Okay, I'll grant that the LM723 has been around for quite a while. Is there a similar, newer device that will do a better job for me This is a 22 volt, 10 amp, low ripple power supply. I've attached an article with schematic that I have built. It works reasonably well but even with 10,000 mf filtering, I'm still getting about 0.5 volts of ripple at 8 amps output.
There are *many* newer chips. You might consider a switchmode pre-regulator followed by a linear regulator for the best thermal efficiency combined with reduced high frequency noise.
I suspect you mean 10,000uF (10mF)
Getting that much ripple suggests to me that the regulator is either *very poor* or the input voltage is sagging under load.
I would take a close look at the input voltage waveform.
Also, I've played with the current limiting section (thanks for the help) by using a high quality multi-turn pot and monitoring the voltage across the current sensing pins. Sure enough when it reaches about 0.6 volts, the output starts to drop rapidly. However, when I reduce the load, the output doesn't come back by itself. Is this normal?
If you have managed to create a foldback current limit then this can happen, but it shouldn't from what I see of your circuit.
I notice that at full load, the 0.1 ohm emitter resistors don't get particularly warm, but the two paralleled 0.47 ohm current limit resistors get hot as hell. Is this expected?
Let's assume that full load is 8A through 4 transistors. So each of those 0.1 ohm resistors has 2A flowing through it for a total power dissipation of 0.4W per resistor.
Now, each of the 0.47 ohm resistors have 4A flowing through them, leading to a power dissipation of 7.52 watts each. So they are dissipating about 20 times the amount of power. No wonder they get hotter.
Finally, I'd like to test the "short circuit robustness" of this circuit, but I'm hesitant to just short the output. any suggestions?
The first thing to do is to get a heavier and heavier load until you observe the power supply going into current limiting.
Then, whilst carefully monitoring the temperature of the output transistors, increase the load and monitor both the output current and voltage. You should notice the output voltage fall and the current remain close to constant.
Your output transistors will start to dissipate seriously large amounts of heat, so stop if the case temperature exceeds some safe value.
On a power supply like this, a friend of mine had a thermistor attached to the pass transistor which pulled the current limit low if a preset temperature was exceeded.
Another issue with the 723 is that it is seriously limited in power dissipation and this generally limits the output current to a relatively small value. You may find that the 723's output current needs to be monitored to ensure that you don't exceed this at maximum current and minimum voltage -- during short circuit conditions this is the worst case.
Well, anyway, if there is a better LR and circuit that I should be using, I'd like to know about it. Or, if there are some improvements to this existing circuit, that'd be cool, too. Thanks.
Most modern regulators are more rugged in that they have some sort of over temperature and over current protection. The 723 comes from the age of steam electronics and I would suspect that its performance is probably not up to par compared to current designs (most of which are a *lot* simpler to use).
What you might choose to use depends a great deal on what you want from your power supply.
Check out this
for an example of the process you might go through.