Innovative iWatt SSL LED Driver Addresses Cost and Lifetime Issues in Price-Sensitive Retrofit Bulbs

The iW3626 was developed in close cooperation with several iWatt key customers, including Eastfield International Industries, Ltd., which has designed the iW3626 into its next-generation, non-dimmable SSL bulb product lines.

“The challenge with SSL bulbs is hitting the price point the market demands with the long-term reliability consumers expect,” said Mr. Jacky Luo, director of R&D Centre at Eastfield International Industries. “We chose iWatt’s iW3626 because it enables us to optimize our designs to the specific needs of our customers and because of the built-in OTP derating. These features enable us to ensure predictable, long operating life with a low BOM cost.”

Regulations around the world mandate performance requirements, such as PFC and input harmonics and these regulations vary by country and by application. In single-stage LED drivers, there is a correlation between improving PF and increasing output ripple. The patent-pending, user-configurable PFC feature in the iW3626 allows designers to configure the PF strength from > 0.7 to > 0.9, enabling them to meet the various global mandates, while effectively managing the trade-off between power factor and output ripple. This helps ensure the required power factor can be achieved with low output ripple, minimizing both heat and flicker, with no impact to overall cost or size.

The on-chip, configurable over-temperature protection and derating feature of the iW3626 monitors the temperature inside the sealed SSL bulb. When thermal conditions reach a point set by the system designer, the iW3626 LED driver automatically reduces the current drive to the LEDs, lowering the power dissipation and resulting in cooler overall operation. This reduces the risk of thermal runaway and ensures the temperature rating of the electrolytic capacitors in the system is not exceeded, thereby helping ensure predictable bulb operating life. Additional built-in protection features include LED open/short, input over-voltage, over-current, and current-sense resistor short protections.

The iW3626 achieves up to 20% BOM cost savings via its highly integrated design features. It allows FETs to be replaced with lower-cost, bipolar junction transistors (BJTs), eliminating the need for high-voltage electrolytic capacitors, and includes the configurable over-temperature protection feature on board. Additionally, iWatt’s patented PrimAccurate™ primary-side control eliminates the need for a secondary-side regulator and optical feedback isolator.

The iW3626 is packaged in a standard, low-cost, 6-lead SOT23 package, which can be used in single-layer PC boards for additional cost savings and a smaller design footprint.

“The biggest obstacles to mass consumer adoption of SSL LED bulbs have been cost and predictable operating life,” said Hubie Notohamiprodjo, iWatt’s director of marketing for SSL products. “The iW3626 LED driver offers a new approach to reduce these barriers in non-dimmable applications, with features such as configurable power factor correction and integrated over-temperature protection, which, until now, were only associated with higher-cost driver solutions.”

iW3626 Key Features
Output power: 10W (for 60W equivalent bulbs)
User-configurable power factor from > 0.7 to > 0.9
PrimAccurate primary-side control reduces solution size, lowers BOM cost, increases reliability
Up to 20% BOM savings(1)
High efficiency > 85% at high line
Tight LED current regulation better than ± 5%
LED over-temperature protection and derating
Meets global standards, including European Union IEC61000-3-2(2) requirements
Small SOT-23 package

Pricing, Availability
The iW3626 is available now in production quantities. Samples are available at $0.35 in 1000-piece quantities.