Resonant SMPS using L6599

res_smps

New member
Hi' Res i see you got a good result. From what I see you are loading around 1140w and input sees 1760w that is around 60% eff. This may not be true as power factor tend to draw more current than what really is drawn from smps. You need to see the actual watts at the input with a watt meter. Above all regulation seem to hold well with only a 2v drop. Well done Res
Dear Silvio,

I think the meter on the input measures peak current, from this screenshot Pin = 1292W, Pout = 118*9.49 = 1119.82, the result is 86,4% eff
power measurement.jpg

maybe these results are also not really accurate, I just did a quick test, not comparing with my clampmeter / multimeter.
because my kids play around me, I don't want them to touch it
 

Silvio

Member
@ Res

For loads you can get some heating elements from old microwave ovens. These may have grill function and usually they have a couple of heating elements rated 450w at 120v. They are usually hooked up in series. These make very good loads. I also use halogen lamps to load my smps with them. You may have seen it in my videos. I make them switchable and they also double as a series load when testing pro amplifiers for current limit. Sometimes a 100 or 200w lamp in series with the mains supply is not enough to get it started so I use these instead inserting them gradually. I have 5 in all rated at 180w, 2x200w, 1 x 300w and 1 x 400w. Having 4 switches the first one is always connected but the other 4 are switched individually.

IMG_0357[1].jpg IMG_0372[1].JPG
1 SMPS 1000w with cpu heatsink PIC 2 showing switched halogen lamps
 

res_smps

New member
I ask you some questions. How does the smps behaves with no load and full load regarding regulation? I guess you need a minimum load. When I added regulation to my smps it needed this as with no load the trafo was ticking meaning switching on and off. Even so from a peak voltage of 80-0-80v I had to set for 60-0-60 as there was not enough headroom for regulation higher than this. Voltage drop in the output inductor and other losses etc.

If the smps is intended for audio than do not trouble yourself much about holding full power for a long time. This week I was testing my 1000w amplifier and adjusted it at full blast with the clip indicator showing slightly at times. The average wattage was around 200-250w drawn by the amplifier smps at the input. You see although the smps can give more than a 1000w the average is somewhat quite smaller. During my bench tests when I was testing my smps (I have a cpu heatsink attached to my mosfets and diodes) It could hold 900w continuous without any problems with a very moderate temperature rise of around 50 degrees and held to that temperature for half an hour.

I will reply this question by email because I will show some videos that I didn't upload on YouTube
 

res_smps

New member
This is the complete design of this SMPS including schematic and pcb layout in one pdf file
You can use it freely even for commercial, I can't prevent being copied and sold,
there are too many smps makers and sellers here (Indonesia) from very bad designs to very good ones, some of them just copied other design

transformer parameter
Np : 16T
Ns : 2x6T for +/- 70V
Lr 27uH
Lp 143uH
 

Attachments

  • L6599 V2 by res.pdf
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res_smps

New member
load test using a water heater
water heater.jpg
load with 1 heaters
Pin=401,6W Vout=138,4A Iout=2,62A Pout=362,608W Eff=90,29%
1 heater load.jpg
load with 2 heaters
Pin=818W Vout=138,5 Iout=5,43A Pout=752,055W Eff=91,94%
2 heater load.jpg
 
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MicrosiM

Administrator
Staff member
@Res


Very good results.

Could you please confirm the below points, because I am little confused?

In one of your videos, I saw that you have almost a sine wave shown on your oscilloscope. could you please clarify where did you measure exactly?
Did you use current probe?

This video

[video=youtube;y42T_Fw6fCs]https://www.youtube.com/watch?v=y42T_Fw6fCs[/video]


Could you please connect your oscilloscope at the SMPS + & - (AC Coupling) and show me what wave you have at the output in idle?

Thanks
 
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res_smps

New member
thank you Silvio
the efficiency is very good at over 90%
I hope this result is correct because I don't really trust the meter on the input.
while at the output I use constant 89 (voltmeter) and sanwa DCM400AD(clamp meter)
 
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res_smps

New member
Very good results.

Could you please confirm the below points, because I am little confused?

In one of your videos, I saw that you have almost a sine wave shown on your oscilloscope. could you please clarify where did you measure exactly?
Did you use current probe?

