ال تأثير من ال بدء المقاوم من ال ينظم الطاقة الإمداد

The selection of resistors in switching power supply circuits not only considers the power consumption caused by the average current value in the circuit, but also the ability to withstand the maximum peak current. A typical example is the power sampling resistor of a switch MOS transistor, which is connected in series between the switch MOS transistor and the ground. Generally, this resistance value is very small, and the maximum voltage drop does not exceed 2V. It seems unnecessary to use a high-power resistor based on power consumption. However, considering the ability to withstand the maximum peak current of the switch MOS transistor, the current amplitude is much larger than the normal value at the moment of startup. At the same time, the reliability of the resistor is also extremely important. If it is open circuit due to current impact during operation, a pulse high voltage equal to the supply voltage plus the back peak voltage will be generated between the two points on the printed circuit board where the resistor is located, and it will be broken down. At the same time, it will also break down the integrated circuit IC of the overcurrent protection circuit. For this reason, usually a 2W metal film resistor is selected for this resistor. Some switching power supplies use 2-4 1W resistors in parallel, not to increase dissipation power, but to provide reliability. Even if one resistor is occasionally damaged, there are several others to avoid the occurrence of open circuits in the circuit. Similarly, the sampling resistance of the output voltage of the switching power supply is also crucial. Once the resistance is open, the sampling voltage is zero volts, and the PWM chip output pulse reaches its maximum value, causing a sharp increase in the output voltage of the switching power supply. In addition, there are current limiting resistors for optocouplers (optocouplers), and so on.

In switching power supplies, the use of resistors in series is common, not to increase the power consumption or resistance value of resistors, but to improve the resistance's ability to withstand peak voltage. In general, resistors do not pay much attention to their withstand voltage. In fact, resistors with different power and resistance values have the highest operating voltage as an indicator. When at the highest operating voltage, due to the high resistance, the power consumption does not exceed the rated value, but the resistance can also break down. The reason is that various thin film resistors control their resistance values based on the thickness of the film. For high resistance resistors, after the film is sintered, the length of the film is extended by grooving. The higher the resistance value, the higher the grooving density. When used in high-voltage circuits, spark discharge occurs between the grooves, causing resistance damage. Therefore, in switching power supplies, sometimes several resistors are intentionally connected in series to prevent this phenomenon from occurring. For example, the starting bias resistance in common self-excited switching power supplies, the resistance of switching tubes connected to DCR absorption circuits in various switching power supplies, and the application resistance in the high-voltage part of metal halide lamp ballasts.

٪ 0aIn إضافة٪ 2c زنك أكسيد متغيرات هي أيضا شائعة مستخدمة في تبديل طاقة إمداد دوائر. زنك أكسيد متغيرات لها آن شديد سريع ذروة جهد امتصاص وظيفة. ال أكبر خاصية من متغيرات هو ذلك متى الجهد المطبق إلى لهم هو أدناه لها عتبة ٪ 2c ال التيار التدفق من خلال لهم هو متطرف صغير٪ 2c مكافئ إلى أ مغلق صمام. متى ال الجهد يتجاوز ال عتبة ٢ج ال التيار التدفق من خلال ذلك الارتفاعات المفاجئة٪ 2c مكافئ إلى أ صمام فتح. بواسطة استخدام هذا وظيفة٪ 2c غير طبيعي الجهد الزائد ذلك غالبا يحدث في الدائرة يمكن أن تكون مكبوتة و الدائرة يمكن تكون محمية من الجهد الزائد الضرر. المتغيرات هي بشكل عام متصلة إلى ال التيار الكهربائي المدخلات من التبديل الطاقة الإمدادات و يمكن امتصاص البرق المستحث عالية الجهد من الطاقة الشبكة ٪ 2C توفير الحماية متى ال التيار الكهربائي الجهد هو أيضا عالية.