DC boost converter max power ?

[bianchi77]

Everyone,

I've been experimenting DC boost converter,
How much maximum power can I get from this circuit ?

I got output 221.8V and input 12V already...

Does it depend on my inductor ,output diode and my switching FET rating ?

Output diode is 3A 1N5822 and FET = IRFS730 5.5A 400V L = 130uH ...

Cheers

[budm]

Re: DC boost converter max power ?

https://cdn.badcaps-static.com/pdfs/...5e5724b92b.pdf
You are missing lots of info, it is not that simple.
BTW, what circuit?
Should look up 'how to design DC-DC boost converter'.

[bianchi77]

Re: DC boost converter max power ?

ok thanks, it's DC booster 12V to 220V topology, simple PWM and resistor divider feedback...
I've read that TI info, it depends on its chip...mine is a simple astable multivibrator PWM
Doing experiment with 2A 120uH now....
I haven't got any bulb yet for a small test but I will....
It doesn't have to be perfect so if it does the job...all good...

[budm]

Re: DC boost converter max power ?

If you read 2 and on up, you will see that the IC is selected based on what the parts you will be using, I.E. the spec of the inductor.
if the IC with integrated power Power MOSFET is being used then you have to make sure it can handle the required current and Voltage, it is still the same concept, all the parts have to be consideration of the circuit design.

2:Calculate the Maximum Switch Current
The first step to calculate the switch current is to determine the duty cycle, D, for the minimum input
voltage. The minimum input voltage is used because this leads to the maximum switch current.
(1)
VIN(min) = minimum input voltage
VOUT = desired output voltage
η = efficiency of the converter, e.g. estimated 80%
The efficiency is added to the duty cycle calculation, because the converter has to deliver also the energy
dissipated. This calculation gives a more realistic duty cycle than just the equation without the efficiency
factor.
Either an estimated factor, e.g. 80% (which is not unrealistic for a boost converter worst case efficiency),
can be used or see the Typical Characteristics section of the selected converter's data sheet
( Reference 3 and 4).
The next step to calculate the maximum switch current is to determine the inductor ripple current. In the
converters data sheet normally a specific inductor or a range of inductors is named to use with the IC. So
either use the recommended inductor value to calculate the ripple current, an inductor value in the middle
of the recommended range or, if none is given in the data sheet, the one calculated in the Inductor
Selection section of this application note.
(2)
VIN(min) = minimum input voltage
D = duty cycle calculated in Equation 1
fS = minimum switching frequency of the converter
L = selected inductor value
Now it has to be determined if the selected IC can deliver the maximum output current.
(3)
ILIM(min) = minimum value of the current limit of the integrated switch (given in the data sheet)
ΔIL = inductor ripple current calculated in Equation 2
D = duty cycle calculated in Equation 1
If the calculated value for the maximum output current of the selected IC, IMAXOUT, is below the systems
required maximum output current, another IC with a higher switch current limit has to be used.
Only if the calculate value for IMAXOUT is just a little smaller than the needed one, it is possible to use the
selected IC with an inductor with higher inductance if it is still in the recommended range. A higher
inductance reduces the ripple current and therefore increases the maximum output current with the
selected IC.
If the calculated value is above the maximum output current of the application, the maximum switch
current in the system is calculated:
(4)
ΔIL = inductor ripple current calculated in Equation 2
IOUT(max) = maximum output current necessary in the application
D = duty cycle calculated in Equation 1
This is the peak current, the inductor, the integrated switch(es) and the external diode has to withstand.
3: Inductor Selection
Often data sheets give a range of recommended inductor values. If this is the case, it is recommended to
choose an inductor from this range. The higher the inductor value, the higher is the maximum output
current because of the reduced ripple current.
The lower the inductor value, the smaller is the solution size. Note that the inductor must always have a
higher current rating than the maximum current given in Equation 4 because the current increases with
decreasing inductance.
For parts where no inductor range is given, the following equation is a good estimation for the right
inductor:
(5)
VIN = typical input voltage
VOUT = desired output voltage
fS = minimum switching frequency of the converter
ΔIL = estimated inductor ripple current, see below
The inductor ripple current cannot be calculated with Equation 1 because the inductor is not known. A
good estimation for the inductor ripple current is 20% to 40% of the output current.
(6)
ΔIL = estimated inductor ripple current
IOUT(max) = maximum output current necessary in the application

[budm]

Re: DC boost converter max power ?

BTW, how much current are you trying to get at 220VDC output?

[bianchi77]

Re: DC boost converter max power ?

I don't need much for starting ...0.2A ...up to 1A 220V if possible 220VA later on...

Will I get the same voltage feedback if I put optocoupler on it ?
Currently I'm using a NPN transistor and voltage divider to get the feedback..

[budm]

Re: DC boost converter max power ?

