A large ferrite-core transformer steps down the voltage.
| | Typical Part Number | Function | | :--- | :--- | :--- | | PWM Controller IC | UC3842, TL494, KA7500 | Generates switching signal for MOSFET. | | Primary MOSFET | 20N60, IRF840, etc. | High-voltage power switch. | | Primary Capacitor | 400V, 100-220µF | Smooths rectified input voltage. | | Transformer | Custom Ferrite Core | Steps down voltage, provides isolation. | | Output Diodes | MBR2045CT (Schottky) | Rectifies high-frequency AC to DC. | | Output Capacitors | 25V, 2200µF | Filters output DC voltage. | | Voltage Reference | TL431 | Provides precise voltage reference for feedback. | | Optocoupler | PC817 | Transfers feedback signal across isolation barrier. |
The high-frequency AC runs through a ferrite-core transformer that steps down the high voltage to a safe, low-voltage AC level while providing galvanic isolation between the mains and the user terminal block. s36012 power supply circuit diagram
Add a 0.01Ω shunt on the low side. Feed its amplified signal (via LM358) into a comparator that pulls the FB pin low when current exceeds the setpoint. This overrides the voltage loop.
Low-ESR electrolytic capacitors combined with a toroidal inductor choke smooth out the remaining high-frequency ripples, delivering a clean 12V DC output. 6. The Feedback Loop A large ferrite-core transformer steps down the voltage
: Standard silicon diodes create too much voltage drop and heat at 30A. The S-360-12 uses high-current Schottky diode pairs (common cathode packages like the 30C60 or 40C60) mounted to a dedicated secondary heatsink.
| Protection | Circuit Method | Action | | :--- | :--- | :--- | | | Current sensing via a 0.01Ω/5W wirewound resistor on the negative output rail. Voltage across it is fed to pin 16 (Error Amp 2) of TL494. | If voltage exceeds ~0.3V (≈30A), TL494 shuts down output. Hiccup mode. | | Over-voltage (OVP) | A Zener diode (13V) + SCR (C106) across output. | If output >13.5V, Zener triggers SCR, shorting output and blowing the primary fuse. | | Over-temperature | NTC thermistor bonded to the main heatsink, connected to TL494 shutdown pin. | Shuts down at >85°C. Automatically resumes when cool. | | High-voltage power switch
Once stable, control of the power transistors is assumed by the ubiquitous (or its equivalent, the KA7500).
To safely transmit error signals across the isolation barrier, the feedback network uses an optocoupler. It converts voltage deviations on the 12V side into light signals, isolating the controller on the high-voltage side.