JPH0244192B2 - BIIMU * PENETOREESHONINKYOKUSENKANYOKODENATSUKARAASUITSUCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high voltage color switch for beam-penetration cathode rays, and more particularly:
A small, low cost color switch for changing the voltage level of the accelerating anode of a beam penetration cathode ray tube.

Beam penetration color CRTs (cathode ray tubes), as they are commonly known, are display devices having a fluorescent screen on which images or text can be drawn. One or more phosphor layers on the inner surface of the phosphor screen can be selected to emit visible light at most desired wavelengths. If two layers of phosphor are provided on the inner surface of the phosphor screen, two or more different colors can be produced by varying the depth of penetration of the electron beam into the phosphor layer.
Since the electron beam emitted by the cathode in the neck of the CRT impinges on the phosphor layer at a speed that is primarily influenced by the voltage level of the accelerating anode, a change in the voltage level applied to the accelerating anode will affect the two-layer phosphor layer. causes a corresponding change in the proportion of light emitted by the In other words, in a penetration CRT that has two layers of phosphors that emit different light,
Up to four colors can be displayed by changing the DC voltage level applied to the accelerating anode placed near the front of the CRT.

A significant limitation encountered when using penetration CRTs is related to the length of the reset time between successive exposure times, since the DC voltage level of the accelerating anode must be changed during the reset time. The length of is determined primarily by the capacitance of the accelerating anode. Because the accelerating anode has a relatively large size and therefore an inherently large capacitance, it accumulates a significant amount of charge during the imaging time. Of course, the addition of capacitors, especially large capacitors often used in high voltage power supplies, increases the capacitance in the high voltage circuit and further lengthens the reset time. As this charge increases or decreases as the voltage level of the accelerating anode changes, the reset time separating successive imaging times is related to the charge/discharge rate determined by the total capacitance seen by the high voltage power supply.

Other limitations found in known color switches used in beam penetration CRTs are:
It is related to the switching order of colors displayed on a CRT fluorescent screen. 3 to 2-layer penetration CRT
Although it is possible to display a color or four distinct colors, certain high voltage color switches must operate in a specific order. In other words, the high voltage color switch applies one preselected voltage level to the accelerating anode during successive imaging times. That is, the anode voltage is, for example, from 10kV to
to 14kV, from 14kV to 18kV and finally to 18kV
to the first 10kV. At each successive imaging time, the image or character written by the voltage beam appears only in a color corresponding to the voltage level applied to the accelerating anode. If an image or character is to appear in one color, e.g. red, during a particular rendering time, the next time the red color information is to be displayed after the completion of that rendering time, the high voltage color switch is set to that preselected voltage level. It cannot appear until the imaging time when a voltage level corresponding to the red color is applied to the accelerating anode again.

Reference may be made to U.S. Pat.
There is number 3906333. This patent specification describes a switching high voltage power supply for use in beam penetration type cathode ray tubes.
In this power supply, the secondary winding of a high voltage step-up transformer is connected in series with the accelerating anode of the cathode ray tube. The primary winding of this transformer is connected to ground through a capacitor to generate a DC voltage level. The voltage across this capacitor is applied to the baseline DC high voltage regulation input. The color switching power supply of the present invention is an improvement on that described in this patent.

Other patents to refer to include the May 30, 1978 patent titled “Switch-operated High Voltage Power Supply System.”
There is a date US Pat. No. 4,092,556. This patent describes a high voltage power supply for fast switching of high voltage applied to the anode of a beam penetration color cathode ray tube. The energy for fast transitions between voltage levels is stored in two inductors, one for the upward transition and one for the downward transition. When it is desired to change the voltage applied to the cathode ray tube, the appropriate one of the storage inductors is connected to the anode through a control switch to rapidly change the voltage applied to the anode. The voltage increases until it reaches the desired upper voltage corresponding to the desired color, at which point the switch is turned off and the storage inductor is recharged. Once a predetermined voltage level is reached, the high voltage power supply maintains the anode at that voltage level by a tracking action.

It is an object of the present invention to create a compact, low cost beam system with a relatively short reset period between each exposure time.
An object of the present invention is to provide a high voltage color switch for penetration CRT.

Beam penetration CRT according to the invention
A feature of the high voltage color switch is that the charge stored on the CRT's anode can be changed quickly so that switching to different colors can occur after a short reset time.

Beam penetration CRT according to the invention
The advantage of high voltage color switches is that energy is conserved and relatively little energy is lost as heat. Therefore, the color switch becomes small and lightweight, making it suitable for use in aircraft cockpits and the like.

