Author Topic: DRSSTC feedback issue  (Read 290 times)

Offline Radek

  • High Voltage Enthusiast
  • *
  • Posts: 6
  • Karma: +0/-0
    • View Profile
DRSSTC feedback issue
« on: April 04, 2019, 11:21:48 PM »
Hello,

I've been working on my medium-sized DRSSTC for a while. Currently, I'm trying to tune the primary LC circuit with the iron load. However, I've been struggling with the ud2.7C that is unable to tune to the feedback signal. I tried to increase the Vbus high enough to get about 50 mA on the secondary of feedback CT which should make about 3 V sinusoidal signal on the feedback input (considering the 51 R resistor on the ud board), but it still did not help. So the only signal I've got on the IGBT gates is from the interrupter (tried to increase the ontime, but it has no effect when no feedback). The CT ratio is 1:200. I scope on the extra CT with 5,1 R resistor connected to its secondary. OCD is set to 1 V (equals to about 45 apk).

Do you have any ideas why the ud is unable to tune to the primary LC resonant frequency?

Thank you in advance.

I attach the CT output wave (150 mV) with the gate wave (52 V pk-pk).


Offline Fumeaux

  • High Voltage Enthusiast
  • *
  • Posts: 48
  • Karma: +4/-0
    • View Profile
Re: DRSSTC feedback issue
« Reply #1 on: April 05, 2019, 08:59:16 AM »
There is one problem. The UD2.X are intended to work with primary feedback and not with secondary feedback. On loneoceans schematic it doesn't say so, but im sure on his post about the UD2.7 he said it somewhere.

There it does:


I can advise you to read the whole aticle before continuing http://www.loneoceans.com/labs/ud27/
« Last Edit: April 05, 2019, 01:27:58 PM by Fumeaux »

Offline dexter

  • High Voltage Enthusiast
  • *
  • Posts: 14
  • Karma: +1/-0
    • View Profile
Re: DRSSTC feedback issue
« Reply #2 on: April 05, 2019, 10:58:12 AM »
Test the UD with a signal generator on feedback CT pins, maybe is something wrong with your board.

My coil also uses 1:200 CT's and i had to increase Vbus over 50V for the UD to tune to the feedback signal

Offline Radek

  • High Voltage Enthusiast
  • *
  • Posts: 6
  • Karma: +0/-0
    • View Profile
Re: DRSSTC feedback issue
« Reply #3 on: April 05, 2019, 05:50:54 PM »
There is one problem. The UD2.X are intended to work with primary feedback and not with secondary feedback. On loneoceans schematic it doesn't say so, but im sure on his post about the UD2.7 he said it somewhere.

There it does:


I can advise you to read the whole aticle before continuing http://www.loneoceans.com/labs/ud27/

I forgot to mention. Of course, I use the primary feedback. As I said, the secondary coil is not in place while tunning. I’ve studied how does ud2.7C work, but still cannot find out what problem I’m dealing with atm.

Test the UD with a signal generator on feedback CT pins, maybe is something wrong with your board.

My coil also uses 1:200 CT's and i had to increase Vbus over 50V for the UD to tune to the feedback signal

I tested the UD with 555 generator to choose a proper value of gate resistor at resonant frequency. Therefore I dont expect there is a problem with the board itself. Only if the type of the signal mattered, because the 555 output signal is a square and fb is obviously sinusoidal.
In my case I put Vbus up to 200 VDC and still did not caught the feedback. I also tried to reverse the FB, still without a result.

Offline Mads Barnkob

  • Administrator
  • High Voltage Senior
  • *****
  • Posts: 949
  • Karma: +11/-0
  • Denmark
    • View Profile
    • Kaizer Power Electronics
Re: DRSSTC feedback issue
« Reply #4 on: April 08, 2019, 08:25:32 AM »
Hi Radek and welcome to HVF!

Quote
(equals to about 45 apk).


This sound like a very low peak current unless its a QCW? I think you have a too weak feedback or wrong phased feedback/output from GDT.

You have to bench test this with a couple of function generators to make both feedback, interrupter and OCD signal, alternatively you can just use a power supply on the OCD input to simulate the threshold level, but then you got no test if it can catch the peaks of a sinusoidal waveform.
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline Radek

  • High Voltage Enthusiast
  • *
  • Posts: 6
  • Karma: +0/-0
    • View Profile
Re: DRSSTC feedback issue
« Reply #5 on: April 08, 2019, 08:42:46 AM »
Hi Radek and welcome to HVF!

