TINY feedback without opto coulper

Hi,

Please refer to our design example DER-110 which I believe is similar to what you wish to design.

http://www.powerint.com/sites/default/files/PDFFiles/der110.pdf

While it is possible to obtain improved overall regulation in a multi output design, the balanced feedback technique that you are thinking of using, provides improved regulation of the second output at the expense of a slight degradation of the regulation of the first output. This is often a tradeoff and works well. You muct however decide if you can live with this tradeoff or if your requirement is better met using a one tightly regulated output from which the feedback signal is obtained and a tightly regulated second output using a secondary linear regulator.

I hope application note (AN-22) will help you with the selection of components for your balanced feedback circuit.

Other than the fedback circuit, regulation is dependent on construction of transformer. Please refer to our Application Note AN-22 for additional information on this subject:

http://www.powerint.com/sites/default/files/product-docs/an22.pdf

Regards

PI-Sarek

Your AN-22 is informitive, even though it has a drawing error in figure 4, but does not answer my question. I want to use the TL431 but not the costly, short lived optocoupler. There should be a simple network I can put between the opto and EN imput for feedback control.
I know Balu can figure this out.

What say you?
Harry
PS You have the slowest website in the world!

Hi,

1. I understand that you would like to design a circuit using TNY279. The circuit shown in DER-110 shows exactly that. I request you to take a look at the circuit in DER-110.

2. You can use a TL431 circuit to design a suitable feedback circuit. One way to design this circuit is to drive a PNP transistor instead of the optocoupler and the PNP transistor could in turn drive the base of transistor Q1 shown in DER-110.

3. Page 14 of AN-22 provides the necessary explanation behind the calculation technique of designing a balanced feedback circuit when designing multiple output power supplies.

4. I am afraid we do not have a dedicated application note specifically for the implementation you seem to have in mind but I hope the above explanation helps you to design a circuit for your application.

5. I regret any inconvenience due to the speed of our website. I will have that communicated to our IT department.

6. I reviewed Fig.4 in AN-22 and did not find any errors. I will be grateful if you could provide me aditional information regarding the error you have mentioned.

Regards

PI-Sarek

I see no instances in all your docs of a TL431 with no optocoupler in the feedback loop. I need good regulation, high reliability and low cost and size, which your circuits diagrams do not show. Please don't school me on dual feedback sources, been there, done that.
So you are stating, "Good regulation requires an opto coupler even if the output is non isolated"?

Sorry, It is Fig 10 in AN-22 that has C3 floating off RTN.

Harry

Hi,

1. DER-105 shows a design example of a multiple output non isolated flyback using TOP243Y and TL431 based balanced feedback circuit without using any optocoupler. As indicated in my last response, this circuit shows the use of the PNP transistor instead of the Opto Coupler.

I have provided a link below for DER105.
http://www.powerint.com/sites/default/files/PDFFiles/der105.pdf

Page 5 of the DER shows the schematic.

I do not have a schematic that shows a similar solution using the TinySwitch.
I hope you will be able to use the information we have provided in DER105, DER110 and AN-22 and create your own schematic for your design.

Regards

PI-Sarek