SECTION 3 HOW TO WORK WITH FINAL SMPS FET by sisusy

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									SECTION 3 HOW TO WORK WITH FINAL SMPS FET

If you are unfamiliar with the blocks in SMPS circuit, you should first read the first article of this
SMPS.
Many a friend of mine who complained SMPS circuit of this type, ranging from the FET which
can not be installed ampe who spent the FET to 5 seeds, not only FETnya are burning, but like
firecrackers rentengan when the SMPS is attempted, thour-thuorr-thuorr.
SMPS scheme are:

How it works largely the same range as that reviewed in the previous article, the difference in
error amp circuit is used. Here, the authors examine only the circuit blocks on top of its functions
only.
1. Line filter and rectifier: consists of R536, C532 and M502. Then rectified and filtered by the
circuit consisting of Main Rectifier D519, C527, C528, C529, c530 and C525 (220uF/400) to
create a B + voltage of 308V.
2. Start up circuit: B + voltage of 308V after insufficient, the voltage is inhibited by R531 and
R532 later by the zener (D518 6V2) voltage is limited to 6V2 and 6V2 voltage is used as a
voltage Startup via R528 10K (18K/22K on some models). Voltage is sufficient to trigger /
switching IC501 9NK70 (on some models use FS7UM) to initiate the self oscilation.
3. Snubber circuit: consists of C524 (2n2/1n 2kV) and R533 (2R2).
4. Error Amp: consists of 2 error amp circuit, each used for standby and when ON. Error Amp
while standby using ZD517 (2V), R522 (680), T506 (C945) and C521 (10N). While the Error
Amp when ON is IC503 (TL431), R506 (100K), RT501 (22K), C511 (220P), R505 (2K4), R504
(470K), R503 (100K) and C510 (2n7). Error Amp will compare the output voltage of +115 V B
(after going through R506 and RT501) with internal reference voltage IC TL431.
5. The series Over Current Protection (OCP) consists of T507 (A1015), T508 (C1815), R525
(100), C523 (18n) and ZD521 (13V). Meanwhile, R526, R527 is used for adjustment of the
sensitivity of the OCP as well as the negative voltage path leading to the IC501 (final power).
6. The series of critical frequency / pulse oscillation consists of L507, R523 (1K2) and C522
(3n3) that keep the oscillation frequency remains at work.
More About Error Amp when ON

1. Secondary voltage of 14V supply optocoupler anode leg through R542 (220), while leg
optocoupler cathode supplied by Error Amp circuit composed of IC503 (TL431), R506 (100K),
RT501 (22K), C511 (220P), R505 (2K4), R504 (470K), R503 (100K) and C510 (2n7). Error
Amp will compare the output voltage of +115 V B (after going through R506 and RT501) with
IC TL431's internal reference voltage (2.5 V = according to the datasheet) that the error voltage
is then fed to the cathode leg optocoupler.
2. The voltage difference is present in the diode / input optocoupler (PC817) led optocoupler
voltage from collector to deliver emitornya feet (PC817 opto legs in order are, 1: anode, 2:
cathode, 3: emitter, 4: collector). The voltage delivered by the PC817 comes from the secondary
winding on the non-isolated areas. Voltage serves as the error voltage and the voltage driver is
then used to control the oscillation / work from the primary circuit.
Standby System

1. With the voltage of 14V, automatic regulator circuit (T503 C2236) also issued a 5V standby
voltage through D522 1N4002. This is a standby voltage mains voltage used by the IC program
on standby and working (ON).
2. When the TV is turned off by remote (made standby), up the voltage on the standby path that
led to the T505 base (C2235). Be in a state of the transistor switch (E and C are connected).
Since E and C are connected, then the anode D514 also directly connected to ground (-),
resulting in an error voltage of TL431 missing / short-circuit to ground by the diode (see the
arrow direction diode). Since opto no longer receive the bias voltage, then the primary circuit
will go into standby mode. When the standby mode, the output of the transformer secondary
'accidentally' made down drastically. B +115 read around 25V, 50V into 8-10V and 14V to about
2V. Then 5V for standby is taken from where?
3. In addition to joining the shorted voltage error of the TL431, T505 also gives a negative bias
on the tr T504 (A1023) through R516 (2k2) to make the T504 to be in state tr switches. When
the T504 switches, tr is connecting voltage 50V (when standby read about 8 s / d 10V), which
finally is the voltage (which 8volan) T503 is used to supply voltage (5V standby regulator).
Conversely, when in the ON again, taken from the 14V voltage T503, T504 and tr (A1023) re
not in a state switch (not used when ON).
Repair Tip

1. Try / test SMPS SMPS should use the means test as reviewed in the article How to Safely Test
the Power Supply (SMPS).

								
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