iWatt’s digital LED driver ICs deliver flicker-free dimming and hot-plug support in space-constrained LED lighting apps

LOS GATOS, USA: iWatt, Inc., a developer of energy-efficient digital power supply control integrated circuits (ICs) used in leading-edge power supplies, 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.

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 percent to 100 percent with tight ±5 percent 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.