Compact 120V AC to 12V DC 363mA Converter for Direct Live Wire Connection

The discussion addresses the design and selection of a compact 120V AC to 12V DC converter capable of supplying approximately 363mA directly from live mains wiring without using a wall outlet adapter. Suggested solutions include using a small transformer (e.g., 120V to 15-16V) followed by a bridge rectifier, filtering capacitors, and a 7812 linear voltage regulator to achieve stable 12V DC output. Alternatively, a capacitive power supply with an X2-rated capacitor and a 12V zener diode regulator can be used for lower current demands, though this approach becomes bulky at higher currents. For the smallest and flattest form factor, a high-frequency switch-mode power supply (SMPS) is recommended due to its reduced size and heat dissipation compared to linear regulators. Additional design considerations include implementing a bridge rectifier with ripple filtering, PWM-driven MOSFET regulation with feedback for voltage stability, current limiting to manage inrush current, RFI filtering to reduce electromagnetic interference, and spike suppression on the AC input. The importance of capacitor selection for high-frequency operation and the trade-offs between component size, current stability, and circuit complexity are emphasized. Practical advice includes potentially repurposing internal circuits from existing adapters if compactness and construction skills allow, and clarifying the application and space constraints to optimize the design.
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