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Isolated Dual interleaved PFC'd Flyback controller IC

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treez

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Hello,
Do you know of an Dual interleaving controller IC for Isolated , PFC’d Flybacks? The load would be connected to the output of the dual PFC’d flybacks, which both pour their current into the same output.
I just searched st.com, ti.com, Infineon, fairchild, analog, mps, and onsemi but none of them do it.
I appreciate that such a topology would’nt usually make sense, but this is a particular case where it would be useful.
There are plenty of Dual interleaved Boost PFC IC’s, but these are generally not suitable for “hacking” into a useage with flybacks
One reason that Dual PFC’d boost PFC IC’s are not suitable for the said flyback useage, is their lack of suitable output overload protection, and lack of suitable output short circuit protection. The above two kind of follow from the fact that Boost PFCs don’t usually connect directly to the load, so for them , short circuit protection is not as relevant…..whereas PWM controllers that serve the load directly, need the typical timeout overload protection……this “timeout” overload protection does not exist in Dual interleaved Boost PFC chips.
Also, few of the Dual interleaved Boost PFC IC’s have suitable connection for a feedback optocoupler…….this could be hacked in, but not too conveniently.
Some of the Dual interleaved Boost PFC IC’s have very lax overcurrent protection….for example, the UCC28064A needs the overcurrent sense resistor to be set for at least twice the peak current of either of the Dual Boost stages…….this would be very poor if used with flybacks that are directly connected to the load… thinking of the high staircasing of primary current that would occur in the event of an output short circuit.

(i posted similar previously , but this time it is specific to the controller, so a different post if i may, specially since the post title will spring and invite incoming interest from google searchers, thus helping the forum with extra traffic)
 

FAN9611 is a good option - if no other power converters near ...
 
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Thanks, will look into the FAN9611.........But with reference to the UCC28064A Dual interleaved PFC controller...

We have just been looking into designing a Dual Interleaved Flyback PFC for VAC input = 115VAC, and vout = 220VDC, 120W with UCC28064A.
Its a Boost PFC chip, but we need flyback so are trying to hack it for flyback useage.

We have just seen on page 32 of the UCC28064A datasheet that we must set the overcurrent limit to more than twice the max peak current limit of each of the dual converters.

This is terrible…..usually its best to set the overcurrent limit to around 10-15% more than the max peak current level …so having to set it to more than twice the peak current level is terrible……..why have they set this chip up like this?......i appreciate that if we were using it in Boost PFC mode, then it wouldn’t be so bad, because the fets wouldn’t even get turned on if the current was already above the limit, but even then, twice the peak current level is really high. How has this chip even come onto the shelves? Allowing that much overcurrent is surely ridiculous.

The UCC28064A is not “peak current” mode, and not “average mode”…but instead it just has an “on-time setting”…(that depends on the RSET resistor value, the COMP pin voltage, and the VINAC voltage)
UCC28064A datasheet
https://www.ti.com/lit/ds/symlink/ucc28064a.pdf
 

yes it is terrible - this is why we have designed our own discrete resonant 2-phase controller for PFC & flyback ...

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also FAN9612
 
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Flybacks - especially 2 & 3 phase ( interleaved ) are quite popular up to 600W or so - minimum parts, low side gate drive, good power factor, pretty simple control, good efficiency if synch rect on the o/p - and low RFI if resonant (BCM, or CrCM ) ... and if you use a 1200V Si-C fet - very resistant to mains spikes ....
 
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But above 600W what else can you think of for isolated PFC?
 
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above 600W we use half bridge and full bridge resonant design for isolated PFC with various DC out

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up to 3kW ...
 

Never tried using a buck-derived topology (half/full bridge) for a PFC, sounds like getting good PF across a wide Vin range would be very tricky (assuming you're operating in CCM most of the time).
 

above 600W we use half bridge and full bridge resonant design for isolated PFC with various DC out

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up to 3kW ...

Wait let me be clear..you go straight from line or rectified line to isolated DC with half bridges or full bridges (I'll call this single stage isolated pfc)? Or do you have a boost PFC before using a half or full bridge for your isolated DC bus?


I was asking about possibilities for skipping the boost PFC as Treez is doing with the flyback.

Never tried using a buck-derived topology (half/full bridge) for a PFC, sounds like getting good PF across a wide Vin range would be very tricky (assuming you're operating in CCM most of the time).

Well like I said I can see it with Dual Active Bridge which is an anything-to-anything DC-DC voltage converter. It could be fed with rectified line line directly. I could also generally see 'buck derived topologies' running backwards since syncronous bucks look like boosts from the opposite direction.

You can see an example of that here:
https://www.infineon.com/dgdl/Infin...N.pdf?fileId=5546d46267354aa00167404c69bb7b8c

But I've never found literature on these in the context of PFC's.
 

Yes, single stage resonant half or full bridge to isolated DC out, 0.99 PF up to 3kW
 
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What other details are you willing to share about that?
 

We make them for emergency radio broadcast amps ( class D & E ) - minimum parts counts - so maximum reliability - they run off a generator nicely ( sine wave in ) and are very low RFI ( ZVS over full load range ) they are inherently current limited to about 1.5 x Io max - no electrolytics on the mains - so are designed to last for 25+ years - we do put significant electrolytics on the o/p to give 10mS ride thru and plenty of oomph for driving the loads peak I requirements.

Not patented - as we wanted to keep building them for many years without competition - since 1994 in fact. Now that we have 1200V SiC fets on the pri and big Si fets on the sec the efficiency for the synch rect o/p version is very high indeed ...

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We do a 3 phase version also - where the input is 400V ( 350 - 440Vac ) L-L for each of the 3 modules - giving up to 66V out at 120A for forklift charging ...

Soon to do an 180ADC one ....
 

And what’s the efficiency? Do you think it’s better or worse compared to a boost or totem pole pfc paired with an LLC or full bridge?
 
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hi there, we don't like quoting efficiencies to parties other than customers, lets just say - more heat comes off the magnetics than all the semi's - from 40 to 70 degC the fan power goes from 1W to 3W to keep everything below 95 degC on the mag's - the weight of the heatsinks is 150g for the standard 2.5kW version.
 
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We don't particularly like the DAB, too many bits, too many control bits, too tricky to get exact dead times over load and line ... the list goes on ...
 
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above 600W we use half bridge and full bridge resonant design for isolated PFC with various DC out

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up to 3kW ...

Resonant bridge, as in phase shifted full bridge or LLC? Hard to see how a standard PSFB could maintain ZVS with an AC input. What sort of duty cycle range is necessary to get a good PF?
 
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I did not mention phase shift at all ... there are many ways to skin a cat...
 
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Indeed, I'm guessing your operating mode changes throughout the mains cycle. Must use a high performance digital controller.
 
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