iWatt’s New Digital LED Driver ICs in Space-Constrained LED Lighting Application
Jan 13, 2011 iWatt, Inc., a US developer of energy-efficient digital power supply control integrated circuits (ICs), has 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.
iWatt’s AC/DC power conversion ICs 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.
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.
Author: BIO T&T
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