DE1537308C - Circuit arrangement for generating a periodic sawtooth current in a coil, in particular the Ablenkwick development of a television picture tube - Google Patents

Description

1 2

The invention relates to a circuit arrangement. During the trace, a flows linearly in a

to generate a periodic sawtooth current in the direction of changing deflection current through a diode,

a coil, in particular the deflection winding one of the undesirable losses in the deflection circuit

TV picture tube in which causes in a first branch. With the outgoing-controlled circuits

the coil via a first controllable, in both 5 conduct on the other hand during the relatively long

Directional switch at an energy storage trace interval one or more active, as a switch

chernden power source lies, with the controllable serving components in both directions, where

Switch by the anti-parallel connection of a control during the second half of the trace the energy ble rectifier is formed with a diode and. is supplemented in the deflection circle and the flowing constant

the control electrode of the rectifier with an io current, and thus the power

Control pulse source is connected, which the switch losses, is significantly lower.

conductive during part of the sawtooth trace The invention is based on the object of providing a backward,

makes, and in which the sawtooth return with the help of run-controlled deflection circuit to create which

a second controllable switch is initiated. improved efficiency without excessive

There are already numerous circuit arrangements 15 circuit complexity. .
for fully transistorized television receivers. Particularly problematic with such tran- a coil, in particular the deflection winding of a sistorempfänger, is from the standpoint of the reliable television picture tube, in which in a first power branch speed and economy, the horizontal deflection 20 the coil via a first controllable, in both circuit. To circumvent the difficulties of directional switches on a power source, the voltage and current carrying capacity is clearly visible, whereby the controllable switch through the anti-transistors has circuit arrangements parallel connection of a controllable rectifier with wound, which is formed with controllable silicon rectifiers of a diode, and the control electrode of the work, which can be loaded much more strongly than transistors 25 connected to a rectifier with a control pulse source. which switches the switch during part of the sawing

In a known line deflection circuit, the tooth leading makes conductive, and in the case of the sawtooth deflection winding via the anti-parallel connection of a return with the help of a second controllable switch controlled silicon rectifier with a diode is introduced, according to the invention achieved by put a voltage source. The control electrode of 30 that the first controllable switch also consisted of silicon rectifiers is with an output of part of a second branch of the current, which is monostable in series Multivibrators and the anode cathode circuit with the switch a second power source den route of a second controlled silicon DC and an oscillating reactance coupled, whose control electrode in turn holds, which during the middle part of the saw with The second output of the multivibrator feeds energy off when the switch is closed is bound. The control of the two silicon equal to the second power source picks up and by means of the judge takes place periodically towards the end with the help of the front or rear second controllable switch edge of the multivibrator pulse. For one also in the sawtooth trace from the second power source The current reversal point of the sawtooth trailing edge is disconnected again with the formation of an oscillating circuit running of the deflection current, the switching times of the 4 ° must be such that as a result of the natural oscillation of the Multivibrators are strictly adhered to. Here- reactance is the current in the first switch through is however, especially with regard to a first time reversing, its being more controlled the long-term constancy, a considerable circuit rectifier is blocked, and a second time moderate effort and extensive stabilization reversal, whereby its diode is also blocked, Measures conditional, which are in the price of the television 45 and the reactance thereby on the series device knock down, switching the first power source to the coil of the

It is also known that the deflection coil is switched via the first branch and with this one from the anti-parallel connection of a controllable series connection with compensation for the sawtooth silicon rectifier with a diode existing outward running coil losses the return switch to a 50 ′ oscillation serving as a voltage source.

To put the storage capacitor and the deflection coil Here, the reactance is used once

In addition, a series resonant circuit parallel to the switching energy storage during the sawtooth trace,

ten, over which the sawtooth return in the form of a further it represents a vibratory structure,

Half sine wave takes place. which at the beginning of the return interval by a

In these known circuits there is a double oscillation with its natural resonance

to return-controlled circuits, the current being reversed in the first switch and

controlled silicon rectifier during the short, finally, third along with the deflection coil

Recovery interval to a voltage source - usually only with the help of a capacitor

is switched so that the return oscillation carried out in the deflection coil during - executes. at

energy consumed during the outward run is replenished. 60 of the double current reversal due to the resonance

The efficiency of these circuits is in oscillation, however, the controllable rectifier of the

Compared to the conventional forward-controlled first switch due to the first current reversal

Circuits lower, which however is not so good for blocking while its diode is still conducting, which then

a wide-angle beam deflection of color television is also blocked by the second current reversal

tubes are suitable. With the return-controlled switch 65 is so that the first switch in two steps

flows during the return interval is closed and the resonant circuit of the reactive

relatively strong current in one direction due to resistance across the series connection of the deflection

the thyristor and the associated deflection elements. coil closes with the power source.

