Knowledge not found in 100 books: How to determine the inductance of wide range buck and boost

PowerAnts

Knowledge not found in 100 books: How to determine the inductance of wide range buck and boost [Copy link]

 

There are some posts about BOOST in the forum recently.

How to choose and calculate the inductor in a DC-DC power supply https://en.eeworld.com/bbs/thread-1195945-1-1.html

Why buck_boost should be designed from the lowest input voltage https://en.eeworld.com/bbs/thread-1198862-1-1.html

The book only has the transformation ratio formula, but in applications, the input voltage varies within a certain range, and in some applications, the output is still adjustable. How to determine the inductance? Extending to the buck, what should we do?

There are many conditions for selecting inductors, including minimum loss method, minimum ripple method, minimum volume method, and minimum cost method. What do you need to focus on?

I hope this post can serve as a starting point for netizens.

PowerAnts

Let's talk about the ripple rule first. The book recommends 0.2-0.4. The designer patted his head and decided to use 0.3. It's always right to be moderate! !

Wait, VIN=10~45V, VOUT=48V, then when calculating the inductance, how big should VIN be so that the ripple does not exceed 0.3 in the entire input range? I have heard different opinions, 10V? 45V? 0,5VOUT? 0.5*(45-10)? These "guesses" are all wrong! ! ! !

PowerAnts

Because this is my personal research experience, if not many people pay attention to it, I won't post it all at once.

Let's put it this way. Every time 10 people support it, one item will be unlocked.

cflyswing

Newcomer, keep following

okhxyyo

Like~~ Waiting to see the share

kangkls

If the inductor is not chosen properly, it will explode and burn the subsequent circuit. I once burned several thousand dollars of subsequent equipment.

呜呼哀哉

PowerAnts posted on 2022-4-7 16:33 Let's talk about the ripple rule first. The book recommends 0.2-0.4. The designer patted his head and said, "I'll take 0.3. It's always right to be moderate! ! Slow...

The calculation of the inductance of the BUCK should be done under the minimum input voltage and maximum output current. The duty cycle of the BUCK is the ratio of the output voltage to the input voltage. The switching frequency and D determine the rise time of the inductor current, that is, the peak current. So I think the answer is 10V.

PowerAnts

No one is discussing this here, I have already posted it somewhere else

电子微创意

PowerAnts posted on 2022-4-11 19:06 No one is discussing this here, I have already posted it somewhere else

Nowadays, there are too many people who want to eat fast food, and the habit of chewing slowly to digest food has been neglected.

PowerAnts

L=ton*vin/deltI (1)
deltI=k*Io*vout/vin (2)
ton=D/f (3)
D=(vo-vin)/vo (4)
Substitute (2), (3), (4) into (1) to get
L=(vo-vin)*vin^2/(kfIo*vo^2)
k, f, Io have been determined, what is the relationship between vo and vin, L is the largest?
The condition is vin=2vo/3
OK!
For 10-45V to 48V, use 32V input to calculate the inductance
For 10-20V to 48V, use 20V input to calculate the inductance
For 36-45V to 48V, use 36V input to calculate the inductance

That is to say,

No matter what your input range is, the voltage point closest to 2VO/3 is the best!

No matter what your input range is, the voltage point closest to 2VO/3 is the best!!!!!!!

No matter what your input range is, it is best to use the voltage point closest to 2VO/3!!!!!!!!!!!!!!!!!!
See if it is useless?

Note: An expert pointed out that in "Mastering Switching Power Supplies AZ", the foreign author directly proposed in another way that the condition for the maximum L is D=1/3. In Boost, the two are the same thing.

Therefore: This statement is not found in 100 books. I am a little careless! ! ! I am a little embarrassed (I haven't read a book on switching power supply for 10 years, and I didn't know there was such a book)

Comment: I have always been accustomed to studying the extreme conditions of circuit parameters, striving to achieve calculations that are better than device errors in design work, and I jokingly call it finding the "G" point.

PowerAnts

I am very pleased to have reached the level of foreign authors! However, there is no limit to skills, and I still need to explore

soso

PowerAnts posted on 2022-4-11 19:06 No one is discussing this here, I have already posted it somewhere else

Can I continue after 10 people have unlocked an item?

PowerAnts

soso posted on 2022-4-15 13:53 Can I continue after 10 people have unlocked one item?

One item on the 10th floor has been unlocked in advance!

How many people read the following post?

https://en.eeworld.com/bbs/thread-1199565-1-1.html

There are many experts in the place, and they can give me some suggestions!

The EE community is still too low-level. It is hard for me to see posts that allow for rational discussions and mutual improvement from multiple parties.

soso

PowerAnts posted on 2022-4-15 15:46 One item has been unlocked in advance on the 10th floor! How many people read the following post? http://bbs.eeworld.com ...

Well, let’s slowly gather the relevant discussions.

不亦心

The author of "Mastering Switching Power Supply AZ" passed away last year, leaving behind an unfinished work. "Switching Power Supply Design and Optimization" is an advanced version of AZ, which is quite good and I have read it several times.

The book contains a derivation process, which is similar to Mr. Jiang's derivation.

The relationship between ripple current and duty cycle is derived, and the duty cycle corresponding to the extreme value of ripple current is calculated. The result can be converted into Engineer Jiang's conclusion.

PowerAnts

Bu Yixin published on 2022-4-16 15:09 The author of "Mastering Switching Power Supply AZ" passed away last year, leaving behind an unfinished work. "Switching Power Supply Design and Optimization" is considered an advanced version of AZ, which is not bad...

This guy has changed my prejudice against Indians. The word "Asan" will disappear from my dictionary.

不亦心

Sanjaya Maniktala's posthumous work was compiled and published by his family. AZ is going to add some content, mainly some views on wireless charging and LLC resonant topology.

English version, it's a bit difficult to read, I just read it and share it with netizens who need it

Power Supplies A to Z 3rd _ Maniktala_Rosano_ add on to A-Z 2nd-20210623.zip.002 (7.99 MB, downloads: 34)

2022-4-16 23:36 上传

点击文件名下载附件

Power Supplies A to Z 3rd _ Maniktala_Rosano_ add on to A-Z 2nd-20210623.zip.001 (10 MB, downloads: 38)

2022-4-16 23:36 上传

点击文件名下载附件

呜呼哀哉

Bu Yixin published on 2022-4-16 23:44 Sanjaya Maniktala's posthumous work, compiled and published by his family. AZ is going to add some content, mainly some views on wireless charging and LLC resonant topology...

I have only seen AZ, DCDC which explains it in great detail. There seems to be a Chinese version on design and optimization, which is really in-depth.

UUC

Although I am not engaged in this field and it is difficult to understand it in depth, I still join in the fun and learn.

forest2000

Although I am not engaged in this field and it is difficult to understand it in depth, I still join in the fun and learn.