LM7805 5V 1A Regulator Power Supply Circuit

The LM7805 circuit board is a voltage-regulated linear power supply that efficiently converts an input voltage within the safe range of 7V to 12V AC or DC to a fixed +5V DC output, capable of delivering a current of up to 1.2 Amps (with Heat Sink).

LM7805 5V 1A Regulator Power Supply Circuit Board

It is suitable for providing additional power to various electronic components, charging modules, or powering LEDs (max 5 watts).

Here, we will discuss and explain the workings of this positive DC power supply along with its circuit diagram.

Circuit Diagram

Schematic of lm7805 5v 1amp regulator power supply circuit is shown below.

Schematic of LM7805 5V 1A regulator power supply circuit

Working Explanation

The working principle of the LM7805 5V 1A regulator power supply circuit is simple, and it operates in two fundamental steps: AC/DC to DC conversion and voltage reduction (step down).

The circuit can accept either AC or DC input voltage. If AC voltage is supplied, the signal passes through the diode bridge (D1, D2, D3, D4) for full-wave rectification, converting it into DC voltage. On the other hand, if the input is already DC, the diode bridge ensures that the power flows in only one direction through DC-DC conversion.

The capacitor (C1) is used for smoothing, and maintaining the converted DC voltage, which, in both cases, is unregulated.

The series circuit consisting of a current-limiting resistor (R1) and an LED (D5) indicates the AC/DC to DC conversion by emitting light.

An LM78XX series positive voltage regulator integrated circuit, LM7805 TO220 (U1), is used to step down the voltage to a linear 5V. The minimum DC power (approx. 2.5V and 5mA) supplied to the VIN pin of the regulator IC is sufficient to activate it.


When the voltage received at the VIN pin of the IC (U1) exceeds 7.5V, the excess voltage is passed through the GND pin to the ground to convert it into heat, which is then dissipated by a suitable aluminum heat sink. Unlike PNP type regulators where up to 10% of the output current is wasted as quiescent current. This process helps maintain the +5V (fixed) output at the VOUT pin.

If the lm7805 IC becomes too hot (>125°C) due to overload or high ambient temperatures, it activates an internal thermal protection circuit by cutting off the IC's input supply. In the event of a short circuit occurring at the output, the internal circuitry of the LM7805 limits the current to prevent damage to the power supply circuit.

To ensure a stable and clean 5V 1A power output, an electrolytic capacitor (C2) is used for smoothing, and a ceramic capacitor (C3) is used to filter out noise. Additionally, male header pins (JP1) are connected to the output in parallel to power any 5V electronic devices through jumper wires.

See Also: AMS1117 3.3V 1A Regulator Power Supply Circuit.

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