National Semiconductor has announced a new LED driver with better phase dimming performance than similar products on the market. This LM3450 LED driver for high-brightness LED lighting systems includes an active power factor modifier (PFC) and phase dimming decoder to ensure stable light and dark variations over a wide programmable dimming range. A flashing situation will occur. As a member of National's PowerWise high energy efficiency chip family, the LM3450 is especially suited for 10W to 100W high performance LED lighting systems with phase dimming.
Residential and commercial lighting systems that use phase dimmers must be equipped with circuitry that correctly decodes the phase chopping waveform so that the dimmer can stably regulate the brightness of the LED. Currently, dimmable LED drivers on the market often do not meet the minimum current requirements of a normal phase dimmer or a TRIAC dimmer, causing the dimmer to suddenly turn off or "misfire" when the brightness is adjusted, so that the light Flicker occurs because the phase angle cannot be accurately interpreted, and the flicker is particularly noticeable when the dimming rate is extremely low. In order to solve this problem, the current driver will reduce the dimming range of the LED or continuously dissipate the power to ensure that the dimmer will not start incorrectly.
National Semiconductor has introduced a new, uniquely designed LM3450 LED driver to solve this problem. It features a built-in hold circuit that allows for flexible adjustment of the current flowing into the phase dimmer. This flexible current-adjustable hold circuit works in tandem with a programmable intelligent dimming decoder to ensure stable light and dark variations over the entire 100:1 dimming range. Because this chip integrates the above functions, its dimming effect is better than similar products in the industry, not only the light and dark changes, but also the highest efficiency in the industry. The LM3450 LED driver also incorporates an active power factor corrector to ensure that the power factor meets the stringent requirements of the US Environmental Protection Agency's Energy Star program for residential and commercial lighting product power standards.
This LED driver has a built-in power factor corrector and phase dimming decoder to ensure that the light and dark changes are stable and there is no flicker.
National Semiconductor LM3450 LED Driver Technical Features
The LM3450 LED driver can accurately adjust the output while greatly increasing the power factor at the input. The built-in phase dimming decoder interprets the phase angle and converts it to a DIM signal for the 500 Hz PWM output so that the driver can regulate the brightness of the LED. Thanks to these features, the LM3450 driver is an adjustable phase offline LED driver for driving loads from 10W to 100W.
The built-in phase dimming decoder increases design flexibility by utilizing a programmable mapping function from input to output. In addition, the decoder also includes a filter that can flexibly perform the filtering function, and the sampling rate can be changed at any time to ensure that the dimmer responds quickly and the light and dark changes of the light are stable. The current-adjustable holding circuit ensures that the decoder correctly interprets the dimmer phase angle while minimizing the extra power that is inevitable due to the supply of holding current.
The LM3450 chip has other advantages, including analog adjustment input. Engineers can use this feature to provide different functions such as Thermal Foldback, sensor line contact, 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 the first-level configuration is adopted, the volume of the lighting product can be minimized, and the system can fully exert its conversion efficiency. The two-stage configuration has the advantage of improving dimming and enhancing noise immunity.
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