INN3167 hot start issue
Issue: some of (few%) devices PSU (12V 2.5A) didnt start after power cycling. Looks like Cbpp still charged, Cbps discharged while applying input, typically its 1-20s after poweroff.
Also - didnt work CC profile.
If PSU started someway - it works perfect, in full range of input voltage and output current. Bug is critical, dead device after grid blinking.
What are already checked:
-bug not visible, if Cout left charged
-bug not visible, if discharge Cbpp
-bug migrated with some transformers (didnt seen differences in measurements, see below)
-Cbps replaced 2.2u-4.7u-10u
-Cout replaced 220u-1000u
-Cbpp replaced 0.47u or 4.7u
-Rbpp replaced 3k, 7k, 10k, 13k
-IC replaced (again, bug is migrated with transformers)
-UV/OV disabled
Transformer data
| Transformer OK | Transformer NOK | |
|---|---|---|
| Primary inductance, uH | 563 | 565 |
| Secondary inductance, uH (half/half) | 8,2 (8,13/8,17) | 8,14* (8,18/8,21) |
| Bias inductance, uH | 10,2 | 10,15 |
| Primary leakage, uH, Secondary shorted | 23,4 | 24,5 |
| Primary leakage, uH, half secondary shorted | 26,22/26,0 | 26,1/29 |
| Secondary Leakage, uH, primary shorted | 0,35 | 0,37 |
| Half secondary Leakage, uH, primary shorted | 0,4/0,4 | 0,4/0,44 |
| Phase check, uH, All windings in series | 877 | 880 |
Schematic data - added.
FWD pin osc view - added (FWD and Cbps voltages while unsuccesfull start attempt, 14 pulses)
评论
Hello Viktor,
Since the issue seems to be transformer related, I would assume it is of common mode nature. Please evaluate dv/dt levels observed on primary and secondary switching nodes, including primary bias rectifier.
Kind regards,
PI-Dmitry
Here is more complete osc pictures, succesfull and failed startup