3 4

The energy supply for the forward and reverse interval in the deflection coil. In the deflection

Energy consumed during the run takes place at device 21, a first source of electrical energy is in

the circuit according to the invention in two steps: Form of a capacitor 23 on which a ratio-

During the sawtooth trace, the constant voltage is developed.

capable reactance see energy from a con-5 that during the trace interval by means of a

constant current source on (circuits which the controllable switching element 24 of bipolar conductivity

Loss energy is coupled back to the deflection winding 22 during the sawtooth trace,

whole, are in Anglo-Saxon usage The switch 24 consists of the parallel connection

referred to as "trace driven"). During the sawing of a controllable silicon rectifier (thyristor)

Tooth return is now this in the reactance io 25 and a damping diode 26, which is polarized so

stored energy on the deflection coil - that it conducts in the opposite direction as

given (a deflection circuit in which the loss of the thyristor 25. The deflection circuit 21 contains

energy is supplemented during the sawtooth return, also with a second source of electrical energy

is referred to as "retrace driven"). The invention a relatively large inductance 27, which at

According to the circuit, a combination of these 15 now provides a voltage terminal B + of z. B. +150 volts des

represent both principles, namely with regard to the power supply part (not shown) of the receiver

of the last-mentioned circuit part is connected after the last catcher. Between the coil 27 and

mentioned principle works, while one terminal of the switching element 24 is a blind

Consideration of the overall circuit of the first-mentioned resistance element in the form of the series circuit

Principle can speak. 20 of a coil 28 and a capacitor 29 are coupled.

Further features of the invention emerge from the control electrode of the thyristor 25 is a

the subclaims. In the following the invention is a circuit arrangement with an inductive with the

I) on the basis of the illustrations of an exemplary embodiment coil 27 coupled winding 30, a resistor

explained in more detail. It shows 31 and a capacitor 32 connected, by means of

F i g. 1 shows 25, partly shown in block form, of which the thyristor 25 in each case during the forward switching scheme of a television receiver with the invented interval of the deflection oscillation opened (conductive intended Deflection circuit and power) will.

F i g. 2 a series of (not to scale a second controllable switching element 33 with bi-reproduced) Waveform diagrams showing the polar conductivity is between the connection explanations the operation of the circuit after 30 point of the coils 27 and 28 and a reference span-F i g. 1 serve. . coupling point (ground). The switching element 33

F i g. 1 illustrates an embodiment which, like the switching element 24, consists of the parallel invention, as can be used in a typical television circuit of a thyristor 34 and an energy receiver. The television receiver has a recovery diode 35 which, in the opposite direction, conducts an antenna 10 which receives the television signal and which conducts 35 th direction as the thyristor 34.
couples to the receiving part 11. The receiving part is then provided with a circuit arrangement

11 normally contains an RF amplifier, one through which the switching element 33 in each case before the back-mixing stage for converting the RF signals in the IF running interval of the deflection period is made conductive. Signals, an IF amplifier and a demodulator, this circuit arrangement contains the transequipment from the IF signals the BAS signal (signal 40 mator 20, which is the output of the horizontal oscillator mixture). The receiving part is a video 19 coupled to the control electrode of the thyristor 34, amplifier 12 connected downstream. Via the series connection of the capacitor 23 and

The increased luminance component (image sacred deflection winding 22 is a capacitive voltage

component) of the output of the video amplifier 36 with the two capacitors 36 a and 36 &

kers 12 appearing signal mixture is switched to 45. The connection point of the capacitors

Control electrode (e.g. the cathode) of the picture tube 13. 36 a and 36 & is coupled to the phase detector 18

The composite signal is also pelted by the video amplifier to the latter for the purpose of controlling the oscillator 19

12 to supply the amplitude sieve (synchronization signal separation with return pulses).

stage) 14. The amplitude sieve 14 supplies the vertical deflection generator 15 with vertical synchro- 50 generated return pulses at the capacitor 36 b of the voltage distributor 36, which are based on the nisierimpulsen from the. The signals generated by the vertical deflection generator 15, the horizontal oscillator 19 (with a downstream vertical deflection stage 16 that feeds the nominal frequency of 15750 Hz according to the vertical deflection winding 17 of the applicable standards in the USA terminals YY ' ) are supplied to the phase picture tube 13 with deflection energy. detector 18 fed. These return pulses (or

