High power AC/DC converter for soldering iron

Posted by: kasloV on 02/06/2018

Hello!
I'm designing a supply to power soldering iron. My specifications:
- Input voltage 230VAC
- 1st output 5V 0.5A for digital circurity
- 2nd output 24V 3,33A for iron
- Total power 82,5W
- IC - TOP267VG Open Frame
- Transformer - ETD29

I'm using PIexpert for calculations:
-VOR 100.00 Volts - Reflected Output Voltage
-VDRAIN 575 Volts - Maximum Drain Voltage Estimate (Includes Effect of Leakage Inductance)
-PIVB 60 Volts - Bias Rectifier Maximum Peak Inverse Voltage

1st output
-IRIPPLE1 0.40 Amps - Output Capacitor RMS Ripple Current
-PIVS1 26 Volts - Output Rectifier Maximum Peak Inverse Voltage

2nd output
-IRIPPLE2 2.68 Amps - Output Capacitor RMS Ripple Current
-PIVS2 116 Volts - Output Rectifier Maximum Peak Inverse Voltage

Can you please tell me if this circuit will work correctly? Are the output capacitors too small/big? Is the clamp and feedback circuit designed properly? Do i need to add extra filters? What happen if I accidently short the circuit without using current limmiting feature?
The device will be for my home use only

Files

Attachment	Size
Schematic	19.68 KB
transformer.pdf	1.45 MB

Comments

D4 is likely too small, and needs a snubber,

R7 -> 100 ohm

C6, C7 need to handle 1.5A ripple each - are they rated for this?

R5 should be 10k for a 5V o/p and a 2v5 TL431 ...

C10 should be 47uF 63VDC

Hi KasloV,

WIth regards to your inquiry, the TOP267VG in terms of power requirement is already suitable/enough. However for the transformer selected which is ETD29, is this the recommended core in the PIExpert sheet? If possible that you can share the sheet then that would be helpful. On the other inquiries below are the answers:

Can you please tell me if this circuit will work correctly?
-The circuit looks fine and will most likely run and perform as expected.

Are the output capacitors too small/big?
- This depends basically on your output ripple requirement. Adjust accordingly as needed but keeping in mind that the current rating (RMS capacitor current rating) must also be considered.

Is the clamp and feedback circuit designed properly?
-It seems R5 is too high for your feedback resistor. Kindly verify properly with respect to the specs of the TL431.

Do i need to add extra filters?
- Input filters? or output filters? Depending on your requirement you may add as needed.

What happen if I accidently short the circuit without using current limmiting feature?
-The default current limit should kick in if the external resistor is not used (but current pin must be connected to ground).

Hope this helps.

Leo

Thank you very much for the reply.
I changed the value of R5 to 10k. It was a little math mistake.
Piexpert recomends me to use EI30 core but it's hard to get them in my country. Acording to TOPswitch-jx application note ETD29 looks fair enough for 80W (table 5).
I attached the sheet as you asked. Note that PIXLs gives me no errors and warnings, but is you have any other considerations please let me know
Thank you for your help

Attachment	Size
TOPSwitch-JX_Flyback_Design2_Copy00.pdf	1.6 MB

Hi Kaslov,

Looking at the PIExpert sheet everything looks fine. I suppose this should work as as expected. Should you have any more inquiry please feel free to message us. Thank you very much.

Regards,

Leo