Ceramic Capacitors and Reliable Capacitors Manufacturer

The ceramic capacitor is available in many versions including leaded disc ceramic capacitors, surface mount multilayer ceramic capacitors, MLCCs etc.

 

Ceramic capacitors are one of the most widely used forms of capacitor used in electronics equipment these days.

 

Ceramic capacitors have also been used for many years, being found in valve or tube circuits dating from the 1930s.

 

Today ceramic capacitors area available in a variety of formats ranging from leaded components to surface mount technology, SMT varieties. As leaded versions disc ceramic capacitors are widely available, and as SMT devices, multilayer ceramic capacitors or MLCCs are available in all the common formats. As such these ceramic capacitors are used in virtually every type of electronics equipment.

 

The actual performance of the ceramic capacitors is highly dependent upon the dielectric used. Using modern dielectrics, very high values are available, but it is also necessary to check parameters such as the temperature coefficient and tolerance. Different levels of performance are often governed by the dielectric used, and therefore it is necessary to choose the type of dielectric in the ceramic capacitor.

 

Ceramic capacitors range in value from figures as low as a few Pico farads to around 0.1 microfarads. In view of the wide range and suitability for RF applications they are used for coupling and decoupling applications in particular. Here they are by far the most commonly used type being cheap and reliable and the loss factor is particularly low although this is dependent on the exact dielectric in use.

 

Basics of Ceramic Capacitor

Ceramic capacitors are the workhorses of the capacitor world these days. Ceramic capacitors are used in millions as a result of a combination of their cost and performance. There is a wide variety of dielectrics that can be used as described below, but as the name of the ceramic capacitor suggests, they are all ceramic in nature.

 

In order to ensure that sufficient levels of capacitance can be obtained within a single capacitor package, ceramic capacitors, like types of capacitor have multiple layers. This increases the level of capacitance to enable the required values of capacitance to be achieved.

 

Ceramic capacitors are available now in three main types although other styles are available:

 

  • Leaded disc ceramic capacitors for through hole mounting which are resin coated
  • Surface mount multilayer ceramic capacitors
  • Specialist microwave bare leadless disc ceramic capacitors that are designed to sit in a slot in the PCB and are soldered in place

 

Although it is possible to obtain other types of ceramic capacitor, these are the main types that can be found today. Of these the surface mount variety is used in the greatest quantities by far because of the manufacturing methods used these days for electronic equipment.

 

Capacitors Supplying Expert

Zonkas Electronic specializes in manufacture of Ceramic Capacitors which are applied to various industries. The ceramic capacitor is a capacitor constructed of alternating layers of metal and ceramic, with the ceramic material acting as the dielectric. The company has well-equipped manufacturing facilities that are operated by a team of experts. The strong team comprises of engineers, technicians, marketing professionals, quality analysts and customer services.

 

If you want to learn more information about ceramic capacitor manufacturer and capacitors, try to check out Zonkas’s website: www.zonkas-cap.com to obtain the details you need.

 

 

Article Source: http://www.radio-electronics.com/info/data/capacitor/ceramic-capacitor.php

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UMTS Antenna and GSM Antenna Supplying Expert – Evercom Communication

Established in 1993, Evercom Communication specializes in manufacturing GSM antenna and UMTS antenna. Furthermore, kinds of other antennas also can be found on their website.

 

The comprehensive ranges of GSM antenna, including roof antenna, NMO antenna, magnetic antenna, mini magnetic antenna, portable antenna, trucker antenna, marine antenna, on-glass antenna, patch antenna, window clip antenna, wall mount antenna, yagi antenna and base station antenna. If you have any interest, you can try to check out Evercom’s product page.

 

Let’s get to the point. Evercom’s dynamic research and development team offers unrivaled expertise that enables Evercom to provide wide frequency range of standard, customized and tailor-made UMTS antennas to meet all kinds of customers’ requirements. They credit their success to the continuous efforts into the innovation and dedicated customer service. In addition, Evercom maintains a speedy and flexible process of design, production, packaging and delivery in order to meet the diverse demands.

