New Industry Products

TRIAC Dimmable LED Driver ICs Cut BOM Count by 40

September 02, 2016 by Power Integrations

This article introduces Power Integrations' LYTSwitch-7, a single-stage, non-isolated, TRIAC dimmable, buck topology LED driver IC.

Power Integrations, a leading innovator in semiconductor technologies for high-voltage power conversion and leader in high-efficiency, high-reliability LED driver ICs, announced its LYTSwitch-7 single-stage, non-isolated, TRIAC-dimmable, buck topology LED driver IC family end of July. These LED driver ICs provide a highly robust solution while requiring a BOM count that is approximately 40% less than for conventional circuits.


Capable of delivering up to 22 watts

Capable of delivering up to 22 watts without a heatsink in a very small SO-8 footprint, these high-efficiency devices are suitable for bulbs, tubes and fixtures. LYTSwitch-7 designs do not require bleeders; employing simple, passive damping for TRIAC management and an off-the-shelf, single-winding inductor, reducing component count to just 20, as compared to approximately 35 parts for typical dimmable LED driver boards. The internal 725 V MOSFET delivers better withstand performance during line surges, while the bleeder-less design has high TRIAC compatibility but does not produce wasted heat, resulting in a more efficient and reliable driver.


LYTSwitch-7 ICs deliver a phase-cut (TRIAC)

LYTSwitch-7 ICs deliver a phase-cut (TRIAC) dimming solution with a wide dimming range and monotonic dimming response in the 10:1 range. It is characterized by its advanced thermal performance – the lamp provides light output in abnormal ambient conditions with the wide hysteresis following shutdown. The LED drivers enable efficiency of greater than 86% - around 2% higher than conventional dimmable products – with high PF, accurate regulation and comprehensive protection. They suit low- or high-line input as well as wide-range universal-input designs for U.S. commercial lighting applications, which operate from 90 VAC to 305 VAC with TRIAC dimming enabled in low-line installations.



LYTSwitch-7 is a constant-current device – power delivery is dependent on load voltage.

The family consists of two parts: LYT7503D and LYT7504D, both housed in a SO-8 “D” package, MSL-1 rated. It features a very low EMI with a quiet (source potential) heatsinking, boundary-mode and low-side architecture (with a high-side architecture coming soon), a wide input range with excellent line regulation, and an accurate OVP reduces stress on O/P capacitor. As it is self-biased, low-cost off-the-shelf magnetics can be used. The low VF current measurement increases efficiency. Comprehensive protection includes over-temperature fold-back, end-stop thermal shutdown, O/P over-current short circuit, line OVP, output OVP and open/short IC pins.

A sophisticated proprietary algorithm provides a high power factor (PF) with accurate regulation and best protection:

  • Accurate CC across line, load and production
  • Simple geometric control maintains CC
  • Line-noise rejection in current-limit mode
  • High MOSFET utilization factor - best use of integrated MOSFET
  • Small buck power inductor: single winding allows the use of off-the-shelf parts
  • Small EMI inductor (low EMI): boundary mode, quiet source pin cooling, low-side.

Like all Power Integrations LED drivers, LYTSwitch-7 ICs have a host of protection features including thermal foldback with end-stop shutdown, which protects the IC, driver and fixture at abnormally-high ambient temperatures by automatically reducing the current flow and dimming the lamp. Developers find that thermal foldback is the key to reducing costs associated with over-design of both electrical and mechanical components to meet reliability goals since the IC automatically limits unusual temperature excursions without extinguishing the lamp. Devices are also protected from open- and short-circuit conditions, input and output OV, overcurrent and SOA. LYTSwitch-7 ICs meet international standards including DOE Level 6 (external power supply), CEC Titles 20 and 24, ENERGY STAR® Lamps Program Requirements Version 2.0, NEMA SSL-7A and EN61000-3-2 (C&D).

Key applications include low-cost A19 lamps, small-form-factor lamps such as candle-style and GU10 bulbs, commercial & industrial applications, ceiling lamps and downlight fixtures. LYTSwitch-7 IC samples are available now. Devices are priced at $0.33 in 10,000-piece quantities. Two reference designs (DER-539 and DER-540) are available for download now from the Power Integrations website at LYTSwitch-7.



The newly introduced LED drivers LYTSwitch-7 ICs combine the following features:
• Excellent performance
• Better than 0.9 power factor
• 86% efficiency at 230 VAC
• Deep and monotonic dimming response
• Supporting universal input with 120 VAC dimming for U.S. market
• Regulation better than ±3% across a wide range of line and load
• Simplified BOM
• Lowest total component count (20 components)
• Dimmable without a bleeder
• Single-sided PCB
• Off-the-shelf magnetics
• Up to 22 W with a thermally efficient SO-8 package
• Highly flexible and reliable
• High-side/low-side buck conversion
• Surge resistant with line OV protection
• Integrated accurate input and output OVP, SC, OC, over-current, pin short/open
• Thermal foldback with end stop shutdown
• TRIAC dimmable up to 22 W
• Compatible with standard TRIAC dimmers
• Linear and monotonic dimming
• 90 VAC to 305 VAC input, dimmable at low line
• Highly cost-effective
• Bleeder-less solution
• Standard off-the-shelf magnetics (no bias winding)
• Only 20 total components, small SO-8 package
• 725 V integrated MOSFET enhances surge reliability
• Integrated protection features
• Line overvoltage - surge protection for LED load
• Overcurrent and short-circuit
• Thermal fold-back with end-stop thermal shutdown. 


This article originally appeared in the Bodo’s Power Systems magazine.


About Power Integrations

Power Integrations, Inc. is a leading innovator in semiconductor technologies for high-voltage power conversion. The company’s products are key building blocks in the clean-power ecosystem, enabling the generation of renewable energy as well as the efficient transmission and consumption of power in applications ranging from milliwatts to megawatts.