50Hz CHASSIS
100Hz CHASSIS
GENERATION OF INTERNAL REFERENCES
AND POWER SUPPLIES
The power supply at Pin 16 comes
from:
On start-up, half-wave rectification
of the mains by the mesh RP025, CP054, and a diode of the bridge rectifier. In
Standby Mode, winding 9, 8 of LP020 (fly-back mode). 12 V obtained by
rectification (DP050, CP054) is applied to regulator IP050 (7809 applied to
Diode DP051), which supplies 9 V via DP052.
In Steady-State, winding 9, 10 of LP020 (fly-back mode). Rectification by
DP053 supplies a voltage of about 11 V.
Note that in this case Diode DP052 is blocked, and disconnects circuit
IP02.
Resistor RP054 delivers the power
supply to the final stage (Pin 15), and sets its maximum current. The circuit supplies several voltages and
service signals according to changes in the direct current
voltage at Pin 16. As soon as +Vdc
reaches approximately 4V5, an internal reference of +2V5 is generated. For +Vdc & 5V5, a RESET pulse is produced. When
+Vdc reaches 10V3 (Vdc start), enabling of an internal power supply Vdc int = 5
V. This stabilized voltage allows the circuit to perform well in a wide voltage range on Pin 16. This threshold also triggers the passage to
high state of Vdc off, thus enabling the interlock and limit management logic,
and authorising pulse output from Pin 14 (as long as +Vdc remains higher than
+Vdc stop, i.e. 7V4 typ.). For Vdc of
15V7 typ., passage to high state of Vdc max, and interlocking of the
circuit by the interlock and limit management logic.
OPTIONS
SWITCHING OF START-UP POWER SUPPLY:
On 100-Hz chassis, a thyristor
(TP025) is added in series with Resistor RP025. When mains power is applied, a current from the 300 V via the
RP028, RP030 through 32 resistor network energizes the thyristor. The thyristor
then channels the CP054 charging current.
When the power supply starts up, a voltage of 9V6 appears at the output
of Regulator IP050 and saturates Transistor TP026. With its gate then earthed,
the thyristor de-energizes the next time the mains alternation is inverted. This layout reduces the consumption
by 0.7W.
LOW-POWER SWITCH
A low-power switch can be connected
in series with Resistor RP025 to replace the classic mains switch. In operation, this switch connects RP025 via
Resistor RP55 to Pin 16 of IP60. In Off
position, this switch switches Pin 16 of IP060 to earth via Resistor RP035 and
Diode DP035. Zener Diode DP054 limits
the voltage to the terminals of CP54 when Off.
OUTPUT STAGE
The output stage of the TEA2261
consists of a push-pull. It supplies
the basic current for control of TP060, and then channels the reverse locking
current caused by the discharging of CP040.
In the conduction phase, Resistor RP054 limits the polarization current. TP060 SWITCHING CIRCUITS
resistors RP029 through RP032 pre-charge CP040 as soon as power is switched on,
to ensure an adequate reverse locking current during the start-up phase and at
the beginning of each burst. Self-induction coil LP040 sets the dl/dt of the
control current reversal. The circuit
DP022, CP023, RP022 slows the rise in collector voltage of TP060 when it is
blocked, to ensure minimum dissipation through switching, and to limit the
overvoltage peak. To do this, it is assisted by the secondary assembly DP113,
LP112, RP112, CP112, and DP112.
Secondary Voltages
The secondary wingdings produce five
direct voltages:
+USYS which can be between 127 and
140 volts, according to chassis, and according to the winding connector
selected (19 through 22 via jumpers JP914 through 917).
+US and -US, symmetric power
supplies with specific earth distributed to the audio stage via a cable (from
BP120). +UVERT, vertical stage power
supply voltage. Also applied to the regulator circuit, IP30, and causes the polarization of the base of TV002 (IV001 power supply). +U7V, voltage supplying the switched 5
V. In Standby Mode, the 10VSTBY is
produced by Regulator IP130 and Diode DP133. In Steady State, the 13 V from the
EHT takes over via Diode DP134. The
switched 5 V is obtained at Pin 8 of IP140 (switched by voltage +U13, Pin 4) on
50-Hz stereo chassis, while a transistor, TP146, handles this regulation task
for 50-Hz Dolby and 100-Hz chassis.
