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 power down protection circuits. The Schottky diodes has a fast recovery speed and can be used in high-frequency situations, so the switching power supply uses this type of diodes as the rectifier output. However, the temperature of the rectifier tube on the switching power supply is still very high.

Common testing methods for voltage drop of Schottky diodes

Test with a "DCPOWERSUPPLY" instrument (constant current stabilized DC current): First, apply a low voltage to allow current to pass through theSchottky diodes, then slowly increase the current to reach the rated current of the measured Schottky diodes. Wait for the voltage value to stabilize before reading, and the stable reading is the voltage drop of the rated current.

Why is a 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 there is current passing through the Schottky diodes, the tube core will generate heat, which will be emitted through the tube body. When the Thermal equilibrium is reached (the heat generated by the tube core can be emitted in time), the impedance at this time is relatively stable, which is the Conservation of energy (P=I2R, P is converted into heat). If the rated current is directly used for testing, the initial reading is relatively high because the tube core is at room temperature and has the highest impedance. The reading will gradually decrease over time, which is because the impedance decreases with increasing temperature.

Common Mistakes in Testing Methods for voltage drop of Schottky diodes

Due to limitations in testing instruments, some users directly use a multimeter for testing. Although the multimeter has a range for testing diodes, its output current is only one or two milliamperes. The measured reading is not "internal resistance", but the voltage drop at milliampere level. Moreover, when testing the voltage drop of each batch of Schottky diodes using this method, the displayed reading may deviate greatly. Schottky diodes usually operate in ampere level, The difference between the two is a thousand times greater.