10/9/2016

Dear Friends and Fellow Americans,

I am not prone to writing public letters. However the current state of affairs in our country has moved me to write. I will be direct and to the point.

Problem

In the Bible, at 2 Chronicles 7:13-14, God says, “¹³When I shut up the heavens so that there is no rain, or command the locust to devour the land, or send pestilence among My people, ¹⁴if My people who are called by My name humble themselves, and pray and seek My face and turn from their wicked ways, then I will hear from heaven and will forgive their sin and heal their land.”

I believe that we as a country have completely lost our moral compass. This belief is substantiated by our current political predicament where we have two very clearly and very corrupt and morally bankrupt candidates as the front runners for President of the United States. As a country we have not figured out how to elect a decent person for the most important leadership position in the world.

I am a big believer in the importance of historical lessons. Consider the Roman Empire. Rome was arguably the vastest empire this world has ever known. But it was when Rome became morally bankrupt that she diminished and was ultimately conquered.

Today, the United States, after having experienced the blessings of the Lord for two centuries, is experiencing the same moral decline. But the Lord, in His Word, has graciously and mercifully provided a path back to His blessings as described in the above quoted verse of 2 Chronicles 7:14.

Solution

Our actions need to be to,

1. Humble ourselves,
2. Pray and seek God’s face,
3. Turn from our wicked ways.

Then God says that He will hear us from heaven, forgive our sin, and heal our land.

Application

Humble ourselves – Acknowledge that we are God’s creation, needing the salvation of the Lord Jesus Christ from our sin, and made to be His servants in the work of glorifying Him and loving and respecting others in His Name.

Pray and seek God’s face – Get a Bible, read it as it is God speaking to you about His plan for you, and pray to the Lord that He will guide and direct your steps for His Glory.

Turn from our wicked ways – Know what the Bible says about right from wrong. Do right and turn away wrong while loving God and your fellow man.

Immediate Application — November Election

In less than a month, we will be casting lots, or voting, for candidates for office including President of the United States.

In Proverbs 1:14, the wicked says, “Thrown in your lot with us. We shall all have one purse.”  But God says in the next verse, “My son, do not walk in the way with them. Keep your feet from their path, for their feet run to evil and they hasten to shed blood.”

No doubt, you have by now heard in the news media that we must choose the lesser of two evils regarding Hillary Clinton and Donald Trump. But the Bible says in Romans 3:9, “And why not say…”Let us do evil that good may come”?  Their condemnation is just”

In light of the apparent quandary in choice for President of the United States, I would like to highlight two alternative candidates that I believe would be solid, conservative, and pro-life.  These candidates may not be on the ballot in all fifty states and territories, but you can always write them in.

Dan Castle – Constitution Party   http://castle2016.com/platform/

Evan McMullin – Independent     https://www.evanmcmullin.com/

While these candidates may not have the charisma of the leading candidates, we have to ask ourselves, “What do we want in a president?”  Remember that when God chose David to be king, David was the least of his brothers. But David was a man after God’s own heart.

I urge you to consider your vote. Do not cast your lot in with the wicked. Do not settle for the lesser of two evils. Instead, vote for a person who you know would honor the office of President of the United States. Trust in the Lord to resolve all of the attendant issues such as Supreme Court Judge of the United States.

Yes it would seem that it would take a miracle at this point for anybody else than Hillary Clinton or Donald Trump to be elected as President.  But then – a miracle is a small thing for the Creator of the universe.

To God Alone Be Glory.

Robert W. Stowe
Marion, IA

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Source Characterization for Power Supply Specification

Last month we introduced this series with the article titled, “Specifying Electronic Power Supplies from a System Point of View: Introduction”.  In this article we explore importance of load characteristics when specifying a power supply.

The figure 1 shows a power supply in simplified form, connected to a generalized load. The feedback and control circuit samples the output voltage, compares it to a reference (not shown), and adjusts the source voltage to maintain the load voltage constant. This process is not perfect, and the power supply specifications describe the deviation from perfection. The deviation from perfection must be within the requirements demanded by the load for the load to operate satisfactorily.

Figure 1: Simplified representation of power supply and load.

The Importance of Knowing the Load Characteristics

The load is the reason for being for a power supply and imposes a major portion of the performance requirements for the power supply. The power supply is never a perfect black box and it is extremely important to treat it as a vital and integral part of your system. It must meet the demands placed upon it by the load in several key performance measures. The most common measures are discussed below:

Static Requirements

Typically, the load requires one of the following parameters to be provided and controlled to within a certain tolerance band: voltage, current, or power. For example, a subassembly might be designed to operate with a controlled input voltage of 5 volts. When excited with a controlled input voltage of 5 volts, the subassembly responds by drawing up to 10 amperes, and consuming up to 50 watts of power. This example illustrates that the power supply must maintain the output voltage at 5 volts and be able to provide up to 10 amperes of current since up to 10 amperes is what the load draws when excited by 5 volts. In this case, power is an alternate way of expressing compliance since power is the same as voltage times current.

Some loads may require different controlled parameters at different times. Such an example is a battery charger which might require constant current for battery charge mode and constant voltage for battery maintenance mode.

Loads will require the controlled parameter to be within a certain tolerance band for proper operation. The power supply must maintain the controlled parameter within the tolerance band.

These parameters may be expressed in terms of average, RMS, or a peak value with a duration qualifier.

Dynamic Requirements

Loads also exhibit dynamic characteristics which change over time.

Time Transients

Many types of loads frequently change their effective impedance. An example might be a computer printer which exhibits rapid step changes in effective impedance. For such a device to function properly, the power supply must be able to rapidly source spurts of output current while maintaining the output voltage within a specified band. This means that the power supply must have enough output capacitance and high enough control loop bandwidth to maintain the output voltage within the prescribed limits. Loads which have this type of behavior must have power supplies specified to limit the droop on the leading edge of the pulse, and recover to within a certain band of the steady state output in a prescribed time interval.

Dependence on Voltage

Non-linear loads change impedance as voltage is increased. One example is a typical solid state circuit which might draw very little current at low voltages, and then begins to draw current with a very rapid and nonlinear increase as voltage is increased.

A configuration which causes greater problems is cascading a power supply with a second power supply of a switching converter design. A switching converter has a nonlinear negative resistance characteristic. At very low input voltages, below the turn-on threshold, the current may be miniscule. When the input voltage is increased to the turn-on threshold, the input current suddenly draws very high current. As the input voltage is increased, the input current decreases, following a constant power characteristic. If care is not taken in the first power supply design and cable length, the load (the switching converter) will cycle on and off because of the voltage drop in the cable length and/or the output impedance of the power supply.

