Toshiba PJTV9 Schematic
SERVICE TRAINING
1997 G-SERIES
COLOR TELEVISION
POWER SUPPLY
AND SHUTDOWN
TROUBLESHOOTING
GUIDE
Contents
POWER SUPPLY CIRCUIT.......................................1
1. OUTLINE OF SYSTEM..................................................................................................................... 2
2. STAND-BY POWER SUPPLY........................................................................................................... 3
3. MAIN POWER SUPPLY.................................................................................................................... 3
4. OUTLINE OF THE CURRENT RESONANT TYPE SUPPLY..................................................... 4
5. FUNDAMENTAL THEORY OF LC SERIES RESONANT CIRCUIT........................................ 4
6. MAIN SUPPLY ACTUAL OPERATION ......................................................................................... 6
7. MAIN POWER SUPPLY TROUBLESHOOTING GUIDE .......................................................... 10
8. SCAN DRIVEN SUPPLY ................................................................................................................. 12
10. SUB POWER SUPPLY.................................................................................................................... 14
11. SUB-POWER SUPPLY TROUBLESHOOTING GUIDE............................................................ 16
SHUT DOWN CIRCUITS.........................................17
1. SUMMARY OF SHUT DOWN CIRCUITS. ................................................................................... 18
2. POWER SHUT DOWN TROUBLESHOOTING GUIDE............................................................ 20
3. +30 Volt Over Voltage Protect. ......................................................................................................... 21
4. +15V Over Voltage Protect. .............................................................................................................. 21
5. +30 V Over Current Protect. ............................................................................................................ 22
6. +15V Over Current Protect. ............................................................................................................. 22
7. -15V Over Current Protect. .............................................................................................................. 23
8. +35V Over Current Protect. ............................................................................................................. 23
9. +/-15V Under Voltage Protect........................................................................................................... 24
10. 200V Under Voltage Protect. .......................................................................................................... 25
11. X-Ray (High Voltage) Protect. ........................................................................................................ 25
12. +125V Over Current Protect. ......................................................................................................... 26
POWER SUPPLY CIRCUIT
1
1. Outline of system
The block diagram of the power supply is shown in Fig.
1. The N7 chassis consists of the standby power supply
which supplies power to the microcomputer, and the
main power supply which supplies power to the horizontal output and audio output. This chassis also has a
scan driven supply from the flyback which supplies
power to the vertical output, video output, and signal
processing circuts.
The main supply is a current resonating type supply. It
is small in size, highly efficient and reliable.
F801 T801 T802
SR81
Q801
VOLTAGE CONTROL
STR-Z3201
Q843
SW
Q830
SW
D802~D805
Q802
VOLTAGE CONTROL
STR57041
T840
POWER
TRANS.
TPW
1549AZ
D801
D840
F860
R861
Q862
PHOTO COUPLER
F850
Q840
+12V
REG.
T862
CONVERTER
TPW
3332AS
R883
T888
Fig. 1 Power supply block diagram.
CONVERTER
TPW
3330AM
+5V-1 (MICROCOMPUTER)
+12V
+38V
TRANS.
Q430
+26.5V
F851
+15V
TRANS.
LOW VOLTAGE PROTECTOR
-15V
Q840
REG.
Q840
REG.
Q840
REG.
5V-2 (TUNER, COMB, V/C/D etc.)
5V-3 (PIP, ESD/C.C/RGB. SW)
9V-2 (COMB, DSP, CRT-D etc.)
AUDIO OUT
+9V
H.Vcc (V/C/D)
R470
R479
1
Z801
PROTECTOR
H1C1019
3
Q853 Q854
C471
+13(+125V)
R101
+
D471
R7782
O.C.P
Q768
O.C.P
Q759
O.C.P
Q762
R472
R7750
R7765
F.B.T. V.M
+32V (TUNER)
F.B.T.(HEATER)
200V L.V.P. 35V O.C.P
CONVERGENCE
CIRCUIT
F470
R471
2
X-RAY
13
14
16
2
2. Stand-by Power Supply
3. Main Power Supply
The stand-by power supply supplies 12Vdc to the relay SR81, 5V to the microprocessor, 5V to the protect
IC, and a reset 5V to the microprocessor. T840 supplies a low AC signal to D840. D840 rectifies the signal and C840 filters it to produce 12Vdc. The 12V is
applied to Q840. Q840 outputs a regulated 5V on pin 5
and supplies a reset 5V at pin 4. Reset occurs when
power is first applied to Q840. The 5V on pin 5 comes
up first while pin 4 stays low. This is the reset condition. After C843 fully charges, pin 4 goes to 5V for
normal operation.
* Troubleshooting Tip:
A loss of the 5 V or reset 5V will prevent the
microprocessor from operating.
F801 D899 C801
Surge
T801
1. Main Power Rectifier Cir cuit
D801 and C810, the rectifier and filter for the main
switching supply, produce 165V. R810 suppresses the
rush current at turn on. SR81 is a relay that turns on the
main supply. The relay is controlled by the microprocessor through the relay drivers: QB30 and Q843.
* Troubleshooting Tip:
Because the microprocessor controls the relay, the
main power supply may not turn on if the microprocessor does not operate properly.
L901
THERMISTOR
+5V-1
Q843
D801
QB30
C810
R810
MICOM
POWER
165V DC
Rectified
output
SR81
C840
T840 D840
C843
Q840
1
2
5
4
3
Fig. 2 Rectifying circuit and standby power
+5V (to MICOM)
Reset
C842
3
4. Outline of the Current Resonant Type Supply
Fig. 3 shows the block diagram for the current resonant
switch mode power supply. The primary side is an LC
series circuit. It consists of the primary winding of the
transformer and a resonant capacitor in series. Two
power MOS FET’s in a push-pull configuration drive
the primary side of the transformer.
