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[SOLVED] IGBT + T8 Fluorescent + Simple Ballast = Headache
My first post! Hopefully first of many.
So my story is this, I started this job not too long ago fresh out of school and there are literally no EE's around to actually give me guidance. As a result I'm forced to make just such a post.
So I have a very simple ballast to give a short 1000VDC pulse to turn on a T8 bulb for a short period of time. I'm interested in the propagation of the plasma inside the lamp, so it starting up is pretty crucial. Anyway I devised an IGBT controller circuit and ballast from a variety of sources and all seems well, sort of...
The whole circuit seems to work just fine when nothing is connected to it but when I plug in voltage probes the bulb never turns on. When the bulb turns on and the plasma connects both the cathode and anode the impedance is very low and most all the current sinks through the bulb until the cap is discharged. When I hook up the probes anywhere on the circuit BESIDES across the IGBT the bulb no longer turns on and the cap discharges gradually through the 15k resistor (it's really odd, when the probe is across the IGBT everything works fine, but anywhere else and the T8 no longer turns on). When I put the IGBT between the ground and the rest of the circuit it works fine, however that leaves the cathode at a high potential all the time and makes my experiment useless. I need the IGBT between the cap and the rest of the circuit.
Can anyone please critique my circuit that drives the IGBT? I'm 80% sure my problems lie with the negative of my 12 volt float and how it interacts with the rest of the ballast. How could I properly couple it to ground without grounding out the 1000V from the rest of the circuit? Any help would be most appreciated!
Circuit:
b.imagehost.org/0795/circuit.png
My first post! Hopefully first of many.
So my story is this, I started this job not too long ago fresh out of school and there are literally no EE's around to actually give me guidance. As a result I'm forced to make just such a post.
So I have a very simple ballast to give a short 1000VDC pulse to turn on a T8 bulb for a short period of time. I'm interested in the propagation of the plasma inside the lamp, so it starting up is pretty crucial. Anyway I devised an IGBT controller circuit and ballast from a variety of sources and all seems well, sort of...
The whole circuit seems to work just fine when nothing is connected to it but when I plug in voltage probes the bulb never turns on. When the bulb turns on and the plasma connects both the cathode and anode the impedance is very low and most all the current sinks through the bulb until the cap is discharged. When I hook up the probes anywhere on the circuit BESIDES across the IGBT the bulb no longer turns on and the cap discharges gradually through the 15k resistor (it's really odd, when the probe is across the IGBT everything works fine, but anywhere else and the T8 no longer turns on). When I put the IGBT between the ground and the rest of the circuit it works fine, however that leaves the cathode at a high potential all the time and makes my experiment useless. I need the IGBT between the cap and the rest of the circuit.
Can anyone please critique my circuit that drives the IGBT? I'm 80% sure my problems lie with the negative of my 12 volt float and how it interacts with the rest of the ballast. How could I properly couple it to ground without grounding out the 1000V from the rest of the circuit? Any help would be most appreciated!
Circuit:
b.imagehost.org/0795/circuit.png
