Establishes a highly stable baseline reference voltage.
A network of resistors monitors the output voltage. If the voltage drops under a heavy load, the feedback loop biases the pass transistors to allow more current through, stabilizing the output. 4. Output Filtering and Crowbar Protection
The A20112 schematic incorporates an elegant current-limiting circuit. A low-resistance shunt resistor ( RSensecap R sub cap S e n s e end-sub
Because "A20112" is often a module number rather than a consumer brand model, finding the exact PDF can be tricky. Here are a few tips: a20112 power supply schematic
The A20112 is a classic linear-regulated (or in some variants, a hybrid switching-to-linear) power supply architecture. It is designed primarily for applications that require low electromagnetic interference (EMI), ultra-low output ripple, and robust tight regulation. Key Technical Specifications
The A20112 is primarily designed as a linear regulated or specialized switching power supply topology (depending on the specific manufacturer suffix, such as those found in legacy test equipment or specific CRT monitors). Most commonly, it functions as a multi-rail linear DC power supply designed to take an alternating current (AC) mains input and step it down to stabilized, low-noise direct current (DC) rails. Key Specifications
Interleaved control to reduce noise and balance thermal loads across MOSFETs . Establishes a highly stable baseline reference voltage
The clean AC voltage is passed into a full-wave bridge rectifier. This component converts the sinusoidal AC wave into a pulsating, single-polarity Direct Current (DC) signal.
The chip modulates an external MOSFET to switch rapidly, forcing the input current waveform to mirror the shape and phase of the AC input voltage. The energy is stepped up through a robust boost inductor into a bulk electrolytic capacitor. This stage creates a regulated, rock-solid , serving as the clean high-voltage rail for downstream logic.
The A20112 is a switch-mode power supply (SMPS) designed for the Namco System 246 and 256 arcade motherboards. Unlike standard PC ATX power supplies, the A20112 utilizes a custom form factor and a dedicated single-row output connector to interface directly with the arcade I/O board. It is a high-efficiency unit capable of delivering substantial current on the +12V rail to power the console's cooling fans and disc drives, while maintaining stable low-ripple voltage for the sensitive CPU and RAM (+3.3V and +5V). Here are a few tips: The A20112 is
The schematic shows a classic on the secondary:
The A20112 is a robust industrial power supply, but due to the age of the electrolytic capacitors inside, most surviving units require a "recap" maintenance service to ensure reliability. If a schematic diagram is required for component-level repair, it is recommended to search for schematics of similar Delta Electronics 150W ATX power supplies from the same era, as the control circuits are often similar.
Typically rated between 1A and 3A slow-blow, protecting the transformer from catastrophic downstream shorts.
Commonly delivers split rail voltages (e.g., +15V, -15V for operational amplifiers) or standard digital logic lines (+5V).