LYT3315D

Description

The LYTSwitch™-3 family is ideal for single-stage power factor corrected constant current LED bulbs and downlighters. Each device incorporates a high-voltage power MOSFET and discontinuous mode, variable frequency variable on-time controller. The controller also provides cycle-by-cycle current limit, output OVP, line overvoltage, comprehensive protection features, plus advanced thermal management circuitry.

All LYTSwitch-3 ICs have a built-in TRIAC detector that discriminates between leading-edge and trailing-edge dimmers. This capability together with load monitoring circuitry regulates bleeder current during each switching cycle. The controller disables the bleeder circuit completely if no dimmer is detected, significantly increasing efficiency.

The combination of a low-side switching topology, cooling via electronically quiet SOURCE pins and frequency jitter ensure extremely low EMI. This reduces the size of the input filter components – greatly reducing audible noise during dimming.

The part numbers shown in Table 1 describe 4 different power levels and two MOSFET voltage options to cost-optimize designs while EcoSmart™ switching technology insures maximum efficiency for each device size and load condition.

Product Highlights

Combined Single-Stage PFC + Accurate CC Output

• Less than ±3% CC regulation over line and load
• Power Factor >0.9
• Ensures monotonic VA reduction with TRIAC phase angle
• Low THD, 15% typical for dimmable bulbs, as low as 7% in optimized designs

Advanced Integrated TRIAC Dimmer Detection

• Detects leading-edge and trailing-edge TRIAC dimmers
• High-efficiency mode when no dimmer is present
• Selectable dimming profile increases design flexibility
• Fast turn-on (<500 ms) even in deep dimming
• Low pop-on and dead-travel
• Active bleeder drive for widest dimmer compatibility

Design Flexibility

• Supports buck, buck-boost, tapped-buck, boost, isolated and non-isolated flyback
• Up to 20 W output

Highest Reliability

• No electrolytic bulk capacitors or optoisolators for increased lifetime
• Comprehensive protection features
  • Input and output overvoltage
  • Output short-circuit and open-loop protection
• Advanced thermal control
  • Thermal foldback ensures that light continues to be delivered at elevated temperatures
  • End-stop shutdown provides protection during fault conditions