Silan
Microelectronics
SD6800_Datasheet
SINGLE STAGE PRIMARY SIDE REGULATION PFC CONTROLLER FOR LED
DRIVER
DESCRIPTION
The SD6800 is a single stage primary side regulation (PSR) power factor
correction (PFC) controller, specially designed for LED driver.
The Device adopts constant on time operation to achieve high power
factor.
The SD6800 provides accurate constant current control and operates in
boundary conduction mode (BCM) with high efficiency.
The Device adopts primary side regulation eliminating the opto-couple,
secondary feedback control and loop compensation for reducing design
and cost.
The SD6800 provides completed protections such as short LED
protection, open LED protection and over temperature protection, etc.
SOP-8-225-1.27
FEATURES
PSR Flyback topology
Boundary Conduction Mode
Low start current
Leading edge blanking
Constant on-time control
VCC over voltage protection
VCC under voltage lockout
Over temperature protection
Cycle by cycle current limiting
Peak current compensation
Short LED protection and Open LED protection
APPLICATIONS
LED lamp
LED illumination with AC input
ORDERING INFORMATION
Part No.
SD6800
SD6800TR
Package
SOP-8-225-1.27
SOP-8-225-1.27
Material
Halogen free
Halogen free
Packing
Tube
Tape & reel
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
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Microelectronics
BLOCK DIAGRAM
3
Clamp
SD6800_Datasheet
CS
CLAMP
16V/8V
uvlo
CS_O
CS_PL
VCC
6
0.1V
2
FB
CC
MODULE
GM
PFC
MODULE
V_OVP
0.2V
ZCD
LED_S
FB_O
FB_OVP
DRIVE
DR
R
Q
S
LEB
Max_toff
Min_toff
Min_T
5
COMP
GND
1
4
ABSOLUTE MAXIMUM RATING
Characteristics
Supply voltage
Analog pin voltage
Junction temperature
Storage temperature Range
Symbol
V
CC
-
T
j
T
stg
Rating
-0.3 ~ 23
-0.3 ~ 5.5
-40~+150
-55~+150
Unit
V
V
°C
°C
ELECTRICAL CHARACTERISTICS
(unless
otherwise specified,
V
CC
=18V, T
amb
=25°C)
Characteristics
Supply voltage
Operating voltage
Turn-on threshold
Turn-off voltage
Clamp voltage
VCC over voltage threshold
Start-up current
Operating current
FB Feedback
V
CC
V
CCON
V
CCOFF
V
Z
V
CCOVP
I
start
I
op
V
CC
=15V
I
CC
=20mA
After IC starts
9
14.4
6.9
--
21.4
0
300
--
16
8.0
27
23
3
500
18
17.6
9.1
--
24.6
10
800
V
V
V
V
V
μA
μA
Symbol
Test conditions
Min.
Typ.
Max.
Unit
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
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Characteristics
OVP threshold value
Short-circuit detect voltage
Short-circuit detect timing
Zero-crossing detection
FB open loop switching times
Dynamitic characteristic
Leading-edge blanking time
Max. on time
Max. off time
Min. off time
Min. period
Current limit
CS peak limit
Gm amplifier
CS CC compare point
Drive
DR rising time
DR falling time
DR high clamp voltage
Peak drive source current
Peak drive sink current
DR high level
DR low level
Over Temperature Protection
Over temperature detection
Over temperature hysteresis
T
sd
T
sdhys
T
R
T
F
V
DRC
I
srcpk
I
snkpk
V
DRH
V
DRL
C=1nF
C=1nF
Isource=25mA
Isink=20mA
C=1nF
C=1nF
Vcscc
V
CSPL
T
LEB
T
onmax
T
offmax
T
offmin
T
min
COMP connected to 4V via 20K
Symbol
V
FBOVP
V
SHT
T
SHT
V
zcs
N
After 768 switching periods
Test conditions
SD6800_Datasheet
Min.
1.38
--
--
--
--
Typ.
1.46
0.29
768
0.2
768
Max.
1.54
--
--
--
--
Unit
V
V
--
V
--
μs
μs
μs
μs
μs
V
0.60
24
25
3.2
6.3
0.75
33
34
4.2
8.3
0.90
42
43
5.2
10.3
0.49
0.60
0.71
0.097
0.100
0.103
V
100
40
16
0.2
0.7
14
--
200
60
17.5
--
--
15.6
0.3
400
80
19
--
--
--
0.5
ns
ns
V
A
A
V
V
°C
°C
--
--
150
20
--
--
PIN CONFIGURATION
COMP 1
FB 2
CS 3
GND 4
8 NC
7 NC
6 VCC
5 DR
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
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PIN DESCRIPTION
Pin No.
