Toshiba TP43H60, TP43H95, TP50H15, TP50H50, TP50H60 Service Manual

Projection Televisions

Main Power Supply

&

Complete Shutdown Troubleshooting Guide

TP43H60 TP55H64

TP43H95 TP55H95

TP50H15 TP61H60

TP50H50 TZ43V61

TP50H60 TZ50V51

TP50H64 TZ50V61

TP50H95 TZ55V61

TP55H60 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 AC line source. This supply delivers a 5V VDD and a reset 5V to the microprocessor to keep the microprocessor functioning at 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 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 AC 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 &	Stand-by
Isolation Trans.	Regulator	Microprocessor

Main Power Supply

D840		+5-1	5V	VDD
	Q840		5V
T840				Reset
				QA01	11
5V=Relay On
0V=Relay Off					9
	From Shutdown
QB30	Relay Drivers				9
Q843					10
	Rectifier	Main Switching IC
SR81	D801	165V	Q801	4	12

AC Line	Relay		13
Input		7
			14
		C870	15
			16
			17
		T862

Photo

Coupler

Feedback

Q862

Q760	30V	To Q752
	Reg.	Conv. Output
Rectifiers

			To Q752 & Q751
D856 +36			Conv. Outputs

	D855		Q754	5V	To Digital Conv. PC,
				Reg.	Q764 & Q767
	D851	+18	Q755	9V	To Q752
				Reg.	Conv. Output
	D854	-18			To Q752 & Q751
					Conv. Outputs
				-9V
			Q756		To Digital Conv. PC,
	D886	+38		Reg.
					To Q601 Audio Out
	D889
				9V	To Q501
			Q430
				Reg.	Horizontal Start-up
	D891	+12			To Shutdown & Surge protect:
	D894			9V	Q846,SR82,Q757, & Q758
			Q832		+9-2 To Numerous Circuits
				Reg.
	D882	+125	Q830	5V&9V	+5-2 To Numerous Circuits
				Reg.	+9-1 To Numerous Circuits
	D884			5V
			Q831		+5-3 To PIP Module & QBB3
				Reg.
	Error				To Horizontal Output
				32V
	Amp.		D101		To Tuner(s)
		Z801		Reg.
					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-wave bridge rectifier converts 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

	O	D
		r
	S	i
	C	v
		e
		Q801

T862 125V+B

C870	Error
Photo	Amp
Coupler	Z801
Q862

Figure 2

the primary side of the power supply from the secondary side.

Refer to figure 3. The power 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-

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 away from resonance. As a result, less current is induced in the secondary windings.

Load	Increased
Current	Load
			Decreased
			Load
	ResonantOperating		Switching
			Freq.
	Freq	Freq
	.	.

Normal Operatin Freqency is 70-80kHz

Figure 3

5

Surge Protection Relay.

Start-up and Over Voltage Protect

Refer to figure 4. To prolong the life of the power

Refer to figure 5. The positive cycle of the AC line

supply, a surge circuit reduces current through the main

input supplies a 16V start-up pulse to pin 8 of Q801

power supply at startup. When the television is OFF,

via resistor R861. After start-up, a drive circuit con-

relays SR81 and SR82 are open. At turn ON, SR81

sisting of a secondary winding of T862, diode D864,

closes and the switching power supply begins to oper-

and capacitor C868 supply 16-20Vdc to pin 8 of Q801

ate. During this time, the power supply draws a large

to maintain its operation. The voltage developed by

amount of current. To reduce the current, the ground

the drive circuit fluctuates with the switching frequency

path for bridge rectifier D801 is through resistor R810.

of the power supply. Therefore, the voltage on pin 8 is

Once the power supply becomes fully operational and

also applied to an over voltage protect (OVP) block

produces output voltages, one of these voltages is ap-

internal to Q801. If the voltage on pin 8 increases to

plied to the base of transistor Q846. This voltage turns

25V, the OVP triggers the latch and switching stops.

Q846 ON and allows current to flow through the coil

Refer to the latch block for further information. D876

of SR82. SR82’s switch closes and creates a direct

is a 27V zener diode that protects Q801 by preventing

ground path for D801 by bypassing R810. SR82 re-

excess voltage increases on pin 8.

mains closed during normal operation.

Troubleshooting Tip:

R861

D864

R871

R810 is a fusible resistor. If SR82 does not close after

the power supply is fully operational, R810 eventually

From

T862

opens and prevents the power supply from operating.

D876

D801

Whenever troubleshooting the power supply, check R810

C868

first. If R810 is open, replace it using Toshiba part num-

16-20 Vdc

8 Vcc

ber 24007061 and look for cold solders around Q846

Q801

and R846.

OVP

Start

	Main Power Supply
	Relay		Figure 5
		Q801	125V
	SR81
	D801	and	12V
		T862

SR82

R846

R810

Q846

Figure 4

6

Logic and Drivers

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 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 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
	DRI Vcc	VB	D875
8 Vcc			C863
	9	15
		Q801	VIN

		1
Start		B+
		130V
		A
	Logic	Out
		14
		To
		T862
		B
		COM.
		12

Figure 6

Oscillator

Refer to figure 7. Q801’s internal Oscillator develops 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

7