Timeline for Custom buck converter putting out 1V instead of 5V
Current License: CC BY-SA 4.0
13 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Nov 22, 2023 at 8:48 | review | Close votes | |||
| Nov 22, 2023 at 18:47 | |||||
| Nov 22, 2023 at 2:28 | vote | accept | Stephen D. | ||
| Nov 22, 2023 at 2:26 | comment | added | jsotola | please turn off the grid when taking a screenshot of the schematic diagram | |
| Nov 21, 2023 at 23:46 | answer | added | qrk | timeline score: 2 | |
| Nov 21, 2023 at 23:43 | comment | added | MiNiMe | If you have the time and the will, removing the grid and add more contrast to the schematic would be superb. | |
| Nov 21, 2023 at 23:27 | comment | added | BeB00 | @StephenD. what do you see on Vin? could you post all of your oscilloscope traces (inductor and Vin)? | |
| Nov 21, 2023 at 23:06 | comment | added | Stephen D. | @JohnD I have 2 boards acting this way. I can solder up another if needed for confirmation, but that's the last board I have. FB is sitting at 0.13V. I don't have an easy way to try increasing the load current as I don't have any kind of adjustable load and the converter is rated for a few amps, so I'd imagine I need at least an amp to get it out of diode emulation mode. If that's the next troubleshooting step I can try to rig something up. | |
| Nov 21, 2023 at 22:39 | comment | added | John D | @StephenD. The inductor ringing that you see could be normal for discontinuous mode (light loads). Does the ringing go away as you increase the output current toward full load? The ringing should start after the switch node goes low for some period and the inductor "runs out" of current. This happens when the part is operating in "diode emulation mode". | |
| Nov 21, 2023 at 22:34 | comment | added | John D | I don't see anything obviously wrong. Is the FB pin sitting at 0.8 V as you change the line and load? As @BeB00 said looking at the switch node on a 'scope might provide a clue also. Do you just have 1 board acting this way? Can you swap out the IC? | |
| Nov 21, 2023 at 22:22 | comment | added | Stephen D. | With the scope connected to pin 1 of the inductor and ground, I see the inductor ringing (a decaying sinewave). Connected between pin 2 and ground, I see a flat line, with some 60Hz ripple on top of it. | |
| Nov 21, 2023 at 22:03 | comment | added | BeB00 | Have you checked the waveform at the inductor, and at the output, with an oscilloscope? | |
| S Nov 21, 2023 at 21:57 | review | First questions | |||
| Nov 21, 2023 at 23:43 | |||||
| S Nov 21, 2023 at 21:57 | history | asked | Stephen D. | CC BY-SA 4.0 |