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Chips improve efficiency for notebook, desktop power supplies

Digitally controlled power supplies— those in which the control loop closes digitally—have so far found favor primarily in applications requiring large amounts of power. For example, ColdWatt’s (www.coldwatt.com) 1200 to 1625W ac/dc power supply uses Silicon Labs’ (www.silabs.com) C8051F30x digital- power-control chip and targets server installations. Now, Marvell is introducing two digital-control chips that target smaller ac/dc power supplies for notebook and desktop computers. The 8041 aims at notebook computers and supplies as much as 80W, and the 8011 targets desktop computers and supplies as much as 300W. The chips also introduce digital PFC (power-factor correction) for these smaller supplies. Currently, EnergyStar (www.energystar.gov) standards don’t require PFC for laptop and desktop supplies, but future EnergyStar revisions will include PFC requirements because of PFC’s ability to increase power effi ciency.

The chips use Marvell’s proprietary DSP to optimize power throughout the cycle by changing from pulse-width modulation to pulse-frequency modulation in order to keep the peak current at the lowest level. This architecture can also intelligently adjust the current-threshold limit for constant power to manage differences in worldwide universal voltages, which can range from 90 to 260V. Marvell claims that the chips can reduce power-supply size by one-third, reduce BOM (bill-of-materials) count by as many as 20 parts, and increase power-supply effi ciency to 85%. The chips will sell for less than $2 each (1000).

Marvell, www.marvell.com