STMicroelectronics L6562A | Demoboard STEVAL-ILL027V2

Description

With the rapid development of high brightness LEDs, SSL (solid state lighting) has begun tomove from being a niche market to penetrating residential markets. There is a largepotential market for the residential application of SSL, and CFL (compact fluorescent lamp)retro-fit is part of it. Standardization of SSL products is helping to lead the growth of themarket. In September 2007, the US department of energy (DOE) issued ENERGY STAR®criteria for SSL products. To meet the ENERGY STAR specifications for SSL products, thepower factor of power supply must be higher than 0.7 for residential applications. For CFLretro-fit applications, cost, size, and reliability are very important. To achieve a high powerfactor, either passive PFC (power factor correction) or active PFC can be used. Typically,passive PFC requires large passive components, which makes it difficult to maintain a smallsize. Traditional active PFC circuits require a two-stage topology, which entails a boost stagefor PFC, and then buck or flyback for current regulation of the LEDs. The cost of the twostages is high. In this application note, a non-isolated, soft-switched, single-stage highpower factor offline LED driver is introduced. The buck-boost converter is chosen for thisapplication due to its simplicity and low cost. The converter operates with constant peakcurrent for constant power control, and in transition mode (boundary mode between CCMand DCM) to achieve soft switching, using the L6562A controller. High power factor isachieved by reshaping the peak current near the zero crossing of the input AC line.

Features

• Proprietary multiplier design for minimum THD
• Very accurate adjustable output overvoltage
• protection
• Ultra-low (30μA) Start-up current
• Low (2.5mA) quiescent current
• Digital leading-edge blanking on current sense
• Disable function on E/A input
• 1% (@ TJ = 25 °C) internal reference voltage
• -600/+800mA totem pole gate driver with active
• pull-down during UVLO and voltage clamp
• DIP-8/SO-8 packages

Typical applications

• IEC61000-3-2 compliant SMPS (Flat TV, monitors, desktop PC, games)
• HI-END AC-DC adapter/charger up to 400W
• Electronic ballast
• Entry level server & web server

More information

• Datasheet
• IC product information