Electrolytic Capacitors: Comprehensive Overview, Teardown, and Experiments

this video is brought to you by Nippon chemicon I finally got sponsored by Nippon chemicon they have the biggest market share of electrolytic capacitors in the world firstly an important update the brand name of Nippon chemicon will change the brand name used to be Nippon chemicon same as the company name but from today it's chemical at the same time the logo also changes to chemicon when you use electrolytic capacitors and see their logo please remember that their brand name has changed as for the company name it will still be Nippon chemicon today I'm going to talk about electrolytic capacitors firstly what kind of products are they used for let me explain almost all power supplies use electrolytic capacitors here's an ATX power supply for home built computers let's have a look inside this component which is the first thing you see when you open the lid is an electrolytic capacitor there's a chemicon logo there's this large one here and at the back of the circuit board there are electrolytic capacitors with light blueprints these capacitors are conductive polymer aluminum solid capacitors high performance ones if you look closely only the frame part of the chemicon logo is printed the roles of these electrolytic capacitors are stabilizing voltage and supplying power even when the voltage from the outlet fluctuates this electrolytic capacitor can keep supplying power if the electric load changes abruptly the voltage stays the same thanks to the electrolytic capacitors in the output part as you can see electrolytic capacitors play a very important part in supplying power these days there is a trend towards replacing electrolytic capacitors with film capacitors and multi-layer ceramic capacitors however for power supplies I'm guessing they'll keep using electrolytic capacitors especially for this part of the power supply it's because an electrolytic capacitor can store a lot of energy capacitors in a power supply unit must withstand momentary power outage for one or two cycles if you use something other than an electrolytic capacitor it can't store enough energy to supply stable power to the load if you want the same rated voltage and capacitance electrolytic capacitors are a lot better in terms of price and size it depends on the design and many other factors so you can't generalize but I want to say electrolytic capacitors are still very useful for power supplies okay let's go into today's main topic the types of aluminum electrolytic capacitors here are three types of aluminum electrolytic capacitors can you tell the difference the one on the left is an aluminum electrolytic capacitor the most common type electrolyte is inside the one in the middle is a conductive polymer aluminum solid capacitor it doesn't contain electrolyte the one on the right is a conductive polymer hybrid aluminum electrolytic capacitor it contains both electrolyte and conductive polymers I'm going to disassemble them to see the difference firstly a regular aluminum electrolytic capacitor let's look inside something in the shape of a roll came out if you squeeze it you can see some liquid seeping out this is electrolyte even small aluminum electrolytic capacitors contain electrolyte the liquid seeps out like this when you squeeze it this is electrolyte let's see the structure electrodes and paper are wound in the roll they're rolled to the end aluminum electrolytic capacitors are basically made of aluminum foil and paper this is the anode aluminum foil and this is the cathode aluminum foil between them is a piece of paper called separator there's another piece of paper behind the cathode aluminum foil the surface of the anode and cathode foils look slightly different you can't see with the naked eye but if You observe the surface under an electron microscope you can see bumps the bumps expand the surface area the anode aluminum foil has its surface treated and then oxidized when the surface is oxidized it becomes aluminum oxide which works as dielectric the capacitance won't be that much if you only put separators between the foils that's why the paper is soaked with electrolyte the electrolyte serves as the actual cathode the electrolyte in the paper permeates into the surface of the node aluminum foil which makes the surface area a lot bigger this is why the capacitance of the electrolytic capacitor is very big let me explain using a whiteboard this is the anode aluminum foil this is the cathode aluminum foil this is the electrolytic paper which works as a separator the anode aluminum foil is treated to have rough surface which increases its surface area after the treatment the surface is oxidized to become aluminum oxide which is dielectric at this stage the capacitance is actually not that big however there's electrolyte in here it permeates into the uneven surface of the node aluminum foil surface which makes it possible to effectively utilize the large surface area of the foil this is why the electrolyte in electrolytic capacitors is called the actual cathode thanks to the electrolyte which fits the roughenode surface