Cirrus Logic AN374 - Manual (Page 5)

AN374
AN374REV2 5
2.2 Definition of Symbols
Symbol Description
F
sw
Second-stage switching frequency
F
sw1
& F
sw2
Switching frequency for channel 1 and channel 2
TT Second-stage switching period
TT
CH1
& TT
CH2
Switching period for channel 1 and channel 2
T1
CH1
& T1
CH2
Second-stage primary FET ‘ON’ time for channel 1 and channel 2
T2
CH1
& T2
CH2
Second-stage secondary rectifier diode conduction time for channel 1 and channel 2
T3
CH1
& T3
CH2
Time the second-stage FET and rectified diode are ‘OFF’ for channel 1 and channel 2
D
MODE1
& D
MODE2
Duty ratio for Mode 1 and Mode 2
V
IN
Input line voltage
V
Reflected
Voltage across secondary winding reflected onto primary
V
CLAMP
Primary clamping voltage above boost output voltage (V
BST
)
I
PK(FB)
Maximum second-stage peak current in primary-side FET
I
PK1(FB)
& I
PK2(FB)
Maximum second-stage peak current in primary-side FET for Mode 1 and Mode 2
I
MODE1
& I
MODE2
Output current for Mode 1 and Mode 2
V
MODE1
& V
MODE2
Output voltage for Mode 1 and Mode 2
R
Sense
Second-stage primary current sense resistor
R
NTC
& T
NTC
Negative temperature coefficient resistance and corresponding temperature
I
PK(BST)
Maximum boost inductor current
L
P
Second-stage primary inductance
L
BST
Boost inductance
V
BST
Boost output voltage
N Flyback transformer turns ratio N
P
/N
S
V
CH1
Channel 1 secondary output VDC (channel 1 LED string supply voltage)
V
CH2
Channel 2 secondary output VDC (channel 2 LED string supply voltage)
I
CH1
& I
CH2
Channel 1 and channel 2 LED string current
P
OUT
Load power = Power to the LED string
I
Red
Output current that flows through the amber/red color LED string
I
White
Output current that flows through the white/blue color LED string
dim
The CS1630/31 color control system has the ability to maintain a constant CCT or change
CCT as the light dims. OTP configurations allow the selection of the dimming profile. A
specific CCT profile can be programmed to the digital mapping device. The mapping is
two-dimensional: one current versus temperature profile is generated for each dim level.
The CS1630/31 provides two-dimensional mapping for the color LED’s current only, and
one-dimensional mapping (current versus dim level) for the other string.
GAIN
DR
& GAIN
DTR
The dim-regulated gain and dim-regulated plus temperature-regulated gain
T1
CH1
TT
CH1
----------------
 
 
T1
CH2
TT
CH2
----------------
 
 