Simple low power 230VAC to 5VDC power supply

103

02:39:15

This circuit is designed for MCUs and low power components. You will need to tweak this according to your own peak current needs. This circuit has no idle current and therefore efficient while the system is at rest (wrong, the idle current is high, I'll fix it.). It further is capable of delivering upto about 100+mA at 5v.
The latest addition is a variable and stable voltage regulation with potentiometer.
This circuit is dangerous, since it has no galvanic isolation to the mains power. Therefore, no wires must leave the box that you plan to put this in. It is a power supply for a specific device, and not a power box. (take care) 

published 6 years ago

PrathikP

6 years ago

Replacing the zener (a shunt regulator) with an LM78XX (a series regulator) would be disastrous. With a series regulator and under no load current, there is nothing drawing current from the regulator, because of which the rectifier would charge up the capacitor to the peak of the mains voltage. First, the regulator would blow up. Then, the capacitor. It is imperative to use a shunt regulator as it keeps discharging the capacitor even under no load, preventing over-voltage and a subsequent explosion

PrathikP

6 years ago

Let me tell you how a series regulator works. It basically consists of a pass transistor and a control circuitry that controls the conductive of pass transistor in order to maintain a fixed voltage at the output, irrespective of the load. When no load is present, a series regulator draws little to no current from the capacitor, which is why the voltage across the capacitor keeps building and building up until both the regulator and the capacitor pop

PrathikP

6 years ago

A shunt regulator, on the other hand, shunts current (as the name suggests), therefore drawing current from the capacitor and preventing it from exploding. the zener draws current even if there is no load, which is why it should be the choice of regulator.

PrathikP

6 years ago

So an idle current consumption is needed, counterintuitively, to prevent explosion.

smg2006

6 years ago

I fully understand, although being an embedded software designer. I'm currently in need of a simple small and cheap power supply for MCUs and their surrounding modules for low idle current and long lifetime in terms of component wear. - I'm currently trying to alow for a idle setting as well as a MCU controlled modification that would allow for greater current from the mains in case a specific pin gets high or low on the MCU. I feel like this would solve the issue and needs.

smg2006

6 years ago

Thanks for the comments.

smg2006

6 years ago

Well, now I seem to have it.

hurz

6 years ago

@smg2006, be very careful or you are not for long a software designer and get killed by your little dangerous supply circuit. Please use a little transformer to have a galvanic separation, this circuit here is connected to mains and can have 325V or even more at the pins you think is ground and thats why its just 0V, No its propably not cause it depends on how you put the plug into the outlet mains connector. Better use a transformer and you are on the safe side and can also ICP your controller chip from your PC SDK without a big bang when plug in the PC connector! Hope you understand.

smg2006

6 years ago

@hurz thanks for the heads up. I would like to use the opportunity to learn from it. Can you explain what is wrong? I see the ground as 0v. I just don't know how to depict it.

smg2006

6 years ago

Alright, I understand what you mean. But if the capacitor was to break, wouldn't it disconnect the power to the circuit?

hurz

6 years ago

No, the capacitor is not a proper galvanic separation. Again use a transformer as long you ask such questions, you are in dangerous to get killed.

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