Toshiba TP43H60, TP43H95, TP50H15, TP50H50, TP50H60 Service Manual
...
Projection Televisions
Main Power Supply
&
Complete Shutdown Troubleshooting Guide
TP43H60
TP43H95
TP50H15
TP50H50
TP50H60
TP50H64
TP50H95
TP55H60
TP55H64
TP55H95
TP61H60
TZ43V61
TZ50V51
TZ50V61
TZ55V61
TZ61V61
Contents
Main Power Supply ................. 3
Overall Block Diagram.................................................................................................4
Operation ...................................................................................................................... 5
Surge Protection Relay. ...............................................................................................6
Start-up and Over Voltage Protect..............................................................................6
Logic and Drivers.........................................................................................................7
Oscillator.......................................................................................................................7
Oscillator Control.........................................................................................................8
Latch..............................................................................................................................8
Thermal Shock Detection Block .................................................................................8
Over Current Protection ..............................................................................................8
Soft Start .......................................................................................................................9
Resonate Correction....................................................................................................9
Additional Information on Q801................................................................................10
Block Diagram of Q801.............................................................................................11
Troubleshooting Flowchart .......................................................................................12
Shutdown Guide.................... 14
Summary of Shutdown Circuits................................................................................15
Peak-Response Meter. ...............................................................................................16
No Peak-Response Meter. .........................................................................................16
Monitoring Circuits ....................................................................................................17
X-Ray Protect..............................................................................................................17
+125V Over Current Protect. .....................................................................................18
+36V Over Current Protect. .......................................................................................19
+18V and – 18V Over Current Protect. .....................................................................20
+35V Over Current Protect. .......................................................................................20
+ 9V Under Voltage Protect .......................................................................................21
+ 35 Under Voltage Protect........................................................................................21
200V Under Voltage Protect. .....................................................................................21
Troubleshooting Flowchart .......................................................................................22
Main Power Supply
3
Overall Block Diagram
Figure 1 is the overall block diagram of the main switching power supply and the standby power supply. The
standby supply is always active when the television is
plugged into an A C line source. This supply deli vers a
5V VDD and a reset 5V to the microprocessor to k eep
the microprocessor functioning at all times, even when
the television is not operating. T ransformer T840 isolates the standby supply from the live ground, and D840
is a full-wave bridge rectifier that supplies 12Vdc to
voltage regulator Q840 and relay SR81 (connection
not shown). When the microprocessor receives an ON
command from the remote control or power key, on
the front of the television, it sends 5V to relay drivers
Stand-By Supply
QB30 and Q843 to close relay SR81.
When the relay closes, the A C line input is applied directly to the main power supply. The supply starts to
operate and turns ON the television. D801 is the fullwave bridge rectifier for the main power supply. It
rectifies the 120V AC line input to 165Vdc and applies it to the main switching IC, Q801. The primary
side of the power supply is not isolated and, therefore,
is at live ground. Detailed explanations of the main
power supply are covered in the remainder of this section.
Troubleshooting Tip:
If SR81 never closes, check the standby power supply .
Both the 5V VDD and the reset 5V are mandatory for
the microprocessor to operate.
Rectifier &
Isolation Trans.
D840
T840
AC Line
Input
5V=Relay On
0V=Relay Off
QB30
Q843
SR81
Relay
Stand-by
Regulator
Q840
From Shutdown
Relay Drivers
Rectifier
D801
+5-1
165V
5V
Main Switching IC
Q801
Microprocessor
VDD
5V
Reset
QA01
Feedback
4
7
C870
Photo
Coupler
Q862
Main Power Supply
Rectifiers
11
D856
9
D855
9
D851
10
D854
12
D886
13
D889
14
D891
15
D894
16
D882
17
D884
T862
Error
Amp.
+36
+18
-18
+38
+12
+125
Z801
Q760
Q754
Q755
Q756
Q430
Q832
Q830
Q831
D101
30V
Reg.
5V
Reg.
9V
Reg.
-9V
Reg.
9V
Reg.
9V
Reg.
5V&9V
Reg.
5V
Reg.
32V
Reg.
To Q752
Conv. Output
To Q752 & Q751
Conv. Outputs
To Digital Conv. PC,
Q764 & Q767
To Q752
Conv. Output
To Q752 & Q751
Conv. Outputs
To Digital Conv. PC,
To Q601 Audio Out
To Q501
Horizontal Start-up
To Shutdown & Surge protect:
Q846,SR82,Q757, & Q758
+9-2 To Numerous Circuits
+5-2 To Numerous Circuits
+9-1 To Numerous Circuits
+5-3 To PIP Module & QBB3
To Horizontal Output
To Tuner(s)
Reg.= Regulator
Conv.= Convergence
Figure 1
4
Operation
The main power supply is a current resonance switching power supply. Figure 2 is a basic block diagram
for this supply . The primary winding of T862 and capacitor C870 create a LC series resonant circuit. An
oscillator (OSC), drive circuit, and two MOSFETs are
located internal to Q801 (STR-Z4117). The OSC determines the power supply’ s switching frequency . The
drive circuit alternately switches the MOSFETs ON
and OFF. The two power MOSFETs, in a push-pull
configuration, alternate the current flow through the
LC circuit during normal operation. The alternating
current continually builds and collapses an electromagnetic field around T862’s primary windings. The collapsing of the electromagnetic field induces current into
the secondary windings of T862. A full-w a v e bridge
rectifier conv erts the induced current into 125Vdc.