 

Would you want to learn more about GSM antenna and UMTS antenna, welcome to visit Evercom’s website: www.evercomtech.com and feel free to send inquiries to them.

 

 

Q&A:

What is UMTS?

UMTS is one of the Third Generation (3G) mobile systems being developed within the ITU’s IMT-2000 framework. It is a realization of a new generation of broadband multi-media mobile telecommunications technology.

 

– From http://www.umtsworld.com/umts/faq.htm

 

 

Evercom Communication Technology Co., Ltd.

No.108, Jiesin St., Taoyuan Dist., Taoyuan City 330, Taiwan (R.O.C.)

TEL: 886-3-376-5678

FAX: 886-3-376-5319

E-mail: service@evercomtech.com / gtevercomtech@gmail.com

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Technologies of Proximity Card Reader

Passive Proximity Readers

 

Nearly all building access cards based on proximity are passive. There are roughly 125 million cards used for accessing secured buildings today.

 

Passive technology implies there is no battery or power source required in the card. The proximity reader constantly transmits a low level fixed RF signal that transmits energy to the card. When the card is held at a certain distance from the reader, the RF signal is absorbed by a small coil inside the card and powers the card’s chip which contains a unique identification code. Once powered, the card transmits the code to the reader.

 

The advantages of proximity over other technologies are numerous: no moving parts, no mechanical wear, no slots, no read heads to maintain. The reader can be concealed inside walls or special enclosures and, even when the reader is surface mounted, it has no openings to jam or tamper. The card is the most secure and practically impossible to duplicate. Cards can usually be read through a purse or wallet and through most other nonmetallic materials. Card and reader orientation is not critical.

 

Reading ranges depend primarily on the reader. The larger the reading range, the larger the reader’s concealed antenna and hence, the size of the reader. There is a great variety of proximity readers designed for different environments including vandal-resistant mullion mount, smaller decor style and integrated keypad/reader units.

 

Active Proximity Readers

 

Active proximity technology implies there is a battery within the card. Since the card has power the range is greatly expanded (3-15 feet vs. 1-5 inches). The RF signal is low level (<1mw) but the frequency used is much higher. Applications tend to be uniquely applied, although recently the application in computer access control is more prevalent.

 

Orientation of the card and reader become important. Since the RF frequency is much higher several other effects may be noticed such as exact distance due to the fact that the signal bounces off of other object.

 

Active technology is useful where a hands-free (as opposed to contactless) data exchange is required. Since the range is much longer, it is generally not very practical for door access (except gated parking lots) since walking past the door may unlock the room. The typical application is to detect the presence of a person at a computer and allow access without intervention. Equally important is to automatically lock the computer when a person steps away.

 

Read range is adjustable between 3 to 15 feet.

 

Active cards are generally thicker (1/5 inch) as a result of the replaceable battery requirement

 

Presence Detectors

 

Sonar technology is a relatively new entrant as a tool for security with PCs.

 

In computer security there are two primary components to consider:

 

  1. Unlocking the ‘locked’ workstation, and
  2. Locking the workstation after the logon user leaves the station.

 

The first component generally gets the most attention and array of solutions while the second is generally handled by a time-out screen saver or company mandated policy. Both solutions for ‘2’ above are fraught with exposure issues.

 

The use of sonar technology is a means for detecting the presence or absence of an individual, and performing a specific operation when there is a change. It is important to understand there is no real identification of the user performed with this technology.

 

When a user steps away from an authorized session, the sonar device can detect this occurrence and send the appropriate keystrokes to secure the workstation (log off or lock). This improves solutions associated with policy since the device never forgets to lock. It is also a great improvement over a time-out in that this occurs immediately as opposed to a parameter set by the minute(s).

 

Likewise when the user steps up to a locked workstation, the appropriate keystrokes can be set to call up the logon dialog.

 

This technology can be a great aid for other forms of authentication such as biometrics.

 

Pongee Industries Co., Ltd. is the company of specializing in proximity reader, writer, and programmer. They also provide kinds of high quality access controllers for customers to select. Need more information, welcome to visit the Pongee’s website and feel free to contact with them.

