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Power Management ICs Forum Discussions

KUOWENYUNG
Level 3
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Level 3

Hello IFXer,

Do you know how to calculate the the RMS current of MOSFET for CCM PFC? 

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1 Solution
SC
Moderator
Moderator 10 likes received 25 replies posted 10 solutions authored
Moderator

Hi,
Thanks for posting at Infineon Community.
Please refer to page No. 12 in the below reference application note.
https://www.infineon.com/dgdl/InfineonApplicationNote_PFCCCMBoostConverterDesignGuide-AN-v02_00-EN.p... 

Steps to Derive FET RMS Current.
1. Calculate Duty Cycle for PFC CCM Mode (Below shown final result)

D = 1-VIN/VO

2. Calculate Inductor RMS Current (Below shown final result)

ILRMS = (PO/VRMS X ƞ)

3. RMS current during one switching period can be calculated using below formula

IQRMS = ILRMS X √D

Since all quantities are a function of wt due to sin input. The above equation can be written as below.

IQRMS (ωt) = ILRMS (ωt) X √D(ωt)

By substituting, step 1 and 2 into 3 below equation can be derived

IQRMS (ωt) = ((√2 X PO |sinωt|)/(VRMS X ƞ) X (√1-(√2 X VRMS X |sinωt|)/VO)

4. By Integrating mean square value of the above equation we can get the resultant FET RMS equation as below

SPCH_1-1658293290989.png

Note: PF Considered as 1

Thanks,

SPCH.

 

 

 

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1 Reply
SC
Moderator
Moderator 10 likes received 25 replies posted 10 solutions authored
Moderator

Hi,
Thanks for posting at Infineon Community.
Please refer to page No. 12 in the below reference application note.
https://www.infineon.com/dgdl/InfineonApplicationNote_PFCCCMBoostConverterDesignGuide-AN-v02_00-EN.p... 

Steps to Derive FET RMS Current.
1. Calculate Duty Cycle for PFC CCM Mode (Below shown final result)

D = 1-VIN/VO

2. Calculate Inductor RMS Current (Below shown final result)

ILRMS = (PO/VRMS X ƞ)

3. RMS current during one switching period can be calculated using below formula

IQRMS = ILRMS X √D

Since all quantities are a function of wt due to sin input. The above equation can be written as below.

IQRMS (ωt) = ILRMS (ωt) X √D(ωt)

By substituting, step 1 and 2 into 3 below equation can be derived

IQRMS (ωt) = ((√2 X PO |sinωt|)/(VRMS X ƞ) X (√1-(√2 X VRMS X |sinωt|)/VO)

4. By Integrating mean square value of the above equation we can get the resultant FET RMS equation as below

SPCH_1-1658293290989.png

Note: PF Considered as 1

Thanks,

SPCH.