perfectly the capacitance of electrolytic capacitors is very large I drew an equivalent Circuit of a capacitor in addition to a capacitance it includes an inductance element and a resistance element especially the ESR equivalent series resistance is very important I'll talk about it later so please remember this term the ESR affects the capacitor loss and voltage Ripple next let's take a look inside the conductive polymer aluminum solid capacitor this is what's inside conductive polymers serve as electrolyte it's solid if you squeeze the roll no liquid comes out pretty stiff the container is not equipped with a pressure valve since this capacitor doesn't use electrolyte the internal pressure won't go up I'll unwind the roll as you can see the roll is stuck very firmly you can hear the sound as I unwind the roll because there's no electrolyte between the electrolytic paper and aluminum foil they have to be attached together very firmly you can see there's a big difference between this one and the aluminum electrolytic capacitor that we saw earlier there's no liquid inside it's completely solid a conductive polymer aluminum solid capacitor does not contain electrolyte you don't have to worry about liquid leakage because of that however self-healing hardly occurs since there's no electrolyte it's the downside another feature of this capacitor is the low ESR which means the performance is good finally let's look at a conductive polymer hybrid aluminum electrolytic capacitor this is what's inside a hybrid of conductive polymers and electrolyte if you squeeze it the electrolyte seeps out thus it's a hybrid the basic structure is the same as the electrolytic capacitors we saw earlier this capacitor gets the best of both aluminum electrolytic and aluminum solid capacitors the ESR is low and since electrolytes inside a degraded aluminum foil will be self-healed let's learn about the ESR of an electrolytic capacitor using this circuit this part is a simple equivalent Circuit of an electrolytic capacitor this is a circuit of a buck converter charging and discharging current is always flowing in the electrolytic capacitor because of this charging and discharging current the ESR produces heat inside the capacitor the heat causes the evaporation of the electrolyte inside the capacitor which makes the lifetime shorter naturally we want to produce less heat how for example connect another electrolytic capacitor in parallel consider esr2 then what happens to the current flowing in each capacitor it's halved which means the loss caused by the ESR will be one-fourth you can reduce the heat by splitting the current even when you use smaller electrolytic capacitors with twice more ESR they will generate only half the heat another effective idea is to design a circuit that places the capacitor far from heat producing elements in this circuit the inductor power semiconductors and the heat sinks of the power semiconductors it's important to keep the capacitor away from such heat sources so it won't be affected by heat if you design the circuit with these ideas in mind electrolytic capacitors will last 10 or 15 years a lot longer than you think on data sheets they say electrolytic capacitors withstand only 10 000 hours or so but it's a lifetime under very severe condition if you design the circuit considering cooling capacitors will have a lot longer lifetime now let me talk a little bit about the lifetime of an electrolytic capacitor a capacitor with electrolyte in it often ends its life when the electrolyte evaporates the electrolyte evaporates and gradually leaks from the Rubber seal in the form of gas as the capacitor dries out its capacitance decreases in the case of an electrolytic capacitor with conductive polymers in it oxygen gets inside and oxidizes the conductive polymers which causes degradation that's the first Factor another factor is self-produced heat conductive polymers degrade due to heat the heat is generated from the ESR generally electrolytic capacitors especially the ones that use electrolyte are said to have a short lifetime it's because they are used at high temperature which makes the electrolyte evaporate quickly when the electrolyte evaporates the capacitance gets lower and the capacitor ends its life also never short-circuit a capacitor when you discharge it it shortens the capacitor's life usually resistors are used for discharging but this time as an experiment I'm going to Short Circuit to discharge the capacity the voltage is only 15 volts so I don't think it'll be too bad it's dangerous do not short-circuit a capacitor now I'd like to do some experiments using the three types of capacitors we've been seeing I'll swap the output capacitor of this Buck converter and measure the Ripple voltage each time here are three types of capacitors with almost the same capacitance an aluminum electrolytic capacitor with 234 microfarad capacitance an aluminum solid electrolytic capacitor with 273 microfarad capacitance and a conductive polymer hybrid aluminum electrolytic capacitor with 300 microfarad capacitance firstly I'll attach the regular capacitor let's see the Ripple