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I have attached inductor current waveform of PFC boost converter. After the particular current level, an undesired peak is coming. I have done some study and thinking it might be because of inductor saturation but not sure.

PFC boost converter current waveform PFC boost converter current waveform 2

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  • \$\begingroup\$ In a PFC the inductor current should (usually) follow a rectified sine (which is the reference derived from the like voltage.) However, if the line voltage itself is distorted the inductor current would try to follow that as well. So I would check the line voltage reference right at the IC. I see no indication that the inductor is close to saturation in the expanded waveforms, though I would not expect to see so much rounding of the current. I think that's due to measurement effects though. \$\endgroup\$ – John D Jul 9 '18 at 14:30
  • \$\begingroup\$ I think you might be right about the inductor saturating. What does the spec say? \$\endgroup\$ – Cristobol Polychronopolis Jul 9 '18 at 15:40
  • \$\begingroup\$ Sir, line voltage is sinusoidal. Measurement is also good. during light load condition current nature is good but when I am applying a moderate load, current nature is distorted. \$\endgroup\$ – vck Jul 10 '18 at 8:22
  • \$\begingroup\$ Sir, specs of what? \$\endgroup\$ – vck Jul 10 '18 at 8:22
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I observed same behaviour in interleaved PFC controlled by MCU. At higher load same peaks at coils currents affect the line current. Higher Proportional value of current loop controller help slightly together with some feedforward shape which help current controllers performance. Some people have similar problem with TI pfc IC, but there was the problem with some clamping of internal structure - the solution was to decrease shunt value.

oscilloscope trace

(Image source: TI E2E forum topic: UCC28180: UCC28180 PFC : distorsion of the PFC coil current [sic])

But in my case the shunt voltage after amplification with OPAMP is far from ADC max 3.3V. My current scale is 8Amps and issue is at 3-4Amp

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In general: A boost converter is a kind of switching regulator, where a current flowing through a coil is switched on and off. This switching action causes very abrupt current change which results in very high coil voltage (V=L*dI/dt).

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  • \$\begingroup\$ Sir, But it should follow sine waveshape. \$\endgroup\$ – vck Jul 9 '18 at 13:11
  • \$\begingroup\$ What should follow sine waveshape? Why do you expect this? \$\endgroup\$ – Stefan Wyss Jul 9 '18 at 20:09
  • \$\begingroup\$ because implemented topology is the average current mode control. \$\endgroup\$ – vck Jul 10 '18 at 8:18

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