Power Diode Problem Introduction

1. What is the forward current rating of the power diode? The rated current of the diode is the main nominal value of the diode, such as a 5A/100V diode, and 5A is the rated current. Usually the rated current is defined as the rated average current that the diode can pass. However, some tests are square waves before the test, that is, the square wave current with an average value of 5A can be passed. Some of the test conditions are DC, which is the ability to pass 5A DC current. Theoretically, for a silicon diode, a diode with a square wave as a test condition can pass a larger DC current because the square wave of the same average current will cause more loss to the diode than the DC current. So can the 5A diode pass the 5A current? Not necessarily, this is temperature dependent. When your heat dissipation conditions are not good enough, the current that the diode can pass will be limited by the junction temperature.

2. What is the reverse rated voltage of the diode? When the diode is reverse-cut, it can withstand a certain back pressure, then its highest tolerable back pressure is the rated voltage. For example, a 5A/100V diode has a rated back pressure of 100V. Although all diode manufacturers will leave a certain margin, 100V diodes usually use 110V, there is no problem, but it is not recommended, because the manufacturer will not guarantee its reliability if it exceeds the rated value. The problem is that you The problem is. And many power design companies, in order to ensure reliability, will also deduct the design.

3. What is the forward current of the diode? Switching power supplies require a diode to withstand large inrush currents during startup or other transient conditions. Of course, this inrush current should be non-repetitive or long-interval. Usually the diode's data sheet defines this inrush current. The test conditions are often the inrush current of a single waveform, such as a single sine wave, or a square wave. Its current value can often reach several hundred A.

4. What is the forward voltage drop of the diode? The diode is in a forward conduction, and a voltage drop occurs when a current flows. This voltage drop is related to the forward current and temperature. Usually silicon diodes, the greater the current, the greater the voltage drop. The higher the temperature, the smaller the pressure drop. But the silicon carbide diode is the higher the temperature, the greater the pressure drop.

5. What is the reverse leakage current of the diode? When the diode is turned off in the reverse direction, it is not a perfectly ideal cutoff. When subjected to back pressure, some tiny current leaks from the cathode to the anode. This current is usually small, and the higher the back pressure, the larger the leakage current, and the higher the temperature, the larger the leakage current. Large leakage currents can cause large losses, especially in high voltage applications.

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