What is starting resistor
1. What is starting resistor
Starting resistor means that in a circuit that can start a system or a part of the functional system, the circuit current or signal will start the system through it. This resistance is called the starting resistance. The starting resistance is named according to the role it plays in the circuit, and there is no such resistance in the actual resistance. That is, if there is a capacitor at this position. Then this capacitor can also be called a startup capacitor.
2. Working principle of starting resistor
When the starting resistor starts the switching power supply successfully, it will use the new power supply circuit generated after starting to provide starting power to the switching circuit, thereby replacing the power supply of the original starting resistance. At this time, it is considered that it does not matter if the starting resistor is removed. It also works normally.
3. The role of starting resistor
When the power is turned on, when the circuit has not yet started to vibrate, a bias current is provided to the base of the switching tube, so that a certain amount of current flows through the collector of the switching tube and the primary coil of the switching transformer, and an induced voltage is generated in the feedback coil through the induction of the transformer. It is fed back to the base of the switch tube to make the circuit enter into self-oscillation.
In a switching power supply, the use of resistors in series is very common, and its purpose is not to increase the power consumption or resistance of the resistor, but to improve the resistance's ability to withstand the peak voltage. In general, resistors don't pay much attention to their withstand voltage. In fact, resistors with different power and resistance have the highest operating voltage. When it is at the highest operating voltage, its power consumption does not exceed the rated value due to the extremely large resistance, but the resistance will also break down. The reason is that in addition to controlling the resistance of various thin-film resistors by the thickness of the film, for high-resistance resistors, after the film is sintered, the length of the film is extended by grooves. The larger the resistance, the greater the density of the grooves. , When used in a high-voltage circuit, sparking discharge occurs between the grooves and the resistance is damaged. Therefore, in the switching power supply, several resistors are sometimes used in series to prevent this phenomenon from happening. For example, the startup bias resistance in common self-excited switching power supplies, the resistance of switching tubes connected to the DCR absorption circuit in various switching power supplies, and the application resistance of the high-voltage part of the metal halide lamp ballast, and so on.
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