Best Converter Topology for 100w, 150W 180W - Page 1
Forum section: electronics / projects

author: jman
author_rank: Contributor
timestamp: January 27, 2015, 05:54:39 am
content: Hi everyone,what do you think would be the best converter topology for the following 100W, 150W, 180W for a constant current output.Thanks

author: Psi
author_rank: Super Contributor
timestamp: January 27, 2015, 06:01:49 am
content: depends how you define "best"CheapEfficientSmallLow rippleall of the above.etc.

author: rx8pilot
author_rank: Super Contributor
timestamp: January 27, 2015, 06:06:35 am
content: What are you converting?

author: Fsck
author_rank: Super Contributor
timestamp: January 27, 2015, 06:13:09 am
content: ^ as above.voltage and current required are also important..

author: jman
author_rank: Contributor
timestamp: January 27, 2015, 06:17:34 am
content: 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

author: jman
author_rank: Contributor
timestamp: January 27, 2015, 06:19:59 am
content: input is AC 85-220Vacoutput Power is 100W, 150W, 180W

author: ajb
author_rank: Super Contributor
timestamp: January 27, 2015, 06:25:38 am
content: What output voltage/current? Converting 85-240VAC to 5V at 30A is different than converting it to 200V at 1A.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 27, 2015, 06:33:14 am
content: ^Leaning towards a single transistor flyback converter though.Tim

author: jman
author_rank: Contributor
timestamp: January 27, 2015, 06:36:45 am
content: @Ajb output example : 38Vdc/4200mA

author: ali80
author_rank: Contributor
timestamp: January 27, 2015, 09:33:58 am
content: 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

author: bktemp
author_rank: Super Contributor
timestamp: January 27, 2015, 09:38:57 am
content: 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.

author: Psi
author_rank: Super Contributor
timestamp: January 27, 2015, 09:47:45 am
content: A TL494 or similar and toroid or bobbin core transformer is relatively simple to build and understandIts often used in car amps to get quite a bit of power at reasonable efficiency without being too expensive.

author: johansen
author_rank: Super Contributor
timestamp: January 27, 2015, 11:38:57 am
content: 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.....

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 27, 2015, 11:54:09 am
content: Quote from: Psi on January 27, 2015, 09:47:45 amSimple, 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

author: penfold
author_rank: Frequent Contributor
timestamp: January 27, 2015, 10:51:57 pm
content: 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.

author: Psi
author_rank: Super Contributor
timestamp: January 28, 2015, 02:15:38 am
content: Quote from: T3sl4co1l on January 27, 2015, 11:54:09 am? Tl494 can be regulatedBoth current and voltage

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 28, 2015, 03:28:28 am
content: 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

author: mrpackethead
author_rank: Super Contributor
timestamp: January 28, 2015, 04:12:09 am
content: best, is very hard to tell you without you telling us what is important.Do you need it to be cheapDo you need it to be extremely reliableDo you need it to work in a wide range of tempsCan it be electrically noisydoes it need to be isolateddo you need to pass any standards.

author: jman
author_rank: Contributor
timestamp: January 28, 2015, 10:04:44 am
content: is flyback ok @ 180W Power Output?

author: bktemp
author_rank: Super Contributor
timestamp: January 28, 2015, 10:16:00 am
content: Quote from: jman on January 28, 2015, 10:04:44 amIt 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%.