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Solid State Tesla Coils (SSTC) / SSTC issues (gate signal, interrupter-mode, grounding)
« on: April 12, 2020, 09:54:27 PM »
Hey there!
I am building the Kaizer SSTC1 as my first SSTC project and I ran into some issues.
First off, I based the circiut around the schematics given from http://kaizerpowerelectronics.dk/tesla-coils/kaizer-sstc-i/]http://kaizerpowerelectronics.dk/tesla-coils/kaizer-sstc-i/. I only changed one thing: I didn't have a UCC37322 IC, so I used two UCC37321 and inverted the input-signal for one of those two drivers with the help of a spare input of the 74HC14 IC.
I currently use two lab-supplies for powering the electronics and the coil itsels seperately. Later on, one supply should be replaced with the variac.
The coil has its resonant frequency at 210kHz.
1) When running on low voltage (10V) the circuit works rather good. The only issue is a small spike at the rising edge of the gate-signal. When increasing the input voltage up to 30V, the spike grows and the gate-signal gets very noisy and unclean. At a certain point (above 40V) the frequency jumps to about 600kHz and the supplies go into current limitation. The only way to get the system back to its resonant frequency is to shut it down completely.
The radiated field picked up form the probe of the oscilloscope looks fine, until a certain input-voltage. A significant amount of noise is noticeable at about 30V input.
May this voltage dependent spike have to do something with the Miller-Effect? I checked the GDT with my function generator, the signal looks perfect even with the MOSFETS connected, but without any load connected. The issues only occur when the bridge is connected to the driver.
Another thing I considered is grounding, I tried different methods of connecting the coil to earth with the same results.
2) I have issues when trying to interrupt the circuit. I tired to tie the enable-pins of the UCC37321 ICs directly to ground but the circuit keeps oscillating like usually, no matter what I try. The voltage at the ICs is rather smooth and free from any noise, only very small ripples are noticeable at the voltage-supply for the 74HC14 IC.
What could be the cause of this problem?
Please excuse my english, I'm still learning
Kind reguards,
Max Seiringer
I am building the Kaizer SSTC1 as my first SSTC project and I ran into some issues.
First off, I based the circiut around the schematics given from http://kaizerpowerelectronics.dk/tesla-coils/kaizer-sstc-i/]http://kaizerpowerelectronics.dk/tesla-coils/kaizer-sstc-i/. I only changed one thing: I didn't have a UCC37322 IC, so I used two UCC37321 and inverted the input-signal for one of those two drivers with the help of a spare input of the 74HC14 IC.
I currently use two lab-supplies for powering the electronics and the coil itsels seperately. Later on, one supply should be replaced with the variac.
The coil has its resonant frequency at 210kHz.
1) When running on low voltage (10V) the circuit works rather good. The only issue is a small spike at the rising edge of the gate-signal. When increasing the input voltage up to 30V, the spike grows and the gate-signal gets very noisy and unclean. At a certain point (above 40V) the frequency jumps to about 600kHz and the supplies go into current limitation. The only way to get the system back to its resonant frequency is to shut it down completely.
The radiated field picked up form the probe of the oscilloscope looks fine, until a certain input-voltage. A significant amount of noise is noticeable at about 30V input.
May this voltage dependent spike have to do something with the Miller-Effect? I checked the GDT with my function generator, the signal looks perfect even with the MOSFETS connected, but without any load connected. The issues only occur when the bridge is connected to the driver.
Another thing I considered is grounding, I tried different methods of connecting the coil to earth with the same results.
2) I have issues when trying to interrupt the circuit. I tired to tie the enable-pins of the UCC37321 ICs directly to ground but the circuit keeps oscillating like usually, no matter what I try. The voltage at the ICs is rather smooth and free from any noise, only very small ripples are noticeable at the voltage-supply for the 74HC14 IC.
What could be the cause of this problem?
Please excuse my english, I'm still learning
Kind reguards,
Max Seiringer
