T
treez
Guest
Hello,
The NCL30001 controller implements an offline PFC’d single stage flyback converter. This operates in fixed frequency, and is intended for CCM.
The schematic for it involves only a FET source sense resistor. It does not include a current sensing resistor in the return path. As you know, the source sense resistor signal represents the Flyback FET current , and this is not the actual total current.
As you know, virtually all PFC Boost converter controllers involve a sense resistor which is actually in the return path. This is , obviously because in order to make the input current follow the input voltage (sinusoidal), its obviously necessary to sense the actual input current. If its not sensed, then we cannot know what it is.
As such, the PFC operation of the NCL30001 will have significant limitations over varying line and load. Would you agree? I am wondering if they have implemented some fantastic algorithm in the NCL30001 which somehow overcomes this? I very much doubt it, because if they have, then its “goodnight Vienna” to all the PFC controllers which comprise a current sense resistor in the return path. –Obviously, such a sense resistor breaks up the ground…it “splits” the ground, which is something which is of some level of inconvenience. If controllers existed which obviated the need for such a “ground-splitting” sense resistor, then all such controllers would die off overnight….since they have obviously not all dies off, I put forward that the NCL30001 has a level of inflexibility in its PFC operation…would you agree?
Certainly, all the app notes suggest correctly PFC’d operation only over a 2:1 output voltage range.
NCL30001 datasheet:
www.onsemi.com/pub/Collateral/NCL30001-D.PDF
The NCL30001 controller implements an offline PFC’d single stage flyback converter. This operates in fixed frequency, and is intended for CCM.
The schematic for it involves only a FET source sense resistor. It does not include a current sensing resistor in the return path. As you know, the source sense resistor signal represents the Flyback FET current , and this is not the actual total current.
As you know, virtually all PFC Boost converter controllers involve a sense resistor which is actually in the return path. This is , obviously because in order to make the input current follow the input voltage (sinusoidal), its obviously necessary to sense the actual input current. If its not sensed, then we cannot know what it is.
As such, the PFC operation of the NCL30001 will have significant limitations over varying line and load. Would you agree? I am wondering if they have implemented some fantastic algorithm in the NCL30001 which somehow overcomes this? I very much doubt it, because if they have, then its “goodnight Vienna” to all the PFC controllers which comprise a current sense resistor in the return path. –Obviously, such a sense resistor breaks up the ground…it “splits” the ground, which is something which is of some level of inconvenience. If controllers existed which obviated the need for such a “ground-splitting” sense resistor, then all such controllers would die off overnight….since they have obviously not all dies off, I put forward that the NCL30001 has a level of inflexibility in its PFC operation…would you agree?
Certainly, all the app notes suggest correctly PFC’d operation only over a 2:1 output voltage range.
NCL30001 datasheet:
www.onsemi.com/pub/Collateral/NCL30001-D.PDF