LM3429: Unable to work, no output voltage

Hi Wu,

The LM3429 is designed for applications up to ~5A. I am not aware of this device ever being used at 50A. The max gate charge of your NMOS is almost 90nC which would at least require an additional gate driver between the controller and the NMOS.

What type of LED requires 50A? Is this 50A pulsed or continuous? I see you have PWM dimming configured, what is the frequency and duty cycle? What is the forward voltage and how many LEDs are in series?

What type of cooling/heat sinking is used for this design? What is the total power output?

It sounds like something was damaged in your board...I would double check the current rating and operating temperature of all of the components to make sure they are appropriately de-rated.

I see you have two 2mΩ sense resistors in parallel for a total resistance of 1mΩ. According to the datasheet equations, the 1mΩ sense resistors corresponds to 100A, not 50A.

You also have an effective 1mΩ limiting resistance which corresponds to a current limit of 245A. This could be a serious problem.

Even if you fix these errors, as this device was designed for ~5A applications, I am doubtful that this design will function effectively at 50A operation.

Regards,

Zach

Hi Zach,
Thank you for your reply. There is indeed a problem with our design. We want to design an LED driver circuit with a total power of 1200W and an input voltage of 51V. The LEDs will be multiple 12V LED beads connected in series and parallel. The heat dissipation will use a combination of aluminum substrate, heat sink, and fan. Is there a suitable design scheme, or is it feasible to use a boost circuit? Or is it feasible to use two LM3429s for driving? If we use the boost circuit scheme, what is the maximum boost voltage that can be achieved? If you have a better design scheme, please let me know. Thank you very much.

Regards,

Wu