I notice SOMETHING(C) when solenoid valve is triggered in high speed

[circuit_freak]

Hi all,

Probe is connected at mosfet output(where solenoid is triggered) and below is what i got.

**broken link removed**

A - Rising & Falling interval is 80us [it off before on completely]
B - Rising & Falling interval is 1ms [it off after on completely]
C - Output remains ON for more than 120ms, it happens occasionally.

The ON in C is generated by solenoid, so can i presume C happens because of residue energy in solenoid inductor? correct me if i am wrong.

Whenever i trigger the solenoid in high speed as described in A(Rising & Falling interval is 80us) C happens occasionally, which it is a problem for me.
The controlling waveform is normal, C happens only when it is used to trigger inductive load.

So Any idea how to solve this please? thanks.

 

[ericgibbs]

hi,
It appears that 'punch through' is occurring when switching the inductive load.

Look here: **broken link removed**

 

[circuit_freak]

hi,
while going thru the provided link, please have a look on below..

The mosfet i use have turnontime 0.7ms(typ), 5ms(max) and turnofftime 0.04(typ), 5ms(max).
Told by a senior C happens becuase of the turnontime in A has out of spec, what do you think?

thanks.

 

[duffy]

Driver latchup. Usual fix is a "snubber" circuit (a resistor in series with a capacitor) across source and drain on the driver. Need some details on the solenoid to suggest some values.