DE2508991A1 - CIRCUIT ARRANGEMENT FOR GENERATING A SAW-TOOTH-SHAPED DEFLECTIVE CURRENT - Google Patents

Description

PHN.7 ^ 32

wij / fk / minc

February 15, 1975

PHN-7432
Feb. 27, 1975

"Circuit arrangement for generating a sawtooth-shaped Deflection current. "

The invention relates to a circuit arrangement for generating a sawtooth-shaped deflection current with a forward and a return through a deflection coil, which circuit arrangement has a first and a second Switch and includes a network that is between a first electrode of the first and a first electrode of the

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PHN. 7V32

February 15, 1975

second switch is arranged, the first switch during the trace time, the deflection coil to a trace capacitance connects.

Such a circuit arrangement is known from U.S. Patent 3,517,253 known and provides for the Horizontal deflection in a picture display device. This is the connection point of the network with the first one Electrode of the second switch connected to a terminal of a supply voltage source via a charging inductance. In this inductance energy taken from the source is stored during part of the period, which - energy then transferred to the network and finally to the outbound capacity in the return time to compensate for losses is delivered. Stabilization is obtained in that the inductance value of the charging inductance is controllable, which leads to that of the deflection circuit absorbed energy is controllable.

Such an inductance not only takes up a lot of space and is expensive, but it is itself the cause of significant energy losses. Because besides sudden voltage and current transitions in the arrangement occur when the switches become conductive or block, arise in the inductance with the stray capacitances unwanted high-frequency vibration phenomena. It is true that the amplitude of the same can be determined by means of damping networks can be reduced, but such networks affect the

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"3" PHN. 7 ^ 32

February 15, 1975

respective adjustments in the arrangement, what the design of the same and in particular a high voltage transformer difficult, and they cause further and unnecessary energy losses. The invention now aims to address these disadvantages avoid, and the circuit arrangement according to the invention has the indicator that between a terminal of a supply voltage source and the connection point of the Network with the first electrode of the second switch, a third controllable switch without interconnection a charging inductance is added.

The recorded between the first and the second switch network can be from the series circuit of a Inductance and a capacitance exist. It is a finding of the invention that this inductance because of the same Disadvantages as above can be omitted and the circuit arrangement according to the invention, the first Switch contains a controllable element which is supplied with a control signal for reversing the deflection current in the trace time gets, whereby it can be brought into the conductive state, can have the further characteristic that the network consists of a capacitance and that a second controllable element in the first switch is anti-parallel to the controllable element Element that is brought into the conductive state around the beginning of the trace time. This contains the circuit arrangement does not have any other inductance than that optionally coupled by means of a transformer Deflection coil.

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PHN.

February 15, 1975

Embodiments of the invention are shown in the drawings and are described in more detail below. Show it:

1 shows a first embodiment of the inventive Circuit arrangement,

Fig. 2 waveforms appearing therein

3 shows a second embodiment of the inventive Circuit arrangement,

Fig. H waveforms appearing therein.

In Fig. 1 is in a television receiver

positive terminal 1 of a supply voltage source connected to the anode of a thyristor T_ ,, while the negative terminal 2 of the source is connected to the ground of the receiver. The cathode of the thyristor T "is connected to the series network of a coil Lp and a capacitor C and to an electrode of a switch S". The other end of the network Lp, C is connected to one electrode of a switch S ₁ and one end of an inductance L , the other end of which is connected to a capacitor C i. The free ends of the

"C

Switch S ₁ and Sp and the capacitor C are connected to ground.

The circuit diagram according to FIG. 1 is greatly simplified, which means that the inductance L _{1 can be} regarded as the horizontal deflection coil of the television receiver, not shown further, although it can in reality be the primary winding of a transformer. Similarly, the capacitance of the capacitor Q is very high

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assuming large, i.e. without taking into account the so-called S-correction, and other elements necessary for the present Invention are not important, such as a linearity or a centering circuit, are of simplicity omitted for the sake of

The switch S ₁ or S "consists of the antiparallel connection of a thyristor T ₁ or T" and a diode D or D ", the anode of the thyristor T ₁ or T" with the cathode of the diode D ₁ or D_ and the cathode of the thyristor T ₁ or T _{0 is} connected to the anode of the diode D ₁ or D_.

At the beginning t of the trace time, the diode D is ₁

conductive. The capacitor C, behaves as a source of con-

constant voltage, so that a deflection current i flows through the coil L. which has a linear profile as a function of time. At a point in time t, approximately in the middle of the trace time, the current i becomes zero, after which it reverses its direction. As a result, the diode D ₁ blocks and the current i through the thyristor T _{1 is} fixed. A condition for this is that the same gate receives a positive pulse, namely at a point in time before the point in time t_. At the end t of the trace time, the current i assumes its maximum value.

At a point in time t "before the point in time t_, the thyristor T_ is activated by means of a positive pulse brought into the conductive state at its gate. in the

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Series network L_, C occurs a free oscillation with a Frequency higher than the horizontal frequency. A current χ flows through the network, the direction of which through the thyristor T is opposite to that of the current i is. The course of the two currents as a function of time is plotted in FIG. 2a, while FIG. 2b shows that of the current i through the thyristor T _, - Fig. 2c that of the current i

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through the diode D_ and FIG. 2d that of the current i, _ specify the thyristor T ".

