When probing the primary side of the A20112 with an oscilloscope, always use an isolation transformer to prevent ground-loop shorts and protect your test equipment.
The A20112 typically functions as a linear or regulated switch-mode power supply (SMPS), depending on the specific manufacturing revision (often tied to vintage electronics brands like McIntosh or legacy computing peripherals).
Auxiliary windings on the inductors or a voltage divider connected to the ZCD pin detect when the inductor current reaches zero, triggering the next switching cycle. 2. Schematic Breakdown and Functionality a20112 power supply schematic
Elias checked the schematic’s bill of materials (BOM), noting the capacitor rating: 35V35 cap V 105∘C105 raised to the composed with power cap C
: It manages two power stages in parallel but out of phase. This reduces the ripple current in the output capacitors and allows for smaller, more cost-effective inductors. When probing the primary side of the A20112
The A20112 utilizes either four discrete high-speed diodes or a single integrated bridge rectifier block. This stage flips the negative halves of the AC sine wave into positive pulses, resulting in pulsating DC. 3. Smoothing and Filtering Stage
): Provide voltage feedback to the A20112 to maintain output voltage stability. The A20112 utilizes either four discrete high-speed diodes
Absorbs high-voltage spikes and transient surges from the main power grid.
Manufacturers rarely release schematics for commercial power supplies, but you can find the via:
A 500W generic ATX power supply was reported using a KA7500BD and an LM339 comparator. The KA7500BD, essentially a clone of the TL494 PWM controller, is extremely common in older ATX designs. A user in a forum sought help for a power supply labeled "A20112," mentioning a blown fuse and an invisible silkscreen—indicating the "A20112" is the board's part number.
Provides galvanic isolation to keep the user safe from high-voltage AC mains.