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Problem regarding voltage regulator.

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beckhamho

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Hi Guys,

I am using LM 2575 HVT 5.0 as the step down voltage regulator from 12v to 5v.
below is the schematic that i used.


The problem is the inductor are very hot. It cause the LCD not function properly.
What i need to do?
 

Did you calculate the inductor value, and purchase a high quality type, as specified on page 15 of the data sheet?
 

Hi,
The problem is that the duty cycle is too high I.E the voltage exists on the inductor for a long time and the current in the inductor will increase linearly till it is limited only by the series resistance of the inductor which is low I.E the current inside the inductor is high that is why it gets hot, lower it by reducing the capacitor at the output and this will reduce the duty cycle and will increase the frequency of your switching regulator.
 

Hi,
For a 12v to 5v setup, what is the duty cycle that you get? What kind of inductor and it's rating you use?
 

How much current does the circuit draws?
 

The inductor needs to be rated for the full output current you require (1 amp max for this IC) plus say 20% for the switching ripple - if the DC resistance is too high or the choke is not designed for the load current you are trying to get, then it will get too hot.
Unfortunately the comment below
The problem is that the duty cycle is too high I.E the voltage exists on the inductor for a long time and the current in the inductor will increase linearly till it is limited only by the series resistance of the inductor which is low I.E the current inside the inductor is high that is why it gets hot, lower it by reducing the capacitor at the output and this will reduce the duty cycle and will increase the frequency of your switching regulator.
Click to expand...
isn't quite correct, changing the value of the output cap will not affect the duty cycle of operation, or the frequency of operation of this IC (only at very light loads will the duty cycle reduce), Regards, Orson Cart.
 
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