Dependence on Frequency

Loads can create a frequency dependence which is not obvious to the untrained user. This frequency dependence is of at least two forms:

1. Resonant behavior can occur due to inductance and capacitance in both the power supply and the load. Power supplies can resonate with load capacitance or inductance if the power supply is not designed well for the load. This resonance will usually take place at frequencies determined by the reactive elements in the system. This effect is usually undesirable unless the system is designed to be resonant.
2. The power supply control loop behavior can be adversely influenced due to load capacitance and inductance. The presence of substantial capacitance or inductance can move the control loop poles and zeros, substantially changing the transient response and ripple rejection capability of the power supply by decreasing or possible increasing the bandwidth of the power supply.

Dependence on Temperature

Loads must operate in their intended environment. More often than not, the power supplies for these loads must operate in the same environment. These environments may be benign, such as a test laboratory, or severe, as in down-hole oil and natural gas exploration. The power supply must be able to work in the environment of the load, or the power supply environment must be separated from the load to allow satisfactory operation.

Upcoming Topics

This series of articles about specifying power supplies from a system perspective will cover in more detail various aspects of system level concerns. Some of these aspects to be covered are:

• Source Characterization
• Efficiency
• Thermal Environment
• Packaging

Watch for the upcoming articles on “Specifying Electronic Power Supplies from a System Point of View “.

If you need assistance with power electronics design, call or email us today for help with your requirements. You can also go to our power electronics consultant website for more information about our services for business clients. Thank you for reading this tutorial article entitled “Specifying Electronic Power Supplies from a System Point of View: Load Characterization”

The post Specifying Power Supplies for a System: Load Characterization appeared first on POWER ELECTRONICS CONSULTANT.

Power Supplies Serve to Match Load to Source

There are many commonly available sources of electrical power as well as endless types of sources yet to be discovered or developed. We also have countless applications for this power.

However, most applications can not take power directly from the source. There must be a matching process that changes the  source power to useable power for applications. This matching process is the function of the electronic power supply.

Notice that the phrase “electronic power supply” is a misnomer. An electronic power supply does not create power — rather, it simply transforms the available source power to a useful form for your application.

Figure 1 illustrates the relationships between the source and the power supply and the power supply and the load.

Figure 1: Power supply relationsip with the source and the load.

A System Level Approach Needed at the Right Time

Approaching power supply application, specification, and design with a system level perspective is of critical importance for the success of projects. The system includes the source, the load, and even the environment around the power supply. Additionally the system power supply must be treated with the same importance as other aspects of the system design.

The source and load characteristics must be understood before the power supply requirements are determined. The time to evaluate for power supply specifications is right after the initial load and source characteristics are known. It is quite common that a suitable power supply design is not reasonably possible given the initial load and source characteristic determination. If this is the case, either the load or source characteristics need to be changed before proceeding further with the system design. Otherwise, the result will be a failed project or a project with extremely high cost overruns. This problem is a very common mistake that is easily preventable.

A Major Cause of Project Catastrophes

Perhaps a reason for project failures is a belief that electronic power supplies are perfect black boxes, capable of perfectly supplying power to the load. They are not perfect black boxes and failure to consider their limits and adverse behavior can be catastrophic to a project program.

The cost to make make design changes increases exponentially as time in the development cycle progresses. This exponential characteristic happens due to the work that must be done to re-document, re-test, and re-work designs and existing product. This is called the waterfall effect. Problems not found until late in the development cycle can prove to have catastrophic cost consequences. Don’t think that the power supply design can wait till the end! Design power supplies into your system at the right time.

Power Supplies are Multi-Disciplinary and Complex

Electronic power supplies, especially switch-mode type, have very complex analog energy transfer processes and require a diverse skill set to design. The skill set includes not only knowledge of high frequency with high power analog electronics, but also sufficient knowledge of mechanical packaging and heat transfer concepts to prevent the unit from overheating.

Many vendors have simplified switching power supplies for general purpose applications. However, a system knowledge of the source and the load are still important as well as understanding the characteristics and limitation of the power supply itself.

Upcoming Topics

This series of articles about specifying power supplies with a system perspective will cover in more detail the following system level concerns. Some of these concerns are:

• Load Characterization
• Source Characterization
• Efficiency
• Thermal Environment
• Packaging

Watch for the upcoming articles on “Specifying Electronic Power Supplies from a System Point of View”.

If you need assistance with power electronics design, call or email us today for help with your requirements. You can also go to our power electronics consultant website for more information about our services for business clients. Thank you for reading this tutorial article entitled “Specifying Electronic Power Supplies from a System Point of View: Introduction”

The post Specifying Power Supplies for a System: Introduction appeared first on POWER ELECTRONICS CONSULTANT.

This tutorial installment is: The Isolated Power Supply. This topic answers the following questions:

• What is power supply isolation?
• What are the main purposes of power supply isolation?
• What are the methods of power supply isolation?
• What are power supply isolation parasitics?
• How is power supply isolation measured?

To view a different topic, go to the Power Supply Tutorial table of contents.

Last topic: Power Supply Conduction Modes

Next topic: Power Supply Topologies

What is Power Supply Isolation?

In the context of power supply design, isolation is the electrical and sometimes magnetic separation between two circuits in close proximity to each other.

Main Purposes of Power Supply Isolation

There may be many purposes for isolation. Some of the most common are:

Safety

Electronic power supplies commonly process dangerous voltages with low impedances. Isolation is often required to prevent operator contact with dangerous voltages. Transformers used within power supplies function as a safety isolation transformer.

Voltage Level Shifting

Power supply designs must often accommodate loads at different potential voltages than the source. Isolation is often required to achieve the potential level shifting. Within the power supplies themselves, voltage level shifting devices may be required to couple energy or signals to circuits at two or more different voltages. Such an example is a gate drive transformer used for high side switch control.

Enable Step-Up Conversion Using Buck Derived Topologies

The buck converter has a conversion ratio that is a linear function of duty. This characteristic is very desirable. However, the buck converter is a step-down converter only. To achieve a conversion ratio greater than one without a transformer, one must use a converter topology such as a boost, buck-boost, non-inverting buck-boost, Cuk, SEPIC, etc. However, these topologies all have non-linear conversion ratios. To achieve conversion ratios greater than one with a linear conversion ratio, a transformer isolated derivative of the buck converter can be used. This type of converter can even be used to achieve a buck-boost type characteristic where the input voltage can range greater or less than the output voltage.

