LNK3206 problem with noise
We have made the design at LNK3206G. It’s works but there's a ringing noise of coil. What do you think why we getting this noise?
The oscillogram at the source of the field-effect transistor indicates that the frequency is about 66 kHz.
The scheme is attached.
Comments
We have made waveforms at the source of the transistor. Please, check it.
The frequincy is approximetly 8kHz. Pulse duration - 1μs. The noise is like peep and it's quite loud.
Also check the updated schematic. R4 is not soldered. L2 = 500 μH. If change L2 at 1200 μH then the frequiency will be 5 kHz.
What will we do with noise problem?
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| Screen Shot 04-11-17 at 12.25 PM.PNG (57.95 KB) | 57.95 KB |
Any feedback?
Hello TALLmen,
If i understand your test setup right. your input voltage is 220VAC. where did you measure the waveform, the source to output RTN? the transistor you mentioned is Q1 or the transistor inside Link3206 which means the source pin of the IC. I asked this because the voltage is only 35-40V at your source pin which is too small to me.
By the way, how much is the output voltage and Output current when you have this issue. does this happen at all load conditions
For the inductance, 500uH may be too low at high line. the on time of your pulses will be very small and deliver little power. You can run our PIxls tool to check how much the inductance should be for your required output current. below is the link.
https://piexpertonline.power.com/site/login
When you mentioned the coil is noisy, did you mean it was L2. Is this coil the varnished one, if not, can you varnish it and try to see if it is audible or not.
Best Regards
We measuared waveforms at the pin S of Pi's chip.
Why do you think that the voltage is 30-40V? the each cell on the waveforms is 50V. Do the amplitude is around 300V.
Output voltage 5V and current - 150 mA, as we want. So, the power supply is working, but we have the problem with noise.
In this design we have use the following coil: http://katalog.we-online.de/en/pbs/WE-PD2-HV/768775312?m=n&sp=http%3A%2F%2Fwww.we-online.de%2Fweb%2Fen%2Felectronic_components%2Fsearchpage_PBS.php%3Fsearch%3D768775312&_ga=1.116168207.88973866.1484046384
Hello TALLmen,
In the screenshot of the waveform, it shows 5V/div. That's where the confusions come.
The inductor you share has 280mA saturation current. LNK 3206's current limit is higher than 482mA. it is very possible that the inductor will be saturated. it is recommended to use the inductor whose saturation current is higher than 600mA with LNK3206.
From the datasheet of the inductor you share, it is hard to tell if it is varnished or not. you may need to contact the manufactory to check if it is varnished or not. if possible, you can also varnish it and check if it helps.
if your output current is 150mA, it is also recommended to use LNK3205 for the cost reduction consideration. In this way you can use a smaller inductor as the current rating can be lower(>500mA is OK). it will also help the audible performance as the swicthing frequency will increase with the low current limit.
Best Regards
Hello TALLmen,
Thank you very much for interested in using Power Integrations product.
When you mention the ringing noise at the source of your transistor, how much is it. Did you have any waveform to share. Is it voltage related or current reaated when you observed.
Can you share the BOM of your input side circuit especially for those components at the transistor.
Best Regards
Jia