I don’t know if you have ever encountered such a situation. The circuit fails for no reason, the circuit looks intact, or a large piece of it may have been burned. Before you rack your brains, you might as well put your eyes on the little resistance.
The possible reasons for the damage of the chip resistor are:
1. The resistance is too close to the power transformer, and the line impedance at both ends is very small. The inverter is not equipped with a DC reactor and an AC reactor on the output side, so that the rectifier bridge is under the impact of the high amplitude spike current of capacitor filtering, resulting in the rectifier bridge damage.
2. The voltage of the power grid becomes high instantaneously, lightning strikes or excessive surge voltage is encountered, and the internal resistance of the power grid is small, and the protection of the grid resistance after breakdown and burnout does not work, causing all overvoltages to be applied to the rectifier bridge.
3. The back-stage circuit and the inverter power switching device are damaged, causing the rectifier bridge to flow through the short-circuit current and be damaged.
4. The output current and voltage are too low, which reduces the burden on the rectifier bridge and damages it.
5. The quality of the purchased product is not good enough.
Problems that SMD resistors may encounter in life:
1. What is the electrode structure and how to deal with electroplating
Both ends of the chip resistor are installed with external electrodes, and the external electrodes are a 3-layer structure made on a ceramic substrate. One layer is plated with nickel, the second layer is silver-based thick film material, and the third layer is tin-plated. , The chip resistor is a product that fully meets the requirements of lead-free.
2. Pulse limited power
The pulse limit power of the chip resistor is not directly related to the pulse time, but is specified according to the high voltage of the chip resistor's rated power. If it is a single pulse, one data can be used to give a negative limit value. If it is a continuous pulse, one data can also be used as a reference value to give a qualified limit value within the corresponding range of the trial device.
Third, the resistance value of the chip resistor
Although there is a resistance called 0 ohm on the market, as long as it is a conductor, it must have a resistance value. A 0 ohm resistor also has a resistance value, but it is very small, so it is called 0 ohm. Although the size of the chip resistors has different resistance values, they are all below 50mΩ.