At a time t. shortly after the point in time t “, the current i becomes greater than the current i: der _j c y

Thyristor T ₁ stops conducting and the two currents flow through diode D ₁ . After the current i has reached a maximum, it decreases again, after which its size again becomes the same as that of the current i. The time t 1 and the tuning frequency of the network L _p , C have been selected in such a way that this takes place at the end time t of the trace time. At time t, therefore, the diode D ₁ blocks, while the thyristor T ₁ remains blocked, since there is no longer any positive voltage at its gate. The elements C., L ₁ ,

t I

C, L ₀ and T "are now in series, the tuning frequency having been selected in such a way that half a period almost corresponds to the desired duration of the return of the horizontal deflection current.

Under these circumstances, a sinusoidal shape arises at the connection point of the coil L ₁ with the capacitor C

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February 15, 1975

Voltage ν (see Fig. 2e) of high amplitude, which reaches its maximum value at time t-ς in the middle of the flyback time. Between the times t "and ts , the current i = i flows through the thyristor T". At time tg this current becomes zero and reverses its direction, whereby the thyristor T blocks and the diode D becomes conductive. At a point in time t ¹ , the voltage ν is zero, the diode D ₁ becomes conductive: t 'is therefore the starting point in time of a new trace time.

After the point in time t ', the current i flows

through the diode D _? , the network L ₂ , C and the diode D ₁ , through which the current i also flows. Despite the fact that the two currents through the diode D _{1 have} opposite directions, this diode can be conductive because the current i due to the losses brought about

Phase shifts in absolute value is smaller than that Current i.

At a point in time t · the thyristor

T "brought into the conductive state by means of a positive pulse at its gate, as a result of which the voltage at its cathode rises fairly quickly to almost the voltage V_ of the supply source. The diode D ₂ can no longer conduct, and its task is taken over by the thyristor T ". Of the

Current i decreases and becomes zero at a point in time t'_, ^c /

after which it would turn back: the thyristor T “therefore listens derive on, and the state in which to the left of the

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Switch S shown part of the circuit arrangement does not change until time t 'when the thyristor T is brought into the conductive state again, which time t 'occurs one line period later than the time t “.

Energy to make up for losses

Supplied by the supply source during the conduction time t 'to t ^! of the thyristor T "and" is the one in Fig. 2.6. hatched surface proportionally. The amount of energy supplied can therefore be set in that the point in time t ″ is selected, for example, to set the voltage on the capacitor C, whereby the maximum strength of the deflection current is also set 1. This voltage is fed to a modulator 3 in which pulse position modulation takes place in a known manner. occurs.

The point in time t ¹ can occur at the earliest at the point in time t ^ at which the diode Dp begins to conduct, in reality at the point in time after the point in time tr at which the switching off of the thyristor T "has ended. At the latest, the point in time t · .. can occur ^{simultaneously with the point in time t 1.} In Fig. 2c, d and e is indicated by

_ 9 L

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Dashed lines show the position when the thyristor T is brought into the conductive state _{at a time t 1 before time t.} Because the voltage at the cathode of the thyristor T "then from zero to almost V-,

J ο

jumps, the voltage ν jumps as well, namely by an amount that is dependent on _{the inductance values of the inductances L 1 and L.} From FIG. 2e it should be evident that the delay time will start later than in the case where the point in time t 'occurs after t ¹ , the delay being dependent on the regulation and therefore being variable. A regulation after time t ¹ is recommended.

In Fig. 1, the control circuits of the thyristors T ₁ and T _? not specified, since the control of the same can be realized in a known manner. Any additional tuning capacitors, for example in parallel with switch S ₁ , are also not specified, nor is the manner in which auxiliary supply voltages and the high voltage for the end anode of a picture display tube are generated. will. This can be carried out in a known manner with the aid of one or more windings of rectifiers coupled _{to the inductance L 1.}

In the same way also Fig. 3 is a highly simplified circuit diagram of another embodiment of the inventive circuit arrangement is, with respect to FIG. 1, the coil L _p is fallen away, while the diode D ₁ by a thyristor T "with the same managerial

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direction has been replaced. For the sake of clarity, the thyristor T ₁ according to FIG. 1 is now called T '. The course of the deflection current i as a function of time is plotted in FIG. 4a, while FIG. 4-b shows that of the voltage v _v

at the cathode of the thyristor T ~, Fig. 4c that of the voltage ν at the connection point of the coil L ₁ with the capacitor C, Fig. kd that of the voltage ν on this capacitor and Fig. He that of the current I ^ through the thyristor T_ .

3 ' ^J

¥ ¥ during the first half of the outbound time

i flows the current through the thyristor T "and after the time t is about in the middle of this time fliesst- this current through the thyristor T ^1, gets supplied to a positive pulse before this time the gate. In Fig. kc is the same as in Figure 2e, the voltage across a conductive thyristor or a conductive diode has been neglected. In reality, the voltage ν after time t is somewhat positive, so that the thyristor T ″ ... as well as the diode D ₁ in FIG then locks.

