GRUNDIG SUPER COLOR P37-222 GCE15 CHASSIS CUC 2201 Internal View.

FULLY Modular Chassis CUC2201. No Power supply but a SMPS Line Power supply with ONE
Transformer for all puprpose (Supply + Deflection + EHT) Based on TDA3640.
The CHASSIS CUC 2201 Is the Father predecessor of all CUC 3400 CUC 3410 and CUC 3510 CHASSIS series of GRUNDIG television.




No "Official" power supply, all supplyes are generated via the Line + EHT Transformer which acts as SMPS LINE TRANSFORMER.


























It seems simple but is sophisticated, all is based on two MAIN components:
The TDA3640 (PHILIPS) and the SMPS LINE TRANSFORMER which is very particular.


SMPS LINE TRANSFORMER Does the Line deflection + EHT + SMPS Transformer. All switching frequency is line and phase frequency locked.



This chassis was reliable except for the EHT tripler which was failing very often.
The EHT tripler was causing sometimes big troubles.


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GRUNDIG SUPER COLOR  P37-222  GCE15  CHASSIS  CUC 2201  DESCRIPTION OF THE ZNT - LINE SUPPLY TRANSFORMER TECHNOLOGY, ONE TRANSFORMER FOR ALL FUNCTIONS :


Short Functional Description
The GRUNDIG line/power supply unit has two important features:

- the line/mains transformer (ZNT) with ferrite core.
This transformer is provided with windings for the power supply and line output stages:

- the supply frequency corresponds to the line frequency.

The ZNT is used for electrical isolation, horizontal deflection, and generation of the operating voltage. The ZNT windings are tightly and loosely coupled to ensure that the load capacity of the supplies is high enough and that back effects on the line transformer winding N-M are avoided.

Startup Circuit
The starting voltage for IC 655 is obtained from the bridge rectifier D 621 via R 641. lf the voltage on pin 2, which is derived from the resistor network R 642, 643, and 644, reaches a level of approximately 10 V, the IC 655 starts to drive T 6  61 via pin 3 (precondition: pin ‘8>10V).
The line/power supply circuit starts to oscillate.
Simultaneously, the current consumption drawn via pin 2 rises and the winding E-D of
the ZNT takes over the operating voltage supply function (D 647, R 647, C 647).
Oscillator in IC TDA 3640 The control pulses for the T 661 are generated by an oscillator which operates on the threshold principle where C 653 is an externaly connected frequency-determining component (oscillator retaining range 14-17 kHz approx.). The oscillator oscillates at a free-run frequency until the reference pulses from the ZNT exceed 1 Vp at pin 12.
ln full operating condition (ON) avoltage of about +5 Vp is applied to pin 12.

Line 0utputStage
The deflection transistor T 521 is activated in stand-by mode. The cyclic line-frequency control of the deflection transistor corresponds to the “ON" operating mode.
The power for the horizontal sweep circuit is derived from the electromotive force of coil M-N that no additional operating voltage is necessary for T 521.

Vooltage Stabilisation
ln stand-by mode the pulse from winding E-D (tightly coupled with winding A-B) is used as a reference for stahilisation. The controlled variation is +10.5 V on pin 2 TDA 3540.

ln full operating condition, that is 'ON“. the voltage in the horizontal sweep circuit (transformer winding M-N) must be stabilised to a constant level. This is achieved by means of a reference pulse from winding C-D which is tightly coupled with winding M-N. The resulting direct voltage
obtained via D 633 is proportional to the width of the picture or high voltage and is applied to pin 10 and compared with the reference voltage (about 3 V) on pin 11. ln this part of the circuit the +C voltage is adjusted by means of R 637 to 196 V and 192Vf'or 25" receivers and 28" receivers.
respectively.

