DE2852942A1 - PICTURE DISPLAY ARRANGEMENT, INCLUDING A SWITCHED SUPPLY VOLTAGE CIRCUIT - Google Patents

Description

July 20, 1978 / PHQ 77-008

"Image display device containing a switched supply voltage circuit".
(Addition to patent application P 23 60 025.1)

The invention relates to

A picture display device, containing a switched supply voltage circuit for converting a DC input voltage into a DC output voltage, which is _{almost independent of changes in the input voltage and / or changes (} a load connected to the terminals of the output voltage _s with the series connection of the primary winding of a transformer and a controlled switch, which series circuit is connected to the terminals of the input voltage and to which primary winding a tuning capacitor is connected in parallel, with furthermore a control circuit for alternately bringing the switch into the conduction or blocking state during operation, the duration of which can be regulated depending on the output voltage and wherein a secondary winding of the transformer is connected to a rectifier which supplies the output voltage, wherein the picture display device further comprises a horizontal deflection circuit, the supply energy from the switched n food gets voltage circuit, contains.

In such a switched

Supply voltage circuit with coordination is applied to the primary winding of the transformer during the blocking time of the Switch produces an essentially sinusoidal oscillation

.25 testifies. With the vote it is achieved that the tension

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not too high at the switch during its blocking time becomes, and at the same time there are vibrations that would arise with stray capacitances and undesired radiation could cause, avoided. Yeil the tuning frequency difficult and can only be controlled by means of rather expensive elements, e.g. transducers, can with a regulation of the conduction duration of the switch, the frequency of the S ehalt inipulse supplied to it is not constant be. In a picture display device, for example a television receiver, if the horizontal deflection circuit is fed by the switched supply voltage circuit, the difference between the constant Horizontal deflection frequency and the variable switching frequency cause difficulties in smoothing out the

1 ^s output voltage, for example the high voltage for a picture display tube, of the supply voltage circuit.

The invention creates an image display arrangement which does not have this disadvantage and which is characterized in that the voltage present at a trace capacitor is fed to the primary winding of the transformer by means of the controlled switch and a first diode connected to the switch in such a way that the primary winding of a sawtooth-shaped. Current with the horizontal frequency flows through, which during a first part of its trace time through the first diode and during the other part of the trace time, during which the controlled switch is conductive, flows through a second diode and the switch, which second diode is connected in parallel to the series circuit of the switch and the first diode ^{, a current originating from a terminal of the input voltage through an inductance (L f} ), which is connected via a third diode to the resonance circuit formed by the primary winding, the tuning capacitor and the trace capacitor flows during the conduction time of the switch, as a result of which energy is stored in the inductance, while one flows during the blocking time of the switch through the inductance and the third diode

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Electricity compensates for energy losses.

It should be noted that FIG. 5

DE-OS 23 60 025 shows a circuit that essentially a combination of a switched supply voltage circuit and a horizontal deflection circuit, with a common one for the two circuit functions controlled switch is used. There is a circuit arrangement with one of one sawtooth-shaped current flowing through it, part of a also an inlet condenser and a return condenser containing resonance circuit forming coil, in particular Horizontal deflection coil in a picture display arrangement, to stabilize the voltage on the trace capacitor, which during the trailing time of the sawtooth-shaped ' Current is applied to the coil by means of a first diode and by means of one of these via a second diode switch connected in parallel, whereby during the Closing time of the switch from a voltage source A current flows through an inductive element and as a result during the switch-off time the stored magnetic energy of a winding of the inductive element via a third to the resonance circuit connected diode current flows and whereby the from the G-I e i ch voltage source supplied to the switch Current flows through said winding at the same time. So the inductive element is simultaneously through the winding formed so that both the inflowing from the source of food how the current transferred into the sawtooth circuit with the coil flows through the rich winding and thereby losses due to leakage inductances, as they are with separate Windings occur are avoided. The inductive element is between the "supply source and the." Switch connected so that the the inductive element Direct current flowing through the switch flows and the coil is only traversed by a sawtooth-shaped current. In contrast, with a circuit s in order according to the invention, the inductive element between the supply source and the switch averted

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PHQ 77.008

connected to the th end of the spool. Since this is a Feed circuit acts in which the inductive element occurring voltage, e.g. transformer, taken and used for the DC voltage supply of further stages a direct current supplied via the inductive element is not disturbing, on the contrary, this is immediately with the connected DC consumers fed. Only part of the energy required on the secondary side is stored in the inductive element and transmission to be fed during the blocking time of the switch, so that the inductive Element can be small.