The signal sequence derived therefrom obtained by the amplitude sieve 14 is passed in the phase-zonal synchronization pulses to a phase detector 18 with the detector 18 supplied by the amplitude sieve 14, to which a second signal is also drawn, compared with the horizontal synchronization pulses. The result is that a corresponding error oscillator 19 is related to the oscillation frequency of the horizontal phase detector 18 generated. The voltage in the phase detector 18, which is fed to the horizontal oscillator 19 by comparing the two signals, is generated in order to control its phase and frequency,
The output pulses of the oscillator 19 are so lator 19 with the horizontal synchronization pulses or treated so that positive pulses synchronize. The output oscillation of the Hori- result, the z. B. a width of 3 to 7 microzontal oscillator 19 reaches a transformer seconds, a repetition frequency of 15,750 Hz and a 20 to the inventively designed horizontal 65 predetermined phase position with respect to the line deflection circuit 21 have scanning or line retrace interval.

The deflection circuit 21 feeds the horizontal The positive pulses thus formed are of deflection winding 22 with a sawtooth current with the secondary winding of the transformer 20 on the

Control electrode of thyristor 34 coupled. The thyristor 34 initiates a sequence of processes that cause that every time a pulse reaches the control electrode of this thyristor, the return of the Horizontal deflection period is generated.

In Fig. 2 current and voltage curves are shown, which at different points in the circuit according to FIG. 1 appear during a distraction period. The forward of the deflection period comprises the time interval from t ₀ to t _s , while the return comprises the interval from t ₅ to t ₀ '. According to the standards applicable in the USA, typically have the interval from i ₀ to t. a duration of about 53 microseconds and the interval from t _s to t ₀ ' a duration of about 10.5 microseconds.

The operation of the first or trace switching element 24 in the horizontal deflection circuit 21 will now be considered. This switching element 24 serves to switch a constant voltage source (capacitor 23) via the deflection winding 22 while the deflection period is running. In fact, at time t ₀ (start of the trace), a current (signal profile A) of maximum amplitude flows in deflection winding 22 in the direction, for example, from terminal X to terminal X '. The voltage across the series connection of winding 22 and capacitor 23 (signal curve J5) then passes through the zero value and is reversed. When the polarity of this voltage is reversed, the diode 26 in the switching element

24 conductive, so that the essentially constant voltage (e.g. + 50VoIt) applied to capacitor 23 is developed, arrives at the deflection winding 22.

As a result, during the first half of the trace (i ₀ to t ₂ ), the current in the deflection winding 22 (signal curve A) drops essentially linearly towards zero, as a result of which the capacitor 23 is supplied with energy. The capacitor 23 is dimensioned so large that the voltage across it does not change significantly. Approximately (ie, at time t ₂₎ in the center of trace returns the current in the deflection winding 22 (waveform A) its direction and turns on the snubber diode 26 25 to the thyristor In preparation for this switching of the current paths of the thyristor 25 during the first half of the trace by a control signal (signal curve G), which is supplied via the winding 30, the resistor 31 and the capacitor 32, set in a standby state.

The manner in which the control signal is generated will be described. The polarity of the part of this control signal falling in the outward path is selected so that the thyristor 25 can conduct when a voltage in the forward direction is applied to its anode-cathode path. This happens approximately in the middle of the trace (z. B. at t ₂ ), so that at this point in time the deflection current is switched from the diode 26 to the thyristor 25. The deflection current in winding 22 then increases during the second half as it passes through the thyristor

25 flows, essentially linearly. Energy is drawn from capacitor 23 during this interval and transferred to deflection winding 22.

In order to end the outward flow and to initiate the reverse flow, the thyristor 25 must be blocked. A thyristor can be blocked by reversing the direction of the current in the anode-cathode path and the anode-cathode junction a reverse voltage over a sufficiently long time interval is supplied to remove all stored charge carriers from the transition zone. In the Deflection circuit 21 should accomplish these operations without the desired smooth transition from the im essential linear outgoing current to reverse the direction of the current disturbed during the return or is torn.

Approximately 5 microseconds before the end of the trace (ie at t ₃ ) , the des

ίο thyristor 34 an output pulse (waveform H) of the oscillator 19, whereby a sequence of processes is initiated, which causes the return. In fact, when the thyristor 34 is gated (made conductive) by the oscillator 19, a circuit is closed by the first switching element 24, the second switching element 33, the coil 28 and the capacitor 29. The current in deflection winding 22 (waveform A) continues to rise linearly, since switch 24 remains closed.

