Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Possessed IGBT will not turn ON

Swend

Full Member level 4
Joined
May 14, 2019
Messages
237
Helped
10
Reputation
20
Reaction score
9
Trophy points
18
Location
Roskilde, Denmark
Activity points
2,304
Hi All!

I made a PCB for my power supply and assembled it, but now Q2 won't turn ON, and I swear it did when it was a ratsnest. This is the simple schematic:

power-stage.png

I have tested Q1, and that one works fine, but Q2 just makes a little 1uS burst on pin2/q2 even though the gate pulse is 50uS. And if I connect pin3/u6 directly to the gate pin1/q2 it still only makes that 1uS burst on pin2/q2 regardless how long I keep the connection. (q1, q5 and q6 are off at the moment).

Either Q2 must be possessed or I'm missing something obvious, can you please help me out?

SDS00047.PNG
SDS00048.PNG
 

kripacharya

Banned
Joined
Dec 28, 2012
Messages
1,209
Helped
182
Reputation
360
Reaction score
175
Trophy points
1,343
Location
New Delhi
Activity points
0
An obvious suggestion would be to very carefully re-check your circuit board/pcb for errors. And also for dry solder joints etc.
Though it's a great feeling to have a new build work right away, I am always suspicious of anything that works perfectly 1st time around. :)
 
  • Like
Reactions: asdf44

    asdf44

    points: 2
    Helpful Answer Positive Rating

FvM

Super Moderator
Joined
Jan 22, 2008
Messages
46,602
Helped
13824
Reputation
27,896
Reaction score
12,497
Trophy points
1,393
Location
Bochum, Germany
Activity points
272,171
You say "Pin2 Q2", but it's a differential probe. What's the reference node? Similarly, how are measuring Pin1 Q2?
 

Swend

Full Member level 4
Joined
May 14, 2019
Messages
237
Helped
10
Reputation
20
Reaction score
9
Trophy points
18
Location
Roskilde, Denmark
Activity points
2,304
An obvious suggestion would be to very carefully re-check your circuit board/pcb for errors. And also for dry solder joints etc.
Though it's a great feeling to have a new build work right away, I am always suspicious of anything that works perfectly 1st time around. :)
Yes you are right, therefore I abandoned the PBC and started populating a new PCB from scratch making sure every component worked as I soldered. So now it will turn on, but I have no idea what went wrong in the first place.

- - - Updated - - -

You say "Pin2 Q2", but it's a differential probe. What's the reference node? Similarly, how are measuring Pin1 Q2?
My scope is floating, so I'm just using one (and one only) regular probe as a differential probe. I have to make some differential probes when I get the time, so I can use more channels at the same time. The reference is the GND of the driver for GATE, and HV 0 (zero) for the other.
 

FvM

Super Moderator
Joined
Jan 22, 2008
Messages
46,602
Helped
13824
Reputation
27,896
Reaction score
12,497
Trophy points
1,393
Location
Bochum, Germany
Activity points
272,171
My scope is floating, so I'm just using one (and one only) regular probe as a differential probe.
Let me rephrase the question, where do you connect the ground clip in both measurements?
 

Swend

Full Member level 4
Joined
May 14, 2019
Messages
237
Helped
10
Reputation
20
Reaction score
9
Trophy points
18
Location
Roskilde, Denmark
Activity points
2,304
Let me rephrase the question, where do you connect the ground clip in both measurements?
(edited) Sorry, The reference is the GND of the driver for q2 pin1, and HV 0 (zero) for Q2 pin2
 

FvM

Super Moderator
Joined
Jan 22, 2008
Messages
46,602
Helped
13824
Reputation
27,896
Reaction score
12,497
Trophy points
1,393
Location
Bochum, Germany
Activity points
272,171
If you are sure that the -600V is actually present, look for a PCB discontinuity.
 

