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PDF LD7591 Data sheet ( Hoja de datos )
| Número de pieza | LD7591 | |
| Descripción | Transition-Mode PFC Controller | |
| Fabricantes | Leadtrend Technology Corporation | |
| Logotipo |  |
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LD7591
04/30/2009
Transition-Mode PFC Controller with Fault Condition Protection
Datasheet. P03 (for Internal Use Only)
General Description
The LD7591 is a voltage mode PFC controller operating on
transition mode, integrated several functions of protection,
such as OVP, OCP, and Brown-in protection. It minimizes
the components counts and is available in a SOP-8 or DIP-8
package. Those make it an ideal design for low cost
applications.
It provides functions of low startup current, over voltage
protection, open feedback protection, disable function, over
current protection, under voltage lockout and integrated LEB
of the current sensing. Also, the LD7591 features without
mains voltage sensing compared with traditional current
mode PFC for power saving. The LD7591 can be disabled if
the INV pin voltage is lower than 0.45V and the operating
current decreases to 65μA
.
Features
z Transition mode of PFC pre-regulator
z Voltage mode control
z Programmable max. on-time
z Low Startup Current (<30μA)
z UVLO (Under Voltage Lockout)
z LEB (Leading-Edge Blanking) on CS Pin
z Open-Feedback Protection and Disable Function
z OVP (Over Voltage Protection)
z OCP (Cycle by cycle current limiting)
z 800/-1200mA Driving Capability
z Internal OTP function
Applications
z Output above 65W adaptor.
z Open Frame Switching Power Supply
z LCD TV Power Supply
z LED Power Supply
Patent Pending
Typical Application for Boost PFC
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AC EMI
Inpu Filter
t
7
8
4
5
1
32
6
Leadtrend Technology Corporation
LD7591-DS-P03 Apr. 2009
1
1 page  
Absolute Maximum Ratings
Supply Voltage VCC
OUT
COMP, INV, CS, RAMP, ZCD
Maximum Junction Temperature
Operating Junction Temperature Range
Operating Ambient Temperature Range
Storage Temperature Range
Package Thermal Resistance (SO-8, θJA)
Package Thermal Resistance (DIP-8, θJA)
Power Dissipation (SOT-8, at Ambient Temperature = 85°C)
Power Dissipation (DIP-8, at Ambient Temperature = 85°C)
Lead temperature (Soldering, 10sec)
ESD Voltage Protection, Human Body Model
ESD Voltage Protection, Machine Model
Gate Output Current
LD7591
30V
-0.3 ~VCC
-0.3 ~7V
150°C
-40°C to 125°C
-40°C to 85°C
-65°C to 150°C
155°C/W
100°C/W
420mW
650mW
260°C
2.5 KV
250 V
800mA/-1200mA
Caution:
Stresses beyond the ratings specified in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only
rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not
implied.
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Leadtrend Technology Corporation
LD7591-DS-P03 Apr. 2009
5
5 Page 
OVP and Disable on INV pin
To prevent the over voltage on the output capacitor from the
fault condition, LD7591 is implemented with an OVP
function on INV pin. Whenever the INV voltage is higher
than the OVP threshold voltage 2.675V, the output gate
drive circuit will be shutdown simultaneously thus to stop
the switching of the power MOSFET until the INV pin down
to 2.5V. The OVP function in LD7591 is an auto-recovery
type protection. The figure 15 shows its operation. On the
other hand, if the OVP condition is removed, the Vcc level
will get back to normal level and the output will
automatically return to the normal operation.
The disable comparator disables the operation of the
LD7591 when the voltage of the inverting input is lower than
0.35V and there is 100mV hysteresis. An external small
signal MOSFET can be used to disable the IC, referring to
figure 14. The IC operating current decreases below 65μA
to reduce power consumption if the IC is disabled.
LD7591
Fig. 16
Figure 17 shows typical ZCD-related waveforms. Because
the ZCD pin has some capacitance, there can be some
delay caused by Rz1 and the turn-on time can be delayed.
Ideally, the switch must be turned on when the inductor
current reaches zero; but because of the structure of the
ZCD delay, it is turned on after some delay time. During this
delay time, the stored charge of the COSS (MOSFET
output capacitor) is discharged through the path indicated in
figure18. This charge is transferred into a small filter
capacitor, Cin1, which is connected to the bridge diode.
Therefore, there is no current flow from the input side,
meaning the input current Iin is zero during this period. In
order to reduce the negative current flowing the internal
diode, the resistance of RZ1 is suggested larger than 47kΩ.
Fig. 15
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OUT
RAMP
COMP
IPEAK
Inductor
Current
Ton
Tdis
tzero
INEG
-n · (VOUT – VIN)
0A
Zero Current Detection (ZCD)
Figure 16 shows typical ZCD-block. The Zero Current
Detection block switches on the external MOSFET as the
current through the boost inductor has gone to zero using
an auxiliary winding coupled with the inductor. This feature
allows transition-mode operation. If the voltage of the ZCD
pin goes higher than 0.2V, the ZCD comparator waits until
the voltage goes below 0.1V. If the voltage goes below 0.1V,
the zero current detector turns on the MOSFET. The ZCD
pin is protected internally by two clamps, 6.7V-high clamp
and -0.7V-low clamp. The 150us timer generates a
MOSFET turn on signal if the driver output has been low for
more than 150us from the falling edge of the driver output.
AUX
Voltage
-n · VIN
ZCD
Voltage
VOUT
0V
Delay
Time
-n · (VOUT – VIN)Ra/(Ra+Rb)
0.1V
-0.7V-Clamp
VDS
Minimum
Voltage
Turn-on
0V
Fig. 17
Leadtrend Technology Corporation
LD7591-DS-P03 Apr. 2009
11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet LD7591.PDF ] | |
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