Non-buck derived topologies with non-linear conversion characteristics can also use transformers for isolation and assisting with step-up and step-down conversion. The most common example is the flyback topology (the transformer in the flyback more correctly functions as a multiple winding inductor).

Obtaining Multiple Output Converters

The isolating characteristics of a transformer also allow the design of power supplies with multiple outputs by adding windings to the transformer along with rectifier and filter components. A very common example of this type of power supply is the desktop computer supply with +12, +5, and +3.3 volt outputs.

Ground Loop Prevention

Isolation between circuits can also be used for the purpose of preventing ground loops. Ground loops occur when two or more circuits share a common return path. When ground loops occur, there is the high likelihood that the signal voltage developed by current from one of the circuits on the return path will disrupt the operation of the other circuit.

Providing Galvanic Isolation

Electrical isolation inherently provides galvanic isolation since galvanic corrosion depends on the conduction of electrical charge.

Power Supply Isolation Methods

There are at least three methods for achieving isolation in power supplies:

Physical Separation

The most obvious form of power supply isolation is simple physical separation — used when there is no electrical, magnetic, or thermal interaction desired. The separation may employ different types of dielectric mediums between the conducting surfaces.

Transformers

Transformers provide electrical isolation, but allow power to be magnetically coupled through from primary to secondary. They are used when it is desired to transfer power across the power supply isolation boundary and can be designed for safety isolation, voltage level translation, step-up, step-down functions, and for obtaining multiple outputs.

Optocouplers

Opto-couplers are used to transfer signals across different voltage levels, and without introducing significant parasitics across the boundary. There are at least two basic types:

IC Package

The optocoupler in an IC package consists of a light emitting device and a light receiving device inside the same IC package. Both are semiconductor devices. The efficiency of transfer is described by the Current Transfer Ratio (CTR). The CTR ages with input drive level and with operating temperature making careful design with these devices important. In power supplies, they are commonly used to transfer feedback from the secondary to the primary across the power supply isolation boundary. Typical isolation voltages for this type of device are on the order of 3kV.

Optical Fibers

High voltage power supplies can make use of optocouplers with a data transmission fiber between the transmitter and the reciever. This form of optocoupler can achieve tens and even hundreds of kilovolts of isolation while processing control and data signals.

Power Supply Isolation Parasitics

Isolation is never perfect. It is a poor practice to assume that if conductors do not touch, then they are isolated. The following parasitic parameters are responsible for undesirable isolation boundary performance:

Imperfect Insulators

All insulators have some degree of conductivity, resulting in leakage current.

Surface Tracking

Surface tracking is caused by conduction contaminants on the insulator surfaces between conductors. This type of parasitic is commonly responsible for circuits with extremely high lumped resistance values not working as planned. The greater the voltage potential between the conductors, the greater is the tracking current. If the combination of contaminant surface density is great enough or the voltage potential is great enough, an arc will occur leaving a carbon trail which is difficult to remove. Once the carbon trail is formed, the voltage holdoff capability at that location is compromised.

Dielectric Breakdown

Dielectric breakdown occurs when the electric field strength across a dielectric medium is great enough to cause electrons to be stripped from their normal orbiting locations around the atoms. If the dielectric is not renewable, the reliability of the part is compromised. If the dielectric breakdown occurs along an insulation surface between two conductors, a carbon path is left which will result in surface tracking at that location.

Stray Capacitance

Every insulator material used in isolation applications exhibits capacitance which is a function of the area of and distance between the effective conducting surfaces, as well as the dielectric constant of the material. At frequencies greater than DC, there will be some current flowing through the effective capacitor. This effect causes two circuits to be DC isolated but not AC isolated. If the circuits are physically close enough to each other, and the frequency components are high enough, one circuit will be able to disrupt the operation of the other circuit. This is known as “crosstalk”. Stray capacitance between primary and secondary windings is a common source of objectionable common mode currents and can cause power supplies to fail emissions testing.

Leakage Inductance

Transformers will always have a parasitic called leakage inductance. It is caused by flux from one winding not linking with the other winding(s). Leakage is typically seen as an undesirable parasitic that should be minimized. In resonant supplies it is possible to use it advantageously.

Mutual Inductance

Mutual inductance causes undesired linking between two different circuits. This is usually a problem when there are large magnitude currents with rapid switching transients in close proximity to sensitive nodes of other circuits.

Measurement of Power Supply Isolation

There are at least two methods of measuring isolation quality:

Resistance Measurement

One method of measuring isolation quality is to measure the resistance between two isolated circuits.

Hi-Pot Test

Another method of measuring isolation quality is to perform a “Hi-Pot” test. This test applies either a DC or an AC voltage across two isolated circuits. The resulting leakage current is measured. If the leakage current fail exceeds a specified value, the device under test fails.

Next Topic

The next tutorial installment is Power Supply Topologies. This topic answers the following questions:

• What is a power supply topology?
• What are the most basic topologies?
• What are the derivative topologies of the most basic topologies?
• What are the other topologies in use?

If you need assistance with power electronics design, call or email us today for help with your requirements. You can also go to our power electronics consultant website for more information about our services for business clients. Thank you for reading this tutorial article entitled “Power Supply Isolation”

Next topic: Power Supply Topologies

Back to Power Supply Tutorial table of contents.

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This tutorial installment is: The Achille’s Heel of Electronics Products. The power supply often becomes the Achille’s heel of electronic product design. Why?

This topic answers the following questions about power supplies:

• What are the pitfalls of their implementation?
• Why are they the system weak link?
• When is the best time to develop system power requirements?
• What is the correct perspective with which to approach their implementation?

To view a different topic, go to the Power Supply Tutorial table of contents.

Last topic: What is a Power Supply?

Next topic: Unregulated Power Supplies

Pitfalls of Power Supply Implementation

• Assuming that it is a perfect black box: Supplies are less than perfect devices. Not only do converter characteristics and performance affect the load operation, but the load characteristics also affect converter behavior. The same type of interaction also exists at the input of the converter with the source. Finally, the load characteristics can be indirectly reflected to the source through the power supply and vice versa.
• Assuming that it is a simple aspect of product design: Converters are often not simple. The design of converters will usually go beyond the skill set of most non-power electronics engineers. Even the application of off the shelf conversion devices can be a challenge as the documentation that accompanies them is usually limited, with little disclosure about the internal design which may significantly impact compatibility with loads and sources.
• Allowing it to be an afterthought in the design process: Since the power supply is not a perfect black box, it cannot be relegated as an afterthought in the design process. Product design must take place keeping converter capabilities in mind. Otherwise it is possible to design a great product, but have no power supply for it.
• Failure to allocate adequate physical space for it: Conversion devices need space. While technology for improving efficiency is continually improving allowing for smaller supplies, it is a mistake to not plan for space for converters.
• Failure to adequately specify the important performance requirements: There are numerous specifications which a power supply must satisfy. If they are not identified, poor performance is the likely result.

