Datenblatt-pdf.com


LD7577 Schematic ( PDF Datasheet ) - Leadtrend

Teilenummer LD7577
Beschreibung High Voltage Green-Mode PWM Controller
Hersteller Leadtrend
Logo Leadtrend Logo 




Gesamt 18 Seiten
LD7577 Datasheet, Funktion
LD7577
1/15/2009
High Voltage Green-Mode PWM Controller with
Brown-Out Protection
Rev. 01
General Description
The LD7577 integrates several functions of protections, and
EMI-improved solution in SOP-8 package. It minimizes 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, it features more protections like OLP (Over Load
Protection), OVP (Over Voltage Protection), and brownout
protection to prevent the circuit from being damaged under
abnormal conditions.
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 Slope Compensation
z OVP (Over Voltage Protection) on Vcc Pin
z AC Input OVP (Over Voltage Protection)
z OLP (Over Load Protection)
z Precision 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 EMI
input Filter
*
HV VCC OUT
BNO
LD7577
CS
GND COMP
*
*See Application Information
Leadtrend Technology Corporation
LD7577-DS-01 January 2009
1
www.leadtrend.com.tw
photocoupler
TL431






LD7577 Datasheet, Funktion
Electrical Characteristics
(TA = +25oC unless otherwise stated, VCC=15.0V)
Brownout Protection & Line Compensation (BNO Pin)
Brownout Turn-On Trip Level
Brownout Turn-off Trip Level
Line Voltage OVP-Off Level
Line Voltage OVP-On Level
Saturation Voltage on BNO Pin
Input impedance
IBNO=1.5μA
Gate Drive Output (OUT Pin)
Output Low Level
VCC=15V, Io=20mA
Output High Level
VCC=15V, Io=20mA
Rising Time
Load Capacitance=1000pF
Falling Time
Load Capacitance=1000pF
OLP (Over Load Protection)
OLP Trip Level
OLP Delay Time
FS=65KHz
De_Latch VCC Level
PDR (Power Down Reset)
LD7577
1.00
0.90
3.90
3.70
5.1
1.05
0.95
4.00
3.80
6
1.10
1.00
4.10
3.90
V
V
V
V
V
MΩ
1V
9V
100 nS
30 nS
5.0 V
30 mS
8.0 V
Leadtrend Technology Corporation
LD7577-DS-01 January 2009
6
www.leadtrend.com.tw

6 Page









LD7577 pdf, datenblatt
LD7577
Fig. 18
Fig. 17
OVP (Over Voltage Protection) on Vcc
The VGS ratings of the nowadays power MOSFETs are
mostly with 30V maximum. To prevent the VGS from fault
condition, the LD7577 is implemented with over-voltage
protection on Vcc. As long as the Vcc voltage is higher
than OVP threshold voltage, the output gate drive circuit will
be shut down, thus to stop the switching of the power
MOSFET until the next UVLO(ON).
The Vcc OVP function in the LD7577 is an auto-recovery
type protection. If the OVP condition, usually caused by
the feedback loop opened, is not released, the Vcc will trip
to the OVP level again, re-shutting down the output. The
Vcc waveform in Fig. 18 shows this auto-recovery type
protection, presenting a hiccup mode.
On the other hand, the removal of the OVP condition should
render the Vcc level back to normal level, causing the output
automatically returning to the normal operation.
Brownout Protection & Line voltage OVP
(Over voltage protection)
The LD7577 is programmable to set the brownout protection
point and the line voltage OVP point though BNO pin.
The voltage across the BNO pin is proportional to the bulk
capacitor voltage, referred as the line voltage. A brownout
comparator is implemented to detect the abnormal line
condition. As soon as the condition is detected, it will shut
down the controller to prevent the damage. Figure 19
shows the operation. When VBNO falls below 0.95V, the
gate output will be kept off even Vcc has already achieved
UVLO(ON). It therefore makes Vcc hiccup between UVLO(ON)
and UVLO(OFF). Unless the line voltage is large enough to
pull VBNO larger than 1.05V, the gate output will not start
switching even when the next UVLO(ON) is tripped. A
hysteresis is implemented to prevent the false trigger during
turn-on and turn-off.
The comparator built in BNO will disable switching from
Gate-out as soon as it detects excessive high line voltage
and BNO voltage over 4.0V. VCC will then operate in hiccup
mode between UVLO-on and UVLO-off. The Gate-out will
not resume switching until VBNO falls below 3.8V.
Therefore, it can prevent excessive high line voltage from
damaging the external components. Fig. 20 shows the
operation.
Leadtrend Technology Corporation
LD7577-DS-01 January 2009
12
www.leadtrend.com.tw

12 Page





SeitenGesamt 18 Seiten
PDF Download[ LD7577 Schematic.PDF ]

Link teilen




Besondere Datenblatt

TeilenummerBeschreibungHersteller
LD7575Green-Mode PWM ControllerLeadtrend
Leadtrend
LD7575AGreen-Mode PWM ControllerLeadtrend
Leadtrend
LD7575BGreen-Mode PWM ControllerLeadtrend
Leadtrend
LD7576Green-Mode PWM ControllerLeadtrend
Leadtrend
LD7576AGreen-Mode PWM ControllerLeadtrend
Leadtrend

TeilenummerBeschreibungHersteller
CD40175BC

Hex D-Type Flip-Flop / Quad D-Type Flip-Flop.

Fairchild Semiconductor
Fairchild Semiconductor
KTD1146

EPITAXIAL PLANAR NPN TRANSISTOR.

KEC
KEC


www.Datenblatt-PDF.com       |      2020       |      Kontakt     |      Suche