Power Diode Recovered Charge(Qr) & Reverse Recovery Time(trr) || Diode Switching Loss Explanation

Summary

In this educational lecture, the presenter delves into the concept of stored charge and reverse recovery in diodes. They explain the functioning of a diode under forward and reverse bias, highlighting the role of minority charge carriers and junction capacitance. The lecture further discusses the process of removing stored charges and the significance of reverse recovery time (tRR). It explores power loss in diodes due to stored charges and reverse recovery, and contrasts different types of diodes, such as the IN4007 and SBD, in terms of their reverse recovery characteristics.

Takeaways

• 🔌 Diodes function by allowing current flow when forward-biased and blocking current when reverse-biased.
• 🌊 The depletion region in a diode expands when reverse-biased, which helps to block current flow.
• ⚡ The process of removing stored charges in a diode's junction capacitance is crucial for its operation.
• 🕒 Reverse recovery time (tRR) is the time it takes for a diode to remove all stored charges and become capable of blocking reverse voltage.
• 📉 The waveform of voltage and current across a diode can illustrate the diode's behavior during forward and reverse bias conditions.
• 🔋 The stored charge in the junction capacitance affects the diode's ability to block reverse voltage, which is significant for its performance.
• 💡 The minority charge carriers' diffusion from the P-region to the N-region and vice versa is key to the diode's conduction.
• 🔗 The slope of the current during the diode's operation influences the diode's charge and discharge dynamics.
• 🛑 The removal of stored charges is achieved by applying a reverse voltage, which initiates the reverse recovery process.
• 📚 Different types of diodes, such as Schottky or standard silicon diodes, have varying reverse recovery times and stored charge characteristics.

Q & A

What is the main topic of the lecture?

The main topic of the lecture is the stored charge and reverse recovery in diodes, including power loss due to stored charges and the concept of reverse recovery time (t_rr) in diodes.

What happens when a diode is forward biased?

When a diode is forward biased, the depletion region reduces, allowing current to flow through it due to the diffusion of minority charge carriers from the P region to the N region and vice versa.

How does the depletion region change when a diode is reverse biased?

When a diode is reverse biased, the depletion region spreads towards the PN junction, and the minority carrier charges are pulled out, preventing current flow until the diode is capable of blocking the reverse voltage.

What is meant by stored charge in a diode?

Stored charge in a diode refers to the minority charge carriers that accumulate at the junction capacitance when the diode is forward biased.

What is reverse recovery?

Reverse recovery is the process of removing the stored charges from the junction capacitance when the diode transitions from forward bias to reverse bias.

How is the reverse recovery time (t_rr) defined?

The reverse recovery time (t_rr) is the time required for a diode to remove all stored charges and block the applied reverse voltage after transitioning from forward bias to reverse bias.

What is the significance of the current slope during reverse recovery?

The current slope during reverse recovery is significant as it determines the rate at which the stored charges are removed and the diode's ability to block the reverse voltage.

What are the power losses in a diode during reverse recovery?

Power losses in a diode during reverse recovery include conduction losses when the diode is forward biased and switching losses when the diode transitions to reverse bias.

Why is it important to know the reverse recovery time for diodes?

Knowing the reverse recovery time is important because it affects the efficiency and performance of circuits, especially in applications involving fast switching.

How do different types of diodes compare in terms of reverse recovery time?

Different types of diodes have different reverse recovery times. For example, Schottky diodes typically have faster reverse recovery times compared to silicon diodes, which is an important consideration in high-speed switching applications.

Outlines

00:00

🔬 Introduction to Stored Charge and Diode Operations

This paragraph introduces the topic of stored charge and diode behavior, particularly focusing on reverse recovery and power loss due to stored charges. The speaker begins by inviting viewers to subscribe to the channel and engage with the content. The main discussion revolves around the functioning of a diode, explaining how a forward bias leads to the diffusion of minority charge carriers and the resulting current flow. The concept of junction capacitance charging and the role of the depletion region in a PN junction diode are also covered. The paragraph sets the stage for a deeper dive into the technical aspects of diode operation and the challenges associated with stored charges and reverse recovery.

05:03

🔋 Reverse Bias and Diode Recovery Process

The second paragraph delves into the process of reverse biasing a diode and the subsequent removal of stored charges. It describes how applying a reverse voltage leads to the depletion of minority charge carriers and the expansion of the depletion region. The speaker uses a waveform diagram to illustrate the voltage and current changes over time, highlighting the intervals during which the diode transitions from forward to reverse bias. The concept of reverse recovery time (tRR) is introduced, explaining the time it takes for a diode to remove all stored charges and become capable of blocking reverse voltage. The paragraph also touches on the impact of the slope of the current on the diode's behavior, providing a technical explanation of the recovery process.

10:07

⏱ Understanding Reverse Recovery Time and Diode Types

The final paragraph discusses the reverse recovery time (TRR) in detail, emphasizing its significance in determining the diode's ability to block negative voltage after charge removal. The speaker contrasts different types of diodes, such as the IN4001 and Schottky diodes, highlighting their respective TRR characteristics. The paragraph concludes with a summary of the lecture's key points and a thank you to the viewers for their attention. It reinforces the importance of understanding the technical specifications of diodes for applications involving rapid switching and voltage blocking.