The Power Supply is Usually the Weak Link

Conversion devices are usually the weak link in most electronics products and usually will be the first components to fail. The stress levels on the internal conversion components are usually much higher than in other electronics components. Forms of stress include voltage, current, power, and temperature. All of these forms of stress have major impact upon component reliability and lifetime. Therefore, reliability of the product is usually dominated by the power conversion choice. For this reason and others, the converter must not be relegated as an afterthought in the design process.

When to Develop the Power Supply Design Plan

The plan for implementation should be developed before the product design review which is a critical milestone to be completed before hardware is built. There must be confidence that a reasonable approach exists before committing to hardware. Not completing this vital check in a product design is an invitation to disastrous results, cost overruns, and schedule delays. Don’t fall into the trap of assuming that the power supply is a trivial component. They usually are not. Identifying the specifications should be an important of the plan. Please download the Applications and Specifications Requirements Form.pdf for help with this task.

The Correct Perspective for Power Supply Implementation

The power converter must be seen as a critical component in the system. Without a thoughtful  implementation, the system will perform poorly at best. Remember that there are usually significant interdependencies between the power supply and the load and the source. Treating it as a black box or as an afterthought will usually lead to late stage and costly surprises. Finding the cheapest implementation usually leads to poor value and prototyping troubles. Put extra effort to seek the best value which is a compromise of low cost, outstanding performance, small size, and reliability. These factors are typically weighted according to their relative importance in your application.

Next Topic

The next tutorial installment is: Unregulated Power Supplies. This next topic will answer the following questions:

• What are unregulated power supplies?
• What are the basic types of unregulated power supplies?
• What are the advantages and disadvantages of unregulated power supplies?

If you need assistance with power electronics design, call or email us today for help with your requirements. You can also go to our power electronics consultant website for more information about our services for business clients. Thank you for reading this tutorial article entitled “The Achilles Heel of Electronics Products”

Next topic: Unregulated Power Supplies

Back to table of contents.

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This tutorial installment is: Power Supply Conduction Modes. This topic answers the following questions:

• What are power supply conduction modes?
• What are the effects of conduction modes on power supply performance?

To view a different topic, go to the Power Supply Tutorial table of contents.

Last topic: Power Semiconductor Switches, MOSFETs and Schottky Diodes

Next topic: Power Supply Isolation

Power Supply Conduction Mode Explanation

The earlier tutorial installment titled Power Supply Capacitors and Inductors discussed how inductors are energy storage devices. The energy stored is proportional to the square of the current through the inductor. During times of light loading and when using passive rectifying diodes rather than synchronous rectification, the current through the inductor can fall to zero. This condition is known as discontinuous conduction mode (DCM) operation. When the inductor current never falls to zero, or when the power supply employs synchronous rectification, the condition is said to be in continuous conduction mode (CCM).

With synchronous rectification, active switches are used for rectifiers and current flow can actually reverse direction allowing the current to continue to flow. Therefore, unless the synchronous switch is commanded to turn off, the conduction mode will always be continuous.

Effects in Discontinuous Conduction Mode vs. Continuous Conduction Mode

Advantages of DCM over CCM:

• No right half plane zero (RHPZ) in boost, buck-boost, flyback topologies: The CCM boost, buck-boost, and flyback topologies have a RHPZ in their control to output transfer function. This means that if, for example, the load current increases causing the output voltage to initially dip, the response of these topologies will initially correct in the wrong direction before correcting in the right direction. The right half plane zero is nearly impossible to compensate for in the compensation loop. As a result, the control loop in these CCM coverters is typically made to cross over at a frequency much lower than the RHPZ frequency resulting in lower transient response bandwidths. The DCM version of the boost, buck-boost, and flyback converters do not have a right half plane zero and can have higher loop crossover frequency allowing higher transient response bandwidths.
• Single pole transfer functions: In the buck, boost, buck-boost, and all topologies derived from these, the input to output and control to output transfer functions contain single pole responses while operating in DCM. Converters with only single pole transfer functions are easier to compensate than converters having a double pole response.

Disadvantages of DCM over CCM:

• Conversion ratio is dependent upon load: While operating in CCM, the DC conversion ratio (the output voltage divided by the input voltage), is independent of the load, to a first order basis. This characteristic makes DC analysis of converters operating in CCM easier. However, while operating in DCM, the DC conversion ratio is dependent upon load, complicating the DC analysis.
• Ringing: When the inductor current reaches zero while in non-synchronous operation, the end of the inductor connected to the switch (also called the freewheel end), must immediately transition to the voltage at the other end of the inductor. However, there will always be inductive and capacitive parasitic elements which will cause severe ringing if damping is not implemented. It is possible for this ringing to exceed switch voltage ratings. It is also possible for this ringing to be a source of radiated and conducted emissions. Lastly, this ringing can produce undesirable noise at the output of the power supply.
• Higher peak and RMS currents for same power output in boost, buck-boost, and derived topologies including flyback: Boost, buck-boost, and derived topologies including the flyback are commonly operated only in DCM to avoid the adverse effects of the RHPZ described earlier. However, to achieve the same power in DCM as in CCM, the peak and RMS currents are substantially higher resulting in greater losses in the conduction paths and greater ringing  because the energy stored in inductances is proportional to the square of the current. Energy stored that is not delivered to the output causes ringing and losses.
• Physically larger transformers and inductors required for same power output: In DCM, the inductance must be much smaller in value to allow the current to fall to zero before the start of the next cycle. Smaller inductance results in higher RMS and peak inductor currents. Because the RMS and peak currents are greater in DCM than in CCM, the transformers must be sized larger to accommodate greater flux swings and copper and core losses.

Next Topic

The next tutorial installment is Power Supply Isolation. This topic answers the following questions:

• What is power supply isolation?
• What are different types of isolation?
• What are the effects of non-ideal isolation?

