Hiper Current limit
I am using a Hiper Supply to generate 190V DC.
I am using that to PWM and create a 115 VAC 60 HZ supply.
Included is current scan.
I have decrease R59 to .05 ohms.
This is since my output wave form is AC so the current peaks at one point.
I would like to reduce the current limit resistor further.
This is because I am likely to be driving non PFC loads to my load current will be even more peaky.
How low can I make R59?
The current waveforms shown are the max current before the DC rail drops due to LLC current limit.
Comments
What is your input voltage? 115 VAC 400 HZ
Is R59 the current sense resistor? Yes,.05 ohms
What is your minimum input voltage? 100 VAC 400 HZ
I made R59 .03 Ohms from experimental results. I am including scans from max load of 230 W. The main MOSFETS get to 60 C with the small heatsinks used on RDR-189.
I would like to implement a wattage limit in software.
I can do that in one 16 ms cycle. Or maybe 48 ms for some noise filter.
Would that be soon enough.
My unit may be hooked up to a power corrected load.
Then I would need to override the R59 limit in software at 230 watts.
Your scope shots show >1.2 kW peak at the peaks of the output AC sinusoid. That means something like 13A pk at the LLC primary and so ~.03 ohms makes sense (which translates to ~16A current limit).
An additional timed overpower limit at a lower peak power setting than what the current limit allows the LLC to deliver is a great idea. It will protect the PSU from overheating.
I have a general question about your architecture. Do you need the PFC output to be 380V? If the AC input voltage is single range 115VAC then the PFC will be more efficient if you re-design it for 190V output. The LLC efficiency will be about the same if you change to 300V MOSFETs and re-design the primary to have half the turns and with Litz with 2x the strands.
A 190 V output sounds good if it means better efficiency. How much better. I am unsure about doing that because I have had such a hard time getting any vendor other than Santronics to produce a LLC transformer.
The PFC efficiency will increase by something like 2%. The heat savings will be in the PFC MOSFET, which you can change to 300V rated. Your bulk cap and PFC diode ratings will also change.
What is your input voltage?
Is R59 the current sense resistor?
What is your minimum input voltage?
What you are doing is to increase the peak power capability of the LLC in order to deliver the instantaneous peak power at the peak of the output sine wave.
You can play with the spreadsheet and put in the peak power that you need, and examine the peak primary current necessary to deliver this peak power at minimum input voltage. From this you can calculate the value of R59.
If you just reduce the value, you will need to examine the LLC waveforms at the peak of the output of the sinusoid, at minimum input voltage and make sure that you still get ZVS operation, and that the main MOSFETs don't overheat.