[Science knowledge] How to design a surge protection circuit in
Time:2018-11-12 Read:400
  Your lamp has broken in three months? Surge is the culprit!
  Phenomenon description: In daily life, we sometimes encounter hundreds of lamps for no reason. The common phenomenon is that the LED downlights installed in the hotel lobby are not bright from time to time, often bad, repaired and broken, broken and repaired, the root cause It is caused by surge voltage.
一、what is the swell
  Surge is also called a surge, as the name suggests is a transient overvoltage that exceeds the normal operating voltage. In essence, a surge is a violent pulse that occurs in just a few millionths of a second. Possible causes of surges are: heavy equipment, short circuits, power switching, or large engines. Products containing surge arresters can effectively absorb sudden bursts of energy to protect connected equipment from damage.
二、the source of surge voltage
  1. Surge caused by lightning strikes. When a lightning strike occurs, the communication circuit generates induction and forms a surge voltage or current.
  2. Load switching and short-circuit faults in system applications can also cause surges;
  3. High-frequency surge voltage caused by frequent switching of other equipment.
三、why the power supply needs surge protection circuit
  The power module is the system that is in contact with the outside and the interface. The external surges pass through the power module, so the surge protection circuit is required.
  Due to the small size and high integration of the power module, the maximum withstand voltage and maximum current of the internal control chip and transistor are relatively limited. A surge voltage may cause damage to the module, resulting in paralysis of the entire system, even if it is not damaged immediately. The device is subjected to stress shocks, which also affects the life and reliability. Therefore, in order to ensure the continuous and reliable application of the power module, a surge protection circuit is generally required. The power module is limited by the small size, and many modules cannot be equipped with anti-surge circuits. Therefore, it is necessary to add an anti-surge circuit to the outside of the module.
四、Commonly used anti-surge circuits have three options
  1. Use traditional lightning protection components to form surge protection circuits, such as TVS tubes (transient suppression diodes), gas discharge tubes, PTCs (thermistors), etc.
  2. Optical coupling circuit.
  3. Magnetic coupling circuit.
  The so-called anti-surge, there are two pressure indicators, one is common mode, and the other is differential mode. Surge generated by lightning or high current switching in nature is generally considered to be common mode, and the surge in the form of differential mode is often caused by high voltage lines in the vicinity of the data cable and poor insulation between the data cable and the high voltage line.
  Although the latter is much smaller than the voltage and current generated by the former, it does not remain as short as a few milliseconds as in the former, but will steadily exist for a long time in the data communication network. The nominal withstand voltage of an optocoupler or a magnetically coupled device is the common mode, which is the withstand voltage between the front end and the back end. If this withstand voltage is exceeded, the front and back ends are burned together; the device does not claim the withstand voltage of the differential mode. This is determined by the design of the circuit. If the withstand voltage is exceeded, the front end burns out and the back end does not burn out.
Choose a reliable anti-surge circuit, which can effectively protect the dam caused by the instantaneous high voltage of the power grid. The small-volume, high-efficiency and self-short-circuited patch products will protect your power system.
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