Easiest circuit design for a LT1076-5 Step-Down Regulator

[kittydog42]

I am looking for the easiest circuit for this device. I would like to try to do this without an inductor if possible due to space. My input voltage will be 24VDC and the regulator I am using has a fixed 5VDC output. Any ideas as to how?

 

[audioguru]

The LT1076-5 is a switching regulator. Its circuit needs to have an inductor.

Use a linear regulator like a 7805 that works without an inductor. But since your input voltage is so high it will probably get too hot and will need to have a big heatsink if your circuit uses a fair amount of current.

 

[Hero999]

What current do you require?

If it's only 50mA then I wouldn't worry about a switching regulator.

If you want low currents <500mA then check out this website for a simple discrete switching regulator.
https://www.romanblack.com/smps/smps.htm

 

[justDIY]

if you've got a good sized pocket book, this might be an option:

https://dimensionengineering.com/DE-SW050.htm

 

[kittydog42]

I require about 220mA. I am currently using a C&D Technologies NME2405D, which costs around $11. The cost is one issue, and the 1W rating is the other, since I am a little over it. The plus is that it is very simple to incorporate, but the minus is that it is overloaded, and that the part is not a standard form factor.

 

[Hero999]

220mA?
Then you're better off using the design from the website I linked in my previous post.

Cheaper and just as effective.

You need to drop the requirement for not having an inductor though. What's so bad about inductors? You can't build a decent switching power supply without one so buy one if you don't fancy winding your own.

https://www.romanblack.com/smps/a02.htm

+15v -------*-----------------*--------,
            |                 |        |  Q1
            |        470 ohm  R1       |  PNP
            |                 |        E  BC327
      8k2   RZ                *------B
            |                 |        C
            |                 |        |          (measured:)
            |            2k7  R2       |   470uH  (460uH, 0.7 dc ohms)
            |                 |        |
            |      NPN BC337  |        *----L1-------*------ +5v out
            |                 C  Q2    |             |
            *----*----*-----B          |             |
            |    |    |       E--------|-------------*
            |    |    |                |             |
            |    |    |                |             |
            |    |    '------C2--------*             |
     zener  |    |           2nF       |             | 47uF
      ZD1   -    |                     -             C 16v
     5.6v   ^    C1                    ^ D1  1A      |
    400mW   |    |                     | schottky    |
            |    | 6.8nF               | 1N5819      |
            |    |                     |             |
Gnd --------*----*---------------------*-------------*------ Gnd

 

[gramo]

If you could get hold of a 12/15V plug pack, then the 7805 is great, and cheap ($0.25 from www.futurlec.com)

Perhaps use a 5W wire wound resistor available from www.futurlec.com to step down the input voltage

Although rated for 5W, driving them at 2 Watts will still produce a lot of heat, but you can drive your loads up to 300mA dissipating only 1/2 Watt over the 7805 (Power is calculated by V * I)

Using two 33 ohm resistors means that half the heat can be dissipated on each resistor

 

[gramo]

The whole cost of the above circuit (2 * 33 ohm 5W resistors & 7805T) = $0.65

 

[kittydog42]

I don't know if I have the space for the 5W resistors. I have a 7805 set up with a heatsink and that is too big as well. I could get the LT1076-5 to work with an inductor, but it seems to take up too much space for my application.

One question about inductors - can I use any type, such as an axial or radial inductor that would resemble a capacitor in appearance?

 

[Hero999]

You have a space limit!

You should have made that clear in your original post.

Anyway, what's wrong with my suggestion, or anyone else's suggestion?

 

[audioguru]

If your 24V input is reduced to 8V then a 7805 won't need a heatsink since it would dissipate only 660mW. But with 24V as its input it must dissipate 4.2W and need a pretty big heatsink.

 

[kittydog42]

You have a space limit!

You should have made that clear in your original post.

Anyway, what's wrong with my suggestion, or anyone else's suggestion?

True.

I don't really have a rigid space limit, but the size of my finished product will mostly be determined by how large the power component is.

 

[kittydog42]

Would something like this work for an inductor? I need thru-hole mounting.

https://www.electro-tech-online.com/custompdfs/2007/04/768.pdf

 

[Hero999]

Which inductor

In what circuit?

Take care to pay attention to the current rating.