AN2711 Triac Dimmable LED Driver Application Note

About this manual

The document presents a solution for driving LEDs using Triac phase-control dimmers, which are common in home fixtures but often cause erratic performance in standard power converters. The proposed design utilizes the ST L6562A transition-mode PFC controller to drive a single-stage PFC-flyback converter, ensuring compatibility with dimmer circuits while maintaining high power factor when not dimmed.

The note covers the background of triac-based dimming issues, hardware design details for the STEVAL-ILL016V2 demonstration board, circuit descriptions, and performance analysis under various conditions including undimmed operation, maximum output current, startup times, and conducted EMI.

What's inside

• Characteristics of the Triac-based dimmer
• Damping circuits
• Other input filter effects
• Filtering the LED current - electrolytic capacitors revisited
• Hardware design of the STEVAL-ILL016V2 demonstration board
• Circuit description
• Performance (Undimmed)
• Performance (Dimmed)
• Startup time
• Conducted EMI

Specifications

Frequently asked questions

What is the basis for this LED driver design?

The design is based on the ST L6562A transition-mode PFC controller driving a single stage PFC-flyback power converter.

What are the benefits of using this driver with dimmers?

It provides a low-cost, commonly available dimming option for home fixtures and ensures high power factor when not wired to a dimmer.