STMicroelectronics has launched a 400W power supply evaluation board to help equipment makers meet stringent enviornmental energy efficiency requirements.
The EVL400W-EUPL7 evaluation board is a ready-to-use 400W power supply built with ST’s L4984D current-mode PFC controller and L6699 resonant half-bridge controller to maximize energy efficiency in multiple operating modes.
Full-load efficiency is over 93 percent at 230VAC and over 91 percent at 110VAC, with no-load mains consumption of less than 0.150W. This meets the US EnergyStar v6.1 requirements for a power supply for a computer system, as well as the European EuP Lot 6 Tier 2 requirements for household and office equipment, and the CoC (Code of Conduct) Version 5 Tier 2 for external power supplies.
The EVL400W-EUPL7 has also achieved CLEAResult Plug Load Solutions 80 PLUS certification, rated Platinum at 115V AC and Gold at 230V AC. CLEAResult is the largest provider of energy efficiency programmes and services in North America and the 80 PLUS performance specification is referenced by EnergyStar. This requires a multi-output power supply in computers and servers to have an efficiency of 80 percent or greater at 20 percent, 50 percent and 100 percent of rated load with a true power factor of 0.9 or greater.
The high efficiency at light loads comes from the support for burst mode in the L4984D and L6699, as well as the L6699’s self-adaptive dead-time that allows for reduced primary current. The L4984D and L6699 each have low quiescent current and a disable input that allows remote on/off control and can be used for power sequencing or brownout protection. The two devices can also interact to switch-off the pre-regulator when operating in burst mode.
The power supply design also uses ST’s SRK2001 synchronous-rectification controller to provide high average and typical efficiency across a wide load range. Saving energy with synchronous rectification also allows a small heatsink at the secondary side.