General > General Technical Chat

Quick TVS diode question. Vclamp < Vbreakdown

<< < (7/12) > >>

kellogs:
Hmm... perhaps that could work. How about adding an TVS diode (+ maybe inductor & MOV trick) to this diagram



With some caveats:

- substitute U1 and U6 with at least 101V able P-mosfets. Actually just U1 I think, U6 should be disengaging -220V spikes, I wonder if fast enough...
- parallelize U1 and U6 into a number of P-mosfets each in order to avoid heat issues and voltage drop
- work these resistors to adjust for +150V spikes on the small Zeners + fat one  (-220V too?), and maybe not screw up whatever balance the current values achieve

What do you think ?

T3sl4co1l:
Something like that.

Note that TL431 can't saturate less than a Vbe below VREF, so won't turn off a 2N7002.  Some voltage offset could be added to M1 source, or a P-type inverter used.

Also note you want hysteresis to prevent chatter as it goes on and off.  Your load is going to be pretty significant after being off for a few 10s-100s ms. :)

Tim

kellogs:

--- Quote from: T3sl4co1l on September 07, 2022, 02:09:51 am ---Your load is going to be pretty significant after being off for a few 10s-100s ms. :)

Tim

--- End quote ---

Could you elaborate on this ? Not sure what to make of it.

Also, does a 1uH inductor look right for the clamping voltages involved in 12V automotive ?

T3sl4co1l:
I mean when it switches back on, charging your input caps will surely make it chatter.

1uH is probably fine, also helps with general filtering, put some small caps around it (couple uF?).

Tim

kellogs:

--- Quote from: T3sl4co1l on September 07, 2022, 09:47:50 pm ---I mean when it switches back on, charging your input caps will surely make it chatter.
Tim

--- End quote ---

Ok... but why ? And which part is going the chatter to form at, the fat Zener ?

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod