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PDF LD7577J Data sheet ( Hoja de datos )
| Número de pieza | LD7577J | |
| Descripción | High Voltage Green-Mode PWM Controller | |
| Fabricantes | Leadtrend | |
| Logotipo |  |
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LD7577J
8/16/2010
High Voltage Green-Mode PWM Controller
with Brown-Out Protection
Rev. 00b
General Description
The LD7577J integrated several functions of protections,
and EMI-improved solution in a tiny package. It minimizes
the component counts and the circuit space, and it’s
perfect for the low cost of applications.
It provides functions of low startup current, green-mode
power-saving operation, leading-edge blanking of the
current sensing and internal slope compensation. Also,
the LD7577J features more protections like OLP (Over
Load Protection), OVP (Over Voltage Protection), and
brownout protection to prevent the circuit being damaged
from the abnormal conditions.
Furthermore, the LD7577J features frequency trembling
to suppress the noise and is an excellent solution for EMI
filter design.
Features
z High-Voltage (500V) Startup Circuit
z Current Mode Control
z Non-Audible-Noise Green Mode Control
z UVLO (Under Voltage Lockout)
z LEB (Leading-Edge Blanking) on CS Pin
z Internal Frequency Trembling
z Internal Slope Compensation
z Internal Over Current compensation
z OVP (Over Voltage Protection) on Vcc
z AC Input OVP (Over Voltage Protection)
z OLP (Over Load Protection)
z Brownout Protection
z 500mA Driving Capability
Applications
z Switching AC/DC Adaptor and Battery Charger
z Open Frame Switching Power Supply
z LCD Monitor/TV Power
Typical Application
AC
input
EMI
Filter
*
BNO
HV VCC OUT
LD7577J
CS
GND COMP
*
*See Application Information
Leadtrend Technology Corporation
LD7577J-DS-00b August 2010
1
www.leadtrend.com.tw
photocoupler
TL431
1 page  
Electrical Characteristics
(TA = +25 °C unless otherwise stated, VCC=15.0V)
PARAMETER
CONDITIONS
High-Voltage Supply (HV Pin)
High-Voltage Current Source
Vcc< UVLO(on), HV=500V
Off-State Leakage Current
Vcc> UVLO(off), HV=500V
Supply Voltage (Vcc Pin)
Startup Current
Operating Current
(with 1nF load on OUT pin)
VCOMP=0V,Fsw=65KHz
VCOMP=3V,Fsw=65KHz
OLP Tripped
OVP Tripped
UVLO (off)
UVLO (on)
OVP Level
Voltage Feedback (Comp Pin)
Short Circuit Current
Open Loop Voltage
VCOMP=0V
COMP pin open
Green Mode Threshold VCOMP
Burst Mode Threshold VCOMP
Current Sensing (CS Pin)
Maximum Input Voltage(Vcs_off)
Leading Edge Blanking Time
Input impedance
Delay to Output
Oscillator for Switching Frequency
Frequency
Fsw=65KHz
Trembling Frequency
Green Mode Frequency
Fsw=65KHz
Modulation Frequency
Fsw=65KHz
Temp. Stability
Voltage Stability
VCC=11V-25V
LD7577J
MIN TYP MAX UNITS
0.5 1.0 1.5 mA
35 μA
320
3.3
3.6
0.78
0.88
9.0 10.0 11.0
15.0 16.0 17.0
26.5 28.0 29.5
μA
mA
mA
mA
mA
V
V
V
1.5 2.2
5.8
2.35
1.4
mA
V
V
V
0.80 0.85 0.90
V
320 nS
1 MΩ
100 nS
60 65 70 KHz
±4 KHz
22 KHz
86 Hz
5%
1%
Leadtrend Technology Corporation
LD7577J-DS-00b August 2010
5
www.leadtrend.com.tw
5 Page 
LD7577J
considering the EMI performance, thermal treatment,
component sizes and transformer design.
VCC
OUT
LD7577J
CS
GND
320ns
blanking
time
Can be removed if the negative
spike is not over spec. (-0.3V).
Fig. 16
Fig. 17
Oscillator and Switching Frequency
The switching frequency of the LD7577J is fixed as
65KHz internally to provide the optimized operations by
Frequency Trembling
The LD7577J is implemented an adjustable frequency
Trembling function which provides the power supply
designers to choose the optimized EMI performance and
lowest system cost. The Trembling frequency is fixed
internally ±4KHz which is incorporated with the 65KHz
switching frequency.
Internal Slope Compensation
Stability is crucial for current mode control when it
operates at more than 50% of duty-cycle. To stabilize the
control loop, the slope compensation is required in the
traditional UC384X design by injecting the ramp signal
from the RT/CT pin through a coupling capacitor. In the
LD7577J, the internal slope compensation circuit has
been implemented to simplify the external circuit design.
On/Off Control
Pulling COMP pin below 1.2V will turn off the LD7577J
and disable the gate output pin of the LD7577J. The
off-mode will be released when the pull-low signal at
COMP pin is removed.
Dual-Oscillator Green-Mode Operation
Lots of topologies have been implemented in different
chips for the green-mode or power saving requirements
such as “burst-mode control”, “skipping-cycle mode”,
“variable off-time control “…etc. The basic operation
theory of all these approaches intends to reduce the
switching cycles under light-load or no-load condition
either by skipping some switching pulses or by reducing
the switching frequency.
What the LD7577J uses to implement the power-saving
operation is Leadtrend Technology’s own IP. By using this
dual-oscillator control, the burst -mode frequency can be
Leadtrend Technology Corporation
LD7577J-DS-00b August 2010
11
www.leadtrend.com.tw
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LD7577J.PDF ] | |
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