GB1599337A

GB1599337A - Tv receivers

Info

Publication number: GB1599337A
Application number: GB849078A
Authority: GB
Original assignee: Licentia Patent Verwaltungs GmbH; Licentia Oy
Current assignee: Licentia Patent Verwaltungs GmbH; Licentia Oy
Priority date: 1977-03-14
Filing date: 1978-03-03
Publication date: 1981-09-30
Also published as: DE2711020A1

Description

(54) IMPROVEMENTS IN OR RELATING TO TV RECEIVERS (71) We, LICENTIA PATENT VERWALTUNGS-GESELLSCHAFT MIT BESCHRANKTER HAFTUNG, a company organised under the laws of Germany, of Theodor-Stern-kai 1, 6 Frankfurt/ Main 70, Germany do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following state ment: The present invention relates to a television receiver.

According to the invention, there is provided a TV receiver having a remote control receiver, a line output stage, signal producing means arranged to control the line output stage, a protection means for the line output stage, and a power supply arranged to energise the remote control receiver and the protection means independently of the output of the remote control receiver, the protection means being responsive to a switch-on signal produced by the remote control receiver to actuate the signal producing means, and to cause the application of an operating voltage from the power supply means to the line output stage with a predetermined delay relative to the actuation of the signal producing means and being responsive to a fault signal indicative of a fault in the line output stage to cause the withdrawal of the operating voltage from the line output stage without delay relative to the production of the fault signal.

The invention will be explained with reference to the drawing for the example of a television receiver having a mains circuit, with stand-by operation and remote control.

Therein Figure I shows an example of a circuit and Figure 2 shows curves for explaining the operation.

In a TV receiver the problem arises of applying an operating voltage to a stage thereof with a certain delay upon switching on of the apparatus, in order to avoid damage to semi-conductors due to indefinite conditions during the starting process.

This precaution is particularly important in the switching on of the operating voltage for the line output stage in a television receiver. If, after the switching on of the receiver or the switching over from stand-by operation to normal operation, the drive of the line output stage has not yet attained its correct value, and hence the line output stage is driven in an indefinite manner, with the full operating voltage already present, the line output stage transistor may be damaged by these indefinite conditions.

Such a delayed switching on of an operating voltage can be achieved for example with an electronic switch in the form of a transistor which via a time constant member is driven at its base in a conducting sense only after a delay. However, this necessitates an additional expenditure on circuitry.

In the example of the invention, the delaying switching on is performed in the manner described in the following: Figure 1 shows, in the television receiver, a mains circuit 1 fed with the mains voltage, having a separating transformer 2 with the primary winding 3 and the secondary winding 4. The secondary winding 4 supplies, via rectifiers 5, 6, 7, 8 four operating voltages U1, U2, U3 and U4. U1 iS the operating voltage for the line output stage 9, which is controlled by the line oscillator 10 via the driver stage 11. The line output stage 9 feeds the line deflection coils 12 for the picture tube 13. Further, there are provided an ultrasonic remote control receiver 14 having a microphone 15, an electronic switch 16, and a protection means comprising a protective circuit 17 having a relay winding A and a switch 18, a filter member 19 and a threshold value circuit 20.

The operation will be explained with reference to Figure 2. In the switched position illustrated the television receiver operates in stand-by condition. The operating voltage U1 for the line output stage 9 and the operating voltages U2, U3 for the further stages, as for example the video output stage, the vertical deflection, the individual amplifiers and the sound part, are switched off by the relay contacts al, a2, a3.

The operating voltage U4 iS not switched off and keeps the remote control receiver 14 in readiness for reception. In some cases the picture tube 13 is pre-heated from the secondary winding 4 via a further rectifier circuit or from the operating voltage U4, which is always present. The line oscillator 10 likewise does not receive any operating voltage. The driver stage 11 receives the operating voltage U4, but owing to the absence of drive on the line oscillator 10 does not give any current.

At the instant tl the microphone 15 receives an ultrasonic remote control signal 21 for switching the receiver to normal operation. The remote control receiver 14 thereupon generates the control voltage Us, which closes the switch 16. The switch 16 is preferably constructed as a programmable stabilising circuit. The line oscillator 10 is now supplied with the operating voltage U4 and via the driver stage 11 it supplies the control voltage for the line output stage 9.

