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adjustable voltage and current power supply

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kesmez1

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I have just finished the power supply project.
Circuit supply can be done with 48 volt dc 150 watts smps or transformer. The circuit requires a 5 volt additional supply with 48 volts.
Mje3055 can be used instead of 2n3055. This transistor should be cooled with a 5 watt cooler. The 3055 transistor heats up to 5 watts maximum at each voltage in a 4 amp load current.
Voltage setting is done with 50k potentiometer and current setting is done with 1k potentiometer.
I have not yet implemented the circuit practically. I will do it. There may be a problem. Those who want to do can make the circuit. The circuit is working in a simulated environment.
The characteristic of the circuit is that it does not need a very large cooler and different supply voltages.
C3, C6 and C10 must be low esr (low impedance) type.
Extract the rar file to a folder.
You can run the ASC file with the free ltspice simulator.
The circuit is working in the high side step down topology. Pre-regulation. The goal is to produce 1.2 volts of the required 3055 emitter voltage. The 48 volt input voltage can be reduced to 40 - 45 volts. I chose it because it has a 48 volt standard smps output.
For minimum heating of the 3055, the Vce voltage had to be at a minimum. I think the best voltage is 1.2 volts. The collector power consumption of this transistor is 1.28 = 4.8 watts at 4 amps.
To make the output ampere 8 amps, we need to parallel the pair of bc 327 mje3055. I need to use 3 pairs for 12 amps. But in this case you need to increase your power in the step down section.

psupplyeb.png
 

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Without doing a full analysis, it looks like it should work but the configuration is rather unusual, referencing the output to the positive supply and generating an internal negative rail. I'm not criticizing the design but it does seem rather complicated for what it does.

Brian.
 

It does appear you are using a lot of bits to achieve an outcome that can be attained with a simpler circuit and less bits and still be rugged and operational...
 

set the output voltage to 5 volts load resistance to 2 and test the 3055 power dissipation.
You'll see it's 3 watt instead of 107 watt
 

Q4 transistor was added R20 = 2k2 bias resistance.
 

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It does appear you are using a lot of bits to achieve an outcome that can be attained with a simpler circuit and less bits and still be rugged and operational...

In relation to the intended function (adjustable constant I/V power supply with switch mode pre-regulator), the circuit isn't overly complex at first sight. I have rather doubts that it's "rugged and operational" as is. Running the simulation, I see an unstable switcher duty cycle. Setting a low constant current, e.g. 200 mA, I see massive output overshoot during turn-on. The behavior is probably due to the I/V regulator topology. I concede that designing an I/V controller with smooth transition and no wind-up isn't easy.

Regarding "high side step down" switcher topology, I recognize that it's used here for convenience, to allow a ground referenced NMOS switch in a simple 3842 current mode switcher configuration.
 
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    d123

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Hi,

In the schematic in post #1, is the op amp ground connection meant to be like that, if so what is the purpose?
 

Just be aware that the LM334 current sources, connected as they are without temp compensation, will drift around significantly with temperature.
The current changes so much that they actually make excellent temperature sensors.

I have not fully analyzed your circuit to determine whether this is a problem or not.
 
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    d123

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first lm334 constant 4 volts and 0.6 mA, 2.4 mWat
the second lm334 4 volts 1.08 ma, 4.3 mWatt.
to work in conditions.
the thermal change will be less.
 

The LT1013 offers better performance with the opamp. The collector connection of Q6 was changed.
 

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first lm334 constant 4 volts and 0.6 mA, 2.4 mWat
the second lm334 4 volts 1.08 ma, 4.3 mWatt.
to work in conditions.
the thermal change will be less.

They change will occur because of the changes in external ambient temperature. Self heating only adds up to that.

Please read its datasheet, there is a very simple way using another resistor and a diode to minimize the temperature coefficient. The datasheet shows an 1N457, but I've used common 1N4148 with reasoneable results.
 

Thank you for your suggestion. I know the diode circuit in datasheet. He can use that circuit. It would be better. I ordered materials aliexpressten. I will make the circuit when the goods arrive.
 

In message 12, the d8 diode is faulty. I am adding the file again.
 

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