SE455560B - TELEVISION PRESENTATION SYSTEM - Google Patents

Description

455 56Û 2 of the sweep switch in that the single conversion system energy source starts self-oscillating at approximately the horizontal deflection frequency with a working ratio ratio which is almost the ratio between the sweep and sweep regression intervals. During standby, the energy of the remote control circuit flows through the short-circuited sweep switch from a secondary winding of the sweep return transformer. The standby power consumption can amount to less than 10 watts, and a normal value is about 6 watts. The useful power for the remote control circuit can amount to about 1.5 watts at 12 volts.

The invention will be described in detail in the following with reference to the accompanying drawings, in which Fig. 1 shows an energy supply and deflection circuit intended for a television receiver with emergency remote control circuits which form an embodiment of the invention, Fig. 2 shows waves associated with the circuit a Fig. 1 shows the normal operating mode, Fig. 3 shows waves associated with the circuit of Fig. 1 during operation in standby mode, and Fig. 4 shows a detailed embodiment of the output circuit of a single conversion system energy source (SICOS energy source).

In Fig. 1, a single conversion system energy source 20 described in the above-mentioned published British application operates in such a way that it transfers energy from a terminal for an unregulated B + supply to different television receiver load circuits connected to the secondary windings of a sweep return transformer high voltage transformer T1. 33 which is connected to a high voltage winding WQ. During operation 1 of the normal mode of operation, horizontal sweep return pulses are connected in a transformer, see the voltage V3 shown in Fig. 2c, which is formed by the horizontal deflection generator 21, from the secondary winding W2 of the sweep return transformer T1 to the primary winding W1.

From the terminal of the primary winding W1, the positive sweeper pulse pulses are peak-rectified by a diode D1, and they are filtered by a capacitor C1 and fed to the single-conversion system energy source control circuit 22 along a signal line 34. The controller control circuit 22 is synchronized with the horizontal signal line 29 for generating pulse width modulated signals 23 with a working ratio that varies with variations in the amplitude of the sweep return pulse voltage. The pulse width modulated signals are applied to an input terminal 24 of the single conversion system energy source 20 for pulse width modulation of the receiver switches S1 and S2. Each switch comprises a transistor, Tr1 or Tr2, with an antiparallel diode, not shown in Fig. 1, connected between its collector and emitter electrodes. By modulating the pulse width of the operation of the switches S1 and S2, the amplitude of the sweep return pulse is kept relatively constant under varying load and B + voltage conditions.

The positive voltage formed across the capacitor C1 keeps a transistor Q1 in saturation, thereby bringing its collector voltage to the potential of ground 25 and biasing in the reverse direction to a diode D10. On the secondary side of the sweep return transformer T1, a standby switching transistor, namely the darlington transistor Q2, is kept saturated by means of base current flowing from a holding rail 26 through a resistor R9 and a zener diode D5. The horizontal sweep return switch 27 and the horizontal drive transistor Q5 are thus connected to chassis ground 28 via the current conducting remote control switch Q2.

The waveforms in Figs. 2a-2e show the normal operation of the single-conversion system energy source and the horizontal deflection circuit of Fig. 1. Fig. 2a illustrates the switching voltage V1 at the connection point between the output switches S1 and S2 in the single-conversion system energy source. . The solid waves represent waves taken at a typical operating point of the energy source.

Fig. 4 shows a detailed embodiment of the circuit in the single-conversion system energy source 20 in Fig. 1. The switch S1 becomes current-conducting at a controllable moment Tu within the sweep interval of the horizontal deflection cycle, thereby connecting the energy storage coil L1 to the B + input voltage terminal. The switch S1 becomes current-conducting because near the time T1, the positively directed edges of the pulse width modulated signal 23 have turned on the transistor Trä, whereby the transistor Tr2 of the switch S2 has been switched off. In order for the current il to be maintained in the main winding L1 of the coil L1, the terminal provided with a point at L1a becomes positive in relation to the terminal which has no point, whereby the switch S1 diode DS1 has a bias voltage in the forward direction. A now decreasing current in the winding Lla flows to the B + terminal in Fig. 1.