At the point in time t at the end of the trace time

the thyristor T_ brought into the conductive state by means of a positive pulse at its gate. Because the voltage on the capacitor C at this point in time has the polarity indicated in FIG. 3, current can actually flow through the thyristor T "while the thyristor T 'blocks. The elements C ,, L ₁ , C and Tp are now in series, the tuning frequency has been chosen such that half a pe-

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period of the desired duration of the return of the deflection current almost corresponds.

In the same way as in Fig. 1, the flows. Current i between times t and t, - through the Thyristor T "and after the time t ^ through the diode D".

Because the voltage V _x ^ jumps to almost zero at time t _c,

K ₃ 5

the voltage ν jumps with a value corresponding to -V_, while the voltage ν cannot change abruptly. At time t / - the voltage ν reaches its maximum value and in one

At time t ¹ , it takes the value -V _{x again} . at. In this ο α

Time the thyristors T "and T" are simultaneously in brought the conductive state, whereby the voltage ν after

V jumps while the voltage ν jumps to zero. In order to ± J

the new forward time begins. Because the voltages at the gate and at the anode of the thyristor T "correspond to one another, the current i can only flow for a very short time. Of the

3
Capacitor C remains charged and flows through it during

no power for the entire run-out time.

The above is true in the theoretical case where the circuit arrangement is lossless. In practice, energy is supplied by the supply source in order to compensate for losses in that the thyristors T_ and T ¹ V _{1 are} not brought into the conductive state at the same time, in the sense that the thyristor T "is switched on before time t ' . Just as in FIG. 1, the energy supply can be adjusted by means of a modulator 3.

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Auxiliary supply voltages and the high voltage

can with the circuit arrangement of FIG. 3 on known Wise generated, for example with the help of the inductance L coupled windings and / or with the help of a Transformer in series with a capacitor, the series circuit formed in this way being connected in parallel to the capacitor G.

The circuit arrangement according to FIG. 3 offers

Compared to the known arrangement according to FIG. 1 and also compared to the above-mentioned known arrangement, the point in time at which the thyristor T is brought into the conductive state initiates the return flow, during the initial point in time of the return time in the two other arrangements the time t_ in FIG. 2 and by the tuning frequency of the network L, C in FIG. 1 is determined, so that the interval t "to t" is not well controlled. The diode D in FIG 3, since the jump in FIG. Hc at time t would bring a diode into the conductive state, whereby the capacitor C would be short-circuited by the thyristor T 1 and the diode and consequently a very strong current would be traversed.

The two described embodiments according to

¹ , 1 and 3 have in common the fact that the energy " ¹ I fulir comes from the supply source without charging inductance, this function being fulfilled by a thyristor,

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which thyristor has a second function, namely switching off the diode in the second switch. Another embodiment is conceivable, in which case such a charging inductor would be included in series with the thyristor T between the terminal 1 and the switch S in FIG. However, it should be clear that in this embodiment not only the disadvantages mentioned at the beginning occur, but also that the diode D "would not block immediately, which would lead to the elements D ₂ , C and T" ^{causing after the time t 1} Current would flow, whereby the thyristor T "could block. In Fig. 1 as well as in Fig. 3, a coil can be included in series with the thyristor T ~ for purposes other than storing energy, for example to suppress high-frequency radiation caused by transitions, insofar as such a coil does not have any appreciable effect of the arrangement influenced and therefore cannot be regarded as charging inductance.

1 and thyristors have been selected as controllable elements. It should be evident that these elements can be replaced by other known controllable elements, for example transistors.

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Claims (1)

. PHN.7 ^ 32 PATENT CLAIMS: 1 . J Circuit arrangement for generating a saw Tooth-shaped deflection current with an inlet and a return by a deflection coil, which circuit arrangement includes a first and a second switch as well as a network which is arranged between a first electrode of the first and a first electrode of the second switch is, wherein the first switch connects the deflection coil to a trace capacitance during the trace time, thereby characterized in that between a terminal of a supply voltage source and the connection point of the network with the first electrode of the second switch, a third controllable switch without the interposition of a charging inductive! did is recorded. Z. Circuit arrangement according to claim 1, characterized marked that the network is out of the series connection consists of an inductance and a capacitance. 3 · Circuit arrangement according to claim 1, wherein the first switch contains a controllable element that sends a control signal to reverse the deflection current in the trace time gets fed, whereby · this element in the conductive State can be brought, characterized in that the network consists of a capacitance and that antiparallel to the controllable element in the first switch - 15 5 0 9 8 3 8/0637 PHN.7 ^ 32 second controllable element is located, which is brought into the conductive state around the beginning of the trace time. k. Circuit arrangement according to Claim 1, characterized marked that the time interval in which the third Switch is conductive, is adjustable. 5 · Image display device with a circuit arrangement for generating a horizontal deflection current according to one of the preceding claims. 509838/0 6 37 - 16 - Blank page