US3739094A

US3739094A - Gaseous light firing circuit for television receivers

Info

Publication number: US3739094A
Application number: US00178770A
Authority: US
Inventors: D Griffey
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 1971-09-08
Filing date: 1971-09-08
Publication date: 1973-06-12
Anticipated expiration: 1990-06-12
Also published as: CA945689A

Abstract

A gas discharge lighting device useful as a pilot light in a television receiver has for its primary voltage supply a steady state voltage input means greater than the sustaining voltage potential required for operating the lighting device but less than the firing voltage potential required for consistently and continuously firing the lighting device into operation. In order to assure firing the lighting device without altering the voltage level of the steady state voltage input means, a pulsating voltage input means having recurring voltage pulses of relatively short duty cycle are applied to the lighting device so as to be additive with said steady state voltage potential.

Description

United States Patent 1 Griffey June 12 1973 [75] Inventor: Donald E. Griffey, Skokie, Ill. [73] Assignee: Motorola, Inc., Franklin Park, Ill. [57] ABSTRACT [22} Filed: Sept 8, 1971 A gas discharge lighting devi ce useful as a pilot light in y l a television receiver has for its primary voltage supply PP NW a steady state voltage input means greater than the sustaining voltage potential required for voperating the 521 US. Cl 178/73 R i device less than the Rage PP required for consistently and continuously firing the [51.] Int.,Cl. H041: /44 [58] Field of Search 340/253 P, 253 A, l ".Peratim assure 340/286, 253 C, 226, 331, 248; 78/73 7.84 the lighting device without altering the voltage level of the steady state voltage mput means, a pulsating volt- 56] v References cued age input means having recurring voltage pulses of relatively short duty cycle are applied to the lighting device UNITED STATES PATENTS so as to be additive with said steady state voltage poten- 3,339,019 8/1967 Kn0rr,-.lr. et a]. 178/73 R ti L 2,084,995 6/1937 Barbulesco 340/253 P 4 Claims, 2 Drawing Figures 25 2/ H Q CRT 2/0 8 27 ,3 if I r'iZoEo R 5 AMP AMP 48 VHF B TUNER 23 FOCUS SWITCH 47 45 PL PL UHF VHF TUNER 43 TUNER GASEOUS LIGHT FIRING CIRCUIT FOR TELEVISION RECEIVERS Primary Examiner-Richard Murray Att0rneyVincent Rauner and L. Arnold AAA GASEOUS LIGHT FIRING CIRCUIT FOR TELEVISION RECEIVERS BACKGROUND This invention relates to firing circuits for gaseous lighting devices and more particularly, relates to a gaseous light firing circuit for a pilot light in a television receiver.

A gaseous or gas discharge lighting device requires the application of a firing or starting voltage input potential for initiating its operation and the continuous application thereafter of a sustaining or holding voltage input potential of a lower amplitude to maintain operation of the lighting device. In television receivers, such gaseous lighting devices are used to provide dial illumination and pilot lights and are often connected to a steady state voltage supply which simultaneously serves as a voltage supply for other parts of the receiver including voltage sensitive solid state components such as semiconductor devices. In a practical design of the television receiver wherein factors of economy and peak performance are balanced, the solid state components have operating parameters which correspond to the amplitude of their voltage supply; therefore, the break down voltages of these solid state components may be exceeded if the voltage supply is significantly increased for other purposes such as firing a gaseous light. The use of a different steady state voltage supply of a greater amplitude for firing the gaseous light comprises a cost disadvantage. Also, due to some variation in firing levels for a variety of gaseous lights, it becomes desirable to exceed the firing voltage level by some safety margin to assure consistent and continuous firing of the lights. This again increases the probability of exceeding the breakdown voltages of the solid state components through raising the voltage level of the steady state voltage supply common to both the light and the solid state components. It is therefore proposed to supply a gaseous lighting device with a series of recurring voltage pulses of relatively short duty cycle and which are additive with the steady state voltage input supply connected to the lights. These voltage pulses make it possible to assure proper firing of the light and to do so without appreciably increasing the power consumption of the lighting device.

SUMMARY It is therefore an object of this invention to provide a circuit for firing a gaseous lighting device for a television receiver by selectively increasing the absolute voltage potential applied across the lighting device.

It is another object of the invention to provide a series of recurring voltage pulses to the lighting device in a manner so as to be additive with the normal voltage potential applied across the lighting device.

