AME5144 Datasheet, PDF (10/15 Pages) AMETHERM Circuit Protection Thermistors – High Efficiency, 37V Step-Up Converter for 2 to 10 White LEDs

AME
AME5144
High Efficiency, 37V Step-Up
Converter for 2 to 10 White LEDs
Duty Cycle
The maximum duty cycle of the switching regulator de-
termines the maximum boost ratio of output-to-input volt-
age that the converter can attain in mode of operation.
The duty cycle for a given boost application is defined as:
This applies for continuous mode operation.
D=
V_OUT + V_DIODE - V_IN
V_OUT + V_DIODE - V_SW
Calculating Load Current
The load current is related to the average inductor cur-
rent by the relation:
I_LOAD = I_IND (AVG) x (1 - D)
Where “ D” is the duty cycle of the application. The
switch current can be found by:
I_SW = I_IND (AVG) + 1 /2 (I_RIPPLE)
Inductor ripple current is dependent on inductance, duty
cycle, input voltage and frequency:
I_RIPPLE = D x (V_IN-V_SW) / (f x L)
Combining all terms, we can develop an expression
which allows the maximum available load current to be
calculated:
I_LOAD
( 1-D ) x ( I_SW (max) -
D ( V_IN-V_SW )
2fL
)
10
Rev. D.01