Quote
(equals to about 45 apk).


This sound like a very low peak current unless its a QCW? I think you have a too weak feedback or wrong phased feedback/output from GDT.

45 apk is only a safe current for the testing. The nominal primary current will be obviously higher. I think, for tuning this current should be sufficient.
I tried to reverse the FB so that wont be the problem. GDT is phased properly too. That was checked by the scope at both gates.

I recently found out by scoping the ud, that there is 500 mV pk-pk signal at the TL3116 input (when about 10 V pk-pk at the FB input/51 R resistor). The output of this comparator is just a constant of 5 V. Have you ever measured the TL input? Is the signal too low or can the TL be damaged somehow?

Offline Hydron

  • Administrator
  • High Voltage Engineer
  • *****
  • Posts: 226
  • Karma: +6/-0
    • View Profile
Re: DRSSTC feedback issue
« Reply #6 on: April 08, 2019, 04:13:52 PM »
I would suggest also looking at the other (reference) input of the comparator to sanity check things - if the input voltage crosses the reference voltage and there is still no output then the comparator has an issue.

Offline Radek

  • High Voltage Enthusiast
  • *
  • Posts: 6
  • Karma: +0/-0
    • View Profile
Re: DRSSTC feedback issue
« Reply #7 on: April 08, 2019, 04:33:50 PM »
I've already checked the reference input (voltage divider). There is 1,6 V as expected. The other (FB) input reaches about 500 mV pk-pk as its maximum (even at about 200 VDC on the bus). So it is understandable that it cannot set the comparator. However, I don't understand why there is such a low signal when at the FB input itself (CT secondary) is more than 10 V pk-pk. The higher current won't make it any better I think. I cannot let through the feedback approx. 0,5 A when the ud is not tuned yet. That would make such a high current when there is a nominal primary current (let's say 200 apk).

There is a comparison of the signal at FB input (14,8 V pk-pk) and comparator input (480 mV pk-pk).

Offline Hydron

  • Administrator
  • High Voltage Engineer
  • *****
  • Posts: 226
  • Karma: +6/-0
    • View Profile
Re: DRSSTC feedback issue
« Reply #8 on: April 08, 2019, 07:55:49 PM »
The 500mV swing is expected - there is a series resistor and clamping diodes which limit it after the burden resistor. It should actually swing above/below the same ~1.6V as the reference input uses.

Offline Radek

  • High Voltage Enthusiast
  • *
  • Posts: 6
  • Karma: +0/-0
    • View Profile
Re: DRSSTC feedback issue
« Reply #9 on: April 08, 2019, 08:06:11 PM »
Well, so do I understand it properly that the issue is due to the comparator itself then?

Offline Hydron

  • Administrator
  • High Voltage Engineer
  • *****
  • Posts: 226
  • Karma: +6/-0
    • View Profile
Re: DRSSTC feedback issue
« Reply #10 on: April 08, 2019, 09:01:06 PM »
It may not be the comparator. Have a read up about how they work - they switch when the relative polarity at the two inputs changes. That's why I asked about both inputs and what voltage they were.
If they are not both approx 1.6V (e.g. one is near zero like your scope trace suggests) with no feedback input then something else is incorrect in your input circuitry.

Offline Radek

  • High Voltage Enthusiast
  • *
  • Posts: 6
  • Karma: +0/-0
    • View Profile
Re: DRSSTC feedback issue
« Reply #11 on: April 08, 2019, 09:34:38 PM »
The reference input should be a constant of 1.6 V, am I right?

High Voltage Forum

Re: DRSSTC feedback issue
« Reply #11 on: April 08, 2019, 09:34:38 PM »

 


