Author Topic: Is 1n4148 suitable for bootstrap diode application?  (Read 1121 times)

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Offline hbozyqTopic starter

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Is 1n4148 suitable for bootstrap diode application?
« on: May 28, 2023, 05:01:50 am »
Just as title. I'm trying JLC SMT pre-assemble service and for saving money I'm going to use basic parts only.
For my application I got some N-MOS half bridges and now a bootstrap diode should be choose.
The bus voltage is 60V max and switching frequency is less than 50khz.
I got two choice: US1M(1.7V@1A 75ns) or 1N4148WS(1.25V@150mA 4ns).
The first one is fine for I had use it before, but its footprint is a bit too large.
So I wonder if 1N4148 is capable for my application, seems like the main issue could be its relatively small current capacity.
Any suggestions? Thanks in advance. :)
 

Offline Terry Bites

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Re: Is 1n4148 suitable for bootstrap diode application?
« Reply #1 on: May 28, 2023, 06:27:51 am »
Read dis
 

Offline Vovk_Z

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Re: Is 1n4148 suitable for bootstrap diode application?
« Reply #2 on: May 28, 2023, 06:34:40 am »
The bus voltage is 60V max
I don't clearly understand what your circuit is but you may want consider peak reverse voltage too. It may be 2x-3x bigger of an input voltage so 100V rated 4148 (4448) may feel not good.
« Last Edit: May 28, 2023, 06:36:54 am by Vovk_Z »
 

Offline hbozyqTopic starter

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Re: Is 1n4148 suitable for bootstrap diode application?
« Reply #3 on: May 28, 2023, 07:06:51 am »
Let me clarify it. The circuit is like this.


BTW I found this:
The chosen bootstrap diode (DBS) should be rated higher than the maximum rail voltage since the diode must be able to block the full rail voltage and any spikes seen at the VS node.   The diode‚Äôs current rating is simply the product of total charge (QT) required by the HVIC (High Voltage Integrated Circuit) and the switching frequency.   An ultrafast recovery diode is recommended to minimize any delay of charging the CBS cap. A 1A ultrafast recovery diode is typical for DGD2103M applications.(Diodes, AN1154)

So I guess 75V will be fine? Using a very high voltage rating diodes will no be really helpful for MOS will break down first.
 

Offline David Hess

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Re: Is 1n4148 suitable for bootstrap diode application?
« Reply #4 on: May 28, 2023, 08:14:36 am »
The 1N4149 is higher current than the 1N4148.  The BAV20 or BAV21 is higher voltage but still pretty fast.  There is probably some bipolar transistor collector-base junction which would be better than either, but they would need to be qualified for recovery time.

 

Offline T3sl4co1l

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Re: Is 1n4148 suitable for bootstrap diode application?
« Reply #5 on: May 28, 2023, 01:50:14 pm »
Fine on average current to most bootstraps, but the catch is pulsed current.  I would want to see a 10 ohm series resistor with the diode.  And, if that configuration gives adequate charge time and average output current/voltage, then that will do.

Tim
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Offline hbozyqTopic starter

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Re: Is 1n4148 suitable for bootstrap diode application?
« Reply #6 on: May 28, 2023, 03:33:49 pm »
Thanks. Definitely will try it.
 

Offline hbozyqTopic starter

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Re: Is 1n4148 suitable for bootstrap diode application?
« Reply #7 on: June 03, 2023, 12:45:05 am »
Tried this in the field, using a 10 ohm series resister with 1n4148ws, the circuit work as expected without issue. :-+
 
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