PC Power Supply with 13.8V & 5A

The circuit of power supply for PC works with a mains voltage of 230VAC to produce an output of 13.8V at 5A due to rectification.

This project came upon the modification of a PC switch mode power supplies (SMPS) which are cheaper and widely available because linear power supplies could give major disadvantages such as high power dissipation, size, and appropriated weight. The SMPS are rated anywhere between 150W and 300W depending on the PC model and provides 70% to 90% efficiency. Several power supply units are designed according to the same principle of half-bridge configuration.

The circuit operates for a short duration as a free-running oscillator after switching ON the mains voltage. A feedback winding at the output transformer causes this behavior. Normally for PC power supplies, the switching frequency is approximately 33 kHz as defined by a resistor and a capacitor. In the original power supply, several protection circuits are included for excessive primary current due to a very high secondary current that leads to a high alternating voltage. The circuit and load should also be protected against over-voltage. Providing 13.8V includes rectification, regulation, protection, and filtering at secondary.

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