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LZC811
PSR & PFC LED Driver Controller
General Description
Fly-back topology
The LZC811 is a single-power stage, Real-Current control to meet accurate
isolated and primary side offline LED lighting
output current
regulator which achieves high power factor. Very less components
The proprietary real-current control method Programmable input AC voltage
can control the LED current accurately from
compensation
the primary side information. It can Leading Edge Blanking on CS/FB pin
significantly simplify the LED lighting system Protection Features
design by eliminating the secondary side
Building in hysteresis OTP
feedback components and the opto-coupler.
VDD over voltage protection
The LZC811 integrates active power factor
Cycle by cycle current limiting on CS
correction and works in Quasi Resonance
pin
mode (QRM) in order to reduce the
Secondary peak current protection
MOSFET switching losses. With a building in
on CS pin
700V start-up MOSFET, IC can eliminate the
Output short to GND protection
power loss caused by start-up resistors to
Output programmable over voltage
provide a high efficiency solution for lighting
protection
applications. The external programmable
FB and CS pins default protection
line voltage compensation provides a more Application circuit
precise output current throughout the
universal AC input voltage range. The
leading edge blanking circuit on the CS/FB
input removes the signal glitch and results in
reduced external components and system
cost. The multi-protection features of
LZC811
VDD Gate
Comp CS
GND
FB
LZC811 greatly enhance the system
reliability and safety. The LZC811 features
VDD and output over voltage protection;
Fig 1 Application Circuit
output short circuit protection, cycle-by-cycle
current limit and secondary peak current
protection on CS pin, VDD UVLO and
auto-restart and over-temperature protection.
The driver output voltage is clamped at 18V
to protect the external power MOSFET.
Features
Single stage PFC
Primary side regulation without
Secondary Feedback
Quasi Resonance (QR) mode with
Confidential
Page 1
Preliminary Ver:0.24

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LZC811
PSR & PFC LED Driver Controller
Pin Assignment
NC
CMP
NC
FB
VDD
CS
DRV
GND
LZC811 Pin Assignment
Absolute Maximum Rating
Symbol
Parameter
VDD Maximum supply voltage on VDD pin
VFB Input Voltage to FB Pin
VCS Input Voltage to CS Pin
VCMP
Input Voltage to CMP Pin
ESD Capability
TMax
HBM Model
Machine Model
Maximum Operating Junction Temperature3
TSTG
Storage Temperature Range
Rating
28.0V
-0.3V to 6.0V
-0.3V to 6.0V
-0.3V to 6.0V
>2000V
>200V
125oC
-55oC to 150oC
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Preliminary Ver:0.24

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LZC811
PSR & PFC LED Driver Controller
Block Diagram
3.6V
Comp
1.0V
Comp
ZVD
Output
OVP
Output
SCP
Bandgap
OTP
VDD
UVLO
VDD OVP
VDD
FB
FB
Clamped
Output
ZCD Current
Regulator
QR-OSC
S SET Q
R CLR Q
Driver
GAT
E
COM
P
CS
S&H
Pin Functions
Name I/O
Pin
No.
CMP
I
1
FB I/O 2
CS
GND
DRV
VDD
NC
NC
I
Power
O
Power
/
I
3
4
5
6
7
8
1.5V
Comp
400nS
LEB
Comp
1.0V
Fig 2 LZC811 Block Diagram
GND
Description
Loop compensation for constant current regulation. Output of the OTA.
The RC network is placed between it and GND.
Detect output diode zero current to regulate output current.
Connected to a resistor divider for sensing the reflected voltage from
auxiliary winding.
Current sense pin, a resistor connects to sense the MOSFET current.
Power Ground.
Totem-pole output to drive the external power MOSFET, Maximum
Voltage is internally clamped to 18V.
Power Supply.
No connect.
No connect.
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Preliminary Ver:0.24

