# experimental problem in boost converter

#### mimou

Joined Oct 23, 2023
3
Hello everyone, I have designed a boost converter. The input is from a solar panel providing 8W/6V, with the desired output voltage set to 12V and a load of 20 ohms. I calculated all parameters using literature equations, taking into account the parasitic elements (Fs=20kHz, D=53%), and simulated it using Matlab. However, I encountered a problem in the experimental results; for instance, the output voltage measures only 8V.
I don't know where the problem is, can you help me please.

#### BobTPH

Joined Jun 5, 2013
8,989

#### mimou

Joined Oct 23, 2023
3

#### Ian0

Joined Aug 7, 2020
9,826
The input is from a solar panel providing 8W/6V,
But is the sun shining brightly enough for it to provide 8W? If you get 8V int 20Ω, the odds are you are only getting 3.2W from the panel (after losses)

#### Irving

Joined Jan 30, 2016
3,890
Some component values for L, D, Cout2 would be useful

#### MisterBill2

Joined Jan 23, 2018
18,538
As a switching boost circuit the current from the magnetic storage element is in series with the internal resistance of the photo array. so no, it will not deliver as desired. (the real world is cruel that way)

#### pwrtrnx

Joined Feb 1, 2024
20
you need to assign values - e.g. C3 = 1000uF, L1 = 1mH, C2 = 220uF, RC1 = 22 ohms

pwn freq = 50kHz, Don = 20% say

for starters.

#### Irving

Joined Jan 30, 2016
3,890
What's ESR of C2, R of L1, actual diode used?

How did you get to 1mH for L1?

#### pwrtrnx

Joined Feb 1, 2024
20
easy starting points, ESR of components not critical at this stage - but do provide some damping, typ figures would be 0.1 ohm for the L and 0.2 ohm for the Caps, Rds-on for the fet should be 0.05 ohm

#### pwrtrnx

Joined Feb 1, 2024
20
The posters main problem appears to be that the energy source is not stiff enough to run the sim properly - a battery with a resistor is a very good sim for a fully irradiated solar panel. Vbatt = V open ckt, R = Vopen ckt / I short ckt

#### Ian0

Joined Aug 7, 2020
9,826
The posters main problem appears to be that the energy source is not stiff enough to run the sim properly - a battery with a resistor is a very good sim for a fully irradiated solar panel. Vbatt = V open ckt, R = Vopen ckt / I short ckt
That's what I thought.
An even better simulation is a current source with a load of diodes in series across it.

#### mimou

Joined Oct 23, 2023
3
Thank you so much for your responses,
for ESRs I use the values from the datasheets (rl=0.1ohms, rc=0.08ohms, and ron=0.05ohms). The simulation has been done, but the issue lies in the experimental results.

#### Irving

Joined Jan 30, 2016
3,890
The main issue I see is that, as was said above, the performance of the boost converter is highly dependent on the impedance of the source, which will depend on the level of illumination. Here is an LTSpice simulation plotting output voltage against source series resistance:

#### MisterBill2

Joined Jan 23, 2018
18,538
At least some of those switcher supplies use a fast diode to supply the low impedance for when the inductor is delivering current. The diode is just upstream of the inductor,and is forward biased as that end of the inductor becomes negative relative to ythe other end.

#### pwrtrnx

Joined Feb 1, 2024
20
@mimou the issue lies in the capability of the power source to supply enough power