Design Win

12 V - 400 W adapter based on L4984, L6699 and SRK2001

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Product overview


The EVL400W-EUPL7 demonstration board is a 12 V - 400 W converter, tailored for the typical specification of an AC/DC adapter with wide input mains range, very low power consumption at light load and good average efficiency.

The architecture is based on a two-stage approach: a front-end PFC pre-regulator based on a CCM (continuous conduction mode) boost PFC controller using the L4984, and a downstream LLC resonant half-bridge converter, designed around the L6699.

At the secondary side, synchronous rectification is implemented by means of the SRK2001 that assures a very high rectification efficiency with consequent small Heat Sink required.

The PFC section uses a proprietary LM-FOT (line-modulated fixed-off-time) that allows control methodology at fixed frequency operation for boost PFC converters as long as its operating in CCM.

The LLC section uses the L6699, a double-ended controller specific to series-resonant half-bridge topology. The output voltage regulation is obtained by modulating the operating frequency.

The main focus of this demonstration board is the light-load efficiency, achieved through the burst mode function of both PFC and LLC controllers with the self-adaptive deadtime of the L6699, modulated by the internal logic according to the half-bridge node transition times, which allows the maximization of the transformer magnetizing inductance, reducing the primary current at light load operation.

An active high voltage start-up circuitry based on a depletion MOSFET provides a very fast start-up time and minimizes the residual consumption during normal operation to a negligible level.

  • All features

    • Universal input mains voltage range: from 90 Vac to 264 Vac
      • frequency from 45 to 65 Hz
    • Output voltage: 12 V at 33 A continuous operation
    • Overall efficiency at full load: > 89%, according to ENERGY STAR® 6.1 limit for computers
    • Certified as 80Plus PLATINUM level at 115 Vac and GOLD level at 230 Vac in the CLEAResult Plug Load Solutions website
    • Average efficiency: > 89%, according to European CoC ver. 5 Tier 2 for external power supplies
    • Efficiency at 250 mW > 50%, well above EuP lot 6 Tier 2 limit for household and office equipment
    • No load mains consumption: < 150 mW at 230 Vac, well below European CoC ver. 5 Tier 2 limit for external power supplies
    • Mains harmonics: meets EN61000-3-2 Class-D and JEITA-MITI Class-D
    • EMI: according to EN55022 Class-B
    • Safety: meets EN60950 standards
    • RoHS compliant

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Quality and Reliability

Part Number Marketing Status Package Grade RoHS Compliance Grade WEEE Compliant Material Declaration**
CARD Industrial Ecopack1 -




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(**) The Material Declaration forms available on st.com may be generic documents based on the most commonly used package within a package family. For this reason, they may not be 100% accurate for a specific device. Please contact our sales support for information on specific devices.

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