ESP8266 Community Forum

- Thu Mar 16, 2017 3:15 am #63770 Hello~all,
Please look at the following picture carefully at first.My questions:
1).Why it has no any effect even I increase the R167?The current of Vds in Q29 is 60V while the current input is 24V.( It’s a VRLA battery wish 200AH)
2).Why the 2N7002 was burned in my circuit? The feature of burning out is the MOS was penetrated by current when opening the machine in just a few second !
Is here the voltage is so big ? Any idea do you have?
Thank you in advance.

PS: This is the link of 2N7002's datasheet: http://www.kynix.com/uploadfiles/pdf/2N7002+702.pdf,please have a look if it's needed.

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- Sat Mar 18, 2017 3:13 pm #63899 Hi !
Look at your P Mosfet datasheet : gate capacitance (may be some nF), or gate Charge in nC (nano Coulomb)
When your 2N7002 is switched on , it shortens P Mosfet charged capacitance, current may arise above Q29 ID max.
Transient curents in Power Mosfets (gate charging or discharging) are not negligible.
Try with some resistor (1K ? 4K7 ?) in series with Q29 drain to avoid Q29 burning. (limit PMOS gate discharge current)