 

 

Article Source: https://www.rfideas.com/support/learning-center/proximity-reader-technologies

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Taiwan UAV Manufacturing Specialist – Carbon-Based Technology Inc.

Proved Core Values of Unmanned Systems in Fields of Anti-Disaster and Geographic Spatial Application.

 

UAVs Companies?

 

Carbon-Based Technology Inc. was established in March 2007 and devoted in complete system design, integration, manufacturing, and global marketing of Unmanned Aircraft System.

 

Carbon-Based Technology not only can offer high reliability Unmanned System as a platform for “Intelligence Gathering”, but also can offer total solutions for various aspects. Through this Hi-tech and Hi-reliability UAS platform which is 100% researched & developed in-house, it can integrate with techniques of data processing and analyzing for relative study fields such as GIS and Remote Sensing, Team Carbon-based can offer clients with totally intact and useful intelligence on the ground as well as in the air. Especially for fields of anti-disaster and geographic spatial application, they have assisted clients from various professions to acquire priceless feedbacks. This also has proved core values of Unmanned Systems of Carbon-Based Technology!

 

Below, I am going to introduce one of products in Carbon-Based UAVs to you – Real Time Surveillance.
Avian-S
Real-time Surveillance

Real-time Surveillance

Avian-S Real-time Surveillance

Avian-S unmanned aerial systems featuring the advantages of long endurance, hi-stability, turn-key operation, and payloads that are plug-and-play modular designed. Any individual with less or even no aviation experience can easily accomplish any mission.

 

Avian is an Unmanned Aircraft System (UAS) featuring compact design, multi-purpose, and modularized payloads which are interchangeable on-site according to the mission requirements.

 

If you are interested in learning further details about real time surveillance, welcome to check out product pages of Carbon-Based. And feel free to send inquiry or contact with them for more information.

 

Watch Video Below for More Details!

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Carbon-Based Technology Inc.

Carbon-Based Technology Inc.

3F, No.30, Keya Road, Daya District, Taichung City, 42881 Taiwan

Tel: +886-4-2565-8558

Fax: +866-4-2565-8559

E-mail: info@uaver.com

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PTC Thermistors: Positive Temperature Coefficient

The positive temperature coefficient, PTC thermistor has two types: silistor & switching PTC have very different characteristics.

 

As the name indicates a positive temperature coefficient, PTC thermistor has a response in which the resistance rises with increasing temperature.

 

There are two types of PTC thermistor which have very different characteristics, one showing a linear increase, whilst the other shows a sudden change in resistance.

 

PTC thermistor outline

 

PTC thermistors can be divided into two types according to their structure and the materials used. The two types of PTC thermistor have very different characteristics:

 

  • Switching PTC thermistor:

This form of PTC thermistor is used in heaters, sensors and specialized versions are also used as resettable fuses. Switching type NTC thermistors have a highly non-linear curve. The resistance at first falls slightly with increasing temperature, and then at a critical temperature the resistance increases dramatically, thereby acting virtually as a switch. This makes it ideal in many protection devices.

  • Silistor:

The silistor PTC thermistor uses a semiconductor as its base material and it is characterized by a linear characteristic and as a result, the silistor is used in temperature sensors. The silistor PTC thermistor is generally manufactured from doped silicon, the level of doping determining the exact characteristics.

 

Switching PTC thermistor basics

 

As the switching PTC thermistor is very widely used form, it warrants further explanation as it has an unusual characteristic.

 

Switching PTC thermistors are typically fabricated from polycrystalline materials including barium carbonate or titanium oxide with added materials including tantalum, silica, or manganese, etc.

 

The materials are mixed and ground to fine powders and finally compressed into the required shapes before being sintered. Contacts are then added and the thermistor is encapsulated.

 

The characteristic of the switching PTC thermistor shows that the device has a highly non-linear characteristic. As the temperature increases, the resistance first decreases, then rising slightly before it reaches a critical temperature, TC. At the critical temperature the resistance increases sharply for any increase in temperature, before finally leveling off and falling slightly.

