High efficiency 250W SMPS design

[ejagielo]

Hello,

I am currently designing a 250W DC-DC SMPS with an input range of 18V-90V and an output of 120V, and I am trying to find the most efficient topology for this application (i.e., flyback, forward, SEPIC, etc.) I know that there are pros and cons to each SMPS topology, but I was wondering if anyone knows of the best one to use for this application that maximizes efficiency.

Thanks

 

[goldsmith]

Hi ejagielo
A forward converter would be ok for your purpose .
Best Wishes
Goldsmith

 

[ishailesh]

Hey!

Please look into the following document.
https://ww1.microchip.com/downloads/en/AppNotes/01114A.pdf

 

[ejagielo]

Thanks guys, your advice and the document that you directed me to are very helpful. I am also considering increasing the power level to 500W. However, the document says that forward converters are best for wattages up to 350W. I've also heard that forward converters can theoretically handle up to 1kW, but the MOSFET switching losses become quite high for wattages of this magnitude. I was wondering if a forward converter could still be used for a 500W application. Any thoughts or opinions would be greatly appreciated.

Thanks again!

 

[goldsmith]

converters are best for wattages up to 350W

I gave powers around 1KW from one stage forward converter and higher powers with multistage ! if you be able to find a good mosfet and design a good snubber network there won't be any problem . ( a fly back converter will give powers around 500 watts ! so why a forward can't give higher ? ( there are many tricks for this aim available ! )
A problem in higher powers in forward converter : maximum stress across the DS junction is around 2Vm . and a high voltage mosfet will have larger Rdson . so dissipation at higher currents should be higher ! but there is a trick available ! use a low voltage mosfet and an RCD network ! ( thus the strees can be around Vm ! ) but another manner is to use some mosfets in parallel but higher gate current would be required , but of course lower dissipation ( because of parallel Rdson of each one ) another way is IGBT ! but it has a big disadvantage that can't switch at high frequencies ( as high as enough ! )
Good luck
Goldsmith

 

[Tahmid]

Thanks guys, your advice and the document that you directed me to are very helpful. I am also considering increasing the power level to 500W. However, the document says that forward converters are best for wattages up to 350W. I've also heard that forward converters can theoretically handle up to 1kW, but the MOSFET switching losses become quite high for wattages of this magnitude. I was wondering if a forward converter could still be used for a 500W application. Any thoughts or opinions would be greatly appreciated.

Thanks again!

For the 250W design, a forward converter is suitable. However, I would recommend the half-bridge converter if you plan to increase power level to 500W (I would still recommend it if you didn't). You will find loads of circuits and designs online, that use the half-bridge topology. Check various forums, including this one.

You will have to decide how you're going to drive the MOSFETs. You could use a gate drive IC or a gate driver transformer.

However, it is not impossible to use a forward converter for power output of 500W. I wouldn't, though.

- - - Updated - - -

another way is IGBT ! but it has a big disadvantage that can't switch at high frequencies ( as high as enough ! )
Good luck
Goldsmith

It might be interesting to note that there are some IGBTs that may be used at quite high frequencies. One such example is the IRGP50B60PD.

 

[goldsmith]

It might be interesting to note that there are some IGBTs that may be used at quite high frequencies. One such example is the IRGP50B60PD.

Hi Tahmid
How about price ? are they economical for a simple purpose ? i hope you know that an IGBT will be Un safe in high inrush currents and high dissipations ( it's characteristics will be changed with temperature ) . and i hope you know about real equivalent circuit of an IGBT ! ( a BJT ( at least one BJT ) and an RCD network ! it is as a parasitic behavior . so safety of a mosfet is more than IGBT in high frequencies and higher powers . and don't forget that price is most important issue for a designer ! and a notice about forward converter : if your experience be as high as enough powers up to 3 KW is possible too with a forward converter , but not a single ended forward converter .
Best Wishes
Goldsmith

- - - Updated - - -

be used at quite high frequencies

Tahmid
By the way is 150 KHZ or 200 KHZ a quite high frequency ??!!

 

[Tahmid]

Tahmid
By the way is 150 KHZ or 200 KHZ a quite high frequency ??!!

For an IGBT, I would say that 150kHz is quite high frequency and it can be used in a lot more applications that a lower frequency one - one that can only be used upto 20khz, for example.
It should be noted, that IR calls this IGBT an "SMPS IGBT".

http://www.irf.com/whats-new/nr050118.html

How about price ? are they economical for a simple purpose ?

I pointed out the IGBT as I thought it is an interesting device. I never said that it should be used in this application. While price is high, at higher current and power, the price won't be too big a problem. However, of course, at lower current, the price may be restricting.

and don't forget that price is most important issue for a designer !

I wouldn't say so. Price comes later. Certainly, first is the quality, efficiency and longevity of the design. Then, you start thinking about price.

and a notice about forward converter : if your experience be as high as enough powers up to 3 KW is possible too with a forward converter , but not a single ended forward converter .

Of course. I even said in my last post, it's possible. It's just that, I wouldn't do it. I would rather go for a bridge converter. It's, as you say, up to the experience, and of course preference.

 

[goldsmith]

Hi Tahmid

For an IGBT, I would say that 150kHz is quite high frequency and it can be used in a lot more applications that a lower frequency one - one that can only be used upto 20khz, for example.
It should be noted, that IR calls this IGBT an "SMPS IGBT".

http://www.irf.com/whats-new/nr050118.html

I know it is a fast IGBT , but the problem is t select correct words ! i saw it is SMPS IGBT . but when you are mentioning quite high frequency , it means the frequencies above this , aren't available ! yeas it is one of the faster IGBT's . but i still believe the word " quite high isn't ok for that " . it is at LF range .

he price won't be too big a problem. However, of course, at lower current, the price may be restricting.

No ! the price is pretty important . suppose you want design a high power converter . ( e. 5000 P.C.S ) most of the times i prefer to design best things with lower prices . consider when you can design a project with lower price and best quality why you should consume more money to earn that quality ? is that really reasonable ? for example when you want build a simple SMPS for powers around 500 W . is that a good idea to consume higher money when you can pay lower money ? ( of course both of them are in same qualities . )
I hope you got the point .

Of course. I even said in my last post, it's possible. It's just that, I wouldn't do it. I would rather go for a bridge converter. It's, as you say, up to the experience, and of course preference.

Yes most of the times i prefer half or H bridge for aims such as that . but if i have to do that with a forward converter , i prefer to add a master/slave feedback then i can earn powers around 40KW easily .
Best Wishes
Goldsmith