Datasheet

LV5026MC
No.A2042-6/16
LED current and inductande setting
• Relation ship beween REF_IN and CS pin voltage(Power Factor Crrection(PFC))
The output current value is the average of the current value that flows during one cycle. The current value that flows into
coil is a triangular wave shown in the figure below. Make sure to set Ipk so that (average of current value at one cycle)
is equal to (LED current value).Ipk is set by the relationship between REF_IN voltage and Rcs voltage.
This relationship make Power Factor Correction (PFC).Therefore, it is available to make LED current a sine curve.
• Setting Zener voltage
Vzd depend on LED voltage (VF). Choose Zener diode around Vf (LED voltage).When VAC voltage is lower than Vf,
LED operation is not normal. Using Zener diode prevents incorrect operating during VAC voltage lower than Vf. In
detail, refer to [LED current and inductance setting]
In case of REF_IN pin open, this error amplifier negative input(-) is under control of internal VREF voltage
(0.605Vtyp).
Ipk =
(Vac-Vzd)×
R2
R1+R2
Rcs
LED current and inductance setting
It is available to use both no-isolation and isolation applications.
(For non-isolation application)
The output current value is the average of the current value that flows during one cycle. The current value that flows into
coil is a triangular wave shown in the figure below. Make sure to set IL_PK so that (average of current value at one cycle)
is equal to (LED current value).
Ipk: peak inductor current
Vf: LED forward voltage drop
Vac: effective value, R.M.S value
VREF: Built-in reference voltage (0.605V)
VREF_IN: REF_IN voltage (6 pin)
Rs: External sense resistor
Vzd: Zener diode voltage (REF_IN pin)
RESET
REF_IN
CLK
Q
CS
VREF
(0.605V typ)
Rcs
a blockdiagram in outline
+
-
-
OUT
L
R1
R2
Vzd
FET current
FET
Vac
REF_IN
FET current
T
ON
OFF
ToffTon
VREF (0.605V typ)
RESET
REF_IN
CLK
Q
CS
VREF
(0.605V typ)
Rcs
a blockdiagram in outline
+
-
-
OUT
Vac
L
LED
R1
R2
Vzd
Inductor current
Inductor
current
FET
Vac
T
ON
OFF
Ipk
Ipk = (Vac-Vf)/L × T_c
= Vf/L × T_d
IL = Vac/L × T
T_c T_d
FET_on FET_off
T (1cycle)
IL = Vf/L × T
REF_IN
VREF (0.605V typ)/built-in reference
ILED slope is proportion to
Vac voltage (REF pin voltage)