Making my contribution in good manner, since my friend complains me that i don't contribute much, so here it is.
To make a reliable PFC.
1. You need a good inductor which should not saturate at the worst possible RMS INDUCTOR current. In other words, the required inductance at that current must not fall, otherwise PFC will get damage and its very dangerous situation when working with live mains.
2. The Boost diode must be chosen carefully which is based on many variables such as frequency of operation, if PFC is CCM, then the fast recovery is always the priority, start from anything under 50nS and do look for D=0.3 i.e. 30% current rating vs temp in datasheet, it must pass the worst peak ripple current the boost diode needs to charge the capacitor at low line conditions i.e. 90VAC.
3. The Bulk capacitor, it should be of low ESR and must have adequate ripple carrying capacity for HF + LF currents, otherwise it will heat up when loading the PFC at full load. Fire works can occur.
4. The Switch, either MOSFET or IGBT should be chosen, again depending upon the frequency of operation. Generation 5 IGBTS are good upto 75KHZ and above that always use a MOSFET, but its costly affair.
5. Next main thing to consider is controller feedback resistor dielectric value, always try to use feedback resistors in series config, for eg if the feedback R value is 1Mohm, use 5 X 200k in order to ensure high enough dielectric capability and avoid any aging effects.
6. Always use tightly coupled short PCB traces between Inductor out, Mosfet/IGBT Drain/Collector and Boost diode anode, in order to ensure low spiky behavior.
7. Always use source terminal or emitter terminal of switch involved as STAR GND Terminal and make star connection of bulk capacitor return to this point only, this makes it easier for the PFC to handle transients.
8. Its always a good practice to pre charge bulk caps via series resistor/ NTC before enabling the PFC chip to perform boost operation via Switch.
9. For Aux Supply, its help ful to use secondary winding on PFC inductor to get a separate voltage to power up the chip at full loading. You can use the standard ratio of NP/NS=Vp/Vs, where Vp is PFC output voltage and NP is inductor turns. You can choose Vs around 20-30 and post regulate it for 15V operation.
Still to come..............stay tuned.
Kanwar
To make a reliable PFC.
1. You need a good inductor which should not saturate at the worst possible RMS INDUCTOR current. In other words, the required inductance at that current must not fall, otherwise PFC will get damage and its very dangerous situation when working with live mains.
2. The Boost diode must be chosen carefully which is based on many variables such as frequency of operation, if PFC is CCM, then the fast recovery is always the priority, start from anything under 50nS and do look for D=0.3 i.e. 30% current rating vs temp in datasheet, it must pass the worst peak ripple current the boost diode needs to charge the capacitor at low line conditions i.e. 90VAC.
3. The Bulk capacitor, it should be of low ESR and must have adequate ripple carrying capacity for HF + LF currents, otherwise it will heat up when loading the PFC at full load. Fire works can occur.
4. The Switch, either MOSFET or IGBT should be chosen, again depending upon the frequency of operation. Generation 5 IGBTS are good upto 75KHZ and above that always use a MOSFET, but its costly affair.
5. Next main thing to consider is controller feedback resistor dielectric value, always try to use feedback resistors in series config, for eg if the feedback R value is 1Mohm, use 5 X 200k in order to ensure high enough dielectric capability and avoid any aging effects.
6. Always use tightly coupled short PCB traces between Inductor out, Mosfet/IGBT Drain/Collector and Boost diode anode, in order to ensure low spiky behavior.
7. Always use source terminal or emitter terminal of switch involved as STAR GND Terminal and make star connection of bulk capacitor return to this point only, this makes it easier for the PFC to handle transients.
8. Its always a good practice to pre charge bulk caps via series resistor/ NTC before enabling the PFC chip to perform boost operation via Switch.
9. For Aux Supply, its help ful to use secondary winding on PFC inductor to get a separate voltage to power up the chip at full loading. You can use the standard ratio of NP/NS=Vp/Vs, where Vp is PFC output voltage and NP is inductor turns. You can choose Vs around 20-30 and post regulate it for 15V operation.
Still to come..............stay tuned.
Kanwar
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