Boost converter cannot reach the desired output voltage

[sprooch]

Hi,

I am designing an analog boost converter controlled by microcontroller now and I have a problem with the output voltage.

requirements:
Input voltage = 0-15 V
Output voltage = 48 V
Output current = 6.25 A

I am using:
L = 35uH
C = 60uF

When I applied input voltage in the range from 8.5 V - 15 V, I got an ouput of 48 V and 6.25 A by changing the dutycycle ( D )

But when I applied input voltage below 8.5 V, I got below 33 V even I tried a fast dutycycle ( 89% )

I do not know exactly what is happening. I need some help for this....

 

[saturn1bguy]

A schematic would really help here, but I just can't see how you're going to get that kind of output (300W) given your input range of 0-15V! I'm having trouble believing this works at all with such a tiny inductor. And at 5V input you'd have to be supplying over 67A...

Man, are you sure you didn't mean to address the free energy forum?

 

[sprooch]

Yes, it is designed for boosting solar panel output which has power of 300 W.
I attached the circuit in multisim

 

[Ubergeek63]

you do realize that you need a 100A and preferably a 200A FET with better than 2A gate drive for that converter, don't you? And you should be using at least a 12V panel-they put out between 20V and 12V under full sun at full load.

 

[sprooch]

Yes,

I've just realized the FET.
I checked all the components and tried to change them.
but the problem I found is that I could not find the components I chose on the simulation software (multisim).

Do you now another way to simulate the right components? otherwise I have to buy the components first then try them, I think...

 

[MrAl]

Hi there,


When you start to push the limits of a boost converter lots of things come
into play that dont when you are dealing with low power. The inductor
series resistance becomes very important as well as other losses in the
inductor, and transistor 'on' resistance, etc.
Higher power 'boost' supplies are often made with transformer outputs
to boost the output instead of relying on an inductor to do all the work,
but yes a standard boost circuit is 'easier' to make.

 

[sprooch]

I have tried to look for the right components that can handle high power.
I found difficulties on choosing the inductor.

The inductor that is used here is not the usual components. I have to find aprox 200A , 35uH Inductor. How can I solve this problem? Do I have to order a special inductor in this case?

I am really a beginner in this field.

 

[Ubergeek63]

What is your solar panel rating? You should not be using a 6V panel and a 12V panel wants to put out 17V, but you should really be looking at a 24V panel to run a 48V rail in that configuration.

 

[Papabravo]

I have tried to look for the right components that can handle high power.
I found difficulties on choosing the inductor.

The inductor that is used here is not the usual components. I have to find aprox 200A , 35uH Inductor. How can I solve this problem? Do I have to order a special inductor in this case?

I am really a beginner in this field.

At those levels I think you are going to have to make your own inductors. Odds are they won't be at all cheap.

 

[sololf21]

Hi,

I am designing an analog boost converter controlled by microcontroller now and I have a problem with the output voltage.

requirements:
Input voltage = 0-15 V
Output voltage = 48 V
Output current = 6.25 A

I am using:
L = 35uH
C = 60uF

When I applied input voltage in the range from 8.5 V - 15 V, I got an ouput of 48 V and 6.25 A by changing the dutycycle ( D )

But when I applied input voltage below 8.5 V, I got below 33 V even I tried a fast dutycycle ( 89% )

I do not know exactly what is happening. I need some help for this....

hi there,

i'm also doing an fyp similar to urs but my input is 18V, also from a solar panel... possible to share ur findings and how u got the values for ur inductors and other components in ur circuit?

I'm reali desperate for a solution now cos my fyp is due in 3mth and i haven gotten a single component...

thanks in advance.

pls mail to sololf21@hotmail.com