Views:1 Author:Site Editor Publish Time: 2018-04-16 Origin:Site
Because the working temperature of the capacitor is increased by 10 ℃ and the service life is halved, so don't think that the aluminum electrolytic capacitor with 2000 hours life is better than 1000 hours, we should pay attention to the test temperature of confirming the lifetime. Each manufacturer has a formula for calculating temperature and lifetime, which should be calculated with reference to actual data when designing capacitors. Need to understand is to improve the life of aluminum electrolytic capacitance, first, to reduce the operating temperature, far from the heat source in the PCB, the second consideration to use the highest operating temperature of the capacitor, of course, the price will be higher.
At a particular frequency, the resistance that blocks the passage of AC current is called impedance. It is closely related to the capacitance and inductance in the capacitance equivalent circuit, and it is also related to the ESR. The capacitance reactance of the capacitor decreases gradually with the increase of frequency in the low frequency range, and the reactance drops to the value of ESR when the frequency continues to increase to the intermediate frequency range. When the frequency reaches the high frequency range, the reactance becomes dominant, so the impedance increases with the increase of frequency.
The output filter electrolytic capacitor in the switching power supply has a sawtooth voltage frequency up to tens of kHz or even tens of MHz. At this time, the capacitance is not its main index. The standard of measuring the capacitance of high frequency aluminum electrolysis is the "impedance frequency" characteristic. It is required that there is a lower equivalent impedance in the operating frequency of the switching power supply, and it has a good filtering effect on the high-frequency peak signal generated by the semiconductor device.