Protective Circuits of TDA 3640
The protective circuits respond immediately if:
- the operating voltage on pin 2 is too low (<7 V):
- ICE of T 521 is too high (more negative than -1 V at pin 7);
- the power supply voltage is too high (voltage at pin 18 is 2.8 V higher than at pin 2);
- the power supply voltage is too low (voltage at pin 18 is 1.4 V lower than at pin 2);
- the high voltage is excessivley high (line flyback pulses >6V at pin 12):
- the crystal temperature is too high (>135° C).



The invention relates to a horizontal deflection circuit for a picture display apparatus, comprising:
a horizontal output stage provided with a switching element which is coupled to a horizontal output transformer for generating at least one voltage, and
a drive circuit for generating a drive signal for switching the switching element, and provided with a duty cycle control circuit for modulating a duty cycle, of the drive signal during changes of state of the horizontal deflection circuit.
The invention also relates to a method of horizontally deflecting a cathode ray of a picture display tube, and to a picture display apparatus provided with the horizontal deflection circuit.
2. Description of the Related Art
Such a horizontal deflection circuit is known from German Patent Application DE-A-4021940, corresponding to U.S. Pat. No. 5,381,329. This Application describes a power supply circuit in which a switching element (a transistor in this case) is coupled to a power supply transformer and a horizontal output transformer. Such a power supply circuit, which is known as Wessel circuit, supplies power supply voltages by means of the power supply transformer and a horizontal deflection current, fly-back voltages and/or scan voltages by means of the horizontal output transformer. In normal operation, the power supply circuit, further referred to as combined circuit, generates a drive signal of which one edge is used for fixing a switch-off instant of the switching element. This switch-off instant initiates a horizontal fly-back, and is controlled in normal operation by what is generally referred to as a phi2-control circuit. To this end, the drive circuit compares instants of occurrence of fly-back pulses supplied by the horizontal output stage and related to the horizontal fly-back, on the one hand, with instants of occurrence of the horizontal synchronizing pulses, on the other hand. A possible difference in instants of occurrence is corrected so that the video signal is displayed at the correct horizontal position on the display tube.
During a described change of state from stand-by operation to normal operation, a duty cycle of the drive signal is controlled so as to continuously increase an on-time of the switching element from a small value to a nominal value. With such a variation of the duty cycle, the switching element is protected from a too large dissipation. However, a duty cycle modulation, as used in the combined circuit, does not provide the possibility of having a variation of voltages generated by the combined circuit during the change of state to satisfy various requirements imposed by different components that are coupled to the scan and fly-back voltages.
SUMMARY OF THE INVENTION
It is, inter alia, an object of the invention to provide a horizontal deflection circuit and a method in which, during a change of state, a duty cycle variation is influenced by at least one of the voltages generated by the horizontal deflection circuit so as to satisfy the various requirements which are imposed on a variation of different voltages. The requirements referred to relate to, for example, a maximum admissible current in components connected with the voltages or a maximum admissible rate at which a voltage may vary around a specific value.
To this end, a first aspect of the invention provides a horizontal deflection circuit for a picture display apparatus, comprising a horizontal output stage provided with a switching element which is coupled to a horizontal output transformer for at least generating a voltage, and a drive circuit for generating a drive signal for switching the switching element, and provided with a duty cycle control circuit for modulating a duty cycle of the drive signal during changes of state of the horizontal deflection circuit, characterized in that the horizontal deflection circuit is provided with a feedback circuit having at least one feedback input which is coupled to an output of the horizontal output stage for receiving a DC signal which varies during said changes of state, said feedback circuit having an output for applying a control signal to a control input of the duty cycle control circuit. By an arranged feedback with a voltage generated by the horizontal output stage, a first rate of growth of the duty cycle of the drive signal determined by the maximum admissible dissipation in the switching element is changed at an instant when the variation of one of the fed-back voltages tends to reach an unwanted range. According to the invention, the control of the duty cycle variation provides the possibility of inhibiting the rate at which voltages rise at the instant when one of the components tends to violate an imposed requirement. It consequently is not necessary to choose a constant, very slow increase of the voltages, satisfying all requirements, but unnecessarily extending the duration of the change of state.
An embodiment of the horizontal deflection circuit having the characterizing feature that the DC signal is related to at least a scan voltage generated by the horizontal output transformer, provides the possibility of an accurately defined desired variation of a scan voltage, with the advantage that charging of the capacitors coupled to the scan voltage varies at a chosen second rate. Consequently, too large currents and loads are not produced in these capacitors and components arranged in series therewith such as diodes, coils, resisters or fuses. In this way, the current in a horizontal output transformer coupled to the switching element, can also be maintained below a saturation value, and the peak lead of a power supply circuit feeding the horizontal deflection circuit decreases.
An embodiment of the horizontal deflection circuit, with the characterizing feature that the DC signal s related to at least a fly-back voltage generated by the horizontal output transformer, provides the possibility of an accurately defined desired variation of a fly-back voltage. This also has the advantage that too large loads of components arranged in series with the above-mentioned capacitors, such as diodes, coils, resisters or fuses cannot be produced. To prevent flash-over in display tubes which are sensitive thereto, a desired third rate can be fixed at which the anode voltage of the display tube, which is also a fly-back voltage, increases. To this end, a voltage derived from the anode voltage or another fly-back voltage can be fed back. It is alternatively possible to reduce or eliminate the noises which may occur due to large current variations or due to a fast rise and fall of the anode voltage during switching on and switching off the picture display apparatus.
The embodiment of the horizontal deflection circuit, with the characterizing feature that the feedback circuit is provided with change detector means coupled to the feedback input for supplying output signals which are a measure of a change of the DC signal, has the advantage that only the variation in DC signals is fed back, with which in normal operation, in which the DC signals have reached their final value, the feedback does not have any influence on the duty cycle control.
An embodiment of the horizontal deflection circuit, with the characterizing feature that the feedback circuit is further provided with a threshold circuit arranged between the feedback input and the change detector means, provides the possibility of limiting the variation of a scan or fly-back voltage above a level determined by a threshold circuit at a fourth rate. This provides the advantage of obtaining an extra slow increase of the anode voltage above this level which is necessary for display tubes which are sensitive to flash-over during a rise of the anode voltage close to a final value.



