Led driver, on 24VAC

Electromechanical Optoelectronics
1

https://www.digikey.com/en/products/detail/diodes-incorporated/AL5809-30P1-7/5030208

Will this current limiting LED driver work with 24AC?

If not, what if I add a bridge rectifier circuit? I wouldn’t have enough room for any large caps to smooth it out.

I’m wanting to drive a couple of these LED’s and my supply is 24VAC. Is there better options?

https://www.digikey.com/en/products/detail/cree-led/CLA1A-WKW-CXAYB153/2034472

2

Unfortunately this driver doesn’t take an AC input voltage, it seems. The only AC/DC LED driver I could find that would take 24VAC was part number 788-1043-ND, which doesn’t seem to fit the rest of your criteria. You may need to consider a bridge rectifier or a board mount AC/DC converter with the output going to an LED driver.

3

Would a rectifier, like 4 diodes, would give me a square wave output of 12vdc, right. Would that little chip led driver work on that kind of voltage?

4

I’m only looking at drawing about 100ma

5

Hello @SouthernAtHeart,

Allow me to collect a few notes and then I will provide a few recommendations.

Undervoltage

There is a 2.5 VDC overhead associated with the AL5809-30P1-7.

As an example, consider a red LED with a 2 VDC forward drop. The source voltage should be at least 4.5 VDC.

Overvoltage

The AL5809-30P1-7 has a max voltage of 60 VDC. Your 24 VAC supply has, the peak rectified voltage of 34 V which is well within theAL5809’s specification.

PWM Dimming

The datasheet states that PWM dimming may be used. The frequency range is 100 to 200 Hz.

The impact of pulsed AC (e.g. 120 Hz from a bridge rectifier) is unknown.

Recommendation

  • Bridge rectify the 24 VAC and then add a small filter capacitor. The output of the bridge will be approximately 34 V peak well within the AL5809’s voltage capabilities.

  • However, the AL5809 is a linear regulator. Guard against excessive power dissipation, especially if only a few series LEDs are used.

    Given the high voltage, it may be necessary to add a series resistor to drop the voltage. Stated another way, dissipate some power in the resistor as opposed to all power in the regulator.

  • The AL5809-30P1-7 is rated for 30 mA. For 100 mA shift to the AL5809-100P1-7.

Happy soldering,

APDahlen