In this post we comprehensively discuss how to construct 12V 5 Amp SMPS circuit using MOSFET and optocoupler feedback.
Its efficiency is around 85%.
What is a 12V 5 Amp SMPS Circuit:
A 12V 5A SMPS Switched Mode Power Supply circuit is designed to provide a stable and regulated 12V DC output with a maximum current of 5 amperes.
SMPS circuits are commonly used in various electronic applications where efficient power conversion is required, such as powering electronic devices, LED lighting systems or charging batteries.
Below, we will explore the unique construction details and formulas that set this power supply apart.
Diagram Circuit
Parts List:
| Category | Component | Quantity |
|---|---|---|
| Resistors | 470k / 1/4W MFR | 1 |
| 1k / 1/4W MFR | 1 | |
| 18k / 1/4W MFR | 1 | |
| 47Ω / 1/4W MFR | 1 | |
| 0.22Ω / 1W MFR | 1 | |
| 150Ω / 1/4W MFR | 1 | |
| 2.2k / 1/4W MFR | 1 | |
| 22Ω / 2W MFR | 1 | |
| 22Ω / 1/4W MFR | 1 | |
| Capacitors | Electrolytic 470nF / 250V | 1 |
| Electrolytic 100μF / 400V | 1 | |
| Electrolytic 47μF / 25V | 1 | |
| Electrolytic 220μF / 25V | 1 | |
| PPC 10nF / 500V | 1 | |
| PPC 100pF | 1 | |
| PPC 2.2nF / 100V | 1 | |
| Semiconductors | Diode 1N4007 (Rectifier) | 4 |
| Zener Diode 18V / 1W | 1 | |
| Zener Diode 11.2V | 1 | |
| Schottky Diode BA159 | 2 | |
| Schottky Diode 8A / 100V | 1 | |
| Transistor KC507 | 1 | |
| MOSFET IRF840 | 1 | |
| Optocoupler 4N35 | 1 | |
| NTC Thermistor | 1 | |
| Other | Fuse 5 Amp | 1 |
| Ferrite core EE | 1 |
Working Details
The core concept centers around the flyback inverter, utilizing a MOSFET power switch for dynamic control.
Initialization involves the use of a 470k resistor to charge the MOSFET gate prompting its activation.
Positive feedback mechanisms ensure swift and complete MOSFET opening.
The primary of the transformer links to 325V, initiating energy accumulation within the core.
As a result, primary current increases, causing a voltage drop across the 0R22 current sensing resistor.
When the voltage drop across the current sensing resistor reaches 0.5V, the KC507 transistor opens.
KC507 then reduces the voltage on the MOSFET gate, instigating its closure.
A feedback mechanism facilitates rapid MOSFET closure, leading to a reversal of voltage polarity across the transformer windings.
The stored energy in the transformer core efficiently transfers to the output via an electrolytic filter capacitor.
Collaborative efforts of an optocoupler and zener diode ensure stable output voltage.
The zener diode activates when the output voltage reaches its nominal value.
The 4N35 optocoupler LED permits current flow, activating the optocoupler transistor.
This transistor enhances the voltage at the base of KC507, enabling it to turn on at a lower drop on 0R22.
Inherent short circuit protection is achieved through the current sensor 0R22 with KC507, limiting the MOSFET peak current to 2.27A.
A ferrite core transformer with a secondary winding wound using four wires of 0.6mm diameter, and other windings using 0.4mm wire.
The optocoupler and zener diode combination results in a maximum output voltage deviation of 4%.
Simple modifications for other voltages involve adjusting the zener diode voltage and the number of secondary turns at the same ratio.
Formulas and Calculations:
Here in this article 12V 5 Amp SMPS circuit are probably employed to specify the voltage deviation (Vdeviation) and maximum allowed current (Imax) for a circuit:
Maximum Current, or Imax: = 2.27 A
This number, in your instance 2.27 A, indicates the maximum amount of current that may pass through a part or circuit safely.
Overdrawing this current may result in malfunction, damage or overheating.
In circuit design, it is frequently employed to make sure parts are not overstressed beyond their present ratings.
Datasheets for electronic components may provide Imax in addition to other characteristics like nominal voltage and operating temperature.
Vdeviation (Voltage Deviation)= 4%
This figure, which in your instance is 4%, denotes the permitted voltage fluctuation from a target level.
A percentage is frequently used to express it.
For example, the following voltage range might be acceptable if your circuit has a nominal output voltage of 12V and a Vdeviation of 4%:
Minimum voltage: 12V – (4% of 12V) = 11.52V
Maximum voltage: 12V + (4% of 12V) = 12.48V
In order to establish tolerable voltage variations around a controlled output voltage, Vdeviation is essential in power supply design.
Note:
these equations are utilized to specify a circuits operating limitations for voltage and current, guaranteeing dependable and secure functioning.
Safety Note:
- This 12 V 5 Amp switch mode power supply circuit is not recommended for beginners due to its connection to potentially hazardous mains voltage.
- Poor circuit design may lead to mains voltage reaching the output.
- Capacitors may retain dangerous voltage even after disconnection from mains.
- Proceed at your own risk, and no responsibility is taken for any injury to health or property.
Conclusion:
When designing or working with a 12V 5A SMPS circuit, it is essential to consider safety precautions, thermal management, and adherence to relevant regulations.
Following established design guidelines and safety standards is crucial especially for power supplies intended for commercial or industrial applications.
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