FET driver not working..why?

For schematic,see the PDF at http://www.oil4lessllc.org/Misc/ .
Basically, i amusing a 555 to drive the input of an IR2118, which is
a high side inverting FET driver.
have it all wired as per diagram in the datasheet.
Using a 12V supply for the 555 and see a 12V positive gate pulse WRT
FET source.
I adjust supply on the drain to see what is (not) happening; a 100
ohm load is from source to ground.
All i see is a 12V pulse across the load; *not* that adjustable
supply voltage; and _that_ is what i want: the supply to be switched to
the load.
So..pray tell what this idiot is doing wrong and indicate how to fix
(pulse transformer for gate drive?).

 

you made a wrong connection, +12V should not be connected to pin8 on
the ir2118

gate drive voltage is on 0.47u charged via the diode when the fet is
off

-Lasse

 

Also the bootstrap diode is recommended to be ultra-fast recovery-- a
1N4007 is more like ultra-slow. You could change it for a UF4007 or
UF4004.


Best regards,
Spehro Pefhany

 

You need to move the 12V connection from VB to VCC, and also connect a bootstrap capacitor between VB and VS, on the order of 10x Cin, and as mentioned use fast recovery diode between the VB-VCC.

 

and looking at again, the +12V need to be connected to Vcc, and the
0.47u
bootstrap cap goes between pin 8 and pin 6, not between pin8 and
ground

must have been going a little too fast

-Lasse

 

Nice, that link totally shut down my FF when I clicked in the PDF link..

Shut it down with no notice and when I restarted it, all it did was
restore my other tab and had the audacity to not even apologies for it!


Oh well.

Jamie

 

Wow! You're even more incompetent than I imagined.

 

No asshole, the link was block via my ISP when Acrobat tried to load
it. You are a total imbecile, one that really does not know what ****
they are talking about and likes shaving their own foot in their month

I hope you like eating shit, because it appears that you walk in it
all day, and after putting your foot in your mouth like you do, often,
it must not be too tasty by now..

what a winner of a child your mother had.. You must of been the
drippings from the sheet on that one knight out she couldn't remember.

Jamie

 

Good point. It expects to be actively or passively pulled down within
a couple volts of ground during the 'off' times.


Best regards,
Spehro Pefhany

 

You are probably incorrect, but the wiring is directly from the data
sheet.

 

What i want is the FET to completely turn on and off - thereby giving
the load a HV pulse.

 

AFAIK not stated in the data sheet.
Excellent point..thanks.

 

Thanks.
That connection was drawn wrong.

 

Check.

 

Try this. LTSpice format. Your drawing looks good , so you've obviously corrected it in the mean time. Never tried this with dropbox before , so hope it works.

https://www.dropbox.com/sh/cqh7lzfr0otyy58/anDm0atzqa

Cheers
Ned

 

Unlike you, I have never shaved my own foot in my month.

English must be your third language.

 

Well, he probably "designed" it. What would you expect from a pig (ham)
who runs to the ARRL and claims "Daddy! Daddy! .. he picked on me"

 

Had a more serious problem that totally explained the why: the FET
drain was open(!).
Schematic has been updated and corrected.
Works nice into a 100 ohm resistor as load.
Next will be the acid test..
The load will be the B+ (bottom) end of the flyback transformer in
the TV set; a 33uF filter cap will be across that load for a
closer-to-DC (adjustable) drive.

 

Only the cap was wrong..

 

"Time step too small; time = 6.47366e-06, timestep = 1.25e-19;
trouble with u2:diode25-instance d:u2:_md4_d3 OK"