Maybe a Problem with 78xx regulator

[HorstHühn]

Hi,

In a simululation I found an Error while using 7812 regulator. I tried to simulate a power supply with 230VAC without transformer. I need only 10mA at the output.

After the simulation I tried to build up tis circuit in real and found out, that it doesnt work properly. I got not more than 3 Volts out of it.

Then I simulated the 7812 for itself and I found an error. It delivers under all circumstances 12.xx Volts even without a power source. I tried the other ones and found out that 7805 was working properly, all the others hat te same mistake.

Am I wrong or is there a malfunction in the models?  I am usinf the students version 13.0

Regards

HorstHühn

[n_dakota]

Hello,

Yes, it looks like incorrect behavior. Thank you for pointing it out!

[jheffernan]

Yes, I noticed the same problem when trying to simulate a power supply.  The 7805 regulator is the only one in the 78xx family that works like the real circuit.  All others have a mysterious voltage at the input when disconnected, so the output never goes to zero.  I attached a Multisim simulation to illustrate the issue.  I added pull-down resistors on all the inputs but they made no difference.

[fofango570]

"После моделирования я попытался создать эту схему в реальном режиме и обнаружил, что она не работает должным образом."
Входное напряжение стабилизатора не более 35 вольт, а вы подсунули 220!
Он вообще должен сгореть, или пробиться.