I am generating a 10Hz square wave with a CD4060. The output is fed into a BD139 that drives a potted HV module (input resistance 18.5K). Power supply is 5VDC. The purpose to to flash a neon lamp. I am aware there are other ways of doing this, but this is part of a larger project.
The generator works perfectly on its own. But when I connect the HV module, the DC level shifts up about a volt, and ringing appears across the top of the wave form. When I connect the neon lamp, the ringing increases about three fold. Please refer to photos provided. Ignore the speaker in the schematic.
Can someone please suggest a solution so I can understand the problem? It appears to be related loading, but the 18.5K seems reasonable enough to me. Maybe it is some kind of feedback from the bridge? Nothing I have tried so far removes it, even in the slightest.
The generator works perfectly on its own. But when I connect the HV module, the DC level shifts up about a volt, and ringing appears across the top of the wave form. When I connect the neon lamp, the ringing increases about three fold. Please refer to photos provided. Ignore the speaker in the schematic.
Can someone please suggest a solution so I can understand the problem? It appears to be related loading, but the 18.5K seems reasonable enough to me. Maybe it is some kind of feedback from the bridge? Nothing I have tried so far removes it, even in the slightest.
Attachments
-
255.4 KB Views: 20
-
17.1 KB Views: 22