The switching action on the primary side of the transformer produces the main B+ on the secondary side.
The main B+ is regulated by negative feedback. The
main B+ is fed into an error amplifier and outputted to a
photo coupler. The output of the photo coupler is applied to the primary side of the power supply to control
the switching speed.
Oscillator
DRIVE
Fig. 3 Basic configuration
5. Fundamental Theory of LC Series Resonant Circuit
The LC series resonant switch mode power supply is a
frequency regulated power supply oper ating above resonance. When the the load increases on the secondary
side of the transformer, the frequency decreases (operates closer to resonance) and the current increases. Conversely , when the load decreases, the frequency increases
and the current decreases.
B+
ERROR
AMP
PHOTO
COUPLER
VL (v)
Increased Load
Decreased Load
e
Fig. 4 LC series resonant circuit
VL
e
Resonant point
1
f=
LC
2p
Normal
Operating
Frequency
Frequency
Fig. 5 Characteristics
4
STR-Z415, STR-Z415, and STR-Z4201 Block Diagram
CD
OC
11
Vcc VB
TSD
8
DELAY LATCH REF
OC
7
Css
OVP
OSC
CONTROL
5
CONT
6
Fmax CT
START
DRI Vcc
915
OSC
10
Logic
34
DT GND
2
14
12
1
VIN
OUT
COM
Pin No. Symbol Function
1VIN Half bridge power input
2 Gnd Ground
3 DT Dead time resistor terminal
4 CT Oscillator capacitor terminal
5 CONT Oscillator control terminal
6FMAX Maximum frequency determining resistor terminal
7CSS Soft start capacitor terminal
8 CD Capacitor for delay latch: ON-OFF terminal
9VCC Power source terminal for control section
10 DRI VCC Gate drive power supply output terminal
11 OC Over current detect terminal
12 COM Half bridge GND
14 OUT Half bridge output
15 V
B High side gate drive power source input
Table 2 Pin function
5
6. Main Supply Actual operation
Refer to Figure 7 diagram and waveforms.
1. Start-up
When power is applied to the set, a start-up pulse of
16V is applied to pin 9 of IC Q801. At the same time,
the charging of C869 (pin 8) induces a delay to the internal latch circuit to prevent the Over Voltage Protect
(OVP) from engaging, and C866 (pin 7) sets the switching frequency high to reduce the surge current. After
the initial start-up, the circuit operates at its nominal
frequency (70-80 kHz), and the Drive Circuit (see page
9) supplys 17V to pin 9.
2. Output switching element
Two power MOSFETs in push-pull configuration, op-
erate the switching. The on-off timing of each MOSFET is controlled by the logic inside Q801. To avoid
shorting the MOSFET s, they are never turned on at the
same time. Between the time one transistor turns off
and the other turns on, both MOSFETs are of f. This off
time is called dead time, and is determined by
R867(pin3).
3. Basic Oscillation
5.CD terminal (Pin 8) - Latch Delay
The Latch circuit shuts the power supply off (shut-down)
when a fault is detected. Shut-down occurs by detecting
errors from the following:
• Over voltage protection (OVP) circuit
• Thermal shock detection (TSD) circuit
• Over current protection (OCP) circuit
• Loss of and no recovery of Main B+
The charging time of capacitor C869 connected to the
CD terminal (Pin 8) is used to delay the operation of the
latch circuit when power is initially applied. If the unit
goes into shut-down, temporarily remove AC power to
reset the latch circuit.
7.OC terminal (Pin 11) - Over Current Detect
This is to detect over-current in the LC series resonant
circuit.
8.Over voltage protection (OVP) circuit
If the Vcc terminal (Pin 9) exceeds 22V (typical), the
latch circuit is engaged (shutdown) .
The frequency of the internal oscillator is determined
by the charge and discharge of capacitor C862 (pin 4) ,
and is controlled by the feedback into pin 5 through
the Oscillator control block. The oscillator generates a
ramp waveform at Pin 4. The ramp waveform charges
up to 4 V (typical) and discharges to about 2.5 V. The
charging time is the output-on period for one of the
MOSFETs, and the discharging time is the off period
for both MOSFETs (see OSC OUT SIGNAL waveform
of Figure 7). The lowest oscillation frequency is determined by capacitor C862 and resistor R867.
4. Frequency Control
Current flowing out of the CONT terminal (Pin 5) var-
ies the charging time of oscillator capacitor C862, which
in turn, controls the frequency of the Output (Pin 14)
signal. The control current is determined by the
photocoupler. The photocoupler phototransister side current is determined by the feedback current of the photodiode side. The photodiode current is determined by
the error amp inside of Z801, which is monitoring the
+125V source. Thus, the terminal current (CONT) corresponds to the feedback from the +125V output.
9.Thermal shock detection (TSD) circuit
This is to make the Latch circuit operate when the IC's
internal temperature exceeds 150°C.
6
Actual Circuit
VIN
(AC)
R810
Q801
C810
C873
D873
R861
Vcc
R862
9
10
D862
T862
D864
R871
#2
V
B
15
#10
D883
MAIN OUTPUT
1
V
TSD
OVP
START
IN
R872
14
12
OUT
COM
C865
C863
D875
C871
R870
7
CD
8
DELAY
LATCH
REF
Logic
11
OC
C869
Css
C866
OC
7
CONT
Q862
OSC
CONTROL
5
Fmax
R864
6
OSC
CT DT
R868
34
D872
GND
2
C862
R867
R866
C867
C868
C874
C870
#3
#4
#5
#12
#11
#14
#13
#15
D884
D855
D886
C884
Q862
C891
R891
Audio
output
R883
Z801
ERROR AMP
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