When the SMT thick film resistor withstand voltage is not properly selected, the system design may be damaged due to the breakdown of the resistor. At the input end of the AC-DC switching power supply module, after the plug or connector is disconnected, the residual voltage on the input terminals L and N is attenuated to 37% of the initial value within 1S. Therefore, one or two MΩ-level impedance resistors are generally used for energy bleed in design, and the input terminal is high voltage, that is, both ends of the resistor are subjected to high voltage, and when the resistance of the resistor is low voltage input high voltage in the case of a failure, there will be a failure.
Second, choose twice the power of SMT thick film resistor
For example, in actual use, if the current flowing through the resistor in the circuit is 100 mA and the resistance is 100 Ω, then the power consumption on the resistor is 1 W. Choosing a common chip resistor, such as a package of 0805 or 1206, is not suitable. Used in this circuit, it will burn out due to the low rated power of the resistor. Therefore, the rated power of the selected resistor should be more than 1W, that is, the power margin of the circuit design selection resistor is generally more than 2 times, otherwise the power consumed by the resistor will cause the resistor to overheat and fail.
By handling the above two points, the SMT thick film resistor can be used safely, and the number of failures can be avoided in the circuit design. The entire test circuit can be burned due to the damage of the SMT thick film resistor in the relevant test environment.
