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PDF LT1509IN Data sheet ( Hoja de datos )
| Número de pieza | LT1509IN | |
| Descripción | Power Factor and PWM Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
s PFC and PWM Single Chip Solution
s Synchronized Operation up to 300kHz
s 99% Power Factor over 20:1 Load Current Range
s Current Mode PWM
s Instantaneous Overvoltage Protection
s Dedicated Overvoltage Protection (OVP Pin)
s Minimal Line Current Dead Zone
s Typical 250µA Start-Up Supply Current
s Line Switching Noise Filter
s Low Quiescent Current: 13mA
s Fast 2A Peak Current Gate Drivers
s Separate Soft Start Controls
U
APPLICATIONS
s Universal Power Factor Corrected Power Supplies
and Preregulators
LT1509
Power Factor and
PWM Controller
DESCRIPTION
The LT ®1509 is a complete solution for universal off-line
switching power supplies utilizing active power factor
correction. The PFC section is identical to the LT1248 PFC
controller except the EN/SYNC pin is removed because
PFC and PWM are synchronized internally.
The current mode PWM section (the LT1508 is the volt-
age-mode counterpart) contains all the primary side func-
tions to convert the PFC preregulated high voltage output
to an isolated low voltage output. The PWM duty cycle is
internally limited to 47% (maximum 50%) to prevent
transformer saturation. PWM soft start begins when PFC
output reaches the preset voltage. In the event of brief line
loss, the PWM will be shut off when the PFC output voltage
drops below 73% of the preset value.
, LTC and LT are registered trademarks of Linear Technology Corporation.
BLOCK DIAGRAM
VCC
16V TO 10V
VSENSE
14
IAC
9
OVP
11
SS1
16
7.5V
7.9V
14µA
14µA
SS2
13
+
–
–
EA
+
+
–
VAOUT
10
7.5V
VREF
VREF
12
MOUT ISENSE
87
RUN
2.2V +
M1
–
7µA
IA
25k
IB
IM =
IA2IB
200µA2
IM
–
CA
+
CAOUT
6
–
+
+
0.7V
–
–
PWM0K
+
7V to
4.7V
+
1V
–
–
CL
+
1.2V
–+
4
CSET
+
–
NOTE: PWM PULSE IS DELAYED BY 55% DUTY CYCLE AFTER PFC PULSE
19
RAMP
18 50µA
VC
GND1
3
PKLIM VCC
5 17
R
R
RUN S
Q
OSC
–
+
16V
15
RSET
55%
DELAY
R
SQ
R
200ns
BLANKING
16V
GTDR1
1
GND2
2
GTDR2
20
1500 • BD01
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LT1509
Reference Voltage vs
Temperature
7.536
7.524
7.512
7.500
7.488
7.476
7.464
7.452
7.440
7.428
–75 –50 –25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (°C)
LT1509 • TPC04
Multiplier Current
300
VAOUT = 7V
VAOUT = 6.5V
VAOUT = 6V
150
0
0 250
IAC (µA)
VAOUT = 5.5V
VAOUT = 5V
VAOUT = 4.5V
VAOUT = 4V
VAOUT = 3.5V
VAOUT = 3V
VAOUT = 2.5V
500
LT1509 • TPC05
Supply Current vs Supply Voltage
16
15
14 TJ = –55°C
13
12 TJ = 125°C TJ = 25°C
11
10
9
8
7
6
5
10 21 32
SUPPLY VOLTAGE (V)
LT1509 • TPC06
Frequency vs RSET and CSET
500
450 RSET = 10k
RSET = 15k
400 RSET = 20k
350 RSET = 30k
300
250
200
150
100
50
0
200
600 1000 1400 1800 2200
CSET CAPACITANCE (pF)
LT1509 • TPC09
GTDR Rise and Fall Time
400
300
200
100
0
0
FALL TIME
RISE TIME
NOTE: GTDR SLEWS
BETWEEN 1V AND 16V
10 20 30 40
LOAD CAPACITANCE (nF)
50
LT1509 • TPC07
GTDR1 Maximum Duty Cycle vs
RSET and CSET
1.00
0.99
0.98
0.97
0.96
0.95
0.94
0.93
0.92
0.91
0.90
200
RSET = 10k
RSET = 15k
RSET = 20k
RSET = 30k
600 1000 1400 1800 2200
CSET CAPACITANCE (pF)
LT1509 • TPC10
Start-Up Supply Current vs
Supply Voltage
550
500
450
400
350
300 –55°C
250 25°C
200 125°C
150
100
50
0
02
4 6 8 10 12 14 16 18 20
SUPPLY VOLTAGE (V)
LT1509 • TPC08
MOUT Pin Characteristics
1.5
1.0 TJ = 125°C
TJ = 25°C
0.5 TJ = –55°C
0
–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5
–4.0
–2.4
–1.2 0
1.2
MOUT VOLTAGE (V)
2.4
LT1509 • TPC11
5
5 Page 
LT1509
APPLICATIONS INFORMATION
input up to VC and then the SS2 voltage continues beyond
VC. The PWMOK comparator contains hysteresis and will
pull SS2 low disabling the PWM section if the PFC output
voltage falls below approximately 62% of its preset value
(240V with nominal 382V output).
