TPS92513: TPS92513DGQT

kiran surve

Part Number: TPS92513

Tool/software:

Hi,

We are using TPS92513DGQT for IR LED dimming using PWM controlled from microcontroller.

We are facing LED failures for which we SUSPECT the IC TPS92513 during OFF to ON condition give instantaneous peak current on output which opens the LED.

There are three LEDs connected in series on NEAR_LED+ AND NEAR_LED-, and two IR LED connected on MIDDLE_LED+ and MIDDLE_LED-.

The current is limited to 0.717A in both the circuits. IR LED used has normal operating current as 0.7A and the absolute current rating for the LED is 1000mA.

Please verify the circuit, if it can cause damage to the LEDs.

IR LED parameters.

Schematics of TPS92513

Waiting for your quick response.

Regards,

KIRAN SURVE

7 months ago

0 Zhiqian Wu 7 months ago

TI__Mastermind 31255 points

Hi,

Our expert will reply you today.

0 Steven Li 7 months ago

TI__Mastermind 23150 points

Hi Kiran,

I take a quick look over your schematic and do not see an obvious mistake. Just to double check - Are C23 and C18 open (not component is installed)?

kiran surve said:
We are facing LED failures for which we SUSPECT the IC TPS92513 during OFF to ON condition give instantaneous peak current on output which opens the LED.

Please try capturing the LED current waveform and kindly share the oscilloscope capture. Thanks.

Best Regards,

Steven

0 kiran surve 7 months ago in reply to Steven Li

Prodigy 170 points

C23 and C18 are not installed.

Please find oscilloscope current waveforms taken across parallel combination of resistors R136 & R137.

PWM is set at 50%, 75% and 100%.

Best Regards,

KIRAN SURVE

0 Zhiqian Wu 7 months ago in reply to kiran surve

TI__Mastermind 31255 points

Hi, Kiran

our expert will reply you late.

0 Steven Li 7 months ago in reply to kiran surve

TI__Mastermind 23150 points

Hi Kiran,

I check the oscilloscope captures you shared but do not see any abnormal behavior.

Could you directly measure the LED current? The voltage across the current sense resistor (parallel combination of resistors R136 & R137) only reflects the inductor current but not reflects the LED current.

One thing to check - Does the LED failure happen for all devices? Or does it happen occasionally? (What is the failure rate?)

Best Regards,

Steven

0 kiran surve 7 months ago in reply to Steven Li

Prodigy 170 points

Hi Steven,

Thanks for the reply.

The measured LED current is 710mA when measure keeping current meter in series of LED.

The LED failures are not for all the devices. It happens occasionally. The Failure rate is 5%.

Best Regards,

KIRAN SURVE

0 Steven Li 7 months ago in reply to kiran surve

TI__Mastermind 23150 points

Hi Kiran,

I would recommend you use a current probe to measure the instantaneous current across the LED and check if there is any spike on the current waveform. Measuring the average (or RMS) current with the current meter may not show if there is any spike that may cause damage to the LED.

Also, please check if the LED has a good heat dissipation condition and does not get damaged due to overheat.

Best Regards,

Steven