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PDF LD7750 Data sheet ( Hoja de datos )

Número de pieza LD7750
Descripción High Voltage Green-Mode PWM Controller
Fabricantes Leadtrend 
Logotipo Leadtrend Logotipo



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LD7750
2/23/2010
High Voltage Green-Mode PWM Controller with
Over Temperature Protection
Rev. 00b
General Description
Features
The LD7750 integrates several functions of protections,
and EMI-improved solution in a SOP-8, SOP-7, or DIP-8
package to minimize the component counts and the circuit
space.
The device provides functions of low startup current,
green-mode power-saving operation, leading-edge
blanking of the current sensing and internal slope
compensation. Also, the LD7750 features more
protections like OLP (Over Load Protection), OVP (Over
Voltage Protection), and OTP (Over Temperature
Protection) to prevent the circuit being damaged under the
abnormal conditions. The LD7750 features built-in
auto-recovery function for OVP on Vcc pin and OLP.
Furthermore, the LD7750 features frequency swapping to
depress radiation noise, providing an excellent solution for
EMI filter design.
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 Swapping
z Internal Slope Compensation
z Internal Over Current Protection
z OVP (Over Voltage Protection) on Vcc
z OLP (Over Load Protection)
z External OTP through a NTC
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
*
HV VCC OUT
LD7750
OTP
CS
GND COMP
*See Application Information
*
photocoupler
Leadtrend Technology Corporation
LD7750-DS-00b February 2010
1
www.leadtrend.com.tw
Free Datasheet http://www.datasheet4u.ne

1 page




LD7750 pdf
Electrical Characteristics
(TA = +25°C unless otherwise stated, VCC=15.0V)
PARAMETER
CONDITIONS
High-Voltage Supply (HV Pin)
High-Voltage Current Source
Off-State Leakage Current
VCC< UVLO(on), HV=500V
VCC> UVLO(off), HV=500V
Supply Voltage (Vcc Pin)
Startup Current
Operating Current
(with 1nF load on OUT pin)
VCOMP=0V, LD7750
VCOMP=3V, LD7750
OLP tripped, LD7750
OVP tripped, VCC=OVP
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
Current Sensing (CS Pin)
Maximum Input Voltage,Vcs_off
Leading Edge Blanking Time
Input impedance
Delay to Output
LD7750
MIN TYP MAX UNITS
0.5 1.0 1.5 mA
35 μA
200 320 400
2.5
2.9
0.50
0.63
9.0 10.0 11.0
15.0 16.0 17.0
24.5 26.0 27.5
μA
mA
mA
mA
mA
V
V
V
1.45 1.75
mA
5.3 5.7
V
2.75 V
2.0 V
0.80 0.85 0.90
V
250 nS
1 MΩ
100 nS
Leadtrend Technology Corporation
LD7750-DS-00b February 2010
5
www.leadtrend.com.tw
Free Datasheet http://www.datasheet4u.net/

5 Page





LD7750 arduino
Fig. 15
Fig. 16
LD7750
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
LD7750, the internal slope compensation circuit has been
implemented to simplify the external circuit design.
On/Off Control
The LD7750 can be turned off by pulling COMP pin to
lower than 2.0V. The gate output pin of LD7750 will be
disabled immediately under such condition. The off-mode
can be released when the pull-low signal is removed.
Green-Mode Operation
By using the green-mode control, the switching frequency
can be reduced under the light load condition. This feature
helps to improve the efficiency in light load conditions.
The green-mode control is Leadtrend Technology’s own
IP.
Over Load Protection (OLP) - Auto
Recovery
To protect the circuit from the damage caused by
overload condition or output short condition, a smart OLP
function is implemented in the LD7750 for it. The OLP
function in LD7750 is an auto-recovery type protection.
Fig. 17 shows the waveforms of the OLP operation.
Under such fault condition, the feedback system will force
the voltage loop toward saturation and thus pull the
voltage on COMP pin (VCOMP) to high. Whenever the
VCOMP trips the OLP threshold of 5.0V and stays for over
63mS, the protection will be activated to turn off the gate
output and to shutdown the switching of power circuit.
The 63mS delay time is to prevent the false-trigger during
the power-on and turn-off transient.
Leadtrend Technology Corporation
LD7750-DS-00b February 2010
11
www.leadtrend.com.tw
Free Datasheet http://www.datasheet4u.net/

11 Page







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