CCM boost inductor design

Single inductor progressive wound for 500W PFC is standard

Right, I've seen single coils used in PC power supplies, at least, up to

750 watts I think so it's a bit puzzling as to why need to do something much different, unless there are very rigid full-load efficiency requirements we don't know about. what does "low loss" mean. 80-85% efficiency is probably standard for a good-quality 500 watt PC PSU.

Oh, I read down looks like OP wants his design to not use electrolytic capacitors. That clears things up a bit. and also, damn son.

Math is oK when used with SPICE and Breadboarding. If you need high effici ency, then you need many loops of the three magic steps. (MSB) This will re duce the L to about 300uF. At 150KHz your Kool-Mu will be hot-Mu and MPP wi ll be better but any good Ferrite (3F3) tops all. As the power goes up and F goes down, you can drop back to Kool-Mu, (2 stacked donuts.) is a good ch oice, and save money. 150KHz may be difficult for MOSFETs and magnetics. Si C MOSFETs may be needed but the diode must always be SiC. The inductor construction is tricky, gap the center post and outside walls equally. Do not go to three layers! JL, there are some operating points that Kool-Mu cannot touch MPP. Cheers, Harry D.

Hi Piotr, Normally CCM

He found an awesome Vishay 50uF 900V film cap. 500W at 600V is 0.83A, drawing the 50uF down by 0.1 volt in 6us. And with its 4-m-ohm esr, the switched-current ripple is only 33mV, who needs an electrolytic?

a bit. and also, damn son.

--
 Thanks, 
    - Win

Doesn't a PFC booster need milliseconds of holdup, as the AC line crosses zero?

If it's driving a downstream forward converter or something, a lot of ripple might be tolerable. But not too much.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Sure, but mpp is expensive.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Holdup is for the situation when the AC stays zero for a predefined time. Typically one line cycle in the case of servers, to allow them to save critical data (which doesn't happen, anyway...). In this case this application t_holdup=0, as there will be a battery switchover. The capacitor is only to provide a reasonable ripple value. I have assumed deltaV of 60V, which is just 10% of the 600V V_BUS. The downstream LLC will have no problems with that.

Best regards, Piotr

Just the losses. It is easy to wind the inductor if you don't care much about them.

There are, and this could be inferred from the thermal requirements. And you are right, the peak efficiency is expected at the full load and high line, not in the usual middle of the curve. For exactly the same reason.

The goal here is 95% end-to-end, including the LLC stage. This makes things quite interesting. :-)

Best regards, Piotr

This is for CCM with deltaB=30mT or so. The manufacturer's design tool as well as the Steinmetz coefficients for the material bolted into a Matlab script consistently report core losses of about 1W. Winding losses are higher, but even that bumps the temperature up by at most

35 degrees for the worst design option. It is estimated to be 25.6 deg in the case I am interested in (Core_loss=1.07W, Winding=2.23W, deltaB=25.3mT). Not much to save already, a lot to spoil winding it improperly.

It is extremely stable, but its saturation properties are disappointing.

Good ferrite is 3C95, used elsewhere in the converter. The main transformer is (present tense, as it has been prototyped) wound on an E43 planar core for its tremendous area to volume ratio. And the

40uH resonant inductor is also magnetically integrated within the structure. Beauty, I'll show it to you later.

This is also an option worth considering, thanks Bitrex, BTW.

This is going to be an all-SiC design, based on 6xC3M0065090J. And there will be no diode, I have always been a big fan of synchronous rectification. SiC would be required in the totem-pole topology anyway, so there are many reasons to go that way.

Yes, this is my biggest concern.

Best regards, Piotr

Right, but the low-load region is not a big concern in this application. I can live happily with DCM or frequency-clamped BCM there. Or switch the main converter altogether, as I have a 50W auxiliary PSU there.

Best regards, Piotr

Hearing this from you is a huge reward.

In fact, the entire converter is designed around this cap. The "I am what I am, find a way of using me" LLC transformer is another such a place. The bottom-up approach sometimes pays off.

Best regards, Piotr

Is that the one you designed with an intrinsic series-resonating inductor?

Its sometimes a bit embarrassing to admit it, but often finding an available capable component can be the foundation of a push-the-limits design.

--
 Thanks, 
    - Win

The AC line around here crosses zero 120 times a second! That's what I was referring to.

60v p-p ripple sounds about right. If there's a downstream switcher, its input impedance will be negative so the ripple is exponential in the downward direction.

"Things don't go to hell in a straight line."

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

I guess there is a concern for the heat getting out of inner windings. The path through the copper is long.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

PFC stage efficiency around 99% is standard:

Sorry for the brief post, busy days

Cheers

Klaus

Maybe you should rather say it's a standard goal for a manufacturer showing off exceptional performance, such as the one in the link.

But I wonder what real-world "standard" values are for power supplies we generally encounter, for example in a 500-watt PC power supply. This brings up the issue that it's not easy to make accurate measurements of AC-in DC-out losses, especially down at the 1% level. DC-in DC-out, yes, but PFC boost converters, no, SFAICT. The Institute's electronics-engineering lab is well equipped, but I currently cannot be sure of any high crest-factor AC-power measurements, to better than 1% to 2%.

For that matter, can we trust Infineon's data, 229.6 volts AC, 4.431 amps AC = 1014.9 watts, e.g., to the 0.01% level, for a 98.198% result (PFC boost converter design guide, page 20), without any indication of how it was measured? The very fact they give the result to 0.001% is an indication of careless error-bar evaluation.

OK, one note mentions Yokogawa's WT330 meter, spec: 0.1% of reading + 0.1% of range (300V), which is 229 +/- 0.529 volts = 0.23% accuracy. Hmm, it'd be nice to have one of those, but we're still talking 0.25% not 0.1% certainty. That's a 25% error at the 1% loss level.

--
 Thanks, 
    - Win