Feedback Design
Posted by: Arindam
on
Hi,
I am reading the application notes of TinySwitch 3 family design guide (pdf is given in the attachment). In the TL431 feedback design section a table is given, where different feedback components can be selected for different output voltages, but no generalized formulae or procedure is given. Where can I find some generalized formulae or procedure for feedback design of SMPS?
Arindam
Files
| Attachment | 大小 |
|---|---|
| an-90_tinyswitch-iii_family_design_guide.pdf | 3.93 MB |
评论
I understand, but how I design Cfb2, Rfb1, and Rbias?
Hi Arindam,
100nF Cfb2 is recommended so that TL431 does not respond to the cycle-by-cycle output ripple voltage.
Rfb1 is designed to limit the feedback current through Ufb1.
1kΩ Rbias provides the minimum operating current of TL431 which is approximately equal to 1 mA.
Hi Arindam,
You can use the voltage divider formula to solve for the value of Rs1 given the desired Vout (Rs2 is always 10kΩ).
The target voltage is set at 2.5V - TL431 reference voltage.
2.5 = (Vout * 10kΩ) / (10kΩ + RS1)