How to judge the damage of fast recovery bridge

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How to judge the damage of fast recovery bridge [Copy link]

The fast recovery bridge is a rectifier device widely used in power electronic equipment, usually in circuits with high current requirements and fast recovery characteristics. Due to its fast switching characteristics, the fast recovery bridge performs well in high-frequency environments. However, with the increase of usage time or under inappropriate operating conditions, the fast recovery bridge may be damaged or its performance may degrade.

1. Judge by output voltage test
When the fast recovery bridge is suspected to be damaged, the most direct detection method is to measure its output voltage. The main function of the fast recovery bridge is to convert the input AC power into DC power. If the output voltage is abnormal, it is likely that there is a problem with the fast recovery bridge.
Test steps:
First, make sure that the device is powered off and physically check the fast recovery bridge to confirm that there is no obvious damage to its appearance.
Use a multimeter to measure the input voltage of the fast recovery bridge to ensure that the input voltage is normal.
Then measure the output voltage of the fast recovery bridge. Under normal circumstances, the output terminal should provide a stable DC voltage. If the measured output voltage deviates significantly from the expected value, such as too low, too high or no output, it may mean that the fast recovery bridge is damaged.
2. Judge by diode function test
The fast recovery bridge is composed of multiple fast recovery diodes. The characteristics of these diodes directly determine the performance of the fast recovery bridge. The working status of these diodes can be tested one by one through the diode test function of the multimeter.
Test steps:
Adjust the multimeter to the diode test mode.
Test the forward voltage drop of each diode in the fast recovery bridge one by one, which should usually be between 0.2V and 0.8V.
If the forward voltage drop of a diode is 0 or infinite, it means that the diode may be short-circuited or open-circuited, causing the fast recovery bridge to fail.
3. Judge by switching characteristic test
One of the key performances of the fast recovery bridge is its fast recovery characteristic, that is, the recovery time between switching states is very short. Therefore, the switching characteristics of the fast recovery bridge can be measured to determine whether it is working properly.
Test steps:
Use an oscilloscope or other high-frequency test equipment to measure the waveform characteristics of the fast recovery bridge during the switching process.
Check the recovery time parameter (trr). Generally, the recovery time of the fast recovery diode should be between tens of nanoseconds and hundreds of nanoseconds.
If the measured recovery time is significantly longer than the typical value in the specification, or the waveform is abnormal, such as excessive ringing or noise, it may indicate that the fast recovery bridge is damaged.
4. Judge by temperature monitoring
When the fast recovery bridge works under high frequency and high current conditions, a certain amount of heat will be generated. If a diode is damaged or its performance deteriorates, it will cause a significant increase in heat. Therefore, temperature abnormality can also be used as an important basis for judging whether the fast recovery bridge is damaged.
Test steps:
Let the device run for a period of time under normal working conditions, and use an infrared thermometer or thermal imager to measure the temperature distribution of the fast recovery bridge.
Under normal circumstances, the temperature of the fast recovery bridge should be uniform and within a safe range. If the temperature of a certain area rises abnormally, it may mean that the internal diode is damaged, resulting in local overheating.
5. Judge by appearance inspection and smell
Although the damage of the fast recovery bridge usually does not show obvious changes in appearance, when it is severely damaged, it may appear burning, cracking, and even accompanied by a pungent smell.
Inspection points:
Check whether there is obvious physical damage to the appearance of the fast recovery bridge, such as burn marks, package cracks, etc.
Before electrical testing, olfactory inspection can also provide some clues, especially when the equipment fails, the damage of the fast recovery bridge is usually accompanied by an obvious burnt smell.
The judgment of the damage of the fast recovery bridge requires a combination of multiple test methods, including voltage measurement, diode testing, switch characteristic testing, temperature monitoring, and appearance inspection.