®
RT7781
PowerZeroTM Series PWM Flyback Controller
Features
General Description
PowerZeroTM Technology
Integrated 700V Start-Up Device
Brown-In and Brown-Out
The RT7781 is a series of high-performance current mode
PWM controllers with Richtek proprietary PowerZeroTM
technology. The PowerZeroTM provides an excellent green
power solution, especially under light-load and no-load
conditions. The integrated high-voltage device provides
fast start-up function without external start-up resistors.
It also features brown-in and brown-out detection.
Low No-Load Input Power (<50mW) (RT7781G/L/A/C)
Low No-Load Input Power (<30mW) (RT7781T)
Accurate Over Load Protection
Driver Capability : 400mA/−400mA
PRO Pin for Arbitrary External Protection
(RT7781G/L/A/T)
The RT7781 offers complete protection functions such as
internal Over-Temperature Protection (OTP), Over-Load
Protection (OLP) and VDDOver-Voltage Protection (OVP).
It also features Secondary Rectifier Short-circuit
Protection (SRSP) and Current Sensing pin (CS) open-
circuit protection. Due to these protections, design of
power supply unit becomes simple and reliable.
ACD Pin for TV Application (RT7781C)
Disable Mode for 30mW Solution (RT7781T)
Jittering Frequency
Soft Driving for Reducing EMI Noise
VDD Over Voltage Protection
Internal Over Temperature Protection
Secondary Rectifier Short Protection
CS Pin Open Protection
The RT7781 provides several versions, shown in the
RT7781 version table, for various applications. It is targeted
for cost-effective and compact power supply units such
as NB adaptors.
RoHS Compliant and Halogen Free
Applications
NBAdaptor
Marking Information
RT7781xGS : Product Number
SwitchingAC/DCAdaptor with LowNo-Load Input Power
TV and MonitorApplications
Open Frame Power Supply
RT7781x
GSYMDNN
x :G/L/A/T/C
YMDNN : Date Code
Simplified Application Circuit
V
OUT+
AC Mains
(90V to 265V)
V
OUT-
RT7781
VDD
OPTO
HV
PRO
GATE
OPTO
COMP
CS
GND
Copyright 2014 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS7781-03 April 2014
www.richtek.com
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RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]