DC-DC converter with constant current limit

[maheshjalgaonkar]

Sir,

I want to develop a DC-DC converter with constant current limit . So i choose lm 2575 which is suitable for my requirement load and line regulation . Now the question is how do i impliment current limit in It (15V/500mA). Please anyone help me .

 

[hamidmoallemi]

hi

you can use LM317 , refer to its datasheet from ON semiconductor or National semiconductor

 

[goldsmith]

Sir,

I want to develop a DC-DC converter with constant current limit . So i choose lm 2575 which is suitable for my requirement load and line regulation . Now the question is how do i impliment current limit in It (15V/500mA). Please anyone help me .

Hi maheshjalgaonkar
As you can see in datasheet of LM2577 , there is a pin which has been called on/off pin . if you tie a resistor from it through the input then the IC will be turned off , so you can easily implement hiccup current limiting with that . it means take a sample from out put current via a low value resistor like 0.1 ohm and then apply it into a comparator and compare it with 0.05 volt , and then try to use a simple BJT or mosfet ti turn off and on it via a command signal which comes from the comparator and then it will enforce the on / off pin to be high or low so the current will be easily limited .
Best Wishes
Goldsmith

 

[maheshjalgaonkar]

Thanks for giving answer i tried with ON/OFF pin but its behavior is strenge. So now i selected mc33063 IC.

 

[goldsmith]

i tried with ON/OFF pin but its behavior is strenge

Hi again
What do you mean it is strange ? i've used this method for many times and without any problem . can you tell me what happened when you used this method ? and how you used this method ?

Best Luck
Goldsmith