Hello. I'm working on a driver for my VFD filaments. Say I need a Vfilament of 1.6V, and a current of 40mA, such as with a small VFD.
So far I have a square wave driver set up, basically for my two filament pins I can alternate the two pins between 1.6 and 0 with some H bridge at maybe 100KHz. If I connect the filament load to this, it's the equivalent of using a 3.2V Vpp square wave biased at 0v. See Sim Link 1. I put two 40 ohm resistors as a stand in for 2 VFD tubes filaments in parallel. However, I'd like to add some sort of smoothing and DC bias. I was thinking of using a small transformer, such as this one: https://www.mouser.com/datasheet/2/445/750315240-3096542.pdf Applying a 100KHz RC low pass filter to the output, and approximating the turn ratio at 1:1 (it's 1:1.1 in the datasheet but ignoring that for now), I have a simulation below as Sim Link 2. The problem here is I seem to be wasting a huge amount of power just driving the transformer on the primary size. The plot on the very far left shows I'm delivering 2.2A to the transformer. I guess I could find a larger transformer with a higher inductance, or increase my switching frequency, but I'm not sure if I'm on the right design path here. Also, it seems like some of my issues stem from my LC filter. If I remove that, the simulation shows more reasonable primary currents of 100mA. See Sim Link 2. I don't really remember my ECE courses from a long time ago, so I'm not sure what is going on here. Anyone have any suggestions? Sim Link 1: https://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCDsB0AcYCYCsBTAtLEAGaBOWuYALFrgGwDMFRSSkSZIuuISrWr6YYAUAG7hE4Mh24IQRTB3FgscudjiKpipP0HiKZTGJDJG08PIU4pSitGJgkuBGSQUkBSLgqqeAcw3DRQsLexsT28tHSESDkieAHdvSXAA+KweACdWBB0M9J0AjhIYiQV-cSIyIgTxZNjS8sRMJCy6oOqyiuy25LS6RibujsKChpzxPuLm1kgerKHwLKq2+IQSCSkC3X09ZY35pekGTdFcgt3ZzAjT8fOxk7H5q6yai53lxeWm5IB7QIhRJGtaViKcqGDgUHhfNg-PRYSRuBDQNg4LCQvSAsEQ8BQcCOMD0QE4CAyRRYSDwZA8IA Sim Link 2: https://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCDsB0AcYCYCsBTAtLEAGaBOWuYALFrgGwDMFRSSkSZIuuISrWr6YYAUAG7hE4Mh24IQRTB3FgscudjiKpipP0HiKZTGJDJG08PIU4pSitGJgkuBGSQUkBSLgqqeAcw3DRQsLexsT28tHSESDkieAHdvSXAA+KweACdWBB0M9J0AjhIeMDIWBBJwLIiylRx5WWY6+oaWMGhSAixato7MNGbEWAYsCgRZMGosLOaseiIie2ItSARSGRbp2aR5skXhokVmGIkFf3FZ3eOggSIhvVKr8SWqw-BAyOg1WIrCvOuvoI+fkQSa4PIJeO43b73RYvA6nSrZeHJAAOIBEmUwaL0DBAbiiXkx+lRWEwCGhUQ+ZDOASQE1yqUOonKlMR4B4AGMJMy+pyqeJXsZ2oxmrAtHZ4IMiIRILpqu16XQhVkFQk+YcDjScuJledkrFtUqJlldaxIIqMcTEQdzvESnkpFahITbViDAdnU7Sjr2RCJCTPUbFMYIDgiIgMuQyKT8JJyIG5QB7QLB8AbWhsNgWVWqig8RNsZNLSRuBBvRQQCBanG51jPSDgRxgeg1nAV54thjIaujNuHfDNyw41lAA Sim Link 3, no LC Filter: https://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCDsB0AcYCYCsBTAtLEAGaBOWuYALFrgGwDMFRSSkSZIuuISrWr6YYAUAG7hE4Mh24IQRTB3FgscudjiKpipP0HiKZTGJDJG08PIU4pSitGJgkuBGSQUkBSLgqqeAcw3DRQsLexsT28tHSESDkieAHdvSXAA+KweACdWBB0M9J0AjhIeMDIWBBJwLIiylRx5WWY6+oaWMGhSAixato6zRGsiOyJILApEXEgyCDRq2AQKWG1ISAQ7OhE2SZbp2fnF5bGhxWYYiQV-cSIyIgTxZIEiCnESvPu9LCrj8EDI6DVYisKnmQiIK-Z7-CTPBCvIJeO4PUqwvSLT5Hc6XRCYJBZdFBAAOIBEmUwBL0DBAbiiXmJ+nxUIQSKivwuV2yzOSaRWlVYY1ZxyOmJy4g5p2BXMY2P5nOSsSFWWJ2KlzPijwkUiOumpyupCs1pOVwuSAGM9PDMHqsl9jBApmQRAhRhQsJJRrgsNcWu0USdykz5TwAPaBK3gJDWWisRSXQwcCj+8NByGSNxsHAyPThmMBtgQSDgRxgejhnAQVM4MjIWNgNxBkj4QuWMngHhAA -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/5b312e27-2546-4c4c-a22f-8c4fada6d2dcn%40googlegroups.com.
