LNK306 TECHNICAL INQUIRY

Posted by: bong_mendoza on 05/08/2015

Hi.

I design a universal power supply using LNK306 switcher with input voltage 19V to 265V AC and DC.

My output is 22V DC. I am trying to support up to 2.2W load, that means it drawing 100mA of current.

I dont have any problem with higher voltage inputs but when using lower voltage input range, my protoytpe

does not start up. To be exact, at 19V DC input, my maximum load that can give me a 21.65VDC output is 1.5W.

If I increase my load higher to 1.6W or more, it could not start up. I monitor the current drawn from the mosfet and it is 235mA.

Can LNK306 still provide above 235mA of current? I need to support at least 2.2W of load. What do you suggest?

My design is based on An37 application note and PI XLS results. My inductor is 1mH with 600mA DC capacity.

I can provide my schematic if you need to analyze.

Thank you very much.

Bong

Comments

Follow up question to the above, If I want to change LNK306 to a higher power IC that have best compatibility, what IC to you suggest?

Thanks for Posting question into forum. How did you design your Power Supply? Did you use our PI Expert Software or any of our DER Reports, Please send us the Schematic. Please download our PI Expert Software and you can validate your design by entering your specifications. Our PI Expert Software provides the Optimised solution and Magnetics design.

Regards,

PI-KSAN

I think my msg got lost that I posted a moment ago. Here it is again.

A quick question: what is max rise time for the input DC source for proper functioning of the LNK6777 chip?

DC bench supply I have goes up to 250V in approx 250 ms
Is it not too slow?
Do you think the controller will shut down switching if it is so slow?

The input goes up is less than 2ms in applications where it will be used,

Appreciate a prompt finding of an answer for this question.
-robin'

Thank you for your reply KSAN,

Design was based on PI Expert and some LNK307 Application notes. Attached is my schematic.

The only error I am getting in PI Expert is that the Vmin is less than 70V.

This circuit is tested with VDC input minimum 19VDC and works fine to provide 22VDC output 1.5W consumption.

But if I increase the load consumption further to 1.6W and higher. The output is on and off and it seems that LNK306 is resetting. Is it because the LNK306 cannot give more power anymore. How can I increase the power capacity? Is there any IC that is exact replacement of LNK306 but higher power.

Thank you,

Bong

Attachment	Size
LNK306 SCH (176.15 KB)	176.15 KB

Hi,

Yes you can achieve more power with LNK306 Part. As the data sheet says it can provide output current of Maximum of 360mA, so your output voltage is 22V. The total power can go upto 7.5W. Could you please explain what exactly means ressetting, is the output voltage oscillating and unable to regulate? Increasing the Inductance for your design will provide additional power. We won't recommened any design below 50 VDC input, the part will able to provide work as low as 19VDC, but we won't recommend for low VDC input as the IC has some internal issues.

Regards,

PI-KSAN