The battery-powered design for my wristwatch uses a 3.7v Li-ion battery (1000mA-hr) to produce 180VDC at 7ma. I use a 50:1 transformer (Coilcraft LPR6235), and it will run somewhere around 150kHz. It's controlled by the onboard FPGA, and I have voltage-feedback. The power supply will actually go higher than just the transformer turns-ratio due to inductive effects. The transformer is rated for 100V, so it's going to be interesting to see if it breaks-down at 180V.....
If your area isn't as constrained (wristwatches are brutal....), there are a lot of other transformers available, such as those used in CFLs or laptop backlights. Coilcraft has a nice selection and they sell direct to you even if you only buy single units. The circuit itself is simple: Transformer primary is connected to the 3.7V battery, and to a NMOS transistor. I used a low-leakage DMG3420U. The fpga turns the NMOS on for 2usec, then off. You have to be careful about how long the transformer is energized (otherwise you get really unsafe current), and keep the frequency low enough to minimize losses. I expect I will need to do a lot of tweaking once I get my PCB, but the tweaks are easy because it's an FPGA. The secondary winding goes to a bridge rectifier and small filter cap (0.1uf). I use direct-drive, not multiplex.The 3-1/2 digit 7-segment display is rather large, so there is enough room on the PCB for each segment to have a small NPN transistor and emitter resistor, for current-control. The FPGA drives the NPN at 3.3V; with a Vbe drop of 0.7V, the emitter resistor is calculated from the voltage (3.3-0.7 =2.6v) and the segment current (335uA in my case). I use dual NPNs (PMBTA42DS) to save PCB area. Everything (except the neon display) is surface-mount. -- 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 [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/793de40c-22e5-42f7-a827-6de0b6f696ed%40googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