Keywords

💡Stored Charge

Stored charge refers to the accumulation of charge carriers within the junction capacitance of a diode. In the context of the video, when a diode is forward-biased, minority charge carriers diffuse across the PN junction, leading to the storage of these charges. This stored charge plays a crucial role in the diode's operation and its ability to conduct current. The video discusses the process of removing these stored charges during reverse recovery, which is essential for the diode's proper functioning.

💡Diode

A diode is a two-terminal electronic component that allows current to flow primarily in one direction. It consists of a PN junction, which is a boundary between a P-type semiconductor and an N-type semiconductor. The video focuses on the behavior of diodes under different biasing conditions, such as forward and reverse bias, and the impact of stored charges on their performance.

💡Reverse Recovery

Reverse recovery is the process of removing stored charges from the junction capacitance of a diode when it transitions from forward bias to reverse bias. This process is critical for the diode's ability to block reverse voltage and is characterized by the reverse recovery time (tRR). The video explains that during reverse recovery, a negative current is used to extract minority carriers, which is illustrated through the waveforms and charge distribution diagrams presented.

💡Power Loss

Power loss in a diode refers to the energy dissipated as heat when current flows through the diode, particularly during the switching process. The video discusses two types of losses: conduction loss, which occurs when the diode is forward-biased and current flows, and switching loss, which happens during the transition from forward to reverse bias. Understanding power loss is important for designing efficient electronic circuits.

💡tRR (Reverse Recovery Time)

tRR, or reverse recovery time, is the time it takes for a diode to remove all stored charges and become capable of blocking reverse voltage after being switched off. This parameter is crucial for high-speed switching applications where rapid diode recovery is necessary. The video mentions that different types of diodes have different tRR values, which can affect their performance in specific applications.

💡QR (Recovery Charge)

QR, or recovery charge, is the amount of charge that must be removed from the diode's junction capacitance during reverse recovery. It is represented by the area under the current waveform during the reverse recovery period. The video uses QR as an example to illustrate the relationship between the stored charge and the diode's reverse recovery characteristics.

💡PN Junction

The PN junction is the interface between P-type and N-type semiconductor materials in a diode. It is the fundamental structure that allows the diode to exhibit its unidirectional conductivity. The video explains how the depletion region of the PN junction changes with forward and reverse bias, affecting the diode's behavior and the storage of charge carriers.

💡Depletion Region

The depletion region is the area near the PN junction where the majority of charge carriers have been depleted, leaving behind an electric field that opposes further flow of current. The video describes how the width of the depletion region changes with biasing conditions, affecting the diode's ability to conduct or block current.

💡Forward Bias

Forward bias is a condition where a diode is connected in such a way that its P-type side is connected to the positive terminal of a voltage source, and its N-type side is connected to the negative terminal. This biasing condition allows current to flow easily through the diode. The video discusses how forward bias leads to the diffusion of minority charge carriers and the storage of charge in the junction capacitance.

💡Reverse Bias

Reverse bias is the opposite of forward bias, where the P-type side of a diode is connected to the negative terminal of a voltage source, and the N-type side is connected to the positive terminal. This biasing condition causes the depletion region to widen, making it difficult for current to flow. The video explains the process of removing stored charges when a diode transitions from forward to reverse bias.

💡Diode Types

The video mentions different types of diodes, such as the IN4007 and SBD (Schottky Barrier Diode), and discusses their specific reverse recovery characteristics. Different diode types have different materials and structures, which affect their performance parameters like reverse recovery time and stored charge. Understanding these differences is important for selecting the appropriate diode for a given application.

Highlights

Introduction to stored charge and diode reverse recovery

Explanation of power loss in diodes due to stored charges and reverse recovery

Definition of tRR (reverse recovery time) and QR (reverse recovery charge)

Types of diodes and their reverse recovery times

How to subscribe and receive notifications for upcoming lectures

Basic functioning of a diode under forward bias

The role of minority charge carriers in diode operation

How the depletion region changes under reverse bias

Process of removing stored charges in the junction capacitance

Waveform analysis of voltage and current across a diode

Minority charge distribution during reverse recovery

Interval analysis of diode operation from on to off state

Impact of current slope on diode performance

Explanation of how depletion region width increases after removing stored charges

