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want a solution for Variable O/P voltage SMPS

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maheshjalgaonkar

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sir,
I want to design a SMPS with variable O/P voltage eg. 4-30V with variable current eg. 0-3A.
So sir I am confuse which topology is suitable for this application. please suggest me some solution. And if u have any reference then please forward me.
 

It's a switch mode power supply circuit
LM2576.png
Refer datasheet of LM2576.
 

maheshjalgaonkar said:
sir,
I want to design a SMPS with variable O/P voltage eg. 4-30V with variable current eg. 0-3A.
So sir I am confuse which topology is suitable for this application. please suggest me some solution. And if u have any reference then please forward me.
Click to expand...

You can do one of 2 things:
1) For variable output voltage, adjust the duty cycle of the primary side PWM controller.
2) Have the output voltage fixed and use an adjustable switching voltage regulator.

I would say that the 2nd choice is better. If you choose choice 1, the required change in duty cycle is too large. Also keep in mind the automatic duty cycle change to compensate for line and load variations.

So, you can have a fixed output voltage greater than 30V (eg. about 40V) and use a suitable switching regulator.

Hope this helps.
Tahmid.
 
Thanks for solution but i want adjustable current also and i want linear O/P(ripple free) so i was thing to used series pass transistor to be used at O/P of SMPS so is that ok with this 2nd option. And one more thing i am considering both of this options are for flyback topology .
 

For variable output voltage, i want to adjust the duty cycle of the primary side PWM controller So i need help on this topic if u can suggest any PWM controller for this application or if it just a matter of transformer design then what will be the value i should consider while designing Transformer like Duty cycle, switching frequency, Bsat.
 

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