# 5V Power Supply using 7805 Voltage Regulator with Design

## 5V Power Supply using 7805 Voltage Regulator with Design

In most of our electronic products or projects we need a power supply for converting mains AC voltage to a regulated DC voltage. For making a power supply designingÂ of each and every component is essential.Â Here I’m going to discuss the designing of Â regulated 5V Power Supply.

Component List :

1. Step down transformer
2. Voltage regulator
3. Capacitors
4. Diodes

Let’s get into detail of rating of the devices :

Voltage regulator :

As we require a 5V we need LM7805 Voltage Regulator IC.

7805 IC Rating :

• Input voltage range 7V- 35V
• Current rating Ic = 1A
• Output voltage range Â  VMax=5.2V ,VMin=4.8VÂ

Transformer :

Selecting a suitable transformer is of great importance. The current rating and the secondary voltage of the transformer is a crucial factor.

• The current rating of the transformer depends upon the current required for the load to be driven.
• The input voltage to the 7805 IC should be at least 2V greater than the required 2V output, therefore it requires an input voltage at least close to 7V.
• So IÂ chose a 6-0-6 transformer with current rating 500mA (Since 6*âˆš2 = 8.4V).

NOTE : Any transformer which supplies secondary peak voltageÂ up to 35V can be used but as the voltage increases size of the transformer and power dissipation across regulator increases.

Rectifying circuit :

The best is using a full wave rectifier

• Its advantage is DC saturation is less as in both cycle diodes conduct.
• HigherÂ TransformerÂ Utilization Factor (TUF).
• 1N4007Â diodes are used as its is capable of withstanding a higher reverse voltage of 1000vÂ whereasÂ 1N4001Â is 50V

Capacitors :

Knowledge of Ripple factor is essential while designing the values of capacitors

It is given by

• Y=1/(4âˆš3fRC) Â (as the capacitor filter is used)

1. f= frequency of AC ( 50 Hz)

2. R=resistance calculated

R= V/Ic Â Â

V= secondary voltage of transformer

• Â  Â  Â V=6âˆš2=8. 4

3. C= filtering capacitance

We have to determine this capacitance for filtering

Y=Vac-rms/Vdc

Vac-rms = Vr/2âˆš3

Vdc= VMax-(Vr/2)

Vr= VMax- VMin

• Â  VrÂ = 5.2-4.8 =0. 4V
• Â  Â Vac-rmsÂ = .3464V
• Â  Â VdcÂ = 5V
• Â  Â  Y=0Â .06928

Hence the capacitor value is found out by substituting the ripple factor inÂ Y=1/(4âˆš3fRC)

Thus, C= 2314 ÂµF and Â standardÂ 2200ÂµF is chosen

Datasheet of 7805 prescribes to use a 0.01Î¼F capacitor at the output side to avoidÂ transientÂ changes in the voltages due to changes in load and a 0.33Î¼F at the input side of regulator to avoid ripples if the filtering is far away from regulator.

# Circuit Diagram

• aarima says:

ripple factor

• Balaji says:

(Vr/2)Ã—âˆš3=0.3464

• Mohammed Mairajuddin Musharaf says:

Vr/2âˆš3=0.4/2âˆš3=0.115
But you got 0.3464p, please explain or correct ASAP

• Sneha Mary Reddy Thumma says:

can you specify what is y and how u got that formula ???

• Shivanand Ganji says:

great article. simple for power supply design. transformer and other components actually makes it bulky.

power supply should be in Component form. like smps.

• Ravindran DVL says:

As per the data sheet of7805 the min input voltage should be 7.2 volts. Here in the circuit diagram it is shown 6 volts. Please clarify.

• zeineb says:

and if i want output max 5V 2A? what should i add to the circuit?

• zeineb says:

and if i want output max 5V 2A? what should i addto the circuit plz?

• giridhar says:

18ohm, sorry

• giridhar says:

where have u used the 18k resistor?

• Yes, 7805 maximum output capacity is 1A. So you should always use a current below it. And the current rating of the transformer also matters.

• Nidheesh says:

Whether the output will be 5V 1A DC?

• 7805 is a proven voltage regulator. You will get it for sure. Try in hardware.

• Johanan Prime says:

hi there. im trying to design this in the Multisim program but i am unable to obtain the desired 5V output. instead, I am getting a constant 0.926pV output. I’ve tried changing the component values but I’m unable to obtain the expected result.

• arjun shinde says:

hello
thanks for giving specification of ICs 7805

• rusman says:

Hi,

thanks for the post.

when calculating R it should not be from secondary transformer since during discharge current direction is into the load.

so R = Vc / load into current via 7805.

do you agree ?