Kevin Weddle Posted January 19, 2014 Report Share Posted January 19, 2014 I changed the opamp load resistor from 100K to 200K. But of course the voltage regulation is no where near as good as the 30V Stabilized Power Supply. Quote Link to comment Share on other sites More sharing options...
audioguru Posted January 19, 2014 Report Share Posted January 19, 2014 Kevin,1) As I said before, a high voltage zener diode (yours is 28V) has poor voltage regulation and its voltage increases as it heats up. If the input is exactly 30.0V then the 10 ohm resistor feeding the zener diode has a VERY high current of 2V/10 ohms= 200mA (minus 23mA in the pots). Then the zener must dissipate 177mA x 28V= 5W which is extremely hot so its voltage will increase a lot as it warms up. If the input is a little high at 33V then the zener diode must dissipate 7.8W!Use a 5.6V zener diode at a low current. It will have pretty good voltage regulation and its voltage does not change when the temperature changes. If you feed it from an active current source made with an opamp then its voltage regulation will be excellent. The output amplifier can easily amplify it to 28V.2) Why do you use TWO opamps when only one is required?3) With a 30.0V supply, if you use ordinary 741 opamps then their maximum output voltage is about +26V. The darlington output transistor has a maximum voltage drop of about 2V so the maximum output of your "28V" regulated power supply is only +24V. If the 30V has ripple then the maximum regulated voltage will be even less.4) It has NOTHING to prevent it from burning up if the output current is too high or if the output is shorted. Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted January 24, 2014 Author Report Share Posted January 24, 2014 The 1-25volt power supply design is a better one. Quote Link to comment Share on other sites More sharing options...
audioguru Posted January 24, 2014 Report Share Posted January 24, 2014 The 1-25volt power supply design is a better one.Your 1-25volt power supply design is exactly the same as this 28V one with the same problems. Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted January 25, 2014 Author Report Share Posted January 25, 2014 Yes it makes little sense. Because the potentiometers set the output voltage. Quote Link to comment Share on other sites More sharing options...
audioguru Posted January 25, 2014 Report Share Posted January 25, 2014 Why don't you fix it? Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted January 26, 2014 Author Report Share Posted January 26, 2014 I'm satisfied with the design. It's not perfect. Quote Link to comment Share on other sites More sharing options...
audioguru Posted January 26, 2014 Report Share Posted January 26, 2014 I'm satisfied with the design. It's not perfect.I am surprised you didn't fix it. It will be easy to make it work much better with fewer parts, as I explained.Will it burn down your house when it is overloaded? Quote Link to comment Share on other sites More sharing options...
audioguru Posted January 26, 2014 Report Share Posted January 26, 2014 Burn down your house with this simple circuit that will have excellent voltage regulation: Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted February 2, 2014 Author Report Share Posted February 2, 2014 Pretty. Quote Link to comment Share on other sites More sharing options...
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