Flyback Transformer Circuit to give 600 mA average current but support higher peak current upto 1-2 amp design.

Thread Starter

narendra@sixsensemobility

Joined Mar 7, 2023
7
Hi, Team,
its excited to be here, I just got flyback dc to dc conversion circuit with support of input volt of 80-100 v to output volt - 5V. Attached circuit here on drive : Flyback circuit isolated GND with 200 mA output current.

Could someone please help similar or this to modify to handle more current like 600 mA & peak current upto 2 Amp , that required by my Sim module : A7672s as per datasheet but I'm not using other peripheral of this module, so i'm sure, 1 Amp peak should be enough and average current i could measure with transformer, so including esp32 with BLE active, this sim module PCB was totally consuming 200mA average during HTTP post action (sending data to server) , else consumption is 70-80 mA, so assuming sim module only taking not more than 100 mA in normal mode.

https://manuals.plus/m/d70efb93e7bade7e6e61c78447a99e33b2f6607d08d3fa59b8ac5c65f8bb201d.pdf (Sim A7672s datasheet, if anyone want to go though.)

In short, guys please help me to design circuit with max current 600 mA with peak current support of 1 or 2 Amp. flyback circuit 200 mA.png
Above is mine 200 mA output flyback output circuit with EE1605 transformer.

Please help me to increase current output rating .
 

ronsimpson

Joined Oct 7, 2019
3,149
The schematic has 48V input and you want 80-100. Why 80V? Where do you get 80 volts?
The schematic has two 7V 100mA outputs and you want 5V.
The output current changes from 200mA to 600mA, with 2A peak.
Do I have that right?
This is not a simple change but a totally new design.
This simple one transistor circuit is very hard to make work and does not regulate well.

There are many schematics for a 5V 2A "wall wort" USB charger thing. I would start out there. Find one that uses a IC. Reduce the input turns by 20%.
 

Irving

Joined Jan 30, 2016
4,001
Can't be done with that transformer unless you are prepared to rewind it.

Go to Mouser or DigiKey. Use parametric selection for flyback SMPS chip with Vin > 80v and Pout >= 15W eg TNY177. Download datasheet. Read thoroughly. Follow design guidelines and given PCB layout...

1678200605267.png

[edit] Added link to online design software
 
Last edited:

ronsimpson

Joined Oct 7, 2019
3,149
I like the tiny switch line. They have good application notes.
Here is another design.
Note how simple the transformer is.
You will need to remove the diodes on the input and reduce the turns on the primary. (Post #3 and #4)
How much isolation do you need?
1678202147103.png
 

Thread Starter

narendra@sixsensemobility

Joined Mar 7, 2023
7
Sorry sir for delayed reply , actually here in india, today is big Fest of colors 'Holi' & i didn't get notification ring. btw Thank you sir for quick response,
& here answers:

1. I want ofcourse a new circuit for my new purpose for my DC-DC conversion ,
& sir input volt is 80V dc , that peak volt circuit could handle 100v will be better in safe side.

2. output current is need 600mA or more, with peak support upto 1 or 2 amp.

3. Isolation we are doing to separate ground ( as it could be much noisy, coming from EV vehicle battery), as my other circuit has CAN ic, so i need to separate CAN supply ground separate from above.

I just shared by reference design share by my senior mentor sir , just to take idea, that i'm trying to get a bit cheaper (as possible) & simple flyback design like with transformer (i'll rebind, whatever required) with isolation.
 

ronsimpson

Joined Oct 7, 2019
3,149
This looks like an electric car USB charger.
Being an automotive item, it should work over very wide temperature range.
The reason we are trying to push you away from the circuit in post #1 is that they are hard to make work. They often to no work over a wide temperature range. They are very dependent on how the transformer is made, and the gain of the transistor. The output regulation is not good.
 

Thread Starter

narendra@sixsensemobility

Joined Mar 7, 2023
7
Sir, I tried to find such car usb charger circuit or product & found some circuit but not as a product.

finally I just need a bit more help .

if i need to get two isolated output, can i get from same using one transformer.

& sir please also suggest me to design this transformer coils. I'm more trying to find locally such smps circuit. but if anyone get time,please suggest me for winding the transformer for getting 5V 2 amp output. from 80v .
 

Irving

Joined Jan 30, 2016
4,001
You can get two secondaries from that circuit, the second is the same as the first, 2 turns but only needs bifilar not trifilar winding as will be limited to 1A on each secondary - its bad practice to be unbalanced across 2 secondaries. Do you really need two isolated outputs? If you follow the design link in post #2 (design guidelines) it takes you to the online design software which will guide you, but you do need some understanding of how this works and the implications of using particular magnetics - which will also depend on whats available to you locally. 80 - 100v is an no-standard input requirement so some extrapolation from the 85v AC input or 48v DC input options is needed, and you must prototype & test it as the design software can only go so far.

I gave you the basic transformer detail in the circuit above. As this appears to be intended for a commercial product (since cost was an issue) and user safety is important (80 - 100v is considered lethal), a proper design process and a formal testing regime is needed, If that is beyond your understanding or ability to take forward then you probably need to hire someone who knows what they're doing - this is a non-trivial design requirement and a hobbyist approach isn't appropriate.. You have to do the work! If you want a full design and a validated prototype that's not going to come for free.
 

Thread Starter

narendra@sixsensemobility

Joined Mar 7, 2023
7
yes, sir, i was going to mention it in my last reply, if someone could take some pay & i'll be happy to get it done, or i'm already trying to understand & also given this to manufacturers of transformer, now just left part is about transformer.
this video explain below circuit. its seems , without ic : switcher ic

https://drive.google.com/file/d/1TWNf6OfTSGOfDitfw5u4qp9Hvs_lkU74


if there is tip or thanks button to pay, i'll be happy to pay for you help, let me know, if anything possible, & for testing, i'm always ready my side to put my effort as a young startup guy. just i made whole IoT device, only this part was related power electronics, i don't understand much.
 

Irving

Joined Jan 30, 2016
4,001
None of these simple charger circuits are suitable for an embedded automotive application, they won't last 5 minutes. Its not just about the number of turns on the transformer, you need to consider cooling, air-flow, vibration, temperature range, etc, etc if this is to be a commercially reliable part.
 

Thread Starter

narendra@sixsensemobility

Joined Mar 7, 2023
7
ok so sir, you mean, without ic , circuit will not be reliable but with ic, like you shared above circuit with IC : TNY227 , with IC it'll be somewhat reliable.

i've found similar ics anyone like below as alternatives :

1. TOP 244YN or TOP221 , i need 5v, just 8-10 watt fine for my purpose at Vout.
2. LNK304PN or LNK626PG
3. TNY274 or TNY268

TNY268 - seems perfect for my output & cheaper too, easily available at local, Topswitch are bit costly.

I understood now, working & calculation of turns etc as per this doc. https://www.sc.iitb.ac.in/~anurag.1/files/btp-report.pdf , after making test pcbs , i'll update you guys.

Thanks you.
 
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