Power Electronics

Are the Power Module Alliances Really Different?

During APEC 2005, attendees had a spirited debate on whether standardization and/or alliances benefited the power industry and its customers. The most intense discussion centered on which was better, the Distributed-power Open Standards Alliance (DOSA) or the Point of Load Alliance, known as POLA. It was clear from some of the comments that there were misperceptions about both initiatives.

As background, POLA includes Texas Instruments, Artesyn Technologies, Emerson's Astec Power, Ericsson Power Modules and now Murata Manufacturing. DOSA includes Artesyn Technologies, Celestica Power Systems, Delta Electronics, Ericsson Power Modules, Lambda, SynQor and Tyco Electronics. Both alliances have a common goal: to provide customers standardization and second-sourced products. However, as with most differing schools of thought, the way to achieve this objective can vary significantly.

The most important difference between the two alliances is the circuits used in their products. POLA is founded on the fundamental that every POLA member — three are required to call a part POLA — builds a product to the same schematic. The founding principles of POLA are to give the customer the same mechanics, footprint and functionality, plus provide modules that are completely interoperable; for example, they will function the same in all static and dynamic operating conditions. These principles support customers' continual requests for power modules that work the same in their circuit design, regardless of the supplier.

DOSA chose to take a different approach to standardization and second sourcing. It created standards that define the mechanics and pin-out, plus the pin functions. The members who choose to implement the standard — only two are required to call a part DOSA — design the circuits independently without sharing intellectual property. DOSA members cannot and do not claim complete interoperability for their parts.

The DOSA camp claims to offer the only “true second source” modules, based on the argument that all POLA modules have the same pulse width modulator (PWM) IC. Wouldn't that put a weak link in the supply chain? POLA nonisolated modules are based on PWMs from a single supplier. POLA and its PWM supplier, which is independent of the alliance members, have undertaken significant steps to ensure an adequate source of supply and virtually eliminate this risk. In addition to fabrication, stocking wafers and finished parts, the PWM supplier produces the POLA PWMs at two independent foundries, which provides three POLA silicon fabrication sites. All other parts on the POLA schematics are available from at least three suppliers.

Perhaps the challenge of “true second source” needs to be redirected to DOSA. If DOSA modules are completely independently executed designs, how can they be a “true second source” if they are not interoperable? Because the designs are different, the customer is forced to qualify all modules independently in every design. With POLA, only a module from one company needs to be tested. All the others will work the same.

To ensure maximum integrity of the design, each POLA part undergoes a rigorous internal testing and qualification process by each partner, including life test, humidity, thermal shock, HALTS, EMC, plus mechanical shock and vibration testing. Most of the modules are made and tested by all five POLA companies. As a final test, POLA companies send samples of each new part adopted to the company that originated the design for interoperability testing.

In addition, POLA takes mechanical compatibility to a higher level. Not only are the dimensions, pin-out and pin functions the same, but the mechanical placement of major components is the same. For pick-and-place assembly, the pick-up point — usually the inductor — is in the same place for every partner.

POLA also recently agreed to match tape-and-reel formats. Contract manufacturers can buy POLA parts from any member and be assured of no downtime to re-setup or reprogram pick-place equipment.

The power module alliances really are different. Customers and time will determine who really is the “true second source.”

Brian C. Narveson is the strategic marketing manager for Texas Instruments' Plug-In Power business. Prior to the acquisition by TI, Narveson served as vice president of Engineering for Power Trends Inc. since 1992.

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