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PDF iW3623 Data sheet ( Hoja de datos )
| Número de pieza | iW3623 | |
| Descripción | AC/DC Digital Power Controller | |
| Fabricantes | iWatt | |
| Logotipo |  |
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iW3623
AC/DC Digital Power Controller for
High Power Factor Off-Line LED Drivers
1.0 Features
●● Isolated AC/DC off-line LED driver
●● Power factor > 0.95 for wide input voltage range
100 – 277VAC
●● Total harmonic distortion (THD) < 10%
●● Under 5% 100Hz/120Hz output current ripple
●● Resonant control to achieve high efficiency
●● LED current foldback with external NTC
●● Small size design
xx Small size input bulk capacitor
xx Small size output capacitor
xx Small transformer
●● Primary-side sensing eliminates the need for
opto-isolator feedback and simplifies design
●● Tight LED current regulation ± 5%
●● Under 0.5 second start-up time
●● Hot-plug LED module support
●● Multiple protection features:
xx LED open circuit protection
xx Single-fault protection
xx Over-current protection
xx LED short-circuit protection
xx Current sense-resistor-short-circuit protection
xx Input over-voltage and brown-out protection
2.0 Description
The iW3623 is a high-performance AC/DC off-line power
supply controller for LED luminaires. The iW3623 combines
power factor correction and LED current regulation into one
controller. It achieves PF > 0.95 and THD < 10% for 100–
277VAC input voltage range.
The iW3623 operates in quasi-resonant mode to provide
high efficiency. The device uses iWatt’s advanced primary-
side sensing technology to achieve excellent line and load
regulation without secondary-feedback circuit. In addition,
the iW3623’s pulse-by-pulse waveform analysis technology
allows accurate LED current regulation. The iW3623
maintains stability over all operating conditions without the
need for loop compensation components.
3.0 Applications
●● Non-dimmable LED lamps and luminaires
●● Optimized for up to 40W output power
Rev. 0.8
iW3623
Preliminary
September 10, 2012
Page 1
1 page  
iW3623
AC/DC Digital Power Controller for
High Power Factor Off-Line LED Drivers
6.0 Electrical Characteristics
VCC = 12 V, -40°C ≤ TA ≤ 85°C, unless otherwise specified (Note 1)
Parameter
Symbol Test Conditions
VIN SECTION
Start-up voltage threshold (Note 2)
VIN_ST
TA= 25°C, CFG resistor = 20kW
TA= 25°C, CFG resistor = 4.7kW
Brown-out threshold (Note 3)
Over-voltage shutdown threshold
Input impedance
VIN range
VBR_TH
VIN_OVP
ZIN
VIN
TA= 25°C, CFG resistor = 20kW
TA= 25°C, CFG resistor = 4.7kW
TA = 25°C, positive edge
After start-up
VCB SECTION
Over-voltage shutdown threshold
Input impedance
VCB_OVP
ZCB
TA = 25°C, positive edge
After start-up
VCB range
FVSENSE SECTION
Input leakage current
VCB
IBVS(FVSENSE)
VSENSE = 2V
Normal voltage threshold
VSENSE(NOM) TA= 25°C, negative edge
Min
1.512
0
1.62
0
1.521
Typ
0.283
0.212
0.283
0.212
1.68
5
1.8
15
1.536
Max
1.848
1.8
1.98
1.8
1
1.551
Unit
V
V
V
V
V
kW
V
V
kW
V
µA
V
Output OVP threshold (default)
BVSENSE SECTION
Input leakage current
FDRV SECTION
Output low level ON-resistance
Output high level ON-resistance 1
Maximum switching frequency
(Note 4)
BDRV SECTION
Output low level ON-resistance
Maximum switching frequency
(Note 4)
Output source current
VSENSE(MAX) TA= 25°C, negative edge
IBVS(BVSENSE)
VSENSE = 0.1V
RDS_ON_LO(FDRV)
RDS_ON_HI(FDRV)
fSW_FDRV(MAX)
ISINK = 5mA
ISOURCE = 5mA
RDS_ON_LO(BDRV) ISINK = 5mA
fSW_BDRV(MAX)
IB
if VIN_A < 130mV
if VIN_A > 130mV
1.683 1.7 1.717 V
1 µA
16 W
25 W
200 kHz
1W
200 kHz
90 kHz
90 mA
Rev. 0.8
iW3623
Preliminary
September 10, 2012
Page 5
5 Page 
iW3623
AC/DC Digital Power Controller for
High Power Factor Off-Line LED Drivers
9.2 IC Start-up
Prior to start-up, the VCC capacitor is charged up through active
start-up circuit controlled by the ASU pin, and through the VIN
and VCB to VCC internal diodes. When VCC is fully charged to a
voltage higher than the start-up threshold VCC(ST), the “Enable”
signal becomes active and enables the control logic, as
shown in Figure 9.1. The iW3623 detects the input voltage
at VIN pin. If the input voltage reaches the start-up threshold,
then constant output current mode is enabled and the
output-voltage starts to ramp up. When the output-voltage
rises above the forward-voltage of LED, the controller
operates in constant current mode. The ASU is disabled
after the flyback operates for about 50 miliseconds.
