Best Converter Topology for 100w, 150W 180W

[jman]

Hi everyone,

what do you think would be the best converter topology for the following 100W, 150W, 180W for a constant current output.

Thanks

[Psi]

depends how you define "best"

Cheap
Efficient
Small
Low ripple
all of the above.

etc.

[rx8pilot]

What are you converting?

[Fsck]

^ as above.
voltage and current required are also important..

[jman]

let's say if we go for a cheap converter what kind of topology for the following output power?
same as for the efficient, low ripple etc.


thanks

[jman]

input is AC 85-220Vac
output Power is 100W, 150W, 180W

[ajb]

What output voltage/current?  Converting 85-240VAC to 5V at 30A is different than converting it to 200V at 1A.

[T3sl4co1l]

^

Leaning towards a single transistor flyback converter though.

Tim

[jman]

@Ajb output example : 38Vdc/4200mA

[ali80]

usually for powers below 200w flybacks component cost is cheaper but it is much more complex to design and control properly and is a lot noisier.
so i recommend going with forward or half-bridge or something similar

[bktemp]

If a PFC is used, a LLC resonant converter would give probably a higher efficiency and could be smaller than a forward or half-bridge converter, because it needs no additional inductor. Otherwise forward or half-bridge converter are the typical choice.

[Psi]

A TL494 or similar and toroid or bobbin core transformer is relatively simple to build and understand

Its often used in car amps to get quite a bit of power at reasonable efficiency without being too expensive.

[johansen]

the best topology is rather dependent on how much money you want to throw at it.

even at 100 watts you have a rather incredible selection of mosfets across 2 orders of magnitude to choose from..
do you want.... 50Khz and 99% efficiency or 500Khz and 98.5% efficiency when mixed with a ferrite core of the latest generation? (but it costs less than half as much...)

or do you want 1Khz and a 98.5% efficiency using a tape wound amorphous core.. but, you don't waste one hundredth of the switching losses in the fet driver circuit and its no load losses are 1 mega ohm... rather than 100kohms.....

[T3sl4co1l]

A TL494 or similar and toroid or bobbin core transformer is relatively simple to build and understand

Its often used in car amps to get quite a bit of power at reasonable efficiency without being too expensive.

Simple, maybe.  That doesn't mean it's right.

Even the cheapest Chinese crap PSU doesn't get away with that, because 1. they're dealing with real live mains, and 2. the output has to be regulated.

Tim

[penfold]

Established commercial designs would tend to be a single switch forward.  100-200W is crossing the boundary where the flyback and single switch forward cross over in terms of their viability.  Unless you really require high efficiency or small size then its not really worth going for LLC and really for that kind of power and input voltage the efficiency for anything but an exceptionally designed LLC will be marginal.

[Psi]

A TL494 or similar and toroid or bobbin core transformer is relatively simple to build and understand

Its often used in car amps to get quite a bit of power at reasonable efficiency without being too expensive.

Simple, maybe.  That doesn't mean it's right.

Even the cheapest Chinese crap PSU doesn't get away with that, because 1. they're dealing with real live mains, and 2. the output has to be regulated.

Tim

?  Tl494 can be regulated
Both current and voltage

[T3sl4co1l]

Can be, but it's much more complicated, especially to implement true current mode control!  Your example (car audio amp) is exactly the counter-example of good design, as it implements none of these..

Tim

[mrpackethead]

best, is very hard to tell you without you telling us what is important.

Do you need it to be cheap
Do you need it to be extremely reliable
Do you need it to work in a wide range of temps
Can it be electrically noisy
does it need to be isolated
do you need to pass any standards.

[jman]

is flyback ok @ 180W Power Output?

[bktemp]

is flyback ok @ 180W Power Output?

It can be done, but you will get a high peak current, reducing the efficiency of the circuit. This high peak current has to be absorbed by the output caps. This is the main cause of failing caps in smps.
In ideal case the peak current will be 4 times the output current. If the input voltage changes, the peak current will even get higher, because the duty cycle moves away from the ideal condition of 50%.