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Registered Member #18429
Joined: Sat May 18 2013, 02:05AM
Location:
Posts: 19
Thanks for the suggestions! I'll use the nylon bolt method...
At present I am having some problems with the UD1.3 driver... After finally locating a solder blob bridging two pins of a MOSFET, I get a full +/- 20V swing on the GDT secondary (I subtituted a 20V power regulator instead of Ward's 24V one), but the waveform seems to contain some really high frequency ringing (?) which makes the traces look really thick, and something is wrong with the rising edge: (10V/div, 20µs/div)
The P-channel mosfets heat up quite a bit (especially Q3) although the connections and orientation appears to be correct. Also I hear a high pitched noise when running the circuit... The schematic can be found here
I am using a 555 square wave generator for feedback at 5V and around 10kHz.
Here is the gate waveform to one of the N channel MOSFETs:
To the P channel MOSFETs (via DC-blocking(?) capacitor)
Registered Member #18429
Joined: Sat May 18 2013, 02:05AM
Location:
Posts: 19
Any thoughts?... In all my projects so far I've never seen a waveform like the first one I posted, in terms of trace thickness and weird dead-time differences, so I'm at a loss as to what would could be causing it.
I've spent many hours troubleshooting the circuit and would appreciate any feedback about the waveforms!
EDIT: Well I checked over the PCB connections again and noticed that one of the diode pins simply wasn't soldered properly... (the diode connected to the gate signal for the P mosfets). After resoldering, the edges of the waveform looked normal, but the ringiness/trace thickness was still apparent and the MOSFETs still hot.
I tried swapping the GDT for a differnent one, and using a faster 555 feedback signal (to increase reactance), and everything looks OK now! Just some under/over shoots but hopefully the IGBT gate zeners should take care of that.
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First DRSSTC -- questions
