The design and building of a 12V 5 Amp SMPS circuit with MOSFET and optocoupler feedback is explained thoroughly in this post.
It is around 85% accurate.
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.
Further we will explore the unique construction details and formulas that set this power supply apart.
Circuit Working:
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 | PPC 470nF 250V | 1 |
| Electrolytic 100μF400V | 1 | |
| Electrolytic 47μF 25V | 1 | |
| Electrolytic 220μF 25V | 1 | |
| PPC 10nF 500V | 1 | |
| PPC 100pF | 1 | |
| PPC 2.2nF 100V | 1 | |
| Semiconductors | Diode 1N4007 | 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 | |
| Fuse 5 Amp | 1 | |
| Ferrite core EE | 1 |
The key concept is the dynamic control of the flyback inverters via a MOSFET power switch.
During setup the MOSFET gate is charged using a 470k resistor which causes it to activate.
Fast and complete MOSFET opening happens via positive feedback methods.
Energy builds up in the core of the transformer when the primary connects to 325V.
Therefore, a voltage drop occurs across the 0R22 current detecting resistor as the primary current rises.
The KC507 transistor opens when there is a 0.5V voltage drop across the current sensing resistor.
The MOSFET gate then drops as a result of KC507 reduce the voltage on it.
A feedback system switches the voltage polarity across the transformer windings by enabling quick MOSFET closing.
Through the use of an electrolytic filter capacitor the energy stored in the transformer core is transferred efficiently to the output.
Stable output voltage is achieved by the teamwork of a zener diode and an optocoupler.
When the output voltage reaches its nominal value the zener diode turns on.
The optocoupler transistor is triggered by current flowing via the 4N35 optocoupler LED.
By increasing the voltage at the KC507s base the transistor allows it to activate at a lower level on 0R22.
The current sensor 0R22 with KC507 restricts the MOSFET the maximum current to 2.27A providing inherent short circuit safety.
A ferrite core transformer with four 0.6mm wires coiled around the secondary winding and additional 0.4mm wire windings.
The maximum output voltage variation generated by the pair of the optocoupler and zener diode is 4%.
Adjusting the zener diode voltage and the number of secondary turns at the same ratio is easy to modify for different voltages.
Formulas and Calculations:
Below are the formulas with calculations for Simple 12V 5 Amp SMPS circuit:
This circuit diagram is probably used 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 pass through a part or circuit safely.
Overdrawing this current may result in malfunction, damage or overheating.
In circuit design it is frequently used 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% represents the permitted voltage fluctuation from a target level.
A percentage is frequently used to express it.
For example, the following voltage range is acceptable if the 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 used to specify a circuits operating limitations for voltage and current guaranteeing dependable and secure functioning.
Safety Note:
- This 12V 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:
A Simple 12V 5A SMPS Circuit (Switched Mode Power Supply) offers a reliable, handy and efficient way to power devices that need a steady 12V DC output at up to 5A current.
Similar to a standard linear power supply it uses high frequency switching to achieve greater energy efficiency and less heat generation.
Its design makes it suitable for various uses such as embedded systems, tiny motor drives and LED lights.
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