Due to the action of the filter member 19 the voltage U5 at the output of this filter member rises, but only slowly so that initially the switch 18 in the protective circuit 17 is not closed. Upon the attainment of the threshold value Uw at the instant t2 the threshold value circuit 20 supplies at the terminal 22 the voltage U6 which actuates the switch 18. Thereby the winding A is supplied with current at voltage U4, so that the relay contacts a1, a2, a3 are closed. At the instant t2, therefore, the receiver is fully switched on. It is apparent that the voltages U1 U2, U3 appear with a time delay from t to t2 of about one second. During this time satisfactory driving of the line output stage 9 is ensured, so that the line output stage transistor is not endangered.

The protective circuit 17 has primarily the purpose of switching off the operating voltages Ul. U2, U3 upon the occurrence of a fault in the circuit, by opening the contacts a1 to a3. This is effected by a fault voltage UF at the terminal 23. This is preferably derived from the magnitude of the current through the line output stage transistor or the magnitude of the voltage of the flyback pulse. If this current or voltage exceeds a certain value, the fault voltage UF opens the switch 18, so that the contacts al to a3 are opened. Such a protective circuit is described in more detail in German patent specification 15 91 712. By the control at the terminal 22 by the voltage U6, this ability of the protective circuit 17 is therefore additionally utilised for the delayed switching on of the operating voltage U1 for the line output stage 9.

The relay contacts a here serve merely for switching between stand-by and normal operation. Upon complete switching off of the receiver the mains voltage on the primary side of the separating transformer 2 in the mains circuit 1 is completely switched off.

The described embodiment ensures the delayed switching on of the operating voltage, utilising components which would normally be present in a receiver with little expenditure on extra circuitry.

In the example of the described hereinbefore the ability of a protective circuit present to switch off the operating voltage in an emergency is additionally utilised for switching on the operating voltage with delay after the switching on of the apparatus. Directly after the switching on of the apparatus the protective circuit is therefore in its operative condition as if there were a fault in the apparatus, and initially it keeps the operating voltage switched off in desired manner.

The protective circuit is therefore independently rendered operative in the sense of switching off the operating voltage, on the one hand by the fault voltage arising from the fault and on the other hand by a voltage that occurs upon switching on.

As described hereinbefore, the invention is particularly advantageously used in a television receiver having a mains circuit and with stand-by operation. In the case of such a mains circuit the operating voltages are obtained by rectification of the output voltage on the secondary winding of the separating transformer. The delayed switching on of the operating voltage may then be effected in desired manner on the secondary side of the mains circuit. This has the advantage that no interference with the primary side is necessary and the desired absolute galvanic separation between the primary side and the secondary side of the mains circuit is ensured.

WHAT WE CLAIM IS: 1. A TV receiver having a remote conrol receiver, a line output stage, signal producing means arranged to control the line output stage, a protection means for the line output stage, and a power supply arranged to energise the remote control receiver and the protection means independently of the output of the remote control receiver, the protection means being responsive to a switch-on signal produced by the remote control receiver to actuate the signal producing means, and to cause the application of an operating voltage from the power supply means to the line output stage

