What types of SMD patch varistors are available?

SMD chip varistoris a resistance device with nonlinear volt-ampere characteristics. It has resistance and other characteristics. It is mainly used to clamp the input voltage within a certain range to absorb excess current before voltage input. Its response time is ns level, and its speed is very fast. It is a special element used to protect the circuit behind, especially in surge protection. We often use zinc oxide SMD patch varistors

SMD patch varistorsare generally divided into three types:

1. Common type: We often use common patch varistors, sometimes called surge absorption type, which are mainly used to clamp high input voltage and suppress lightning transients. The occurrence of this transient overvoltage is random, and the voltage peak may be very large. Most of the varistors we usually see fall into this category. Generally, the fuselage size range by Ф 5mm~ Ф 20mm, including 07271/471, 10271/471, 14271/471, etc. If you are familiar with SMD varistors, you will see the following SMD varistors on many occasions

Here, we should consider comprehensively when selecting:

① Large limiting voltage (V): that is, the large voltage that the two ends of the rheostat can bear. Take 220V mains supply as an example, assume that the fluctuation range of mains supply input voltage is between 0.8 and 1.5, and the voltage at both ends of the rheostat is 1.5 × 1.5=330V, up to 220. At this time, the optional rheostat specification can be 471 or 561. The larger one is selected because the peak voltage may exceed 330V or even higher. If the SMD patch varistor is at the nominal voltage for a long time, the service life of the SMD patch varistor is easily affected

② Current capacity (KA): refers to the pulse current applied within the specified time interval and the large pulse current allowed to pass through the rheostat. In fact, the surge current absorbed by the patch varistor should be less than the large magnetic flux of the product

③ Nominal voltage, leakage current (MA), etc. can also be considered

2. Medium and high energy type: as the name implies, it absorbs higher level of surge and has higher energy density. This SMD patch varistor is mainly used for magnetic energy in large induction coils such as cranes, current transformers and generators. It is a selection standard for this kind of varistor energy absorption capacity, because it usesSMD patch varistorto absorb energy. At present, many high-energy SMD chip varistors either have low voltage or insufficient energy. If the energy is not high enough, the absorbed energy density is not large enough. When choosing, we should choose according to the actual needs and pay attention to what to protect

3. High-power type: this type of rheostat is mainly used to absorb the continuous pulse group that occurs periodically, such as the rheostat on the switching power supply. Because the impulse voltage of switching power supply is periodic, the energy can be calculated according to the cycle. Although the peak voltage is not high, the average power is high due to the high frequency. Therefore, high power SMD patch varistor is required at this time. The selection shall be calculated according to the pulse period