• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 600 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

LM3406: Shut Off time after VINS low & Length of first on time pulse

LM3406: LM3406HV

Minqi Zhao
Intellectual 1660 points
Part Number: LM3406

Dear expert,

My customer is using LM3406HV in lighting. Now they found two problems as below, and made some tests. Could you help to check will their solution have other problems?

  • Device parameters:

Inductance: 47uH * 2 (series connection)

Output capacitance: 4.7uF + 1uF

VCC capacitance: 0.1uF

COMP capacitor: 0.22uF

Ron: 510K

  • Problem 1. Flashing at power off: Paralleling a 4.7uF ceramic capacitor at the output can eliminate this phenomenon. Will the paralleled capacitor category and larger capacitance cause problems ? For example, using 22uF / 63V aluminum electrolysis in parallel.

Cyan: Vin
Blue: COMP
Purple: VCC
Yellow: SW

  • Problem 2. Abnormal start-up after continuous power-on: the front end 36-45V is a switching power supply. After the power is turned off, it takes time to reduce the voltage. The problem will occur if the voltage hasn't been reduced to 6V. After the power supply terminal voltage drops below 6V, then power on will be no problem. They plan to connect two 15K resistors in parallel at the input as discharge resistors, will it cause problems?

Thanks for your suggestions.

  • 0
    TI__Mastermind 28655 points

    Hello,

    Problem 1, parallel capacitors two 4.7 uF solves problem.  Two 22 uF electrolytics in parallel?  Electrolytics are not good for high frequency so they won't reduce the current ripple the same as ceramic.  Adding the capacitors should be okay otherwise.

    Problem 2, Adding two resistors is just more load for their power source even though it is small.  It is not problem for the LM3406.

    Best Regards,