According to the invention, beam penetration
A high voltage color switch for a CRT includes a high voltage power supply connected to the accelerating anode of the CRT through a transformer secondary winding. The primary winding of the transformer is connected to ground through a low pass filter. Color-specifying information is applied to the primary winding of the transformer, and from there to the secondary winding, where it is superimposed on the high-voltage DC level from the high-voltage power supply and varies the DC voltage level applied to the accelerating anode. Set to . A feedback loop detects the average voltage level on the primary winding,
Drive it to zero. A DC voltage corresponding to the DC voltage thus removed is applied to the accelerating anode of the CRT by adjusting the reference input to the high voltage power supply to change its high voltage DC level.

Beam penetration CRT according to the invention
For the above and other purposes of high voltage color switch,
The features and advantages will become clearer in the following description of preferred embodiments thereof with reference to the drawings.

First, referring to FIG. 1, a sequential beam penetration CRT according to the present invention is shown.
One embodiment of a color switch is shown. A high voltage power supply 10 of known type is provided and connected by conductors 12 to one side of a secondary winding 14 of a transformer 16. The other side of the secondary winding 14 is connected by a conductor 18 through a damping resistor 20 to a beam penetration CRT (cathode ray tube) 22. As is well known, the CRT 22 includes an anode 24 to which a high voltage is applied which directs a beam of electrons emitted by a cathode (not shown) located in the neck of the tube in front of the CRT 22. Accelerate toward the fluorescent screen 25 that is located. The inner surface of the fluorescent screen 25 typically has at least two
A layer of phosphor is provided, each layer emitting light of a different wavelength or color in response to stimulation by the electron beam. For the purpose of explaining the present invention, the fluorescent screen 25
It is assumed that the inner surface of the phosphor is provided with one fringe color phosphor layer and one red phosphor layer, but it will be appreciated that phosphors that emit light of various colors may be used. Of course, more than two phosphor layers can also be used. The anode 24 is made of a highly conductive material and is placed near the front of the CRT 22 and around the periphery of the CRT 22 . Because of its large size, anode 24 has a relatively large capacitance and is shown as a capacitor in FIG. 1 for ease of illustration.

The transformer 16 also has a primary winding 26, and the turns ratio of the primary winding 26 to the secondary winding 14 is matched to circuit characteristics as is well known. For example, the turns ratio is 1:
1000, if the voltage across the primary winding 26 changes by 4V, the voltage across the secondary winding 14 will change by 4kV. This voltage swing, if symmetrical with respect to ground potential, would result in a swing from -2kV to +2kV in the secondary winding. In this embodiment, one end of the primary winding 26 is connected to ground, and the other end is connected to one side of the resistor 30 by a conductive wire 28. The other side of resistor 30 is connected by conductor 32 to a capacitor 34, the other side of which is connected to ground. The resistor 30 and capacitor 34 are
It acts as a low pass film that integrates the voltage waveform on conductor 28 to primary winding 26 of transformer 16.

Color specifying information is provided to the high voltage color switch of the present invention via conductors 36 and 38 from an external signal source (not shown). Various types of external signal sources can be used, but for simplicity, select which of the four colors to input to the color switch from the CRT2.
It is assumed that the signal is a 2-bit digital signal that can specify whether the signal is displayed in 2 bits or not. This digital signal is given to the D-A converter 40, where
It is converted into an analog signal with a level corresponding to the color displayed on the CRT. The output signal from the D-A converter 40 is provided to a drive circuit, such as an operational amplifier 44, where it is amplified and connected to the primary winding 2 of the transformer 16.
6 is applied to the primary winding 26 as a signal having a voltage level and waveform suitable for driving the primary winding 26.

As a feature of the invention, the primary winding 2 of the transformer 16
A feedback loop is included that detects the average (DC) voltage level of the waveform applied to 6 and adjusts the output level of drive circuit 44 to maintain it at zero. The feedback loop includes an operational amplifier 52 connected to conductor 32 at one input end for detecting the DC component of the signal waveform applied to primary winding 26. The other input terminal of operational amplifier 52 is connected to ground. The output end of operational amplifier 52 is connected to the input end of operational amplifier 44 via conductor 54 .

Another feature of the invention is a low pass filter 48 that detects changes in the DC voltage level as the duty cycle of the output signal from the DA converter 40 changes, as will be explained in more detail below. is conductor 4
6 is connected to the conductor 42, and the DC voltage level detected by the integral action is connected to the reference terminal of the high voltage power supply 10 via the conductor 50 in order to proportionally change the level of the output voltage from the high voltage power supply 10. given to.