At the same time, considerable energy, which has previously been stored in the capacitor 29, flows in the aforementioned circuit with a resonance frequency determined by the values of the capacitor 29 and the coil 28. Initially, a current (waveform D) flows in this circuit in the forward direction through the thyristor 34 and in the reverse direction through the conductive thyristor 25, through which a larger forward current (from the winding 22) also flows.

However, the resonance current rises faster than the deflection current, so that after a certain time interval (for example 2 to 3 microseconds) the resulting current in the thyristor 25 is reversed (signal curve C). The thyristor 25 is switched off. The resonance current, which continues to rise, then switches to the diode 26 for a short time interval until the deflection current and the resonance current are equal again. At this point in time, the diode 26 and the thyristor 25 are both switched off (ie switched to the high-resistance state), whereby the winding 22 is switched off from the constant voltage source (ie the capacitor 23). The retrace interval begins at this point in time (i _5).

The time interval (i ₄ to t ₅ ) during which current flows through the diode 26 is dimensioned in its duration so that it is sufficient to remove all stored charge carriers in the thyristor 25, so that it is ensured that the thyristor 25 lasts as long remains switched off until the required readiness key pulse reaches its control electrode during the run-out of the next deflection period.

During the return, the switch 33 couples the coil 28, the capacitor 29 and the Deflection winding 22 existing reactance components to a series resonant circuit, wherein the capacitor 23 can be neglected because of its large capacity. The resonance period of the three components is chosen so that it is twice as long as the desired retrace interval. the Current in the deflection winding 22 therefore passes through half an oscillation period, thereby creating the desired This current is reversed in direction and thus the beam return in the picture tube 13 is achieved.

Since the thyristor 34 is a unipolar conductive component (only conductive in one direction) is connected across it the diode 35 to make the switch element 33 bipolar conductive, so that the

Deflection current can reverse its direction. If the current flow through the switch 33 reverses its direction (at i ₆ ), the thyristor 34 is blocked. The duration of the current flow through the diode 35 (approximately half the retrace interval) is more than sufficient to ensure that all charge carriers are removed from the thyristor 34 and that the thyristor is properly switched off or blocked.

The energy exchange relationships that exist during and immediately after the return, including the way in which in preparation for the initiation of the return energy in the Capacitor 29 is stored are from. of particular interest and should now be explained.

At the beginning of return (i ₅ ), the currents in deflection winding 22 (waveform A) and in coil 28 (waveform D) are significant and of the same value (any difference is quickly eliminated because both components are in series at this point in time ). These currents embody energy that is stored in the inductive components mentioned. At the same time, the capacitor 29 also stores some energy at the beginning of the return, since the current in the coil 28 and in the capacitor 29 has dropped from its peak value (signal curve D) and some voltage is present on the capacitor 29 (signal curve E).

When switch 24 is opened (at t ₅ ), the energy stored in deflection winding 22 and inductor 28 is transferred to capacitor 29 during the first half of the retrace, whereupon all of the energy stored in capacitor 29, including that at the beginning of the return has been stored, while the second half of the return flows back into the deflection winding 22 and the inductance 28. At the end of the return flow, practically no more energy is stored in the capacitor 29.

During the entire retrace interval and immediately before this interval (ie from f ₃ to i ₀ ') the second switch 33 is closed, so that the inductance 27 is coupled directly via the supply voltage B +. During this interval, the current in the coil 27 increases essentially linearly, so that a considerable amount of energy is stored in this coil 27.

At the end of the retrace (at i ₀ '), when the voltage on the deflection winding 22 has run through essentially half an oscillation period, the diode 26 is again charged in the forward direction. When the diode 26 is switched on, the current in the deflection winding 22 again assumes its linearly increasing course. At the same time, the residual energy stored in the coil 28 (signal curve D) is transferred very quickly (from t ₀ ' to t _± ') to the capacitor 29 via the diodes 26 and 35. At the end of this energy transfer, the diode 35 (and consequently the switch 33) is opened. It should be noted that the switch 33 _{remained closed during the interval from i 3} to t ( . The coil 27 then begins to transfer its energy via the switch 24 to the capacitor 29 (signal curve E). During the interval from t _x to i ₃ is transmitted enough energy from the coil 27 into the capacitor 29 to make up the circuit losses incurred during the previous sweep period again. This energy is then from the capacitor 29 during the retrace

mostly delivered into the winding 22, as already mentioned.

