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AC and DC inputs (24 to 250VDC or
88 to 276VAC) and provides a 15V,
800mA (12 W) output from a 100
by 100 mm form factor (making the
power supply suitable for protection
relays that have to be housed in
compact housings).
The power supply uses a two-stage
converter topology comprising a DC-
to-DC step-up (“boost”) regulator
designed around a TI TPS40120
current-mode
controller
which
forms the input to a quasi-resonant
flyback converter designed around a
UCC28740 pulse-width-modulation
(PWM) controller. The output of the
flyback converter forms the 15 V, 0.8
A output from the power supply.
Enabling interoperability
In conventional electricity distribution
grids, infrastructure is operated in
isolation and without gathering any
information about grid performance or
the cause of faults. Full implementation
of a smart grid requires these “dumb”
devices to be replaced with Intelligent
Electronic Devices (IED). In addition
to performing essential electrical
tasks such as transforming voltages,
redirecting energy flows, and isolating
sections of the grid in the event
of faults, IEDs constantly monitor
voltages, currents, power quality, and
other parameters that can affect grid
performance.
This information is passed between
IEDs (such that they can be
automatically activated to correct
abnormal grid operation) and back
to operators (who can then quickly
respond to peaks and troughs in
demand or outages) via dedicated
communication channels. These
communication channels provide
rapid and reliable transmission of
information and rely on wired- and
wireless-technology and Internet,
Ethernet, industry standard, and
proprietary protocols.
The
electricity
distribution
industry is working hard to adopt
a communications standard to
enable interoperability between the
disparate elements of an electricity
grid. The favored standard is IEC
61850, which is already established
for communications in electrical
substations. IEC 61850 is now being
extended beyond the substation to
the Intelligent Electronic Devices
(IED) that make up smart grids.
IEC 61850’s strength is its ability to
rapidly exchange data yet preserve the
original meaning of the information.
As such, the standard promises to
markedly enhance communication
between, and coordination of, smart-
grid infrastructure.
The IEC 61850 Gateway forms a key
part of this communication system
and again TI has stepped in with
chips designed to make the power
supply for these products easier
to develop. The gateway will likely
require multiple power-management
chips to deal with multiple AC and DC
inputs. Figure 3 shows a schematic
with a selection of voltage converters
including a 24/48VDC input/5 VDC
output switching regulator, a 230VAC
input/5 VDC output switching
regulator and 5VDC input/multiple DC
output low-drop-out linear regulator
(LDO).
Another option for gateway power is
a power management IC (PMIC) such
as the TI TPS69510. The PMIC can
accept 5 V Li-ion battery power and
provides three step-down (“buck”)
converters, one boost converter, and
eight LDOs, and is designed to support
the specific power requirements of
OMAP-based applications.
The eight general-purpose LDOs
power the OMAP-based processors,
power to other devices in the system,
and power to DDR memory supplies
in applications requiring these
memories.
Managing consumption
Consumers become familiar with the
concept of smart grids when utility
maintenance crews arrive at their
home to replace antiquated meters
with intelligent units. According
Figure 3: Schematic for IEC 61850 Gateway illustrates requirement for
multiple-voltage regulators. (Courtesy of Texas Instruments)
Figure 4: STMicroelectronics
power supply reference design for
smart-metering applications.
31 l New-Tech Magazine Europe