Evaluation board aids energy-saving power supply design

The board leverages innovative features of ST’s L4984D current-mode PFC controller and L6699 resonant half-bridge controller to maximise energy efficiency in multiple operating modes.

Full-load efficiency is over 93% at 230VAC and over 91% at 110VAC, with no-load mains consumption of less than 0.150W, meeting ENERGY STAR Version 6.1 requirements for computers, European EuP Lot 6 Tier 2 requirements for household and office equipment, and 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.

High efficiency at light loads leverages support for burst mode, featured 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.

With ST’s SRK2001 synchronous-rectification controller also on-board, the EVL400W-EUPL7 achieves high average and typical efficiency across a wide load range.

Saving energy with synchronous rectification also allows a small heatsink at the secondary side.

Built-in active high-voltage startup circuitry, designed with a depletion MOSFET, reduces the residual consumption in normal operation to a negligible level and ensures a fast startup time.

Having a 12V output and wide AC input-voltage range from 90V to 264V (45-65Hz), the EVL400W-EUPL7 provides a medium-power reference design ready to meet the most aggressive energy-saving targets for applications such as ATX supplies, small servers and workstations, medical equipment, signage, and LED panels.

With its low no-load consumption, which eliminates the need for an auxiliary switched-mode power supply (SMPS), the design also helps save bill-of-materials (BoM) costs.