Secondary Regulation
This mode is adopted as soon as
Steady-State Mode begins. It regulates voltage USYS. A fraction of USYS, tapped off by divider bridge RL082, RL081,
and RL080,
is applied to Pin 31 of IV001 (SMPS
IN). This information is compared to an
internal reference whose value can be adjusted according to operating mode
(USYS adjusted in 64 steps within a 16-V range). A strobe signal at line frequency with a variable duty cycle is
available on Pin 37 (SMPS OUT). This
signal is applied to galvanic isolating transformer LP070 via Transistor
TP161. A soft start circuit is
associated with the production of the command strobe signal. (CV246, Pin 17;
when power is applied to circuit IV001, it is charged to 5V5 in 900 ms. The
network RV242, CV242, CV243 limits the pass band of the entire regulating loop
to 300 Hz. On 100-Hz chassis, Transistor TP162
controls transformer degassing In the
event of irregularities on the secondaries or in the time bases, the interlock
circuit forces the BREATHING line to low state (Pin 28 of IV001). The regulating and time base commands are
then stopped. If the error persists after two more start-up attempts by IV001,
the TV goes into Standby Mode.
Power Supply Interlocks
Overloads and short circuits are
detected by analysing the primary current in the emitter resistor of TP060
(input at Pin 3 of circuit IP060). The
sensitivity of this stage was increased in Standby Mode to detect errors in the
low-voltage secondaries (RP065, TP027, and RP059). For this reason, when an
incident occurs in Steady State on a secondary other than U SYS, it is
necessary to go to Standby Mode to trigger the interlock.
- An overload or short circuit on voltages +U VERT or +10 V STBY leads to:
power supply VCC1 of the regulation
and sweep circuit (IV001) disappearing.
An overload or short circuit on +US causes TP190 and TP170 to
conduct. This forces the breathing
interlock input of the regulation and sweep circuit (IV001) to be triggered by
a low level.
- An overload or short circuit on:
- US causes DP190 and TP170 to conduct, and triggers the IV001 interlock. In the event that external speakers with too low an impedance value are connected (Dolby versions), or when incidents occur on the +5 V, simply shut off the sweep to remove the overload:
·
Excessive
current in Resistor RP130 causes TP129 and TP170 to conduct, and triggers the
IV001 interlock (audio mute).
·
A
short circuit on the +5 V blocks TP175 through the action of DP178, and causes
TP170 to conduct (see sweep interlocks), causing the IV001 interlock
to
trigger and the +13 V to disappear.
Detection of Mains Power Failure
In the event of mains power failure,
the micro controller must be informed promptly so that the data in the NVM
(IR003) can be saved, and to avoid a plop in the speakers (sound mute).
To do this, POWER FAIL has a rising
edge in the event of mains power failure in ON Mode, and a falling edge in the
event of mains power failure in Standby Mode.
The signal is received by the
management circuit via the INTERRUPTION input at Pin 55. Transistor TR091
produces a low mute level when the phenomenon occurs in ON Mode.
The negative voltage rectified in
Forward Mode by Diodes DP151/152 is an image of the mains voltage. It blocks
TP152 in ON Mode. TP150 and TP145 are blocked. TP167 is saturated, and the
POWER FAIL line has a low level.
When the mains falls below 160 Vac,
TP152, TP150, and TP145 conduct, TP167 generates a rising edge on the POWER
FAIL line by blocking off. In Standby
Mode, because voltage +UVERT goes from 23-26 V to 14 V, the RP150/151 network
saturates TP150, TP145 conducts and blocks TP167, and the POWER FAIL line has a high
level.
When
mains power breaks down, the decrease in 10VSTBY saturates TP166 and TP167, and
the POWER FAIL line has a falling edge.
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