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LM3424 minimum on time clarification

Vini
Intellectual 895 points
Other Parts Discussed in Thread: LM3424

Hi,

I am using a two stage LED driver solution. 1st stage is AC-DC and LM3450A is used for this. 2nd stage is DC-DC and LM3424 is used for that.

I am using eval boards for both these ICs for evaluation. LM3450A eval board outputs a 50V constant voltage that is used to drive LM3424. LM3424 is driving 9W LED bulb (30V @ 300mA). A PWM signal is used to control the LM3424 LED dimming.

When LED brightness is reduced gradually from 100% to ~ 10% by reducing the PWM duty cycle, the output current is not constant and LEDs start flickering.

What can be the reason for this? PWM frequency is 2kHz. I am doubting the minimum on time requirement of LM3424.

How to confirm this? And what can be a possible workaround?

Regards,

Vinod