How to use a multimeter to measure the quality of fast recovery diodes

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How to use a multimeter to measure the quality of fast recovery diodes [Copy link]

Fast recovery diodes are widely used in power circuits and switching power supplies. Their fast recovery characteristics make them excellent in high-frequency applications. However, diodes may fail due to overload or aging during use, so it is important to check their working status regularly.

1. Understand the basic characteristics of fast recovery diodes
The main characteristic of fast recovery diodes is their short reverse recovery time, usually between a few hundred nanoseconds and a few microseconds. Compared with ordinary diodes, fast recovery diodes can stop conducting more quickly, thereby reducing switching losses. Before measuring, it is crucial to understand the pin configuration of the diode, which is usually divided into an anode and a cathode.
2. Preparation
Before starting the measurement, you need to prepare the following tools and materials:
a digital multimeter (DMM)
a known good fast recovery diode (as a comparison)
a workbench and appropriate tools
3. Measurement steps
Power off: Before measuring, make sure the circuit is powered off to avoid damage to the multimeter and yourself.
Identify the pins: Confirm the anode and cathode positions of the fast recovery diode. Usually, there are marks or stripes on the cathode side of the diode.
Set up the multimeter: Set the multimeter to the "diode" test mode. This mode will emit a small current to detect the conduction characteristics of the diode.
Measure forward conduction:
Connect the red probe of the multimeter to the anode and the black probe to the cathode.
Read the value of the multimeter. For a normal fast recovery diode, a lower forward voltage drop should be displayed, usually between 0.6V and 1.0V. If it displays "OL" or infinity, it means that the diode is open.
Measure reverse impedance:
Connect the red probe of the multimeter to the cathode and the black probe to the anode.
At this time, the multimeter should normally display "OL" or a high resistance value, indicating that the diode is not conducting in the reverse direction. If it displays a low resistance value or close to zero, it means that the diode is short-circuited.
Dynamic test (optional):
If conditions permit, the reverse recovery characteristics of the fast recovery diode at the operating frequency can be tested by an oscilloscope. This step requires more professional equipment and knowledge.
4. Determine the quality of the diode
Normal state:
The forward conduction voltage is within the normal range.
The reverse impedance is high and displays "OL".
Open circuit fault:
Displays "OL" when measuring in the forward direction.
It may display a high resistance value when measuring in the reverse direction.
Short circuit fault:
Displays a low resistance value or close to zero when measuring in the forward direction.
Displays a low resistance value when measuring in the reverse direction.
Through the above steps, the multimeter can be effectively used to measure the quality of the fast recovery diode. Regularly checking the status of the diode can not only extend the service life of the equipment, but also improve the stability and safety of the circuit. In practical applications, if a problem is found in the diode, it should be replaced in time to avoid affecting the entire circuit.