U.S. Philips Corporation

U.S. Phillips Corporation

Dirk J Teuling

Jozef J Hulshof

Henricus L Simons

Nicolaas Lambert

Franciscus A Schoofs

Hendrik Ten Pierick

Terence Doyle

Edward M Ponte

James J McCormack

Johannes A Misdom

Frederik J De Bruijn

Steven J Van Raalte

Willem J De Haan

Picture display device comprising a plurality of electron transport ducts or transporting electrons in the form of electron currents, and selection electrodes for withdrawing each electron current at predetermined locations from its transport duct and for directing said current towards a luminescent screen. The selection electrodes are driven by a selection driver comprising integrated driver circuits having outputs which are DC-coupled to the selection electrodes and are cascaded as regards their power supply voltages in such a way that they apply both selection pulses and transport (bias) voltage to the selection electrodes.

Picture display and selection driver and integrated driver circuit for

A switching device for S correction capacitors includes parallel-arranged branches, each having a series arrangement of an S correction capacitor (Cs) and a switch (S). At one side, the parallel branches are coupled to a horizontal deflection coil (Lh). The switches (S) are controlled by a microcomputer (13) for switching S correction capacitors (Csi) parallel in dependence upon a repetition frequency of horizontal synchronizing pulses (Hs). A hardware frequency detector (11) supplies frequency information (V) related to the horizontal synchronizing pulses (Hs). A frequency change detector (12) coupled to the hardware frequency detector supplies an attention pulse (AP) to an interrupt input (INT) of the microcomputer (13) when a change of the frequency information (V) has been detected.

Switching device for S correction capacitors

In the market, there is a tendency towards picture tubes with a super flat screen. Due to the flat screen, it is becoming increasingly difficult to meet the even tighter specification on North/South raster distortion (N/S distortion), the tighter specification being caused by a growing importance of text display and high resolution displays. A deflection correction circuit is provided which compensates for a N/S distortion by inducing a correction current (Icv) through a vertical deflection coil (Lv). The correction current (Icv) can be injected in the vertical deflection coil (Lv) via an injection transformer (Ti) coupled in series with the vertical deflection coil (Lv). The injection transformer (Ti) is driven via an output stage (3) by a waveform generator (1,2). The waveform generator (1,2) generates a voltage waveform (M) built up out of substantially straight line sections. The deflection coil (Lv) integrates the voltage waveform (M) into a current waveform (Icv) having substantially parabolic sections. Such an inexpensive and flexible deflection correction circuit can be used to compensate for top/bottom and/or seagull N/S distortion, or for correction of convergence distortions. The deflection correction circuit can be a discrete or an integrated circuit.

Deflection correction

In order to cause scan and/or fly-back voltages (Vsca, Vfly) supplied by a horizontal output stage (1) to vary at a desired rate during a change of state in a horizontal deflection circuit (1, 2, 4), a feedback circuit (4) is provided. This feedback circuit (4) processes the scan and/or fly-back voltages (Vsca, Vfly) to a control voltage (Vco) with which a duty cycle (dc) of a drive signal (Hdr) of a switching element (Tr) in the horizontal output stage (1) is influenced.

Horizontal deflection

One of the problems in display devices is that the black level is different for each type of display tube and is also dependent on temperature and ageing. The display devices hitherto known with black level setting circuits apply one control voltage to the relevant cathode during the field blanking interval, whereafter the cathode current is measured and subsequently compared with a reference current. Subsequently, the black level is adapted until the measured current approximately corresponds to the reference current. The display device now includes a black level setting circuit with a control circuit adapted to successively apply at least two control voltages in a predetermined ratio to the cathode. Moreover, the black level setting circuit includes a correction circuit for supplying a correction value dependent on the ratio between the currents generated in the relevant cathode in response to the at least two control voltages.

Display device including a black level setting circuit

A line sychronizing circuit in a picture display device, has a phase control loop including an oscillator and a phase comparison stage. In order to enlarge the capture range of the control loop, the phase comparison stage is in the form of a phase-frequency detector having a trigger action on edges of pulses applied, the circuit being provided with means for inhibiting the supply of the control signal form the phase-frequency detector during a predetermined period after establishing that the phase difference measured by the phase-frequency detector between the local line-frequency signal and the incoming line synchronizing signal is larger than a predetermined value. In the perdetermined period, the oscillator signal has substantially the same frequency as before establishing that the phase difference measured by the phase frequency detector is larger than the predetermined value. The supply of the control signal is restored during a second predetermined period after the supply of the control signal has been inhibited, and this irrespective of the phase difference between the local line signal and the incoming line synchronizing signal.