If you need assistance with power electronics design, call or email us today for help with your requirements. You can also go to our power electronics consultant website for more information about our services for business clients. Thank you for reading this tutorial article entitled “Power Supply Conduction Modes”

Next topic: The Isolated Power Supply

Back to Power Supply Tutorial table of contents.

The post Tutorial: Power Supply Conduction Modes appeared first on POWER ELECTRONICS CONSULTANT.

This tutorial installment is: Power Semiconductor Switches | Power MOSFETs and Schottky Diodes. This topic answers the following questions:

• What are the majority carrier power semiconductor switches used today?
• What are the typical applications for these switches?

To view a different topic, go to the Power Supply Tutorial table of contents.

Last topic: Power Semiconductor Switches, PIN Diode, BJT, IGBT, Thyristor

Next topic: Conduction Modes

As shown in the installment of this tutorial entitled Power Semiconductor Switches, Classification, power semiconductor switches can be classified by the type of charge carriers: minority carrier devices or majority carrier devices. This topic will discuss majority carrier devices. For a discussion of minority carrier devices, please see the topic Power Semiconductor Switches, PIN Diode, BJT, IGBT, Thyristor.

Majority Carrier Device Family

Majority carrier devices do not store significant minority carriers and therefore have turn on and turn off times an order of magnitude faster than minority carrier devices. Switching times of majority carrier devices are less than 200nS and frequently very much less. Consequently, the maximum practical switching frequency of a power supply with majority carrier active switches can reach 1MHz and beyond.

Power Metal Oxide Semiconductor Field Effect Transistor (MOSFET)

We will discuss the N-channel enhancement mode power MOSFET for this tutorial topic. There is also a P-channel enhancement mode power MOSFET for some power supply applications.

The power MOSFET  has three terminals: drain, gate, and source. The gate to source voltage controls the conduction state of the power MOSFET. There is an insulating layer between the gate and an electrostatically controlled conduction channel between the drain and the source. Application of a gate to source voltage greater than the device threshold voltage will cause the power MOSFET to turn on by modulating the geometry of the electrostatic conduction channel.

Power MOSFETs also contain a slow reverse recovery time anti-parallel body diode from the drain to the source.

Parasitic parameters of the power MOSFET:

• R_ds, the on state drain to source resistance, which causes conduction losses and non-zero voltage drop across the on state switch,
• Leakage resistance during the off state,
• Cdg, the Miller, drain to gate, or reverse transfer capacitance, which slows the turn-on and turn-off transition time of the transistor switch as well as potentially being a source of instability and dV/dT turn on problems,
• Cgs, the gate to source capacitance, which contributes a delay time to the turn-on and turn-off of the transistor switch.

Advantages of the power MOSFET:

• Voltage controlled, high input impedance device, easier than current control of BJT.
• Fast switching speed because they are free from minority carrier stored charge.

Disadvantages of the power MOSFET:

• Can be susceptible to thermal runaway in power supply applications requiring constant current.
• Fast transient switching induces greater radiated and conducted emissions (EMI).
• Devices with breakdown voltages of 600V or higher typically have greater on-state voltages than comparable minority carrier devices.

Power MOSFET maximum ratings available from Digi-Key as of 3/2011:

• Maximum drain to source breakdown voltage, (V_DS):  4000 volts.
• Maximum drain current, (I_D):  600A.
• Maximum apparent power, (V_DS*I_D):  56kVA¹

Silicon Carbide Power MOSFET

Silicon carbide (SiC) is an emerging semiconductor material for use with power MOSFET’s. These devices have an R_DSon about one third that of comparable silicon power MOSFETs, allowing for on state voltages comparable to IGBT’s. This feature opens the door to high power applications for power MOSFET’s with breakdown voltages over 600V. Since the silicon carbide power MOSFET is a majority carrier device, there is no associated storage time to cause the well know current tail characteristic of IGBT’s. Consequently, silicon carbide power MOSFET’s enable high voltage switching at frequencies greater than 50kHz.

Additionally, the total gate charge on a silicon carbide power MOSFET is actually about 3 times less than for a comparable silicon power MOSFET, resulting in yet further gains in the upper frequency limit and/or reduction of switching loss.

Furthermore, the silicon carbide material is relatively insensitive to operating temperature, allowing an R_DSon which is stable over the operating temperature. The maximum junction temperature is 200 degrees C.

Advantages of the silicon carbide power MOSFET:

• Low on-state drain to source voltage due to low R_DSon
• Low total gate charge
• R_DSon changes little as temperature is increased
• Higher maximum junction temperature

Disadvantages of the silicon carbide power mosfet:

• Gate drive requires greater voltage for full enhancement, and slightly negative values for reliable cutoff.
• Thoughtful consideration of parasitic layout parameters required due to very fast switch transitions.
• Likely to generate greater emissions due to rapid switch transitions.
• Cost

As of 3/2011 manufacturers of SiC MOSFETs include Cree and Powerex.

Gallium Nitride MOSFETs

Gallium Nitride (GaN) is another emerging semiconductor material for use with power MOSFET’s with breakdown ratings of 200V or less. These devices have a total gate charge approximately one fifth that of comparable silicon MOSFETs and an R_DSon about half or less. This feature opens the door to switching applications well above 2MHz in frequency, greatly reducing component size for non-isolated topologies and facilitating large step down ratios in buck converters.

Advantages of the Gallium Nitride power MOSFET:

• Very low total gate charge
• Low R_DSon resulting in lower conduction losses
• RDSon changes less than silicon power MOSFETs  as temperature is increased
• Device is fully enhanced with a gate to source voltage of 5 volts.

Disadvantages of the G allium Nitride power mosfet:

• Thoughtful consideration of parasitic layout parameters required due to very fast switch transitions.
• Likely to generate greater emissions due to rapid switch transitions.

Gallium Nitride Power MOSFET maximum ratings available from Digi-Key as of 3/2011:

• Maximum drain to source breakdown voltage, (V_DS):  200 volts. (Update on 5/27/2011: EPC gave a GaN overview and roadmap presentation on May 11th at the IBM Power Symposium. Plans were announced for availability of 600V GaN devices sometime in 2011, and possible availability of 1200V devices in 2012.)
• Maximum drain current, (I_D):  33A.
• Maximum apparent power, (V_DS*I_D):  6.6kVA¹

As of 3/2011 manufacturers of GaN MOSFETs include Efficient Power Conversion (EPC).

