# Need help with voltage regulator circuit

Discussion in 'The Projects Forum' started by nilimpa, Mar 9, 2009.

1. ### nilimpa Thread Starter New Member

Mar 9, 2009
1
0
Hi guys, I need help with a circuit.

My boss asked me to design a voltage regulator circuit these parameters:

Input: 32V to 40V DC
Output: 24V regulated DC
Current: 1A

Apparently the L7824 IC was not able to sustain 1A of current. The application is for an audio amplifier of some sort.

I have no idea how to design a regulator circuit. The only types I've learned in school is those using the L78xx series. No idea how to do it any other way.

Could anyone point me in the right direction regarding the basics of designing this kind of circuitry? Thanks.

2. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
I suspect your biggest problem with the 7824 was heatsinking. Bet it got pretty hot. How stable does this voltage have to be? What I mean is, if it is 24V with 10ma, and 24.7V with 1A, does this present a problem?

There is a way to boost the current capacity of any 3 terminal voltage regulator by adding a transistor. The problem is you leave the short circuit and overtemp protections behind, but the current gain is significant. Look at the datasheet of these devices to get some examples.

Here is an example:

http://eu.st.com/stonline/books/pdf/docs/2143.pdf

Most likely you didn't have adequate heat sinking, and the device went into thermal shutdown (a feature, not a bug). You might double check this.

3. ### mik3 Senior Member

Feb 4, 2008
4,846
63
If you didn't use a heat sink the LM7824 got hot and turned off automatically. Use a quite big heat sink (if you don't know how to calculate the size) and try it again.

4. ### Skeebopstop Active Member

Jan 9, 2009
358
3
Thermal pads can often do the trick as well, assuming you have the appropriate ground planes and vias. You'll have to do the maths on the power dissipation in the IC from 40V to 24V. That is a pretty big jump if it is a linear regulator!

I agree that an output buffer may be your best bet if heatsink is too expensive or bulky.