Please can you  advise if the lack of any filter impedance in the neutral line will mean it will fail Conducted immunity compliance testing?

We cannot have any impedance in the Neutral line because we have a triac in the neutral, and the triac load current flows in the neutral, so we cannot put imedances in there.

Also, the triac drive circuit is obviously referenced to the neutral.

We have blown air over the PCB so the 17W will be fine here, we believe.

Also, please confirm that out Buck diode will need to be SiC?

Also, please advise if the opto feedback method, or the "bootstrap" method gives lower standby power?

Hi Treez, 

Thanks for using Power Integration products. 

LNK TN2 Size 9 can be used for 24V output. But, it cannot be used as high as 17W output. 

LNK XT2 Size 9 is up to 10W. It can be extended to 12W but IC thermals will be high. 

Opto will not yield to lower Standby power. Opto is used to increase regulation accuracy. 

Buck diode: ultrafast  < 35nsec Trr or SiC can be used. 

                   SiC will be more efficient and will have lower device temperature with the penalty of device cost. 

Thanks 

Regards 

PI-CHLOE 

Thanks, we do have blown air, wouldnt that make it OK..?

Worst case is 0.862W conduction loss....switching loss will add to that , as you know, but if we use SiC, we will have lower

switching loss as rev rec current spike lower.

Thanks, you kindly say opto feedback doesnt give low standby power...but the LNK3209 datasheet says that the opto method yields the lowest standby power. (page 7).

Please could you  confirm how to get lowest standby power with LNK3209 in Buck?

Hi Treez, 

If there is a fan that will cool down the IC, It will help in to lower down the IC temperature. 

Adding the SiC will also help in the efficiency and thermal of the design. 

For the Opto statement in the datasheet, Please see attach file. 

As you can see in the attach file, the IC is NOT biased via the output. It is being biased in the DRAIN side. 

If the IC being biased in the DRAIN side, power loss in the IC will be high. This section needs to be updated in the datasheet.

We have already update the AN70 for this statement.    

For lower standby power, 

If you have a preload resistor in the output, you can increase the value (R20). But this will increase the regulation during light loads. 

Please check if the regulation is still acceptable. 

Please also used 0803 for the BP cap, 0805 X7R is more stable with respect to voltage applied to the BP pin.  

Thanks 

Regards

PI-CHLOE