Silicon Schottky Diodes

The power versions of the silicon Schottky diode also have broad applicability in switching power supplies. Being majority carrier devices, silicon Schottky diodes do not have minority stored charge and therefore have zero reverse recovery time. However, silicon Schottky diodes have roughly 10 times as much junction capacitance which can have similar effects as reverse recovery time as well as ringing with parasitic inductance in the circuit.

Silicon Schottky diodes have substantially less forward voltage drop than their non-Schottky counterparts, which can be used advantageously to reduce conduction losses or to tweak output voltage for certain topologies.

An undesirable characteristic of silicon Schottky diodes is much greater reverse leakage current which can be problematic at elevated temperatures, causing substantial dissipation on the device and loss of efficiency.

Advantages of silicon Schottky diodes:

• Zero reverse recovery time
• Substantially less forward voltage drop compared to conventional diodes

Disadvantages of silicon Schottky diodes:

• Ten times greater junction capacitance than conventional diodes
• Substantially greater leakage current compared to conventional diodes

Silicon Schottky Diode Maximum ratings available from Digi-Key as of 3/2011:

• Maximum collector to emitter breakdown voltage, (V_RRM):  250 volts²
• Maximum collector current, (I_F):  140A
• Maximum apparent power (V_RRM * I_R):   24kVA¹

Silicon Carbide Schottky Diodes

Silicon carbide Schottky diodes, being majority carrier devices, do not store minority carrier charge and therefore do not have a reverse recovery time. Additionally, the silicon carbide semiconductor has excellent stability characteristics over the operating temperature range as well as increased maximum junction temperature. Unlike the silicon Schottky diode, the forward voltage drop and junction capacitance of a silicon carbide Schottky diode are comparable to the non-Schottky diodes. Like the silicon Schottky diodes, the silicon carbide schottky diodes have substantially greater leakage current compared to conventional diodes.

Advantages of silicon Carbide Schottky diodes:

• Zero reverse recovery time
• Relatively insensitive to operating temperature change
• Greater maximum junction temperature

Disadvantages of silicon carbide Schottky diodes:

• Substantially greater leakage current compared to conventional diodes

Silicon Carbide Schottky Diode Maximum ratings available from Digi-Key as of 3/2011:

• Maximum  breakdown voltage, (V_RRM):  1700 volts
• Maximum forward current, (I_F):  25A
• Maximum apparent power (V_RRM * I_F):   42.5kVA¹

Gallium Arsenide (GaAs) Schottky Diode

Gallium arsenide Schottky diodes have the lowest junction capacitance of all power semiconductor diodes. Consequently, they are able to operate at switching frequencies of 5MHz and beyond.

Advantages of GaAs Schottky Diodes:

• Lowest junction capacitance
• Temperature stable

Disadvantages of GaAs Schottky Diodes:

• Limited documentation

GaAs Schottky Diode Maximum ratings available from Digi-Key as of 3/2011:

• Only one breakdown rating available: 300V
• Maximum forward current, (I_F):  29A
• Maximum apparent power (V_RRM * I_F):   8.7kVA¹

Next Topic

The next tutorial installment is Conduction Modes. This topic answers the following questions:

• What are power supply conduction modes?
• What are the effects of conduction modes on power supply performance?

If you need assistance with power electronics design, call or email us today for help with your requirements. You can also go to our power electronics consultant website for more information about our services for business clients. Thank you for reading this tutorial article entitled “Power Semiconductor Switches | Power MOSFETs and Schottky Diodes”

Next topic: Power Supply Conduction Modes

Back to Power Supply Tutorial table of contents.

Notes:

¹ As used in this article apparent power is a relative figure of merit for power handling comparison. It does not indicate the absolute power through put capability of the device.

² Silicon Schottky diodes with breakdown voltages greater than 100 volts exhibit some reverse recovery time even though they are still classified as Schottky devices.

References

[1]    Reid L. Sprite, “Power Semiconductors: The BJT, MOSFET, and IGBT”, December, 2004.

[2]    Ned Mohan, Tore M. Underland, and William P. Robbins, Power Electronics, 2^nd Edition, New York, NY, John Wiley & Sons, 1995.

[3]    Robert W. Erickson, Dragan Maksimovic, Fundamentals of Power Electronics, 2nd Edition, Norwell, MA, Kluwer Academic Publishers, 2001.

The post Tutorial: Semiconductor Switches | Power MOSFETs and Schottky Diodes appeared first on POWER ELECTRONICS CONSULTANT.

This tutorial installment is: Power Semiconductor Switches | PIN Diode, BJT, IGBT, Thyristor. This topic answers the following questions:

• What are the minority carrier power semiconductor switches used today?
• What are the typical applications for these switches?

To view a different topic, go to the Power Supply Tutorial table of contents.
Last topic: Power Semiconductor Switches, Classification
Next topic: Power Semiconductor Switches, MOSFETs and Schottky Diodes

As shown in the last installment of this tutorial, power semiconductor switches can be classified by the type of charge carriers: minority carrier devices or majority carrier devices. This topic will discuss minority carrier devices. For a discussion of majority carrier devices, please see the topic Power Semiconductor Switches, MOSFETs and Schottky Diodes.

Minority Carrier Device Family

Minority carrier devices have charge storage times of a few hundred nanoseconds to a few microseconds. Consequently the switching time is limited to this order of magnitude, and the maximum practical switching frequency of a power supply with minority carrier active switches is limited by the storage time to about 50 to 100 kHz. Some device types have greater minority charge storage and/or more limited methods of minority charge removal, resulting in further frequency limitations. The minority carrier devices used today are the PIN diode, BJT, IGBT, and the thyristor.

PIN Diode

The power versions of the PN junction diode have broad applicability in switching power supplies. Besides the usual breakdown voltage and rated current, the other main consideration in selecting a diode for rectification use is the reverse recovery time. The PIN diode is the same as a PN diode but with the addition of an intrinsic layer between the P and the N layers. This intrinsic layer provides the breakdown voltage capability of the device since under reverse bias conditions, it is devoid of charge carriers.

Line frequency rectifiers can use standard recovery time diodes. Switching power supply applications using minority carrier transistors such as IGBT’s or BJT’s require diodes with fast recovery times of less than 500nS. Switching power supply applications using majority carrier devices such as power MOSFETs require ultra fast recovery times of less than 100nS.

