Gregory's ServerI wonder if my fatal analog design problem can be "fixed in software" and suddenly had an idea... Instead of turning the flyback converter on continuously, I changed the firmware to run it in small 1-millisecond bursts per every 10 ms, allowing the 10 V isolated power supply to recover and recharge between pulses. Unbelievable, this hack worked! It successfully charged the capacitor bank to 1000 V... ⚡ #electronics
|
7 comments
 Setting up the fail-safe crowbar and watchdog timer early on before debugging other parts of the high-voltage circuit turned out to be really worthwhile. Now I love how I can physically discharge the dangerous capacitor by just pressing Control-C in my Unix terminal emulator. #electronics Trap for young players... If you're disabling another interrupt within an interrupt, that disabled interrupt source may have already set its flag just before you've disabled it, causing a TACTOU situation. When the ISR returns, that supposedly-disabled IRQ is immediately invoked. I just spent an hour trying to debug a strange problem because of this race condition... :woozy_baa: #electronics Success. High-voltage supply and regulation are now fully functional. My fatally flawed analog power supply problem has been fixed in software. The burst-ON hack turned out to not "just a software hack" but kind of an optimal solution given the circuit components constraints. If I need a real hardware solution I'd just implement exactly the same control with RC timers and AND gates instead of an interrupt service routine. #electronics More progress on the high-voltage impulse generator. The huge capacitors, resistors and inductors for pulse shaping are now installed for testing. They mostly work. But this test uncovered a serious problem - each time the circuit fires, I can hear an arcing noise, the oscilloscope also shows a weird glitch, likely caused by arcing. The generator is supposed to destroy the device-under-test, not itself! Now my suspect is the isolated DC-DC module. Just ordered a better one for another try... #electronics Problem solved. The "arcing" sound during the impulse current discharge is NOT a fault. It's actually a common phenomenon in all high-current pulse circuits. The "snap" noise was caused by sudden physical deformations of the circuit board itself, due to Lorentz force from the intense current. #electronics Success! My first circuit board prototype of the IEC 61000-4-5 Combination Wave Generator (aka Lightning Surge Generator, aka Impulse Generator) is working after a month of development. This PCB has greatly improved safety and usability compared to the original perfboard. #electronics |
Voltage regulation at 500 V is even better than my expectation. 2% within theoretical 536 V set point. #electronics