| Electronics > Repair |
| 300W inverter repair - problem with H-bridge |
| << < (3/4) > >> |
| Harry_22:
Hi! I can’t understand why you have -13.2 volts on the trace (trigger mark in the second picture)? Please clarify where the probe and ground were connected. |
| bborisov567:
Probe is connected between source and gate on the top mosfet. I should have inverted the trace. These -13.2 v are actually 13.2 V of Vgs. |
| Harry_22:
I tried to simulate the circuit in Microcap but the upper T6 opens too slowly. I had to increase the period from 25 µs to 100 µs so that the peak reaches 240V. I don't see any problems with the diodes, but it looks like the circuit is slightly different. |
| bborisov567:
I also simulated the circuit on LTSpice and results are looking really good. Yesterday i had some more time to test and it turns out that if connect the probe gate-source the impulses are looking really clean 12 v p-p, but if i connect it source to gate (gnd to gate and active probe end to source) then i observe the oscillation shown before. I believe there might be some issue with the oscilloscope grounding to the grid that causes the bad measurement. |
| BennoG:
--- Quote from: bborisov567 on October 24, 2024, 05:41:05 am ---I also simulated the circuit on LTSpice and results are looking really good. Yesterday i had some more time to test and it turns out that if connect the probe gate-source the impulses are looking really clean 12 v p-p, but if i connect it source to gate (gnd to gate and active probe end to source) then i observe the oscillation shown before. I believe there might be some issue with the oscilloscope grounding to the grid that causes the bad measurement. --- End quote --- Never put the gnd clip on anything else then the gnd of your DUI. Even when you have everything doucopled. Use 2 probes and substract the value in the scope. Or use a differential probe. |
| Navigation |
| Message Index |
| Next page |
| Previous page |