Calculate Value of Cboost & Leakage Current

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Discussion Overview

The discussion revolves around calculating the value of the bootstrap capacitor (Cboost) and understanding the leakage current associated with it, specifically in the context of using a high side driver IC. Participants are exploring the theoretical and practical aspects of this calculation, including the impact of load capacitance and clock rate.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant inquires about determining the bootstrap capacitor leakage current while using a high side driver.
  • Several participants request a schematic or figure to provide more accurate assistance, indicating that visual information is crucial for troubleshooting.
  • Another participant notes that the output voltage (HO) is zero despite applying a 15V supply and a 5V pulse, expressing a need for clarification on achieving the expected output.
  • There is a repeated request for the specific chip being used and its datasheet, which is seen as essential for further analysis.
  • One participant suggests that the value of the boost capacitor is dependent on the output load capacitance and clock rate, indicating a need for more data to make accurate calculations.
  • A reference to an application note (AN-1123) is provided, which outlines the procedure for calculating Cboost, but emphasizes the need for the part number of the driven MOSFET/IGBT gate to determine total gate charge (Qtot).

Areas of Agreement / Disagreement

Participants express a consensus on the necessity of providing complete information for effective assistance. However, there is no agreement on the specific calculations or the implications of the parameters discussed, as multiple viewpoints and uncertainties remain regarding the bootstrap capacitor and its associated leakage current.

Contextual Notes

Participants highlight limitations due to insufficient data, such as the lack of a specific part number for the driven MOSFET/IGBT gate, which affects the ability to calculate total gate charge (Qtot). The discussion also reflects varying levels of understanding and the need for additional context to resolve the issues presented.

billy fok
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currently am using high side driver and i need to calculate the value of Cboost.
may i how i determine the "Bootstrap capacitor leakage current".
 
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Show a figure or a schematic, otherwise we cannot answer.
 
Svein said:
Show a figure or a schematic, otherwise we cannot answer.
I hope that i have attached the right schematic. I apply 15v to Vcc and 5v pulse to IN.
when i measure HO is zero. but i need to have 15V output from my HO. hope you are able to help me
 

Attachments

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    driver.png
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so what is the chip ?
what does its datasheet say about it's use ?
post a link to the datasheet

Dave
 
Baluncore said:
This appears to be a continuing problem of insufficient data.
https://www.physicsforums.com/threads/working-of-driver.805987/#post-5059370

The chip is probably still the IRS21850S, SINGLE HIGH SIDE DRIVER IC.
The value of the boost capacitor will be dependent on the output load capacitance and the clock rate.

ah hah :rolleyes: :smile:

Billy fok
some advice ... if you want people to help you and give your good answers
You really have to please start supplying ALL the information in your posts
none of us are mind readers :wink:

regards
Dave
 
The procedure for calculation of Cboost can be found in IR application note AN-1123.
http://www.irf.com/technical-info/appnotes/an-1123.pdf

See pages 9 through to page 12, where Cboot > Qtot / Vdrop.
We do not know the part number of the driven MOSFET/IGBT gate so we cannot know Qtot, the total gate charge.
 

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