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LZC811
PSR & PFC LED Driver Controller
Electrical Characteristics
(TA=25 and VDD=15V if not otherwise noted)
Symbol
Parameter
Test Conditions
Limits
Min. Typ. Max.
VDD pin
IOP
VDDON
VDDOFF
VDDRST
Operating Current
Turn-on Threshold Voltage
Turn-off Threshold Voltage
Logic Reset VDD Threshold
Voltage
Gate open
VDDOVP VDD Over Voltage Protection
CMP pin
VREF
Reference voltage for OTA
input
ICMP_SINK
ICMP_SOURCE
VCMP_MAX
FB Pin
CMP maximal sink current
CMP maximal source current
CMP max. voltage
VFB_SINK
VFB_SOURCE
FB voltage when sink current
FB voltage when source
current
2mA sink current
4mA
source
current
VFB_ZVD
VFB_OVP
VFB_SCP
FB zero voltage detect
FB voltage when Output OVP
FB voltage when trigger SCP
CS Pin
VCS1
Cycle by Cycle current limited
on CS
FB=0V
∆VCS / ∆IFB
Inner CS Voltage vary with FB
source current
TBLANK
Oscillator
Leading-Edge Blanking Time
FOSC_MAX
FOSC_MIN
Maximal Frequency
Minimal Frequency
GATE Drive Output (GATE Pin)
TR Rise Time
TF Fall Time
CL=1nF
CL=1nF
Over Temperature Protection
-0.1
300
1
16
9
6
25
0.2
50
10
4.0
5.0
GND
0.2
3.6
1.0
1
TBD
400
130
30
200
100
+0.1
500
OTPH
Over Temperature Lockout
145
OTPL
Over Temperature Resume
125
Unit
mA
V
V
V
V
V
uA
uA
V
V
V
V
V
V
V
mV/mA
nS
kHz
kHz
Ns
Ns
°C
°C
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Preliminary Ver:0.24

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LZC811
PSR & PFC LED Driver Controller
Operation
The LZC811 is a primary side control offline LED controller that incorporates all the features for high
performance LED lighting. LED current can be accurately controlled with the real current control
method form the primary side information. Active Power Factor Correction (PFC) is included to
eliminate the unwanted harmonic noise injected onto the AC line.
Startup
During start-up, the current can charge up the VDD hold capacitor. the turn-on and turn-off thresholds
of LZC811 are approximately 15V and 9V respectively.. The 6V hysteresis voltage is implemented to
prevent shutdown from a voltage dip during start-up.
Quasi Resonance mode (QRM)
During the external power MOSFET on time (TON), the rectified input voltage is applied across the
primary side inductor (Lm) and the primary current increases linearly from zero to the peak value (IPK).
When the external power MOSFET turns off, the energy stored in the inductor forces the secondary
side diode to be turn-on, and the current of the inductor begins to decrease linearly from the peak
value to zero. When the current decreases to zero, the parasitic resonant of inductor and all the
parasitic capacitance makes the power MOSFET drain-source voltage decrease, this decreasing is
also reflected on the auxiliary winding. The zero-current detector in FB pin generates the turn on
signal of the external MOSFET when the FB voltage is lower than 0.2V and ensures the MOSFET turn
on at a valley voltage .
As a result, there are virtually no primary switch turn-on losses and no secondary diode
reverse-recover losses. It ensures high efficiency and low EMI noise.
Active Power Factor Correction (APFC)
LZC811 is designed with quasi-resonance and constant on time Ton to achieve high power factor
under normal operation. The on time of LZC811 vary with input AC voltage VP Sinϖt and load
condition and its value is constant basically because of very large loop compensation capacitance on
CMP pin. According to following equations,
I L peak
=
VP
Sinϖt
Lm
×
Ton
I Lavg
=
VP Sinϖt
2× Lm
×
Ton
2
×
f osc
The peak current I Lpeak and average current I Lavg of transformer will be shaped as AC input
sinusoid too because Ton and fosc both are constant and then high power factor can be achieved.
Confidential
Page 5
Preliminary Ver:0.24