voltage if you zoom in you can see the Ripple voltage is about 80 millivolts next the conductive polymer aluminum solid capacitor the Ripple voltage is a lot lower this time see here it's around only 25 millivolts Peak to Peak the capacitance is about the same as the regular one but the Ripple voltage is lower finally the hybrid aluminum electrolytic capacitor look at the waves this capacitor also has lower Ripple voltage compared to the regular capacitor it's about 30 millivolts the amount of Ripple voltage is completely different depending on the type of capacitor this is because of the ESR that I explained earlier in order to reduce the Ripple voltage of a regular capacitor to the same as the other capacitors with the circuit used for this experiment the capacitance needs to be about 680 microfarad even then the Ripple voltage is higher than when a conductive polymer capacitor was used so in the case where you need to place a circuit in a small space use solid or hybrid aluminum electrolytic capacitors you may wonder if ESR should be as small as possible but that's not always the case especially when a voltage regulator is equipped with a low ESR capacitor like in this experiment the operation gets a bit unstable this is a bit off topic more about control engineering but it's because the control of the DC DC converter and the circuit parameters affect each other in such cases you can simulate the experiments using chemicon spice model you can reduce the rework that occurs in experiments with actual equipment you can find the link in the description when using an electrolytic capacitor you definitely should avoid reverse polarity wrong polarity can actually destroy capacitors be sure to connect the wires to the right polarity especially when you assemble the circuit yourself before powering on make sure that the polarity is correct now to raise alert let's see what happens if the polarity is reversed if the polarity is reversed leakage current flows in the capacitor which generates gas inside and the internal pressure increases then the pressure valve opens and the electrolyte spews out ouch a capacitor damaged by reverse polarity is very hot do not touch it by the way chemicon capacitors have several types of pressure valves this one has a cross pressure valve and this one has a triangle pressure valve that looks like a German vehicle logo they are easy to remember next let's see how the characteristics of an electrolytic capacitor change depending on the temperature I prepared an electrolytic capacitor buried in dry ice I'd like to compare the discharge characteristics of this ice capacitor with one at room temperature I'll add a discharge resistor in parallel with the capacitor and see the discharge characteristics first the capacitor at room temperature there you can see a normal RC discharging curve next let's see the discharge characteristics of this capacitor in dry ice this Red Wave represents the one cooled with dry ice let's see what happens there see the yellow wave represents the capacitor at room temperature and the Red Wave represents the cooled one their discharge characteristics are completely different in the case of the cooled capacitor the voltage drops abruptly to zero why does this happen this is because the electrolyte inside the capacitor is Frozen with frozen electrolyte the capacitor no longer functions we used a regular aluminum electrolytic capacitor for this experiment what happens if we use a solid capacitor or hybrid capacitor let's see in the case of a solid electrolytic capacitor the discharge characteristics hardly changes this is because the capacitor doesn't contain electrolyte it's all solid so there's nothing that could freeze inside therefore the discharge characteristics don't change much lastly a hybrid aluminum electrolytic capacitor this one's also working a hybrid aluminum electrolytic capacitor contains electrolyte but it also contains conductive polymers so the capacitor works even in this environment the cold one is discharging a little faster though the capacitance seems to be a bit lower foreign I think the electrolytes Frozen inside as we've seen so far a regular electrolytic capacitor doesn't function in an extremely cold environment other types of capacitors such as conductive polymer capacitors and hybrid capacitors are not so much affected when you actually use capacitors in such environments I recommend performing cooling experiments and reading data sheets beforehand so we experimented with aluminum electrolytic capacitors we've seen several types including conductive polymer solid capacitors and hybrid capacitors each type has its own characteristic and usage so I hope you'll find what environment they're suited for the best way to learn is to read catalogs everything important is written in here also don't forget Nippon chemical changed its brand name to chemicon when you come across this new logo remember they changed the logo thanks for watching

Channel: DENKI OTAKU

Views: 3,260

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Id: MAP-VA1m-A4

Length: 16min 30sec (990 seconds)

Published: Fri Apr 21 2023