POWER SUPPLY DESIGN

[DerStrom8]

And This Is not just ONE File, it is Probably a Gig of data.

Most email services have a data limit of 25MB, so you're right--either send it on a CD via snail-mail or try using the skype file transfer option. However, on a dial-up connection that will take a LONG time, probably days.

 

[Willen]

My pc still uses a mechanical hard drive that takes a couple of minutes to boot. My son's pc uses a solid-state drive that boots immediately.

I never heared that there is solid-state HD exist! But I used to think that why they don't use such harddisk made from chips (like memory card) instead of Magnetic Disks. Does it boot faster like a TV ON? Amazing, all devices use memory cards as a HD like cellphones, cameras etc which is faster and less power consumer but why PC uses magnetic disk? May be it has long life..and secure for data? Does a solid-state HD cost high?

My son had a Mercedes with a V12 engine with two turbos.

I never have seen Marcedes, but I heared and read on books that rich foreigners have Mercedes Cars . May be he is a big engineer or businessman, isn't it? Can I know how much he paid for them?

 

[audioguru]

I never heared that there is solid-state HD exist!

They have a huge amount of memory so they are expensive.

I heard and read on books that rich foreigners have Mercedes Cars . May be he is a big engineer or businessman, isn't it? Can I know how much he paid for them?

My son is a car dealer. He buys and sells used cars. He bought a 2003 Mercedes at the auction for about 9,000 dollars. It was 180,000 dollars when new. He fixed it (it had a few minor problems) then sold it for about 15,000 dollars. He has had a few other Mercedes cars, some BMW cars and some Saab cars. I was happy with my old car then my son bought me a newer better car (I did not ask for it) and he sold my old car.

 

[Zerotolerance]

AMG BITURBO? Nice! CL 65 or SL 65? I'll take either

Those SL 65s and CL 65s run for $200,000+

 

[magvitron]

I'm not boasting but the internet speed here is way better. So I opt for these methods.

 

[ladyphoebe15]

I created a new one. Is this capable of my producing my desired output 0-25v and 3A with a transformer of 24v 3A.

 

[audioguru]

View attachment 84837
I created a new one. Is this capable of my producing my desired output 0-25v and 3A with a transformer of 24v 3A.

Is its voltage regulation good enough since it has no error amplifier and no negative feedback?
1) The 24V zener voltage increases when it gets warmer but the transistors' voltage decreases to cancel it.
2) The output voltage drops as much as 1V when loaded with 3A.
3) The current-limiting transistor Q1 will blow up then the 11 ohms will reduce the output voltage a lot when there is a load.
I will fix it in half an hour.

 

[audioguru]

OK, my half hour is gone, sorry for the delay.
I fixed the current limiter but the poor voltage regulation remains.

I cannot add contrast to your pastel schematic until the postman comes with a gift from Chemelec.

 

[ladyphoebe15]

Is its voltage regulation good enough since it has no error amplifier and no negative feedback?
1) The 24V zener voltage increases when it gets warmer but the transistors' voltage decreases to cancel it.
2) The output voltage drops as much as 1V when loaded with 3A.
3) The current-limiting transistor Q1 will blow up then the 11 ohms will reduce the output voltage a lot when there is a load.
I will fix it in half an hour.

I don't know how to make a better voltage regulator especially with an error amplifier and negative feedback. I can't test the circuit directly due to lack of materials so I simulate it to proteus.

 

[audioguru]

Is the poor voltage regulation of your voltage regulator good enough for your application?

There are hundreds of voltage regulator designs in Google and hundreds of voltage regulator ICs with datasheets showing schematics for them.
They all use an error amplifier with negative feedback so if a heavy load increases the output current which tries to drop the output voltage then the error amplifier senses the voltage dropping and boosts it up to normal. If the output voltage tries to go too high then the error amplifier senses it and reduces the output voltage down to normal.

When you learn about opamps then you will see how easy it is for an opamp to be an error amplifier with negative feedback. The voltage regulation will be so good that it will be difficult to measure any change in output voltage when the load current changes from zero to maximum. If a small voltage change is measured then it will probably be caused by the tiny resistance of the wire connecting the load to the regulator circuit.

Your circuit uses two emitter-follower output transistors. Your simulator program should have models for the transistors to show you how much the output voltage will change when the load current is changed. Or you could look up how much Vbe changes when Ic changes on their datasheets.

 

[ladyphoebe15]

I plan on using discrete components because it required for us to do so and prohibited to use any IC or Amplifier.

 

[audioguru]

I plan on using discrete components because it required for us to do so and prohibited to use any IC or Amplifier.

Before opamps and voltage regulator ICs were invented, many amplifiers and regulated power supplies were made with discrete parts.

 

[DerStrom8]

Before opamps and voltage regulator ICs were invented, many amplifiers and regulated power supplies were made with discrete parts.

Right, every single IC can be recreated using discrete components, it will just take up more space.

 

[audioguru]

You used common-collector emitter-follower transistors that amplify the current. Then are you also allowed to use common-emitter transistors to amplify voltage and simulate an error amplifier with them?

 

[ladyphoebe15]

what do you suggest i do with the 2 emitter-follower transistors? Should i change them?

 

[audioguru]

what do you suggest i do with the 2 emitter-follower transistors? Should i change them?

If the 24V zener diode has a tolerance of 5% then its minimum voltage is 22.8V. The Q2 emitter-follower has a maximum Vbe of 1.0V and the T1 emitter-follower transistor has a maximum Vbe of 1.5V so at 3A the minimum output voltage is only 20.3V before R3 and R4, not 25V. R3 + R4 should be a single 0.22 ohms resistor that will reduce the output voltage to about 19.6V.

Without a load the minimum output voltage will be about 21.7V, not 25V so the output voltage drops (21.7V - 19.6V =) 2.1V so the voltage regulation of your circuit is horrible.

If you make a little error amplifier with a couple of transistors with a voltage gain of 150 times then when the output current is changed from 0A to 3A the output voltage will change only (2.1V/150=) 0.014V so the voltage regulation will be very good.

 

[ladyphoebe15]

is it okay if I replace the 24v zener diode with a 27v and removing the Q1 and the 0.22 ohm? I plan to make a no-load Power Supply that will have a small change or possibly none when added a load later on.

 

[audioguru]

is it okay if I replace the 24v zener diode with a 27v and removing the Q1 and the 0.22 ohm? I plan to make a no-load Power Supply that will have a small change or possibly none when added a load later on.

1) If a 27V/5% zener diode is used then its minimum voltage is 25.7V. The maximum voltage loss of the emitter-follower transistors is 1.1V with no load and is about 2.5V with a 3A load so the minimum output voltage will be 23.2V to 24.6V and the voltage regulation is horrible.

2) Q1 and the 0.22 ohm resistor limit the maximum current to 3A. If they are removed and the output of your power supply circuit is shorted or overloaded then something will get VERY HOT and might catch on fire.

Without having an error amplifier and without negative feedback then why do you think a load will make a small change or no change to the output voltage??

 

[ladyphoebe15]

i have no background with how to make error amplifiers or negative feedback and how to connect it to my circuit.

 

[audioguru]

i have no background with how to make error amplifiers or negative feedback and how to connect it to my circuit.

An ordinary common-emitter transistor is an amplifier. Google has hundreds of voltage regulator circuits online like this one: