Solid capacitor replacement principle

SMD aluminum electrolytic capacitor

The principle of solid capacitor replacement All capacitors need to confirm the installation size before the substitution. The term is defined as ESR (commonly defined as the response speed and power loss of the charge and discharge action of the capacitor to stabilize the power supply voltage.
At present, most of the audio and video and computer products are equipped with the following groups of voltages of 12V, 5V, 3.3V, 2.5V, 1.8V, and 1.8V. First, we emphasize that the 5V power supply is mainly responsible for various types of input in the digital circuit system of the board. The power supply of the output interface has a relatively small distribution range and the damage rate of the capacitor is also quite low. Therefore, under normal circumstances, the computer board and the circuit board based on digital logic circuit can replace the 10V electrolytic capacitor with 6.3V capacitor in small batch repair and replacement.
Selection of withstand voltage: Due to the large error of aluminum electrolytic capacitor, there will be a large margin when designing withstand voltage. For example, 12V aluminum electrolytic capacitor is commonly used for 12V power supply, 10V is commonly used for 5V power supply, and 6.3V is used for 3.3V. 6.3V or 4V is selected below 3.3V (this is rare). This is the general rule chosen by the manufacturer. We will also see 25V aluminum electrolytic capacitors used on 12V power supply on the board, even in the CPU 1.45V filter. Part of the 10V electrolytic capacitor is seen. Therefore, the original aluminum electrolytic capacitor withstand voltage is only used as a reference. The only standard for selecting the capacitor withstand voltage is the voltage of the circuit. If a solid capacitor is used, as long as the circuit voltage is lower than the solid capacitor withstand voltage, There is no need to consider the margin (in fact, the capacitor designer has reserved the margin according to the common supply voltage)
The choice of capacity, the choice of capacitor capacity is determined according to the current in the circuit (ie power consumption), such as the CPU is the king of power consumption in the motherboard, we have seen dense electrolytic capacitors and high-frequency tiles around it Capacitance, also in the vicinity of the GPU of the graphics card. Also due to the large error of the electrolytic capacitor and the large capacity reduction after aging, there will be a large margin in the capacity selection. The capacity of the solid capacitor is hardly reduced, no need Considering the problem of capacity reduction after aging, the ESR value is obviously superior to that of the aluminum electrolytic capacitor, so there is a large space for the solid capacitor in the capacity selection. According to experience, it is generally possible to select one quarter or more of the aluminum electrolytic capacity. Of course, this value is not absolute, a slight deviation, it does not matter.
Everyone is familiar with electrolytic capacitors. The understanding of capacitors often only remembers the capacity and withstand voltage. It is true, but forgets the decisive factor about the quality of the capacitor [the material of the capacitor]. When the electrolytic capacitor is replaced, the volume is allowed. Under the pressure resistance close to the original model, high voltage replacement of low voltage, high capacity replacement of low capacity, are correct understanding, but in the choice of solid capacitors, can not follow the traditional replacement concept, due to the material And the process is different, in the case of the same withstand voltage and capacity, electrolytic capacitor and solid capacitor contrast, the volume of solid capacitor is more than double the electrolytic capacitor. Because the price of solid capacitor material is much more expensive than the material price of aluminum electrolytic capacitor, the more The bigger the price, the more expensive it is. It doesn't have to be that big. More importantly, the excellent performance of solid capacitors determines the small capacity to handle the harsher working environment.
The pure solid material determines its longer life and less error. Its factory parameters can remain unchanged after tens of thousands of hours of continuous operation. However, after working for two thousand hours in aluminum electrolytic capacitors, the electrolyte will slowly appear. Drying phenomenon, the capacity becomes smaller, and the circuit system will become unstable over time. If the operation slows down, the solid capacitor emphasizes low ESR, and the performance does not change at high temperature. So replace the solid capacitor, so don't feel old The capacity is not enough, the voltage will not be too low, these conceptual errors.
Said a lot, practical application examples:
1: CPU power supply type capacitor, this position is generally 6.3V-10 electrolytic capacitor.
According to the actual voltage of the CPU to replace, the CPU core voltage produced in the past five years has not been higher than 2.5V, all below 1.8V, if it is antiques, it is another matter.
It can be used for 6.3V 1500UF-6.3V 3300UF electrolytic replacement on the periphery of the CPU. It can be used with solid capacitors 4V 1200UF, 4V 1500UF, 2.5V1500UF, 4V 820UF and 2.5V 820UF. It can also be used for 2: 6.3V1500UF-2200UF (diameter 8MM) electrolysis for 3.3 V or 3.3V power supply parts, available solid capacitor capacity 330-820UF withstand voltage 4V or more. Such as the common 4V 560UF
3: 12V power supply 16V 1000UF--16V 3300UF Electrolytic usable solid capacitor 16V270UF 16V330UF (12V power supply is used as a high voltage circuit that does not directly supply large current, so the capacity available here is small)
4: The most commonly used 1000UF/6.3, widely distributed with memory slots, AGP slots, PCI slots, such electrolytic solids: withstand voltage higher than 4V capacity greater than 270UF, such as: 4V 560UF, 4V 470UF.
5: Other commonly used, 470UF/16V electrolysis available solid 180UF/16v
6: Replace a small electrolytic capacitor with 10V withstand voltage. Please use 6.3V or 10V withstand voltage solid capacitor. Since the chip with 5V power supply is not too much and the power consumption is not large, a small electrolytic capacitor is generally used.