The Role of Capacitors in Power Supply
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Author:pmo646c82
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Published time: 2019-06-21
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Capacitor is one of the key passive components to realize the combination of voltage and current in a wide range of power supply. Although each capacitor can store electrical energy, dielectric technology plays an important role in the selection of capacitors for specific applications.
3: EMI/RFI suppression These capacitors are connected to the input end of the power supply to mitigate electromagnetic or radio interference caused by semiconductors. These capacitors are vulnerable to destructive overvoltage and transient voltage due to their direct connection to the main input line. As a result, different safety standards have been introduced in various parts of the world, including EN132400 in Europe, UL1414 and 1283 in the United States, and CSAC 22.2NO.0, 1 and 8 in Canada. X-level and Y-level capacitors using plastic film technology (such as EPCOSB3292X/B81122) provide one of the cheapest suppression methods. The impedance of the restraining capacitor decreases with the increase of frequency, allowing high frequency current to pass through the capacitor. X capacitor provides "short circuit" for this current between lines, while Y capacitor provides "short circuit" for this current between lines and grounding equipment. According to the peak value of surge voltage, X and Y capacitors are classified in more detail. For example, the rated peak surge voltage of an X2 capacitor with capacitance value up to 1_F is 2.5KV, while that of an X1 capacitor with similar capacitance value is 4KV. The appropriate level of interference rejection capacitor should be selected according to the peak voltage during load interruption. All kinds of capacitors in control and logic circuits are used in power supply control circuits. These capacitors are universal components with low voltage and low loss unless they are in harsh environment. High temperature components are usually used for power supply in harsh environments. For industrial or professional power supply, low ESR components such as EPCOSB45294 series can be selected, which is a good choice when requiring higher overall reliability. In order to make use of the automation of assembly, the reduction of size, the decrease of assembly cost and the increase of productivity, most designers try to follow the SMD capacitor technology used in the control circuit. However, there are not a few engineers who choose hybrid technology to take full advantage of the much lower cost of some lead elements.