Start Up and Supply Voltage
The LT1509 draws only 250µA before the chip starts at
16V on VCC. To trickle start, a 91k resistor from the power
line to VCC supplies trickle current, and C4 holds VCC up
while switching starts (see Figure 8); then the auxiliary
winding takes over and supplies the operating current.
Note that D3 and the larger values of C3 are only necessary
for systems that have sudden large load variations down
to minimum load and/or very light load conditions. Under
these conditions the loop may exhibit a start/restart mode
because switching remains off long enough for C4 to
discharge below 10V. Large values for C3 will hold VCC up
until switching resumes. For less severe load variations D3
is replaced with a short and C3 is omitted. The turns ratio
between the primary winding determines VCC
according to :
VOUT = NP
VCC – 2V NS
for 382V VOUT and 18V VCC, Np/Ns ≈ 19.
LINE MAIN INDUCTOR
NP
NS
R1
91k
1W
D1
D2
D3
+ C1
VCC
2µF + C3 + C4
+ C2
2µF
390µF
100µF
Figure 8
LT1509 • F08
Output Capacitor (PFC Section)
GTDR2 (PWM) pulse is synchronized to GTDR1 (PFC) pulse
with 53% duty cycle delay to reduce RMS ripple current in the
output capacitor. See PFC/PWM Synchronization graph in
the Typical Performance Characteristics section.
The peak-to-peak 120Hz PFC output ripple is determined by:
VP-P = 2ILOAD(DC)(Z)
where ILOAD(DC) is the DC load current of the PWM stage
and Z is the capacitor impedance at 120Hz.
For 470µF, impedance is 2.8Ω at 120Hz. At 335W load,
ILOAD(DC) = 335V/382V = 0.88A, VP-P = (2)(0.88)(2.8Ω) =
5V. If less ripple is desired higher capacitance should be
used. The selection of the output capacitor is based on
voltage ripple, hold-up time and ripple current. Assuming
the DC converter (PWM section) is designed to operate
with 240V to 382VIN , the minimum hold-up time is a
function of the energy storage capacity of the capacitor:
tHOLD =
(0.5)COUT
POUT
(382V – 0.5VP–P)2 – 240V2
with COUT = 470µF, VP-P = 11.5V, and POUT = 335W,
tHOLD = 60ms which is 3.6 line cycles at 60Hz. The ripple
current can be divided into two major components. The
first is the 120Hz component which is related to the DC
load current as follows:
I120HZ ≈ ILOAD(DC) √2
The second component is made up of switching frequency
components due to the PFC stage charging the capacitor
and the PWM stage discharging the capacitor. For a 300W
output PFC forward converter running from an input
voltage of 100VRMS, the total high frequency ripple current
was measured to be 1.79ARMS.
For the United Chemicon KMH 450V capacitor series,
ripple current at 100kHz is specified 1.43 times higher
than the 120Hz limit.
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LT1509IN.PDF ] | |
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