Why does the equivalent series resistance of aluminum electrolytic capacitors decrease as frequency increases?

乱世煮酒论天下

Why does the equivalent series resistance of aluminum electrolytic capacitors decrease as frequency increases? [Copy link]

Generally speaking, due to the influence of parasitic parameters, the loss will increase as the switching frequency increases, but aluminum electrolytic capacitors are a special case. Their equivalent resistance will decrease as the frequency increases, so the loss will decrease as the frequency increases. Why is this the case? Is the equivalent series resistance also related to the frequency? Could it be that in the equivalent circuit of the capacitor, the resistor, inductor and capacitor are connected in series, the frequency increases, the impedance of the entire equivalent circuit increases, the residual current decreases, and the loss of the equivalent resistor ESR decreases?

In this case, the frequency of the electrolytic capacitor must exceed the resonant frequency, and the overall performance is resistive-inductive. In this way, as the frequency increases, the impedance increases, the current decreases, and the loss on the equivalent resistance decreases.

maychang

[Could it be that in the equivalent circuit of the capacitor, the resistor, inductor and capacitor are connected in series, the frequency increases, the impedance of the entire equivalent circuit increases, the residual current decreases, and the loss of the equivalent resistor ESR decreases? ]

no.

The equivalent resistance of an electrolytic capacitor is mainly the resistance of the electrolyte. The electrolyte is not a solid but a liquid, and the conductivity of liquids deviates greatly from Ohm's law (gas conductivity does not follow Ohm's law at all). The equivalent resistance of an electrolytic capacitor also changes greatly with temperature. At low temperatures, it can be ten or even twenty times that of normal temperature, which is not the case with solid conductors. The change in the equivalent resistance of an electrolytic capacitor with frequency is also completely different from that of solid conductors.

qwqwqw2088

In addition to frequency, temperature is also an important factor affecting ESR.

乱世煮酒论天下

maychang posted on 2024-7-4 17:57 [Could it be the equivalent circuit of the capacitor, the resistor, inductor and capacitor are connected in series, the frequency increases, the impedance of the entire equivalent circuit increases, the residual current decreases, and the equivalent circuit...

The life of aluminum electrolytic capacitors decreases as the temperature increases. According to the empirical formula, the life span is halved for every ten-degree increase in temperature. What characteristics of aluminum electrolytic capacitors are affected by temperature, resulting in a reduction in service life?

Gen_X

The main influencing factor is the chemical properties.

When the frequency is low, chemical processes are involved, resulting in large internal resistance. When the frequency is high, the chemical reaction is too late and the nature of the capacitor is fully reflected.

The same is true for temperature. Increased temperature causes chemical properties to become active, which accelerates changes in the "insulating dielectric layer" and reduces its lifespan.

maychang

[url=forum.php?mod=redirect&goto=findpost&pid=3343277&ptid=1286783]The life of aluminum electrolytic capacitors decreases with increasing temperature. According to the empirical formula, the life of aluminum electrolytic capacitors is halved for every ten degrees increase in temperature. Temperature affects the life of aluminum electrolytic capacitors...

[What characteristics of aluminum electrolytic capacitors are affected by temperature, resulting in a reduction in service life? ]

As the temperature rises, the electrolyte dries up faster. When the electrolyte dries up, the capacity decreases or even becomes completely unusable.

se7ens

The supplier has previously provided ESR information

I haven't studied the relationship between ESR and frequency in detail.

Since it's an agent, I can't get any answer even if I ask.

And the design rules define the ESR at a fixed frequency.

吾妻思萌

maychang posted on 2024-7-4 17:57 [Could it be the equivalent circuit of the capacitor, the resistor, inductor and capacitor are connected in series, the frequency increases, the impedance of the entire equivalent circuit increases, the residual current decreases, and the equivalent circuit...

Early power supplies mostly used aluminum electrolytic capacitors. No wonder the performance was different when it was turned on and after working for a while.

Thank you, teacher, for being sensitive to the problem.