 

A similar type of device is known as a Polymer PTC. These devices consist of a plastic element into which carbon grains are embedded. When cool, the carbon is able to conduct electricity, but as the temperature increase the carbon grains move further away as a result of expansion and conduction falls rapidly. In this way the device acts like a switch in the same way as the more traditional PTC thermistors.

 

PTC thermistor operational modes

 

There are two main ways in which switching PTC thermistors are generally used.

 

  • Self-heating mode:

When used in the self-heating mode, current is passed through the thermistor, often in series with the item being controlled. As it heats up as a result of the current, it reaches a point where the critical temperature is reached and the resistance increases significantly. In this way it operates in a self-heating mode and can be used as a safety cut-out or regulator.

 

  • Sensor mode:

In this mode, a minimum amount of current is passed through the device and PTC thermistor senses the surrounding temperature. Keeping the current to a minimum ensures the self-heating effect is negligible and only the surrounding temperature affects the device. As the surroundings heat the device it may reach its critical temperature at which point the resistance will significantly increase.

 

Switching PTC thermistor applications

 

Switching thermistors are a very useful form of electronic component. It can perform functions with a single component that would require far more complex circuitry should any other technique be used.

 

  • In-rush protection:

Some electrical items like motors and transformers have a large surge of current at switch on. This gives rise to very high peaks of current which can cause spikes on the power line, or cause damage in some instances. PTC thermistors can be used to reduce the level of the inrush current and thereby prevent the spikes or damage occurring.

 

  • Overcurrent protection:

In this application, the PTC thermistor is placed in series with the load and uses the self-heating effect. The current taken under normal conditions should enable the thermistor to operate in its flat resistance curve area. However if an over-current condition arises, then the thermistor will carry more current and the temperature will rise more causing it to rise beyond the critical temperature when the resistance will rise significantly causing the current to drop.

 

PTC thermistor circuit symbol

 

It is sometimes necessary to indicate the type of thermistor being used on a circuit diagram. Accordingly the IEC have a special PTC thermistor circuit symbol that can be used.

 

As seen the circuit symbol utilizes the characters +t° to give an indication of the positive temperature coefficient.

 

Positive temperature coefficient, PTC thermistors are used in many electronic circuits and for a variety of functions. It is essential to check that the correct type is selected for any given circuit to ensure that its characteristic meets the requirements.

 

Zonkas is the experienced and reliable manufacturer of specializing in capacitor, inductor, and transformer. If you are still interested in PTC thermistors, welcome to visit the website of Zonkas.

 

 

Article Source: https://www.electronics-notes.com/articles/electronic_components/resistors/thermistor-ptc-positive-temperature-coefficient.php

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Scope Of RFID Systems In Security Measures

What is RFID?

 

Radio-frequency identification device is a technology that retrieves the status and presence of a thing to which it is attached to remotely. These devices will track the objects automatically and sends the embedded information to the processors.

 

Typical components of RFID system

 

An RFID system contains an RFID tag, RFID reader, RFID antenna, and RFID package.

 

RFID tag is attached to the item that needs to be tracked and identified.

 

RFID antenna will detect the RFID tag when it comes in range.

 

RFID reader reads the RFID tags and authenticates its presence.

 

RFID package contains the server and software and transmits the information to all other applications.

 

Application of RFID systems

 

To simplify, RFID systems do the same function as of a BAR-CODES, but when it comes to applications they are widely spread as RFID systems doesn’t need to maintain contact with the scanners as in case of BAR-CODE. High Frequency RFID systems doesn’t necessarily to be appear in the line of sight, especially such are applied for livestock tracking, Missile tracking, automobile tracking through assembly lines and most importantly in case of vehicle tracking.

 

Security potential

 

Increasing security measures through CCTV cameras has already outdated, the latest technology implies to the usage of RFID readers wherever the security is needed along with authentication.

 

They can be installed in a library, home, and elsewhere domestically to secure the important files, books, and expensive things, so that even when they are found missing they can be easily detected with the help of local servers that are giving location information.

 

They can also be placed in a vehicle, thanks to their non-contact readable characteristic feature as the vehicles can be tracked along the route as they can use the location provided by the nearest GSM signal boosting towers and thus one can keep notice of their vehicles.

