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该开关电源稳压电路用于稳定不受控的输出5V电压。当输出5V电压升高,但未过压时,该电压加到R510、光耦合器N502中的发光二极管、精密三端稳压器N503上。N503基准电压为2.5 V,当N502中的光电晶体管输出电压加至R508上超过2.5 V时,输入N501②(误差放大器)的电压大于2.5 V,脉宽调制器从导通转入截止,从N501⑥输出,使开关管V501截止.输出5 V电压降低,反之,输出5 V电压升高,达到稳压目的。当输出5 V电压过压,大于6.2 V时,VD510击穿,使N503击穿,N502负端接地,R508上的电压升高.V504、VD513导通.N501④电位下降.振荡器停振,从而保护了开关电路不被损坏。RS05、C508决定NS01中振荡器的频率,R506、C515用于误差比较器的频率补偿。
The switching power supply regulator circuit is used to stabilize uncontrolled output 5V voltage. When the output 5V voltage increases, but not over-voltage, the voltage is added R510, light-emitting diodes in the optocoupler N502, precision three-terminal regulator N503. The N503 reference voltage is 2.5 V. When the phototransistor output voltage in N502 exceeds 2.5 V on R508, the voltage at input N501 ② (error amplifier) is greater than 2.5 V. The pulse width modulator switches from on to off and outputs from N501 ⑥ , So that the switch tube V501 ends. The output 5 V voltage decreases, on the contrary, the output voltage of 5 V increases to achieve the purpose of regulating. When the output 5 V voltage overvoltage, greater than 6.2 V, VD510 breakdown, so N503 breakdown, N502 negative terminal grounded, R508 voltage on the rise. V504, VD513 conduction. N501 ④ potential down. Protection of the switch circuit is not damaged. RS05, C508 decide the frequency of the oscillator in NS01. R506 and C515 are used to compensate the frequency of the error comparator.