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# Vin RMS calculation in PFC stage of 3.3kW on board charger

## Vin RMS calculation in PFC stage of 3.3kW on board charger

Level 3
Level 3

Hi,

I have a doubt in  3.3kW PFC stage  in the given Infineon code for 3.3kW PFC demo board.  The VIN AC RMS voltage is calculation is done by using a digital filter . The Vin sensed ADC reading is  sampled at 30kHz.   The digital filter  function is called every 2.5kHz. The output of filter is considered as average AC voltage . This average voltage is multiplied with 1.111 to get  RMS  AC voltage.  I want to know the cutoff frequency  and  type of filter used.

Below the equation used in code  for filter.  g_U_in   is the ADC reading for Vin Ac sense.

1 Solution

## Re: Vin RMS calculation in PFC stage of 3.3kW on board charger

Moderator
Moderator

Hi Rakesh,

Sorry for the delay in responding. The equations you refer to are the back-to-back low pass filters. The filter factor used (ZK_UIN = T0/T = 1041) is defined in defines.h

http://techteach.no/simview/lowpass_filter/doc/filter_algorithm.pdf  you can refer to this.

Best regards,
Pranava
4 Replies

## Re: Vin RMS calculation in PFC stage of 3.3kW on board charger

Moderator
Moderator

Hi,

Can you please share the source code you are referring to?

Best regards,
Pranava
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## Re: Vin RMS calculation in PFC stage of 3.3kW on board charger

Level 3
Level 3

The source code is attached please check.

Level 3
Level 3

Hi,

Regards

RAKESH

## Re: Vin RMS calculation in PFC stage of 3.3kW on board charger

Moderator
Moderator

Hi Rakesh,

Sorry for the delay in responding. The equations you refer to are the back-to-back low pass filters. The filter factor used (ZK_UIN = T0/T = 1041) is defined in defines.h

http://techteach.no/simview/lowpass_filter/doc/filter_algorithm.pdf  you can refer to this.

Best regards,
Pranava