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.
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.
Emerson Network Power