active PFC input filter

Also here is a pic of the input current to the PFC stage, without using an input filter before the PFC stage:

I think the PFC algorithm is possibly incorrect as there is a large variance in the current ripple.

Any idea how to smooth this current out or what part of the algorithm could use adjustment?

cheers, Jamie

schematic:

More stages of filtering may be the way to go. You are going to need an EMI filter before the bridge to kill the harmonics the diodes create so why not use a PI filter there to help the ripple reduction.

If you want to examine ripple at the conversion frequency, you're going to have to look at much shorter duration periods at different input LF phase angles.

This looks like a model's output. If so, it's only sensible to talk about the model, and not about an actual circuit. They will have widely varying causes for perceived problems.

RL

schematic:

Would a common mode choke across the two AC inputs before the bridge rectifier be good to use as well?

cheers, Jamie

schematic:

Hi,

I made a test PI filter in ltspice, it lets about 60mA of 300kHz current ripple back to the AC source (V1 and V2 are 240VAC splitphase), any suggestions on how to improve this filter, or is this a good configuration to use?

The cap before the first inductor, L1, doesn't seem to really do much in the simulation, what is the reason for using a PI filter on the AC lines rather than just an LC?

The right side of the schematic leads to the multiphase PFC stage. The ripple is 300kHz as there are 3 100kHz boost circuits in parallel, offset by 1/3rd.

cheers, Jamie

"Jamie Morken" wrote in message news:tDSLj.171635$pM4.116965@pd7urf1no...

schematic:

Jamie, Jamie, do you have good medical insurance? I worry about you and my bottle of tequila. Your always playing in high voltage with both hands. Filters have to do with input and output impedance over the frequency range of interest. Your poor C4 is in parallel with V1+V2 that have a Zout of maybe 1mR. For C4 to be of any worth it's Z must be much lower. In normal testing this unit will be plugged into a LISN that looks like 50R at 200KHz. To do any reasonable simulation you must add the LISN and line Zo to your simulation for both PFC and CE (Conducted Emissions). If done properly you will end up with another inductor between V1 and C4. As you increase the size of C4+C5+C3 you are reducing the power factor because these components draw current that is phase shifted. C3 must be split into 3 caps, one for each phase and placed close to the switching FET to reduce large current loops. A max value for each cap is around 3.3uF for C4 and C5 (Special X caps) and maybe 1.0uF for each C3. Now increase the three inductors until proper attenuation is attained. Good idea to split the inductors into both sides of the line (balanced), four inductors total. Dump L5. Now if this filter has to pass PFC and CE you must make sure there are no large gain peaks at the 5, 7, +9 harmonic of the line frequency. Add D-Qing R+C to fix. Now that the DM (Differential Mode) is filtered add the CM (common mode) section. Where the hell is Genome, he normally handles this rookie s**t. Got to go watch the sunset and drink some tequila. Harry

schematic:

Hi,

What type of filter would be good for a 3phase input source (rather than

I was thinking just series inductors with caps like this:

I don't have the 3phase common available so I can't put caps to that.

cheers, Jamie

schematic:

The leakage inductance of a common mode choke may help reduce the switcher ripple. Other than that they would be of little help for this situation.

schematic:

LTSpice assumes a zero impedance voltage source. That isn't the case in real life. Power wiring looks like a messy RLC circuit. At low frequencies it has impedance levels in the 0.1 to 10 Ohm range.

That sounds like it should be fairly easy to stomp the ripple from down to reasonable levels. You may need film capacitors to get enough capacitance in real parts but a few stages of a few uF combined with a few uH and some lossiness should do the trick.

Remember once you make RF power it has to go somewhere.