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PDF LD7752B Data sheet ( Hoja de datos )

Número de pieza LD7752B
Descripción Green-Mode PWM Controller
Fabricantes Leadtrend 
Logotipo Leadtrend Logotipo



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No Preview Available ! LD7752B Hoja de datos, Descripción, Manual

LD7752B
6/11/2013
Green-Mode PWM Controller with HV Start-Up Circuit and
Soft Start time Adjustment
REV. 00
General Description
The LD7752B brings high performance, highly integrated
functions, protections and EMI-improve solution. Its an
ideal solution for those cost-sensitive system, reducing
component count and overall system cost.
The LD7752B features high voltage startup circuit,
minimum loss and green-mode power-saving operation,
leading-edge blanking of the current sensing and internal
slope compensation. They also consist of more
protections of OLP (Over Load Protection) and OVP (Over
Voltage Protection) to prevent the circuit from damage
under abnormal conditions.
Furthermore, the proprietary frequency swapping function
can reduce the noise and help the power circuit designers
to enhance EMI performance with fewer components and
less developing time.
Features
High-Voltage Startup Circuit
UVLO (Under Voltage Lockout)
LEB (Leading-Edge Blanking) on CS Pin
Internal Frequency swapping
Internal Slope Compensation
Internal OCP Compensation
OVP (Over Voltage Protection) on Vcc Pin
OLP (Over Load Protection)
+250mA/-500mA Driving Capability
Soft-Driving
Soft Start Time and Grouping Frequency Adjustment
Applications
LCD Monitor/TV Power
Switching AC/DC Adaptor and Battery Charger
Open Frame Switching Power Supply
Typical Application
AC EMI
input Filter
HV VCC
*CT OUT
LD7752B
CS
GND COMP
photocoupler
Leadtrend Technology Corporation
LD7752B-DS-00 June 2013
1
www.leadtrend.com.tw

1 page




LD7752B pdf
Electrical Characteristics
(TA = +25C unless otherwise stated, VCC=15.0V)
PARAMETER
CONDITIONS
High-Voltage Supply (HV Pin, HV MOS process)
High-Voltage Current Source
VCC < UVLO(on)
Off-State Leakage Current
VCC > UVLO(off), HV=500V
Supply Voltage (VCC Pin)
Startup Current
VCC=15V, HV=500V
Operating Current
(with 1nF load on OUT pin)
VCOMP=0V
VCOMP=3V
OLP tripped
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
Fixed Frequency Mode Threshold
VCOMP()
Green Mode Threshold VCOMP()
25kHz
Burst Mode Threshold VCOMP
Current Sensing (CS Pin)
VCS-OFF
VCS-MIN
Leading Edge Blanking Time
Delay to Output
Oscillator for Switching Frequency
Frequency
Temp. Stability()
Voltage Stability()
(VCC =11V-25V)
Green Mode Frequency
100kHz
Frequency Swapping
100kHz
Maximum Duty
LD7752B
MIN TYP MAX UNITS
1.1 1.3 1.5 mA
15 A
100 150 200
0.55
2.0
230
230
7.0 8.0 9.0
15.0 16.0 17.0
27.0 28.0 29.0
A
mA
mA
A
A
V
V
V
0.14 0.17 0.20
5.10 5.30 5.50
2.5
2.1
1.60
mA
V
V
V
V
0.80 0.85 0.90
0.60 0.65
0.7
250
100
V
V
ns
ns
94.0 100
5
1
25
6.0
75
106
kHz
%
%
kHz
kHz
%
Leadtrend Technology Corporation
LD7752B-DS-00 June 2013
5
www.leadtrend.com.tw

5 Page





LD7752B arduino
LD7752B
Adjustable Grouping Frequency and Soft
Start on CT Pin
In order to prevent the acoustic noise from grouping
frequency Fg, adjust the external capacitance of CT pin
and the soft start time for it according to the below table.
The grouping frequency is limited from 600Hz to
1.80KHz
CCT (nF)
Grouping frequency
Fg (KHz)
Soft start time
Tss (mS)
22nF
33nF
1.2~1.8
0.8~1.3
3.0
3.8
47nF
0.6~1.0
6.0
Internal Slope Compensation
A fundamental issue of current mode control is the
stability problem when its duty-cycle is operated for
more than 50%. To stabilize the control loop, slope
compensation is required in the traditional UC384X
design by injecting the ramp signal from the RT/CT pin
through a coupling capacitor. Well, LD7752B requires
none of it since theres a built-in slope compensation
circuit to simplify the external circuit design.
On/Off Control
Pulling COMP pin below 1.6V will disable the gate
output pin of LD7752B immediately. The off mode will
be released soon as the pull-low signal is removed.
Dual-Oscillator Green-Mode Operation
There are various topologies for chips to meet
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 reduce the switching
frequency.
With LD proprietary dual-oscillator technique, the
green-mode frequency can be well controlled and
further to avoid the generation of audible noise.
Over Load Protection (OLP) - Auto
Recovery
To protect the circuit from being damaged in over-load,
short or open loop condition, the LD7752B is
implemented with smart OLP function. It also features
auto recovery function; see Fig. 11 for the waveform. If
in fault condition, the feedback system will force the
voltage loop enter toward the saturation and then pull
the voltage high over COMP pin (VCOMP). When the
VCOMP ramps up over OLP threshold of 4.5V and stays
for more than OLP delay time, the protection will be
activated and then turn off the gate output to stop the
switching of power circuit.
A divide-2 counter is implemented to reduce the
average power under OLP behavior. As soon as OLP is
activated, the output will be latched off and the divide-2
counter starts to count the numbers of UVLO(off). The
latch will be released when the 2nd UVLO(off) point is
tripped, then the output will recover to switch again.
With the protection mechanism, it minimizes the
average input power to control the components
temperature and stress within the safe operating area.
VCC
UVLO(on)
UVLO(off)
COMP
4.5V
OUT
OLP
2nd UVLO(off)
OLP Counter Reset
OLP Delay Time
OLP trip Level
t
t
Switching
Non-Switching
Fig. 11
Switching
t
Leadtrend Technology Corporation
LD7752B-DS-00 June 2013
11
www.leadtrend.com.tw

11 Page







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