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Characteristics of high frequency rectifier diodes in closed power supply
Publish：SHENZHEN ENXIC ELECTRONICS CO., LTD,Schottky diodes, rectifier diodes, fast recovery diodes, switching transistors, thermistors, MOS tube, TVS tube, Youze Electronics Time：2018-01-08 Views:1794
Because the frequency of the modern switching power supply is above 20kHz, the rectifier diodes in the switching power supply must have the characteristics of low forward pressure reduction and rapid recovery. It should also have large enough output power compared with the general rectifier diode. The reverse recovery time of fast recovery diode and super fast recovery diode is reduced to millisecond, so the efficiency of power supply can be improved by using the following three types of rectifier diodes: fast recovery diode; super fast recovery rectifier diode; Schottky rectifier diode.
The fast recovery rectifier diode and the ultra fast recovery diode are used as the rectifying devices in the switching power supply for the radiator, which depends on the maximum power of the circuit. In general, the allowed junction temperature of these diodes is at 175 degrees centigrade. The manufacturer has a technical description of the indicator to provide the designer to calculate the maximum output current, voltage and shell temperature.
Even under large positive current, the forward voltage drop of Schottky rectifier diode is very low, only about 0.4V, and with the increase of the junction temperature, the forward pressure drop is lower. Therefore, the Schottky rectifier diode is especially suitable for the low voltage output circuit of about 5V. The reverse recovery time of the Schottky rectifier diode is negligible, because the device is a majority of the carrier semiconductor devices, and in the switch process of the device, there is no problem of removing a few carrier storage charges.
The Schottky rectifier diode has two disadvantages: one, the reverse cut-off voltage is low, the current product is about 100V, and the second, the reverse leakage current is large, making the device more vulnerable to heat breakdown than other types of rectifier devices. Of course, these shortcomings can also be overcome by increasing the instantaneous over-voltage protection circuit and properly controlling the junction temperature. It shows the typical characteristics and parameters of high speed rectifier diodes.
The fast recovery and ultrafast recovery rectifier diode has moderate and higher forward voltage drop, and its range is from 0.8 to 1.2V. The two rectifier diodes also have higher cut-off voltage parameters. When selecting a fast recovery rectifier diode, the reverse recovery time is at least 1/3 of the switching transistor‘s rise time. The two rectifier diodes also reduce switching voltage spikes, and this spike directly affects the ripple of output DC voltage. Therefore, they are especially suitable for use in auxiliary power circuits with low power and output voltage of about 12V.
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