Non-isolated 200W SMPS

[marko.severin]

Greetings,
I need to design a SMPS with the following: Vin = 120-300V, Vout = 13.5V, Iout = 15A. It must be as small and as efficient as possible. Also, it does not have to be isolated and it does not require PFC.
Basically what I need is a step-down converter. I've done some basic calculations and a two-stage buck converter yields quite poor efficency, since I have to use 600V mosfets for the first stage.

So, what topology would you recommend? A LLC resonant converter seems to be a popular choice, but given the wide input voltage range, I do not believe it to be a good choice.

Thanks to all!

 

[islurpundalik]

the power integration company provides a variety of SMPS controllers according to your specific needs. it also provides a good design support software 'PI expert' to calculate the neccesary parameters for free. I think you should look into it.
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-pundalik

 

[eem2am]

go for a 4 stage interleaved flyback, with each stage switching 90 degrees apart from the next.

otherwise, at that power level you are looking at a bridge converter................just a plain half bridge should do ,
you rightly say the LLC is not for you because of your wide Vin range.

i do not think powerint.com have controllers for your power level........

they have the "hyper" series but that is resonant

 

[Orson Cart]

Since your Vin max is only 300V and the power only 200W a straight buck converter (or resonant buck converter) with a mosfet in parallel with the freewheel diode (for synchronous buck operation) will give the highest efficiency as only one semi-conductor is in series with the current at any time, you will need some good caps on the input to supply the 15A pulses, but the mosfets need only be 350-400V, 40A rated (or bigger), a resonant buck will give lower switching losses than a straight buck and can be synch switched also. Interleaving buck converters will alleviate the stress on the input caps, you could have 2,3 or 4 stages, running at 50kHz say (to keep switching losses to a minimum), IC's exist for implementing all of the above - high side gate drive needed to run the buck FET.
Regards, Orson Cart.