5V To 48V DC Converter For Phantom Power Supplies

The 5V to 48V DC Converter circuit relies on the MC34063A switching regulator IC to step up a low-voltage DC input to the higher voltage required for audio equipment. Power first enters the circuit through connectors, passing through a fuse (F1) for circuit protection, and ensures proper operation while a 5mm LED (LED1) indicates power status. The MC34063A acts as the core control element, operating as a DC-DC step-up (boost) switching regulator. It uses an internal oscillator and switch transistor to rapidly cycle current through inductor L1 (ranging from 100µH to 150µH). When the internal switch closes, energy is stored in the magnetic field of the inductor; when the switch opens, that stored energy collapses and is forced out, creating a higher voltage spike. Additional filtering and smoothing are provided by inductor L2 (22µH-220µH), resistors, and capacitors to stabilize the output line. Diodes play a critical role in directing this energy flow: 1N4007 diodes (D1, D3) handle general rectification and routing, while the SR1100 Schottky diode (D2) provides fast switching action with low forward voltage drop to efficiently capture the boosted output. Finally, a second 5mm LED (LED2) can be used to indicate the active 48V phantom power output stage on the custom PCB before it connects to the target audio device.