High voltage flyback converter for nixie tubes
- Input voltage: 5V - 12V
- Output voltage: 150V - 200V
- Output power: 180V 20mA @ 5V in, 180V 40mA @ 12V in
Schematic and pcb layout created in KiCad 6 Nightly Build (compatible with KiCad 5). Converter also have been simulated with LTspice XVII.
Order board v1.0 from OSH Park
Drain and gate oscillograms:
Measured characteristics:
| Vin, V | Iin, mA | Pin, W | Rload, kOhm | Vout, V | Iout, mA | Pout, W | Eff, % |
|---|---|---|---|---|---|---|---|
| 5,34 | 82 | 0,44 | NC | 180,7 | - | - | - |
| 5,21 | 278 | 1,45 | 37,6 | 180,4 | 4,6 | 0,83 | 57,29 |
| 5,16 | 374 | 1,93 | 28,2 | 180,2 | 6,3 | 1,14 | 58,83 |
| 5,07 | 549 | 2,78 | 18,8 | 180,0 | 9,5 | 1,71 | 61,43 |
| 4,92 | 730 | 3,59 | 14,1 | 179,9 | 12,7 | 2,28 | 63,61 |
| 4,61 | 1170 | 5,39 | 9,4 | 179,5 | 19,2 | 3,45 | 63,90 |
Drain and gate oscillograms:
Measured characteristics:
| Vin, V | Iin, mA | Pin, W | Rload, kOhm | Vout, V | Iout, mA | Pout, W | Eff, % |
|---|---|---|---|---|---|---|---|
| 12,52 | 17 | 0,21 | NC | 180,4 | - | - | - |
| 12,39 | 195 | 2,42 | 37,6 | 177,9 | 4,4 | 0,78 | 32,40 |
| 12,38 | 217 | 2,69 | 28,2 | 177,8 | 6,0 | 1,07 | 39,71 |
| 12,36 | 249 | 3,08 | 18,8 | 177,6 | 9,2 | 1,63 | 53,09 |
| 12,32 | 273 | 3,36 | 14,1 | 177,6 | 12,3 | 2,18 | 64,95 |
| 12,28 | 326 | 4,00 | 9,4 | 177,9 | 18,9 | 3,36 | 83,99 |
| 12,00 | 789 | 9,47 | 4,7 | 176,7 | 38,1 | 6,73 | 71,11 |
- Output current limit can configured with R5 resistor. Less value - more current, but also more heating. With values <0.025 ohm converter may become unstable.
- D1 diode should be replaced with bigger one for operating with maximum current at 12V. Current SOD-123FL diode can be easily thermal destroyed in this mode.
- Improve mosfet layout for better heat dissipation
- Replace one shunt resistor (this values are rare) with 2-3 more generic nominals connected in parallel
- Add test points for drain and gate nets for debugging purpose
- More current, less temperature, more effeciency and etc.