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Power Management ICs Forum Discussions

monil9
Level 2
Level 2
First like received 5 sign-ins First solution authored

Dear sir,

i am designing 2KW PFC, when I give a load above 500W, it started humming noise from the converter.
also at 1300W, it's working fine long time up to 2 hours, but above 1300W it is going unstable and the VB_OK relay gets on-off and the output voltage going unstable.
here i am attaching input current waveforms with the following specs:
pout =1300W 
Vin = 220vac
Vdc_out = 390vdc
IC VCC = 13.7VDC
Rsense = 0.005Ohms (5mOhms)

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1 Solution
monil9
Level 2
Level 2
First like received 5 sign-ins First solution authored

thank you for your response
I got a solution by just putting the gate driver to MOSFET and the audible noise is gone, also got the very nice shape of the sine current at 2000W.



View solution in original post

4 Replies
Neo_Qin
Moderator
Moderator
Moderator
50 solutions authored 100 replies posted 100 sign-ins

Hi @monil9 ,

Give me some time to familiarize with these issues, I will update you later.

Regards,

Neo

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Neo_Qin
Moderator
Moderator
Moderator
50 solutions authored 100 replies posted 100 sign-ins

Hi @monil9 ,

1) Audible noise

Most susceptible to audible noise are usually MLC ceramic capacitors, inductors, or transformers. Magnetic components, such as inductors and transformers, are stressed by high-voltage pulses at frequencies that result in a physical effect, such as the reverse piezoelectric effect on the coil or magnetostriction on the core.

The mechanical self-resonant frequency (SRF) of these components must be addressed, since these vibrations are amplified many times at the resonant frequency. If you have located the component of the audible noise, it's recommended measure the mechanical SRF to see if it falls within the audible noise range,  and identify factors that contribute to this resonance.

Solutions such as changing the control strategy to avoid certain frequencies or changing the peak current can reduce audible noise. Changing the magnetic design to change the stiffness constant or the weight of the board or the construction of the coil can also mitigate noise. Together, one or several of these methods can be employed to eliminate or minimize audible noise in a power supply.

In a typical ICE3PCS01G application, the switching frequency will be set at about 65kHz. Maybe the 100~200Hz line frequency ripple dominated this behavior, try to change the filter parameters to see if this phenomenon is improved.

2)  Converter unstable when output above 1300W

In the current waveform you provided, the oscilloscope is configured as AC coupling, so I cannot get the peak voltage of Isence pin. However, the spike in the waveform can easily trigger the PCL protection, which may be further cause the output unstable.

Could you confirm the spectrum of these spikes? In most cases, they come from the high-speed switching of MOSFETs. You can appropriately increase the rise/fall slope of the MOSFET driver circuit and add filtering to the shunt resistor loop to see if the situation improves.

Neo_Qin_0-1673253970670.png

Regards,

Neo

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monil9
Level 2
Level 2
First like received 5 sign-ins First solution authored

thank you for your response
I got a solution by just putting the gate driver to MOSFET and the audible noise is gone, also got the very nice shape of the sine current at 2000W.



Neo_Qin
Moderator
Moderator
Moderator
50 solutions authored 100 replies posted 100 sign-ins

Hi @monil9 ,

Thanks for sharing your workaround, congratulations!

Thank you very much for making use of Infineon community support, we will be glad to work with you in the future as well.

Regards,

Neo

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