IP warrants that over the next few years we will
have to provide power conversion for both types of systems
as well as for the converged systems to come.
WLAN
Router
IP WAN
Video
PSTN
IPWAN = Internet Protocol Wide Area Network
WLAN = Wireless Local Area Network
PSTN = Public Switched Telephone Network
Current Environment with Separate
Networks
Fig. 1 shows the current situation with voice going through
traditional PBX (Private Branch Of鏗乧e), Central Of鏗乧e, and
Switch to the Public Switch Telephone Network (PSTN). On
independent paths the data travels from Routers to wide Area
Networks (WAN) and the video goes trough a third indepen-
dent path.
Fig. 2. Voice/Data/video Over IP
Telecom 鈥?8V DC Power Distribution
Traditionally telecom systems have been distributing a DC
power (-48V typically) obtained from a battery back up
being continually charged by a Recti鏗乪r/Charger from the
AC line. Subsequently the 鈥?8V is converted into various
low positive DC voltages (Fig. 3 shows 12V only for
simplicity) as well as back to AC voltages as necessary.
Home
Phone/Fax
Central
Office
Office PBX
(Private Branch
Exchange)
Voice
Switch
Public Switch
Telephone
Network (PSTN)
AC LINE
-48V
DC/DC
12V DC
Router
Data
Wide Area
Network
(WAN)
Rectifier
/Charger
Battery
Backup
-48V
DC/AC
120/208V AC
Video
Video
Video
Fig. 3. Telecom 鈥?8V DC power distribution
Fig.1. Separate Networks for Voice, Data and Video
Datacom AC Power Distribution
Data centric systems tend to rely on an Uninterruptible
Power Supply (AC UPS) front-end for distributing AC
power, which subsequently is converted into the basic
constituents, -48V, AC power and low voltage DC (again,
for simplicity we are only showing a 12V DC in Fig. 4).
REV. 1.0.0
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