1
2
3
4
5
6
7
8
Pin Name
COMP
FB
CS
GND
DR
VCC
NC
NC
I/O
I/O
I
I
I/O
O
I/O
--
--
SD6800_Datasheet
Function description
RC loop compensation pin, output of transconductance amplifier
Feedback voltage input pin
Current sense pin
Ground
Drive pin
Power supply
NC
NC
FUNCTION DESCRIPTION
The SD6800 is a single stage primary side regulation (PSR) power factor correction (PFC) controller, specially
designed for LED driver. The device adopts constant on time operation to achieve high power factor.
The SD6800 provides accurate constant current control and operates in boundary conduction mode (BCM) with high
efficiency. The device adopts primary side regulation eliminating the opto-couple, secondary feedback control and loop
compensation for reducing design and cost.
The SD6800 provides completed protections such as short LED protection, open LED protection and over temperature
protection, etc.
1.
Start-up and under voltage lockout
After AC supply is powered on, the capacitor connected to pin VCC is charged by AC supply through a start resistor.
Once VCC voltage rises up to 16V, the circuit starts to work. VCC voltage will be pulled down by internal consumption
of IC until the auxiliary winding of Flyback transformer could supply enough energy to maintain VCC voltage above 8V.
If the protection occurs, the output of circuit is off, VCC voltage starts to decrease. If VCC voltage is decreased to 8V,
the capacitor connected to pin VCC is recharged through start resistor.
V
CC
V
START
V
STOP
t
0
I
CC
0
Powered by
resistor
Powered by
auxiliary winding
and resistor
t
Powered by resistor
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
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2.
Drive circuit
SD6800_Datasheet
Drive circuit is power by VCC. When DR＝1, MOSFET is on; When DR＝0, MOSFET is off. T
LEB
＝0.75µs
is set to
avoid the burr which will cause error at the turn-on transient of MOSFET.
3.
Peak current detection and sample holding
When MOSFET is on, the primary current, which is detected by sense resistor, increases linearly. If this current
exceeds the threshold value 0.6V, the current limit comparator acts to turn off MOSFET and DR＝0.
When it is normal, primary peak current is I
pk
, and the secondary diode on time is T
off1
, hence, the output current is
given by:
I
out
=
0.5
⋅
n
⋅
I
pk
⋅
T
off1
T
Where, n is the primary/secondary turns ratio.
I
pk
⋅
T
off1
T
is calculated in integral mode, and
I
pk
⋅
T
off1
T
=
V
cscc
R
sen
is realized through loop control.
Where, R
sen
is the sense resistor.
That is,
I
out
=
0.5
⋅
n
⋅
V
cscc
R
sen
The output of error amplifier COMP is used for control switch on time. When the on time is up, DR＝0, MOSFET is off.
4.
Boundary Conduction Mode
The pin FB detects the voltage across the auxiliary winding by a resistor divider. When the secondary current turns to
zero, FB voltage starts to decrease. If FB voltage is decreased to 0.2V, the MOSFET would be turned on.
5.
VCC over voltage protection and Open LED protection
The output voltage is reflected by the auxiliary winding voltage of the Flyback transformer, and both pin FB and pin
VCC provide over voltage protection function. When VCC voltage exceeds 23V, or FB voltage exceeds 1.46V, the over
voltage protection is triggered and the IC will discharge, VCC voltage start to decrease. If VCC voltage is decreased to
8V, the capacitor connected to pin VCC is recharged through start resistor. If the over voltage condition still exists, the
system will operate in hiccup mode.
6.
Over Temperature Protection
If the circuit is over temperature, the output is shut down to prevent the circuit from damage. The over temperature
protection has the hysteresis characteristic. The temperature should be decreased lower than the threshold
temperature by 20°C for normal operation. This is adopted to avoid frequently change between normal and protection
modes.
7.
LED Short-circuit protection
When LED is short-circuit and held for 768 periods, the protection acts and the circuit restarts after the protection.
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
http: //www.silan.com.cn
Rev.:1.2
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