An embodiment of the invention is shown in the drawings and will described in more detail below. Show it:

Fig. 1 is a circuit diagram of a circuit arrangement according to the invention,

Fig. 2 waveforms to explain the operation of the circuit arrangement.

. The switched supply voltage circuit from FIG. 1 shows a switching arrangement in the form an npn transistor Tr whose collector is connected to one end of the primary winding L of a transformer T. The other end of the winding L is connected to one end of a choke L ', the other end of which is connected to the positive one Terminal of a DC voltage source Vp. Is connected while the emitter of the transistor Tr is connected to the negative terminal of the source V-. The source V_ is for example a rectifier circuit that supplies the AC voltage rectifies the electrical supply network.

The anode of a diode D ^ is with

connected to the negative terminal, while the cathode of a diode D "is connected to the positive terminal. The cathode of the diode D "is connected to the anode of the diode D" and the anode of a diode D ₁ , the cathode of which is connected to the collector of the transistor Tr. The connection point A between the three diodes is via a trace capacitor C ₁ with the connection point between the

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Choke L ^f and the primary winding L connected, while a flyback capacitor C ″ is arranged parallel to the winding L.

A driver stage Dr for delivering stop pulses is connected to the base of the transistor Tr, the repetition frequency of this stage being that of the horizontal time base of a television receiver, not shown corresponds, of which the feed circuit in Fig. 1 forms a part. Horizontal frequency signals, which are generated in a known manner, are for this purpose the stage Dr fed.

During a first part of the

During the horizontal period, the diode D _{1 is} conductive, while the transistor Tr is blocked. A stream d. St flows through the primary winding L and also through the capacitor C ₁ and the diode D ₁ . If the capacitance of the capacitor C _{1 is} large enough, it can be said that the voltage V _n across it is at least almost constant during the entire horizontal period, so that the change in the current: L, which change is shown in FIG. 2a, during the

Partly t - t "of the trace time. when the diode D _{1 is} conductive —ο —2 ι

can be viewed as nearly linear. At the same time, the energy stored in the choke L 'by a current i', which current flows through this choke during the previous time, causes this current: L ^{1 to be} maintained. The current ± * also flows through the capacitor C ₁ and the diode D "with an almost linear change (decrease), as is shown in FIG. 2b. Because the two diodes D ₁ and D "

are conductive, the voltage at the collector of the blocked transistor Tr corresponds almost to the value + V, -. with respect to the voltage at the negative terminal of the source, which is the reference voltage of the circuit arrangement, and the voltage at the connection point t A (FIG. 2c) also corresponds to the value + V _1,.

At a point in time t ₁ , the

Transistor Tr by a switching pulse, which is its base is supplied and originates from the driver stage Dr,

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tend. The current _i flows in the same way as it _{flowed before the moment Js 1} , but the current i ¹ now flows through the capacitor C ₁ , the diode D ₁ , the transistor Tr and the source V_. The two currents -i and -ji ¹ consequently flow through the diode D ₁ . Before the time _t ..

the current i ¹ decreases, while it increases after the time point t. The voltage at the collector of the transistor Tr, and therefore the voltage at the point A, becomes almost zero at the time t, so that the voltage

—-J

at the connection point between the choke L 'and the winding L, which occurred before time t. was equal to V ₁₃ + V after

- "I Jü ο

becomes equal to V at this point in time. The voltage at the throttle L ¹ was equal to -V when in Flg. 1 is seen from the right-hand side to the left-hand side of the throttle and now assumes the value V “-V, which determines the slope of the positive flank from FIG. 2b.

From the above, it should be evident that the circuit arrangement is supplied by the current i 'after time t _{1 with} energy which compensates for the losses and loads to which power is supplied. A satisfactory effect is obtained if dex current ^ 'does not become zero during the period, that is to say if the inductance of the choke L' is selected in a certain way.

Because the inductance of the winding L is much smaller than that of the reactor L ¹ , the current d. Zero. This takes place at a point in time t after the point in time t., After which point in time the current i reverses its direction and consequently in the direction that of the current i. Opposite ¹ is flowing through the diode D _1, the voltages at the inductor L ^f and L of the winding remain the same as before the time t _o, that is V_ - V _n or '. V.

- / c JtS U O

A short time after the time _t_

and during the trace time at a point in time when the two currents flowing through the diode D ₁ fHessen have the same absolute value, the diode D does not conduct. The current ji ¹ now flows through the winding L and the transistor Tr, while the current i through the transistor Tr, the

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Diode D "and the capacitor C ₁ flow. This situation . and the voltage considered above also remains unchanged as long as the traasistor Tr is conductive.

