Traditionally, aluminum electrolytic capacitors and tantalum electrolytic capacitors have been widely used in smoothing and decoupling applications that require large capacitors. With the increase of capacitance value, MLCC is replacing various electrolytic capacitors in power circuits and other applications.
Replacing electrolytic capacitors with MLCC has various advantages, such as reduced space due to smaller size and thinner appearance, reduced ripple voltage due to low ESR, and improved reliability due to reduced self heating.
Electrolytic capacitors have a significant characteristic of having a relatively high ESR value. If the ESR is relatively high, it will be lost in the form of heating, so the heating of the electrolytic capacitor itself is quite serious. In addition, its ripple current is relatively high, which can also cause severe self heating. ESR, combined with ripple current, generates heat to a certain extent and accelerates the evaporation rate of the electrolyte. The capacity also decays, resulting in a vicious cycle.
The main feature of MLCC is its relatively long lifespan, and its performance is very consistent at high and low temperatures. Its characteristics do not differ significantly between high and low temperatures.
It should be noted that although low ESR is one of the advantages of MLCC, it may also lead to abnormal oscillation and anti resonance. In addition, the capacitance value of MLCC in high dielectric constant systems (Type 2) may change when applying DC voltage.
This guide will introduce you to the advantages and precautions of replacing electrolytic capacitors with MLCC.
Advantages of replacing aluminum electrolysis with MLCC
Advantage 1: Reduced space due to smaller size and lower profile
Advantage 2: Reduced self-heating
Advantage 3: Reduced ripple voltage
Main Features of MLCCs, Tantalum Electrolytic Capacitors, and Aluminum Electrolytic Capacitors
|
|
MLCC |
Tantalum Electrolytic Capacitors |
Aluminum Electrolytic Capacitors |
|
Advantage |
* samll size /low profile * Low ESR reduces ripple voltage and self-heating * non-polarized |
* High capacitance * Good DC bias characteristics |
* High capacitance * Good DC bias characteristics * Low price |
|
Notes |
* Due to its advantageously low ESR, abnormal oscillation or anti-resonance may occur
*-Products with high dielectric constant change their capacitance due to DC bias (DC voltage applied) |
* Relatively high ESR * Relatively high ripple voltage and self-heating |
* Large size * High ESR * High ripple voltage and self-heating * High temperature severely affects product life |
MLCCs offer various advantages such as space reduction due to smaller size and lower profile, reduction of ripple voltage due to lower ESR, and improvement of reliability due to reduced self-heating.
On the other hand, low ESR, which is an advantage of MLCCs, may cause abnormal oscillation or anti-resonance. Additionally, note that MLCCs of high dielectric constant (Class 2) exhibit a characteristic capacitance change with applied DC voltage.
Precautions when replacing aluminum electrolysis with MLCC
Note 1: DC bias (DC voltage applied) characteristics
Note 2: Abnormal oscillation
Note 3:Anti-resonance
Note 1: DC bias (DC voltage applied) characteristics
MLCCs of high dielectric constant (Class 2) have a characteristic of capacitance change when DC voltage is applied, and this characteristic is called the DC bias (DC voltage applied) characteristic.Therefore, DC bias characteristics should be considered when using MLCCs with DC voltage applied.
Example of DC Bias Characteristics of High Dielectric Constant MLCC
Note 2: Abnormal oscillation
Low ESR, which is an advantage of MLCC, can sometimes cause unstable output voltage or abnormal oscillation of the DC-DC converter. The DC-DC converter obtains a constant and stable DC voltage by comparing the output voltage to a reference voltage, amplifying the error difference by an error amplifier, and feeding it back negatively.
During this process, a phase delay is generated by the smoothing circuit's inductor and capacitor. When the phase delay approaches 180°, it becomes like a positive feedback, leading to unstable output voltage or abnormal oscillation.
Example of DC Bias Characteristics of High Dielectric Constant MLCC
Note 3: Anti-resonance
Furthermore, care must be taken when using low ESR MLCCs for decoupling purposes.
Generally, multiple capacitors are connected in parallel as decoupling capacitors for ICs operating at high currents and low voltages. For decoupling purposes, capacitors with low impedance over a wide frequency range are ideal, but the impedance frequency characteristics of MLCCs exhibit a V-shaped behavior.
The frequency at the bottom of the V is called the self-resonant frequency (SRF). When MLCCs with different SRFs are mounted in parallel, an LC parallel resonant circuit is formed by the capacitance and parasitic inductance component of the MLCCs. This phenomenon is called anti-resonance.
Anti-resonance causes intense impedance peaks, which reduces noise rejection at that frequency. As a result, the supply voltage can become unstable and circuit malfunctions may occur.
Disadvantages of MLCC:
1.Compared to electrolytic capacitors of the same capacity, the unit price of MLCC will be higher;
2. MLCC has a bias characteristic, and its capacity tends to decay with the applied voltage,
3.The capacity range of MLCC is relatively small, and MLCC cannot easily reach 2 million or million like electrolytic capacitors
Recommended Products for MLCC Replacement
You can check our recommended UF Capaciotrs MLCC products by selecting the type of electrolytic capacitor you are using.
UF Capacitors is an ISO9001-certified manufacturer in China, founded in 1995. We hold military qualifications for Aluminum Electrolytic Capacitors, tantalum capacitors, MLCC, and other products. Additionally, we have a UL-recognized test laboratory located at our factory site.
Our marketing position is to provide a superior alternative to first-tier brands such as TDK, Murata, AVX, EPCOS, Vishay, and Panasonic. We offer similar quality but at better prices, with faster lead times and excellent service. With extensive experience working with renowned international companies like GE, Philips, Jabil, and Flex, we have built a strong reputation.
How to Obtain a Quote from UF Capacitors?
You can easily send an email to lily@ufcapacitors.com, the engineering and sales team in UF Capacitors will help you select the correct polymer aluminum capacitors.
For more details, pls visit our website: www.ufcapacitors.com