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Calculation of SMPS resonant parts
Calculation of SMPS resonant parts
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Old 8th October 2019, 06:15 PM   #41
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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Well. Also a IR2112 will do the job, with lower output capabilities. Using both mechanism is useless.
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Old 9th October 2019, 12:21 PM   #42
kees52 is offline kees52  Netherlands
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Originally Posted by Osvaldo de Banfield View Post
The schematic in post below, reference and anode are shortcircuited, then the net is useless. C2, C9 caps and the resistor R13 are all shorted out.
Hi Osvaldo


I have done the resonance in sim, but I have a strange problem, when I do set it on very low load, the feedback does run out to max voltages, en without a upgoing frequency, it looks like the output caps does this as it is a lowpass filter on almost dc.

Do you have a kind of idea about this?

thanks
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Old 9th October 2019, 01:09 PM   #43
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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Most SMPS's need a minimum load to maintain the inductors running in the continuous current mode, except those specifically designed to run dry. Now, I know that resonant and quasi resonant need some small capacitances added to the tank to limit the maximum resonant frequency, where drivers and MOSFET's becomes more inefficient.
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Old 9th October 2019, 02:49 PM   #44
kees52 is offline kees52  Netherlands
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I think for audio, we need just to use open loop supply, feedback here does more harm then good, I can use lineair regulators for the tube filaments., just make the smps such that I have al voltages needed or maybe get used later.

For audio we need no feedback as people say here, but for me it was a learn fase to do implement it, but can easy be disconnected later.

I get good regulation when I have 5 amps minimum, I think also the vco from ltspice has a to low action on voltage, but maybe I do something wrong here.

regards
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Old 9th October 2019, 03:21 PM   #45
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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I think for audio, we need just to use open loop supply, feedback here does more harm then good...
I don't imagine why, and without feedback, how will the SMPS maintain the output voltage(s)? Is very risky this.

I made a SMPS with UC3842, STP7N60, PC817 and TL431 for my audio class AB (TDA2006īs and TDA2003's) and performs quite well from about 2 decades ago. Including, it survived a "paint tsunami" when some years ago while painting my house, a large paint stream droped in the STP7N60's heatsink (Grounded). Some sparks, no more.
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Old 10th October 2019, 12:14 PM   #46
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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Yesterday night, returning home in "bondi" (Bus), I was thinking about this topic, and I was wondering if U take into account in the simulations, loses in the circuit, Eddy, hysteresis, copper, etc. This represent a fixed load for the SMPS itself, limiting the frequency coverage of the controller.
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Old 10th October 2019, 02:00 PM   #47
kees52 is offline kees52  Netherlands
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Quote:
Originally Posted by Osvaldo de Banfield View Post
Yesterday night, returning home in "bondi" (Bus), I was thinking about this topic, and I was wondering if U take into account in the simulations, loses in the circuit, Eddy, hysteresis, copper, etc. This represent a fixed load for the SMPS itself, limiting the frequency coverage of the controller.
No I do not have done that, I go build one, I am busy with the pcb, no feedback, and us therefore a uc3843 in fixed frequency and dutycycle 50 procent.

Simulation is a just try, real live is what I need, but the resoances are in the microhenrys and nanofarads, this will not respond on a 10 nH pcb trace.

Then I go play, or not when electrocuted.

See this welder transformer, 4 Kw 160 amps.

regards
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Old 11th October 2019, 06:01 PM   #48
kees52 is offline kees52  Netherlands
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For the problem with feedback loss at low load?.

The solution seems that a LCC version resoant smps does a lot better there, signals looks
more stable, did just halve the capacitance of the resonant cap and did a extra one over the primairy coil, now the feedback does fine, I have ZCS and ZVS as result, even with no load.

Feedback does now the job,, with low and high load, does even the job now with just no load, open output. LCC does better, less ripple I did see also. These are quite good for welding smps

regards
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File Type: jpg LCC-test.jpg (225.9 KB, 20 views)
File Type: jpg ZVS-ZCS-sinusoidal.jpg (183.2 KB, 18 views)
File Type: jpg LCC-schematic-sim.jpg (240.5 KB, 19 views)
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Old 11th October 2019, 06:14 PM   #49
Osvaldo de Banfield is offline Osvaldo de Banfield  Argentina
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C2 = 470nF seems excessively high to me. I slows down too much the response of the filter and voltage sag with sudden loads will be. 1nF is quite better, in my experience.
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Old 11th October 2019, 10:06 PM   #50
kees52 is offline kees52  Netherlands
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Originally Posted by Osvaldo de Banfield View Post
C2 = 470nF seems excessively high to me. I slows down too much the response of the filter and voltage sag with sudden loads will be. 1nF is quite better, in my experience.
It has to be 4.7n it do has inpact on speed, but it is also a pole, we need to do that right otherwise things get bad.

Q of tank is reason for feedback problems open output.

regards
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