Common testing methods for voltage drop of Schottky diodes

Common testing methods for voltage drop of Schottky diodes

The advantages of Schottky diodes are low impedance, small forward voltage drop, and fast recovery speed, so they are commonly used in high-frequency high current rectification and voltage drop protection circuits. Schottky diodes have a fast recovery speed and can be used in high-frequency situations, so switching power supplies use this type of diode as a rectifier output. However, the temperature of the rectifier diode on the switching power supply is still very high.

The commonly used testing method for voltage drop of Schottky diodes is to use the "DCPOWERSUPPLY" instrument (constant current stabilized DC current) for testing: first, apply a small voltage so that there is current passing through the Schottky diode, then slowly increase the current to reach the rated current of the tested Schottky diode, wait for the voltage value to stabilize before reading, and the stable reading is the voltage drop of the rated current.

Why is the stable voltage reading the correct voltage drop reading: The impedance of Schottky diodes is not fixed, but decreases with increasing temperature (non-linear relationship).

When a current passes through a Schottky diode, the die generates heat, which is then dissipated through the body. When thermal equilibrium is reached (the heat generated by the die can be dissipated in a timely manner), the impedance is relatively stable, which is the law of conservation of energy (P=I2R, P is converted into heat). If tested directly with rated current, the initial reading is relatively high because the core is at room temperature and has the highest impedance. The reading will gradually decrease over time because the impedance decreases with increasing temperature.

Common misconceptions in testing the voltage drop of Schottky diodes

Some users, due to limitations of the testing equipment, directly use a multimeter for testing. Although the multimeter has a diode testing section, its output current is only one or two milliamps. The reading it tests is not the "internal resistance", but the voltage drop when the current is in the milliampere level. Moreover, when using this method to test the voltage drop of each batch of Schottky diodes, the displayed reading may deviate greatly. Schottky diodes usually operate at ampere level currents, with a difference of thousands of times between the two