220V at 1A = 220W, that means the input current will be a lot higher 18.33A (3.67A @ 220V 0.2A: 44W) but that will be more because you will not get 100% conversion,so what kind of 12V supply are you using?
You are no building isolated output so no need to use Opto-couple.

[bianchi77]

Re: DC boost converter max power ?

so I need a car battery to supply 12V 18.33A....if I use 12V 7.2A from UPS....
I will get 80% off that battery power on 220V ? 86.4VA *0.8 = 65VA for 12V 7.2A battery ?
I've tested with 9V battery and get 240V but the amperage is too low...
Anyway how much current can I get for 9V battery ?

[budm]

Re: DC boost converter max power ?

The 18.33A if you do do not have any conversion lost which is not going to be the case so you will need supply that can supply more than 18A at full load.
Right now you are just checking the output Voltage with no load, so what are you getting with the load applied and if the output is still regulating with the load connected. You just have have calculate the load resistance based on your current you want draw from the output at the set regulated output Voltage.

[budm]

Re: DC boost converter max power ?

so I need a car battery to supply 12V 18.33A....if I use 12V 7.2A from UPS....
I will get 80% off that battery power on 220V ? 86.4VA *0.8 = 65VA for 12V 7.2A battery ?
I've tested with 9V battery and get 240V but the amperage is too low...
Anyway how much current can I get for 9V battery ?

Some readings.
http://power-topics.blogspot.com/201...for-power.html
https://cdn.badcaps-static.com/pdfs/...a94ba99eb4.pdf

[bianchi77]

Re: DC boost converter max power ?

Ok, I put dummy load RL = 220 ohm and the voltage drop to 8.45V equal to battery voltage...any work around it ?

[budm]

Re: DC boost converter max power ?

If the power supply is actually putting out 220VDC with no load and you are trying to draw 220V/220 Ohms which will be = 1A of current the load is trying to draw from the power supply, that is 220V x 1A = 220W.
So what do you think? Do you really expecting that little power supply is going to be able to supply that much power? Just think how much power the battery will also have to supply. Did you do simple Ohm laws?
BTW, where is the circuit and where did you get it from? I hope you realize that you are trying to build over 200W converter..

[bianchi77]

Re: DC boost converter max power ?

I got it, so I need a powerfull battery if I want to get more power on 220V minus efficiency...
85W 12V battery , probably only get about 60W 220V...correct me ?

[budm]

Re: DC boost converter max power ?

You need a powerful circuit which you have not show us where you got it from yet. Look up 200W DC-DC converter to get some idea how big they are. Did you read the many links I provided to see if the inductor and all other parts you are trying to use will be OK per calculation?
Is the circuit made to deliver the needed power? You are just going in circle and you are not going to get any where with it until you understand what you are trying to do.
With your little knowledge do you really think you can make such device without understanding basic concept?

This statement alone "Ok, I put dummy load RL = 220 ohm and the voltage drop to 8.45V equal to battery voltage...any work around it ?" makes me wonder. Work around? really?

[Khron]

Re: DC boost converter max power ?

budm, i sincerely admire your patience and good will. That being said, after what went down in the "SATA / PATA power supply" thread at least, it makes everyone wonder.

[budm]

Re: DC boost converter max power ?

Well my patience is running low, if you read a lot of his threads on so many questions it made me wonder if he is learning anything at all such as simple Ohms laws.

[Khron]

Re: DC boost converter max power ?

I know, and i can't blame you...

Nothing wrong with aiming high, but there's that whole thing with "you gotta learn to walk, before you learn to run". Cutting corners in this field isn't much of an option (unless one doesn't mind risking life and limb in the process)

[bianchi77]

Re: DC boost converter max power ?

Here's the circuit, what do I need to make it powerfull ? I follow the principle of inductor doing its job. Don't say 1A...0.1A of 220V is good for my experiment.
Yup I'm learning ohm law, but something practical is more interested to me..doing all math calculation without my hand working on the PCB making me bored.
I keep learning no matter other people call me, it doesn't matter..

Learning is steep and deep but I enjoy it

[bianchi77]

Re: DC boost converter max power ?

I know, and i can't blame you...

Nothing wrong with aiming high, but there's that whole thing with "you gotta learn to walk, before you learn to run". Cutting corners in this field isn't much of an option (unless one doesn't mind risking life and limb in the process)

I'm not cutting corner here...learning and learning...Do I run now ? it's learning to walk now..

[bianchi77]

Re: DC boost converter max power ?

It's a simple astable multivibrator and FET with inductor and resistor voltage divider...I'm not running here but I'm learning here.I don't use any advance PWM chip.I want to know how it works.
on SATA and PATA, the dual transistor is the PWM, that's a cheap and smart idea to make it into production and they are all fixed and running now....made abit modification and tested for 12 hours run non stop, all good....learning and learning...
The price of 2 transistors and 1 power FET will be cheaper than 1 advance PWM chip, profitable for production...