Other Parts Discussed in Thread: TL431,
When I'm checking the waveform on TL431, I have seen there is noise over there. Please suggest which component I need to focus so that I can remove noise in this circuit.
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Hi, Ravi:
Where did you measure this waveform? Is it reference pin?
Would you mind to measure this waveform again with shortest loop? Sometimes the noise comes from GND coupling.
If this noise comes from your output voltage, please adjust your output capacitance. It would be helpful to output ripple and noise.
Regards,
Wesley
Hi, Ravi:
Thanks for your information. So does this noise only show when you connect battery? and does it disappear and would not show during battery charging, is it correct?
If yes, I think this noise comes from capacitive current spike. Adding an inductance and resistance to be a filter may be helpful, but it impacts efficiency. Does this short noise impact any system operation or out of system specification? If it does not impact system, maybe you could ignore it.
Would you please share me the schematic and how you connect battery to let me understand more about your questions?
Regards,
Wesley
Hi, While connecting the 48V battery at load side my CC is working but still waveform looks unstable. To control the sudden spikes I've tried to increase the value of capacitor at controller side. i.e. FB and VS side. Kindly support for the same so that I can complete the task as soon as possible.
Your early response will be valuable for me.
Hello, Ravi:
Based on your waveform, it seems your feedback loop response is too slow to cause the oscillation.
You may try to modify compensation loop to speed up the loop response.
To increase Vs cap might impact VDS valley detection. It is not recommend to increase Vs cap a lot. And too big FB capacitance is also make slow response.
You may refer the application note shows above to know how to adjust UCC28740's feedback loop.
Regards,
Wesley
Hi, Ravi:
Please try to modify C24 and R50. You could try several different value to see how does it works
Regards,
Wesley
Hi,
In my design when I check the MOSFET (Vds=800V. Id=17A), Drain to Source overshoot it is going more than 848V at 280V AC Input(Img. attached). In my design I already added snubber circuit (20K/2W & C=2.2nF & 10nF (parallel connected)).
Testing condition: Input= 280V AC, Output Voltage : 58.4V, 6A (48V Battery connected at output side)
Same
condition 1: Increased 2.2nF capacitor to 10nF
Condition 2: Remove 2.2nF capacitor
In both conditions overshoot is same. Kindly suggest how I can reduce the overshoot spike.
Hi, Ravi:
Please refer the application note as below. page 8~page 9.
You may need to modify the Rsnub to reduce spike.
Regards,
Wesley