A television receiver having voltage sensitive solid state components includes a circuit for firing the gaseous lighting devices useful as dial illumination and pilot lights for the receiver. An individual gas lighting device has a pair of electrical terminal means and requires an input sustaining voltage potential across the pair of terminal means for sustaining operation of the light and an input firing voltage potential across the terminal means greater than said sustaining voltage potential for beginning operation of the light. The firing circuit includes a steady state voltage input means which has a voltage amplitude in the range between the sustaining and the firing voltage potentials of the light and is connected to one of the pair of terminal means of the light. A pulsating voltage input means comprises a series of recurring voltage pulses and is connected to the other of the terminal means of the light. .These voltage pulses are additive with the steady state voltage input means for increasing the total voltage potential across the light to a voltage amplitude greater than the firing voltage potential for beginning operation of the light. This increased voltage potential is selectively applied across the light while maintaining the amplitude of the steady state voltage means.

THE DRAWING FIG. 1 is a circuit diagram partly in block form and partly in schematic form of a television receiver incorporating the gaseous light firing circuit in accordance with the present invention;

FIG. 2 is a graphical representation of a series of recurring voltage pulses applied to a gaseous lighting device through the use of the firing circuit of FIG. 1.

DETAILED DESCRIPTION Television receivers include many solid state components biased into operation by a steady state voltage supply within the receiver, which supply has been selected to correspond to the operating characteristics of the solid state components. The receivers also utilize dial illumination and pilot lights of the gaseous or gas discharge type which are operated from the steady state voltage supply common to the solid state components. These gaseous lights require a greater voltage potential to fire the light into operation than to hold or sustain its operation. In order to assure the firing of an individual gaseous light by increasing its applied voltage potential and yet to avoid exceeding the breakdown voltages of the solid state components, it is required to selectively apply an additive voltage potential across the gaseous light while maintaining constant the amplitude of the steady state voltage supply.

In a preferred embodiment of the present invention as shown in FIG. 1, a television receiver circuit 10 has television receiving and processing circuitry typically comprising an antenna 11, a tuner section 13, an intermediate frequency IF amplifier section 15, and video driving stages including a first video amplifier l7 and a video output transistor 19. The processed television signals supplied from the collector of the video output transistor 19 are then used to drive a cathode-ray tube 21 for displaying the processed signals as images on a display screen 21a. The video output transistor 19 is biased for conduction by a biasing network comprising an emitter resistor 23 and a collector resistor 25 and has a steady state voltage supply or input means 27 also indicated at B+ in the drawing.

The receiver circuit 10 further typically includes circuitry for deriving vertical and horizontal synchronization signals from received composite video signals for use in vertical and horizontal deflection systems associated with controlling the direction of electron beam bombardment within the cathode-ray tube 21. The vertical deflection system is shown in FIG. 1 in connection with its use in comprising a part of the firing circuit of the present invention as will be explained hereinafter. The vertical deflection system includes a vertical oscillator and driver section 31 which receives synchronization signals from the IF amplifier 15 and feeds a vertical output section 33 including a vertical output transistor 35 supplying as its load a vertical deflection yoke 37 through a coupling capacitor 34.

The vertical output transistor 35 also supplies a coil 39 used as the supply coilfor the B+ steady state voltage supply 27. The vertical output transistor 35 is illustrated to be a PNP-type transistor having an emitter resistor 38 connected to ground. The cathode-ray tube 21 includes a focus network indicated in the drawing as G, B and R for symbolizing the focus control for the green, blue and red electron guns of a standard triplegun color picture tube.

FIG. 1 further shows a pair of gaseous lighting devices 41 and 43 in the form of two pilots connected in electrical parallel and used for lighting the dial faces of VHF and UHF tuners (not shown) for the TV receiver, respectively. The lights 41 and 43 are connected in electrical series with a pair of current limiting

resistors

45 and 47, respectively, and are connected across the steady state voltage supply 27. A switch 46 on the VHF tuner is connected in series with the UHF pilot light 43 and functions to disconnect the UHF pilot light when the switch 46 is in the VHF tuner position at terminal 48. The pilot lights 41 and 43 are connected to ground through a common resistor 49.

