Products, Materials + Tools | Jan 12, 2011

iWatt’s New Digital LED Driver ICs Deliver Flicker-Free Dimming & Hot-Plug Support

iWatt, Inc., a developer of energy-efficient digital power supply control integrated circuits (ICs) used in leading-edge power supplies, today announced two primary-side-regulated, leading- and trailing-edge-dimmable, AC/DC Digital PWM Controllers targeting 100V/230VAC offline LED lighting applications. Designed for isolated or non-isolated LED drivers used in incandescent replacement lamps including both space-constrained (GU10, MR16) and larger (A, PAR) types, the iW3612 (3W to 25W) and low-power iW3602 (3W to 10W) incorporate features to ensure long life, power efficiency, reduced size and component costs, and flicker-free compatibility with existing wall dimmers worldwide. Both LED driver ICs are pin compatible with the previous-generation iW3610, but offer wider dimmer compatibility and introduce new hot-plug support, where the user can swap the LED engine without recycling the input power for the LED driver.

iW36xx Common Features:
• Isolated AC/DC offline 100 Vac / 230 Vac LED driver
• Up to 10 W output power
• Line frequency ranges from 45 Hz to 66 Hz
• Intelligent wall dimmer detection
  o Leading-edge dimmer
  o Trailing-edge dimmer
  o No-dimmer detected
  o Unsupported dimmer
• Hybrid dimming scheme
• Wide dimming range from 1% up to 100%
• No visible flicker
• Resonant control to achieve high efficiency, 85% without dimmer
• Temperature compensated LED current
• mall size design
  o small size input bulk capacitor
  o small size output capacitor
  o smallest transformer
• Primary-side sensing eliminates the need for opto-isolator feedback and simplifies design
• Tight LED current regulation ± 5%
• Fast start-up, typically 10 μA start-up current
• Hot-plug LED module support
• Multiple protection features:
  o LED open circuit protection
  o Single-fault protection
  o Over-current protection
  o LED short circuit protection
  o Current sense resistor short circuit protection
  o Over-temperature protection

Worldwide conservation initiatives to replace existing incandescent bulbs with energy-efficient LEDs force those LEDs to address the installed base of dimmable-lighting switches. In iWatt’s LED driver ICs, intelligent digital algorithms automatically detect all types of dimmers or a lack thereof for seamless operation, including both leading-edge (TRIAC style) and trailing-edge dimmers. In the rare case of an unsupported dimmer, safe mode shuts it down. The devices allow smooth, flicker-free dimming from 1% to 100% with tight +5% LED current regulation which prevents flicker from noisy line voltage.

iWatt’s AC/DC power conversion ICs are unique in that they feature a digital feedback and control loop versus analog. This adaptive digital control technology – which is transparent to designers and requires no programming or GUI development – optimizes efficiency, simplifies printed circuit board (PCB) design, and eliminates components to reduce driver size and bill of materials (BOM). Precision primary-side-control technology eliminates the opto-coupler and secondary-side control circuit used in traditional isolated flyback designs. Built-in frequency jitter and quasi-resonant (or valley-mode) switching reduces EMI with over 6dB margin and over 85% efficiency, improving thermal management and reducing the EMI filter components necessary. Proprietary digital spread spectrum technology also makes for easy EMI design by automatically adjusting the device’s switching frequency in real-time response to varying line voltage.

The high switching frequency up to 200kHz enables designers to use smaller capacitors and transformers to optimize space. Additionally, designers may use a smaller heat sink because the high efficiency (85% or better) reduces thermal loss.

LEDs can operate for more than 50,000 hours, and some manufacturers even say 100,000. However, over time and at elevated operating temperatures, the opto-couplers and low-cost electrolytic capacitors in the driver circuitry become weak links in achieving long life. iWatt’s primary-side-control technology eliminates the opto-coupler, and coupled with low inrush current and low ripple current by design, lengthens the life of the LED driver assembly.

Comprehensive safety features include: LED open/short circuit protection, input over-voltage protection, and over-temperature thermal shutdown. An LED current de-rating at high temperatures also protects LEDs. The ICs enable system designers to exceed all safety, EMI, and regulatory standards, including the EN55015B, IEC61000-3-2, and Energy Star.

The chips come in a low-cost, thermally-enhanced SO-8 package with an exposed pad which allows lower die junction-to-PCB thermal resistance for increased reliability. Samples are available, with the iW3602 priced at $0.84 and the iW3612 at $0.98 in 1,000-piece quantities

About iWatt:
iWatt, Inc. is a power control IC company that designs, develops, and markets semiconductor products for the communication and consumer market segments. The company's patented digital control expertise raises the bar in power supply price/performance metrics. iWatt is currently working with market leaders in the communications, flat panel display, and consumer electronics markets to develop high-density, high-value AC-DC, and DC-DC power supplies. iWatt is backed by VantagePoint Venture Partners and Sigma Partners, two leading CleanTech investors, and Horizon Ventures. The Company’s Silicon Valley headquarters is located in Los Gatos, CA with additional offices in Taipei, Taiwan; Seoul, Korea; Tokyo, Japan; Shenzhen, China; and Hong Kong.

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