Here is circuit switching regulator 5V 5A for digital circuit.
Use IC LM2678-5.0 is High Efficiency 5V 5A Step-Down Voltage Regulator This is good power supply, small size and do not hot.

Friends want to build the digital power supply which this circuit “Top Linear power supply regulator 5V 5A with 7812 and LM723” is good quality, but as the too old circuit. Not suitable for this era. So I to find a new and very powerful also an Energy savings.
Considering these reasons. We will Using an ICs Switching supply. Because of has very high performance. High energy, while the low energy input.
LM2678 can respond to fully our needs. We can supply approximately 5A. The circuit and very easy to use. See information on the manufacturer’s manual, very easy to understand explanations. It uses a little equipment is only 9 pieces. And Cin = 3x15uF 50V, C2-0.47uF 63V , C3-0.01uF 63V , D1 – 6TQ045S, L1-22uH, Cout=2x180uF 16V as figure 1
Advantage of this range is very wide input voltage. From 8 vots to 40 volts DC power and does not need to be very smooth. But must be have the current 5 A or more.And this circuit high performance. Generate heat loss at low IC can use a small cooler (heat sink).

Source : 97 Electron Circuit

source:

This is circuit Simple DC Voltage Regulator By Transistor C1061. (easy circuit)
by this circuit can give Voltage go out about 12V, depend on Zener diode or ZD1 usual use 12V values thus. When you use other value 9V such as get Voltage about 9V also. And this circuit still give current output about 1A depend on transformer. The detail is other request you see in image circuit.

If you the hight current than top circuit. you can be try make this circuit, it can provide the 2 Amp current with 2N3055 transistor.

DC 12V to DC 6V-7.5V-9V Converter using 2N3055

This circuit is DC to DC converter model step down voltage. That can modify voltage input 12V DC from be DC 6V , 7.5V and 9V by have the size current about 1A – 2 Amp think. Be easy circuit use Zener diode maintain one’s position voltage. Be stable and have transistor 2N3055. When you several examples of the output voltage 6Vout, R1 =330 , ZD1=6.6V ; 7.5Vout, R1 = 270 , ZD1 = 8.2V ; 9Vout , R1=180 , ZD1=10V ; Perform enlarge the trend tallly go up fully be usable next , see the detail in the circuit and read to add

Our friends is looking for a dual power supply positive, negative and ground for a experiments various circuits.
In some times we need to have experiments about a OP-amp IC – LM741. Which must to use level voltage power supply of +9 volts and -9 volts, or when we a preamplifiers circuit or tone control circuits but they uses supply voltage of +15 volts and -15 volts
We think this circuit will respond your needs certainly because….
- Can provide the positive, negative voltage at size 3, 5, 6, 9, 12 and 15 volts respectively and the current output under 1.5 amps.
- Easy to use with rotating selector switch to selects level voltage as you want, Do not have a voltsmeter measure the output voltage.
It is circuits simple and cheap to make because the IC that have been popular are LM317 and LM337.

How it works
As show figure below , there are the didoe 1N4001 – D3 and D4 acting full-wave rectifier side the positive voltage. Then so filter waveform to smooth with a capacitor C1(2,200uF) , Then entered to input of IC1(LM317T) that is a positive regulated IC, it can adjust voltage to changing of 1.2-37 volts and provide the maximum output current of 1.5 amps….

Read more  and view circuits at http://www.eleccircuit.com/dual-power-supply-3v5v6v9v1215v-with-lm317lm337/

Normally begin to learn about electronics power supply from the battery, for example, 9 volts, 1.5 volts, 6 volts etc. But there are disadvantage that when using battery power is discharged. I need to buy a new one. Consume more.
We should the dc power supply have a choice of AC voltage. Which it must provide a output voltage as usage often is 1.5volt, 3 volts, 4.5 volts, 6v, 9v, and the current is about 1 A.
When we view many circuit ideas, found that the as figure this below (number second the power supply projects in my life) have the best fit. We use a dc voltage regulator number LM317T is the heart of the circuit. Featured, is the constant voltage. Low noise. Almost equal to the voltage of the battery. And short-circuit protection as well…..

Read more and view circuit at http://www.eleccircuit.com/lm317-linear-power-supply-regulator-selector-15v3v45v5v6v9v-15a/

The 3-pin regulator IC as a 78xx numbers have get very popular. I also like it because it is convenient and affordable. Although it is a short circuit within it. But very often, it would have been damaged when a short circuit. I think that should be a good short-circuit protection circuit.As an example, I would suggest a two circuit. We use a simple technique. The more secure without having to change the IC-regulator frequently.

Fuse electronic for ic regulator

Power supply, plus the ground, using current up to 1 Amp.Normally used, IC Regulator no. 78XX. When used to power circuits.And the short circuit that occurred.If no fuse various equipment will be damaged.But if there is an electronic fuse circuit for IC number 78XX.Then when the, short-circuit.This circuit will act to stop paying current and voltage immediately.Thus preventing the loss.
When entering the input voltage, the circuit Q1 and Q2 at the circuit, a bi stable multivibrator circuit.The Q1 Q2 will start but will not work.Because, C1 connected to the base pin of Q1.Then, the charging.Therefore, the voltage at Pin Collector ‘s Q1, to bias the base pin of Q3.Through R4, so the Q3 conduct. And Q4 will conduct with.As a result, voltage input to pin 1 of IC1.Cause the output voltage Implemented.If there is a short circuit when? D1 has served as a ground to stand Q2 base pressure of about 0.3 volts, resulting in a loss Q2 stopped. Bi stable circuit has changed the operating environment to run Q1.

Read more source: http://www.eleccircuit.com/dc-power-supply-protection-circuits/