Advantages of the PIN Diode:

• Inexpensive
• Does not require control

Disadvantages of the PIN Diode:

• Has a reverse recovery time which contributes to power loss

PN Diode Maximum ratings available from Digi-Key as of 3/2011:

• Maximum breakdown voltage, (V_RRM):  4500 volts
• Maximum current, (I_F):  600A
• Maximum apparent power (V_RRM * I_R):   2137kVA¹

Bipolar Junction Transistor (BJT)

The BJT is an older technology. Switching power supply applications for BJTs include switching voltages over 600V at frequencies less than 20kHz. Due to conductivity modulation effects, the BJT can exhibit lower on state collector-emitter voltage than the drain-source voltage across a comparable MOSFET.  The BJT has three terminals: collector, base, and emitter. The BJT conduction state is controlled by the level of current injection into the base terminal. The governing relationship is:

The current gain, h_FE, for a power BJT may be in the range of 20-100 for lighter collector currents. However, as maximum rated collector collector current is approached, hFE, degrades to the range of  5-10 making control of the device more difficult. Additionally, V_CEsat increases causing much greater conduction losses.

The BJT also has substantial storage charge which limits its ability to turn off quickly. Typical storage time and collector fall time is in the range of 1-5 microseconds. This turn-off time limits the maximum practical switching frequency of power supplies using BJT’s as the power semiconductor switch.

Advantage of the power BJT:

• In low power and lower switching frequency applications, the slower switching speed can be used to minimize EMI generation, reducing or eliminating the requirements for input EMI filtering. Power supply cost and size reductions result.
• Lower on state voltage relative to a comparable power MOSFET’s for devices with ratings over 600 volts.

Disadvantages of the power BJT:

• Substantial control current required, resulting in efficiency issues,
• Substantial turn-off storage time resulting in slow switching times and therefore relatively slow maximum switching frequencies.

Power BJT Maximum ratings available from Digi-Key as of 3/2011:

• Maximum collector to emitter breakdown voltage, (V_CEO):  1200 volts
• Maximum collector current, (I_C):  60A
• Maximum apparent power (V_CEO * I_C):   28.8kVA¹

Insulated Gate Bipolar Transistor (IGBT)

The IGBT is a recent technology. Switching power supply applications are for switching voltages over 600V at frequencies less than 100kHz and for higher power levels than either the BJT or power MOSFET can support.  The IGBT, is a three terminal hybrid of the BJT and power MOSFET. Internally, the drain of an N-channel power MOSFET sinks current from the base of a PNP BJT. Therefore, the IGBT has a high impedance input similar to a MOSFET. It also has a collector-emitter output which has a large breakdown voltage and a low on state voltage as in a BJT. IGBT technology has been greatly improved, resulting in shorter turn off delay times compared to the BJT.

Advantages of the IGBT:

• Voltage controlled, high input impedance device, easier than current control of BJT.
• For devices with higher voltage ratings, the on state voltage is much lower than that of a comparable MOSFET.
• Power handling capability is ten times better than power MOSFETs or BJT’s
• Shorter delay times relative to the BJT, about 300nS to 1500nS.

Disadvantages of the IGBT:

• Have a current tail turn-off characteristic which results in longer delay times relative to the power MOSFET.

IGBT Maximum ratings available from Digi-Key as of 3/2011:

• Maximum collector to emitter breakdown voltage, (V_CEO):  4000 volts
• Maximum collector current, (I_C):  400A
• Maximum apparent power (V_CEO * I_C):   340kVA¹

IGBT Modules

IGBT modules (parallel-serial combinations of  IGBTs in the same package) with VA ratings of over 4000kVA are available from Digi-Key.

Thyristors

The thyristor family includes the silicon controlled rectifier, and the gate turn-off thyristor.

Silicon Controlled Rectifier (SCR)

The SCR is the oldest technology used in power switching applications.  SCR applications primarily involve either phase control of AC line power or electronic crowbars where it is desired to rapidly dump energy stored in a large capacitor. Because an SCR has a large turn-off time, it is not suitable for switching applications  greater than 400Hz.

The SCR has three terminals: anode, gate, and cathode. Conduction from the anode to the cathode begins when current is injected into the gate. A conducting SCR looks like a diode, and once conduction begins, the SCR latches on so than removal of the gate drive does not turn the SCR off. The SCR can only be turned off when the anode to cathode current falls below the holding current specification or reverses. Before the SCR can turn off, the minority charge carriers must be removed by the reverse current or recombination effects.

Advantages of the SCR:

• Operating characteristics lends the SCR to phase control of AC power and for crowbar applications.
• Lowest cost per kVA of all power semiconductor switches.²
• Large power handling capability.

Disadvantages of the SCR:

• Substantial minority carrier charge storage time, limiting upper switching frequency to 400 Hz or less.

SCR Maximum ratings available from Digi-Key as of 3/2011:

• Maximum anode to cathode breakdown voltage, (V_AK):  3800 volts
• Maximum anode current, (I_A):  3360A
• Maximum apparent power (V_AK * I_A):   6726kVA¹

Gate Turn-Off Thyristor (GTO)

The GTO thyristor is similar to the SCR but can be turned off through application of negative current to the gate electrode. This turn off capability expands the areas of applications to include not only phase control of AC line power, but also variable speed motor drive and inverters as well. Additionally, the GTO thyristor is able to switch somewhat faster than the SCR.

As of this time (3/2011), Digi-Key is not stocking GTO thyristors. See the Thomas Register for suppliers and distributors, but expect long lead times for these specialty components.

Next Topic

The next tutorial installment is Power Semiconductor Switches, MOSFETs and Schottky Diodes. This topic answers the following questions:

• What are the majority carrier power semiconductor switches used today?
• What are the applications for these switches?

If you need assistance with power electronics design, call or email us today for help with your requirements. You can also go to our power electronics consultant website for more information about our services for business clients. Thank you for reading this tutorial article entitled “Power Semiconductor Switches | PIN Diode, BJT, IGBT, Thyristor”

Next topic: Power Semiconductor Switches, MOSFETs and Schottky Diodes
Back to Power Supply Tutorial table of contents.

Notes:

¹ As used in this article apparent power is a relative figure of merit for power handling comparison. It does not indicate the absolute power through put capability of the device.

² See page 88 of Reference 4.

References

[1]    Reid L. Sprite, “Power Semiconductors: The BJT, MOSFET, and IGBT”, December, 2004.

[2]    Ned Mohan, Tore M. Underland, and William P. Robbins, Power Electronics, 2^nd Edition, New York, NY, John Wiley & Sons, 1995.

[3]    Yong “Perry” Li, “Why Consider a BJT over a MOSFET?”, EETimes, 10/25/2010.

[4]    Robert W. Erickson, Dragan Maksimovic, Fundamentals of Power Electronics, 2nd Edition, Norwell, MA, Kluwer Academic Publishers, 2001.

