12V 2A Switched-Mode Power Supply Using KSE13005 and 2SC2655

This 12V DC, 2A switched-mode power supply (SMPS) converts 220V AC mains into a regulated 12V DC output. The design uses KSE13005 and 2SC2655 transistors in the primary switching stage, a ferrite transformer for isolation and voltage conversion, and a PC817 optocoupler for feedback and regulation. The output is rectified with two SR360 Schottky diodes.

Power Supply Requirements

• Input: 220V AC mains.
• Output: 12V DC at 2A.
• Switching frequency: high-frequency operation using KSE13005 and 2SC2655.

Key Components

• KSE13005 and 2SC2655 Transistors: Primary-side switching devices that handle high-voltage AC and drive the ferrite transformer.
• Ferrite Transformer: Provides high-frequency isolation and steps down the voltage to 12V.
• PC817 Optocoupler: Provides feedback from secondary to primary for voltage regulation and stability.
• SR360 Schottky Diodes: Fast-recovery diodes used to rectify the 12V secondary AC into DC.
• Filter Capacitors: Smooth the DC output to reduce ripple.

Circuit Operation

• The AC mains is applied to the primary switching stage using KSE13005 and 2SC2655 transistors.
• The transistors switch at high frequency, driving the ferrite transformer to step down and isolate the voltage.
• The secondary voltage is rectified by two SR360 Schottky diodes to produce DC output.
• The PC817 optocoupler monitors the output voltage and feeds back a control signal to the primary, adjusting the pulse width or switching behavior to maintain a stable 12V output.
• Filter capacitors smooth the output, ensuring low ripple and stable DC for connected devices.

Key Features

• High-efficiency 12V DC output at 2A
• Primary-side switching using KSE13005 and 2SC2655
• Feedback control via PC817 optocoupler for stable voltage
• Fast rectification with SR360 Schottky diodes
• Compact design with ferrite transformer for isolation and step-down
• Suitable for powering small DC devices or electronics

Construction Notes