Views: 7 Author: Site Editor Publish Time: 2018-01-17 Origin: Site
1. The larger the capacitance, the better.
Many people prefer to use large capacity capacitors in the replacement of capacitors. We know that the larger the capacitance, the stronger the ability to compensate for the IC's current. Not to mention the increase of capacitive capacity will increase the volume, increase the cost, but also affect the air flow and heat dissipation. The key lies in the parasitic inductance of the capacitor, and the capacitor discharge circuit will resonate at a certain frequency point. At the resonance point, the impedance of the capacitance is small. Therefore, the impedance of the discharge loop is small, and the effect of energy supply is very good. However, when the frequency exceeds the resonance point, the impedance of the discharge circuit increases and the current supply capacity of the capacitor starts to decrease. The larger the capacitance is, the lower the resonant frequency is, and the smaller the frequency range of capacitance can effectively compensate the current. From the point of view of ensuring the capacity of the capacitor to provide the high-frequency current, it is wrong to think that the bigger the capacitance is, the better, there is a reference value in the general circuit design.
2. For capacitors of the same capacity, the more small capacitors in parallel, the better.
Voltage, temperature, capacity and equivalent resistance is several important parameters of capacitance, and the lower the ESR is, the better. ESR is related to the capacitance, frequency, voltage, temperature and so on. When the voltage is fixed, the larger the capacity, the lower the ESR. The use of multiple small capacitors and connection in the card design is limited to the PCB space, so some people think that the lower the number of parallel small resistors, the better the effect. This is true in theory, but considering the impedance of the solder joint of the capacitor foot. The effect is not necessarily outstanding if several small capacitors are connected in parallel.
3. The lower the ESR, the better the effect.
In combination with our improved power supply circuit above, for input capacitors, the capacity of input capacitors is a little larger. Relative capacity requirements, ESR requirements can be reduced appropriately. Because the input capacitance is mainly voltage-proof, followed by the absorption of MOSFET switching pulse. For output capacitors, the voltage requirements and capacity can be appropriately decreased a bit. The ESR is a little more demanding because there is enough current to pass. But it is important to note that ESR is not the lower the better. Low ESR capacitance will cause switching circuit oscillation. The complexity of the damping circuit will also lead to the increase in the cost. In the card design, the AC motor capacitance, there is a reference here, this is the element selection parameters, to avoid vibration circuit and lead to a cost increase.
4.Good capacitors represent high quality.
"Only capacitive theory" once flourished, some manufacturers and the media also deliberately to make this matter a selling point. In the design of the board, the level of the circuit design is the key. And some manufacturers can use two-phase power supply than some manufacturers use four-phase power supply more stable products, blindly using high-priced capacitors, not necessarily good products. Measure a product, must be multi-faceted and multi-angle to consider, must not the function of capacitance intentionally or unintentionally exaggerated.