Here's the MOSFET version .............
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hahacool!
but wait. do you know how to fix the problem with my circuit? i mean. without that monster thing.............
thnks!

Of course I do. But you're in very good hands and there's too many cooks in the kitchen.

 

R1 from 0.2 ohms to 200 ohms.
do you know how to fix the problem with my circuit? i mean. without that monster thing.............

R1 is probably the resistance of the wire in the transformer. Do not play with that. It just makes heat.
1) Change the value of D5 to change the output voltage. Vout2 is VD5-0.7V. Do you know why?
2) You change the value of Vout by changing the turn ratio of L1:L2.
You need some voltage across Q1C-E. (example: Vout has ripple in the 55 to 65V range, then Vout2 could be 50V) This way the lowest point of Vout is above Vout2 by a little.
If Vout is very large and Vout2 is low then you have too much voltage across Q1 and heat is (voltage across Q1 X current out).

School: How do you lower the voltage at Vout? Hint 400m/25m is not the turn ration.
Ask questions.

 

R1 is probably the resistance of the wire in the transformer. Do not play with that. It just makes heat.
1) Change the value of D5 to change the output voltage. Vout2 is VD5-0.7V. Do you know why?
2) You change the value of Vout by changing the turn ratio of L1:L2.
You need some voltage across Q1C-E. (example: Vout has ripple in the 55 to 65V range, then Vout2 could be 50V) This way the lowest point of Vout is above Vout2 by a little.
If Vout is very large and Vout2 is low then you have too much voltage across Q1 and heat is (voltage across Q1 X current out).
View attachment 241976
School: How do you lower the voltage at Vout? Hint 400m/25m is not the turn ration.
Ask questions.

ok thnks . I already changed the value of the zener diode and R3, as you can see in the circuit that I added so that there is not such a large current in the zener diode, and now I have the 30V that I needed. what continues to generate doubts is the transformer. in the circuit I have one of 400mh: 25mh. but in online markets I don't know how to look for them, on this website
(https://ar.mouser.com/Power/Transformers/Power-Transformers/_/N-8u9n5) you can select the transformers from the primary and secondary voltages. But when I select the 300V that I have in the primary, according to the ltspice measurement, there is no secondary voltage of approximately 70v on the page, which is what ltspice measures. i mean there is no such thing as 300V: 70V, how can I solve this? I also do not know if the value of the resistance that appears in this table(https://ar.mouser.com/datasheet/2/177/197-2256148.pdf) it is R1 in my circuit.
tnhks!

 

You need a transformer with an AC Output Voltage of 24-Volts.
24-Volts will be the RMS-Voltage, the Peak-Voltage will be 24V X 1.4 = 33.6V.

Since you need 30VDC, and the Peak-AC-Output-Voltage is only 33.6V,
you will need a Transformer that has a substantially higher Current-Capacity than your Load.
Your Load is ~2-amps @ 30V, or around 60-watts.
The Average Voltage your Transformer is supplying is 24VAC, and the Peak is 33.6V,
so you must draw heavy current during each small percentage of a Voltage-Peak
to average out to ~2-Amps.
The Transformer has to be capable of supplying 2 to 3 times your required Current
during those short Voltage-Peaks, to charge a HUGE Capacitor.

I'm too lazy to do the Math,
so I'll just estimate that you'll need at least a 100VA (~100-Watts ) Transformer.
The other alternative, is to go to the next higher standard AC output Voltage,
which will probably be 48VAC.
But this creates a problem,
since you are using a Linear-Regulator, you must dissipate all that extra Voltage as Heat.

The other alternatives are either a custom Toroidal-Transformer, or a Switching-Regulator.
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Of course I do. But you're in very good hands and there's too many cooks in the kitchen.

People here are the best and very eager to help.

This may create the alluded “too many cooks in the kitchen” scenario.
Which sometimes can overwhelm a newbie with too much information.

 

thnks for the answer!
do you guys know what transformer exactly do I need? In online stores the relationship of mH does not appear, in my case it would be 400mH: 25mH and 0.2ohms, but I don't know how to look for it in online stores. by the way, Vsec is 76V maximum voltage
thnks!

 

DigiKey 237-1341-ND ~$41.oo
Triad Magnetics
230VAC Primary,
Secondary Full Load Voltage = 36VAC, (~50-Peak-Volts when Rectified ),
Secondary Maximum Rated Current = 2.78-Amps,

With a Linear-Voltage-Regulator you will have to
"Burn-Up" 20-Volts, at 2-Amps, 20V X 2A =40-Watts of Heat, that's a BIG Heat-Sink.

If you use a "Buck-Regulator" the Heat generation will be much lower.
DigiKey LT1170HVCT#PBF-ND ~$19.oo
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Or, you can buy a complete SMPS Power Supply for ~$40.oo, ( not Chinese junk ),
which only Dissipates 6-Watts of Heat under Full-Load, and is just 2" X 4" X 1" in size.
DigiKey 1470-LCE80PS30-ND
Adjustable, 30V Regulated-Output, at up to 2.6-Amps, with 90%-Efficiency.
Accepts ~90 to 305-Volts Input, and the Output is Isolated from the Mains.
But it doesn't come with a Box, you'll have to get one to make it safe.
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