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. reference to Figure 2. In the switched position illustrated the television receiver operates in stand-by condition. The operating voltage U1 for the line output stage 9 and the operating voltages U2, U3 for the further stages, as for example the video output stage, the vertical deflection, the individual amplifiers and the sound part, are switched off by the relay contacts al, a2, a3. The operating voltage U4 iS not switched off and keeps the remote control receiver 14 in readiness for reception. In some cases the picture tube 13 is pre-heated from the secondary winding 4 via a further rectifier circuit or from the operating voltage U4, which is always present. The line oscillator 10 likewise does not receive any operating voltage. The driver stage 11 receives the operating voltage U4, but owing to the absence of drive on the line oscillator 10 does not give any current. At the instant tl the microphone 15 receives an ultrasonic remote control signal 21 for switching the receiver to normal operation. The remote control receiver 14 thereupon generates the control voltage Us, which closes the switch 16. The switch 16 is preferably constructed as a programmable stabilising circuit. The line oscillator 10 is now supplied with the operating voltage U4 and via the driver stage 11 it supplies the control voltage for the line output stage 9. Due to the action of the filter member 19 the voltage U5 at the output of this filter member rises, but only slowly so that initially the switch 18 in the protective circuit 17 is not closed. Upon the attainment of the threshold value Uw at the instant t2 the threshold value circuit 20 supplies at the terminal 22 the voltage U6 which actuates the switch 18. Thereby the winding A is supplied with current at voltage U4, so that the relay contacts a1, a2, a3 are closed. At the instant t2, therefore, the receiver is fully switched on. It is apparent that the voltages U1 U2, U3 appear with a time delay from t to t2 of about one second. During this time satisfactory driving of the line output stage 9 is ensured, so that the line output stage transistor is not endangered. The protective circuit 17 has primarily the purpose of switching off the operating voltages Ul. U2, U3 upon the occurrence of a fault in the circuit, by opening the contacts a1 to a3. This is effected by a fault voltage UF at the terminal 23. This is preferably derived from the magnitude of the current through the line output stage transistor or the magnitude of the voltage of the flyback pulse. If this current or voltage exceeds a certain value, the fault voltage UF opens the switch 18, so that the contacts al to a3 are opened. Such a protective circuit is described in more detail in German patent specification 15 91 712. By the control at the terminal 22 by the voltage U6, this ability of the protective circuit 17 is therefore additionally utilised for the delayed switching on of the operating voltage U1 for the line output stage 9. The relay contacts a here serve merely for switching between stand-by and normal operation. Upon complete switching off of the receiver the mains voltage on the primary side of the separating transformer 2 in the mains circuit 1 is completely switched off. The described embodiment ensures the delayed switching on of the operating voltage, utilising components which would normally be present in a receiver with little expenditure on extra circuitry. In the example of the described hereinbefore the ability of a protective circuit present to switch off the operating voltage in an emergency is additionally utilised for switching on the operating voltage with delay after the switching on of the apparatus. Directly after the switching on of the apparatus the protective circuit is therefore in its operative condition as if there were a fault in the apparatus, and initially it keeps the operating voltage switched off in desired manner. The protective circuit is therefore independently rendered operative in the sense of switching off the operating voltage, on the one hand by the fault voltage arising from the fault and on the other hand by a voltage that occurs upon switching on. As described hereinbefore, the invention is particularly advantageously used in a television receiver having a mains circuit and with stand-by operation. In the case of such a mains circuit the operating voltages are obtained by rectification of the output voltage on the secondary winding of the separating transformer. The delayed switching on of the operating voltage may then be effected in desired manner on the secondary side of the mains circuit. This has the advantage that no interference with the primary side is necessary and the desired absolute galvanic separation between the primary side and the secondary side of the mains circuit is ensured. WHAT WE CLAIM IS:

1. A TV receiver having a remote conrol receiver, a line output stage, signal producing means arranged to control the line output stage, a protection means for the line output stage, and a power supply arranged to energise the remote control receiver and the protection means independently of the output of the remote control receiver, the protection means being responsive to a switch-on signal produced by the remote control receiver to actuate the signal producing means, and to cause the application of an operating voltage from the power supply means to the line output stage

with a predetermined delay relative to the actuation of the signal producing means and being responsive to a fault signal indicative of a fault in the line output stage to cause the withdrawal of the operating voltage from the line output stage without delay relative to the production of the fault signal.

2. A receiver according to claim 1, wherein the remote control receiver is an ultrasonic remote control receiver.

3. A receiver according to claim 1 or 2, wherein the signal producing means comprises a line oscillator arranged to be actuated by the protection means.

4. A receiver according to claim 3, wherein the signal producing means further comprises a driver stage, arranged to be energised by the power supply means independently of the output of the remote control receiver and protection means, coupling the line oscillator to the line output stage.

5. A receiver according to any preceding claim, wherein the protection means comprises a delay means, a switching means responsive to the switch-on signal to connect the delay means and the signal producing means to the power supply means, and a protective circuit responsive to the delay means to cause the application of the said operating voltage to the line output stage with the said predetermined delay defined by the delay means from reception by the switching means of the switch-on signal and responsive to the fault signal to cause the withdrawal of the operating voltage from the line output stage without delay relative to production of the fault signal.

6. A receiver according to claim 5, wherein the protective circuit includes a relay having a contact control winding arranged to be energised in dependence on the output of the delay means and on the fault signal. and a relay contact arranged to control the connection of the power supply means to the line output stage in dependence on the energisation of the winding to control the application of the said operating voltage to the line output stage.

7. A receiver according to claim 6, wherein the relay includes a further contact arranged to control the connection of the power supply means to a part of the receiver other than the line output stage in dependence on the energisation of the winding.

8. A receiver according to claim 7.

wherein the power supply means is arranged to produce a further operating voltage for application to the said part, the further contact being arranged to control the apply cation of the further operating voltage to the said part.

9. A receiver according to any preceding claim wherein the power supply means comprises a transformer having a primary winding for connection to a mains circuit, and a secondary winding connected to a rectifier or respective rectifiers to produce the said operating voltage or the respective operating voltages.

10. A TV receiver substantially as hereinbefore described with reference to the accompanying drawings.