TPS40210: Boost Converter Not taking Load current

Hi Psasad,
could you please share the schematic and layout? maybe we can find potential risk.

       

Images of schematic and Layout attached please suggest

Hi jasper have you got all the attachments ? hope everything is visible.

Hi Prasad,

What is your load, in amperes, resistance or power level? Could you monitor the MOSFET Vgs, and zoom out to show 1ms range, and zoom out to show a few cycles?

Thanks,
Youhao Xi, Applications Engineering

Thanks. Can you answer the other questions?

with a small load Vgs

without load VGS

pulse duration with load.

pulse duration without any load

Thank you but these waveforms do not reveal much. Can you monitor IC GDRV and ISNS pin voltages along with the MOSFET's Vgs? I am afraid the ISNS is not the real switch current but pulled up by the GDRV through some PCB debris. Please double check you MOSFET source and gate soldering and clean the PCB to avoid any unexpected signal path.

Thanks,
Youhao

Thank you youhao,
thanks for the suggestion..... did you find any fault in the design values ? The switching freq is 600K hope it is not too high for the IC. i was not even able to draw 50mA of current at load with 12V output

Current sense is there to limit the current below certain value right ? when i am drawing such small current what is the functionality of current sense.

Hi Prasad,

You schematic is very blurred on my computer. Anyway, you may place a large cap (say 1uF) on the position of C12, and gradually apply your input voltage (slow rising up) and see if you can establish the output regulation with loading.

If it works, then your loop has problem and we can work from there. Let me know what you see by add the cap.

Thanks,
Youhao

Hope this image is visible to you . I have tested the boost converter for Line regulation it is as expected giving 12V Vout  for Vin ranging from 5.5V to 11V   the problem is there when we draw load current.

Hi Prasad,

So far the info is not enough. CS is used by the PWM comparator to determine the duty cycle. I would like to see your CS signal waveform and see if there any other clue.

Thanks,
Youhao

Hi Prasad,

Sorry for the delay. I was out of office. I did not see any obvious problem in your schematic, and the 600K is high but it should not cause the problem of unable to deliver 50mA load current.

I studied your layout, and you just give me a small piece of it. Can you solder a thick and short copper wire to directly connect R22 ground lead and C13 ground lead? Note that the output ac current loop takes the following path:

Diode(A)-->Diode (K)-->Cout(+) -->Cout(- ) -->R22(-) --> R22(+) -->Q6(S) -->Q6(D) -->Diode (A)

I don't see a direct ground connection between R22 and C13, so this current may take a zigzag path to close the loop. Have a short and direct connection is important.

Please let me know the result.

Thanks,
Youhao