Thank you Microsim, I measure the voltage at resonant capacitor using voltage divider (1M and 10K if I remember correctly) then connect to my oscilloscope because my oscilloscope is only 80Vpp max
V_Cr.jpg

Could you please connect your oscilloscope at the SMPS + & - (AC Coupling) and show me what wave you have at the output in idle?
next time I'll do it for you
 

MicrosiM

Administrator
Staff member
@ Res

I am not sure if thats the reason for the semi sinusoidal waveform, in my case I have almost perfect sinusoidal wave form at the Cr without connecting any resistors to it (when the SMPS is loaded)


And thats another evidence that your SMPS is still not running where Fs = Fr, and it requires some perfect tuning.

Please post some pictures for the output of the SMPS in idle, AC coupling

Thanks
 
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iop95

New member
For LLC it's not mandatory to work at Fs = Fr only.
Below Fr it's a boost gain zone and above a buck gain.
Below Fr must check to not enter in capacitive mode (current lead voltage), losing ZVS with risks for MOSFETs.
 

MicrosiM

Administrator
Staff member
For LLC it's not mandatory to work at Fs = Fr only.
Below Fr it's a boost gain zone and above a buck gain.
Below Fr must check to not enter in capacitive mode (current lead voltage), losing ZVS with risks for MOSFETs.


Yes, that makes sense, but optimal point where Fs = Fr, thats my own opinion.

Thanks
 

res_smps

New member
the higher resonant frequency of my smps is 68kHz and the lower is around 30khz.
my smps works with 50khz to 90khz variable switching frequency

@microsim
sorry I'm out of town now can't do the test

@iop95
Do you have a method to check whether my smps is entering capacitive mode or not?

although my smps is good in load testing, I admit my smps is still not perfect, there are some things that still need to be fixed and improved :
- regulation with no load is still not smooth
- idle temperature of the transformer reaches 60C (30 minutes test)
- at heavy loads the resonant capacitor is very hot
 

iop95

New member
@res_smps
There are some calculations to check for entering in capacitive mode; I have a spreadsheet but need to translate in english... maybe in next days I can upload it.
- LLC is difficult to controll... transfer function is complex and have some non-linear elements, so may exhibit control problems at light loads/no load especially
- check core loses vs temperature... most of them have a minimum around 80-100ºC, so 60ºC may be not so bad if other requirments are not violated.
- need to check esr capacitor and current supported at working frequency range; may need to use more parallel/series caps to remain below limits and reduce cap losses (esr * Irms^2)
 

MicrosiM

Administrator
Staff member
@Res

That means your SMPS is not running properly, and I believe that you still have a lot of work to do.

Good luck
 

res_smps

New member
this is the waveform, i measured it using pcb V1 (post # 1)
https://drive.google.com/drive/folders/1UA6K-lK1vEmXdeSdycBP-v_4cYAZewmD
my oscilloscope is only dc coupling, so i added 100n capacitor in series with the probe
1. Vout with AC coupling, regulated, no load
2. VCresonant (Vcr), regulated, no load
3. Vcr, unregulated, no load, 100khz switching freq
4. Vout with AC coupling, unregulated, no load, 100khz switching freq
5. vcr, unregulated 69khz no load
6. vcr, unregulated 69khz 100 ohm load
7. vcr, unregulated 61khz no load vcr
8. vcr, unregulated 61khz 100 ohm load
 

res_smps

New member
This is the complete design of this SMPS including schematic and pcb layout in one pdf file
You can use it freely even for commercial, I can't prevent being copied and sold,
there are too many smps makers and sellers here (Indonesia) from very bad designs to very good ones, some of them just copied other design

transformer parameter
Np : 16T
Ns : 2x6T for +/- 70V
Lr 27uH
Lp 143uH

update :
I change inductane ratio Lm/Lr to around 10
the new parameter :
Np : 16T
Ns : 2x7T for +/- 70V
CR 200 nF
Lr 27 uH
Lm 268 uH
Lp 295 uH

Fr1 68,49 kHz

CF 330 pf
RFmin 18 kOhm
RFmax 24 kOhm

fmin 56,12 kHz
fmax 98,20 kHz

with the results of more stable regulation at no load and temperature goes down from 60 to 52C
 

MicrosiM

Administrator
Staff member
update :
I change inductane ratio Lm/Lr to around 10
the new parameter :
Np : 16T
Ns : 2x7T for +/- 70V
CR 200 nF
Lr 27 uH
Lm 268 uH
Lp 295 uH

Fr1 68,49 kHz

CF 330 pf
RFmin 18 kOhm
RFmax 24 kOhm

fmin 56,12 kHz
fmax 98,20 kHz

with the results of more stable regulation at no load and temperature goes down from 60 to 52C

Did you try to go down to RFmin = 10Khz
 
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