Flyback controller with advanced features boosts LED lighting performance

Joining ST’s HVLED family of high-power-factor controllers, the HVLED101 contains 800V startup circuitry that cuts the LED turn-on time to less than 250ms. High-voltage input-sensing circuitry and a maximum power control (MPC) engine are also integrated to ensure consistent power output as the line voltage fluctuates. This lets designers choose smaller and lower-cost external passive components to handle worst-case line conditions. Primary-sensing regulation without isolated feedback further reduces the bill of materials and enhances reliability.

Among the patented innovations, ST’s input-current shaping algorithm lowers total harmonic distortion (THD) and maximises the power factor. Also, the HVLED101 is the first high-power factor flyback controller to implement ST’s new valley-locking technique to minimise audible noise, improve regulation, and reduce distortion. At a steady state in quasi-resonant operation, valley locking fixes the number of valleys skipped until a significant change in output power or input voltage is detected. Together, current shaping and valley locking enhance the power factor and THD even at low and medium loads. Flyback converters controlled with the HVLED101 can achieve 5% THD at full load and 10% at 1/3 load to meet leading eco-design codes.

In addition, designers can program the delay time after zero-crossing detection in pure quasi-resonant operation using an external resistor. By ensuring gate turn-on at the lowest point of the valley, the HVLED101 minimises energy losses and electromagnetic emissions (EMI). Overall, the HVLED101 enables converters to achieve maximum efficiency above 90% and no-load power below 100mW.

All necessary protection is built-in, including overcurrent protection, input overvoltage protection, and brownout protection. There is also a smart auto-reload timer (ART) that allows for latch-free operation of all protection mechanisms to ensure high reliability and a superior consumer experience.

Two demonstration boards containing the HVLED101 are available to jump-start development for faster time to market. The EVLHV101PSR50W is an 90-265VAC, 60V/0.8A isolated flyback converter with primary-sensing regulation, while the EVLHV101SSR50W is a similar design with secondary-sensing regulation.

The HVLED101 is in production now in the narrow form-factor SO-14N package priced from $0.99 for orders of 1,000 pieces.