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
    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


    Mar 24, 2008
    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:

    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
    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
    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.