PA5711 데이터 시트보기 (PDF) - ProTek Devices.
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PA5711 Datasheet PDF : 8 Pages
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ANALOG PRODUCTS DIVISION
PA5711
High Voltage LED Driver
2.2.11 Inductor design
The LED ripple current along with factors such as Maximum TON, Minimum input voltage and total forward voltage drop across
the LED’s (VF) at the desired average LED current decide the value of the inductor. The minimum voltage is dependent on the
specific application and the Maximum TON is determined by the duty cycle and the switching frequency.
The maximum duty cycle - Dmax is given by :
Dmax =
VLEDstring
Vin
Where
VLEDstring is the desired forward voltage
drop across LED string at the designed
LED current
Vin is the minimum input voltage
The maximum duty cycle must be maintained below 50% to maintain open loop stability and sub harmonic oscillations.
The Maximum ON-time can be calculated as follows:
tONmax =
Dmax
fs
Where
fs is the switching frequency
The size of the inductor can be calculated using the equation :
Lmin =
tONmax * (Vin – VLEDstring)
ILED * γ
Where
γ is the inductor ripple
The peak inductor current is given by :
γ
ILmax = ILED * [1+ ]
2
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7
Rev.0. 03/12
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