The positive voltage at the one-point terminal of the winding L1a induces a positive voltage at the one-point terminal of the control winding L1c so that the base-emitter junction of the transistor Tr1 is biased in the forward direction. The transistor Tr1 455 560 p 4 picks up the current line in the winding L1a when the current il in Fig. 2b becomes positive at a certain moment after the time TÄ but within the sweep interval T2-T6.

At the end of the sweep interval, at time T6, a controllable amount of energy has been stored in the coil L1. Much of this stored energy is then transferred to the load circuits connected to the sweep regression transformer T1 during the horizontal sweep regression interval T6-T7.

At time T6, the positive sweep return pulse voltage formed at the one-point terminal of the winding W1 in the sweep return transformer T1 is applied to the non-point terminal of the coil L1 winding L1a, whereby the terminals lacking the point and the windings L1 and the winding become positive. The Transistor Trä becomes a current conductor and thereby switches off the transistor Trl. The positive current il is now picked up by the diode DS2 of the switch S2 until close to the center of the sweep return when the transistor Tr2 takes over the current line when the current il becomes negative. During the sweep regression, a resonant transfer of energy takes place via the sweep return transformer T1 between the coil L1 and the sweep regression resonant circuit formed by the capacitor CR and the horizontal deflection winding LH together with the load T1 of the sweep regression transformers W1 connected to the sweep return transformers W1.

Fig. 2d illustrates the base current 13 flowing in the horizontal output transistor Q4 from a winding wb of a horizontal drive transformer T2. Fig. 2e shows the current 12 flowing in a winding wc of the drive transformer T2. Near the time T0, a horizontal drive transistor Q5 is turned on, which thereby generates a base current 15 in the reverse direction, which base current blocks the horizontal output transformer Q4 at the time T1. At the beginning near the time To, a current 12 is also generated which charges a capacitor C8 through a diode D2.

The currents iz and i are thus generated during the normal operation of the switching action of the horizontal drive transistor Q5.

To switch the television receiver to the standby mode of operation, a remote control circuit 30 applies chassis ground potential with a duration of about 1 second as an off-command signal to the base of the remote control switching transistor Q2 via a control rail B1.

When the transistor Q2 is turned off, the current 1 of the sweep return transformer T1 winding W2 is forced to flow to chassis ground 28 via the winding WC of the horizontal drive transformer T2. When the conventional current 455 560 J flows out of the dotted terminal of the sweep return transformer winding W2, the return current path of said current passes through the horizontal output transistor Q4 into the dotted terminal of the drive transformer T2 so that the winding wc C8 is charged to a positive voltage. When the conventional current ii flows out of the terminal of the pointless sweep return transformer winding W2, the return path passes through the diode of the darlington transistor Q2, the attenuation diode D7 of the sweep switch 27 and the diode output transistor Q4 formed by the base collector junction.

The positive current i2 induces in the winding Wb of the horizontal drive transformer T2 a positive base current 13 for the horizontal output transistor Q4. The current ia keeps the horizontal output transistor Q4 conducting. The transformer T2 thus serves as a strap transformer which provides positive feedback from the output of the transistor Q4 so that the transistor is kept saturated.

During standby, transistor Q4 is either in a state with saturated current conduction in the forward direction or a state with collector current conduction in the reverse direction, the attenuation diode D7 also conducting current. These conditions in fact give rise to a short-circuited sweep switch 27 which connects the one-point terminal of the sweep return transformer winding W2 to the one-point terminal of the drive transformer winding WC. With the sweep switch 27 continuously short-circuited, the sweep return resonant circuit is prevented from forming, whereby the sweep return pulse voltages collapse. The supply currents through diodes D4 and D6 become zero, which also applies to the supply voltage vb and the current through the holding rail 26. The remote control transistor Q2 thus remains blocked, even after the above-mentioned off-order signal interval of one second has elapsed.

The voltage Va across the capacitor C4 is the source voltage for the 12 volt supply bus, which activates the remote control circuit 50 and the horizontal oscillator 32. This voltage is formed in the standby mode of operation via diodes D2 and Dj from the positive current in the current i1 flowing in the current transformer. 12. The horizontal oscillator 32 is in operation on standby to facilitate the switching on of the television receiver in the manner which will be described below. A darlington transistor Q3 serves as a shunt regulator to limit the voltage across capacitor C8.

