TL431: tl431

PSENGINEER Intelux

Part Number: TL431

I am using TL431 for over voltage protection in my LED Driver. TL431 is used to pull down the VCC of my controller (FL7733-Fairchild). In some cases, TL431 got damaged in Surge Testing. I tried to address the issue, but it do not create any results.

LED Driver details

Input Voltage : 100VAc to 300VAC

Power : 24W

Over Voltage Cutoff - 325VAC

IC VCC- 22V Maximum

Note : Failure is occurred rarely. TL431's Cathode and Anode getting short.

over 5 years ago

0 Trailokya Rai over 5 years ago

TI__Genius 11391 points

Can you please explain the circuit in more detail and provide the value for R1, R2, R16, R17, R18, R19 and R20 and mention path for VCC.

Regards

Trailokya

0 PSENGINEER Intelux over 5 years ago in reply to Trailokya Rai

Intellectual 260 points

Hi..

Thanks for your reply.

R16,R17- 470K

R18-220K

R19- 18K

R20- NIL

R1,R2 - 23K

The voltage divider is set to 2.5V at TL431 reference at 320VAC. At 2.5V, cathod and anode will be short . Net results VCC short, resulting LED Driver OFF.

With regards

Emil Jose

0 Trailokya Rai over 5 years ago in reply to PSENGINEER Intelux

TI__Genius 11391 points

Emil Rose

Thanks for clarification.

As per my understanding when supply on the reference pin of U2 is going more than 2.5V, U2 is turning ON V_Cathode = 2.4V . The diode D3 is turning on and pulling down the VDD supply.

Can you please provide I_Cathode information when it is ON. This should not go more than 100mA otherwise the device may fail .

0 PSENGINEER Intelux over 5 years ago in reply to Trailokya Rai

Intellectual 260 points

Thanks for your response.

The last sentence you wrote is little bit confusing. Because maximum cathode current of TL431 is 100mA. Kindly check it.

And also note, the damage is not happen in all the cases. Some time it happens and it with all makes TI, NXP,ST,IKSEMI etc

0 Trailokya Rai over 5 years ago in reply to PSENGINEER Intelux

TI__Genius 11391 points

Emil

Sorry , that was a typo. I meant to say that the cathode current should not be more than 100mA. Can you pleaase confirm the max cathode current.

Regards

Trailokya

0 Trailokya Rai over 5 years ago in reply to Trailokya Rai

TI__Genius 11391 points

Hi Emil

I haven’t heard back from you, I’m assuming you were able to resolve your issue. If not, just post a reply below (or create a new thread if the thread has locked due to time-out)

Regards

Trailokya

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TL431: tl431