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TDA8143
HORIZONTAL DEFLECTION POWER DRIVER
TDA8143HORIZONTAL DEFLECTION POWER DRIVER
September 1993
PIN CONNECTIONS CONTROLLED DRIVING OF THE POWER
TRANSISTOR DURING TURN ON AND OFF
PHASE FOR MINIMUM POWER DISSIPA-
TION AND HIGH RELIABILITY. HIGH SOURCE AND SINK CURRENT CAPA-
BILITY. DISCHARGE CURRENT DERIVED FROM
PEAK CHARGE CURRENT. CONTROLLED DISCHARGE TIMING. DISABLE FUNCTION FOR SUPPLY UNDER
VOLTAGE AND NONSYNCHRONOUS OP-
ERATION. PROTECTION FUNCTION WITH HYSTERE-
SIS FOR OVERTEMPERATURE. OUTPUT DIODE CLAMPING. LIMITING OF THE COLLECTOR PEAK CUR-
RENT OF THE DEFLECTION POWER TRAN-
SISTOR DURING TURN ON PERIOD. SPECIAL REMOTE FUNCTION WITH DELAY
TIME TO SWITCH THE OUTPUT ON
DESCRIPTIONThe TDA8143 is a monolithic integrated circuit
designed to drive the horizontal deflection power
tran-sistor.
The current source characteristic of this device is
adapted to the non-linear current gain behaviour of
the power transistor providing a minimum power
dissipation. The TDA8143 is internally protected
against short circuits and thermal overload.
1/9
BLOCK DIAGRAM
PIN FUNCTIONS
ABSOLUTE MAXIMUM RATINGS
THERMAL DATA
TDA81432/9
ELECTRICAL CHARACTERISTICS (VCC = 12 V, Tamb = 25o C unless otherwise specified)
TRUTH TABLE
TDA81433/9
1.8 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750orON OFF(A/V) (A/V)
Figure 1 : GON
VPin3 and |GOFF|
VPin5
Figure 2 : Large Screen Application
COMPONENTS LIST FOR TYPICAL APPLICATION
TDA81434/9
APPLICATION INFORMATIONThe conventional deflection system is shown in
Figure 3. The driving circuit consists of a bipolar
power transistor driven by a transformer and a
medium power element plus some passive compo-
nents.
During the active deflection phase the collector
current of the power transistor is linearly rising and
the driving circuitry must be adapted to the required
base current in order to ensure the power transistor
saturation.
According to the limited components number the
typical approach of the present TVs provides only
a rough approximation of this objective ; in Figure 4
we give a comparison between the typical real base
current and the ideal base current waveform and
the collector waveform.
The marked area represents a useless base cur-
rent which gives an additional power dissipation on
the power transistor.
Furthermore during the turn-ON and turn-OFF tran-
sient phase of the chassis the power transistor is
extremely stressed when the convenctional net-
work cannot guarantee the saturation ; for this
reason, generally, the driving circuit must be care-
fully designed and is different for each deflection
system.
The new approach, using the TDA8143, over-
comes these restrictions by means of a feedback
principle.
As shown in Figure 4, at each instant of time the
ideal base current of the power transistor results
from its collector current divided by such current
gain which ensure the saturation ; thus the required
base current Ib can be easily generated by a feed-
back transconductance amplifier gm which senses
the deflection current across the resistor Rs at the
emitter of the power transistor and delivers :
Ib = RS • gm • Ie
The transconductance must only fulfill the condi-
tion :
1 + βmin ⋅ 1 < gm < 1
where β is the minimum current gain of the transitor.
This method always ensures the correct base cur-
rent and acts time independent on principle.
For the turn-OFF, the base of the power transistor
must be discharged by a quasi linear time decreas-
ing current as given in Figure 5.
Conventional driver systems inherently result into stable condition with a constant peak current
magnitude.
Figure 3 : Conventional Horizontal Deflection System for TVs
TDA81435/9
Figure 5This is due to the constant base charge in the
turn-ON phase independent from the collector cur-
rent ; hence a high peak current results into a low
storage time of the transistor because the excess
base charge is a minimum and vice versa. In the
active deflection the required function, high peak
current-fast switch-OFF and low peak current-slow
switch-OFF, is obtained by a controlled base dis-
charge current for the power transistor ; the nega-
tive slope of this ramp is proportional to the actual
sensed current.
As a result, the active driving system even im-
proves the sharpness of vertical lines on the screen
compared with the traditional solution due to the
increased stability factor of the loop represented as
the variation of the storage time versus the collector
peak current.
Figure 4 : Waveforms of Collector and
Base Current
Figure 6 shows the block diagram of the TDA8143,
the circuit consists of an input transconductance
amplifier composed by Q1, Q2, Q3 and Q4.
The symmetrical output current is fed into the load
resistor R1 and R2 ; the two amplifiers V1 and V2
realize a floating voltage to current converter which
can drive 1.2A sink current and 2A source current
for a wide common output range.
So, the overall transconductance results into :
gm = R1 + R2 ⋅ 1
A current source I1 generates a drop of 70mV
across the resistor R4 which provides an output
bias current of 140mA ; the control input determines
the turn ON/OFF function.
In the ON phase, Q5 shorts the external capacitor
Ct. Within the input voltage range 0 < Vin < 750mV
the element realizes the transconductance func-
tion ; lower voltages are clamped by the D1/Q6
configuration.
For input voltages higher than 750mV, Q7 limits the
maximum output current at 1.5A peak.
In the turn-OFF mode, Ct will be charged by the
controlled source I2 which is proportional to the
input voltage, by this way, the output current de-
creases quasi linearly and the system stability is
reached.
During the flyback phase, the IC is enabled via the
sync. detector input ; this function with the limited
sink and source current together with the undervol-
tage turn-OFF and a chip temperature sensor en-
sure a complete protection of the IC.
CIRCUIT DESCRIPTION
TDA81436/9