To regulate the 125Vdc, an error amplifier monitors
the voltage and supplies a negative feedback to the
oscillator through photo-coupler Q862. Q862 isolates
ing frequency is to resonance, the more current flows
through the primary windings of T862 and the larger
the electromagnetic field builds. The larger the electromagnetic field is when it collapses, the more current
is induced in the secondary winding. When the load
decreases and requires less current, the switching frequency increases and moves a way from resonance. As
a result, less current is induced in the secondary windings.
Load
Current
Increased
Load
Decreased
Load
D
O
r
i
S
v
C
e
Q801
Figure 2
the primary side of the power supply from the secondary side.
Refer to figure 3. The po wer supply’s switching frequency operates above the LC resonance frequency.
When the load increases and requires more current,
the oscillator frequency decreases and operates closer
to the LC resonant frequency. The closer the switch-
T862
C870
Photo
Coupler
Q862
125V
Error
Amp
Z801
+B
Resonant Freq.
Normal Operatin Freqency is 70-80kHz
Figure 3
Operating Freq.
Switching
Freq.
5
Surge Protection Relay.
Start-up and Over Voltage Protect
Refer to figure 4. To prolong the life of the power
supply , a surge circuit reduces current through the main
power supply at startup. When the tele vision is OFF,
relays SR81 and SR82 are open. At turn ON, SR81
closes and the switching power supply begins to operate. During this time, the power supply draws a large
amount of current. To reduce the current, the ground
path for bridge rectifier D801 is through resistor R810.
Once the power supply becomes fully operational and
produces output voltages, one of these voltages is applied to the base of transistor Q846. This voltage turns
Q846 ON and allows current to flow through the coil
of SR82. SR82’s switch closes and creates a direct
ground path for D801 by bypassing R810. SR82 remains closed during normal operation.
Troubleshooting Tip:
R810 is a fusible resistor. If SR82 does not close after
the power supply is fully operational, R810 eventually
opens and prevents the power supply from operating.
Whenever troubleshooting the power supply , check R810
first. If R810 is open, replace it using T oshiba part number 24007061 and look for cold solders around Q846
and R846.
Refer to figure 5. The positive cycle of the AC line
input supplies a 16V start-up pulse to pin 8 of Q801
via resistor R861. After start-up, a drive circuit consisting of a secondary winding of T862, diode D864,
and capacitor C868 supply 16-20Vdc to pin 8 of Q801
to maintain its operation. The voltage developed by
the drive circuit fluctuates with the switching frequency
of the power supply . Therefor e, the voltage on pin 8 is
also applied to an over voltage protect (OVP) block
internal to Q801. If the voltage on pin 8 increases to
25V, the OVP triggers the latch and switching stops.
Refer to the latch block for further information. D876
is a 27V zener diode that protects Q801 by preventing
excess voltage increases on pin 8.
From
D801
R861
16-20 Vdc
8
D864
D876
Vcc
Q801
R871
T862
C868
Relay
SR81
R810
Main Power Supply
Q801
D801
and
T862
SR82
Figure 4
R846
Q846
125V
12V
6
OVP
Start
Figure 5
Logic and Drivers
Oscillator
Refer to figure 6. The logic block controls the
MOSFETs’ switching frequency. The outputs of the
logic block feed two drivers that are powered by the
start block. After the start-up v oltage is applied to pin
8, the start block supplies a drive Vcc (DRI Vcc) of
approximately 8V to pin 9. Delaying the driver supplies at start-up, prevents damaging the MOSFETs. The
8V on pin 9 powers driver B internally. To power
driver A, resistor R862 and diode D862 add the voltage from pin 9 to the voltage on pin 15. D875, C863,
D873 and C873 are voltage regulators and filters for
these supplies.
D873
C873
R862 D862
D875
C863
V
IN
1
B+
130V
Out
14
COM.
12
To
T862
8
Start
Vcc
DRI Vcc
915
Logic
VB
Q801
A
B
Refer to figure 7. Q801’ s internal Oscillator de velops
the power supply’ s switching frequency by generating
a ramp waveform internally . During normal operation,
both MOSFETs are OFF for a short time when they
are alternately switching. This OFF time is called dead
time and determined by resistor R867 on the dead time
(DT) terminal pin 7.
Q801
OSC
7
DT
R867
Figure 7
Figure 6
7
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