 

The size of the smallest developed RFID is 0.05mm × 0.05mm size and the average size would be around 3mm x 3mm. As we go cheaper the size will be increased consistently. Their dimensions make them invisible to see which a plus point in terms of security measures is.

 

Evercom Communication Technology Co., Ltd. is the professional company of specializing in kinds of antennas. If you are interested in learning more details about RFID antenna and other antennas, welcome to visit Evercom’s website to see what antennas they can offer you.

 

 

Article Source: http://EzineArticles.com/8431202

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What Is a Proximity Reader?

If you are in the process of updating your home’s or business’s security system or if you never had such a system and you are planning to invest in one, there are probably a lot of industry terms you don’t understand very well. That is why, in this article, we are going to talk about two important parts of any security access system, the proximity card and the proximity reader.

 

Proximity cards, also referred to as prox cards, are different than the magnetic stripe cards, because they do not need to be inserted into the reader device to grant access in the secured area. We say “grant access” because the majority of proximity cards and proximity readers are used as a part of home or business security system. Other uses include library cards, contactless payment systems or in public transit fare. Proximity cards are practical due to the fact that they can easily be read through a wallet or a purse.

 

There are two main types of proximity cards: passive and active. Passive prox cards have a limited range and are widely used to grant access in office buildings. Active cards, also called vicinity cards, have a greater range (150 meters), due to the fact that they use and internal lithium battery. They can be used to easily access courtyards from inside of a vehicle or from automated toll collection.

 

Now, in case you were wondering “What is a Proximity Reader?” they are devices that can store details about the identity of the cards holders, granting them access to otherwise restricted areas. This system is similar to the “chip and PIN” bank cards, with the difference that the proximity reader grants access using radio frequencies and does not need actual insertion of the card. Also, they offer more security to their holders, due to the fact that they are harder to copy. Another great advantage of these readers is the fact that they are quite sturdy and do not need any maintenance.

 

Another term you might encounter when browsing for this type of access system in “Contactless Smart Card”, which is basically the same thing, with the difference that they use advanced methods of data encryption and authentication, meaning that they offer a higher level of security. Besides this general information, there are various technologies that are used in the manufacture of proximity cards and readers.

 

If you are planning to invest in such a system, you must know that the prices are very different from one product to another. For example, the price for a single card ranges from $2 to $200, while for the proximity reader you can pay from $100 to $400.

 

Before making any purchase, we advise you to ask the advice of an experienced security technician, just to make sure that you choose the right system for your needs. The good news is that the majority of shops, even online ones, have an assistant which can help you make the right decision.

 

Pongee Industries Co., Ltd. is the manufacturer of proximity reader. If you are looking for the best proximity reader, don’t miss Pongee’s website, we can offer clients kinds of high quality products. Contact with Pongee to obtain further product information!

 

 

Article Source: http://EzineArticles.com/8665232

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Difference between Manual Thermostats and Electrical Thermostats

A thermostat is a temperature–sensitive device that turns HVAC systems on and off when the temperature of an environment reaches a preset level. Essentially, it turns on the air conditioning when it gets too warm, or the heating when it gets too chilly. Thermostats control the workings of comfort systems by directing energy to the appropriate system when needed. When selecting a thermostat, property owners can either go for simple manual thermostats or sophisticated electronic thermostats that provide improved functionality and highly efficient operations. Thanks to the easy to understand packaging and universal compatibility, choosing a thermostat is easy.

 

Systems that Use a Thermostat

Single–stage heating systems have one electrical or gas heating device, which may consist of a heater or an AC device as well. Most units that use natural gas provide single–stage heating. Usually, a single–stage thermostat should have room for three wires if the system handles heating only. However, if the system handles heating and cooling, the thermostat will have to accommodate five wires or less.

 

Multi–stage systems have a standard electrical or gas heating device as well as an emergency and/or auxiliary heating device. The emergency or auxiliary heating kicks in when temperatures drop faster than the standard heater can handle, or if the standard heater fails. Line voltage systems, on the other hand, use direct current. Homeowners should choose line voltage thermostats that can handle additional conducted power.

