amc7150 ADDtek Corp, amc7150 Datasheet - Page 5

• Manufacturer Part Number: amc7150
• Description: 1.5a Power Led Driver
• Manufacturer: ADDtek Corp

Inductor
diode while switch turn-off. In order to reduce the current ripple on LEDs, the L value should high enough to keep the
system working at continuous-conduction mode that inductor current won’t fall to zero.
inductor voltage v
Therefore
Where, V
flywheel diode D
voltage of the switch which has a typical value of 1V.
turn-on time can also be known by
With knowledge of the peak switch current and switch on time, the value of inductance can be calculated.
Copyright © 2009 ADDtek Corp.
The Inductor L stores energy during switch turn-on period and discharge driving current to LEDs via flywheel
Since in steady-state operation the waveform must repeat from one time period to the next, the integral of the
Since the operation frequency f is determined by choosing appropriate value for timing capacitor C
t
∫
L
t
t
ON
0
OFF
T
ON
s
=
v
LED
=
L
V
dt
=
CC
D
V
is the total forward voltage (at expecting current) of the LED string, V
=
⋅
−
CC
T
∫
V
F,
s
0
L
t
ON
−
=
Rsense
V
over one time period must be zero:
V
Rsense
v
D
f
L
Rsense
V
I
dt
PK
LED
−
is the peak value of the voltage drop across Rsense which is 300mV, and V
V
+
−
Where
SAT
∫
+
t
T
V
ON
V
s
SAT
−
v
F
L
V
dt
−
LED
D
V
=
(
LED
Dutycycle
⋅
0
t
ON
Where
)
=
T
t
s
ON
=
5
t
t
+
ON
ON
t
OFF
+
t
OFF
F
is the forward voltage of the
DD034_ D -- JANUARY 2009
AMC7150
SAT
is the saturation
T
, the switch