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TDA8140 HORIZONTAL DEFLECTION POWER DRIVER
DESCRIPTION
The TDA 8140 is a monolithic integrated circuit designed
to drive the horizontal deflectionpower transistor.
The current source characteristic of this device is
adapted to the on-linear current gain behaviour of
the power transistor providing a minimum power
dissipation. The TDA8140 is internally protected
against short circuit and thermal overload.

During the active deflection phase the collector
current of the power transistor is linearly rising and
the driving circuitry mustbe adaptedto 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 5
wegive a comparisonbetweenthe typical real base
current and the ideal base current waveform and
the collector waveform.
The marked area represents a useless base current
which gives an additional power dissipation on
the power transistor.
Furthermoreduring the turn-ONand turn-OFFtransient
phase of the chassis the power transistor is
extremely stressed when the conventionalnetwork
cannot guarantee the saturation ; for this reason,
generally, the driving circuit must be carefully designed
and is different for each deflection system.
The new approach, using the TDA 8140, overcomes
these restrictions by means of a feedback
principle.
As shown in Figure 5, 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 feedback
transconductanceamplifier 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 condition
:
1
1 + bmin V 1
RS
<>
RS
Where bmin is the minimum current gain of the
transistor. This method always ensures the correct
base current and acts time independent on principle.For the turn-OFF, the base of the power transistor
must be discharged by a quasi linear time decreasing
current as given in Figure 6.
Conventional driver systems inherently result into
a stable condition with a constant peak current
magnitude.
This is due to the constant base charge in the
turn-ON phase independent from the collector current
; 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 discharge
current for the power transistor ; the negative
slope of this ramp is proportional to the actual
sensed current.
As a result, the active driving system even improves
the sharpnessof vertical lines on the screen
compared with the traditional solution due to the
increasedstability factor of the loop representedas
the variation of the storagetime versus the collector
peak current.