Electronics > Projects, Designs, and Technical Stuff
723 psu issue
m3vuv:
hi any schematics of an example i can try?,cheers m3uv.
xavier60:
--- Quote from: m3vuv on December 13, 2018, 12:51:23 am ---hi any schematics of an example i can try?,cheers m3uv.
--- End quote ---
I have been submitting the results of a design that is being tested on another thread.
The big test will be when I commit the design to a PCB. I won't say much more until it's done.
The original , https://dangerfromdeer.com/tag/power-supply/ , doesn't work properly.
coromonadalix:
normally if you add an power diode in serial or the sensing resistors, you'll get more voltage to control your current limitter, but you will lose more voltage at the output
To negate this, you have to put the current control circuit before the power outputs collector. That way the lm723 is managing / regulating the voltages fluctuations better, and you have less voltages drop at the output.
See the attached photos for an example, i think the l146 can be subbed by the lm723
I have an very old lm723 design similar to this, but have more parts in the current limitter section, i cant find my schematics anymore, it use the foldback regulation technique.
It can drive leds down to 10-20 ma ... up to many amps ...
You have the same applicable principle to the 3 legged variables regulators too ..
coromonadalix:
oh and check this attached photo for negating the minimal 1.2 volt minimum at the output, the lm723 internal design will never get to 0 volts at the output.
Kleinstein:
The circuit with the negative supply to get an output voltage down to zero has 2 serious drawbacks:
1) the reference voltage is now to a large part the external zener diode to stabilize the negative supply - this would likely be rather poor quality compared to the usually rather good 723 internal reference. In the shown circuit there would also be quite some ripple from the negative supply.
2) The negative voltage adds to the supply of the 723 - so the maximum voltage would be lower by some 5 V. The voltage to the 723 is already too high without it, if 30 V transformer is used.
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