LM3447: 56 watt LED driver with very high PF

Hi,

The calculation tool support design<40W, LM3447 can support higher power. 

You can design it with this tool for key transformer parameters like inductance, turn ratio, then use larger magnetic core for higher power.

Hi Andy,

Inductance will be based on the wattage & this parameter needs to calculate first which is the bottleneck on tool side & hence asking for the help.

regards,

Mitesh

Hi Mitesh,

The pop up message is just for warning user to pay more attention on transformer design and core material. it has no impact on calculation result   

Hi Andy,

one more input needed on this.

My LED string voltage range is from 30V to 56V, where as tool OVP limit is showing 43.6V?

Another query:

Max input peak current is showong 7A in the tool, where as if i cal culculate the value its upto 3.5A max, plz guide me.

Mitesh has attched the calculation sheet for reference, for more details, you can refer this.

HI,

I will check how to fix it....

ok, thanks!

Hi Sagar,

Andy is in Lab test whole day and will reply once back to the office.

BR

Monet Xu

For traformer turn ration calculations, do we need to consider the typical output voltage or Max output voltage?

In our case;

 typical output voltage = 37V & Max output voltage = 56V

Hi,

need to consider the Max Vout for duty cycle below 0.5V at Vin_min.

Okay.

But in the tool, typical output voltage is considered?

Hi Andy,

Do you get some time to look into the tool and fix it for given requirement.

Hi Sagar,

I need more time to check it as it's a quite old part released 10+ years ago....

Okay!

Hello Andy,

Any update on above query?

Also suggest the best proven solution for 56W LED Driver Design as per you.

Input: Universal from 85VAC to 305 VAC;

PFC Requirement: >0.95 at full load

OutPut : 35VDC to 56VDC, 56W

Option 1:  singe stage PFC LED driver

Option 2: (PFC+ FLyback)  2 stage PFC LED driver

Andy,

Can we use LM3447 as secondary side feedback controller? We think to apply the feedback on COMP pin. Can you help with your inputs?

Here is the top level scheme to control from secondary side .

MItesh

Let me check it....