On November 15, a Texas jury decided the lawsuit
brought by Power-One against Artesyn Technologies
(now part of Emerson Network Power) in 2005. The
decision has ramifications for engineers who design power systems
that step down a bus voltage at a “point of load” such as
an FPGA or processor. Immediately after the verdict, both companies
issued positive statements to the press.
“The jury found both of the two asserted patents to be valid
and found that Power-One’s U.S. Patent No. 7,000,125... has
been infringed by the Artesyn Technologies product,” noted
Power-One.
Emerson said that “a Texas jury found that only one patent
was infringed involving a product that Artesyn had never sold,
never offered for sale and that the market has never used....
The jury specifically determined that any infringement was not
willful. If the court enters judgment on the verdict, a total of
$100 in damages will be awarded to Power-One.”
Now there can be peace in the valley, right? Not so fast.
WHAT’S A POL?
The first thing to understand is that the
suit was exclusively about using point-of-load voltage converters
(POLs). That’s because the judge in the case made the parties
agree on the definition of a POL to give the jury something
narrow to focus upon.
Explicitly, for this suit, the jury was told that a point-of-load regulator
means a dc-dc switching voltage regulator designed to
receive power from a voltage bus on a printed-circuit board,
adapted to power a portion of the devices on the board, and
placed near the one or more devices being powered as part of a
distributed board-level power system. That means the case is not
about bricks and ac-dc supplies.
Over the past few years, POLs have evolved. In early POLs,
the voltage-regulation control loop was analog, limits were set
via external pull-downs, and turn-on/turn-off sequencing was
accomplished simply by connecting a wire from the “voltage
good” pin of one device in the sequence to the “chip enable” of
the next. These POLs are still used.
But a “digital power” paradigm entered the scene around
the time that the lawsuit was filed. The feedback loop became
digital. More importantly, multiple POLs could be controlled
and monitored remotely via a digital bus. There were two
approaches to this kind of digital power.
Power-One developed the “Z-bus” concept, which used a
controller chip to communicate with multiple POLs via a proprietary
one-wire bus (see the figure). The controller could
operate autonomously, or it could communicate with the system
via an I2C bus. The company also developed an elegant
GUI for development.
Meanwhile, Artesyn introduced a concept called the Power
Management Bus (PMBus) that applies to POLs as well as to
other voltage converters all the way up to ac-dc supplies.
Artesyn proposed it as an open standard, eventually attracting
40 members. In PMBus, voltage converters share an SMBus
with a controller, and there can be hierarchies of buses.
THE VERDICT
How important are POLs? Big data centers
use more power than a nuclear aircraft carrier, so part of the
fix is to make server operating systems aware of, and interoperable
with, power supplies. Of course, that goes beyond
POLs. But estimates of overall POL business now stand at
around $1 billion annually.
What was in the Power-One patents that the jury upheld?
There are two patents, and the jury found all their claims valid.
One was U.S. Patent 6,936,999 for the Z-Bus Digital Power
Module, the controller. The other was 7,000,125, “Method and
system for controlling and monitoring an array of point-of-load
regulators.” That’s the one Power-One said Artesyn had violated
in the product that Artesyn had “never sold, never offered
for sale and that the market has never used.”
The patent makes 31 claims, but the judge got the parties
to agree that the jury would only rule on several of them: multiple
POLs; one or more bidirectional serial buses for programming,
control, and monitoring the POLs; a user interface;
memory with default settings; more details about programming;
and the exact constituents of such a POL. The jury said
that they’re all valid.
Outside of legal costs, the penalty for Emerson is minor. Outside
of POLs, Power-One has no reason to challenge PMBus.
What does that mean for system and circuit designers? “If
somebody is going to be using digital control of POLs, they
should start by talking to Power-One,” said Power-One executive
vice president Dave Hage.
Power-One
www.power-one.com
Emerson Network Power
www.emersonnetworkpower.com