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PDF LD7522H Data sheet ( Hoja de datos )
| Número de pieza | LD7522H | |
| Descripción | Smart Green-Mode PWM Controller | |
| Fabricantes | Leadtrend Technology | |
| Logotipo |  |
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LD7522H
1/9/2009
Smart Green-Mode PWM Controller with Multiple Latch-Mode
Rev. 04
Protections
General Description
The LD7522H is a low startup current, current mode PWM
controller with green-mode power-saving operation. The
SOP-8/DIP-8 package integrated functions such as the
leading- edge blanking of the current sensing, internal slope
compensation, line compensation, and several protection
features. The protection functions include cycle-by-cycle
current limit, OVP, OTP, OLP, and brownout protection. It
provides the users a high efficiency, low external component
counts solution for AC/DC power applications.
Furthermore, to satisfy various protection requirements,
both latch-mode protection and auto-recoverable protection
can be easily achieved by configuring LD7522H on different
operation modes.
The special green-mode control is not only to achieve the
low power consumption but also to offer a non-audible-noise
operation when the LD7522H is operating under light load or
no load condition.
Features
z High-Voltage CMOS Process with Excellent ESD
protection
z Very Low Startup Current (< 35μA)
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 Slope Compensation
z OVP (Over Voltage Protection)
z OLP (Over Load Protection)
z OTP (Over Temperature Protection) through a NTC
z Brownout Protection
z Flexibility on Latch/Auto-Recoverable Protection Mode
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 EMI
input Filter
OVP
VCC
BNO
LD7522H
OUT
CS
(-)LATCH
GND COMP
Leadtrend Technology Corporation
LD7522H-DS-04 January 2009
1
www.leadtrend.com.tw
photocoupler
TL431
1 page  
Electrical Characteristics
(TA = +25oC unless otherwise stated, VCC=15.0V)
PARAMETER
CONDITIONS
Supply Voltage (VCC Pin)
Startup Current
Operating Current
(with 1nF load on OUT pin)
VCOMP=0V
VCOMP=3V
Protection Mode (note 1)
UVLO (off)
UVLO (on)
Voltage Feedback (Comp Pin)
Short Circuit Current
Green Mode Threshold VCOMP
VCOMP=0V
Current Sensing (CS Pin)
Maximum Input Voltage, VCS(OFF)
Leading Edge Blanking Time
Input impedance
Delay to Output
Gate Drive Output (OUT Pin)
Output Low Level
VCC=15V, Io=20mA
Output High Level
Rising Time
VCC=15V, Io=20mA
Load Capacitance=1000pF
Falling Time
Load Capacitance=1000pF
Oscillator
Frequency
Green Mode Frequency
Frequency Temp. Stability
(-40°C~85°C)
Frequency Voltage Stability
(VCC=12V-30V)
Latch Protection (-)LATCH Pin)
(-)LATCH Pin Source Current
Turn-On Trip Level
Turn-Off Trip Level
(-)LATCH pin de-bounce time
De-latch Vcc Level
(PDR, Power Down Reset)
Brownout Protection (BNO Pin)
Brownout Turn-On Trip Level
Brownout Turn-Off Trip Level
BNO pin de-bounce time
Zener Clamping Voltage on BNO Pin IBNO=1.5μA
Note 1: When OVP, OLP, or Latch Protection is tripped.
Leadtrend Technology Corporation
LD7522H-DS-04 January 2009
5
www.leadtrend.com.tw
LD7522H
MIN
TYP
MAX UNITS
20 35 μA
3.5 5.0 mA
3.0 mA
0.7 mA
9.0
10.0
11.0
V
15.0
16.0
17.0
V
2.5 4.0 mA
2.6 V
0.800
1
0.850
350
150
0.900
V
nS
MΩ
nS
1.0 V
9.0 V
50 160 nS
30 60 nS
60 65 70 KHz
20 KHz
3%
1%
92 100 108 μA
3.30
3.50
3.70
V
2.40
2.50
2.60
V
100 μS
6.8 8.0 8.7 V
1.20
1.05
100
1.25
1.10
5.0
1.30
1.15
V
V
μS
V
5 Page 
LD7522H
Oscillator and Switching Frequency
The switching frequency of LD7522H is fixed as 65KHz
internally to provide the optimized operations by considering
the EMI performance, thermal treatment, component sizes
and transformer design.
Voltage Feedback Loop
The voltage feedback signal is provided from the TL431 in
the secondary side through the photo-coupler to the COMP
pin of LD7522H. The input stage of LD7522H, like the
UC384X, is with 2 diodes voltage offset then feeding into the
voltage divider with 1/3 ratio, that is,
V+ (PWM COMPARATOR
)
=
1
3
× (VCOMP
−
2VF )
A pull-high resistor is embedded internally thus can be
eliminated on the external circuit.
Dual-Oscillator Green-Mode Operation
There are many different topologies has 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 intended to reduce the
switching cycles under light-load or no-load condition either
by skipping some switching pulses or reduce the switching
frequency.
By using this dual-oscillator control, the green-mode
frequency can be well controlled and further to avoid the
generation of audible noise.
Internal Slope Compensation
A fundamental issue of current mode control is the stability
problem when its duty-cycle is operated more than 50%. To
stabilize the control loop, the slope compensation is needed
in the traditional UC384X design by injecting the ramp signal
from the RT/CT pin through a coupling capacitor. In
LD7522H, the internal slope compensation circuit has been
implemented to simplify the external circuit design.
Current Sensing, Leading-Edge Blanking
The typical current mode PWM controller feedbacks both
current signal and voltage signal to close the control loop
and achieve regulation. The LD7522H detects the primary
MOSFET current from the CS pin, which is not only for the
peak current mode control but also for the pulse-by-pulse
current limit. The maximum voltage threshold of the current
sensing pin is set as 0.85V. Thus the MOSFET peak current
can be calculated as:
IPeak(Max.)
=
(0.85)
RS
A 350nS leading-edge blanking (LEB) time is included in the
input of CS pin to prevent the false-trigger from the current
spike. However, the total pulse width of the turn-on spike is
decided by the output power, circuit design and PCB layout.
It is strongly recommended to adopt a smaller R-C filter (as
shown in Figure 21) to avoid the CS pin being damaged by
the negative turn-on spike.
VCC
OUT
LD7522H
CS
GND
R-C filter is needed whenever the negative
spike is exceed -0.3V or the total spike
width is over 350nS LEB period.
Fig. 21
Leadtrend Technology Corporation
LD7522H-DS-04 January 2009
11
www.leadtrend.com.tw
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet LD7522H.PDF ] | |
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