How to check a inductor waveform?

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I have uploaded circuit diagram of my current driver. It's working well.

I have select inductor core and turn according to PIXI software.But how can I confirm that it really fits with my driver.

How can I know that my inductor is not saturating using oscilloscope.?
Where should I set probe of oscilloscope to measure it ?

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Circuit Diagram.png170 KB

Very good you are able to power-up the unit easily. Use a current probe in series with the drain in order to verify the inductor current using oscilloscope. Adjust the time scale to see the switching current. The switching current shoud be a linear ramp, no exponential rise to say it is not saturating. Apply a heatgun to increase core temperature to around 130 degree celcius to verify the worst condition. Monitor the drain current during start-up also.


Thanks for your answer. I have checked current waveform. it is showing liner graph.

I had join 2M + 2M + 2M (6M) between filtered ac and feedback to get better THD.
But some of your new circuit diagrams use 10nF + 2.7M .
Let me know which option would be better for THD improvement.

Many of your driver example does not contain 5mH EMI filter choke.
Do you recommended EMI filter choke for outdoor application ?
Is there any extra protection required for indian outdoor application ?

Oh! Looks like you know how to trick the IC, you are creative. Having a capacitor and a resistor to FB pin from filtered AC (+) will make it possible to detect the shorted output. Adding a 6M only will level shift the FB and then mask the shorted output detection.

Trick to further improve the THD is by further increasing the power inductance.

Most of our design was able to meet the standards without the additional CMC filter but sometimes the system application might need to add. It depends on how it is cased-up and connected to the load. I would recommend to add an optional filter if you have space then delete it during EMI testing. At least you have a back-up in case it will be marginal.


According to PIXI my driver THD would be 24.2%. But PIXI does not compile my 330uF 100V Capacitor and 2M+10nF path for decreasing THD.

How can I measure THD in my driver using multimeter/oscilloscope ?
I read somewhere that you can find THD by ratio of DC output Voltage / AC output voltage using multimeter.
Is it really right way to measure it ?

I also know that big inductor core is used to get lower THD.
But Can I use big capacitor to decrease THD ?

PIXL will calculate the THD based from the input current of after the EMI filter. Actual THD will be altered by the EMI filter.

THD measurement will depend on your application. Example,in audio application THD is measured in the output. It is because the end user is more interested in the quality of the sound. As for the power supply level, ampere THD is measured in the input of the power supply.

Please note that THD should be measured in a regulated AC source, not from regular AC outlet or VARIAC. The voltage THD should be less than 1% in order t o get the correct ampere THD.

For efficient working ( < 2 seconds), THD is measured from the a wattmeter. Use Yokogawa or Chroma wattmeter to calculate the THD for you. But then if you have ample time (>1 hr) then a digital oscilloscope can be used. Use FFT measurement to get the harmonic content to calculate the THD. Take the squareroot of sum of the square of 2nd to 33rd harmonic. And then divide to the fundamental harmonic.