LED driver LM3450 for high brightness LED lighting systems

The LM3450 LED driver for high-brightness LED lighting systems has a built-in active power factor correction (PFC) and phase dimming decoder to ensure stable light and dark changes within a very wide programmable dimming range without flickering.

Residential and commercial lighting systems that use phase dimmers must be equipped with circuits that can correctly decode the phase-chopping waveform so that the dimmer can stably adjust the brightness of the LED. Current dimmable LED drivers on the market often do not meet the minimum current requirements of positive phase dimmers or TRIAC dimmers, causing the dimmer to suddenly shut down or "misfire" when adjusting the brightness, causing the light to flicker because the phase angle cannot be accurately interpreted, and the flicker is particularly noticeable at very low dimming rates. To solve this problem, current drivers will reduce the dimming range of the LED or continuously dissipate power to ensure that the dimmer does not misfire.

The new LM3450 LED driver, designed with a unique design, solves this problem and features a built-in hold circuit that allows for flexible adjustment of the current flowing into the phase dimmer. This flexible current hold circuit works in conjunction with a programmable intelligent dimming decoder to ensure stable light and dark variations throughout the entire 100:1 dimming range. Because this chip integrates the above functions, its dimming effect is superior to similar products in the industry, with not only stable light and dark variations, but also the highest efficiency in the industry. The LM3450 LED driver also has a built-in active power factor corrector to ensure that the power factor meets the strict regulations of the U.S. Environmental Protection Agency's Energy Star program for residential and commercial lighting products.

The LM3450 LED driver can accurately adjust the output while significantly improving the power factor at the input. The built-in phase dimming decoder can interpret the phase angle and convert it into a DIM signal suitable for 500 Hz PWM output so that the driver can adjust the brightness of the LED. Because the LM3450 driver has these features, it is an adjustable phase offline LED driver suitable for driving 10W to 100W loads.

The built-in phase dimming decoder increases design flexibility by utilizing programmable mapping functions from input to output. In addition, the decoder also includes a filter that can flexibly perform filtering functions, and the sampling rate can be changed at any time to ensure that the dimmer responds quickly and the light changes steadily. The holding circuit that can flexibly adjust the current ensures that the decoder correctly interprets the dimmer phase angle while minimizing the additional power consumption that must be generated by providing the holding current.

Other benefits of the LM3450 include an analog trim input that engineers can use to provide functions such as thermal foldback, sensor line connections or dimming range adjustment.

The LM3450 chip can be configured in one or two stages. Taking the lighting system using AC as an example, if a one-stage configuration is used, the size of the lighting product can be minimized and the system can give full play to its conversion efficiency. The advantage of the two-stage configuration is that it can improve the dimming effect and enhance the ability to resist noise interference.

Internal Block Diagram

Connection Diagram

Features

■Critical conduction mode PFC

■Overvoltage protection

■Response short circuit protection

■70:1 PWM dimmer decoding

■Analog dimming

■Programmable brightness adjustment range

■Digital angle detection and dimmer

■Dynamic holding current

■ Smooth dimming transition

■Low power operation

■Start-up pre-bias regulator

■Precision voltage reference

Typical Applications

application

■ Dimmable spotlights, troffers and lowbays

■SSL for indoor and outdoor areas

■PFC of power supply