Crossover frequency of a Buck LED driver depends on load?

F

Flyback

Well-Known Member

• Jul 26, 2014

• #1

Hello,
Would the crossover frequency of a Buck Switch mode LED driver be lower in frequency if the load was changed from LEDs to a dummy load resistor of resistance (VLEDs/ILEDs)?

 

alec_t

Well-Known Member

Most Helpful Member

• Jul 26, 2014

• #2

Are you talking about the corner frequency of an output filter? LTspice should be able to tell you.

 

M

MrAl

Well-Known Member

Most Helpful Member

• Jul 26, 2014

• #3

Hi,

Yeah, what do you mean by the crossover frequency?
Some LED drivers may not be able to start into a purely resistive load as that puts a load on the driver from 0v all the way up to the operating voltage while an LED puts a load on it from some starting voltage like 2.5v or so per LED in series.

 

F

Flyback

Well-Known Member

• Jul 26, 2014

• #4

crossover frequency is the feedback loop bandwidth.
Its where the gain crosses the 0dB line...as you know, the phase at this point should be at least 45 degrees, otherwise the converter could be prone to instability

 

crutschow

Well-Known Member

Most Helpful Member

• Jul 27, 2014

• #5

Is this supply current output or voltage output?

 

F

Flyback

Well-Known Member

• Jul 27, 2014

• #6

output is current regulated