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12 volt 50 wattlık güç kaynağı devresine ait ayrıntılara buradan ulaşabilirsiniz.
This is a simple low-cost 50W off-line switching power supply. It operates over a universal AC line input range 90-264 VAC and provides a 12VDC output at more then 4A load. Line and load regulation is better then 0.5%. The unit can operate at power line frequencies from 50 Hz to 1 kHz. It has overcurrent, overtemperature and overvoltage protections as well as passive inrush current limiting.
The PSU uses a flyback converter topology, with an 600V/11A MOSFET (Q1) as the switching device and PWM controller UC3845N (U3). The input section includes a fuse, EMI filter, inrush current limiting NTC resistor R1, a full bridge rectifier CR1, and a DC bus filter capacitor C2. The initial start-up current for the PWM IC is provided by “bleeding” resistors R7, R8 that allow small current which charges the Vcc capacitor C7. When the voltage at the Vcc pin of U3 reaches the positive under voltage lockout threshold (typically 14V-16V), the IC starts to operate and will be driving ON and OFF the switch Q1 via a gate drive resistor. When Q1 turns on, the DC bus voltage is applied across the transformer T1 primary winding, current through the transformer primary ramps up and energy is accumulated in the transformer’s magnetic field. Diodes D4 and D7 during this time interval are reversed biased. When Q1 turns off, the energy stored in the magnetic field causes the voltages across all winding to reverse polarity.
