Circuit to limit capacitor power draw

  • Thread starter capthook
  • Start date
13
0

Main Question or Discussion Point

Hello all!

Circuit to limit power draw from capacitor?

I want to limit my 100,000 uF 35 V capacitor that is charged (via schottky full-wave bridge) to between 4V to 16 V from dumping it's charge all at once.

I would like the capacitor to provide 300 mW to the load (10 ohm resistance). (ie. 1.25v @ .24A ) What do I need to do?

I could put diodes in between the capacitor and load for voltage drops - but the capacitors charge will vary from 4V to 16V..

I want to maximize efficiency.

Should I be looking at a switch mode DC/DC converter? Like this product?

LT1933 - 600mA, 500kHz Step-Down Switching Regulator in SOT-23

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1032,C1064,P7531#featuresSection

Is this the type of circuit component I should be searching for to accomplish this?
Advice on implementing this?
I'm a bit over my head on this..

Thank you!

CH
 
Last edited:

Answers and Replies

berkeman
Mentor
56,063
6,122
Hello all!

Circuit to limit power draw from capacitor?

I want to limit my 100,000 uF 35 V capacitor that is charged (via schottky full-wave bridge) to between 4V to 16 V from dumping it's charge all at once.

I would like the capacitor to provide 300 mW to the load (10 ohm resistance). (ie. 1.25v @ .24A ) What do I need to do?

I could put diodes in between the capacitor and load for voltage drops - but the capacitors charge will vary from 4V to 16V..

I want to maximize efficiency.

Should I be looking at a switch mode DC/DC converter? Like this product?

LT1933 - 600mA, 500kHz Step-Down Switching Regulator in SOT-23

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1032,C1064,P7531#featuresSection

Is this the type of circuit component I should be searching for to accomplish this?
Advice on implementing this?
I'm a bit over my head on this..

Thank you!

CH
Yes, you should use a "Buck" DC-DC converter to make your regulated output voltage. The DC-DC can also supply the current limit function that you mention.
 
13
0
Thank you for your reply!

I'm glad to have validation for the process I was considering. I have decided to go with one of the LT chip models.

FYI: Anyone that needs a SPICE program - LT offers a free/excellent one @:

http://www.linear.com/designtools/software/switchercad.jsp

CH
 

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