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CQ0765RT Schematic ( PDF Datasheet ) - Fairchild Semiconductor

Teilenummer CQ0765RT
Beschreibung FSCQ0765RT
Hersteller Fairchild Semiconductor
Logo Fairchild Semiconductor Logo 




Gesamt 24 Seiten
CQ0765RT Datasheet, Funktion
www.fairchildsemi.com
FSCQ0765RT
Green Mode Fairchild Power Switch (FPSTM) for
Quasi-Resonant Switching Converter
Features
• Optimized for Quasi-Resonant Converter (QRC)
• Advanced Burst-Mode operation for under 1 W standby
www.DataSheet4Up.coowmer consumption
• Pulse by Pulse Current Limit (5A)
• Over load protection (OLP) - Auto restart
• Over voltage protection (OVP) - Auto restart
• Abnormal Over Current Protection (AOCP) - Latch
• Internal Thermal Shutdown (TSD) - Latch
• Under Voltage Lock Out (UVLO) with hysteresis
• Low Startup Current (typical : 25uA)
• Low Operating Current (typical : 4mA)
• Internal High Voltage SenseFET
• Built-in Soft Start (20ms)
• Extended Quasi-resonant Switching for Wide Load Range
Application
• CTV
• DVD Receiver
• Audio Power Supply
OUTPUT POWER TABLE
PRODUCT
230VAC ±15%(2)
Open Frame(1)
85-265VAC
Open Frame(1)
FSCQ0765RT
100 W
85 W
FSCQ1265RT
170 W
140 W
FSCQ1565RT
210 W
170 W
Table 1. Notes: 1. Maximum practical continuous power
in an open frame design at 50°C ambient. 2. 230 VAC or
100/115 VAC with doubler.
Typical Circuit
Vo
Description
In general, Quasi-Resonant Converter (QRC) shows lower
EMI and higher power conversion efficiency compared to the
conventional hard switched converter with a fixed switching
frequency. Therefore, it is well suited for applications that are
sensitive to the noise, such as color TV and audio. The
FSCQ0765RT is an integrated Pulse Width Modulation
(PWM) controller and Sense FET specifically designed for
Quasi-resonant off-line Switch Mode Power Supplies
(SMPS) with minimal external components. The PWM
controller includes integrated fixed frequency oscillator, under
voltage lockout, leading edge blanking (LEB), optimized gate
driver, internal soft start, temperature compensated precise
current sources for a loop compensation and self protection
circuitry. Compared with discrete MOSFET and PWM
controller solution, it can reduce total cost, component count,
size and weight simultaneously increasing efficiency, produc-
tivity, and system reliability. This device is a basic platform
well suited for cost effective designs of Quasi resonant
switching flyback converters.
AC
IN
Sync
FSCQ0765RT
PWM
VFB Vcc
Drain
GND
Figure 1. Typical Flyback Application
©2004 Fairchild Semiconductor Corporation
Rev.1.0.1






CQ0765RT Datasheet, Funktion
FSCQ0765RT
Electrical Characteristics (Continued)
(Ta=25°C unless otherwise specified)
Parameter
UVLO SECTION
Vcc Start Threshold Voltage
Vcc Stop Threshold Voltage
SENSEFET SECTION
Drain To PKG Breakdown Voltage (Note4)
www.DataSheet4UD.craoimn To Source Breakdown Voltage
Drain To Source Leakage Current
OSCILLATOR SECTION
Initial Frequency
Voltage Stability
Temperature Stability (Note2)
Maximum Duty Cycle
Minimum Duty Cycle
FEEDBACK SECTION
Feedback Source Current
Shutdown Feedback Voltage
Shutdown Delay Current
PROTECTION SECTION
Over Voltage Protection
Over Current Latch Voltage (Note2)
Thermal Shutdown Temp (Note4)
Symbol
Condition
Min. Typ. Max. Unit
VSTART VFB = GND
VSTOP VFB = GND
14 15 16
8 9 10
V
V
BVpkg
BVdss
Idss
60HZ AC, Ta = 25°C
3500
Ta = 25°C
650
Vdrain = 400V, Ta = 25°C -
-
-
-
-V
-V
200 uA
FOSC
FSTABLE
FOSC
DMAX
DMIN
-
12V Vcc 23V
-25°C Ta 85°C
-
-
18 20 22 kHz
0 1 3%
0 ±5 ±10 %
92 95 98 %
- - 0%
IFB
VSD
IDELAY
VFB = 0.8V
Vfb 6.9V
VFB = 5V
0.5 0.65 0.8 mA
7.0 7.5 8.0 V
4 5 6 µA
VOVP
VOCL
TSD
Vsync 11V
-
-
11 12 13 V
0.9 1.0 1.1 V
140 - °C
Note:
1. These parameters is the current flowing in the Control IC.
2. These parameters, although guaranteed, are tested only in EDS (wafer test) process.
3. These parameters indicate Inductor Current.
4. These parameters, although guaranteed at the design, are not tested in mass production.
6

