PRESENTATION

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• Zaitoon BSSE02163053• Abdul malik BSSE02163119• Asad malik ali BSSE02163129• Ahmer joyia BSSE02163130• Basharat ali BSSE02163107• Muhammad Imran BSSE02163063

CONTENTS

fast recovery diode Explanation of fast recovery diode Applications PFC ULTRAFAST RECOVERY DIODE DC TO DC CONVERTER USES

FAST RECOVERY DIODE

Statement :o A semiconductor device with two terminals, typically allowing the flow of

current in one direction only.Quick recovery timeo Fast recovery diode is a diode which has a quick recovery time.Explanation oWhat a quick recovery time is will be explained below

COMMON APPLICATION

One of the most common applications for a diode is to rectify 60Hz sine waves.

This is the frequency of normal AC power lines in the United States.

The diode rectifies this current so that it can be changed from AC current to DC current, since most electronic devices work off of DC power.

So the diode rectifies this 60Hz AC sine waves so that it can converted into DC. 60Hz is a very low frequency.

Most standard conventional diodes are designed so that they give their best performance at relatively low frequencies.

When a diode is dealing with AC signals, such as rectifying them, a certain finite amount of time is required for a diode to recover from one signal to the next.AC signals come nonstop at the diode.

As you can see in the illustration, the diode is battered with AC signals coming at it. Most diodes can handle low frequency signals because since the time periods of each cycle is not very long, they aren't very fast. This is why in low-frequency applications, the recovery time of a diode is not particularly significate . Time period is inversely proportional to the frequency, according to the formula, T= 1/f.

However, the greater the frequency of the signal, the shorter the time period of each cycle. The shorter the time period, the less time the diode has to recover from each cycle. At very high frequencies, this can become a problem, since most diodes cannot recover quickly enough from each cycle. This happens in high-frequency applications, such as in television fly back circuits. In cases like these, the recovery time can become very crucial.

This is because the diode must respond to very short-duration spikes with a very brief rest period between adjacent spikes. An ordinary diode could cause erratic or incorrect operation of the circuit. For better and more reliable performance in high-frequency circuits, a special-purpose diode called a fast recovery diode is used.

Below shows the different in recovery time between a fast recovery diode and a standard diode:

APPLICATION OF FAST RECOVERY DIODE

PFC (POWER FACTOR CORRECTION OR POWER FACTOR CONTROLLER)

ULTRA FAST RECOVERY DIODE

DC TO DC CONVERTER

1 PFC (power factor correction or power factor controller)

DEFINITION

PFC(power factor correction is also know as power factor controller)

It is a measure of how efficiently electrical power is converted into useful work output. Means who much ac is converted into dc efficiently.

There are two types of PFC, Active PFC and Passive PFC. All of our power supplies are either Active PFC Power Supplies or Passive PFC Power Supplies.

WORKING OF PFC

Now we will discuss that how PFC works in power supplies. Power factor correction is the term given to a technology that has been used

since the turn of the 20th century to restore the power factor to as close to unity as is economically viable.

This is basically the capacitors to the electrical network which compensate for the reactive power demand of the inductive load and thus reduce the burden on the supply. There should be no effect on the operation of the equipment.

To reduces the loss of electrical bill the Pfc is used in the foam of capacitors.

Capacitors contained in most power factor correction equipment draw current that leads the voltage, thus producing a leading power factor.

If capacitors are connected to a circuit that operates at a nominally lagging power factor, the extent that the circuit lags is reduced proportionately .

There are many ways that this is metered but the net result is that in order to reduce wasted energy in the distribution system, the consumer is encouraged to apply power factor correction

BENIFITS TO APPLY PFC

Here we discuss some of pfc useful benifits for applying pfc 1. Environmental benefit2. Reduction of electricity bills3. Reduction of voltage drop in long cables.

2 ULTRA FAST RECOVERY DIODE

Ultrafast rectifiers are designed in order to have very low forward voltage with an ultrafast reverse recovery. This makes ultrafast rectifier diodes very efficient for secondary output rectifications in high frequency switched mode power supplies.

Ultrafast rectifiers can directly reduce switching loss and improve overall power efficiency due to a good combination between reverse recovery time and forward voltage.

TYPES OF ULTRAFAST RECTIFIERS

There are many different kinds of ultrafast rectifiers and at Future Electronics we stock many of the most common types categorized by maximum average rectified current, maximum reverse voltage, maximum reverse recovery time, forward voltage, packaging type and maximum reverse current

The most common sizes for maximum average rectified current are 1 A, 2 A, 3 A, 8 A and 30 A. We also carry ultrafast rectifiers with maximum average rectified current as high as 365 A.

Forward voltage can range from 550 mV to 2.7 kV, with the most common ultrafast rectifier semiconductor chips having a forward voltage of 1.1 V, 1.25 V or 1.3 V.

ULTRAFAST RECTIFIERS FROM FUTURE ELECTRONICS

Future Electronics has a full selection of ultrafast rectifier chips from several manufacturers that can be used when your circuit requires an ultrafast recovery diode or ultrafast bridge rectifier. Simply choose from the ultrafast rectifier technical attributes below and your search results will quickly be narrowed to match your specific ultrafast rectifier application needs.

APPLICATIONS FOR ULTRAFAST RECTIFIERS:

Ultrafast Rectifiers are made for negative switching power supplies, as free wheeling diodes (such as in motor applications) and for use in inverters. They can also be found in military and other high reliability applications. Other regular applications include desktop personal computers, laptop and printer AC adaptors, DVD AC/DC power supplies, monitors, televisions and games units.

Choosing the Right Ultrafast Rectifier:

When you are looking for the right ultrafast rectifiers, with the FutureElectronics.com parametric search, you can filter the results by various attributes: by Maximum Average Rectified Current (250 mA, 1A, 3A, 8 A,…), Maximum Reverse Current (500 nA, 5 uA, 10 uA, 50 uA,…) and Forward Voltage (550 mV to 2.7 kV) to name a few.

You will be able to find the right semiconductor chip from several manufacturers when you require an ultrafast recovery diode or ultrafast bridge rectifier for any of your circuits.

3 DC TO DC CONVERTER

A DC-to-DC converter is an electronic circuit or electromechanical device that converts a source of direct current from one voltage  level to another.

It is a type of electric power converter. Power levels range from very low small batteries to very high high-voltage power transmission

ELECTRONIC CONVERSION

Switched-mode DC-to-DC converters convert one DC voltage level to another which may be higher or lower, by storing the input energy temporarily and then releasing that energy to the output at a different voltage.

In this method voltage can be increase and decrease. Switching conversion is more power efficient (often 75% to

98%) than linear voltage regulation, which dissipates unwanted power as heat.

CIRCUIT FOR CONVERTING DC TO DC

IMPORTANT IMPROVEMENT

 Another important improvement in DC-DC converters is replacing the flywheel diode by synchronous rectification

using a power FET, whose "on resistance" is much lower, reducing switching losses.

Before the wide availability of power semiconductors, low-power DC-to-DC synchronous converters consisted of an electro-mechanical vibrator.

Vibrator followed by a voltage step-up transformer feeding a vacuum tube or semiconductor rectifier, or synchronous rectifier contacts on the vibrator

USES

DC to DC converters are used in portable electronic devices such as cellular phones and laptop computers which are supplied with power from batteries primarily.

DC to DC converters developed to maximize the energy harvest for photovoltaic systems and for wind turbines are called power optimizers.

Some exceptions include high-efficiency LED power sources which are a kind of DC to DC converter that regulates the current through the LEDs, and simple charge pumps which double or triple the output voltage.

THANK YOU THE END