The control signal supplied to the thyristor 25 (signal curve G) is generated in the following way: the voltage on. of coil 27 and consequently the voltage at coil 30 has the form of a square-wave voltage with level jumps near the beginning (at J ₁ ) and near the end (at i ₃ ) of the trace when the switches 33 and 24 switch over, ie change their state (Signal curve F). After filtering in the network consisting of the resistor 31 and the capacitor 32, the square-wave voltage for the supply to the control electrode of the thyristor 25 is modified so that it assumes a curve with a relatively slow rise and fall. As already mentioned, the polarity of the main part of the voltage during the trace is chosen so that the thyristor 25 can conduct when its anode-cathode path is forward-biased.

The control signal for the thyristor 25 can of course be obtained in various ways. For example can this control signal as well as the control signal for the thyristor 34 by the oscillator 19 can be delivered.

To enable the operating intervals to be set, certain components of the circuit (e.g. coil 28) can be made variable will.

A high voltage generator circuit (not shown) for generating the high voltage for the end anode the picture tube 13 can be coupled to the deflection circuit 21 in various ways. For example .can be the primary winding of a flyback high voltage transformer effectively shunted via switch 24, with upward transformed flyback pulses emanating from a secondary winding of the transformer are removed, fed to a high-voltage rectifier to reduce the To gain terminal anode DC voltage.

An embodiment of the circuit according to FIG. 1 which has been tried and tested in practice with a satisfactory result. 1 is equipped with the following components:

Deflection winding 22 ... 1.1 millihenry

Capacitor 23 1 microfarad

Thyristor 25 RCA type TA 2688

Diode 26 Genenral Instrument

Type RG 100 G

Coil 27 40 millihenry

Coil 28 150 microhenries

Capacitor 29 0.015 microfarads

Thyristor 34 RCA type TA 2688

Diode 35 Genenral Instrument

Type RG 100 G

Claims (8)

Patent claims: 1. Circuit arrangement for generating a periodic sawtooth current in a coil, in particular the deflection winding of a television picture tube, in which you in a first branch Coil via a first controllable switch, which is conductive in both directions, on an energy 009 547/29 storing current source is, the controllable switch is formed by the anti-parallel connection of a controllable rectifier with a diode and the control electrode of the rectifier is connected to a control pulse source, which makes the switch conductive during part of the sawtooth trace, and in which the sawtooth return with the help of a second controllable switch is initiated, characterized in that the first controllable switch (24) is also part of a second current branch which is connected in series with the switch (24) to a second current source (B +, 27) and an oscillating reactance (28,29) which takes energy from the second current source during the middle part of the sawtooth trace when the switch (24) is closed and periodically again by means of the second controllable switch (33) towards the end of the sawtooth trace from the second current source (B +, 27) to form an oscillating circuit is separated, d expects that due to the natural oscillation of the reactance (28, 29) the current in the first switch (24) is reversed a first time, with its controlled rectifier (25) being blocked, and reversed a second time, with its diode (26 ) is blocked, and the reactance (28, 29) is thereby switched to the series connection of the first current source (23) with the coil (22) of the first current branch and with this series connection executes the return oscillation while compensating for the coil losses that occurred during the sawtooth approach. 2. Circuit arrangement according to claim 1, characterized in that the reactance consists of the series connection of an inductance (28) with a capacitance (29). 3. Circuit arrangement according to claim 1, characterized in that the second controllable Switch (33) also has a controllable rectifier (34) which, by reversing the current the return oscillation is blocked. 4. Circuit arrangement according to claim 3, characterized in that the controllable rectifier (34) of the second controllable switch (33) also has a diode (35) connected in anti-parallel. 5. Circuit arrangement according to claim 1, characterized in that the second current source (B + , 27) is formed as a constant current source from the series connection of a direct current source (B +) with a storage inductance (27). 6. Circuit arrangement according to claim 5, characterized in that the storage inductance (27) is designed as the primary winding of a transformer, the secondary winding of which has a consisting of a 7? C element with a series resistance (31) and a transverse capacitance (32) Delay circuit serves as a control pulse source for the first switch (24). 7. Circuit arrangement according to claim 1, characterized in that the first current source is formed by a storage capacitor (23) of large capacity. 8. Circuit arrangement according to claim 1, characterized in that the control pulse source for the second controlled switch (33) comprises a synchronizing signal source (14) that with the by the first controllable switch (24), the "Coil (22) and the current source (23) formed circuit are connected to a feedback circuit (36) is which, corresponding to the current flowing through this circuit, feedback signals to one in the control circuit of the second Rectifier (34) lying phase comparison circuit (18) leads, which accordingly the phase and frequency differences between the fundamental wave of the synchronous signals and the Feedback signals control signals for a second controllable switch (33) controlling Oscillator (19) supplies. 1 sheet of drawings