6 Page









CQ0765RT pdf, datenblatt
FSCQ0765RT
Functional Description
1. Startup : Figure 4 shows the typical startup circuit and
transformer auxiliary winding for FSCQ0765RT application.
Before FSCQ0765RT begins switching, FSCQ0765RT
consumes only startup current (typically 25uA) and the
current supplied from the AC line charges the external
capacitor (Ca1) that is connected to the Vcc pin. When Vcc
reaches start voltage of 15V (VSTART), FSCQ0765RT begins
switching, and the current consumed by FSCQ0765RT
increases to 4mA. Then, FSCQ0765RT continues its normal
switching operation and the power required for this device is
www.DataSheets4uUp.pcolimed from the transformer auxiliary winding, unless Vcc
drops below the stop voltage of 9V (VSTOP). To guarantee the
stable operation of the control IC, Vcc has under voltage
lockout (UVLO) with 6V hysteresis. Figure 5 shows the
relation between the FSCQ0765RT operating supply current
and the supply voltage (Vcc).
The minimum average of the current supplied from the AC is
given by
Is
u
a
p
vg
=
-----2--------V-π---a---c--m-----i-n-
V-----s-2--t-a---r--t
----1-----
Rstr
where Vacmin is the minimum input voltage, Vstart is the
FSCQ0765RT start voltage (15V) and Rstr is the startup
resistor. The startup resistor should be chosen so that Isupavg
is larger than the maximum startup current (50uA).
Once the resistor value is determined, the maximum loss in
the startup resistor is obtained as
Loss
=
----1-----
Rstr
(---V----a---c---m----a---x---)--2----+------V----s---t-a---r--t--2
2
2--------2--------V-----s--t--a-π--r--t------V----a---c--m-----a---x
CDC
AC line
(Va
min
c
- Vacmax)
1N4007
Rstr
Isup
Vcc
FSCQ0765RT
Ca1
Da
Ca2
Figure 4. Startup circuit
Icc
4mA
Power Down
Power Up
25uA
Vstop=9V Vstart=15V
Vcc
Vz
Figure 5. Relation between operating supply current and
Vcc voltage
where Vacmax is the maximum input voltage. The startup
resistor should have proper rated dissipation wattage.
2. Synchronization : FSCQ0765RT employs quasi-resonant
switching technique to minimize the switching noise and loss.
In this technique, a capacitor (Cr) is added between the
MOSFET drain and source as shown in Figure 6. The basic
waveforms of quasi-resonant converter are shown in Figure
7. The external capacitor lowers the rising slop of drain
voltage to reduce the EMI caused when the MOSFET turns
off. In order to minimize the MOSFET switching loss, the
MOSFET should be turned on when the drain voltage reaches
its minimum value as shown in Figure 7.
CDC
+
VDC
-
Np
Lm
Sync
Drain
Cr
Ids
+
Vds
-
GND
Vcc
Ca1
Vco
Rcc
Ca2
Da
DSY
Na
RSY1
Ns
CSY
RSY2
Vo
Figure 6. Synchronization circuit
12

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