Nik_2213

Full Member level 1
Joined
Jul 20, 2010
Messages
98
Helped
23
Reputation
46
Reaction score
23
Trophy points
1,288
Location
UK
Activity points
2,037
Too many years ago, when I was into amateur robotics, I'd a home-brew motor-drive board which inspected & tested clean, yet would not work...

Much baffled searching later, I found a hairline fault across a broad track. This had appeared okay under wary examination, tests showed continuity, but it could not carry load, which promptly popped the tiny 'working' bridge...

Murphy's Law Rules !!!
 

Swend

Full Member level 4
Joined
May 14, 2019
Messages
237
Helped
10
Reputation
20
Reaction score
9
Trophy points
18
Location
Roskilde, Denmark
Activity points
2,304
If you are sure that the -600V is actually present, look for a PCB discontinuity.
Yes I measured the -600V it's there. Actually I also had some noise problems with the power supply in my other open thread, could be related. Anyway I abandoned the PBC and started populating a new PCB from scratch making sure every component worked as I soldered. So now it will turn on, but I have no idea what went wrong in the first place, could be noise could be discontinuity as you say, or both - this build is a bit complicated for me with the mix of HV and LV.
 

kripacharya

Banned
Joined
Dec 28, 2012
Messages
1,209
Helped
182
Reputation
360
Reaction score
175
Trophy points
1,343
Location
New Delhi
Activity points
0
....and started populating a new PCB from scratch making sure every component worked as I soldered. So now it will turn on, but I have no idea what went wrong in the first place, could be noise could be discontinuity as you say, or both - this build is a bit complicated for me with the mix of HV and LV.
I would urge you to double check the 'new' PCB routing as well to ensure it matches your ratsnest circuit. Stress on 'new pcb' since that is what you wrote in #1. There could be an error there as well.

All of us here waiting with baited breath to hear about the outcome. :smile:
 

Swend

Full Member level 4
Joined
May 14, 2019
Messages
237
Helped
10
Reputation
20
Reaction score
9
Trophy points
18
Location
Roskilde, Denmark
Activity points
2,304
I would urge you to double check the 'new' PCB routing as well to ensure it matches your ratsnest circuit. Stress on 'new pcb' since that is what you wrote in #1. There could be an error there as well.

All of us here waiting with baited breath to hear about the outcome. :smile:
"baited breath" - now I have performance anxiety.. In order to not disappoint anyone let me make it a two part cliff hanger, I have assembled the new PCB and all IGBT's can turn on/off, next step is to connect some HV on it and see what goes up in smoke....

You know, the day before yesterday was a humid day and my windows was open, nothing worked and noise flying everywhere, couldn't measure anything, this is really sensitive to humidity.
 

kripacharya

Banned
Joined
Dec 28, 2012
Messages
1,209
Helped
182
Reputation
360
Reaction score
175
Trophy points
1,343
Location
New Delhi
Activity points
0
...., next step is to connect some HV on it and see what goes up in smoke....
...
:popcorn: it's going to work. Just connect it all up slowly, safely, securely, step by step.
 
  • Like
Reactions: Swend

    Swend

    points: 2
    Helpful Answer Positive Rating

Swend

Full Member level 4
Joined
May 14, 2019
Messages
237
Helped
10
Reputation
20
Reaction score
9
Trophy points
18
Location
Roskilde, Denmark
Activity points
2,304
:popcorn: it's going to work. Just connect it all up slowly, safely, securely, step by step.
It seems your chanting helped ! Well not fully happy yet, but getting there.

SDS00188.PNG

The commutation is Q1-Q6-Q2-Q5 each one is 50uS. Oh and I didn't put in L1 and all the caps yet..
 

Swend

Full Member level 4
Joined
May 14, 2019
Messages
237
Helped
10
Reputation
20
Reaction score
9
Trophy points
18
Location
Roskilde, Denmark
Activity points
2,304

Toggle Sidebar

Welcome to EDABoard.com

Sponsor

Sponsor

Design Fast


X
Top