Toshiba ColorStream TP43H60 Manual

NTDMOD02
TOSHIBA
Service Training
PROJECTION
TELEVISIONS
Main Power Supply
& Complete
Shutdown Guide
TP43H60
TP43H95
TP50H15
TP50H50
TP50H60
TP50H64
TP50H95
TP55H60
TP55H64
TP55H95
TP61H60
TZ43V61
TZ50V51
TZ50V61
TZ55V61
TZ61V61
Copyright 1999
TOSHIBA AMERICA CONSUMER PRODUCTS, INC.
NATIONAL SERVICE DIVISION
1420-B TOSHIBA DRIVE, LEBANON, TN 37087

Contents
Main Power Supply...............3
Overall Block Diagram .................................................................................... 4
Operation........................................................................................................... 5
Surge Protection Relay ................................................................................... 6
Start-up and Over Voltage Protect................................................................. 7
Logic and Drivers............................................................................................. 8
Oscillator ........................................................................................................... 8
Oscillator Control............................................................................................. 9
Latch .................................................................................................................. 9
Thermal Shock Detection Block .................................................................... 9
Over Current Protection................................................................................. 10
Soft Start........................................................................................................... 10
Resonance Correction ................................................................................... 10
Additional Information on Q801 .................................................................... 11
Block Diagram of Q801 (STR-Z4117) ............................................................ 11
Pin Descriptions.............................................................................................. 11
Waveforms ....................................................................................................... 12
Troubleshooting Flowchart........................................................................... 13
Shutdown Guide.................15
Summary of Shutdown Circuits.................................................................... 16
Peak-Response Meter .................................................................................... 17
No Peak-Response Meter .............................................................................. 18
Monitoring Circuits ......................................................................................... 18
X-Ray Protect ................................................................................................... 19
+125V Over Current Protect .......................................................................... 20
+36V Over Current Protect ............................................................................ 21
+18V and – 18V Over Current Protect.......................................................... 22
+35V Over Current Protect ............................................................................ 23
+9V Under Voltage Protect............................................................................. 24
+35V Under Voltage Protect........................................................................... 24
+200V Under Voltage Protect ........................................................................ 24
Troubleshooting Flowchart........................................................................... 25

3
Main Power Supply

4
D882
D884
16
17
D891
D894
14
15
D886
D889
12
13
D851
D854
9
10
D856
D855
11 +36
+18
-18
+38
+12
+125
Q760 30V
Reg. To Q752
Conv. Output
To Q752 & Q751
Conv. Outputs
Q754 5V
Reg. To Digital Conv. PC,
Q764 & Q767
Q755 9V
Reg. To Q752
Conv. Output
To Q752 & Q751
Conv. Outputs
Q756 -9V
Reg. To Digital Conv. PC,
To Q601 Audio Out
Q430 9V
Reg. To Q501
Horizontal Start-up
To Shutdown & Surge protect:
Q846,SR82,Q757, & Q758
Q832 9V
Reg. +9-2 To Numerous Circuits
Q830 5V&9V
Reg. +5-2 To Numerous Circuits
+9-1 To Numerous Circuits
Q831 5V
Reg. +5-3 To PIP Module & QBB3
To Horizontal Output
D101 32V
Reg. To Tuner(s)
C870
T862
Main Switching IC
Q801
Z801
Error
Amp.
Q862
Photo
Coupler
D801
Rectifiers
Rectifier
165V
Feedback
SR81
Relay
Stand-by
Regulator
Rectifier &
Isolation Trans.
Q840
Microprocessor
QA01
QB30
Q843 Relay Drivers
D840
T840
4
7
9
Reg.= Regulator
Conv.= Convergence
+5-1
5V=Relay On
0V=Relay Off
5V
5V
AC Line
Input
From Shutdown
Stand-By Supply
Main Power Supply
VDD
Reset
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 AC line source.
This supply delivers a 5VVDD and a Reset 5V to
themicroprocessortokeepthemicroprocessorfunc-
tioningat all times, even when the television is not
operating. Transformer T840 isolates the standby
supply from the live ground, and D840 is a full-
wave bridge rectifier that supplies 12Vdc to volt-
age regulator Q840 and relay SR81 (connection
notshown). 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 QB30 and Q843 to close relay SR81.
When the relay closes, theAC line input is applied
directlyto themain powersupply. Thesupplystarts
to operate and turns ON the television. D801 is
the full-wave 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. De-
tailed explanations of the main power supply are
covered in the remainder of this section.
TroubleshootingTip:
IfSR81 never closes,check the standbypowersup-
ply. Both the5V VDDand theReset 5Vare manda-
toryfor the microprocessor to operate.
Figure1.
PowerSupplyBlock Diagram