The post Tutorial: Semiconductor Switches | PIN Diode, BJT, IGBT, Thyristor appeared first on POWER ELECTRONICS CONSULTANT.

This tutorial installment is: Power Semiconductor Switches, Classification. This topic answers the following questions:

• What are the main power semiconductor switch classifications?
• What are the important properties of the main classifications?

To view a different topic, go to the Power Supply Tutorial table of contents.
Last topic: Power Semiconductor Switches, Ideal Switches
Next topic: Power Semiconductor Switches | PIN Diode, BJT, IGBT, Thyristor

Power Semiconductor Switch Classification

Power semiconductor devices can be classified in at least two ways:

• by type of charge carrier,
• by active vs. passive function.

Charge Carrier Classification

Power semiconductor devices can have two modes of charge carrier conduction:

• minority carrier, where charge is carried by electrons in a P-type semiconductor, or by holes in an N-type semiconductor, or
• majority carrier, where charge is carried by electrons in an N-type semiconductor, or by holes in a P-type semiconductor.

Understanding what type of charge carrier conduction a device has helps us to understand its most basic properties and suitability for different applications.

Minority Carrier Devices

Minority carrier devices excel for applications involving higher voltage levels. Minority carrier devices used for power semiconductors have a p-n^– junction where the n^– region is very lightly doped or intrinsic. Since, under reverse bias conditions, the n^– region is nearly devoid of charge carriers and therefore has low conductivity, it can sustain a large breakdown voltage.

When the device is forward biased, minority carriers are injected into this same n^– region, resulting in a great increase in conductivity, so that under forward bias conditions, the on-state voltage is relatively low. This change in the conductivity is referred as “conductivity modulation”. Comparably rated majority carrier devices for high voltage applications would actually have a higher on-state voltage due to the product of current and channel resistance.

However, minority carrier devices are slow to turn-on and turn-off due to a large stored minority carrier charge which must be inserted or removed prior to the device changing state. This effect limits the maximum practical switching frequency of these types of power devices to 50-100kHz.

Majority Carrier Devices

Majority carrier devices excel for applications involving lower voltage levels and for higher frequencies. Majority carrier devices have fast switching times because they do not store minority charge. They operate either by electrostatic control of conduction cross-sectional area or by employing a metal semiconductor junction. Neither method involves minority carriers.

Active vs. Passive Devices

Power semiconductor switches can further be classified according to whether they are passive responding devices or actively controlling devices.

Passive Responding Devices

Passive devices change conduction state based upon the external voltage and current conditions. They do not need to be controlled. For example, when the current through a diode attempts to change direction, the diode turns off. When the diode becomes forward biased, it turns on.

Active Controlling Devices

Active controlling devices are typically three terminal devices and change from a blocking state to a conducting state as commanded by a control input signal. Active devices control the operation of a switching power supply.

Next Topic

The next tutorial installment is: Power Semiconductor Switches | PIN Diode, BJT, IGBT, Thyristor. This topic answers the following questions:

• What are the minority carrier power semiconductor switches used today?
• What are the applications for these switches?

If you need assistance with power electronics design, call or email us today for help with your requirements. You can also go to our power electronics consultant website for more information about our services for business clients. Thank you for reading this tutorial article entitled “Power Semiconductor Switches | Classification”

Next topic: Power Semiconductor Switches | PIN Diode, BJT, IGBT, Thyristor
Back to Power Supply Tutorial table of contents.

References

[1]     Robert W. Erickson, Dragan Maksimovic, Fundamentals of Power Electronics, 2nd Edition, Norwell, MA, Kluwer Academic Publishers, 2001.

The post Tutorial: Classes of Power Semiconductor Switches appeared first on POWER ELECTRONICS CONSULTANT.

This tutorial installment is: Power Semiconductor Switches, Ideal Switches. This topic answers the following questions:

• What is the basic function of a power semiconductor switch in a switching supply?
• What are the most basic properties of a power semiconductor switch?

To view a different topic, go to the Power Supply Tutorial table of contents.
Last topic: Power Supply Capacitors and Inductors
Next topic: Power Semiconductor Switches, Classification

Power Semiconductor Switch Introduction

All ideal switching supplies continually decompose input power at a given voltage and current into “energy packets”. The small energy packets are then continually reassembled into output power at a new desired voltage and current.

The following image illustrates a 2:1 step down converter where each small block could represent an energy packet:

Observe that the output power is equal to that at the input. This property is characteristic of an ideal switching converter. In practical applications there will be some energy loss due to waste heat.

The power semiconductor switches, perform the decomposition and reassembly process, directing the flow of energy from the input, through the inductor and capacitor energy storage components, to the output.

The power semiconductor switches, depending upon the topology and requirements, are either active transistors, thyristors, or passive diode rectifiers. A topology is an arrangement of switches, inductors, and capacitors chosen to achieve a desired input to output conversion ratio.

Ideal Power Semiconductor Switch Properties

The ideal switch has the following properties:

• infinite breakdown voltage,
• when the switch is off, there is zero current through the switch,
• when switch is on, there is zero voltage across the switch,
• the turn-on and turn-off transition times of ideal switches are zero,
• since the either the voltage or the current is always zero in an ideal switch, the instantaneous dissipation which is the product of instantaneous voltage and instantaneous current is always zero.

Non-Ideal Power Semiconductor Switch Properties

A well chosen practical switch will approximate an ideal on a first order basis. Even so, the non-ideal properties of practical switches must be evaluated for every design.will have parasitic elements which cause:

• finite breakdown voltage,
• leakage current in the off-state,
• non-zero voltage across the switch in the on-state,
• non-zero turn-on and turn-off transition times,
• since there is some voltage across the switch in the on-state, and the transition times are non-zero, there is non-zero dissipation which must be managed.

Next Topic

The next tutorial installment is: Power Semiconductor Switches, Classification. This next topic will answer the following questions:

• What are the main power semiconductor switch classifications?
• What are the important properties of the main classifications?

If you need assistance with power electronics design, call or email us today for help with your requirements. You can also go to our power electronics consultant website for more information about our services for business clients. Thank you for reading this tutorial article entitled “Power Semiconductor Switches | Ideal Switches”

Next topic: Power Semiconductor Switches, Classification
Back to Power Supply Tutorial table of contents.

The post Tutorial: Power Semiconductor Switches | Ideal Switches appeared first on POWER ELECTRONICS CONSULTANT.