A DC power supply takes AC from the wall outlet, converts it to unregulated DC, and reduces the voltage using an input power transformer. typically stepping it down to the voltage required by the load. For safety reasons, the transformer also separates the output power supply from the main input. In this project, we will design a Simple 3A 12V power supply circuit using a 2N3055 power Transistor.
2N3055 power transistors are a common part of 12V power supply circuits The 2N3055 is a semiconductor NPN bipolar power transistor that consists of three terminals called emitter, base, and collector. Unlike FETs (Field effect transistors) it is a current-controlled device in which a small current at the base side is used to control a large amount of current at the emitter and collector side.
Hardware Components
The following components are required to make Power Supply Circuit
| S.No | Component | Value | Qty |
|---|---|---|---|
| 1. | Stepdown Transformer | 230V/15V | 1 |
| 2. | NPN Power Transistor | 2N3055 | 1 |
| 3. | Bridge rectifier | 5A | 1 |
| 4. | Zener Diode | 12V | 1 |
| 5. | Heat Sink | – | 1 |
| 6. | Resistor | 680 ohm | 2 |
| 7. | Capacitors | 5000μF, 0.01μF | 1,1 |
| 8. | Breadboard | – | 1 |
2N3055 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 2N3055
Power Supply Circuit
Working Explanation
This circuit is capable of providing a DC voltage source of 12 volts with a current of max 3A. The power supply circuit uses a 12V Zener diode as a voltage regulator. A Zener diode voltage regulator alone can not provide a large current source, because of the power limit of the Zener diode. So, a 2N3055 current amplifying transistor in a Common-base configuration is used.
On providing an AC input from a 230V/15V 5A non-CT transformer, The step-down AC signal passes through a bridge rectifier which translates the AC signal into a rippling DC. After which the signal passes through a smoothing capacitor C1 (5000μF) to remove any undesirable noise. The signal then passes through a voltage regulator section using a 12V Zener diode. Here, a 680Ω resistor acts as a current-limiting voltage source. In combination, they provide a regulated 12V DC at a relatively low current.
After this, the signal is passed through a current amplifier (2N3305) in a common base configuration to boost the current to 3A DC with the base reference voltage acting through a Zener diode voltage regulator. The DC signal then passes through capacitor C2 to remove any residual noise before going on toward the output.
Applications
- Used in various power amplifiers and oscillators to provide DC supply.
- DC power supplies are widely in use in low voltage applications such as charging batteries, automotive applications, aircraft applications, and other low voltage, low current applications.
- Used as an RPS (Regulated power supply) to provide the DC supply to the various electronic circuits such as small electronic projects.
