ST's L4985A/B and L4986A/B power factor correction (PFC) boost converters integrate 800V start-up circuitry and ST's proprietary and useful auxiliary functions to help simplify application design and increase design flexibility.
The chip's built-in high-voltage start-up function saves auxiliary circuitry and supports "no auxiliary circuitry" designs, reducing bill of materials costs and ensuring start-up reliability. In the additional auxiliary circuit, internal logic circuitry can safely discharge the input filter X capacitor when the AC line is disconnected, solving the power loss problems of conventional discharge resistors and simplifying compliance design with safety regulations such as IEC 61010-1 or IEC 62368-1.
Both converters can be used as PFC pre-regulators to help various applications comply with harmonic distortion requirements such as IEC 61000-3-2 and equivalent standards. Target applications include power supplies for product equipment such as desktop computers, servers, game consoles and TVs; switching mode power supplies (SMPS) for industrial and medical equipment; and electric scooter chargers. The converters also integrate a proprietary multiplication emulator and dedicated circuitry to minimise total harmonic distortion (THD) in all operating conditions, ensuring consistent power quality in LED luminaire power supplies.
ST's highly integrated PFC boost converter solves start-up circuit design challenges
The L4985A and L4986A have a switching frequency of 65kHz, while the L4985B and L4986B are 130kHz. The L4986A/B products have additional power supply normal input and output pins to generate a logic signal to aid system management when the PFC output reaches a user preset threshold.
For energy efficient design, all products have an external standby pin to initiate a low power idle mode in accordance with the latest European eco-design directives.
The new products also have comprehensive built-in protection and monitoring features, including overvoltage protection, feedback loop failure protection, setup error protection and boost inductor saturation protection. Soft-start circuitry limits inrush current and helps maintain output voltage stability, while brown-out/brown-in undervoltage detection ensures that the converter starts reliably under all AC line conditions and prevents excessive RMS currents. brownout protection allows medical devices to meet IEC 60601-1-2 requirements. The IEC 60601-1-2 standard requires that the power supply must maintain a stable output voltage when the grid line voltage drops within 500ms.
Engineers can speed up the project design cycle with the EVL400W-80PL evaluation board, a total solution for AC/DC power supplies certified to the CLEAResult® 80PLUS Platinum Level. SRK2001 synchronous rectifier controller for 90.2% efficiency at full load and 92.49% at 50% load.
The L4985A/B is available in SO-8 package and the L4986A/B has additional power supply normal pins and is available in SSOP-10 package.
