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TPS55165-Q1: Correct buck boost solution

Part Number: TPS55165-Q1

Hi,

I am looking for a suitable buck-boost converter / controller for the power supply with following specs:-

Input = 8V to 32VDC

Output = 12V at 20mA.

Concern is of efficiency since the load current is as low as 20mA

Kindly advise

Regards

Atul Bhakay

  • You can enable the low power mode that will skip pulses and reduce the switching losses to enhance efficiency at light load.
  • Hello Youhao,

    i tried the solution, but it seems that this IC or my circuit is not working in a buck-boost mode.

    following are the results

    1. i tried the solution with web-bench and downloaded the results. built the same circuit on general purpose board for verification.

    2. circuit works fine in buck mode (Vin >15VDC) and we get the output 12VDC

    3. applied voltage is reduced to 8V and no output is observed. (only few mV)

    4. rechecked the connections as per the simulation circuit and everything looks to be correct.

    typical supply scenario  on field

    1. 10.8V

    2. 24V

    3. 14.4V

    4. 8.6V

    Can someone help to get the circuit in working mode? for the full range of Vin 8 to 32VDC

    TPS55165_vin=8.6V.pdfRegards

    Chetan kulkarni

  • Layout plays a critical role. If you have not followed the layout guideline offered in the datasheet, there may be noise issues that can affect the normal operation of the device. Please order an EVM and evaluate. It will support your said application scenario. Since most functions are integrated and preset, including the loop compensation, it does not need many external components, but on the other hand there are not much room to choose the external components other than the ones used on the EVM.
  • Hi Youhao

    thanks for the reply.

    is there any way that will help us to evaluate the basic functionality on the circuit built on general purpose board?

    i understand that this chip works on high frequency and layout plays critical role but would that that really stop the bcuk-boost operation? i can understand that layout plays vital role in overall performance like ripple, load regulation etc. but i can not think of any reason for trouble in basic operation.

    if the IC can work in buck-boost mode, then it should at-least try to regulate the voltage near 12V and should not stop giving output. is my statement correct?

    on general purpose board circuit, i am not worried about performance parameters but just checking the basic functionality.

    regards

    Chetan

  • Can you monitor L1 and L2 voltages at 8V input?
  • I monitored voltages at L1 and L2. it is around 5v.

    i observed some thing which i could not understand.

    • applied Vin =8.6V and observed Vout = 6.2V
    • increased Vin gradually and at 14.6V Vout is 11.98V
    • checked the same till 30V and Vout is stable.
    • reduced voltage gradually to 8.6V and Vout was stable 11.98V.
    • with input voltage 8.6V turned off the supply and restarted but Vout was observed as 6.2V.
    • Checked with Vin >Vout  and Vout was 11.98V then reduced voltage but Vout was stable.

    looks like circuit can not go in boost mode with Vin < Vout. But with the Vin >Vout it generates Vout voltage correctly and then automatic switching from buck to boost happens.  if this is true then what would be the probable cause for not working in boost mode at startup condition?

  • From your description, it seems your board has a lot of internal voltage drops during switching. If you have Vin=8.6V, the L1 should has its high level of 8.6V, but you just see around 5V. As I already recommended, please order an EVM and evaluate with it, so you can save your time.