about di-66 project

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Hi, I am Adel pourmand an electronics student in university and i try to make a SMPS with top switch and this is my first SMPS project and i need help, i searched and found project call di-66 from your site this project uses TOP246Y, now i have some questions if can answer me: 1-why you use 1N4007G and what's different with 1N4007 or 1N4007L that you used 1N4007G? 2-can I use 1N4448 instead of LL4148? 3-i bought TOP246YN instead of Top246Y,what's your opinion about this component can i use this one instead of Top246Y?

Hi Adel

1N4007G is glass passivated version of 1N4007. If you can't obtain then replace with FR106.

The LL4148 is just the SMD version of 1N4148 but any diode with trr <75 ns and >200 mA rating should be fine.

TOP246YN is lead free version of TOP246Y, other than that they are the same.

Good luck with your project.

Regards

Chekov

hey adel, first of all best of luck for ur project & thanks for choosing PI device. further, as Chekov said, u can use FR106 or Fr107... Sure u can use 1N4148. and yes , you may proceed with TOP246Y in place of TOP246YN as if it is a college based project. "N" denoted a Pb-free or lead free component. good goin...best luck
thank you very much , i got it about di-66 project 1-please introduce me what is CTR(current transfer ratio) in optocouplers and is it important parameter? and tell me some optocouplers instead of PC817C because i did not find it but PC817B and PC817 is available? 2- about MBR20100CT, it has two diode inside it,>i should use just one of them or i must connect both anode together and use it in circuit? 3-what is the volatge and current of bias winding in di-66 ? 4-what is the volatge and current of "C" pin of TOP246Y? 5-what is the volatge and current of "F" pin of TOP246Y? 6-can i use R=150kohm from "12V output" to "reference pin of LM431" to improve crossover regulation? 7- i used 3.5uH instead of 3.3uH for L2 & L3,is it important? 8-i used two 1Mohm & 0.25 watt instead of 2Mohm 0.5Watt,please tell me your opinion? ,Thank you, Adel

Hello Adel,

1) CTR = current transfer ratio = gain. A gain of 100% means 1 mA in LED side causes 1 mA in transistor side. A gain of 200% means 1 mA in LED = 2 mA in transistor.

Any CTR is ok but we recommend picking one with a specified range eg 100-200% so that you don't end up with variation in production - say 80% to 600%. Why? Well the CTR gain forms part of the overall loop gain so a narrower range makes it easy to ensure a good loop design over the range of opto CTR tolerance. I'd go for PC817B (the PC817 is likely to have a very wide CTR range).

2) Connect both in parallel ie both anodes together.

3) 12 V, 10 mA
4) ~5.8 V but you generally don't need to worry about the voltage on the pin
5) See datasheet but again don't generally need to consider this - unless I'm missing something you are trying to do.
6) Yes - but there are limits, for example both output must have some load to regulate correctly especially say if the 12 V is unloaded and 5 V is fully loaded.
7) No <10 uH is ok.
8) Also ok. Two resistors are normally required with using 0.25 W types due to voltage rating. Resistor see 375 V DC and 0.25 W = 350 V rating, 0.5 W = 500 V so single 0.5 W is ok but two 0.25 W needed. Interestingly I have heard of 0.25 W resistors failing in the field when only one was used (and therefore voltage rating was exceeded).

BTW take a look at the more detailed report:

http://www.powerint.com/sites/default/files/PDFFiles/der94.pdf

This is very close to the DI-066 design and has more complete design information.

Cheers

PI-Chekov

hi PI expert thank you very much of your last help it was helpfull., about di-66 project 1-please introduce me what is CTR(current transfer ratio) in optocouplers and is it important parameter? and tell me some optocouplers instead of PC817C because i did not find it but PC817B and PC817 is available? 2- about MBR20100CT, it has two diode inside it,>i should use just one of them or i must connect both anode together and use it in circuit? 3-what is the volatge and current of bias winding in di-66 ? 4-what is the volatge and current of "C" pin of TOP246Y? 5-what is the volatge and current of "F" pin of TOP246Y? 6-can i use R=150kohm from "12V output" to "reference pin of LM431" to improve crossover regulation? 7- i used 3.5uH instead of 3.3uH for L2 & L3,is it important? 8-i used two 1Mohm & 0.25 watt instead of 2Mohm 0.5Watt,please tell me your opinion? ,Thank you, Adel