National Semiconductor LM3450 LED driver

National Semiconductor has introduced an LED driver with what is claimed to be the best phase-based dimming performance for high-brightness light-emitting diode applications.

The LM3450 LED driver integrates active power factor correction and phase dimming decoding to provide uniform, flicker-free illumination across a wide, programmable dimming range.

A member of National’s PowerWise energy-efficient product family, the LM3450 is suitable for use in high-performance, phase-dimmable, 10 to 100 W LED fixtures.

The driver regulates an accurate output while maintaining power factor at the input. The integrated phase dimming decoder interprets the phase angle and remaps it to a 500 Hz PWM output to dim the LEDs. This combination of features is suitable for implementing a phase-dimmable offline LED driver for 10 to 100 W loads.

The phase-dimming decoder uses programmable mapping from input to output to increase design flexibility. It also features a dynamic filter and variable sampling rate for a fast, smooth response to dimmer movement. An integrated dynamic hold circuit ensures that the phase dimmer angle is decoded properly while minimising the extra power losses associated with holding current.

Other benefits include an analog adjust input to allow for differentiation such as thermal foldback, interface to sensors or dimmer range adjustability.

The device can be implemented in either single- or two-stage configurations. The single-stage configuration yields the smallest footprint and allows for the highest efficiency when converting from the AC mains voltage.