 

Difference between Manual and Programmable Electrical Thermostats

 

Electromechanical or annual thermostats are the traditional mercury units that have internal coils to contract and expand in response to changes in temperature. They are becoming obsolete because of two main reasons:

 

  • Products containing mercury are banned or restricted in most states
  • Programmable thermostats are more accurate and sensitive to temperature changes

 

However, manual thermostats are still popular due to their ease of use, low cost, and the familiarity of their controls.

 

Digital manual thermostats use an electronic sensor to register temperature changes in an environment and then compare those changes to the preset settings. If there is a difference, the thermostat sends a warning to the cooling or heating system that immediate action is required. However, users still have to physically adjust the settings to their preferred level.

 

Programmable electrical thermostats are an upgrade from the manual thermostats. In addition to saving energy costs, they allow homeowners to program their preferred temperature settings into the unit’s memory, along with the time of day they would like the changes to occur.

 

For most homes, a pre–programmed electrical thermostat does not need any adjustment. Homeowners simply need to install it and they are ready. When determining the right thermostat, homeowners should consider the flexibility and functionality they need from day to day.

 

Alpha Brass electrical thermostats are manufactured and calibrated with precision to provide accurate temperature points. These thermostats are snap-acting and the temperature is controlled by signal interrupting the gas flow to the burner. If you need further details about our electrical thermostats, welcome to browse our website or contact with Alpha Brass directly!

 

 

Article Source: http://cphac.com/blog/difference-manual-thermostats-electrical-thermostats

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SMPS: Basics & Working of Switched Mode Power Supply

Switching mode power supply (SMPS) is used in a range of applications as an efficient and effective source of power. This is in major part to their efficiency. For anybody still working on a desktop, look for the fan output in the central processing units (CPU). That’s where the SMPS is. SMPS offers advantages in terms of size, weight, cost, efficiency and overall performance. These have become an accepted part of electronic gadgets. Basically it is a device in which energy conversion and regulation is provided by power semiconductors that are continuously switching “on” and “off” with high frequency.

 

The different kinds

  • C. to D.C. Converter
  • Forward Converter:
  • Flyback Converter:
  • Self-Oscillating Flyback Converter
  • DC-DC converter

 

The primary power received from AC main is rectified and filtered as high voltage DC. It is then switched at a huge rate of speed and fed to the primary side of the step-down transformer. The step-down transformer is only a fraction of the size of a comparable 50 Hz unit thus relieving the size and weight problems. We have the filtered and rectified output at the secondary side of the transformer. It is now sent to the output of the power supply. A sample of this output is sent back to the switch to control the output voltage.

 

Forward converter

 

In a forward converter the choke carries the current when the transistor is conducting as well as when it’s not. The diode carries the current during the OFF period of the transistor. Therefore, energy flows into the load during both the periods. The choke stores energy during the ON period and also passes some energy into the output load.

 

Flyback converter

 

In a flyback converter, the magnetic field of the inductor stores energy during the ON period of the switch. The energy is emptied into the output voltage circuit when the switch is in the open state. The duty cycle determines the output voltage.

 

Self-Oscillating Flyback Converter

 

This is the most simple and basic converter based on the flyback principle. During the conduction time of the switching transistor, the current through the transformer primary starts ramping up linearly with the slope equal to Vin/Lp. The voltage induced in the secondary winding and the feedback winding make the fast recovery rectifier reverse biased and hold the conducting transistor ON. When the primary current reaches a peak value Ip, where the core begins to saturate, the current tends to rise very sharply. This sharp rise in current cannot be supported by the fixed base drive provided by the feedback winding. As a result, the switching begins to come out of saturation.

 

Basic working concept of a SMPS

 

A switching regulator does the regulation in the SMPS. A series switching element turns the current supply to a smoothing capacitor on and off. The voltage on the capacitor controls the time the series element is turned. The continuous switching of the capacitor maintains the voltage at the required level.

 

Design basics

 

AC power first passes through fuses and a line filter. Then it is rectified by a full-wave bridge rectifier. The rectified voltage is next applied to the power factor correction (PFC) pre-regulator followed by the downstream DC-DC converter(s). Most computers and small appliances use International Electrotechnical Commission (IEC) style input connector. As for output connectors and pinouts, except for some industries, such as PC and compact PCI, in general they are not standardized and are left up to the manufacturer.

