Troubleshooting with spv1040 MPPT

[Zhongxi Li]

Posted on December 09, 2016 at 03:38

Hi,

We designed a battery charger using SPV1040.

• The output voltage is fine;
• however, during the charging process, there is a large fluctuation on the input voltage : 500mV ~ 1V. Ideally. This input voltage should stay close to Vmpp, which is 1V in our case. Since it's fluctuating, the resultant MPPT efficiency is very bad.

The diagram is attached below. Is that because we didn't settle the output current sensor resistors? The datasheet implies that it is only used for over current protection, which is not required by us so we simply grounded the I_plus and I_minus.

Many thanks for your help!

[Andrew Lohmann_2]

Posted on December 21, 2016 at 16:02

I am following your question because I have included a similar part in my design. It is SPV1050, I don't think the problem is difficult the problem is understanding the datasheet and applying it.

[Zhongxi Li]

Posted on January 04, 2017 at 16:41

Hi Andrew, thanks for your reply.

I did some more measurements and find the following:

1. the chip's MPPT function does not need wiring I_PLUS or I_MINUS. If it monitors the output current, it does so internally;

2. perhaps our problem of low MPPT efficiency (~40%) is because we used very small input wattage (~15 mW); increasing the input wattage to 200 mW leads to 70%+ MPPT efficiency. The chip's data sheet uses >0.25 W for specifications, though.