transformer for wide input range

Hello ljarillas,

There is a little problem when designing power supplies for up to 580Vac input. Firstly, you must know the meaning of 580Vac. This “ac” business is for energy distribution only, to characterize AC power lines. For you what is important is what really happens after the AC input is rectified to DC. Taking into account some variations, you can end up with as much as 900Vdc rectified voltage. Any “Universal AC solution” can be used up to 600Vdc, our parts are capable to withstand up to 700Vdc. As you can see, this is quite short of your 900Vdc requirement, and if the design is flyback with extra clamp voltage you need components to withstand in excess of 1150Vdc.
Still, we provide a “work around” for this situation. Check our StackFET solution, you will find the answer to your problem: http://www.powerint.com/node/232
To make you even happier, you can actually use our free PIXls Designer software to assist with your transformer design. All you have to do is to start a new transformer design and place the right voltage value your transformer will see. Try to understand this example, you will see that the selected part (LNK304P in this case) is never exposed to very high voltages, only the transformer is connected to the whole input voltage trough Q1 (IRFBC20).

Cheers,
PI_Crusher

Thanks for the reply Crusher. Yes, I realize the >700Vdc problem and currently using Stackfet solution. But when using the PIXI Designer, I noticed that for a given output, there is no difference on the transformer when I change the input voltage from 58-265Vac to 58-580Vac other than there is a warning regarding high drain voltage which is understandable and can be solved by the stackfet solution.

So, does that mean that i can use the transformers used in the reference designs with 265Vac input in a 580Vac-input design if both have the same output voltages and current?

Thanks.

Hello ljarillas,

LNK304P (and many other parts we provide) has a very precise internal current control for the main switch. You need to provide the maximum/minimum voltage trough our design software only for design details related to current, wire gauge, filter capacitors, etc. Otherwise, the higher the input voltage is the faster the current will increase trough the (transformer) inductance and the controller will take care to end the conduction time (shorter ON time). So it is right, use the transformer as shown by PIXls and ignore the warnigh if you use StackFET topology (but check the split voltages to make sure the DC rail plus clamp voltage is not giving you problems).

Cheers,
PI_Crusher

Thanks Crusher. Can I email you the schematic for our design fo you to comment on it? Thanks.