 

Why SMPS

 

Like every electronic gadget, switching mode power supplies also involve some active and some passive components. And like every of those gadgets, it has its own advantages and disadvantages.

 

Let’s start with why you should go for a SMPS

 

  • The switching action means the series regulator element is either on or off. Very high efficiency levels are achieved as very little energy us dissipated as heat.
  • As a result of the high efficiency and low levels of heat dissipation, the switch mode power supplies can be compact.
  • Switch mode power supply technology also provide high efficiency voltage conversions in voltage step up or “Boost” applications and step down or “Buck” applications.

 

Then there’s the bad set

 

  • The transient spikes due to the switching action can migrate into other areas of the circuits if not properly filtered. These can cause electromagnetic or RF interference affecting other nearby items of electronic equipment, particularly if they receive radio signals.
  • To ensure that a SMPS performs as per the required specification can be a bit difficult. The ripple and interference levels are particularly tricky.
  • The costs of a switch mode power supply is calculates before designing or using one. Additional filtering further adds to the cost.

 

What would the future hold?

 

In the future, we could have more efficient SMPS aimed at a better converter doing the most effective conversion process. The focus areas for designers in making SMPS efficient would be:

 

  • Higher output power
  • Achieving higher current output and low voltage
  • Increasing power density
  • Using switching device like Schottky diode

 

Hon-Kwang Electric specialized in manufacturing switch mode power supply and related products. We provide series of switching power supplies to meet different demands of you. If you are interested in learning more details about switching mode power supply, please feel free to contact with Hon-Kwang.

 

Article Source: http://electronicsforu.com/resources/learn-electronics/smps-basics-switched-mode-power-supply

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Choosing the Best Option for Overcurrent Circuit Protection

When it comes to overcurrent protection of electronic equipment, fuses have long been the standard solution. They come in a wide variety of ratings and mounting styles to fit virtually any application. When they open, they completely stop the flow of electricity, which may be the desired reaction; the equipment or circuit is rendered inoperable, which draws the user’s attention to what may have caused the overload condition so that corrective action can be taken.

 

Nevertheless, there are circumstances and circuits where auto-recovery from a temporary overload without user intervention is desirable. Positive temperature coefficient (PTC) thermistors – also called polymeric positive temperature coefficient devices (PPTCs) or resettable fuses – are an excellent way of achieving this type of protection.

 

Ceramic PTCs are also widely available through possess different operating characteristics including greater internal resistance, higher ambient heat tolerance, and higher voltage ratings. As they are typically used within high ambient heat areas including heating equipment applications not common to many electronics requirements, they were not factored within the scope of this article.

 

How a PTC works

 

A PTC resettable fuse consists of a piece of polymer material loaded with conductive particles (usually carbon black). At room temperature the polymer is in a semi-crystalline state and the conductive particles touch each other, forming multiple conductive paths and providing low resistance (generally about twice that of a fuse of the same rating).

 

When current passes through the PTC it dissipates power (P = I2R) and its temperature increases. As long as the current is less than its rated Hold Current, IHOLD, the PTC resettable fuse will remain in a low-resistance state and the circuit will operate normally. When the current exceeds the rated Trip Current, ITRIP, the PTC heats up suddenly. The polymer changes to an amorphous state and expands, breaking the connections between the conductive particles. This causes the resistance to increase rapidly by several orders of magnitude and reduces the current to a low (leakage) value just sufficient to keep the PTC in the high-resistance state – generally from around tens of milliamps to several hundred milliamps at rated voltage (Vmax). When the power is shut off the device cools down and returns to its low-resistance state.

 

Like a fuse, a PTC is rated for the maximum short circuit current (IMAX) it can interrupt at rated voltage. IMAX for a typical PTC is 40A, and may reach 100A. Interrupting ratings for fuses of the sizes that may be used in the sorts of applications we are considering here can range from 35 to 10000 amperes at rated voltage.