As the sweep return pulses collapse when the standby mode has been initiated, the single conversion system energy source 20 begins to operate in a self-oscillating mode. The collapse of the sweeper pulse pulses disconnects the control circuit 22 and causes the transistor Q1 to turn off. When the transistor Q1 is blocked, an RC network is included which comprises resistors R1-H4 and a capacitor C2 which thereby forms an unstable multivibrator arrangement with the switches S1 and S2 of the single-conversion system energy source. The scales in Fig. 3 illustrate waveforms associated with the circuit of Fig. 1 in the standby mode of operation. As indicated in the voltage V1 in Fig. Ba, the switch S1 in the single-conversion system energy source 20 is current-conducting after the time t1. Near the time t1, the left plate of the capacitor C2 is also positive in relation to the right plate. Thus, when the switch S1 becomes conductive, the capacitor C2 begins to be discharged through the resistors R2 and R3 in the manner indicated in Fig. Jb as a result of the decreasing voltage V2 at the collector of the transistor Q1 after the time t1. the switch S1 in the single-conversion system energy source 20 remains current-conducting due to the regenerative effect produced by the control windings L1b and L1c in Fig. E. As shown in Fig. 1a, the switch S1 remains current-conducting until the time tj, at which time the transistor S1 starts in the switch turned off. When the time t4 has been passed, the transistor Tr1 is turned off while the switch S2 has been switched on as a result of a current line in the diode DS2, whereby the voltage V1 is brought to ground potential.

When the time tu has been reached, the capacitor C2 has been charged to a voltage of opposite polarity, so that the right plate of the capacitor is positive in relation to the left plate. With the positive, right plate of the capacitor C2 locked to ground by means of the switch S2, the base-collector junction of the transistor Q1 is biased in the forward direction, locking the voltage V2 at immediately below ground potential between the times t¿ and t6 in Fig. Jb.

Between the times tu and t6, the capacitor C2 is discharged through the base-collector junction of the transistor Q1 and through the resistor R2 from the B + terminal. Near the instant t6, the voltage across the capacitor C2 reverses its polarity, thereby biasing the base-collector junction of the transistor Q1 in the reverse direction. The capacitor C2 starts to charge from the B + terminal, whereby the left plate of the capacitor is positively charged in relation to the right plate.

When the time t7 according to Fig. 3b has been reached, the capacitor C2 has been charged sufficiently to give the diode D10 bias voltage in the forward direction or to turn on the control transistor Trä in the single-conversion system energy source 20. When the control transistor Tr4 is turned on, the output switch Tr2 will be switched off. When the transistor Tr2 is turned off, the diode DS1 in the switch S1 will be turned on, taking up current line from the main winding L1a of the coil L1 in Fig. 4. The voltage V1 therefore increases to the B + voltage level as illustrated in Fig. 1a.

The duration of a complete self-oscillation of the switches S1 and S2 is, for example, 70 microseconds, which is a duration which is close to the horizontal deflection duration TH_ = 64 microseconds. The self-oscillation time of 70 microseconds is so chosen that it should be short enough to be inaudible to most people in standby mode. The self-oscillation time can be adjusted by adjusting the resistance value of the resistor R2 of the unstable multivibrator.

Fig. Bo illustrates the current il 1 of the sweep return transformer T1 winding wl during standby operation. Since the windings w1 and w2 are fixedly connected to each other and have approximately the same number of winding turns, the current l1 to the collector 1 of the horizontal output transistor Q4 in standby operation is approximately the same shape and amplitude as the current il. In comparison with the currents il and ií during the normal operating mode, the currents il and ií are reduced to a significant degree during the emergency response mode. The power consumption of the single-conversion system energy source 20 during standby is therefore relatively low, for example 6 watts.

Fig. Bd illustrates the voltage V4 across the remote control switching latch Qa in the standby mode. Between the time to een ten-point ta, which is an interval when the currents in the windings W1 and W2 of the sweep return transformer T1 are negative, the diode of the darlington transistor Q2 has bias voltage in the forward direction, the voltage V4 being locked at chassis ground potential. Between the time ta and the time tj, the currents il and ií are positive, with their curves having slopes upwards. During this interval, the current 12 in the winding WC of the transformer T2 is positive, whereby it gives the diode D2 bias voltage in the forward direction and charges the capacitor C8 to a voltage of about 20 volts. In this interval, the voltage V4 is positive and locked at the voltage level established by the voltages that are being generated across the windings WC of the drive transformer T2 and across the capacitor C8.

