Common Electronic Circuits and Devices or Microcontrollers Requires 5V DC power supply. We use Integrated Circuit LM7805 (Positive Voltage Regulator) to give Regulated Constant 5 Volt DC from unregulated DC supply. In this Article a simple easy to construct 5V DC power supply circuit designed and tested.
To indicate the presence of Input Voltage and Output Voltage here we used two LEDs. This Circuit designed to work as a Independent power source for electronic devices and circuits.
Circuit Diagram
Components Required (BOM)
| S.No | Designator | Value | Part Number | Quantity |
| 1 | TR1 | 230V to 0-12V AC | 0-12V Stepdown Transformer | 1 |
| 2 | R1, R2 | 330Ω | – | 2 |
| 3 | C1 C2 | 100µF/25V 0.01µF | Electrolytic Disc capacitor | 1 1 |
| 4 | D1 | – | Bridge Rectifier Module | 1 |
| 5 | U1 | LM7805 | LM7805_TO220 | 1 |
| 6 | LED1 LED2 | Red Green | – – | 1 1 |
Construction & Working
Every DC power supply circuit (Not SMPS) may have these stages to give Regulated Constant DC power supply. Here 230V AC main supply step down to 12V AC by using Step down Transformer then Bridge Rectifier module Converts AC supply to DC supply after that to Remove unwanted AC ripples from DC supply filter elements (Capacitor C1) used. After filter element we get 12 Volt DC supply, to Reduce this supply IC LM7805 employed here, at the output terminal of LM7805 we get constant Regulated 5V DC supply.
IC LM7805
This LM78XX series of fixed-voltage integrated-circuit voltage regulators is designed for a wide range of Regulator applications. These applications include on PCB board regulation for elimination of noise and distribution problems associated with single point regulation. Each of these regulators can deliver up to 1.5 A of output current. The internal
current-limiting and thermal shutdown features of these regulators essentially make them immune to overload.
Some notable features of LM7805 Positive voltage regulator are,
- 3-Terminal Regulators
- Output Current up to 1.5 A
- Internal Thermal-Overload Protection
- High Power-Dissipation Capability
- Internal Short-Circuit Current Limiting
- Output Transistor Safe Area Compensation, For more information refer datasheet.
Lets say the output voltage from the single phase 230V to 0-12 V transformer (used) is 12 V, how come that the input voltage to the filter is 12 V since there is a voltage drop of about 1.4 V (due to the rectifier) ?
Wouldn’t the capacitor that stabilizes the DC voltage after the rectifier correct that problem !?!?!?