5
Load
Current
Resonant Freq.
Operating Freq.
Switching
Freq.
Increased
Load
Decreased
Load
Normal Operating Frequency is 70-80kHz
rent, the oscillator frequency decreases and oper-
atescloser tothe LCresonantfrequency. Thecloser
theswitchingfrequencyistoresonance,thehigher
the current flow through the primary windings of
T862andthelargertheelectromagneticfield. The
largertheelectromagneticfield iswhen itcollapses,
the higher the induced current is in the secondary
winding. When the load decreases and requires
lesscurrent, the switching frequency increases and
moves away from resonance. As a result, less cur-
rent is induced in the secondary windings.
Photo
Coupler
+B
Error
Amp
D
r
i
v
e
O
S
C
T862
C870
Q801
Q862 Z801
125V
Operation
Themainpower supplyis acurrentresonantswitch-
ing power supply. Figure 2 is a basic block dia-
gramfor thissupply. TheprimarywindingofT862
and capacitor C870 create an LC series resonant
circuit. An oscillator (OSC), drive circuit, and two
MOSFETs are located internally 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
continuallybuilds andcollapses anelectromagnetic
field around T862’s primary windings. The col-
lapsing of the electromagnetic field induces cur-
rent into the secondary windings of T862. A full-
wave bridge rectifier converts the induced current
into 125Vdc.
To regulate the 125Vdc, an error amplifier moni-
tors the voltage and supplies a negative feedback
to the oscillator through photo-coupler Q862.
Q862 isolates the primary side of the power sup-
ply from the secondary side.
Refer to Figure 3. The power supply’s switching
frequency operates above the LC resonant fre-
quency. When the load on the secondary side of
the power supply increases and requires more cur-
Figure2
OperationalBlockDiagram
Figure3
LoadCurrentCharacteristics

6
Surge Protection Relay
Figure4 showsthe surgeprotectionoperation. To
prolong the life of the power supply, a surge cir-
cuit reduces current through the main power sup-
ply at startup. When the television is OFF, relays
SR81 and SR82 are open. At turn-on, SR81
closes and the switching power supply begins to
operate. Duringthis time,the power supplydraws
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.
SR82
Q801
and
T862
D801
Q846
R846
12V
125V
Relay
SR81
R810
Main Power Supply
R809
Figure4
SurgeProtect
TroubleshootingTip:
R810 is a fusible resistor. If SR82 does not close
afterthepowersupplyisfullyoperational,R810even-
tuallyopensandprevents thepowersupplyfromop-
erating. Whenevertroubleshooting the power sup-
ply, check R810 first. If R810 is open, replace it,
usingToshiba part number 24007061, and look for
coldsolderjointsaroundQ846andR846.

7
Vcc
Start
OVP
R871
T862
C868
D864
R861
Q801
From
D801
16-20 Vdc 8
D876
Start-up and Over Voltage Protect
The positive cycle of the AC line input supplies a
16V start-up pulse to pin 8 of Q801 via resistor
R861. Figure 5 is the block diagram for this cir-
cuit. After start-up, a drive circuit consisting of a
secondary winding of T862, diode D864, and ca-
pacitor C868 supply 16-20Vdc to pin 8 of Q801 to
maintain its operation. The voltage developed by
the drive circuit fluctuates with the switching fre-
quency of the power supply. Therefore, the volt-
age on pin 8 is also applied to an over voltage pro-
tect (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 sec-
tion for further information. D876 is a 27V zener
diodethat protects Q801by preventing excessvolt-
age increases on pin 8.
Figure5
Start-upandOverCurrentProtect

