I putan adjustable stabilizer scheme.The output voltage can be changed from 5volts to 300volts.Note the powe transistor!

 

That circuit won't work since the input voltage to ground maximum voltage rating of the LT1129 will be exceeded when trying to go above 30V output.

A neat trick shown in some appnotes is to casc_o_de a high voltage power MOSFET on the SW output of several varieties of integrated switcher.

The underscores are because the resident spellcheck changes casc_o_de to cascade.

 

Below is the LTspice simulation of Bordodynov's basic circuit using a TL431 as the regulator control, modified with some added components for proper bias and frequency compensation, and a current limiter.
I didn't have the model for the IRF840 so I used an alternate, but the circuit should work essentially the same with the 840.

Q1 turns on to starve the gate voltage to M1 and limit the current when the voltage drop across R4 reaches about 700mV.
The current is limited to about 220mA, as can be seen after 5ms when the output is shorted by S1.

The output is shown for minimum, midrange, and maximum position of pot U2 for a 200mA load.

Note that the power dissipated in transistor M1 can get quite high at low output voltages and a 200mA load or a short so you would need a healthy heat-sink for operation under those conditions.

 

crutschow. I found your circuit with an obstacle at the entrance. The result of the operation of your electronic circuit. Very bad!


But my electronic circuit with protection:

 

Note that I replaced the scheme.
Now I am applying input 310Volt and output is 305 volts.The value of the reference voltage equal to 2.5volts.
Equivalent:

View attachment 87547

Ah, thank you. I found the data sheet for the TL431. I have not used LTspice as I found multisim to be far more intuitive.. for me anyway.

 

Below is the LTspice simulation of Bordodynov's basic circuit using a TL431 as the regulator control, modified with some added components for proper bias and frequency compensation, and a current limiter.
I didn't have the model for the IRF840 so I used an alternate, but the circuit should work essentially the same with the 840.

Q1 turns on to starve the gate voltage to M1 and limit the current when the voltage drop across R4 reaches about 700mV.
The current is limited to about 220mA, as can be seen after 5ms when the output is shorted by S1.

The output is shown for minimum, midrange, and maximum position of pot U2 for a 200mA load.

Note that the power dissipated in transistor M1 can get quite high at low output voltages and a 200mA load or a short so you would need a healthy heat-sink for operation under those conditions.

View attachment 87572

What about paralleling 2 IRF840s for M1 to share heat dissipation for low voltage hi current situation?

Also, if M1 failed for some reason during a dead short (Low voltage Hi current) across the output of the circuit, would that not render the current limiting useless?


Is there a way to implement current limiting that does not rely on the pass IRF840 being being functional?

Finally, thanks for all your help!

 

What about paralleling 2 IRF840s for M1 to share heat dissipation for low voltage hi current situation?

Also, if M1 failed for some reason during a dead short (Low voltage Hi current) across the output of the circuit, would that not render the current limiting useless?

Is there a way to implement current limiting that does not rely on the pass IRF840 being being functional?
....................

You can parallel two MOSFETs to distribute the heat but you still have the same total amount of heat to dissipate so it doesn't affect the heat sink requirements.

You could add another MOSFET with the NPN transistor limit circuit, in series with the control MOSFET with its own limit.
That would give two (redundant) limits. But then you would likely also need to add some additional circuitry to warn if one of the limits failed. Otherwise you wouldn't know.

 

You can parallel two MOSFETs to distribute the heat but you still have the same total amount of heat to dissipate so it doesn't affect the heat sink requirements.

You could add another MOSFET with the NPN transistor limit circuit, in series with the control MOSFET with its own limit.
That would give two (redundant) limits. But then you would likely also need to add some additional circuitry to warn if one of the limits failed. Otherwise you wouldn't know.

Thank you everyone, your help is very much appreciated.
I will try to make a few changes and post the result.

I am in need of some good books. Any suggestions please?

 

crutschow, You ignored my remark on your electronic circuit. Maybe it's my fault and I'm not very detailed description of my experiment with your circuit. I'm sorry. Your electronic circuit is very bad. I knew it was worse than mine, but not enough. This is the advantage of using transistors with built-in channel. The input ripple amplitude I asked 15 volts and a frequency of 100 Hz (SINE(300 15V 100 1m)). Your electronic circuit output voltage ripple gave 7 volts, and my 0.0005 volts. I would like to hear comments.