Near the time tj, the switch S2 in the single-conversion system energy source 20 becomes current-conducting, the negatively directed part of the currents i1 and i1 being initiated. After this time, the current I1 flowing to the winding w2 of the drive transformer T2 causes a reversal in the polarity of the voltage generated across the winding wc. The voltage V4 therefore decreases from the time tö to the time ts, ie the zero crossing moment for the current ií. At time t5, the current becomes negative, giving the diode of the darlington transistor Q2 a bias voltage in the forward direction and again locks the voltage V4 at chassis ground potential.

Since the sweep switch 27 forms a short circuit during the standby operation, the voltage generated across the winding transformer W2 winding W2 becomes the same voltage V4 as illustrated in Fig. 3d but at a different AC zero voltage reference level.

During standby operation, the peak-to-peak voltage across the winding W2 will thus be, for example, about 25 volts in comparison with, for example, 900 volts during the normal operating mode, which means a peak-to-peak voltage reduction to about 3% of the peak-to-peak voltage. the peak voltage obtained during normal operation.

Current conduction in the horizontal drive transformer Q5 is prevented due to the fact that either diode D8 or diode D9 has a bias voltage in the reverse direction. The operation of the horizontal oscillator 32 during the standby mode of operation will therefore not interfere with the self-oscillating mode of operation of the single conversion system energy source20.

. The standby energy from the remote control circuit 30 and the horizontal oscillator 32 is obtained from the winding Wc of the horizontal drive transformer T2 via the current 12 which charges the capacitor C8 and the capacitor C4 during standby operation. The average value of the positive part of the current 12 is shown in Fig. Ef and amounts to about 150 milliamps, which means about 1.8 watts of usable power at the output of the regulator of 12 volts. The positive current 13 illustrated in Fig. 1 in the winding Wb of the transformer T2 is induced by the current 12. The current i has a larger amplitude because the winding Wb has only about half the number of winding turns against the winding WC. For example, the inductance of the winding Wb may amount to about 200 microhenry, and thus the inductance of the winding WC may amount to about 800 microhenry.

The resistors H7 and R8 have the task of smoothing the base current 13. Via the resistor R7 a certain energy is stored in the winding toilet to extend the base current when the diode D2 blocks. The horizontal output transformer Q4 is safely kept saturated until the current through t 455 550 \ O its collector is zero. .

To return the television receiver to normal operation, the remote control circuit 30 applies a positive pulse, which is a command signal, to the base of the switching transistor Q2 via the control rail 31 for about 1 second until a sufficient holding current for the transistor later becomes available from the holding rail 26. The deflection generator 21 , including the sweep switch 27, is reconnected to chassis ground 28 directly through the switching transistor Q2, whereby the emitter of the horizontal output transistor Q4 has ground potential. As a result, the current i1 in the sweep return transformer winding W2 is grounded to ground by transistor Q2 away from the winding WC of the drive transformer T2. As a result, the current 12 decreases greatly, and the horizontal output transistor Q4 is not in a continuous saturated current line.

The operation of the single conversion system energy source 20 is changed to a start-up sequence which is similar to the start-up sequence described in the above-mentioned published British application for an invention made by P. Haferl. This sequence is controlled by the sweep return self-oscillation until the sweep return voltage coupled to the sweep return transformer T1's primary winding W1 has a sufficiently large amplitude to reactivate the single conversion system energy source regulator control circuit 22. At the same time, the sweep return pulse voltage causes the transistor Q1 to saturate, whereby the multivibrator network comprising the resistors R1-R4 and the capacitor C2 is switched off. During the transition from standby to operating mode, the current 1 changes from being induced by the current in the winding Wc of the drive transformer T2 to being induced by the current in the winding wa. Similarly, during the transition from operation to standby, the current 13 changes from being induced by the winding wa to being induced by the winding WC. In order for these transitions to be performed safely without damaging the horizontal output transistor Q4, the switching sequence of the transistor Q4 during the transitions is not interrupted. Transistor Q4 is not turned on when a large positive voltage V3 is present at the transistor collector.

