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zenerbjt
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HiperPFS Boost PFC controllers looks absolutely excellent, but just wish to first check it over..
Please advise on any of these questions….?
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1….TITLE: Setting of Brown in/out threshold depends on set value of vout for Boost PFC?
Hi,
From page 14 of the HiperPFS datasheet it appears (?) that if vout is not set to 385VDC, then the divider to the voltage monitor pin needs adjusting and then this is said to mean a different Brown in and Brown out threshold.
Is this correct? How has the setting of the brown in/brown out threshold got mixed up with the setting of the output voltage?
HiperPFS datasheet:
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2…..TITLE: Max possible Vout of Boost PFC?
Hi
Page 13 of HiperPFS 3 datasheet states that vout of the Boost PFC should never be set to >395V. It is said that there would be a danger of overvoltaging the internal FET during mains transients or load transients
HiperPFS datasheet:
..However, the abs max drain source voltage of the internal FET is 530V. There is a huge output capacitor of at least 100uF on the output of the Boost PFC. So there is no chance of the internal FET getting overvoltaged, even during line and load transients.
So why can we not make the vout say 400V?
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3…..TITLE: Snubber capacitor to safeguard HiperPFS B(Vdss) of 530V?
Hi,
Page 18 of the HiperPFS Boost PFC controller datasheet says that a 33-100pF capacitor should be connected across the Boost PFC diode in order to prevent the internal FET’s B(Vdss) of 530V from being breached.
Page 18 says that the 530V level is most likely to be breached during heavy loading of the Boost output to almost the overload level.
How can such a capacitor be of any use? Surely it would just create more circuit noise due to high di/dt as such a snubber capacitor gets rapidly charged/discharged?
How could the drain of the internal FET go up to 530V?....As soon as the drain voltage goes above Vout then the Boost diode will clamp the drain voltage to vout…..which wouldn’t get anywhere near 530V.
The only way the drain could get up to 530V would be due to PCB trace stray inductance…but this should be minimised with tight layout and having a small value ceramic cap right at the internal boost diode cathode going down to the controller’s star ground point with the power ground.
HiperPFS datasheet:
********************-------------------------******************
4……TITLE: PFC controller uses voltage divider resistors of too high value?…moisture problem?
Hi,
Page 12 of the HiperPFS Boost PFC controller datasheet shows dividers being used for Vout regulation, and also for VAC input detection for Brown in/out monitoring and Input OV detection. The upper resistance of these dividers is greater than 15 MegOhms. This surely is way too high? Slight moisture on these resistors will surely result in false tripping of Input overvoltage detection and poor vout regulation?
HiperPFS datasheet:
******************----------------------------************************
5 TITLE: Why isnt everybody using HiperPFS-3?
HiperPFS-3 gives you boost fet and diode and controller on a single chip, no sense resistor needed, Error amplifier changes dynamics as vout goes outside nominal in order to preserve the output voltage and improve vout regulation…..why is the HiperPFS not the defacto “go-to” chip for Boost PFC today?
HiperPFS datasheet:
Please advise on any of these questions….?
******************----------------------------****************************
1….TITLE: Setting of Brown in/out threshold depends on set value of vout for Boost PFC?
Hi,
From page 14 of the HiperPFS datasheet it appears (?) that if vout is not set to 385VDC, then the divider to the voltage monitor pin needs adjusting and then this is said to mean a different Brown in and Brown out threshold.
Is this correct? How has the setting of the brown in/brown out threshold got mixed up with the setting of the output voltage?
HiperPFS datasheet:
******************----------------------------****************************
2…..TITLE: Max possible Vout of Boost PFC?
Hi
Page 13 of HiperPFS 3 datasheet states that vout of the Boost PFC should never be set to >395V. It is said that there would be a danger of overvoltaging the internal FET during mains transients or load transients
HiperPFS datasheet:
..However, the abs max drain source voltage of the internal FET is 530V. There is a huge output capacitor of at least 100uF on the output of the Boost PFC. So there is no chance of the internal FET getting overvoltaged, even during line and load transients.
So why can we not make the vout say 400V?
*************************---------------------**************************
3…..TITLE: Snubber capacitor to safeguard HiperPFS B(Vdss) of 530V?
Hi,
Page 18 of the HiperPFS Boost PFC controller datasheet says that a 33-100pF capacitor should be connected across the Boost PFC diode in order to prevent the internal FET’s B(Vdss) of 530V from being breached.
Page 18 says that the 530V level is most likely to be breached during heavy loading of the Boost output to almost the overload level.
How can such a capacitor be of any use? Surely it would just create more circuit noise due to high di/dt as such a snubber capacitor gets rapidly charged/discharged?
How could the drain of the internal FET go up to 530V?....As soon as the drain voltage goes above Vout then the Boost diode will clamp the drain voltage to vout…..which wouldn’t get anywhere near 530V.
The only way the drain could get up to 530V would be due to PCB trace stray inductance…but this should be minimised with tight layout and having a small value ceramic cap right at the internal boost diode cathode going down to the controller’s star ground point with the power ground.
HiperPFS datasheet:
********************-------------------------******************
4……TITLE: PFC controller uses voltage divider resistors of too high value?…moisture problem?
Hi,
Page 12 of the HiperPFS Boost PFC controller datasheet shows dividers being used for Vout regulation, and also for VAC input detection for Brown in/out monitoring and Input OV detection. The upper resistance of these dividers is greater than 15 MegOhms. This surely is way too high? Slight moisture on these resistors will surely result in false tripping of Input overvoltage detection and poor vout regulation?
HiperPFS datasheet:
******************----------------------------************************
5 TITLE: Why isnt everybody using HiperPFS-3?
HiperPFS-3 gives you boost fet and diode and controller on a single chip, no sense resistor needed, Error amplifier changes dynamics as vout goes outside nominal in order to preserve the output voltage and improve vout regulation…..why is the HiperPFS not the defacto “go-to” chip for Boost PFC today?
HiperPFS datasheet:
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