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| blauerscharik:
--- Quote from: fzabkar on July 19, 2024, 04:04:09 pm ---After you switch of the power, does EC01 retain its 320V voltage? If so, this would suggest that 0B2338SP is not starting. Is there a short on the 5V or 12V supplies? Is the 15V pin of the motor controller shorted to ground? --- End quote --- Yes it keeps its voltage and slowly drops. No short on 5V, 12V or pin 41 of the motor controller |
| fzabkar:
--- Quote from: blauerscharik on July 19, 2024, 05:14:28 pm --- --- Quote from: fzabkar on July 19, 2024, 04:04:09 pm ---After you switch of the power, does EC01 retain its 320V voltage? If so, this would suggest that 0B2338SP is not starting. Is there a short on the 5V or 12V supplies? Is the 15V pin of the motor controller shorted to ground? --- End quote --- Yes it keeps its voltage and slowly drops. --- End quote --- As long as the VDD pin is rising above the UVLO threshold (16V), the IC should switch to run mode. If VDD is OK, then the IC is probably faulty. In normal operation the VDD capacitor charges up to 16V via the startup resistors, and the IC then switches to run mode. The IC then pulses its MOSFET chopper. The auxiliary winding on the transformer then supplements the VDD supply via the rectifier diode and takes over from the startup resistor. |
| blauerscharik:
--- Quote ---As long as the VDD pin is rising above the UVLO threshold (16V), the IC should switch to run mode. If VDD is OK, then the IC is probably faulty. In normal operation the VDD capacitor charges up to 16V via the startup resistors, and the IC then switches to run mode. The IC then pulses its MOSFET chopper. The auxiliary winding on the transformer then supplements the VDD supply via the rectifier diode and takes over from the startup resistor. --- End quote --- I don't have a steady voltage on the VDD cap. It jumps around 9V, 10V, 12V 15V an back to 9V. |
| fzabkar:
--- Quote from: blauerscharik on July 19, 2024, 05:46:02 pm --- --- Quote ---As long as the VDD pin is rising above the UVLO threshold (16V), the IC should switch to run mode. If VDD is OK, then the IC is probably faulty. In normal operation the VDD capacitor charges up to 16V via the startup resistors, and the IC then switches to run mode. The IC then pulses its MOSFET chopper. The auxiliary winding on the transformer then supplements the VDD supply via the rectifier diode and takes over from the startup resistor. --- End quote --- I don't have a steady voltage on the VDD cap. It jumps around 9V, 10V, 12V 15V an back to 9V. --- End quote --- That would suggest that the IC is trying to start. It is pulsing the MOSFET, but the auxiliary winding is not replenishing the lost charge in the VDD capacitor. Every pulse reduces the charge until VDD falls below 8V, at which point the IC switches from run mode back to start mode. The capacitor then recharges to 16V via the startup resistor and the cycle repeats. In other words, your supply is hiccuping. This is most often due to an overload on the secondary side, or a bad VDD capacitor (high ESR). I would hardwire a second capacitor in parallel with the 10uF cap and see whether this resolves the problem. Edit: Is the 2R2 sense resistor OK? Is the primary winding of the transformer OK, ie not open circuit? Here is a source for the IC: https://www.lcsc.com/product-detail/Switching-Controllers_OB-On-Bright-Elec-OB2338SP-H_C507634.html |
| blauerscharik:
--- Quote ---In other words, your supply is hiccuping. This is most often due to an overload on the secondary side, or a bad VDD capacitor (high ESR). I would hardwire a second capacitor in parallel with the 10uF cap and see whether this resolves the problem. Edit: Is the 2R2 sense resistor OK? Is the primary winding of the transformer OK, ie not open circuit? --- End quote --- I tried a new cap 50V 22uF (the smallest I had on hand). Same issue. I took out the transformer the windings are fine. The 2R2 resistor shows 2.1ohms so that's fine. Can I not just bypass this circuit altogether so it's always on? |
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