Integrated flyback controller boosts LED lighting, says ST

The HVLED101 90 to 400V flyback controller for LED-lighting applications up to 180W enhances performance and simplifies design with patented control techniques, and primary-sensing regulation support.

It joins 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. It also integrates high voltage input sensing circuitry and a maximum power control (MPC) engine to ensure consistent power output as the line voltage fluctuates. As a result, designers can choose smaller and lower-cost external passive components to handle worst-case line conditions, said ST. Primary-sensing regulation without isolated feedback are claimed to reduce the bill of materials and enhance reliability.

Patented innovations include ST’s input-current shaping algorithm which lowers total harmonic distortion (THD) and maximises the power factor. The HVLED101 is also claimed to be the first high power factor flyback controller to implement ST’s valley locking technique to minimise audible noise, improve regulation and reduce distortion. At 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. Current shaping and valley locking enhance the power factor and THD even at low and medium loads, confirmed ST. Flyback converters controlled with the HVLED101 can achieve five per cent THD at full load and 10 per cent at 1/3 load to meet leading ecodesign codes.

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). The HVLED101 enables converters to achieve maximum efficiency above 90 per cent and no-load power below 100mW.

The flyback controller has built in over-current protection, input overvoltage protection and brownout protection. There is also a smart auto-reload timer (ART) that allows 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 jumpstart development for faster time to market. The EVLHV101PSR50W is an 90 to 265V AC, 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.

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