Smart PWM Controller from STMicroelectronics Increases Efficiency and Reduces Costs for Notebook Power Supplies
Current-mode primary controller IC includes advanced standby function, high-voltage start-up with 700V capability, and dedicated PFC interface Geneva / 08 Dec 2005
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Geneva,
December 8, 2005 – STMicroelectronics (NYSE: STM), a world
leader in power ICs, has announced an innovative current-mode primary
controller IC designed to build sin-gle-ended switching power converters.
The L6668’s
advanced functions make it one of the most innovative and efficient controllers
available for power supplies.
Ideally suited for use in high-end AC/DC adapters and chargers for
notebook or laptop PCs, the versatility of the L6668 current-mode PWM
controller also makes it suitable for power supplies of set-top boxes,
DVD players, low-end LCD TVs and other digital consumer equip-ment.
In addition, excellent energy-saving features make the IC a good choice
in low-power auxiliary converters used in high-end LCD and plasma-based
TVs, desktop PCs and server power supplies.
The IC combines a number of functions able to change the way the device
works to optimize power processing under all operating conditions with
excellent electrical characteristics. This combination allows development
of robust and energy-efficient designs.
One of these innovative functions is the interface with the PFC controller
that enables pre-regulator turn off when the load level falls below
a threshold, saving typically 0.5 to 1W of no-load power consumption.
This interface can be easily connected to the RUN or PFC_OK pins of
the ST’s advanced L6563 Power Factor Corrector IC.
In addition, the chip’s high-voltage (HV) technology, when combined
with a multi-chip ap-proach, makes it possible to integrate a high-voltage
start-up system that is connected directly to the rectified mains voltage.
The HV generator is physically located on a separate chip, made with
BCD (Bipolar-CMOS-DMOS) off-line technology able to withstand 700V,
con-trolled by a low-voltage chip, where all of the control functions
reside. This feature, in addi-tion to burst-mode operation and the very
low quiescent current, helps it to be compliant with energy saving recommendations
with minimum usage of external components. Cost and space saving can
be minimized with no compromise on performance.
The L6668 achieves its high level of efficiency by operating in three
different modes, de-pending on the load conditions. At heavy load, the
IC drives the converter at a programmable fixed frequency to optimize
its size and weight. Then, if the load is reduced below a thresh-old,
the switching frequency is adapted to minimize conversion losses. Additionally,
the im-proved Standby function causes a smooth frequency reduction as
the load is progressively re-duced. Eventually, at very light load the
device enters a special operating mode (burst-mode with fixed, externally
programmed peak current) that brings the switching frequency to ex-tremely
low values, hence essentially zeroing all losses related to switching.
Optimum size/efficiency trade-off can be achieved and conversion efficiency
is maximized under all loading conditions, in addition to the on-board
high-voltage start-up. All this means high ef-ficiency benefits with
low dissipation on a light load.
The L6668 also includes programmable soft-start, slope compensation
for stable operation at duty cycles greater then 50%, a disable function,
current sense leading edge blanking to im-prove noise immunity, latched
disable for over-voltage or over-temperature shutdown, and protective
output current limiting in case the secondary diode fails to short circuit.
The new power supply controller is Blue Angel, Energy Star and EU Code
of Conduct com-pliant, and is available now in an SO16 package.
Available in production volumes now, US pricing for the L6668 is $0.40
in quantities of ei-ther 1000 or 2500 for tape-and-reel.
About ST’s Microcontroller, Linear & Discrete Group
STMicroelectronics is a world leader in offering complete system solutions
that leverage its rich portfolio of Microcontroller, Linear, and Discrete
products, advanced process and design technologies, and applications
expertise. This emphasis on solutions allows the Company to minimize
time-to-market for all customers worldwide in existing and emerging
applications.
About STMicroelectronics
STMicroelectronics is a global leader in developing and delivering semiconductor
solutions across the spectrum of microelectronics applications. An unrivalled
combination of silicon and system expertise, manufacturing strength,
Intellectual Property (IP) portfolio and strate-gic partners positions
the Company at the forefront of System-on-Chip (SoC) technology and
its products play a key role in enabling today's convergence markets.
The Company's shares are traded on the New York Stock Exchange, on Euronext
Paris and on the Milan Stock Ex-change. In 2004, the Company's net revenues
were $8.76 billion and net earnings were $601 million. Further information
on ST can be found at www.st.com.