How to Check LED Driver (Current Regulator) Stability

Customers frequently ask me how to check the feedback loop stability of their LED drivers or other current regulators so I will answer in a REPLY post.

  • +1
    •  Analog Employees 
    on Jun 10, 2020 8:53 PM

    To check the feedback loop stability of an LED driver or other current regulator, use the CTRL input  to command a step change in load current - usually from about half to about full output current.  Then observe the output current and make sure the response to the CTRL step is critically damped.  Adjust the feedback loop compensation if necessary.  One image below shows this method appled to an example circuit schematic and there is also an image below of a scope capture that shows a stable LED current response.

    LT3763, mod DC1831A BCB3226, 42VLED at 4A_0 copy_3.png

    Conditions for Scope Capture:  LT3763EFE, mod  DC1831A, 48VIN, 32VLED at 1.5A to 3A to 1.5A, ILED VCTRL transient_0.bmp

    LT3763EFE, mod  DC1831A, 48VIN, 32VLED at 1.5A to 3A to 1.5A, ILED VCTRL transient_0.bmp