Common problem
Four misconceptions in choosing electrolytic capacitors
Source：本站 | Time：2022-03-21 | Read：326
ShiCaXon Electronics shares with you the experience that can be operated when selecting and using capacitors: When the polarity of the line cannot be determined in the circuit, it is recommended to use electroless electrolytic capacitors. The ripple current through the electrolytic capacitor should not exceed the allowable range. If it exceeds the specified value, capacitors with high ripple current resistance should be used. The operating voltage of the capacitor should not exceed its rated voltage. When soldering the capacitor, the soldering iron should be kept at a certain distance from the plastic casing of the capacitor to prevent the plastic casing from breaking due to overheating. And the soldering time should not exceed 10 seconds, and the soldering temperature should not exceed 260 degrees Celsius.
When using capacitors, many friends will encounter the following misconceptions.
1, The larger the capacitor capacity, the better
??Many people often love to use large capacity capacitors in the replacement of capacitors. We know that the larger the capacitor, the better the ability to provide current compensation for the IC. Not to mention that the increase in capacitance brings about a larger volume, increasing costs while also affecting air flow and heat dissipation. The key lies in the presence of parasitic inductance on the capacitor, and the capacitor discharge loop will resonate at a certain frequency point. At the resonance point, the impedance of the capacitor is small. Therefore, the impedance of the discharge loop is minimal and the replenishment of energy is the best. However, when the frequency exceeds the resonance point, the impedance of the discharge loop starts to increase and the capacitor's ability to provide current starts to decrease. The larger the capacitance of the capacitor, the lower the resonant frequency, and the smaller the frequency range in which the capacitor can effectively compensate the current. From the point of view of ensuring the capacitor's ability to provide high frequency current, it is wrong to say that the larger the capacitor is, the better it is.
2, The more small capacitors are connected in parallel, the better the capacitance is.
??The ESR is related to the capacitance, frequency, voltage and temperature. When the voltage is fixed, the larger the capacity, the lower the ESR. In the board design using multiple small capacitors and connected more out with the PCB space limitations, so that some people think that the more parallel small resistors, the lower the ESR, the better the effect. Theoretically so, but to take into account the impedance of the capacitor pin solder joints, using multiple small capacitors in parallel, the effect is not necessarily outstanding.
3,The lower the ESR, the better the effect
??Combined with the power supply circuit, for the input capacitor, the capacity of the input capacitor should be larger. Relative to the capacity requirement, the ESR requirement can be reduced appropriately. Because the input capacitor is mainly voltage withstanding, followed by absorbing the switching pulses of MOSFETs. For the output capacitor, the requirement of voltage withstand and capacity can be lowered, while the requirement of ESR is higher, because here it is necessary to ensure the sufficient current throughput. However, it is important to note that ESR is not as low as possible, as low ESR capacitors can cause oscillations in the switching circuit. And de-oscillation circuit complex at the same time will lead to an increase in cost. In the board design, there is generally a reference value here, which is used as a parameter for component selection to avoid the increase of cost due to the de-oscillation circuit.
4,Good capacitance means high quality.
??The "only capacitance theory" was once in full swing, and some manufacturers and media also deliberately made this thing a selling point. In the design of the board, the level of circuit design is the key. And some manufacturers can use two-phase power supply to make more stable products than some manufacturers using four-phase power supply, the same, the use of high-priced capacitors, not necessarily to make a good product. ShiCaXon capacitors have been engaged in the R&D and production of capacitors for more than 15 years, and have obtained ISO9001 and other certificates for export to EU. , Email: carol@shicaxon.com or go to Alibaba store! Thank you for your trust and support!
When using capacitors, many friends will encounter the following misconceptions.
1, The larger the capacitor capacity, the better
??Many people often love to use large capacity capacitors in the replacement of capacitors. We know that the larger the capacitor, the better the ability to provide current compensation for the IC. Not to mention that the increase in capacitance brings about a larger volume, increasing costs while also affecting air flow and heat dissipation. The key lies in the presence of parasitic inductance on the capacitor, and the capacitor discharge loop will resonate at a certain frequency point. At the resonance point, the impedance of the capacitor is small. Therefore, the impedance of the discharge loop is minimal and the replenishment of energy is the best. However, when the frequency exceeds the resonance point, the impedance of the discharge loop starts to increase and the capacitor's ability to provide current starts to decrease. The larger the capacitance of the capacitor, the lower the resonant frequency, and the smaller the frequency range in which the capacitor can effectively compensate the current. From the point of view of ensuring the capacitor's ability to provide high frequency current, it is wrong to say that the larger the capacitor is, the better it is.
2, The more small capacitors are connected in parallel, the better the capacitance is.
??The ESR is related to the capacitance, frequency, voltage and temperature. When the voltage is fixed, the larger the capacity, the lower the ESR. In the board design using multiple small capacitors and connected more out with the PCB space limitations, so that some people think that the more parallel small resistors, the lower the ESR, the better the effect. Theoretically so, but to take into account the impedance of the capacitor pin solder joints, using multiple small capacitors in parallel, the effect is not necessarily outstanding.
3,The lower the ESR, the better the effect
??Combined with the power supply circuit, for the input capacitor, the capacity of the input capacitor should be larger. Relative to the capacity requirement, the ESR requirement can be reduced appropriately. Because the input capacitor is mainly voltage withstanding, followed by absorbing the switching pulses of MOSFETs. For the output capacitor, the requirement of voltage withstand and capacity can be lowered, while the requirement of ESR is higher, because here it is necessary to ensure the sufficient current throughput. However, it is important to note that ESR is not as low as possible, as low ESR capacitors can cause oscillations in the switching circuit. And de-oscillation circuit complex at the same time will lead to an increase in cost. In the board design, there is generally a reference value here, which is used as a parameter for component selection to avoid the increase of cost due to the de-oscillation circuit.
4,Good capacitance means high quality.
??The "only capacitance theory" was once in full swing, and some manufacturers and media also deliberately made this thing a selling point. In the design of the board, the level of circuit design is the key. And some manufacturers can use two-phase power supply to make more stable products than some manufacturers using four-phase power supply, the same, the use of high-priced capacitors, not necessarily to make a good product. ShiCaXon capacitors have been engaged in the R&D and production of capacitors for more than 15 years, and have obtained ISO9001 and other certificates for export to EU. , Email: carol@shicaxon.com or go to Alibaba store! Thank you for your trust and support!
