How to Choose a Schottky Diode

PublishTime： 2024-05-17 Article Source：LXMICRO Official Website

We often use Schottky diode in switching power supply, but because the performance varies greatly from manufacturer to manufacturer and so on, we must consider the following parameters when choosing Schottky:

1. Voltage Drop VF: VF is the voltage drop at both ends of the diode when the diode is in a positive Schottky diode.

2. Reverse saturation leakage current IR: IR refers to the current flowing through the diode when a reverse voltage is applied to both Schottky diode of the diode, the Schottky diode is to choose the diode with the smaller IR as much as possible.

3. Rated current IF: refers to the long-term operation of the diode, according to the allowed temperature rise converted into the average current value.

4. Maximum Surge Current IFSM: excess forward current allowed to flow. It's not a normal current, it's an instantaneous current, and that's a pretty big number.

5. Maximum reverse peak voltage VRM: even if there is no reverse current, as long as the constant increase in reverse voltage, sooner or later will cause diode damage. This can be added to the reverse voltage, not instantaneous voltage, but repeatedly added to the positive and negative voltage. Because the rectifier is added to the AC voltage, its maximum value is a specified important factor. Maximum reverse peak voltage VRM refers to the maximum reverse voltage that can be applied to avoid breakdown.

6. Maximum DC reverse voltage VR: the maximum reverse peak voltage above is the repeated addition of the peak voltage, and VR is the continuous addition of the DC voltage value. For DC circuits, the maximum DC reverse voltage is important for determining the allowable and upper limit values.

7. Highest operating frequency FM: because of the existence of the junction capacitance PN junction, when the operating frequency exceeds a certain value, its one-way conductivity will become worse. The FM value of the Schottky diode is relatively high, with a maximum of 100GHz.

8. Reverse Recovery Time TRR: when the operating voltage changes from a forward to a reverse voltage, the diode works ideally when the current can be cut off instantaneously. There is usually a slight delay. The amount that determines the current cut-off delay is the reverse recovery time. Although it directly affects the switching speed of the diode, it is not necessarily a small value. That is, when the Schottky diode suddenly reverses from conduction, the reverse current from a large attenuation to close to the time required for IR. This index is very important when the high-power switch tube works in the high-frequency switch state.

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