SE438399B - CONNECTING TO A LINE END STEP IN A TELEVISION RECEIVER - Google Patents

Description

i 7808441-5 10 15 20 25 30 35 2. the take-up angle becomes as large as possible and thus the feed losses are small. This applies to accumulator or battery-powered devices. In mains-operated devices, this voltage can be produced, for example, by means of a thyristor stabilization step operating with the mains frequency. In this case, however, the disturbing repercussions of the device on the mains become large, because it is difficult to achieve mains separation, which requires a large mains transformer.

Another possibility of achieving the required DC voltage is to use a cutting current source, where the mains voltage is first rectified and then cut off at a high frequency, often with the line frequency, to the primary side of the current source transformer and again rectified on the secondary side. A small format transformer can be used here, since the frequency is high. In addition, mains separation can be achieved through the transformer. The coupler can be either a transistor or a thyristor.

If the coupler consists of a thyristor, a special commutation circuit is required for the current switching, for example a resonant circuit connected between anode and cathode. However, this increases the power losses and, in addition, the stabilization is difficult, since the resonant circuit determines the coupling time of the coupler.

If the coupler consists of a transistor, the current can be interrupted by base control, whereby the regulation of the bottoming time is also easy to perform and thus also the stabilization of the output voltage. The problems consist of the breaking losses, which one strives to reduce by limiting the pitch speed of the switch's collector voltage at the moment of breaking. As a limitation for the rise speed, a diode resistance-capacitor combination connected via the coupler is often used, where the rise of the refraction is slowed down by the series connection of the capacitor and the diode - and the capacitor is discharged through the resistor connected in parallel. In this way, the coupling losses can be transmitted from the inside of the transistor to the outer resistor. However, the actual loss effect arises. It should be mentioned that a thyristor coupler also requires a corresponding limiting circuit for the rise speed of the voltage so that the thyristor is not to be reconnected to the conducting state.

The best known of the circuits which directly supply energy periodically to the deflection circuit is a thyristor line output stage, where a commutation circuit interrupts the current of the deflection circuit, supplies the additional energy required by the deflection circuit and breaks its own current. A disadvantage here is the large currents which occur in the circuits.

For a certain deflection coil, the following values have been given: inductance Lh = 1.7 mH, resistance Rh = 1.8 ohms, current from peak to peak Ihpp = 3.6 A (on coil for a 90 ° 20 "color picture tube).

The effective value of the sawtooth current is Ipp: (2 - Vfš) or in this case 3.6 A: 3.46 = 1.04 A. The power consumed in the resistor is I2 - R = 1.042 - 1.8 = 1.95 W (in in practice, this effect is greater, since the AC resistance is greater than the DC resistance). The pole voltage of the deflection coil required to provide the deflection current is during the deflection a 1 u = xmäzæ1nmnàšå = 11sv, where the sweep time is 52 television (line 64 / us). The current consumed for the losses is 1.95W 118V E _ U = 16.5 mA.

This is an average value stream. If the current is input during the sweep in the saw shape, the peak value T1 .gg 2 EI - 2 52 G3 is 40 mA / us, which is a typical value for color-1 7808441-5 10 15 20 25 30 35 ___..- .. ......____.__.: _...__- _. If the sweep switch is a thyristor, in order to break its current to the anode, a compensating current must be applied, the peak value of which is greater than the value of the deflection current at least during the disconnection line time of the thyristor. In this case, the required current is about 1.3 'I 22 = 2.3 Ä; if the current current is sinusoidal and the required switch-off time is 3.5 / us. If this current is compared with the peak value of 40 mA for the current obtained above, to compensate for the losses, the ratio is 57.

In the thyristor circuit, a compensation or commutation current must be input for the breakage of the sweep switch, which is thus considerably larger than what is needed to compensate for the losses. the excess energy must be returned to the commutation circuit_and this results in the occurrence of a large reciprocating current between the commutation and sweep switch. This current is formed by means of a resonant circuit coupled between the commutation and sweep coupler, where the inductance is either separate or included in the coupling factor of the transformer, as according to U.S. Pat. No. 4,034,263 (H ool J 29/70).

For this inductance, especially in the latter case, a considerable amount of winding wire is required, through which a large current flows. Current constriction, which in a conductor is caused by its own current or by current in adjacent conductors, gives rise to great resistance in the wire, which together with the large current causes a large loss of power.

In addition, an auxiliary circuit is required if it is desired to stabilize the function of the line output stage, for example a transducer or a third thyristor. These elements together cause a high loss effect.

If the commutation thyristor is replaced with a transistor, as according to the published German patent application 2,614,299 (H 04 N 3/16), the situation remains unchanged. Only the stabilization auxiliary circuit can be omitted, since the bottoming time of the transistor can now be regulated. From curve b in Fig. 2 of the application it appears that the collector current is broken from a large value at the time tg, which means a large breaking loss. The power loss is thus still large.

If the sweep switch is a transistor, the break can be performed by base control, the losses only being the break loss of the transistor. This is also large, if the rising speed of the collector voltage is large. However, the sweep circuit consists of a resonant circuit, where the tuning capacitor is connected across the transistor. This capacitor limits the rise speed, so that when using a transistor such as a sweep switch, good efficiency can be achieved, especially if the additional energy is input for as long as possible.

The object of the present invention is to eliminate the above-mentioned problems and disadvantages and to provide a connection for a line output stage, where the breaking losses are particularly small and thus the power consumption is low and where the required additional energy can be input from the power source with good efficiency.

In order to achieve this, the coupling according to the invention is characterized in that the mutual polarity between the primary coil of the feed transformer and the secondary coil is such that as a result of the break of the secondary coupler induces a current, which cancels the current of the primary switch.