At a certain point in time, the base of the transistor Tr is supplied with a negative voltage, as a result of which the transistor Tr blocks at the point in time _t ", which point in time is the end of the run-in time and the start of the run-down time. The two currents shown in FIG. 1 continue to flow in the same direction as vas? · Her, but only decrease in value. The current i. ' flows again through the capacitor Cj and the diode D ", so that the voltage at the connection point A to almost the value Vj, zurückkelir-t-, while the voltage at the connection point between the choke L ^f and the * primary winding. L assumes the value Vo + Vq. The voltage at the choke L ¹ again corresponds to the value -V _n , and the current _i 'decreases in an almost linear manner.

After the point in time _t ", the current _i flows through the capacitor C_. This capacitor has been chosen with such a capacity that he with winding L and other inductances in parallel with it forms a tuned circle whose tuning frequency higher than the horizontal frequency. This creates an essentially sinusoidal oscillation at the collector of the transistor Tr generates and reaches a maximum value, after which it falls off. The current i drops after the time _t "in an essentially sinusoidal manner, becomes zero at time jfcj, during the ramp-down time, after which he reverses his direction.

Since the capacitance of the capacitor C ₁ is much higher than that of the capacitor C ", the capacitor C _can? can be considered to be parallel to diode D ₁ , which shows that the voltage across this capacitor is essentially zero before time _t ". This voltage becomes zero again at time t_ at the end of the flyback time after time _fc ^, whereby the diode D ₁ becomes conductive again. The oscillation stops, the voltage on the capacitor C ₁ is fed to the winding L, so that

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the stream _i flows through it in an almost linear way. The point in time t ^ is consequently the beginning of a new one Period.

The amplitude of the oscillating voltage which is generated on winding L during the flyback time between times _t "and jfc- is much higher than voltage Vg, depending on the ratio of the time between these times to the entire horizontal period during the voltage , itself, does not change significantly at the ent ¥ L, corresponding to the value V _n during the rest of horizontal period. The amplitude of the return oscillation can be kept within the permissible maximum value of the transistor by a suitable choice of the tuning frequency. Vibrations with essentially the same shape over the horizontal period are generated on the secondary windings of the transformer T. Fig. 1 shows two secondary windings L ₁ and L ", which are connected to the rectifiers D ^ and D_, through which these vibrations are rectified. The DC voltage obtained by the rectifier D_ is smoothed by a capacitor C "and can be used to supply direct current to parts of the television receiver, such as for a horizontal deflection circuit, while the high DC voltage obtained by the rectifier D ^, in a known manner, is applied to the end electrode of a picture display tube (not shown) is fed, which is also part of the receiver. forms. The winding direction of the secondary windings (L ₁ , L_ and L ") and the line directions of the relevant rectifier can be selected in a known manner, so that a

^3t) rectifier conducting either during part of the time interval between times t_ and t _K or during part of the remaining time of the horizontal period. is.

One of the DC voltages generated on the secondary side of the transformer T, for example the voltage at the capacitor C ", becomes the pedal stage e Dr fed back, in which a comparison circuit and a Pulse duration modulators ensure in a known manner that

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the conduction time t .. to t _{o of} the transistor Tr in such a geäxi-

- l -J

it is changed that the voltage at C "and thereby the other DC voltages remain constant. Between the primary and secondary windings of the transformer T may be such galvanic isolation can be obtained that one end of the secondary windings with the chassis of the television receiver DC connected, while the primary winding is connected to the network ^ light current. In such a case, the mentioned feedback path must be added to the Driver circuit containing one or more transformers.

Another secondary winding L "

of the transformer T can be used to operate the horizontal deflection output transistor Tr 'of the television receiver. A condition here is that the transistor Tr ¹ is conductive during at least the second half of the horizontal trace time, while it is known to also be conductive during part or all of the time first half of the same can be conductive without dadux ^ ch the deflection circuit is adversely affected, although it must be blocked during the horizontal retrace time, this time is dependent on the retrace adjustment of the deflection circuit. The transistor Tr 'is of the npn type in FIG. 1, the base line including a coil L ^ in a known manner. The Yickelsense of the winding L "has been chosen such that the return oscillation in the drive signal has a negative polarity. Because of the action of the coil L1, the switching off of the transistor Tr 'is delayed for a certain time after the point in time t ", and as a result, the switching-on occurs after the point in time t_. The latter must not occur before the ramp-down time has ended.

It should be evident that a

positive polarity for the flyback oscillation could be used to drive the transistor Tr ¹ . But this measure could have the disadvantage that the peak of the oscillation ^{would be cut off by the base current of the transistor Tr 1} , so that the negative Iblarity is preferred.

