30kHz PWM Dimming

(95% Duty Cycle ON)

30067369

I

Top trace: nDIM input, 2V/div, DC

Bottom trace: I

T = 10µs/div

30kHz PWM Dimming

(10% Duty Cycle ON)

30067370

I

Top trace: nDIM input, 2V/div, DC

Bottom trace: I

T = 10µs/div

30kHz PWM Dimming

(5% Duty Cycle ON)

30067371

I

Top trace: nDIM input, 2V/div, DC

Bottom trace: I

T = 10µs/div

As shown in the Average LED Current vs. PWM DIM Duty Cycle curve the current

drops at very low duty cycle. This is due to the fact that the switcher is shut off

during the LED off time. At low duty cycle the choke does not have time to get

the current up to the control setpoint. This can be looked on as an advantage in

that it allows a wider PWM control range, albeit not linear under about 7.5% duty

cycle (this transition point can be set over a limited range by component value

selection).

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