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| Lab Power Supply - The Lost Current |
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| C:
First, how much have you tested this with different loads? As a lab power supply I would think you would want to connect any load to this and know how well it will try to protect the load while trying to maintain it's settings. Think of using a second copy of this as a load(shunt regulator) to test the first. The +30volt supply & 1000uf cap is your supply. Q2 & R5 is the regulator. By keeping both the same, you could use one to test the other. By making the same changes to both you improve the Power Supply use & Load use. Might also want to think of some nice future additions and make it easy to add them. One thing I have seen is using an internal known load to get more information about connected load. An additional think to think about. Do you want only the load pulling output to 0 Volts & 0 Current output. Really think about this, Say you are building/testing a circuit connected to this supply. You short something out in the circuit. Do you want all the cap's in test circuit dumping in to short or would you like the Lab Power Supply able to pull excess from test circuit. Right now you can source current, To make faster response to a lower output you would need a shunt across the output, Pull down in addition to existing pull up.. If you are going to trouble of creating a PCB, might be nice to be able to use the PCB as part of more test equipment of your test bench. If you plan ahead you can make ground loops less of a problem. |
| xavier60:
There is the concern that some combination of load reactance will make it unstable. I use another large MOSFET driven by 15Hz to cycle various loads. Besides the function of Q1, the op-amps have been applied in a rather standard way, so I'm not expecting any problem that tweaking the compensation won't fix. I had no plans to make it sink current except for a bleed resistor across the output unless I find too much overshoot when it unloads. Designs like that of Peter Oakes have the option of being controlled and monitored by a micro-controller. Every time I think about this, it adds another 4 op-amps, so I won't bother for now. |
| radoczi94:
Did you tried to tie diodes between the fet's DS? That way the CC opamp could pull down the voltage from the capacity on the output, possibly from the connected circuit too. I don't know if it's a working idea or not, just a brainfart. |
| xavier60:
--- Quote from: radoczi94 on February 23, 2018, 10:31:53 am ---Did you tried to tie diodes between the fet's DS? That way the CC opamp could pull down the voltage from the capacity on the output, possibly from the connected circuit too. I don't know if it's a working idea or not, just a brainfart. --- End quote --- If I understand properly, that would need another power MOSFET to force down the output. I'm trying to keep it as simple as practical. Even though there looks like a lot of current overshoot, it is actually much better than other PSUs. An even faster op-amp I'm expecting to reduce the overshoot further. |
| radoczi94:
--- Quote from: xavier60 on February 23, 2018, 11:17:31 am --- --- Quote from: radoczi94 on February 23, 2018, 10:31:53 am ---Did you tried to tie diodes between the fet's DS? That way the CC opamp could pull down the voltage from the capacity on the output, possibly from the connected circuit too. I don't know if it's a working idea or not, just a brainfart. --- End quote --- If I understand properly, that would need another power MOSFET to force down the output. I'm trying to keep it as simple as practical. Even though there looks like a lot of current overshoot, it is actually much better than other PSUs. An even faster op-amp I'm expecting to reduce the overshoot further. --- End quote --- No, I just tought about diodes, 2 or 3, they only open if there is a radical intervention by the CC opamp. Something like the on the schematic below. The 2 diodes on the bottom are the analog OR gate. |
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