Design Win

12 V - 400 W adapter based on L4985A, L6699 and SRK2001

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Product overview


The EVL400W-80PL demonstration board is a 12 V - 400 W converter, tailored to the typical specifications of an AC/DC adapter with wide input mains range, very low power consumption at light load and good average efficiency.

It is composed by a motherboard mounting the high voltage power devices, the primary control board mounting the IC controllers L4985A and L6699 and the secondary control board for the synchronous rectification.

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 L4985A, 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 a reduction in the size of the heatsink required.

The PFC section uses the L4985A, a peak current-mode PFC controller for boost converter with a proprietary multiplier “emulator” which, in addition to the innovative THD optimizers, guarantees very low Total Harmonic Distortion (THD) performance in all operating conditions.

The device operates in quasi-fixed frequency in all operating conditions thanks to a proprietary off-time modulator and includes the high voltage startup block with the circuitry to discharge the X-capacitors of the EMI filter.

This level of integration allows a low-component count solution for boost PFC pre-regulators.

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.

  • 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 computer and compliant with 80Plus PLATINUM level
    • Average efficiency: > 89%, according to European CoC ver. 5 Tier 2 for external power supplies
    • Efficiency at 250 mW > 50%, compliant to EuP lot 6 Tier 2 limit for household and office equipment
    • No load mains consumption: < 150 mW at 230 Vac, below European CoC ver. 5 Tier 2 limit for external power supplies
    • Mains harmonics: meets EN-61000-3-2 Class-D and JEITA-MITI Class-D
    • EMI: according to EN55022 Class-B
    • Safety: meets EN60950 standards
    • RoHS compliant

Quality and Reliability

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




Material Declaration**:

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RoHS Compliance Grade


(**) 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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(*) Suggested Resale Price (USD) per defined quantity for BUDGETARY USE ONLY. For quotes, prices in local currency, please contact your local ST Sales Office or our Distributors