EVL400W-80PL Demonstration Board

STMicroelectronics' 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 preregulators. 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.

Features

• Universal input mains voltage range: from 90 V_AC to 264 V_AC frequency from 45 Hz 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 V_AC, 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