Stmicro's L4985A/B and L4986A/B power factor correction (PFC) boost converters with integrated 800V starting circuits, as well as STMICRO's proprietary practical auxiliary features, help simplify application design and improve design flexibility.
The chip's built-in high-voltage start function saves auxiliary circuits and supports a "no auxiliary circuit" design, reducing bill of material costs and ensuring startup reliability. In the additional auxiliary circuit, the internal logic circuit can perform a safe discharge operation on the input filter X capacitor when the AC line is disconnected, solving the power loss problem of traditional discharge resistors and simplifying the design of compliance with safety regulations such as IEC 61010-1 or IEC 62368-1.
Both converters can be used as PFC preconditioners to help a variety of applications meet harmonic distortion requirements, such as IEC 61000-3-2 and equivalent standards. Target applications include desktop computers, servers, game consoles, TVS and other product equipment power supply; Switching power supplies (SMPS) for industrial and medical equipment; Electric scooter charger. The converter also integrates a proprietary multiplicative simulator and dedicated circuitry to minimize total harmonic distortion (THD) in all operating conditions, ensuring a stable power quality for the LED luminaires.
Stmicro's highly integrated PFC boost converter solves startup circuit design challenges
The new converter benefits from STMICRO's proprietary turn-off time modulator, which ensures that the converter maintains quasi-fixed frequency operation under full load conditions and enters burst mode at light and zero load, thus further simplifying the design. The switching frequency of L4985A and L4986A is 65kHz, while that of L4985B and L4986B is 130kHz. The L4986A/B product adds the normal input and output pins of the power supply, which can generate a logic signal to assist system management when the PFC output reaches the preset threshold of the user.
To enable energy efficient design, all products have an external standby pin to initiate low-power idle mode in accordance with the latest European eco-design directive.
Comprehensive protection and monitoring features are also built into the new product, including overvoltage protection, feedback loop failure protection, setup error protection, and boost inductor saturation protection. The soft-start circuit limits inrush current and helps maintain output voltage stability, while brown-out/brown-in undervoltage detection ensures reliable startup of the converter under all AC line conditions and prevents excessive RMS current. brownout protection enables medical devices to meet IEC 60601-1-2 requirements. The IEC 60601-1-2 standard requires that the power supply must keep the output voltage stable when the grid line voltage decreases within 500ms.
Engineers can accelerate project design cycles with the EVL400W-80PL Evaluation board, a CLEAResult® 80PLUS Platinum Level certified total AC/DC power solution. EVL400W-80PL board integrates L4985 PFC controller with STmicro L6699D resonant controller and SRK2001 synchronous rectifier controller, full load energy efficiency is 90.2%, and reaches 92.49% at 50% load.
The whole series of L4985 and L4986 products have been put into mass production. L4985A/B adopts SO-8 package; The L4986A/B has added power normal pins and is packaged in SSOP-10.