In standby operation, the horizontal oscillator 52 operates, but it is only connected in a circuit with the base of the horizontal drive transistor Q5 when the voltage V4 is low. When the voltage V4 is low, the current ii flows in the negative direction from the diode of the darlington transistor Q2. Thus, even if switching signals are supplied to the base of the drive transistor Q5 in standby mode, only a small negative current will flow, and this does not interfere with the operation of the transistor Q4.

When the current ií becomes positive, the voltage V4 becomes high. The power line in the collector of the transistor Q5 is broken by the diodes DB and D9. A positive current 13 flows so that transistor Q4 is kept under bias voltage until saturation.

When the television receiver is switched from standby to operating mode, transistor Q2 is switched to saturation. Immediately after the command signal has been received, the voltage V is at zero volts, and this results in the zero current in driving the horizontal output transistor Q4. The single-conversion system energy circuit 20 continues to self-oscillate as in standby. The sweep return circuit LH, CR self-oscillates so as to obtain a voltage V3 with increasing amplitude at the sweep return frequency during the interval tl-tj in Fig. 3.

The automatic frequency and phase control part of the horizontal oscillator 32, which part is not de-energized in Fig. 1, begins to phase in the oscillator output to the phase of the self-oscillating voltage V3. The self-oscillating voltage with increasing amplitude which is formed across the sweep return capacitor CR is connected via the sweep return transformer winding W1 and the coil L1 control winding Llc to the base of the transistor Trj for switching on said transistor, whereby the transistor turns off Tr1. The self-weighing voltage V3 with increasing amplitude therefore begins to synchronize the switching off of the switch S1 to the phase of the output of the horizontal output oscillator 32.

As the voltage Vb increases, the oscillator 52, which already has the correct phase, controls the switching of the horizontal drive transistor QS so that the base current 13 with the correct phase is supplied to the horizontal output transistor Q4. The self-oscillating voltage with increasing amplitude switches on the transistor Q1 and thereby switches off the multivibrator arrangement with the transistors R1-R4 and the capacitor C2, at the same time as it activates the regulator control circuit 22. Once the regulator control circuit 22 has been activated, the voltage V3 increases evenly to its nominal value. .

When the television receiver is switched from operating mode to standby, the conversion is a controlled conversion, whereby the horizontal output transistor Q4 is safely brought to a saturated current line on a continuous basis. When the off-order signal is received, the remote control transistor Q2 is switched off, whereby the operation of the horizontal drive transistor Q5 ceases. If the transistor Q2 happens to be turned off during the sweep return, the current induced in the winding Wb of the drive transformer T2 by the winding wa becomes larger than the current induced by the winding Wo. The horizontal output transistor Q4 remains blocked until the end of the sweep return. Thereafter, transistor Q4 is kept continuously saturated.

For a few milliseconds immediately after the off-signal is received, the single-conversion system energy source 20 operates at the lower self-oscillation frequency described in the aforementioned published British patent application with P. Haferl as inventor. When the capacitor C1 in Fig. 1 has been discharged to a sufficient extent to turn off the transistor Q1, the multivibrator arrangement comprising the resistors R1-R4 and the capacitor C2 is activated, this arrangement increasing the operating frequency of the single-conversion system energy source switches S1 and S2 to a self-oscillating frequency as discussed above.

The emergency circuit arrangement just described according to Fig. 1 also provides protection against short circuit and overload. The switching transistor Q2 is controlled only by on-from-order pulses originating from the remote control circuit 30. When the transistor is turned on, it is kept in saturation by the base current supplied from the holding rail 26. A short circuit or an overload which results in a reduction in the voltage Vb to a voltage below about 6.5 volts means that the remote control switching transistor Q2 is switched off and that the television receiver and the single-conversion system energy source 20 are set to the standby mode of operation.In the standby mode, the voltage Vb decreases completely with the current. The television receiver thus generally returns to the emergency mode of operation during a condition when an overload remains, even if repeated attempts are made to connect the television receiver.

An example of the horizontal drive transformer T2 is given as follows: Core: cylindrical, 50 x 6 mm, material N27; wa = 350 turns of 0.2 mm, 4 mH diameter wire; Wb: 80 winding turns wire wire with a diameter of 0.4 mm, 200p fl h WC: 160 winding turns wire wire with a diameter of 0.2 mm, 800flfl í.

