TPS92560: Boost Constant Current getting fried directly after powering up

Jelko Seiboth

Part Number: TPS92560

Hello!

I am trying to design a LED replacement board for 12V GY6,35 Halogen lamps. My design uses a Osram Duris S10 LED, which is supposed to be driven with 38 V and a constant current of 100 mA.

This is the schematic of the board:

I've taken the design and component values of the TPS92560 Component Calculator.

Sadly, the TPS92560 gets extremely hot as soon as the 12 V AC are connected.

After assembling a completely new test pcb and double-checking all connections and parts, I do not have any clue what could be the issue.

Any help or suggestions are appreciated!

Best regards,

Jelko

over 1 year ago

0 Steven Li over 1 year ago

TI__Mastermind 19665 points

Hi Jelko,

Please be noticed that when configured in boost topology, the VP pin should be connected to the LED top voltage rail. Please refer to Section 5 Pin Configuration and Functions from the datasheet. (A screenshot is shown below.)

Best Regards,

Steven

0 Jelko Seiboth over 1 year ago in reply to Steven Li

Prodigy 10 points

Hi Steven,

the Component Calculator tells me to NC R11 and use a diode for the values I entered:

However, I will try to connect VP to the LED top voltage! Thank you so far.

Best regards,

Jelko

0 Steven Li over 1 year ago in reply to Jelko Seiboth

TI__Mastermind 19665 points

Hi Jelko,

Please check your LED Forward Voltage.

Below are my results from the component calculator:

BR,

Steven

0 Jelko Seiboth over 1 year ago in reply to Steven Li

Prodigy 10 points

Hi Steven,

where do You get that 25.60 V from?

I've got an Osram Duris S10 GW P7LP32.EM-RQRS which has a typical forward voltage of 38 V according to this datasheet:

https://docs.rs-online.com/5658/0900766b813fd7d7.pdf

BR,

Jelko

0 Steven Li over 1 year ago in reply to Jelko Seiboth

TI__Mastermind 19665 points

Hi Jelko,

Sorry, I checked another LED with a similar name.

Please be noticed that the VF of your LED is around 34.2V at 100mA, T_S = 25 °C from the datasheet you mentioned.

Best Regards,

Steven

0 Steven Li over 1 year ago in reply to Jelko Seiboth

TI__Mastermind 19665 points

Supplement:

Does the TPS92560 function while getting extremely hot? Is the output current regulated as you expected?

Or does it fail while getting extremely hot?

0 Jelko Seiboth over 1 year ago in reply to Steven Li

Prodigy 10 points

Hi Steven,

I'll try to recalculate the values for my next prototype for 34 V!

My initial thought was the circuit would reach either 38 V or 100 mA as it should be current-regulated.

The LED does not go on. The TPS92560 breaks before I am even able to measure anything. I am planning to connect the next board to a current regulated DC power supply and try to measure something without breaking the next chip..

Best regards,

Jelko

0 Steven Li over 1 year ago in reply to Jelko Seiboth

TI__Mastermind 19665 points

Hi Jelko,

Got it. Please let me know if you have any update.

BTW, could you share with us what your end equipment is? We can talk through e-mail if needed.

Best Regards,

Steven

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TPS92560: Boost Constant Current getting fried directly after powering up