In the coupling according to the invention, the primary coupler supplies only as much energy as is needed to maintain the continuous function. By regulating the lead time of the primary switch, it is possible to regulate the energy in question and stabilize the function of the output stage. A further difference in comparison with known couplings arises from the fact that the function of the sweep coupler affects the function of the primary coupler so that the collector current of the primary coupler becomes negative, as will be described in more detail below. No breakage losses occur here, since current and voltage do not occur at the collector at the collector. Thus, the limiting circuit for the rising speed of the voltage also becomes redundant. The invention and its other features and advantages will be described in more detail below in exemplary form and with reference to the accompanying drawing, in which Fig. 1 schematically shows an embodiment of the coupling according to the invention and Fig. 2 shows current and voltage curves, which adhere to the description of the function of the coupling. The primary side of the transformer is formed by windings 1, 2, 3 and 4, and the secondary side by windings 5 and 6 (Fig. 1). The primary side windings are tightly connected to each other, such as the secondary side windings (k.2å 0.95) in a corresponding manner. On the other hand, the coupling from the primary to the secondary side is loose (kéa 0.7). To point A the positive pole of the current source is connected and to point B the negative. An oscillator 7 controls the function of the primary switch formed by a transistor 8 and a diode 9 and an oscillator 10 controls the function of the secondary or sweep switch formed by a transistor 11 and a diode 12. 13 and 14 constitute energy storage capacitors, while a sweep capacitor is denoted by 15. 16 is a deflection coil and a diode 17 rectifies the voltage coming from the winding 6 to a voltage across the capacitor 14, which acts as a driving voltage for the oscillator 10 and via points C and D can be connected as the driving voltage for other circuits.

Use of the loose connection between the primary and secondary coils for energy storage is not necessary in terms of function, but the structure of the circuit is simplified. It is also possible to use a transformer with a hard coupling between the primary and the secondary and a separate inductance, in which the energy is stored, or a coupling which constitutes a compromise thereof.

The function of the connection is as follows: At the moment t1 (fig. 2) the transistor 8 is controlled to conducting in “x 10 15 20 25 30 35 7808441-5 state (base current = curve f). The transistor 11 is in this case in a conducting state and its collector current (curve c), base current (curve a) and collector voltage (curve b) are those shown in Fig. 2. In this case, the capacitor 13 is connected to the socket of the winding 5 via the transistor 11. When the capacitor 13 is large, the leakage inductance between the windings 1 and 5 constitutes the load of the transistor 8 and the collector current of the transistor 8 begins to grow at a rate determined by this leakage inductance and the driving voltage. (curve 3, tï - t3). At the moment t2 the base current of the transistor 11 is broken (curve a), whereby at the collector after the switch-off time (tz - t3) a return pulse arises according to curve b, the length (t3 - t5) of which is determined mainly by the inductance of the deflection coil 16 and the series capacitor 19 capacitance.

During the return time, the load of the coil 5 is constituted by a resonant circuit, whereby the energy stored in the leakage inductance between the windings 1 and 5 is transferred to the resonant circuit while causing polarity change of the collector current of the transistor 8 (curve e, t3 - ts). The base current of the transistor 8 can be interrupted at the time when the polarity of the collector current changes, ie. the current passes from the collector to the diode 9 (curve f, t4).

If the energy transported to the resonant circuit corresponds to the energy consumed in the deflection circuit during the previous period, the function continues unchanged during the following period. The amount of energy that is transferred can be regulated by changing the switching moment of the transistor 8 in relation to the return pulse. The energy level can be measured by measuring the amplitude of the return pulse, for example differentially through the windings 3 and 4.

During the time t5 - ts, the situation on the secondary side is the same as at the initial moment, so the current of the winding 1 changes at a speed determined by the leakage inductance and the driving voltage. Since in the output situation the current is now negative and flows through the diode 9, it follows that the current is interrupted,. 7808441-5 10 ß and the voltage at the cathode of the diode 9 and the collector of the transistor 8 (curve d) becomes positive. The maximum value of this voltage can be limited by the winding 2 and the diode 18.

Since the transformer has a loose connection between the primary and secondary side, it can be combined with the high-voltage transformer required in the television receiver so that the secondary windings are below the high-voltage winding on one leg and the primary windings on the other leg. In this case, the primary and secondary can be easily isolated from each other and no separate mains transformer or transformer is needed for a shear power source to achieve mains separation. Since information can also be fed via the transformer from the secondary back to the primary, the amplitude of the deflection can be kept constant independent of the mains voltage and, for example, of the variations of the high voltage load.

Claims (3)

10 15 20 25 7aoa441-5 ”in Patent Claims Coupling at a line output stage in a television receiver for developing a sawtooth current, consisting of a sweeping and a return part, through a deflection coil (16), which coupling comprises a supply transformer with primary and secondary coils (1, 5), a primary coupler (8, 9) for connecting the primary coil (1) of the supply transformer to a current source (A, B) and a bidirectional secondary coupler (11, 12) for connecting the deflection coil (16) during sweeping to a sweeping capacitor (15) , which absorbs the sweep voltage and for connecting an energy storage capacitor (13) to the secondary coil (5) of the supply transformer, characterized in that the mutual polarity between the primary coil (1) and secondary coil (5) of the supply transformer is such that the break of the secondary switch (11) and the return pulse acting on the terminals of the secondary coil (5) of the supply transformer through the supply transformer to the primary coil (1) induces a current which cancels primary coupler (8.9) Power Coupling according to Claim 1, characterized in that the coupling between the primary coil (1) and the secondary coil (5) of the supply transformer is loose. Coupling according to Claims 1 and 2, characterized in that the additional energy required for deflection is stored in the leakage inductance by means of the primary coupler (8) through the loose coupling between the primary coil (1) and the secondary coil (5) of the supply transformer.