Line synchronizing circuit in a picture display device

A picture display device, having a line synchronizing circuit and a line deflection circuit, suitable for several line frequencies. Use is made of a modulator for modulating the line deflection current, a control stage being coupled to this modulator for applying a correction signal for correcting, in dependence on the frequency of a line oscillator in the line synchronizing circuit, the S-distortion or the linearity error, respectively, or to keep the amplitude of the line deflection current constant upon a change in the line frequency.

Picture display device including a line synchronizing circuit and a line

A circuit arrangement for generating a sawtooth-shaped signal for the field deflection in a picture display device with an amplitude which is substantially independent of the field frequency is disclosed. The value of the sawtooth-shaped signal during the occurrence of a sampling pulse is compared with a reference value for generating a control signal controlling the slope of the sawtooth-shaped signal. To eliminate instability in amplitude, which might result from phase jitter of the incoming field synchronizing signal and might cause an interlace error, sampling pulses are applied whose repetition frequency is substantially equal to the nth part of the field frequency, where n is an integer which is larger than 1, preferably a small multiple of 2.

Circuit arrangement for generating a sawtooth-shaped signal for the

A circuit arrangement comprising at least two high-voltage power switches (e.g. transistors) connected in series to a high voltage source. In order to ensure that the switches are automatically cut off substantially simultaneously, the control means of each switch comprise a delay element for delaying the cut-off signal. A comparison stage controls the delay caused by at least one delay element as a function of the difference between the voltage present at the junction point of the switches and a reference voltage.

Circuit for simultaneous cut-off of two series connected high voltage

A circuit for generating a sawtooth-shaped current through a coil, a plurality of periodically operated switches being arranged in series, by means of which switches the coil is connected to a trace capacitor during the trace period. During the retrace period, the switches are made non-conductive substantially simultaneously and a supply source produces supply energy for replenishing losses. A retrace capacitor is arranged in parallel with each switch and the supply source is connected in parallel with a number of series-arranged switches which is smaller than the total number of switches. The trace voltage is higher than the voltage of the source.

Circuit for generating a sawtooth-shaped current

A circuit arrangement for a picture display device for generating a sawtooth-shaped line deflection current, at least two controllable deflection switches which are switched at line frequency and are arranged in series. As a result thereof the line deflection coil is connected to a trace capacitor during the trace period. During the retrace period the two switches are rendered non-conductive substantially simultaneously and the coil, the trace capacitor and a retrace capacitance form a resonant network the elements of which determine the duration of the retrace period. Supply energy is supplied from a supply voltage source by means of a supply winding which is divided in at least two winding portions which are each connected by means of one end through a supply diode to the resonant network and by means of the other end to a deflection switch and are coupled to the source via a controllable supply switch, which switches at the line frequency. During at least a portion of the trace period the supply switch is in the conducting state while the supply diodes are non-conducting and are non-conducting during the remaining portion of the line period while the supply diodes conduct. The conduction period of the supply switch may be adjustable to adjust the amplitude of the deflection current and also to stabilize this current versus fluctuations of the supply voltage. The said amplitude does not depend on the line frequency.

Circuit arrangement for a picture display device for generating a

A line deflection circuit in a television display apparatus. Between the parallel diode and the chassis there is a series arrangement of a first winding and a capacitor, a second winding being included between the switch and the voltage supply source. A diode is connected to a point of the first and to a point of the second winding and conducts in the retrace period of the deflection current. By adjusting the conduction time of the switch a trace voltage can be obtained which exceeds the supply voltage so that the circuit is suitable for battery supply.

Circuit in a television display apparatus for producing a sawtooth

Control circuit for controlling a switched converter generating an output voltage which is independent of variations of the input voltage. For this purpose, a forward control is used with a sawtooth voltage of which both the variation during the pulse duration of the pulses applied to the switch of the converter and the slope are linear functions of the input voltage and of an adjusting voltage. The output voltage is proportional to the adjusting voltage. This can be derived from the output voltage by means of a feedback coupling.

Control circuit arrangement for generating a control signal for a

Through a provision of a bias voltage, with the aid of a diode to the base of a transistor of a complementary pair, which transistor is controlled via a small capacitance, a video output amplifier having a very slight dissipation can be obtained.

Television display apparatus having a video amplifier

A switched-mode power supply in which disturbing oscillations which are produced by the associated (auto) transformer are eliminated by means of a clipping circuit, a supply voltage being generated for the driver stage which controls the switch. This measure saves an expensive resistor and ensures a better operation of the circuit at a varying input voltage.

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Eindhoven, Netherlands

Dirk J Teuling