 

crutschow, You ignored my remark on your electronic circuit. Maybe it's my fault and I'm not very detailed description of my experiment with your circuit. I'm sorry. Your electronic circuit is very bad. I knew it was worse than mine, but not enough. This is the advantage of using transistors with built-in channel. The input ripple amplitude I asked 15 volts and a frequency of 100 Hz (SINE(300 15V 100 1m)). Your electronic circuit output voltage ripple gave 7 volts, and my 0.0005 volts. I would like to hear comments.

Since I don't have any idea what you are talking about I can't comment further.

 

I took your circuit that you have attached (TL431 HV Regulator.asc), and decided to investigate the suppression of fluctuations of the bridge rectifier. Simply show a picture. Look

 

crutschow, You ignored my remark on your electronic circuit. Maybe it's my fault and I'm not very detailed description of my experiment with your circuit. I'm sorry. Your electronic circuit is very bad. I knew it was worse than mine, but not enough. This is the advantage of using transistors with built-in channel. The input ripple amplitude I asked 15 volts and a frequency of 100 Hz (SINE(300 15V 100 1m)). Your electronic circuit output voltage ripple gave 7 volts, and my 0.0005 volts. I would like to hear comments.

Hi, 300VDC in, 15VAC ripple, 100Hz = T 0.01/sec..... but at what current?

 

I took your circuit that you have attached (TL431 HV Regulator.asc), and decided to investigate the suppression of fluctuations of the bridge rectifier. Simply show a picture. Look

Okay, I see what you are saying. The circuit does not have much suppression for any input ripple.

The ripple rejection can be greatly improved by adding a 1uF cap from M1's gate to ground and reducing the value of compensation capacitor C2 to 1nF.

 

G.Beard.
ILoad=0.2
Crutschow
The ripple rejection (Cg=1uF, C2=1nF) Kr=30V/0.557V=54. My new cirquit (+10nF) Kr=30V/0.000172V=174418.
Congratulations! You have created a disposable stabilizer. The second time the regulator will not start. But it's easy to fix. Also no-load voltage and full load differ by 4 volts. I have done other studies (comparison) our regulators.
I later add a file to my research of my and your stabilizer.
By all accounts, my stabilizer greatly exceeds yours. But your stabilizer consists of the common components. But if you want to get a high quality stabilizer, use my electronic circuit. The truth is it will be much more expensive.

 

I'm not the first who used the TL431 and two transistors with built-in channel. I found the file "270V Reg Mike.asc" in LTspice Yahoo Group. This stabilizer on two transistors dn2540. Its parameters ILoad=100mA Vout=270V. The scheme is different from mine, there is no short-circuit protection, but the idea is the same.
And I found flaws in this scheme.

 

Here is my electronic circuit. I also give the calculation (Test with different conditions) my circuit and alternative to LTspice.

 

So, would we then reference the adj pin to a fixed rail x amount more positive WRT ground or use resistor between adj and 0v to elevate the output to a desired voltage, or inject a voltage to the adj pin?

How would one adjust the output over a range greater than 48V? Could this be done maybe by having a pre-regulated variable voltage and..... not sure of the correct terminology... float the LM317 on the varied output of the adjustable voltage?
How would one connect an LM317 (at high voltages) to a circuit without the 48V rating being exceeded?



What voltage is the zener diode?
I can see you are using depletion mode MOSFETs so I should think that when the circuit is initially powered the M1 is fully on, R1 and R2 make up a voltage divider and R4 or R1 set the current flowing through the zener which provides a reference voltage which then raises the gate voltage to M1 and the circuit would stabilise at 120V. I this correct? Would you give a brief explanation of your schematic and correct me where needed please?


Here is a NON-regulated circuit from rod elliott's site that I modified slightly for higher current and lower ripple.
The zener does no appear to be conduction in the zener breakdown region, the zener device was not specified, nor was there any explanation as to what this zener is doing in the circuit. Any input would be greatly appreciated.

Again, thank you all for taking the time to reply View attachment 87539

The circuit is a transformerless power supply which is not allowed and violated with the TOS, if you continuing to discuss this kind of circuit then the thread will be closed.