Samsung UE32D4000 POWER SUPPLY - BN 44-00421A - fault finding - Schematic diagram - Fuse blowing - Using IC FAN7602 - TF12N65 - Led television repair and service
Category: LED Television Repair and service
Contents of this article
- Power supply schematic
- LED driver Schematic
- Troubleshooting
Samsung UE32D4000
Troublshooting
Fuse blowing:
If the fuse is blowing of continuously then check the flowing components
MOV VX801s – If it’s found short then replace it
Bridge rectifier BD810 – Check is any one of the diode is short or not
Check the IGBT TF12N65 For any short if found short replace it
Replace ICM801 FAN 7602
ABOUT FAN7602 PWM Controller
The
FAN7602 is a green current mode PWM controller. It is specially
designed for off-line adapter application, DVDP, VCR, LCD monitor
application, and auxiliary power supplies. The internal high-voltage
start-up switch and the burstmode operation reduce the power loss in
standby mode. Because of the internal start-up switch and the burst
mode, it is possible to supply 0.5W load, limiting the input power to
under 1W when the input line voltage is 265V AC. On no-load condition,
the input power is under 0.3W. The maximum power can be limited
constantly, regardless of the line voltage change, using the power limit
function. The switching frequency is internally fixed at 65kHz and the
frequency modulation technique reduces EMI. The FAN7602 includes various
protections for the system reliability and the internal soft-start
prevents the output voltage overshoot at start-up.
1
LUVP - Line Under-Voltage Protection Pin. This pin is used to protect
the set when the input voltage is lower than the rated input voltage
range.
2
Latch/Plimit - Latch Protection and Power Limit Pin. When the pin
voltage exceeds 4V, the latch protection works. The latch protection is
reset when the VCC voltage is lower than 5V. For the power limit
function, the Over-Current Protection (OCP) level decreases as the pin
voltage increases.
3 CS/FB - Current Sense and Feedback Pin. This pin is used to sense the MOSFET current
for the current mode PWM and OCP. The output voltage feedback information and
the current sense information are added using an external RC filter.
4
GND - Ground Pin. This pin is used for the ground potential of all the
pins. For proper oper ation, the signal ground and the power ground
should be separated.
5
OUT - Gate Drive Output Pin. This pin is an output pin to drive an
external MOSFET. The peak sourcing current is 450mA and the peak sinking
current is 600mA. For proper operation, the stray inductance in the
gate driving path must be minimized.
6 V CC Supply - Voltage Pin. IC operating current and MOSFET driving current are supplied using this pin.
7 NC - No Connection.
8
Vstr - Start-up Pin. This pin is used to supply IC operating current
during IC start-up. After start-up, the internal JFET is turned off to
reduce power loss.
SMPS NOTES
D.C.
to DC convertor and DC to AC converter belong to the category of
switched mode power supply (SMPS). The various types of voltage
regulator used in linear power supplies (LPS), fall in the category of
dissipative regulator, as they have a voltage control element usually
transistor or zener diode which dissipates power equal to the voltage
difference between an unregulated input voltage and a fixed supply
voltage multiplied by the current flowing through it. The switching
regulator acts as a continuously variable power converter and hence its
efficiency is negligibly affected by the voltage difference. hence the
switching regulator is also known as “non-dissipative regulator” in a
SMPS, The input DC supply is chopped at a higher frequency around 15 to
50KHz using an active device like the BJT power MOSFET or SCR and the
convertor transformer There are three basic switch regulators 1.Step
down or buck switching regulators. 2.Step up or boost switching
regulator. 3.Inverting type switching regulator
COMMON LED DRIVE WORKING
There
are large arrays of LEDs located behind the LCD panel in a typical LCD
TV LED. In this array are a large number of parallel channels of LEDs
connected in series depending on the size of the TV and the type of
backlighting, for example edge backlighting (less LEDs but more in
series) or direct backlighting (more LEDs in parallel) . The LED voltage
(VLED) is provided by the White LED Backlight Driver Board to each LED
channel and is regulated to a level needed by the highest voltage
required to maximize the light output of each LED string . Depending
upon the power supply requirements determined by the number of LEDs in
the string or grouping of parallel LED strings, the up-stream power
source for the LED backlight driver board may be a DC/DC step-up boost
converter, a DC/DC step-down converter or more commonly an AC/DC
converter . In the case where supply voltage is lower than
the required VLED, a step-up boost converter will be used . As an
example, a LED boost converter LED backlighting system will be described
in detail in this paper for a direct backlighting application, however
the theory of operation will also apply to both the step-down converter
and AC/DC converter situation .
High
brightness LEDs used in LCD backlighting require high LED current which
also equates to higher LED forward voltage . For example, if a user
wants to set the LED current to 80mA maximum, a minimum of 3 .65V
forward voltage must be provided to each LED in the string . If the
power supply can only provide 3 .6V to each LED, then the maximum LED
current is limited to 74mA .
POWER SUPPLY SCHEMATICS
LED DRIVER SCHEMATIC
