Flickering in the Streetlight application using TOPSwitch 256EN LED driver board

Hi,

Is this a non-PF or with PF solution.  Please send the schematic. 

Regards,

PI-Jono

Hello,

Sorry for the late reply. Here is the schematic.

The Parts named DNP have been removed from the present board. 

Hi,

I guess Q1 symbol should be a PNP, please make sure the layout is correct.

For a 24W output design the input capacitance is not enought to minimize the line ripple. Inrease the input capacitance from 22uF to 47uF to reduce/eliminate the shimmer.

The output current is regulated by Q1 which is temperature dependent. At high temperature the output current will drop due to VBE drop on your transistor plus its gain is not limited.  You might consider using a regulated reference for tighter tolerance unless your customer is willing to accept a variation in output current with respect to temperature.

If you still have the luxury of changing the design, rather use LNK-PH or LYTSwhitch 4 devices.  Your design input power will have an input power above 25W which normally requires with power factor and good harmonic characteristic.

By the way consider connecting all of your LED in series to have a balance light output instead of a parallel. 

I hope this help in your design.

Regards,

PI-Jono

Hello,

Sorry for the slipup, yes Q1 is pnp. the Transistor used at Q1 is 1N5401 Is it ok to use 1N5401 instead of 1N5407.

Hi,

No problem, I make mikstakes also before I finalize the design.  1N5401 is a diode, maybe it is 2N5401.

By the way you can use any type of signal transistor because the opto will not require too much current.  You can try even the following:

PMBTA56

MMBT2907A

MMBTA56LT

I hope this helps.  

Cheers,

PI-Jono