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Scorptkd
Level 1
Level 1
First reply posted First like given First question asked

Hi,

We use and input voltage of 24V.

I am using the IDL8150/E application note to adapt the design to drive a single high-power led (12V@1.5A) for machine vision applications. 

Due to design requirements, I was going for MHz operation but using the application note formulas as soon as I go above the 600 kHz for switching frequency the inductor values go negative….

And I go from 16 uH @500 KHz to -20 uH @ 1 MHz….

What am I missing?

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1 Solution
cynic_bandera
Employee
Employee
250 sign-ins First comment on KBA 10 questions asked

Use this formula,

cynic_bandera_0-1715786252255.png

In the App note you refer I see some mistakes (somebody updated and formatted it).

I don't think 1MHz is a good idea because of switching losses, thermal management and EMI.

 

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2 Replies
cynic_bandera
Employee
Employee
250 sign-ins First comment on KBA 10 questions asked

Use this formula,

cynic_bandera_0-1715786252255.png

In the App note you refer I see some mistakes (somebody updated and formatted it).

I don't think 1MHz is a good idea because of switching losses, thermal management and EMI.

 

Yes, I understand the issues, specially the EMI,  but in normal operation the LED will be used primarily as a Flash for the camera, so it will spend 80% of the time Disconnected.

But I am working with low camera exposures times so I will have to evaluate how the illumination output flicker and working at lower frequencies will affect the image quality.

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