* Recent Topics and Posts

post Troubleshooting my first SSTC
[Solid state Tesla coils]
Seb555
Today at 08:14:08 AM
post Re: Secondary Design Tool
[Dual Resonant Solid State Tesla coils]
Fumeaux
April 18, 2019, 10:33:01 PM
post Re: New small SSTC
[Solid state Tesla coils]
Mads Barnkob
April 18, 2019, 10:28:28 PM
post Re: Secondary Design Tool
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
April 18, 2019, 10:24:33 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
Mads Barnkob
April 18, 2019, 10:13:06 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Mads Barnkob
April 18, 2019, 09:51:49 PM
post Re: Question about secondary
[Spark gap Tesla coils]
thedoc298
April 18, 2019, 09:26:14 PM
post Re: Question about secondary
[Spark gap Tesla coils]
dexter
April 18, 2019, 09:20:15 PM
post Which way would be correct (for primary)
[Spark gap Tesla coils]
thedoc298
April 18, 2019, 09:10:30 PM
post Re: Question about secondary
[Spark gap Tesla coils]
thedoc298
April 18, 2019, 08:01:36 PM
post Re: Question about secondary
[Spark gap Tesla coils]
Fumeaux
April 18, 2019, 07:04:40 PM
post Question about secondary
[Spark gap Tesla coils]
thedoc298
April 18, 2019, 06:32:18 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
DICKEYBIRD
April 18, 2019, 04:32:55 PM
post Re: Resisitors
[Spark gap Tesla coils]
thedoc298
April 17, 2019, 11:12:06 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Netzpfuscher
April 17, 2019, 10:44:02 PM
post Re: Please help me in choosing a driver circuit
[Solid state Tesla coils]
Laci
April 17, 2019, 09:38:39 PM
post Re: Please help me in choosing a driver circuit
[Solid state Tesla coils]
Fumeaux
April 17, 2019, 09:29:05 PM
post Re: Would this be about right or not.
[Spark gap Tesla coils]
thedoc298
April 17, 2019, 09:22:07 PM
post Re: Please help me in choosing a driver circuit
[Solid state Tesla coils]
bogdan
April 17, 2019, 09:08:08 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
April 17, 2019, 09:01:40 PM
post Re: Please help me in choosing a driver circuit
[Solid state Tesla coils]
Laci
April 17, 2019, 08:55:48 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Fumeaux
April 17, 2019, 08:51:47 PM
post Re: Please help me in choosing a driver circuit
[Solid state Tesla coils]
Fumeaux
April 17, 2019, 08:42:33 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
April 17, 2019, 08:34:44 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Fumeaux
April 17, 2019, 08:22:30 PM
post Re: Please help me in choosing a driver circuit
[Solid state Tesla coils]
Bambinz
April 17, 2019, 08:16:07 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
April 17, 2019, 08:14:52 PM
post Re: Please help me in choosing a driver circuit
[Solid state Tesla coils]
bogdan
April 17, 2019, 07:55:29 PM
post Teach your kids electronics
[Beginners]
Mads Barnkob
April 17, 2019, 11:51:59 AM
post Re: Secondary Design Tool
[Dual Resonant Solid State Tesla coils]
Fumeaux
April 17, 2019, 09:53:36 AM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
April 16, 2019, 08:46:05 PM
post Re: New small SSTC
[Solid state Tesla coils]
Bambinz
April 16, 2019, 06:55:02 PM
post Re: New small SSTC
[Solid state Tesla coils]
Bambinz
April 16, 2019, 06:45:24 PM
post Re: Hi Uspring, please show me . . .
[Dual Resonant Solid State Tesla coils]
Teravolt
April 16, 2019, 03:06:02 PM
post Re: Hi Uspring, please show me . . .
[Dual Resonant Solid State Tesla coils]
Uspring
April 16, 2019, 03:26:34 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
petespaco
April 16, 2019, 01:20:34 AM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Netzpfuscher
April 15, 2019, 10:02:19 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
April 15, 2019, 09:28:09 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
April 14, 2019, 09:20:52 PM
post Re: Secondary Design Tool
[Dual Resonant Solid State Tesla coils]
Fumeaux
April 14, 2019, 07:56:40 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
petespaco
April 14, 2019, 03:00:18 PM
post Secondary Design Tool
[Dual Resonant Solid State Tesla coils]
Fumeaux
April 14, 2019, 08:00:59 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
DICKEYBIRD
April 14, 2019, 03:58:34 AM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic circuits]
petespaco
April 14, 2019, 12:23:14 AM
post One trace illustrate 2 resonance frequency
[Dual Resonant Solid State Tesla coils]
VNTC
April 14, 2019, 12:15:19 AM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Netzpfuscher
April 13, 2019, 11:16:20 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
April 13, 2019, 09:40:09 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Netzpfuscher
April 13, 2019, 06:00:05 PM
post Re: Hi Steve, would you please explain . . . .
[Dual Resonant Solid State Tesla coils]
Rafferty
April 13, 2019, 02:45:11 PM
post Re: My first DRSSTC on bricks
[Dual Resonant Solid State Tesla coils]
Laci
April 13, 2019, 09:54:41 AM

Sitemap 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30