Computer ATX power control circuit working principle analysis - Power Circuit - Circuit Diagram

MOS power IC full range

Industrial Router Crystal 3.2*2.5mm 3225 26M (26.000MHZ) 12PF 10PPM 20PPM 30PPM

inductance

SMD aluminum electrolytic capacitor

Fourth, the overvoltage protection overvoltage protection is sampled from +5V by R17 and Zener diode Z02 parallel circuit, and sent to the {5} pin of 339 via D37. If the +5V power supply rises for some reason, the {5} pin level of 339 will also increase. When the {4} pin level is exceeded, the {2} pin will send a high level to the 494 {4} pin. The output of the ±5V, ±12V, +3.3V power supply is blocked to achieve the purpose of overvoltage protection. During normal operation, the voltage drop on R17 is not large, and the voltage of Z02 is sent to the {5} pin is low. If the voltage of the +5V power supply rises, the voltage drop across R17 exceeds the regulation value of Z02, Z02 is turned on, +5V The voltage value after the power supply rises is all added to the {5} pin of 339, prompting it to quickly block the output of the 494 pulse to protect the power supply.

V. Undervoltage Protection Undervoltage protection is sampled from R32 at -5V and R14 at -12V, and sent to the {5} pin of 339 via R34 and D37. If the output voltage is too low for some reason, the negative value of -12V and -5V will also decrease, that is, the voltage value rises, and the 5th pin sent to 339 via R34 and D37 raises the level. The {2} pin of 339 sends a high level to the {4} pin of 494, thereby blocking the output of the 449 pulse and implementing undervoltage protection. When the diode D32 is turned on, its voltage drop is basically independent of the passing current, and it is kept at 0.6V~0.7V, so the reduction of -5V voltage will be transmitted to the negative end of D32, which improves the sensitivity of undervoltage protection. .