 

The voltage rating for a PTC is limited. PTC resettable fuses for general use are not rated above 60V operating voltage (there are PTCs for telecom application with 250V and 600V interrupting voltage, but their operating voltage is still 60V); surface-mount and small cartridge fuses are available with ratings from 32V to 250V or more.

 

The operating current rating for PTCs ranges up to about 9A, while the maximum level for fuses of the types considered here can exceed 20A, with some available to 60A.

 

The useful upper temperature limit for a PTC is generally 85°C, while the maximum operating temperature for thin-film surface mount fuses is 90°C, and for small cartridge fuses is 125°C. Both PTCs and fuses require derating for temperatures above 20°C, although PTCs are more sensitive to temperature (Fig.2). When designing in any overcurrent protective device, be sure to consider factors that may affect its operating temperature, including the effect on heat removal of leads/traces, any air flow, and proximity to heat sources. The speed of response for a PTC is similar to that of a time delay fuse.

 

Common PTC applications

 

Much of the design work for personal computers and peripheral devices is strongly influenced by the Microsoft and Intel System Design Guide which states that “Using a fuse that must be replaced each time an overcurrent condition occurs is unacceptable.” And the SCSI (Small Computer Systems Interface) Standard for this large market includes a statement that “… a positive temperature coefficient device must be used instead of a fuse, to limit the maximum amount of current sourced.”

 

PTC resettable fuses are used to provide secondary overcurrent protection for telephone central office equipment and customer premises equipment, alarm systems, set top boxes, voice over IP (VOIP) equipment and subscriber line interface circuits (SLICs). They provide primary protection for battery packs, battery chargers, automotive door locks, USB ports, loudspeakers and power over Ethernet.

 

SCSI Plug and Play applications that benefit from PTCs include both the mother-board and the many peripherals that can be frequently connected to and disconnected from the computer ports. The mouse, keyboard, printer, modem and monitor ports represent opportunities for misconnections and connections of faulty units or damaged cable. The ability to reset after correction of the fault is particularly attractive.

 

A PTC resettable fuse can protect disk drives from the potentially damaging overcurrent resulting from excessive current from a power supply malfunction.

 

PTC resettable fuses can protect power supplies against overloading; individual PTCs can be placed in the output circuits to protect each load where there are multiple loads or circuits.

 

Motor overcurrent can produce excessive heat that may damage the winding insulation and for small motors may even cause a failure of the very small diameter wire windings. The PTC will generally not trip under normal motor start up currents, but will act to prevent a sustained overload from causing damage.

 

Transformers can be damaged by overcurrent caused by circuit faults, and the current limiting function of a PTC can provide protection. The PTC is located on the load side of the transformer.

 

Fuse or PTC?

 

The following procedure will help in selecting and applying the correct component. Help is also available from device suppliers. For unbiased advice it is wise to look for a company that offers both fuse and PTC technology.

 

  1. Define the circuit operating parameters. Consider the following: normal operating; current in ampere; normal operating voltage in volts; maximum interrupt current; ambient temperature/rerating; typical overload current; required opening time at specific overload; transient pulses expected; resettable or one-time; agency approvals; mounting type/form factor; typical resistance (in circuit).

 

  1. Select a prospective circuit protection component.

 

  1. Determine the opening time at fault. Consult the Time-Current (T-C) Curve to determine if the selected part will operate within the constraints of the application.

 

  1. Verify ambient operating parameters. Ensure that the application voltage is less than or equal to the device’s rated voltage and that the operating temperature limits are within those specified by the device

 

  1. Verify the device’s dimensions. Compare the maximum dimensions of the device to the space available in the application.

 

  1. Test the selected product. Independently test and evaluate suitability and performance in the actual application.

 

Zonkas is the professional manufacturer of capacitor, inductor and transformer. Our main products including: various inductors, transformers, Safety Capacitor (Y1, Y2, X1, X2), Ceramic Capacitor, Film Capacitor and Electrolytic Capacitor. If you need more information about PTC resettable fuses or other capacitors, welcome to visit our website or contact with Zonkas directly!

 

 

Article Source: http://www.engineerlive.com/content/21341

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