Self Switching Mode Power Supply Practical Circuit Diagram (5V Battery Charger)

SMPS (Switching Mode Power Supply) Circuit Diagram

Battery Charger Switch Mode Power Supply (SMPS) Circuit Diagram for 5Volts electrobuff.blogspot.com

A Switched Mode Power Supply (SMPS) is a type of power supply that uses switching devices (like MOSFETs) to convert electrical power efficiently. The working principle of an SMPS involves the conversion of AC or DC input voltage into a regulated DC output voltage through a series of stages. Here's a basic explanation of its working principle and a block diagram:

Working Principle:

Rectification: If the input is AC, it's rectified to DC by a bridge rectifier.

Filtering: A capacitor filter smooths the rectified voltage.

Chopping: The DC voltage is chopped into pulses using a high-frequency oscillator (typically tens or hundreds of kilohertz).

Transforming: The chopped voltage is fed into a transformer which steps it up or down as required.

Rectification (again): The transformed voltage is rectified again, often using diodes.

Filtering (again): Another filtering capacitor smooths the pulsed DC into a stable DC voltage.

Regulation: A feedback loop compares the output voltage to a reference voltage and adjusts the duty cycle of the chopping oscillator to maintain a stable output voltage.

SMPS Block Diagram:

Input Stage:

AC input or DC input.
EMI filter to reduce electromagnetic interference.
Surge protection components.

Rectification and Filter Stage:

Bridge rectifier converts AC to pulsating DC.
Large capacitor(s) smooth out the pulsations.

Switching Stage:

Switching transistor (MOSFET) or transistor pairs.
Oscillator generates high-frequency pulses.
PWM (Pulse Width Modulation) controller regulates the duty cycle of pulses based on feedback.

Isolation Stage:

Transformer isolates the output from the input.
Primary and secondary windings provide voltage transformation.

Rectification and Filter Stage (again):

Secondary side rectification (diodes or synchronous rectifiers).
Output filter capacitor(s) further smooth the voltage.

Regulation and Control Stage:

Feedback network compares output voltage with a reference voltage.
PWM controller adjusts the duty cycle to regulate the output voltage.
Overload and overvoltage protection circuits ensure safe operation.

Output Stage:

Regulated DC output.
Voltage/current sensing components.

Auxiliary Circuits:

Startup circuitry.
Soft-start circuit to prevent inrush current.
Shutdown and standby circuits for power saving modes.

By efficiently switching the input voltage, SMPS achieves higher efficiency compared to linear power supplies, making them suitable for a wide range of applications from consumer electronics to industrial systems