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From Pig. 2a shows that the

Time t_, when the current i goes through the value Nxill, generally not in the middle of the linear part of the derm curve shown in this figure. It means that

S the current i has a direct current component. From Fig. 1 it can be seen that this direct current component is nothing more than that of the current i. ¹ and is therefore dependent on the losses of the circuit arrangement and on the energy to be supplied to the respective secondary circuits. The value can therefore be considerable, which can be considered a disadvantage, since it can induce magnetic saturation of the transformer T, although such saturation can be reduced by using a core with an air gap for the transformer T.

The direct current component of the current _i can, however, be reduced by connecting the right-hand end of the choke L 'to a tap on the winding L, the connection of the capacitors C _{1 and Cp facing away from the diode D 1} still being connected to the upper one End of the winding L is connected.

When the right end of the throttle

L 'ummittelbax- connected to the collector of the transistor Tr there is no direct current component at all pass through the winding L. In such a case, however, the voltage across the inductor L 'is greater than in the Trap in Fig. 1 so that its inductance must be higher. It should be evident that the circuit arrangement The embodiment with this direct connection is the same as that in FIG. 5 of DE-OS 23 60 025 is shown, with the main difference that the primary winding L in Fig. 1, the horizontal deflection L of said patent in öiner horizontal deflection scarf replaced. As is known, only a small direct current is allowed through a deflection coil for centering purposes flow, so that Fig. 1 or altered with a tap, as mentioned above, for a horizontal deflection circuit is not suitable. It should also be evident that FIG. 1 is a modification of FIG

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called OS is with the reorganization of the resonance circuit; so that the figures 3> h and 6 of the aforementioned OS can also be 'changed in such a way that they can be used as Speisesclial-

instead of deflection circuits are effective. 5

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Claims (3)

July 20, 1978 PHQ 77.008 PATENT ALTSPRtTECHE ίΐ . Image rendering arrangement _f containing a switched supply voltage circuit for converting a DC input voltage into a DC output voltage, which is almost independent of changes in the input voltage and / or changes in a load excluded at the terminals of the output voltage, with the series connection of the primary winding of a transformer and a controlled switch, which Series circuit is connected to the terminals of the input voltage, and to which primary winding a tuning capacitor is connected in parallel, with furthermore a control circuit for alternately bringing the switch into the conduction or blocking state during operation, the duration of which can be regulated depending on the output voltage and with a secondary winding of the Transformer with a rectifier, which supplies the output voltage, is connected, wherein the image display arrangement furthermore has a horizontal deflection circuit, the feed energy from the switched feed voltage circuit, contains, characterized in that the _{voltage present on a trace capacitor (C 1} ) by means of the controlled switch (Tr) and a first diode (D ₁ ) connected to the switch to the primary winding (l) of the transformer (τ) in such a way is supplied so that the primary winding is traversed by a sawtooth-shaped current with the horizontal frequency, which during a first part of its feed / travel time through the first diode and during the other 909824/08 15 ORlQlNAl INSPECTED July 20, 1978 PHQ 77.0OS the hill run time during which the switch is controlled is conductive, flows through a second diode (d_) and the switch, which second diode leads to the series circuit the switch and the first diode are connected in parallel, ^s with an inductance (L '), which is connected via a third diode (D ") to the resonance circuit formed by the primary winding, the tuning capacitor and the trace capacitor, a current from a terminal of the input voltage (Vp.) during the The conduction time of the switch flows, whereby energy is stored in the inductance, while a current flowing through the inductance and the third diode during the blocking time of the switch compensates for energy losses. 2. Image display arrangement according to Claim 1, characterized by a first series connection of the second (D ₂ ) and the third (D ") diode, which have the same forward direction, and dux-cli a second series connection of the inductance (L '), the primary winding (l) and the collector-emitter path of a Tx-ansistor (Tr), which forms the controlled switch, which is connected to the first series circuit pax "allele, the Pax-all el circuit formed being connected to terminals of the Brigangsgleiclispannungsquelle, the first Diode (D ₁ ) is located between the connection point of the second and third diode and the connection point of the transistor and the primary winding. 3. Image display device according to claim 1 or 2, characterized in that a further secondary winding (L ") of the transformer (τ) is coupled to the control electrode of a further switch (Tr ') in the horizontal deflection circuit for switching the same with the horizontal frequency . H. Image display arrangement according to one of the preceding claims, characterized in that the transformer (τ) between circuit elements, which are connected to the primary winding (l) with direct current are, and circuit elements related to the former Secondary winding (Lp) are connected, a galvanic isolation brings about. 909824/0815