Source: EPCI
EPCI aims to become useful educational and information resource of information, technical materials. links and references on passive components. Here is an overview of top ten articles read on EPCI website in 2018. Majority of the top articles have been adopted from its original source by Capacitor Faks blog, EPCI co-operation web site and our recommended link.
1. Ripple Current and its Effects on the Performance of Capacitors
The power dissipated by a capacitor is a function of ripple current and equivalent series resistance. As such, the ripple current capability is one of the key parameters to consider when selecting a capacitor for a specific application. Other critical parameters include capacitance, voltage rating, equivalent series resistance, and equivalent series inductance.
The article provides overview on ripple current consideration on tantalum, aluminum, ceramic and film capacitors. Link here.
2. Capacitor Selection for Coupling and Decoupling Applications
In circuits, capacitors are used for a wide range of applications including storing electrical charges, blocking DC components, bypassing AC components, filtering unwanted signals, and so on. The applications of a capacitor primarily depend on its characteristics.
Key properties to consider when selecting a capacitor for a given application include capacitance value, voltage rating, frequency response characteristics, cost, and physical size. Other properties of a capacitor that can influence the performance of an electronic circuit include temperature characteristics, self-healing properties, aging, and flammability.
The article discuss coupling and decoupling capacitor needs and selection guide. Link here.
3. 4 types of capacitor for filtering applications in switch mode power supply systems
Capacitors are essential components of a switch mode power supply system. Both the input and output stages of a SMPS system have capacitors. At the input, a rectifier and a capacitor are used to convert AC voltage to DC voltage. The output stage consists of an LC filter, a combination of a capacitor and an inductor, that removes noise and ripple voltages.
A typical switch mode power supply system has the following key components: an input rectifier, an input filter, power switches, a power transformer, an output rectifier, output filters, and a control circuit. The input and output filtering capacitors of a SMPS are selected depending on the electrical performance requirements. These capacitors significantly determine the reliability of a SMPS system.
Application of aluminum, tantalum, ceramic and film capacitors in SMPS are discussed in the article. Link here.
4. Leakage current characteristics of capacitors
Capacitors, just like other electronic components, are constructed with imperfect materials. The imperfections and defects in these materials have significant effects on the electrical performance of capacitors. Some of the parameters determined by these defects and imperfections include impedance, dissipation factor, inductive reactance, equivalent series resistance, and leakage current. When designing an electronic circuit, it is necessary to consider these characteristics.
DC leakage current is one of the key characteristics to consider when selecting a capacitor for your design. Other important parameters include working voltage, nominal capacitance, polarization, tolerance, and working temperature.
The article provides a quick overview of key influence of DCL to capacitor performance, DCL with time, voltage and temperature. Link here.
5. Get the lowdown on shelf life and storage of capacitors
In many electronic devices, the capacitors are the life-limiting components. Whereas the operational life of a capacitor is dependent on both electrical factors and environmental factors, the shelf life is mostly determined by storage conditions. The shelf life of most capacitors depends on environment factors such as humidity, temperature, and atmospheric pressure. Subjecting capacitors to harsh conditions can significantly affect their electrical properties, or even damage them completely.
The article briefly explains shelf life on aluminum, tantalum and ceramic capacitors. Link here.
6. The dielectric constant and its effects on the properties of a capacitor
A typical capacitor comprises two conductive plates and a non-conductive dielectric material. The dielectric material separates the two conductive metal electrode plates. Applying voltage to the electrode plates of a capacitor causes an electric field in the non-conductive dielectric material. This electric field stores energy. The dielectric constant, also commonly known as relative permittivity, is the measure of the ability of a material to store electrical energy, and is one of the key properties of a dielectric material.
The article explains basics of dielectric constant and present a brief overview of common dielectric types. Link here.
7. ESR losses in capacitors explained
In electronic circuits, capacitors are used for a wide range of applications including coupling, decoupling, filtering, and bypassing applications. Failing to select the correct capacitor can lead to excess power dissipation, excessive noise, circuit instability, unpredictable performance, and shorter product life.
A practical capacitor is a non-ideal component. Its circuit model contains series inductance (ESL) and series resistance (ESR). Although equivalent series resistance is often shown in circuit models as a constant value, it varies depending on operating conditions. ESR is resistance from a combination of energy loss mechanisms under specific operating conditions.
Some energy losses within a capacitor can be attributed to the conductors while others involve the dielectric material. These losses vary mainly depending on voltage and temperature. The most common energy loss mechanisms include dielectric losses, ferroelectric losses, dielectric conduction losses, interfacial polarization, partial discharge losses, ohmic resistance losses, sparking between conductors, electromechanical losses, and eddy current losses.
The article explains energy loss mechanisms in capacitors and ESR of tantalum, ceramic and aluminum capacitors. Link here.
8. What is a Dielectric Constant of Plastic Materials ?
Dielectric properties of a polymer film capacitors largely depend upon their structure. The structure determines whether a polymer is polar or non-polar and this in turn decided the electrical properties of the polymer.
Polar plastics have a tendency to absorb moisture from the atmosphere. Presence of moisture raises the dielectric constant and lowers the resistivity. With rise in temperature, there is faster movement of polymer chains and fast alignment of dipoles. This invariably raises the dielectric constant values for polar plastics. Non-polar plastics are not affected by moisture and rise in temperature.
The article describes dielectric constant of plastic materials, how to calculate it and factors affecting it. Link here.
9. Short Tutorial: RF Choke vs. Inductor
Inductors and RF chokes are basically the same type of electrical components. The difference in design is related to the function the device will perform in a circuit. Most engineers are more familiar with inductors – some think both devices can be used interchangeably – that are prevalent in frequency selective systems, such as a tuner for radio receivers or filters. Strictly speaking, ideally an RF choke is an inductor that rejects all frequencies and passes only DC.
The article briefly discuss RF choke and inductor differences and applications. Link here.
10. Effects of ESL on the performance of capacitors
In theory, capacitors are commonly considered as ideal components. However, practical capacitors are non-ideal and contain parasitic elements that can significantly affect their performance. These non-ideal characteristics are mainly dependent on materials and construction methods. The equivalent circuit model of a practical capacitor consists of equivalent series resistance (ESR), equivalent series inductance (ESL), and insulation resistance. The electrodes and the leads of a capacitor contribute the resistive component and the inductive component while the dielectric material contributes the insulation resistance.
The article provides some basic explanation and an overview of parasitic inductance on tantalum, ceramic and aluminum capacitors. Link here.
