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CCS/TIDA-00120: PMP7605

Part Number: TIDA-00120

Tool/software: Code Composer Studio

Hi,

I am trying to make a MPPT using the reference design of TI MPPT PMP7605 and using the same MPPT code provided by TI.

Regarding the issue, I have connected the MPPT with a power supply on the Panel side to provide voltage to MPPT.  No load is connected and no battery is connected.

When I am providing voltage to the MPPT near 8V it takes 200mA current and settled down to 0 mA within a second but as I increase the voltage above 9V it takes a continuous 200mA current and one of the high side MOSFET (Q3) starts heating badly.  

I have checked all the components and replaced MOSFETs and other ICs but still MOSFET Q3 is heating badly. 

Can the 10uH inductor (L1,L2)  be the reason for this ? 

Can anyone please help me on this? 

Best regards,

Nikhil

  • Hello Nikhil,
    I have a suspicion, but I need to look further into this.
    Looking at the Documentation, it specifies the Input Voltage Range as 15VDC - 44VDC, so you are below that.

    While waiting on that, can you provide me the following information:
    How and where did you measure the current?
    Are you using the exact same components as in the TI-Design?
    Are the Fets soldered correctly and every Pin is connected?

    Thank you, kind regards,
    Marion
  • Hi Marion,

    Thank you so much for replying to my post.

    Well, I am using a DC supply instead of a panel to simulate the circuit.

    When the voltage reaches the 8V -9V level it takes a continuous current of 200mA-300mA causing the MOSFET Q3 heat. On the PowerSupply display, it shows the value of current(A) being taken at that instant.

    Yes, I am using the same components as in the TI design except a Gen. purpose diode but it is of the same rating as in the TI board.

    1. One of the problem I found yesterday is of the voltage level at the gate of  Q3 and Q4 MOSFETs. Below is the waveform depicting the same:

    Here the Green waveform is of Q3 and yellow of Q4. We are getting high voltage at Q3 mosfet (which might be the cause of heating).

    In, TI test reports these MOSFETs have the same voltage level.

    I have replaced MOSFETs and again checked the board but didn't find any shorting or faulty component. Also, soldering of all components have been checked yet I am unable to stop the heating at Q3 mosfet.

    MPPT is working but before reaching to that voltage, severe heating is burning the MOSFET.

    2. Also, I have connected the Battery with the MPPT and placed an ammeter between them , keeping the Panel supply around 7-8V . There was a current of 800mA from Battery side towards the MPPT ( Ammeter is showing  a negative 800mA) in a toggle manner.

    Please let me know if I am missing something.

    Thanks and best regards,

    Nikhil

  • Hi Nikhil,

    As Marion said, you are operating the circuit outside its operating range. I am surprised that the circuit is switching - there is supposed to be a check in the code to see if the voltage levels are within range before starting switching. Please check and add this if not present in code. Ideally, the battery voltage should be above 9V and panel voltage should be about 0.5 V above the battery voltage before switching should commence. If not present in the code, please add.

    I see that the drive waveforms are not as expected. They should be complementary (that is, high side switch drive should be low when low side switch drive is high). This may be because of the low input voltage, and the controller may be turning on and off intermittently and not able to stabilize. BTW: You are measuring the high side MOSFET gate to circuit ground. That is why you see high voltage. You should use an isolated probe to measure directly across the gate and source of the upper FET to see the actual drive signal.

    Regards,

    Salil