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Friday, October 14, 2011

TI and Maxim target retrofit lamps with LED drivers

Texas Instruments has launched the LM3448 targeting 2-8W lamps and the TPS92070 targeting 6-20W lamps, while Maxim has introduced an SSL driver for global usage.

Texas Instruments (TI) utilized the stage afforded by Strategies in Light Europe to launch two dimmable LED driver ICs – the TPS92070 flyback controller and the LM3448 developed by National Semiconductor before the recent acquisition by TI.

Separately, Maxim Integrated Products introduced the MAX16841 driver for global solid-state-lighting (SSL) applications with support for AC input ranging from 90-265V and dimmers that are prevalent in the US, Japan, China, and Europe.
                                                                                                                                                                 New driver ICs from TI

TI's new driver ICs are both targeted at AC-powered lighting applications such as retrofit lamps with support for phase-cut triac-based dimmers. The TPS92070 driver IC targets 6W to 20W applications and can also be used in SSL luminaires such as downlights and wall washers. The IC includes power-factor correction (PFC) providing a power factor greater than 0.8 based on a valley-fill circuit. The IC will automatically disable the PFC circuit if it detects a dimmer ensuring optimized dimming response.

The LM3448 utilizes a step-down buck regulator to provide constant output current to LEDs. The IC is specifically designed for space-constrained and cost-sensitive applications such as integral lamps that require minimal external components. The design can handle 2W to 8W applications with full-range dimming and can be combined with external PFC circuits.

Both of the new products include protection features such as thermal shutdown, under-voltage lockout, current limiting, and protection for LED open circuits. Both also integrate the MOSFETs needed to output the pulse-width modulation (PWM) signal that sets the dimming level for LEDs. The products mark the first announcement in the LED lighting space since TI completed the acquisition of National Semiconductor, establishing clear market leadership in LED driver ICs.

Both of the new TI drivers are available now and both come in 16-pin packages. The LM3448 sells for $1.10 and the TPS92070 sells for $0.75 – both in 1000-unit quantities. And both can be used in 110V or 220V lamp designs.

Maxim retrofit lamp driver

Maxim's latest LED driver IC also targets retrofit lamp applications driven from the AC power line. The company says that the MAX16841 driver supports flicker-free dimming from zero to maximum output with leading-edge triac and trailing-edge transistor dimmers – including dimmers sold internationally for 220V operation.

The MAX16841 design can be used in an isolated flyback topology that would be typical in universal lamps for 220V operation or nonisolated buck configurations that might be used in 110V applications.

The new driver can also work in lamp designs that eliminate the electrolytic capacitor. That capacitor is a likely failure point and also increases the size of the driver. Lamp makers may find that eliminating it reduces cost and increases reliability, although some such designs have suffered from flicker in the past. Maxim says it has solved the performance issues in designs that eliminate the capacitor.

The MAX16841 can operate over a temperature range of -40 to +125° C. The compact 8-pin device starts at $1.35 in 1000 unit volumes.

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