The iW3623 implements an output current soft-start. The
output current starts at 5% and move quickly to 100% level.
This feature helps to eliminate output current overshoot
during the start-up.
Start-up
Sequencing
VIN
VCC(ST)
VCC
The TON is determined by the VIN_A and VCB_A voltage. VCB_A is
scaled down from the bus voltage. VIN_A is scaled down from
the rectified input voltage.
After power up, VIN_A voltage is monitored. If VIN_A voltage is
higher than VIN_ST, IC will send out driver signal to the boost
and flyback switch.
The frequency of boost circuit is limited to below 90kHz when
VIN_A is greater than 0.13V. It is limited to below 200kHz when
VIN_A is less than 0.13V.
The BJT emitter resistor provides over-current protection for
boost circuit:
IQC(MAX) = VOCP (boost) ⁄ Rs (9.1)
To minimize BJT turn-on loss and reduce EMI, the BJT is
turned on at valley point of collector pin voltage. This valley
signal is sensed by the BVSENSE pin connected to a secondary
winding on boost choke.
The DC bus voltage is typically 30V above the peak of
line voltage. The minimum value is clamped to 200V (see
Section 9.5 for bus voltage calculation).
9.4 BJT Drive
One important feature of the iW3623 is that it directly drives
a BJT switching device in boost circuit.
ENABLE
ASU
.
Figure 9.1 : Start-up Sequencing Diagram
9.3 Boost Operation
D1
BR LC D2
AC
CB +
R3 BDRV
QC
RVIN
VIN_A
BV BI
SENSE
SENSE
ZIN RS
VBUS
RVCB
VCB_A
ZCB
In the switching operation mode, the iW3623 drives the BJT
with dynamic base current control to optimize performance.
The BJT base current ranges from 10mA to 90mA, and it is
dynamically controlled according to the BJT peak conducting
current. The higher the BJT current, the higher the base
current.
9.5 VIN and VCB Resistors
The VIN and VCB pin resistors are chosen primarily to scale
down the AC line voltage and input bulk capacitor voltage
of the flyback circuit. The typical scale factor KCB and KIN is:
●● KCB and KIN = 0.004 for 230V VAC (rms)
●● KCB and KIN = 0.033 for 277V VAC (rms)
The scale factor can be adjusted to optimize efficiency and
power factor. The RVIN and RVCB resistance can be equated
by
Figure 9.2 : Boost Schematic
The PFC control block provides an on-time (TON) controlled,
valley mode switching power factor correction controller.
RVIN = ZIN / KIN – ZIN and RVCB = ZCB / KCB - ZCB
The internal impedance ZIN is 5kΩ ± 5%, ZCB is 15kΩ ± 5%.
For example, with VIN (rms) = 230V, the VIN and VCB pin
resistors should add up to
Rev. 0.8
iW3623
Preliminary
September 10, 2012
Page 11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet iW3623.PDF ] | |
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