FIG. 2 shows a voltage versus time curve 53 serving as a graphical representation of a series of recurring voltage pulses 53 in the form of relatively large negative going spikes. The vertical deflection yoke 37 is the source of the voltage pulses 53 which have a time duration between pulses of t, and a time duration of t for the pulses. The ratio of on time to off time t; for the recurring pulses 53 is called the duty cycle and desirably should be relatively short, i.e., a maximum of percent.

The recurring voltage pulses 53 comprise pulsating voltage supply or input means and are applied through connecting or feed resistor 55 to the low potential side of the pilot lights 41 and 43. As shown in FIG. 2, the voltage curve 51 remains at some nominal positive voltage level represented by the voltage drop across the resistor 49 between the occurrence of pulses 53. This voltage level must remain such as to permit the steady state voltage supply 27 to sustain operation of the gaseous lights 41 and 43.

The pilot lights 41 and 43 have a sustaining or holding voltage potential requirement for sustaining operation of the lights and a firing or starting voltage potential requirement for beginning their operation. The steady state voltage supply 27 and the values of the

resistors

45, 47 and 49 are selected so that the voltage drop across the lights 41 and 43 will be greater than the sustaining voltage rating of the lights during the time interval t between the pulses 53. However, without increasing the voltage drop across the lights 41 and 43 to a value greater than the firing voltage ratings for the gaseous lights, the lights cannot be consistently and continuously fired into operation at such time that it is desired to have the lights operate.

Now in accordance with the present invention, the voltage potential applied across the lights 41 and 43 is selectively increased during the time interval 1 by connecting the pulses 53 to the low potential side of the lights through the resistor 55. It is apparent that the total voltage drop across the lights 41 and 43 is the absolute voltage potential applied by the B+ steady state supply and the negative values of the pulses 53. FIG. 2

shows an individual pulse 53 as it instantaneously becomes large in negative value and rapidly increases exponentially toward its original positive value.

The on time t for the pulse is a function of the exponential rise of the pulse 53 and is determinative of the duty cycle of on time to off time for the pulses. It has been determined that the best results are obtained when the duty cycle remains less than a 5 percent maximum ratio as the average currents through the gas lighting devices are not then appreciably increased. The maximum values of the negative pulses 53 are variable depending upon the values of the B+ voltage supply 27, the

resistors

45, 47 and 49, and the firing voltage requirement of the pilot lights 41 and 43. Typically, the pilot lights used have sustaining voltages of approximately 60 to 80 volts and firing voltages of approximately 110 to 150 volts, and the vertical deflection pulses are repetitive at a rate of 60 hertz.

It is to be understood that while the present invention has been shown and described with reference to a preferred embodiment thereof, the invention is not limited to the precise form set forth herein, and that various modifications and changes may be made therein without departing from the spirit and scope of the present invention.

I claim:

1. In a television receiver having voltage sensitive solid state components, a circuit for firing a gaseous lighting device having a pair of electrical terminal means and requiring an input sustaining voltage potential across said pair of terminal means for sustaining operation of said lighting device and in addition an input firing voltage potential across said terminal means greater than said sustaining voltage potential for beginning operation of said lighting device, said firing circuit including in combination: a steady state voltage input means having a voltage amplitude in the range between said sustaining and said firing voltage potentials and being connected to one of said pair of terminal means of said lighting device, and a pulsating voltage input means having recurring voltage pulses and being connected to the other of said terminal means of said lighting device, said voltage pulses being additive with said steady state voltage means for increasing the total voltage potential across said lighting device to a voltage amplitude greater than said firing voltage potential for beginning operation of said lighting device whereby an increased voltage potential is selectively applied across said lighting device while maintaining the amplitude of said steady state voltage means.

2. The firing circuit of claim 1 wherein said pair of terminal means comprises high and low voltage input terminals, said steady state voltage input means is a preselected positive voltage potential and is applied to said high input terminal of said lighting device, and said recurring voltage pulses of said pulsating voltage input means are of a preselected negative voltage potential and are applied to said low input terminal of said lighting device for increasing the total voltage potential applied across said lighting device.

3. The firing circuit of claim 1 wherein said recurring voltage pulses have a time duration of less than 5 percent in comparison to the time duration between said pulses for lowering the power consumption of said lighting device.

4. The firing circuit of claim 1 wherein said television receiver includes a vertical deflection yoke and said vertical yoke is the source of said pulsating voltage input means.