Hi every one,
I like to learn about SMPS and for start I like to use CM6800 chip for controller but I have no idea where to find the suitable core to start and I found in my local market there is many SMPS use to replace flyback converter in TV set and my question is how or where I can find formula to convert an flyback converter to a dual forward converter.
I like to learn about SMPS and for start I like to use CM6800 chip for controller but I have no idea where to find the suitable core to start and I found in my local market there is many SMPS use to replace flyback converter in TV set and my question is how or where I can find formula to convert an flyback converter to a dual forward converter.
Not an expert in this field but I suspect there are fundamental problems to doing this. A flyback converter uses an inductor while a forward converter uses a transformer. Inductor cores are usually gapped due to the high energy stored in the core while transformer cores aren't.
You'll need a lot of turns on an inductor core to get a decent transformer which will increase resistance and hence losses. I think this just gets you the worst of all possible worlds.
You'll need a lot of turns on an inductor core to get a decent transformer which will increase resistance and hence losses. I think this just gets you the worst of all possible worlds.
sorry I think you misunderstanding my post I am not talked about the Flyback in TV st to produce the HV supply but the PSU for all electronics component inside TV set use Flyback topology and the PSU I talked about is use transformer that is big even bigger than my 750 PC PSU
The PSU I show to you use UC3842AN with Flyback topology
I would like to use CM6800 with dual forward converter topology
what I need to know is how to convert the transformator use in flyback topology to dual forward topology,
let say in flyback the primary use 100 turn and 38Khz freq now how to calculated the turn needed in dual forward let say use same freq.
is this clear enough ?
I would like to use CM6800 with dual forward converter topology
what I need to know is how to convert the transformator use in flyback topology to dual forward topology,
let say in flyback the primary use 100 turn and 38Khz freq now how to calculated the turn needed in dual forward let say use same freq.
is this clear enough ?
You need to determine the Al value of your core which tells you the inductance you get for the number of turns.
Number of Turns required = SQRT(desired inductance in mH / Al) * 1000
Wind 20 turns on the core and measure/calculate it's inductance, then you can work out how many turns you need. But as I said, the flyback core will be gapped with a low Al meaning you'll need 100's of turns to get an efficient transformer. May not fit on the bobbin or it may have too much resistance for your desired power level.
You will also have to consider the range of input voltages, the output voltages, peak power to be able to determine the flux in the core and so the number of turns and of what gauge wire. But the datasheet/application notes should have all that design information for you.
Number of Turns required = SQRT(desired inductance in mH / Al) * 1000
Wind 20 turns on the core and measure/calculate it's inductance, then you can work out how many turns you need. But as I said, the flyback core will be gapped with a low Al meaning you'll need 100's of turns to get an efficient transformer. May not fit on the bobbin or it may have too much resistance for your desired power level.
You will also have to consider the range of input voltages, the output voltages, peak power to be able to determine the flux in the core and so the number of turns and of what gauge wire. But the datasheet/application notes should have all that design information for you.
Is a double forward converter a 2 switch forward converter, or an interleaved forward converter someone please explain?
I've pulled apart a few transformers from pc power supplies, most of them i broke while trying to remove the cores, some survived. It's not fun.
As for the flyback transformers you could grind the mating surfaces of the core pieces until they mate properly. However you'd need to make a new bobbin too for them to fit in...
I've pulled apart a few transformers from pc power supplies, most of them i broke while trying to remove the cores, some survived. It's not fun.
As for the flyback transformers you could grind the mating surfaces of the core pieces until they mate properly. However you'd need to make a new bobbin too for them to fit in...
I believe we talk about interlaved forward converter,
I do pulled some transformer and use heat to separated it its working
so you told me the only thing to do to convert a flyback transformer to forward converter just erase the gap between EE or EI core ?
No, you have to completely redesign the circuit. The controller IC will be set up for flyback conversion and so may only be monitoring primary current. You may have to re-configure for secondary voltage regulation, depending on what you are trying to achieve. The compensation circuits will need adjustment as will getting the right turns ratio/inductance/on-time/operating frequency.
Do you have any books on SMPS design?
Alternatively, you could just rewire everything and see what happens - but it'll probably be bang.
Do you have any books on SMPS design?
Alternatively, you could just rewire everything and see what happens - but it'll probably be bang.
No, you have to completely redesign the circuit. The controller IC will be set up for flyback conversion and so may only be monitoring primary current. You may have to re-configure for secondary voltage regulation, depending on what you are trying to achieve. The compensation circuits will need adjustment as will getting the right turns ratio/inductance/on-time/operating frequency.
Do you have any books on SMPS design?
Alternatively, you could just rewire everything and see what happens - but it'll probably be bang.
off course I will not use the old circuit, I will use a new circuit basically based from CM6800 application note, I also have some example working circuit with CM6800 from PC PSU.
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