Where can I find simple power supply skematics?

Question

I'm talking about the simple one where you use one diod and resistor. Any formulas too? Thankyou. P.S. Not looking for LM317 diagrams. Just looking for the simple diod-resister type.

Answer 1

you can check with hosfelt electronics, copper electronics, they may have what your looking for

Answer 2

Unlike Charles's comment, you *can* make a "power supply" with just a resistor and a diode.
But it will be -
- very dangerous, because you will have "live" potential throughout your low voltage circuitry!
- inefficient, because you have to burn-off (in form of heat) any energy which you don't need
- useful only for constant load purpose.
- high ripple (hum) unless you put an electrolytic capacitor somewhere in your low voltage circuit.
It works like this:
1) Check your life and house content insurance policies
2) Assume you need 12 Volt DC at (exactly) 100mA
3) Assume your mains power supply is 110VAC
4) Buy a 980 Ohm >10 Watt resistor and connect it to 110V Live. Connect the other end of the resistor to the anode of a 1N4004 diode.
5) Connect your load (12V 100mA) to cathode of the diode and the 110V Neutral.
6) Realize that you will NOT get 12VDC at the load because you only rectify one half wave of the AC, and you have no smoothing capacitor.
7) Burn your fingers on the resistor.
There are transformer-less power supplies in use (Electric toothbrush charger, X-10 controls, etc...) but they use a metal film capacitor (instead if a high-wattage resistor), a 1-Watt resistor (about 300Ohm), a full wave rectifier ( = 4 diodes) and a smoothing capacitor (electrolyte).
But it is still dangerous (must be hermetically sealed) and still requires constant load.

Answer 3

To use a diode and a resistor to make a power supply, you have to ensure your current drain will not cause the voltage drop across the resistor to exceed the zener's voltage rating, thus dropping it below the required power supply voltage.

Zener power supplies are common for performing little tasks, like providing a voltage reference to the input of an opamp, but you should also us a cap. across the zener to clean things up a bit.

You are better off using the LM78xx series, as that compensates for the changes in current up to the limit of the regulator, and they are quick and simple- one IC and one cap.

Answer 4

A diode and resistor will not make a power supply. It can be used as a voltage regulator for a D.C source.

Answer 5

If you want a zener diode regulated supply, here you are:
http://www.wam.umd.edu/~toh/ElectroSim/zener.html