Voltage Booster doesn't work

Thread Starter

Dan Aronin 1

Joined Mar 10, 2019
6
Hi I'm trying to build a circuit that will multiply the input voltage by a factor of 5.

Here is what I came up with:


When I use a PWM signal of 0.5 ON, the output is about double the input so it works fine, but when I change to 0.8 PWM ON, the output doesn't change much (increased by 0.2V).

Any of you have suggestions?
 

DickCappels

Joined Aug 21, 2008
5,950
If you don't already have it, add something like a resistor to limit the base current. This probably won't fix your problem with limited voltage range but it might save you grief from complications.

Also, make sure the DC resistance of your inductor is much lower than your load.
 

Thread Starter

Dan Aronin 1

Joined Mar 10, 2019
6
If you don't already have it, add something like a resistor to limit the base current. This probably won't fix your problem with limited voltage range but it might save you grief from complications.

Also, make sure the DC resistance of your inductor is much lower than your load.
There is a base current limit resistor of 470 ohm (not in the diagram)
DCR = 20 ohm
 

DickCappels

Joined Aug 21, 2008
5,950
470 millihenry? I missed that the first schematic showed 100 mH.

Most likely your inductance and resistance are too high.

For a frequency of tens of kilohertz being well below 100 microhenries is common for many applications.
 

Thread Starter

Dan Aronin 1

Joined Mar 10, 2019
6
470 millihenry? I missed that the first schematic showed 100 mH.

Most likely your inductance and resistance are too high.

For a frequency of tens of kilohertz being well below 100 microhenries is common for many applications.
Can you please show a formula for that so I can better understand?
 
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