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I want to use HCPL3120 gate driver:

Its data sheet is here: https://www.mouser.com/datasheet/2/678/V02-0161EN_DS_HCPL-3120_2016-03-21-908803.pdf

On page number 22 there is an excellent design for IGBT, but I didn't understand how to find the value of Rg. Also, what is the value of the resistor which is attached to the "74xxx open collector"? It is shown as a 270W resistor, which is too high!

Additional questions:

On page 23 there is a design process that he followed, but I have some questions:

  • what is VOL and IOLpeak?
  • from where did he obtain 178mW as a max output power?
  • what if my output power is less than the maximum power?
  • from where did he obtain bias output power?
  • after obtaining Esw, how can I determine how much I should increase from the resistance?
SamGibson
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محمد راشد
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  • Ω and W are common errors due to Unicode fonts when it should be ASCII or ANSI ..ASCII​​ ​​​​ कं ट?ट या ?वषय-व?तु – Tony Stewart EE75 Dec 29 '19 at 16:29

2 Answers2

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I think the "270W" marking is a problem with the fonts used in the schematic, and that this resistor should be marked as 270Ω instead. My guess is that a special symbol font was used in the schematic but a font substitution was made when the pdf was created.

The calculation of \$R_g\$ is pretty well described. You should explain specifically what you "don't get" about it.

Elliot Alderson
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  • first, what is VOL and IOLpeak , from where did he obtain 178 as a max output power , what if my output power is less than the maximum power , from where did he obtain bias output power, after obtaining Esw how can I determine how much I should increase from the resistance – محمد راشد Dec 30 '19 at 07:29
  • @محمدراشد Don't ask more questions in a comment. Add this to your original question, and specify exactly where in the datasheet you have a question. Don't make us search the datasheet for "178". – Elliot Alderson Dec 30 '19 at 15:17
  • I edited the question please check again – محمد راشد Dec 30 '19 at 16:23
  • so you don't have an answer – محمد راشد Jan 01 '20 at 07:00
  • I am sorry that the demands of my own life interfered with the time I had available to read the datasheet for you and provide free engineering consultation. I'm sure by now that you have it all sorted out. Best of luck with your project. – Elliot Alderson Jan 01 '20 at 14:26
  • No I didn't get it yet – محمد راشد Jan 02 '20 at 10:48
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The 270W is a typo in the datasheet, this should be 270Ω

As to the gate resistor. This would be outside the scope of the gate drive chip because it is heavily influenced by the gate you are driving and under what conditions: The gate capacitance.

To calculate the value (and the wattage) of the resistor, please consider the information in this post: what the best way to calculate Rg gate driver for Mosfet

Identify the device you want to switch, look at the test-case Rg, follow up with sizing calculations