Claims (1)

A television presentation system operable depending on the state of an on-off command signal, the system comprising a deflection winding, a deflection generator including a sweep switch arranged to generate a deflection current in said deflection wind, a deflection wind and a deflection current. a switching type energy source synchronized with deflection by operating said deflection generator under normal operation to produce energy for said television presentation system, characteristic WC, WC) which are connected to said deflection generator (21) and which are of means (Q2, W operable in response to said on-off command signal to provide continuous current conduction of said sweep switch (QR) upon receipt of the off state of said order signal to thereby change the operation of said energy source (20) of switching type to a standby mode. drawn therefrom, that said energy source (20) of Television presentation system according to claim 1, sensing type in the standby mode of operation self-oscillates while producing energy at a greatly reduced energy level. 3. characterized in that said deflection generator (20) including Television presentation system according to claim 2, k ätn down - a sweep return resonant circuit (CR, LH) for generating a sweep return pulse voltage and that said switching type energy source (20) includes an inductance (H1) coupled to said sweep return resonant circuit (CR, LH) for transmitting energy therebetween. Illustrated in that said energy source (20) of switching television presentation system according to claim 3, sensing type includes a voltage source (B +), output switching means (S1, S2) connected to said source (E +) and to said inductance (H1) and a control circuit (22) for effecting synchronized operation of said output switching means during normal operation, said control circuit (22) being actuatable in response to the absence of said sweep return voltage and being arranged to effect self-oscillation at such actuation. said output switching means (S1, S2). A television display system according to claim 1 including an input voltage source, said switching type energy source being connected to said source, characterized by a power transformer (T1) having a first winding (W1) connected to said deflection generator (21) for transferring energy from said source to said deflection generator during normal operation and a standby energy source (We, D2, C8) to provide a working supply voltage during standby operation, energy flowing to said standby energy source through a short circuit path formed by said means are influenced by an on-from-order signal. A television presentation system according to claim 5, characterized by - t e c k n a t thereof; said switching type energy source includes control circuits which, when the order signal is in the off state, cause self-oscillating operation of said switching type energy source to generate a voltage of alternating polarity across said power transformer second winding (W2), energy flowing through said second winding said short-circuit path. Television display system according to claim 6, characterized in that said means operable in response to said on-off command signal include a controllable switch (Q2) in parallel with said standby power source (We, D2, C8) for shunting. energy away from said emergency energy source during normal operation. Television display system according to claim 6, characterized in that said switching type energy source (20) includes an inductance (L1) arranged to store energy therefrom from said input voltage source (B +), a sweep return pulse voltage being generated of said deflection generator, said inductance is applied during normal operation to transmit energy stored in said inductance. Television display system according to claims 1, 5 or 8, characterized in that said switching type energy source includes output switching means (Tr1, Tr2) connected to said input voltage source (B +), a reactive network (R1, R2, R3, RA, C2) coupled to said output switching means and means (Q1) which are actuatable in response to a signal indicating the absence of sweep return pulse generation to activate said reactive network for generating said self-oscillating mode. Television display system according to claim 9, characterized in that the control circuit (22) for said switching type energy source is operable in response to a deflection rate signal (29) during normal operation to cause said switching type energy source to work in synchronism with the generation of scanning current and that said reactive network (R1, R2, R3, RU, C2) during the standby operation generates self-oscillating operation at a frequency close to the deflection frequency. Television presentation system according to claim 5, characterized in that said means operable in response to said on-off order signal include a second transformer (T2) with a first winding (Wb) connected to a Må control terminal of said sweep switch and a second winding ar? (We) connected to an output terminal of said sweep switch ïwy and connected to said standby power source to provide a positive feedback to maintain continuous current conduction of said sweep switch. A television display system according to claim 11, characterized in that said means operable in response to said on-off command signal include a controllable switch (Q2) coupled to said scan switch (QU). to shunt current away from said second winding (Wo) of said second transformer (T2) during normal operation. Television display system according to claim 11 or 12, characterized by a deflection oscillator (32) connected to a third winding (Ha) of said second transformer (T2) to provide the deflection rate switching of said sweep switch (Q4) during normal operation.