Hi DV,
If a minimum load is not guaranteed, you need to add a pre-load (~30kOhm) across output2. It will consume a few milliwatts however but it should be enough to stabilize the output to be near 24V. Output2 will still swing depending on the loading condition of both outputs as it is not directly connected to the feedback loop, specially at (1)output1 full load output2 no load, and (2) output1 no load and output2 full load.
Also, since both output returns are connected, you can also explore 'weighted voltage feedback' for this design if you really need a tight regulation for output2.
Regards,

Hi BERJ,

Thank you for your reply.

Output 1 is connected with another circuit board and it is consuming current of 120 mA. i am not facing an problem at output 1 side.

I have added preload of 30Kohm as you have suggested but output of output2 is remains almost same. Two 24VDC operated relay is connected with output 2, when both the relays are ON, output 2 goes down to around 27 volts.

i forgot to remark that rather then 20pF(C6) i have used 22 pF and 33 ohm(R6) instead of 34ohm.

What is Weighted Voltage feedback ???

Thank for your support.

Thank you.

Hi DV,
Ok I see it now. The 24V output should come from a separate winding so that it would be less susceptible to loading changes of the 5V output. See attachment for reference.
You can add Rx if you would if you still need to do 'weighted feedback'. This would however also affect your 5V output and will require fine tuning both Rx and R8 as to what your design actually requires.
As for the snubber components (C6? and R6?), it should not affect the closed loop output voltage.
Regards,

Hello,

Thank you for your reply,

I have tried with separate winding for both the output and it works. Added 27Kohm as preload and achieved 24V output at output2.

will pin allotment effect the performance??? output 1 winding is same but for output2 pin allotment which i have tried is given in image.

Thank you for your valuable help.

Hi DV,
I am not seeing any difference with your upload and mine. Regardless, if you are getting the results you need at your current configuration, then it should be fine. Performance can change with the layout but on lower power levels, it should not be much of an issue.
Regards,

Hello BERJ,

Thank you for your valuable reply.

I have tested and working as per expectations.

Thank you..!

Hello,

I am getting AC voltage with DC output and its affecting rest of the circuit.

When i am removing C4 capacitor i am not getting that AC voltage in in output.

what could be the reason?? and i can overcome on it??

Thank you.

Hello mahidadigvijay,

To further review the design, it would be helpful if you also can provide your PCB layout and magnetics construction or your PI Expert design.

Thank you.

Hello sir,

Thank you for your reply.

sharing you details. please give your valuable feedback.

thank you

sharing you details

Hi mahidadigvijay, 

The AC voltage you're observing on the output is the output ripple. Here are some suggestions we propose in order to reduce it. 

1. PCB layout 

PCB layout is a great factor to consider in reducing output voltage ripple because of noises that can be generated. Upon reviewing your PCB layout, we suggest in revisiting your layout on the primary side as some rules have been violated. Please refer to the device design guide: an-82_tinyswitch-4_family_design_guide.pdf (power.com) 

2. Output capacitance 

We replicated your schematic on our PI Expert online tool that you may access on the link provided below :  

https://piexpertonline.power.com/piexpert/design/select?share=7de59d9ba8dd76122c05f77c6eb614093cf83128617118e8c6539140d7264e63 

It gives optimization warnings. You may increase your output capacitance with larger rated ripple current than the specified ripple current on your PI Expert design or post filter capacitance to reduce the ripple. 

The same PI expert design also has a sample layout the you can refer to for your design. 

Dear PI-Hueka,

Thank you for your reply and suggetions.

The AC voltage which i was getting at output vanished when i have added on more capacitor with 2.2nF and junction of that capacitors is connected to Earth ground.

I have attached the schematic for your reference.

Is it advisable to do that to overcome the issue of AC voltage at Output ??   

Hi dv.mahida,  

To answer your question, the implementation is not advisable. As per the prior suggestion, we observed your given PCB layout have power rail loops wide and long, details listed below:  

 

1. Primary Clamp Snubber (D1, D2, R5) loop is within the primary power loop, making it less effective.  

2. Secondary power loop is not tight, and also its snubber loop are within the power loop.  

The stated loops must be tight and small as possible. And we recommend designing snubbers outside a power rail loop. The layout introduces a big factor of the noise observed on the output section.  

Please follow the design guide and design example provided below:  

• https://www.power.com/sites/default/files/documents/an-82_tinyswitch-4_family_design_guide.pdf 

• https://piexpertonline.power.com/piexpert/design/select?share=7de59d9ba8dd76122c05f77c6eb614093cf83128617118e8c6539140d7264e63