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Power Factor Control with DC input

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coppice:

--- Quote from: schmitt trigger on July 05, 2020, 10:57:13 pm ---Awesome investigation, thanks!

We can all assume that a PFC front end would work with a DC input......but someone had to verify that this particular assumption is correct.

--- End quote ---
We can all assume everything is OK with all products based on some very limited testing someone did? I hope you don't work professionally as an engineer with that kind of thinking.

nuclearcat:

--- Quote from: coppice on July 06, 2020, 11:47:26 am ---
--- Quote from: schmitt trigger on July 05, 2020, 10:57:13 pm ---Awesome investigation, thanks!

We can all assume that a PFC front end would work with a DC input......but someone had to verify that this particular assumption is correct.

--- End quote ---
We can all assume everything is OK with all products based on some very limited testing someone did? I hope you don't work professionally as an engineer with that kind of thinking.

--- End quote ---
I think he meant if magic smoke didn't escaped, it is time to test how well it works. If i will manage to find time for this, i might test too, with thermal camera and etc.
And quite interesting topic, as country where i am living now plunging in darkness, some % of efficiency saved by using direct DC power to AC power supplies will be helpful (if that possible).
Yes it might require some hacks or adjustments, and this is what i am desperate to see here.

schmitt trigger:
Thanks nuclearcat that’s what I intended to mean. That limited testing allows us to be guardedly optimistic.

But Coppice has to be its grumpy self and make disparaging comments, otherwise he is not happy.

Circlotron:

--- Quote from: NiHaoMike on July 02, 2020, 12:33:14 am ---If it's specified for 100-240V AC, it almost certainly will work on 140-380V or so DC.

--- End quote ---
One would think so. I've run my Rigol DS2072 scope many times on DC. It does not have PFC. I have a 12V to 240V "modified sinewave"  :palm: inverter and the sharp rising edges of it's output cause extra losses in the inverter because they are feeding into X caps in the scope psu. So I made an external bridge rectifier to go between the inverter and scope. Runs for quite a long time on a 12V 7Ah battery. Was using it to probe car electronics while driving around. (I was in the passenger seat).

ocset:
With 360VDC output, it sounds as if its a bit low, because PFC output are usually at least 385VDC.
With the low efficiency, it could be worth scoping the gate drive to see if a proper gate drive voltage is there.
Mind you, old fashioned CCM PFCs were  inefficient due to reverse recovery losses in the old slower diodes.
At low volts dc input, it could also be worth scoping the sense resistor, because maybe its in some bursting type operation with  very high rms current.
Changing the diode to a sic type, and then reducing the ohms value of the series gate resistor could result in efficiency improvement....the older  pfc's which used slower diodes, used to switch the fet on very slowly so as not to over-excite reverse recovery...this resulted in inefficiency in itself but had to be done to avoid the mega inefficiency of severe reverse recovery of the slow old diodes.

If you look at eg HiperPFS series of pfc controllers, they can get 90%+ efficiency with use of more modern  diodes.

Of course, BCM PFCs dont excite  the reverse recovery, but they can have very high fsw at light load...resulting in high  switching losses

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