I have build a LED driver using the LNK458 and it works fine, but will not restart when dimmed. Is there a way to correct this?
Please provide more details about the problem (operating conditions, type of dimming - pwm or triac)
Please also send the schematic and the power supply specifications to narrow down the variables.
I am using the schematic in RDR251. I added turns to the transformer secondary for operating 8 LEDs at 250ma. The circuit works well and dims fine. The problem is; if dimmed and the power is cycled, the circuit will not restart at the dimmed point. Full power must be reapplied to restart. Could it be the transformer primary inductance?
When you recycle the power at a very low dimming point, it is possible that depending on how good or bad the triac that is being used, the triac may not be able to turn ON because of insufficient current (triac requires latching current and holding current to work properly). One way you can improve this is by tuning the bleeder and damper circuit. Kindly review section 3 and 4.1 on RD251 report for more info.
Thank you very much. I changed C3 to .15uf and R7 & R8 to 20Ω and it is much better and acceptable to my customer.
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