ZHCSLC6B May 2020 – January 2022 TPS92200
PRODUCTION DATA
For this application, input voltage is 24-V rail with 10% variation, output is 6 white LEDs in series and the inductor current ripple requirement is less than 60% of maximum LED current. To choose a proper peak-to-peak inductor current ripple, the low-side FET sink current limit must not be violated when the converter works in no-load condition. This action requires the half of peak-to-peak inductor current ripple to be lower than that limit. Another consideration is the increased core loss and copper loss in the inductor with this larger peak-to-peak current ripple which is also acceptable. After this peak-to-peak inductor current ripple is chosen, use Equation 10 to calculate the recommended value of the output inductor L.
where
With the chosen inductor value, the user can calculate the actual inductor-current ripple using Equation 11.
In this design, VIN(max) = 26.4 V, VOUT = 18.1 V, ILED = 1 A, choose KIND = 0.6, the calculated inductance is 9.49 µH. A 10-µH inductor is chosen. With this inductor, the ripple, peak, and rms currents of the inductor are 0.57 A, 1.29 A, and 1.01 A, respectively.