Blocking of reverse voltage by diodes after charge removal

Calculation of power loss in diodes during conduction and switching

Detailed discussion on reverse recovery time (TRR) and its significance

Comparison of reverse recovery times for different types of diodes

Conclusion and appreciation for watching the lecture

Transcripts

hello friends hope you are doing well in

today's lecture I'm going to talk about

the stored charge and diode and diode

reverse recovery okay power loss in

diode due to store charts and reverse

recovery and then what is t RR win diode

what is QR n diode types of diode and

their reverse recovery time so okay so

before I start my lecture I would

request you if you haven't subscribe my

channel please subscribe it and press

the bell icon so that you get

notifications of all my upcoming lecture

please like share with your friends and

family members okay watch the video till

the end so that you get all the lecture

notes ok now let's talk about the diode

store charts removal and reverse

recovery ok

I'm not going much more in detail how

diode is functioning but let's talk

about a bit a little bit how the hood is

working now so if you apply a positive

voltage to P reason and negative voltage

to n reason okay so what happens is if

you apply positive voltage to P reason

and negative voltage to n vision there

is a magnetic diffusion of a minority

carry a charge carrier minority charge

carrier from P reason to and reason and

indecent to P reason okay

minority it's the charge carrier

diffuses from P reason to and isn't due

to that the junction

capacitance charges and because of that

the current start flowing through the

through it okay so if you apply a

forward bias diode in a foul road for

advice

okay so depletion region of PN Junction

diode a diode reduces because of that

current start flowing through it okay

okay all right so if you bias a diode in

a reverse fashion okay how would you

guys it if you apply negative voltage to

be terminal of PN Junction and positive

voltage to end a zone of PN Junction

diode becomes a reverse biased reverse

bias condition in that particular

condition the depletion region spreads

towards towards PN and reason and the

minority carrier charges now pulls out

okay

so that is how a diode is working so now

let's talk about the store charts in

removal and reverse recovery means how

you how you remove the stored charges in

junction capacitance and what is reverse

recovery

okay let's talk a bit about that so now

okay

I have drawn a drawn a waveform this is

VD voltage across diode okay over a

period of time this is ID current across

the diode over a period of time okay and

this one I have drawn here minority

charge distribution during reverse

recovery in diode okay so let's talk

about now okay during interval or during

interval T equals to zero here

to t equals to t0 here okay during

interval T equals to 0 to T equals to t0

diode is on condition and there is some

current current flowing through it okay

so that is ID

okay so diode is there is some voltage

across the diode and some current

flowing through it so voltage across

diode is VD on and some current across

the diode is flowing through it is ID on

right okay means diode is in forward

bias condition now

during interval t equals 2t 0 to t

equals to t1 okay t equals 2t 0 to t

equals to t1 you have applied the

reverse voltage across the PN Junction

and diode is in reverse bias condition

so now in diode is in reverse bias

condition so what happens when the diode

is in reverse bias condition means we

start removing minority charges with a

negative current okay okay so we start

removing negative charges from negative

current so you can see here there is

some negative current flowing through

the diode okay now what happens during

interval of T equals 2 T 1 2 T equals 2

T 2 okay during this interval T equals 2

T 1 2 T equals 2 T 2 okay in this

interval a diode is off and if we

removed the enough charge okay and that

point of time voltage across depletion

region start decreasing and go negative

okay at that point of time voltage

across depletion region okay start

decreasing and go negative

okay during t equals to this point of

time okay now let's have a look off

minority charge distribution how it is

functioning when diode is in forward

bias let's say T equals 2t 0 time

Junction capacitance fully charged okay

there is chards concept a concentration

profile over here the junction minority

charges are minority charge carriers

stored in a junction capacitance over T

equals to zero

during the period of T equals 2t one

start removing some charges from you

start pulling out some charges from the

from Junction capacitance okay over P

and n region so now here the now here

you have less charge stored in in the

junction capacitance okay all right

nothing one more thing

the there is a some current slope okay

okay this is some slope current slope

right that the slope determines the

diffusion did and charge and the current

okay so at the point of 2 T 2 you have

reduced some more charges you have

reduced enough charges you have reduced

enough charges and that point of time

voltage across depletion region start

decreasing and go negative so okay

during two teeth okay during this period

t three okay during this period t three

you removed all stored charge in

Junction capacitance right so let's say

here here okay let's say here let's say

here earlier your depletion width reason

width is that much only okay that much

only now once you removed all charge

stored in Junction capacitance okay so

your depletion region

width increases earlier it was that much

now it was that much because you removed

all stool charts from the new Junction

capacitance so you remove all minority

carrier charges from your Junction

capacitance so the depletion region

width increases because of that diode is

now able to block the reverse voltage

okay

okay diode is now able to block the

reverse voltage okay here beauty of -

negative voltage okay and there is no

current flowing through it so alright

hope you understood that much and now

let's talk about much more and this

interval I've already explained during

this now let's talk about loss in power

loss in diode what is power loss P

equals to B into y at time T equals 2 T

0 - 2 equals 2t to zero here it is so

nice conduction loss at T equals to G T

0 and T equals to t4 you have switching

losses right so now what is a reverse

recovery time time required to diode to

remove all Stuart charts and block the

apply negative voltage okay this one is

TR from T equals to 0 to P equals to 2

for that much time required diode to

remove all its two charges that time is

called reverse recovery time now what is

recovered charge negative diode current

area during reverse recovery let's say I

will overlook here diode stored charge

okay so this one is a recovered charges

area okay let's example I n400 say one

the TR are not specified then FASTA

comedy diode the example is I n for one

for it it's TR r equals two now

a Schottky diode let's say SB 180 and no

recovered charts okay so my question is

now while does I even four zero zero

seven and SB 1 at T does not have it TRR

the reverse recovery time okay okay

thank you watching this lecture hope you

enjoyed the lecture I wish you a very

happy learning

thank you so much