Also, as a feature of the invention, means are provided for creating a focus voltage that dynamically tracks the high voltage level applied to the anode. In the preferred embodiment, this means includes a first potentiometer 60 connected to the output of the high voltage power supply 10. This output is separate from the output used to supply the anode voltage and has a DC voltage level lower than the anode voltage. The first potentiometer 60 is connected to the second potentiometer 65 through a winding 64 added to the transformer 16. Potentiometer 65 is used to dynamically adjust the voltage applied to a focusing electrode 66 located near the front of the electron gun (not shown). Typically, the focusing voltage level applied to the focusing electrode is a level of a fixed percentage of the voltage applied to the anode 24. An advantage of this focusing system is that it requires a minimum of additional components, namely two potentiometers 60,
65 and an additional winding of the transformer 16. The first potentiometer 60 adjusts the DC baseline voltage level, while the second potentiometer 65 adjusts the dynamic output to the level applied to the focusing electrode 66.

Referring now to FIG. 2, the operation of the sequential color switch according to the present invention will now be described. All the vertical axes are voltages, and the subscripts of the symbols written correspond to the symbols attached to the conductive wires in FIG. The horizontal axis is time. The color switch switches the rendering time for each of the four colors in a predetermined switching order by applying a step voltage waveform to the accelerating anode 24. In other words, the voltage level applied to the anode 24 is from 10kV to 12kV, 12kV
to 16kV, then from 16kV to 18kV, and finally
From 18kV back to the initial 10kV. In the anodic voltage purification of the duty cycle as shown in the left half of FIG. 2, each imaging time is approximately equal in length, so
No overall change occurs in the DC voltage level compared to the 14kV baseline.

However, if a digital signal is provided from an external signal source indicating that the rendering time for one particular color, such as red, should be longer than the rendering time for other colors, then the right half of FIG. This results in an asymmetrical waveform as shown, and the average DC voltage level is no longer zero. It is known that a DC voltage cannot be maintained across the primary winding 26. According to the invention, the operational amplifier 52 is connected to the conductor 3 at one input.
2, the terminal voltage of the capacitor 34 corresponding to the DC voltage level across the primary winding 26 is detected and fed back to the input end of the drive circuit 44. Thereby, the DC voltage level of the voltage waveform applied to the conducting wire 28 is adjusted. In other words, driving is performed by the feedback loop so that the DC voltage level of the signal waveform applied to the primary winding 26 is brought to zero.

The voltage waveform generated at the secondary winding 14 is the same as that at the primary winding 26.
It is the same as the voltage waveform in , and swings from the negative side of the nearly zero DC voltage level to the positive side. Therefore, in relation to the duty cycle, there will be a shift in the discrete DC voltage levels applied to the accelerating anode 24, resulting in a shift in the colors appearing on the fluorescent screen. To compensate for such deviations, a low pass filter detects changes in the duty cycle of the waveform from the DA converter and proportionally adjusts the high voltage DC level from the high voltage power supply 10. A voltage level is applied to high voltage power supply 10 via conductor 50 .

While the invention has been illustrated and described with respect to preferred embodiments thereof, those skilled in the art will recognize that various changes may be made in form and detail without departing from the scope of the invention.

[Brief explanation of drawings]

FIG. 1 shows in block form a sequential color switch for a beam penetration CRT according to the present invention. FIG. 2 is a diagram showing waveforms at various points in the embodiment of FIG. 10...High voltage power supply, 14...Secondary winding, 16
...Transformer, 20...Damping resistor, 22...
Beam penetration cathode ray tube (CRT), 2
4... Accelerating anode, 25... Fluorescent screen, 26... Primary winding, 30... Resistor, 34... Capacitor, 40
...D-A converter, 44 ... Drive circuit (operational amplifier), 48 ... Low-pass filter, 52 ... Operational amplifier, 60, 65 ... Potentiometer, 64
...Additional winding, 66...Focusing electrode.

Claims (1)

[Scope of Claims] 1. A high voltage color switch for a beam penetration cathode ray tube that displays a color corresponding to a voltage level by switching the voltage level, the switch being connected to the cathode ray tube and displaying a color corresponding to the voltage level. a high voltage power supply means having an output voltage level selected to cause a first predetermined color to appear on the tube; and transformer means connected between an output of the high voltage power supply means and the cathode ray tube. , drive circuit means that amplifies an input waveform applied to an input terminal and supplies it to the transformer means; feedback means that detects a DC component of the input waveform and feeds it back to the input terminal of the drive circuit means; and integrating means for applying a DC voltage level obtained by integrating a waveform to a reference terminal of the high voltage power supply to change the output of the high voltage power supply by an amount proportional to the DC voltage level of the input waveform. A high voltage color switch for beam penetration cathode ray tubes.