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Date: 09-09-15

DC-to-constant current drivers support dimming in smart connected LED lamps

The new LED drivers AL1791/2/3/4 from Diodes Inc., support analog and PWM dimming control in smart, connected white and color LED lamps which are called as smart bulbs.

AL1791/2/3/4 can operate from a 6.5V to 30V input voltage range and can drive up to four independent LED channels with a maximum of 500mA per channel or 1.5A total drive current for the AL1792/3/4, or 1A maximum for the AL1791. Each channel can be individually controlled down to 0.125% with 500Hz to 10kHz flicker-free PWM dimming or with analog dimming down to 1.25%. Using the same pin for both inputs ensures the appropriate analog or PWM dimming response.

Since human eye responses is not linear but is logarithmic, the current control also need to support for such natural response. Diode Inc says these LED drivers support that kind of dimming control with deep dimming down to below 1%. AL1791/2/3/4 operate PWM dimming above 1kHz causing no flicker and the pictures taken by smartphone cameras or any such cameras produce good quality pictures when no bands in the images. The AL179X is capable of high frequency PWM for deep dimming applications: 10kHz at 1.0%, 4kHz at 0.4% and 1kHz at 0.1%.

The safety and other features in AL179x LED drivers includes an enable pin or low standby power, internal protection for LED string open/short-circuit and under voltage lockout, over-temperature protection with thermal shutdown and auto-recovery, and full fault reporting and LED power-good reporting. An integrated low-side current sink topology allows for either lower cost common-anode LED connections or different anode voltages for improved energy-efficiency. All devices operate over an ambient temperature range of -40 Degree C to +125 Degree C and are packaged in the same 14-pin UDFN-4030 package, which allows for easy scalability of LED driver design in smart, connected-lighting applications.

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