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The structural characteristics of Schottky diodes

Schottky diode is a majority carrier conduction device, and there is no minority carrier lifetime and reverse recovery problems. The reverse recovery time of a Schottky diode is only the charge and discharge time of the Schottky barrier capacitor, which is completely different from the reverse recovery time of a PN junction diode. Since the reverse recovery charge of the Schottky diode is very small, the switching speed is very fast, and the switching loss is very small, which is especially suitable for high-frequency applications. However, the reverse breakdown voltage of Schottky diodes is relatively low, because the reverse barrier is relatively thin and the surface is easily broken down. Because Schottky diodes are more prone to thermal breakdown than PN junction diodes, the reverse leakage current is larger than that of PN junction diodes.
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Schottky diodes have the advantages of high switching frequency and reduced forward voltage, but their reverse breakdown voltage is relatively low, mostly not higher than 60V, and only about 100V at most, which limits its application range. For example, freewheeling diodes of power switching devices in switching power supply (SMPS) and power factor correction (PFC) circuits, high-frequency rectifier diodes above 100 volts in the transformer secondary, high-speed diodes of 600 volts to 1.2 kV in RCD snubber circuits, PFC 600V diodes for boosting. Only use fast recovery epitaxial diode (FRED) and ultra fast recovery diode (UFRD).
 
The reverse recovery time Trr of UFRD also exceeds 20ns, which cannot meet SMPS's needs of 1 MHz to 3 MHz in areas such as space stations. Even if the hard switch is a 100 kHz SMPS, due to the large conduction loss and switching loss of UFRD and the high case temperature, a large heat sink is required, which increases the size and weight of the SMPS, and does not meet the requirements of miniaturization and thinning. development trend. Therefore, the development of high-voltage Schottky diodes above 100 volts has always been a research topic and hot spot. In recent years, Schottky diodes have made breakthrough progress. High-voltage Schottky diodes of 150 volt and 200 volt have been put on the market. New materials of SBD and above 1kV have been successfully developed, which has injected new vitality and vitality into their applications.
 
The biggest disadvantage of Schottky diodes is low reverse bias voltage and large reverse leakage current. For example, a Schottky diode made of silicon and metal has a reverse bias voltage rated withstand voltage of only 50V, while the value of the reverse leakage current is a positive temperature characteristic, which tends to increase rapidly as the temperature rises. . In actual design, attention should be paid to the hidden dangers of thermal runaway. In order to avoid the above-mentioned problems, the reverse bias voltage of the Schottky diode in actual use is much smaller than its rated value. However, Schottky diode technology has also been improved, and its reverse bias voltage can be as high as 200 volts.
 
The above explanations are the structural features of Schottky diodes. I hope it will be helpful to you after reading. If you want to know more about Schottky diodes, please contact customer service online or call our company Service hotline (upper right corner of the website) for consultation, we will wholeheartedly provide you with quality service!
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