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R7711A Schematic ( PDF Datasheet ) - Richtek

Teilenummer R7711A
Beschreibung Primary Feedback CC/CV PWM Controller
Hersteller Richtek
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Gesamt 19 Seiten
R7711A Datasheet, Funktion
®
R7711A
Primary Feedback CC/CV PWM Controller for Flyback
Converters
General Description
Features
The R7711A is a current mode PWM controller which
includes primary side voltage feedback technology. It
controls the output voltage and current accurately without
shunt regulator and opto-coupler on secondary side to
reduce the part count and save costs.
The R7711A is designed especially for low power
applications, such as chargers for cell phones, PDAs,
and other mobile products. Complete protections are
provided, such as output Under- Voltage Protection, output
Over-Voltage Protection, VDD Over-Voltage Protection,
Over-Temperature Protection, and Secondary Rectifier
Short-circuit Protection. The ultra low start-up current and
operating current of the R7711A achieves low power
consumption in standby mode. The R7711A supports burst
switching green mode operation to meet CEC regulations
and Energy-Star requirements.
Programmable Primary-Side CC/CV Regulation
Low No Load Input Power (<30mW at 230VAC)
Burst Switching Green Mode PWM Operation
Low Start-up Current (<10mA)
Easy EMI Solution
Built-in Jittering Frequency
Built-in Soft Gate Driver
Programmable Cable Drop Compensation
Adjustable Propagation Delay Compensation
VDD Over-Voltage Protection (VDDOVP)
Output Over-Voltage Protection (OVP)
Output Under-Voltage Protection (UVP)
Secondary Rectifier Short-Circuit Protection (SRSP)
Internal Over-Temperature Protection (OTP)
RoHS Compliant and Halogen Free
Applications
Switching AC/DC Adaptor and Battery Charger
DVD Open Frame Power Supply
STB Power
Cell Phone Charger
Networking Power Supply
Simplified Application Circuit
L
AC Mains
(90V to 265V)
N
VDD DMAG
R7711A
COMP GATE
CS
GND
2
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
R7711A-06 May 2014
VOUT
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1






R7711A Datasheet, Funktion
R7711A
Output Under-Voltage Protection (UVP)
The output UVP is designed to protect the converter from
the output short-circuit conditions. Once the feedback
voltage (VSH_DMAG), sampled on the DMAG pin, is below
the voltage threshold (VTH_UVP = 1.2V typ.), a built-in 11-
bit digital timer performs a UVP debounce time (2048
switching cycles = about 30ms) before issuing the UVP
signal. The UVP signal turns off the converter to prevent
the loading device and converter from being damaged. The
R7711A works in hiccup mode until the fault is removed.
Over-Temperature Protection (OTP)
The built-in OTP function continuously monitors the
junction temperature (TJ) of the IC itself. Once the TJ
exceeds the over-temperature level (TOTP = 150°C typ.),
the OTP signal turns off the converter and prevents the IC
itself from suffering thermal stress and permanent damage.
It's not suggested to use the function as a precise OTP.
The R7711A works in hiccup mode until the fault is
removed.
Secondary Rectifier Short-circuit Protection (SRSP)
The R7711A is equipped with an extra over-current
protection (OCP) against secondary rectifier short-circuit
conditions in flyback converter. When the secondary
rectifier is damaged by short-circuit, the transformer
operates in saturation area and huge current stress occurs
on the main switch. When the VCS reaches the OCP
voltage threshold (VTH_OCP = 1.7V typ.), the R7711A shuts
down the converter after the debounce time of a few cycles.
The R7711A works in hiccup mode until the fault is
removed.
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
www.richtek.com
6
is a registered trademark of Richtek Technology Corporation.
R7711A-06 May 2014

6 Page









R7711A pdf, datenblatt
R7711A
Oscillator Frequency vs. COMP Voltage
80
40° C
70
60 40°C
120°C
50
40
30
20
10
0
0123456
COMP Voltage (V)
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
www.richtek.com
12
is a registered trademark of Richtek Technology Corporation.
R7711A-06 May 2014

12 Page





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