FET driver not working..why?

The gate bootstrap isn't right. See the IR data sheet.

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John Larkin                  Highland Technology Inc 
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John Larkin
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For schematic,see the PDF at

formatting link
. 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?).

Reply to
Robert Baer

On a sunny day (Sat, 03 Nov 2012 22:04:40 -0800) it happened Robert Baer wrote in :

Well, you build a switch! Its a source follower!

Does this driver need to HV bias to that drive circuit?

Reply to
Jan Panteltje

is

RT

ix

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

Reply to
langwadt

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

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"it's the network..."                          "The Journey is the reward" 
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Reply to
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.

Reply to
bloggs.fredbloggs.fred

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

Reply to
langwadt

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

Reply to
Jamie

On a sunny day (Sun, 04 Nov 2012 14:05:15 -0500) it happened Jamie wrote in :

Worked OK here 3 times. (I reloaded the pdf after every reply).

Reply to
Jan Panteltje

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

Reply to
John S

Let us know if it works OK.

Depending on the "Load", I don't think this will work too well with a load that is high impedance if the load node doesn't pull down low enough to charge the bootstrap cap.

boB

Reply to
boB K7IQ

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 f*ck 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

Reply to
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

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"it's the network..."                          "The Journey is the reward" 
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Reply to
Spehro Pefhany

What else do you expect from Maynard?

Reply to
Michael A. Terrell

The irony! Maynard is trying to act superior, when he was expelled from school in the first grade & never went back.

Reply to
Michael A. Terrell

Isn't Jamie one of Larkin's pimps? ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
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Reply to
Jim Thompson

You are obsessed with prostitution and impotence. Curious.

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John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    
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Reply to
John Larkin

No one claims Maynard.

Reply to
Michael A. Terrell

Larkin claims every pimp he can get. Otherwise he'd have no friends

...Jim Thompson

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| James E.Thompson, CTO                            |    mens     | 
| Analog Innovations, Inc.                         |     et      | 
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Reply to
Jim Thompson

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

Reply to
Robert Baer

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