The PMBus Implementers Forum released version 1.1 of the PMBus open standard power management protocol at APEC this week, with some enhancements for the management of system power supplies, and some additions aimed at making the standard attractive for AC/DC power supplies – previously the bus focused on DC/DC converter management.

The new version simplifies system management chores with enhanced fan and cooling management features plus improved fault management.

A quick recap of the bus: At the physical level it's based on the industry-standard I²C bus, a simple 2-wire bus originally developed by Philips for intra-chip communications on a single board. The PMBus protocol standardizes communication between the power converters and other power sub-system devices – such as fans – and the host system.

Power management buses faced a rocky reception at their inception a few years ago, when many in the industry thought that most power supplies were so cost sensitive that adding even 50 cents to the power supply BOM would be a prohibitive increase. However, with large installations like server farms becoming energy-aware, the ability to effectively manage power and its attendant cooling subsystems more than pays off the small additional cost of adding intelligence to the power system. PMBus is ramping up at the perfect time.