change der286

Posted by: mickel on 01/07/2013

Dear Forum

LNK419 support 50 watt, i need to design a LED driver about 50 watt(35 V 1.5 A), but der286 design a LED driver with 30V,1A(30 watt), how i can change Der286 Circuit to Support 50 watt LED driver?

if i design a 50 watt(35V 1.5A) driver, can i use this driver for 30 Watt(30V 1A) application?

mickel

Comments

Hi,

LNK419 can support 50W once set to full mode. That is by increasing the BP capacitor (C9) to 100uF. Reduce also the inductance and the corresponding feedback resistor as per the attached spreadsheet.

Regards,

PI-Jono

Dear Jono

Thank u for reply,I see file and you recommended EI35 Transformer,But Can i USE PQ2625 Bobbine for 50W Application in 66KHZ switching frequency(LNK419 switching Frequency)?

What PIXIs Designer Not support PQ2625?

Hi Mickel,

Yes you can use PQ2625, the paramaters were manually entered in your spreadsheet as a reference. The spreadsheet can adopt any type even a custom core for your flexibility.

Please note that the spreadsheet will not calculate the winding if it will fit the bobbin because the end designer will have infinite iteration on how the transformer is built. Leakage, coupling resistance of the transformer should be check in final construction.

Regards,

PI-Jono

Dear Forum

1-Can I use from figure 4 schematic(With Primary Side Aluminum Capacitor) in der286 document for build 50watt Driver ?

2-LNK419 have protection aganist short circuit?

Hi,

Yes you can use the schematic in DER 286 as starting point for designing 50W. You might adjust some component values (full mode setting) to meet your target current and slight tuning on EMI filter to meet EMI for 50W. You might need redesign the heatsink to meet your thermal performance.

Yes, LNK419 has a short circuit protection through the FB pin. During short circuit, bias voltage should colapse so the IFB current is less than 5uA. Make sure to minimize the leakage of the transformer in order to meet this requirement.

Regards,

PI-Jono

Dear Pi Senior

1-Thank you for Guides,how i can obtain full mode setting for EMI configuration and other parameters for LNK Devices?

2-i use PI Recommendation for Transformer windding and try to Leakage Near of PI Recommendations, what is your mind about "minimize the leakage of the transformer" to obtaion conditions of short circuit protection? it is mean that we obtain leakage below of PI software Recommendtiona?

this problem explain in this links:

https://www.powerint.com/en/forum/led-driver-design/der286-30w-short-circuit-feature-not-run

do PI test this Problem?

Mickel

Hi,

1- Increase the current rating of the EMI filter. Make sure it will not saturate at any given time. Higher input current means higher differential noise, as such you may need to increase your X-cap. Conduct EMI test for the reasonable filter in order to avoid over design.

2- In order to minimize the bias leakage inductance, you need to construct the bias winding as close as possible possible from the secondary winding. DER 286 construction is correct but you can further remove one layer of tape spacing between the two if there is too much ringing in the bias signal. For flyback topology , the lower the leakage the better.

Most of reference design are verified in short circuit condition. Please refer to the waveforms for the reference.

Regards,

PI-Jono