Read Sharp 28JW-74H (serv.man2) Service Manual online
50Hz Widescreen Colour Television – GA20 Chassis
Sharp Electronics (UK) Ltd
Technical Support
Issued June 02
Page 2
SUPPLY
MANAGEMENT
internal
supply
UVLO start
VOLTAGE
CONTRLLED
OSCILATOR
FREQUENCY
CONTROL
OVER-
TEMPERATURE
PROTECTION
POWER-ON
RESET
-1
S1
~
MAXIMUM
ON-TIME
PROTECTION
Q
Q
SET
CLR
S
R
UVLO
LODGIC
LODGIC
START-UP
CURRENT SOURCE
VALLEY
DRIVER
LEB
blank
OCP
short
winding
+
+
+
-
-
-
OVERPOWER
PROTECTION
soft
start
OVERVOLTAGE
PROTECTION
+
-
Drain (start)
Demag
Drive
I
sense
4
8
6
5
3
2
1
TEA1507
Iss
Supply (Pin 1)
Initially, the IC is self supplying from the rectified mains voltage via pin 8 (drain). External supply
capacitor, C705 at pin 1 is charged by the internal start-up current source to a level of about 4 V or
higher, depending on the drain voltage. Once the drain voltage exceeds the M-level (mains-
dependent operation-enabling level), the start-up current source will continue charging capacitor C705
(switch S1 will be opened, see TEA1507 block diagram). The IC will activate the power converter as
soon as the voltage on pin V
capacitor, C705 at pin 1 is charged by the internal start-up current source to a level of about 4 V or
higher, depending on the drain voltage. Once the drain voltage exceeds the M-level (mains-
dependent operation-enabling level), the start-up current source will continue charging capacitor C705
(switch S1 will be opened, see TEA1507 block diagram). The IC will activate the power converter as
soon as the voltage on pin V
CC
passes the V
CC
(start) level. The IC supply is then taken over by the
secondary winding of T703, (pins 1 and 2), as soon as the output voltage reaches its intended level.
The IC supply from the mains voltage is subsequently stopped for high efficiency operation (green
function).
The moment the voltage on the V
The IC supply from the mains voltage is subsequently stopped for high efficiency operation (green
function).
The moment the voltage on the V
CC
pin drops below the UVLO (undervoltage lock out) level, the IC
stops and restart from the rectified mains voltage. Inhibiting the Vcc supply by external means causes
the TEA1507 to operate in a stable burst mode.
Typical Vcc voltages
Start > 10.3 v
UVLO < 8.1 v
the TEA1507 to operate in a stable burst mode.
Typical Vcc voltages
Start > 10.3 v
UVLO < 8.1 v
Over-Temperature
An accurate temperature protection is provided in the circuit. When the junction temperature exceeds
the thermal shutdown temperature, the IC will stop switching. When V
the thermal shutdown temperature, the IC will stop switching. When V
CC
drops to UVLO, capacitor
C705 will be recharged to the Vstart level. If the temperature is still too high, VCC will drop again to
the UVLO level. (safe restart mode).
Drain (Pin 8)
Initially, the IC is self supplying from the rectified mains voltage via pin 8 (Drain)
the UVLO level. (safe restart mode).
Drain (Pin 8)
Initially, the IC is self supplying from the rectified mains voltage via pin 8 (Drain)
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