SPV1040T Not Working as intended.

[Stalin]

Hello, 

I'm trying to use the SPV1040T MPPT IC to boost up the 1.5V I'm getting from the Solar Panel to 3.8V. When I Power ON the MPPT IC its output just follows the Input and i don't see any chances of voltage getting boosted up. Is there anything wrong in the design attached? Please advise. 

For now, I'm using the Lab power supply to power the MPPT IC, the O/P voltage is set to 1.5V, Current limit is set to 100mA. 

Regards

Stalin 

 

 

[AScha.3]

Hi,

from ds:

So connect the ictrl-xx to gnd, and xshut to PV+.

[Stalin]

Thanks for the Suggestion.

I did the Following modifications today and captured the I/P and O/P waveforms.  Can you check if anything still wrong to get the desired output voltage of 3.8V? 

The Measurements are done with No load attached to the output of the MPPT IC.  

 

[AScha.3]

So its working now . good !

Seems it going to "skip mode" , doing some pulses, get much voltage and stops for safety , until it tries again.

To test this, give it some load (resistor to gnd, to get about the target current, you want) + maybe a bigger load cap (470uF or so); you have to try, i dont have this chip. (So i just can tell from my experience with other smps chips.)

+ the diode CR14 should be there.

[Stalin]

I removed the diode, and the scope plots looks little different than before.  I also tried to change the inductor value from 10uH to 33uH (that's the highest I can find quickly) not many improvements other than slight changes in the waveforms. 

FYI - the VIN was probed at the Inductor Pin that connects to the Pin No 3 (LX) of the MPPT IC. 

I'm suspecting if any problem in the Voltage regulation loop. I will try to change the resistor value to match with the STEVAL-ISV006V2 Evaluation board. The Values I used seems much lower than the evaluation board.  

 

 

 

 

[AScha.3]

Sorry, but still in almost same as output -> chip damaged ??

+

output has sharp rising and falling signal = impossible with low impedance caps > 10uF there !

So check, are the caps really there and have contact to gnd (-plane) .

[Stalin]

There is a 10uF CAP on the I/P and O/P.  Should I increase the O/P CAP value further?  

To rule out the I/P = O/P I will change the Chip to a new one tomorrow and probe it. 

 

 

 

 

 

[Stalin]

I changed the O/P CAP from 10uF to 100uF and i don't see the I/P= o/P Problem anymore. the MPPT chip seems to be functional properly in No load, Nominal and Light Loading condition.  Only thing the O/p Voltage is not boosted, the Super CAP charging only up to 1.5V. 

I even tried to increase the O/P CAP up to 500uF, the Results look similar with no changes. 

 

 

 

[AScha.3]

again:

-  pic on scope : really in + out ?? (looks like almost a short in->out ) and IN has higher voltage than OUT = impossible !

- And check with scope directly on 10u caps , + and gnd side , IN and OUT caps. I cannot believe its switching with so much current.

- and try as input a simple AA cell, (1.5V ) , to avoid any strange limiting action from the regulated supply .

[Stalin]

2 Experiments today 

 

I tried with the AA Cell today and the Result is same. MPPT is switching at 100kHz rate but, the Super CAP connected at the output of the MPPT thorough the Current limiting resistor (63.2 ohm) is charging up to 1.5V. Once it reaches 1.5V the Switching Stops. The Switching resumes automatically once the Super CAP is discharged little bit. 

 

I also tried connecting the Solar Panel but, for the indoor lighting there is not enough juice from the Panel to enable the MPPT IC. 

[AScha.3]

So with the 1.5V cell - it should do, as with a panel (giving about 1.5V).

- And check with scope directly on 10u caps , + and gnd side , IN and OUT caps. I cannot believe its switching with so much current.

Did you check ?

If input really (on caps !) has more voltage, than output - replace chip. (This cannot be...)

[Stalin]

Correct. Panel giving about 0.9V nominal. if the light source is moved closer to the Panel it can go up to 1.5V.

The OCV of the Panel itself is 1.75V

about the Scope Plots directly at the I/P and O/P CAP attached here FYR.  

with the Same CAP and Inductor values I will try to replace the MPPT IC once and take one more measurement. 

[Roger SHIVELY]

Hello @Stalin 

 

This post has been escalated to the ST Online Support Team for additional assistance.  We'll contact you directly.

 

Regards,

Roger

ST Support