8
Logic and Drivers
As shown in 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 voltage 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 pow-
ers driver B internally. To power driverA, 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.
Oscillator
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
shorttimewhen theyare alternatelyswitching. This
OFF time is called dead time and determined by
the value of resistor R867 on the dead time (DT)
terminal pin 7.
VB
Logic
COM.
Out
V
IN
Vcc DRI Vcc
A
B
Start
R862 D862
C863
D875
C873
D873
To
T862
Q801
8915
12
1
14
B+
130V
Figure6
LogicCircuit
Figure7
Q801’sInternalOscillator
DT
OSC
R867
Q801
7

9
Oscillator Control
If the load current drawn from the 125Vdc line in-
creases, the 125Vdc voltage begins to drop, de-
creasingthe currentthrough Q862’sLED side. The
current drop causes the LED to couple less light to
thephoto transistorside andreduce thecurrentflow
into pin 4 of Q801. This reduction in current flow
varies the OSC frequency,moving it closer to reso-
nance to increase the supply of current to maintain
the 125Vdc level. Conversely, if the load current
decreases,the 125Vdc rises and increases the light
through Q862 and the current into pin 4 of Q801.
The increased current causes the OSC operating
frequency to move away from resonance to de-
creasethe current supplied to the load and level the
125Vdc.
Figure8
OscillatorControl
Latch
The latch block stops the operation of Q801 until
the voltage on pin 1 of Q801 is removed by turn-
ing OFF the television. As outlined in Figure 9,
any one of the following detection blocks can trig-
ger the latch.
• Over voltage protection (OVP) Block (Refer
toStart-up section)
• Thermal shock detection (TSD) Block
• Over current protection (OCP) Block
The charging time of capacitor C869, connected
to the capacitor delay (CD) terminal pin 6, delays
the operation of the latch circuit during start-up.
Thermal Shock Detection Block
Thethermal shockdetection blocktriggers thelatch
if Q801’s internal temperature exceeds 150°C.
OSC
4Cont.
OSC
Control
Q862
R864
Z801
125 Vdc Load
1
3
Out
B+ Q862
C891
R884
R883 Q801
6
CD
TSD OVP
LatchDelay
OC/RC
C869
Q801 1 V
IN
Figure9Latch

10
5
10
OC
Css
OC
Q801
T862
C870
R870
C867
To pin 14,
Q801
C866
R866
R872
165V from D801
OSC
OSC
Control
C874
RC
C872
11 RC
Over Current Protection
Figure 10 is the schematic diagram for the over
current protection and soft start circuits. The over
current detect (OC) senses excess current in the
LC series resonant circuit. As current in the LC
series resonant circuit increases, a voltage devel-
ops at the over current protect (OC) terminal pin
10. Resistor R870 and C874 detect the current
flowthroughthe LCcircuit. Resistor R866samples
thevoltage andappliesit topin10. Capacitor C867
is a filter to reduce ripple. Depending on the input
voltageon pin 10,theover current protect responds
in one of two ways:
(1) OC Low Threshold Voltage: +2V
When the input voltage at the OC terminal is
higher than +2V, the voltage at the soft start (Css)
terminal pin 5 lowers and the soft start engages.
Byreengaging the softstart, the mainoscillatorfre-
quencyincreases,reducing thecurrent flowthrough
the LC circuit. The soft start continues to operate
until the voltage on pin 10 drops below 2V.
(2) OC High Threshold Voltage: +2.5V
If the input voltage at the OC terminal exceeds
+2.5V,theoscillatorfrequencyincreases toits maxi-
mum frequency and C866 discharges rapidly.
When the Css terminal voltage decreases to 0.7V,
thecircuitresetsand C866charges again. Themain
oscillator frequency decreases gradually. If this
conditioncontinues, the latch engages and oscilla-
tionstops.
Soft Start
Still referring to Figure 10. At start-up, the soft
start is engaged by capacitor C866 on pin 5, soft
start(Css) terminal. Whilecapacitor C866 charges,
the switching frequency increases to reduce surge
currentthrough the MOSFETs. Once C866isfully
charged, the switching frequency goes to its nor-
mal operating frequency (approximately 70-80
kHz).
Figure10
OverCurrent Protect and Soft Start
Resonance Correction
Bymonitoring thecurrentflow throughpin11, The
resonance correction (RC) block prevents the
oscillator’s switching frequency from dropping
below the LC resonate frequency. As the switch-
ingfrequency decreases, current increases through
pin 11 of Q801. When the switching frequency
comes close to resonance, the RC block engages
the over current protect to increase the switching
frequency and move it away from resonance.