I would like to ask a basic question: Is the discharge speed of parallel capacitors determined by the ESR of the capacitors?

snowblind123

I would like to ask a basic question: Is the discharge speed of parallel capacitors determined by the ESR of the capacitors? [Copy link]

 

I would like to ask a basic question. Is the discharge speed of parallel capacitors determined by the ESR of the capacitor? 100HZesr is low, which means it discharges quickly at low frequencies. 100KHZesr is low, which means it discharges quickly at high frequencies. Does this mean that most switching power supplies, no matter how many W they are, are basically underpowered at low frequencies? If the capacitor is a 100000uf high-frequency, low-resistance electrolytic capacitor, will it also discharge quickly at high frequencies? Or has it already far exceeded the self-resonant frequency? Although it is high frequency and low resistance, it still discharges slowly?

maychang

Is the discharge speed of parallel capacitors determined by the ESR of the capacitors?

It is mainly determined by the load of the capacitor discharge. The load is usually much larger than the ESR, so the discharge speed is mainly determined by the load. Only when the load resistance is extremely small (short-circuit discharge) and the connection wire resistance can be ignored, the ESR will play a major role.

maychang

"Does this mean that most switching power supplies, regardless of how many watts they are, will basically have insufficient power at low frequencies?"

Are you powering a hi-fi system? Electronic devices rarely suffer from "underpowered" or "fast discharge".

snowblind123

maychang posted on 2022-4-25 11:20 "Does this mean that most switching power supplies, no matter how many watts they have, basically have insufficient power supply at low frequencies?" Are you powering a high-fidelity speaker? Electronic equipment is very...

It is to power the speakers. I feel that the low-frequency internal resistance of ordinary capacitors is very large, and a lot of them need to be connected to reduce the internal resistance. At present, I feel that supercapacitors have the lowest internal resistance.

maychang

snowblind123 posted on 2022-4-25 14:03 It is to power the speakers. It feels that the low-frequency internal resistance of ordinary capacitors is very large. Many capacitors must be connected in parallel to have a low internal resistance. At present, it feels that supercapacitors have the lowest internal resistance

I guessed correctly, "It's to provide power to the speakers."

The internal resistance of an actual capacitor (not an ideal capacitor) consists of two parts, one is capacitive, i.e., capacitive reactance, and the other is resistive, i.e., ESR. When you say "it feels like the internal resistance of an ordinary capacitor is very large at low frequencies", which part do you mean? Capacitive reactance is inversely proportional to frequency. The lower the frequency, the greater the capacitive reactance. When multiple capacitors are connected in parallel, the capacitance increases to n times the number of parallel connections, and the capacitive reactance decreases to one-nth. There is no doubt about this.

maychang

snowblind123 posted on 2022-4-25 14:03 It is to power the speakers. It feels that the low-frequency internal resistance of ordinary capacitors is very large. Many capacitors must be connected in parallel to have a low internal resistance. At present, it feels that supercapacitors have the lowest internal resistance

In another post, you mentioned a regulated power supply. Both linear regulated power supplies and switching regulated power supplies work best at low frequencies. A good regulated power supply can have a very small equivalent output resistance, even smaller than the resistance of a wire. If you want a good low-frequency response for your speakers, you should use a regulated power supply.

snowblind123

maychang posted on 2022-4-25 14:34 In another post, you mentioned the voltage stabilizer. Whether it is a linear voltage stabilizer or a switching voltage stabilizer, it works well at low frequencies. A good voltage stabilizer, ...

The configuration of high-current linear voltage-stabilized power supply capacitors is too difficult. I have been looking at many circuits and I am getting more and more confused. Even if a capacitor of several tens of PF is added to the power supply path, the sound will change greatly. The output internal resistance of linear power supplies is very low. Some circuits or voltage-stabilizing chips can run a large current of several A or even tens of A with only 0.1uf-1uf output capacitors, and very quickly. If the output capacitor is only 0.1uf or 1uf or 2uf, etc., I don't understand how to configure the capacitors of the rectifier and filter circuits. How to match the rectifier filter/input capacitor with the output capacitor?

snowblind123

maychang posted on 2022-4-25 14:30 I guessed right, "it is to power the speakers". The internal resistance of an actual capacitor (non-ideal capacitor) consists of two parts, one of which is the capacitor...

I think it's not a capacitive reactance problem, but a low-frequency esr. I connected a 76mm diameter disassembly screw capacitor with extremely low high- and low-frequency esr of about 4 milliohms to the computer CPU module line. The computer flew up fast. The low frequency was so strong that I could feel the sound of the current, which was comparable to the super farad capacitor. Haha, I played too weirdly. The low-esr screw capacitor was really too big.

chunyang

Ideal capacitors have “high frequency and low resistance”, but don’t forget that real capacitors also have an ESL parameter.

PowerAnts

maychang posted on 2022-4-25 14:30 I guessed right, "it is to power the speakers". The internal resistance of an actual capacitor (non-ideal capacitor) consists of two parts, one of which is the capacitor...

Those who encounter audio equipment will just take a detour, haha. Many years ago, I went back to the last topic about audio equipment. I suggested putting one of each type of capacitor in the world together, and then anyone who listens to it will be fascinated, because there must be a capacitor that he likes.

maychang

snowblind123 posted on 2022-4-25 22:06 The configuration of high-current linear voltage-stabilized power supply capacitors is really difficult. I have read many circuits and I am getting more and more confused. Even if a capacitor of dozens of PF is added to the power supply path...

"Even if a capacitor of several tens of PF is added to the power supply path, the sound will change dramatically."

I ignore any individual feelings that cannot be measured by instruments.

maychang

snowblind123 posted on 2022-4-25 22:13 I think it's not a capacitive reactance problem, but a low-frequency esr. I connected a 76mm diameter esr with extremely low high and low frequency esr of about 4 milliohms to the computer CPU module line...

"The low frequency is so strong that I can feel the sound of electric current"

PowerAnts said on the 10th floor: "If you encounter speakers, just take a detour." I also took a detour.

snowblind123

maychang posted on 2022-4-26 08:42 "Even if a capacitor of tens of PF is added to the power supply path, the sound will change dramatically." All personal feelings that cannot be measured by instruments, I...

Apple mobile phone power supplies often use capacitors of dozens of PF. TI's power supply reference design contains a huge number of high-frequency capacitors of different capacities. I have disassembled many finished brand switching power supplies. There are basically no high-frequency capacitors in the power supply path. The noise is huge. Many things can be seen and heard. It should also be possible to measure it with instruments. It seems that many equipment such as spectrum analyzers are required. For example, LC RC filtering must be used with high-frequency capacitors, otherwise there will be a lot of noise. Capacitors are connected in parallel according to the capacity ratio to minimize noise, etc. I don't understand

maychang

snowblind123 posted on 2022-4-26 10:13 Apple mobile phone power supplies often use capacitors of dozens of PF. TI's power supply reference design contains a huge number of high-frequency capacitors of different capacities. I have disassembled many of them...

"Apple phones often use capacitors of several dozen PF in their power supplies, and TI's power supply reference designs contain a huge number of high-frequency capacitors of different capacities..."

I've gone around it.

Chad4133

The resistance values of RC and RD affect the charging and discharging speed of the capacitor respectively. The product of the resistance value R and the capacitance value C is called the time constant τ, which describes the charging and discharging speed of the capacitor.