JPS6318892A - Projection type image receiver - Google Patents

Abstract

PURPOSE:To efficiently utilize the allowance of an actual conductible beam current and to supply a screen with a high luminance by adding an auxiliary shunt circuit which shunts the beam current in accordance with the temperature of a tube body in respective projection tubes only when the excessive beam current is biased to one of the plural projection tubes and flows. CONSTITUTION:A main shunt circuit 12 shunts the beam current and controls the increase in temperature of projection tubes 2-4 by an ambient temperature sensor 12a in which resistance value decreases with the increase of ambient temperature (temperature inside a set, for example) of projection tubes 2, 3 and 4. The auxiliary shunt circuit 13 is constituted in such a way that transistors Q2-Q4 for shunting in which tube body temperature sensors 2a-4a are set to emitter resistances are parallelly connected through diodes D2-D4 and branch-connected between partial pressure resistances R2 and R3. If the beam current is biased to one of the projection tubes and flows at the time of impressing a single-color signal, the beam current flowing in respective projection tubes lose their balance, and one of diodes D12-D14 in a single-color detection circuit 13a becomes conductive, whereby the auxiliary shunt circuit 13 operates and beam current corresponding to the tube body temperature at every projection tube is shunted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a projection type image receiving device that limits the beam current of a plurality of projection tubes based on the ambient temperature and the tube body temperature of each projection tube. Regarding.

[Prior Art] A projection type image receiving apparatus that projects images from a plurality of projection tubes onto a screen in all directions is ideal for large-scale audiovisual media in theaters, stadiums, public facilities, and the like. The conventional projection type image receiving device I shown in FIG. The configuration is such that RGB output is applied to each corresponding projection tube 2, 3.4. Projection tube 2, 3.4
In both cases, a liquid-filled layer 7c is disposed between the CRT picture tube 7a and the plastic lens mechanism 7b for enlarging the image in order to maintain the continuity of the refractive index of light and increase the cooling effect. The flyback transformer 8, which supplies beam current to the anode of each projection tube 2, 3.4, is used by the horizontal output circuit 9 to amplify and rectify the horizontal retrace pulse generated during the horizontal retrace period. The size of the projection tube 2.3.4 is closely related to the screen brightness and body temperature of each projection tube 2.3.4, so the beam current is set as high as possible to maximize the screen brightness, while a temperature of around 80°C is recommended for safe use. In order to protect the plastic lens mechanism 7b from overheating, which is considered to have a limit, it is necessary to impose a certain limit on the beam current.

[Problems to be Solved by the Invention] The above-mentioned conventional projection type image receiving device l limits the beam current by setting the ambient temperature of the projection tubes 2, 3.4 to room temperature at the installation location, and setting the ambient temperature of the projection tubes 2 to 4 to Even when the temperature of the tube increases the most due to overheating, the practical limit temperature (e.g. 50℃)
It is designed with the condition that it is suppressed so that it does not exceed. For this reason, as shown in FIG. 4, for example, at installation locations where the room temperature is 10°C and 20°C, the beam current I. From I,. The beam current is further suppressed to 13G in the installation location where the room temperature is 30℃, so that it can withstand use under the worst usage conditions, but in reality there is a considerable margin in the beam current. Despite this, because the beam current is considerably limited in consideration of the worst case scenario, the brightness of the screen 5 is inevitably low, resulting in unnecessarily sacrificing the brightness of the screen, etc. There was a problem.

[Means for Solving the Problems] The present invention solves the above problems, and is a projection type image receiving device that projects images onto a screen from a plurality of projection tubes. a main shunt circuit that operates according to the ambient temperature and limits a rise in ambient temperature by dividing the beam current supplied to all the projection tubes; A sub-shunting circuit that operates according to the tube body temperature of each projection tube only when an excessive beam current flows through the projection tube, and limits the rise in tube body temperature by dividing the beam current supplied to all projection tubes. The present invention is characterized in that it is configured by providing the following.

[Function] This invention divides the beam current supplied to all the projection tubes by a main shunt circuit that operates according to the ambient temperature of the plurality of projection tubes, limits the increase in the ambient temperature, and Only when an excessive beam current flows unevenly through one of the projection tubes, the beam current supplied to all projection tubes is divided by a sub-shunting circuit that operates according to the tube body temperature of each projection tube. flow to limit the rise in temperature of the tube.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG. 1.2. FIG. 1.2 is a circuit configuration diagram and a beam current limiting characteristic diagram, respectively, showing an embodiment of the projection type image receiving apparatus of the present invention.

In FIG. 1, the projection type image receiving device 11 has 6 projection tubes 2° 3.4
A main shunt circuit 12 that limits the beam current according to the ambient temperature and a single projection tube 2 are connected between the secondary winding of the flyback transformer 8 that supplies beam current to the
．． A sub-shunt circuit 13 is connected to each projection tube 2, 3, and 4 to limit the beam current according to the tube body temperature of each projection tube 2, 3, and 4 when a so-called monochromatic signal is applied in which the beam current is biased only to 3 or 4. In this embodiment, the secondary winding of the DC power supply 1B and the flyback transformer 8 is connected to the voltage dividing resistors R1°R2, R2.
3, and the main shunt circuit 12 and the sub shunt circuit 13 are branch-connected downstream of the voltage dividing resistors R3 and R2, respectively.

The main shunt circuit I2 is composed of a parallel connection circuit of a smoothing capacitor CI, a resistor R4, and an ambient temperature sensor 12a consisting of a temperature sensing element. The beam current is shunted by the ambient temperature sensor 12a, which decreases the beam current to the projection tubes 2, 3 .
4. Control the temperature rise. The sub-shunt circuit 13 includes tube body temperature sensors 2a, 3a, and 2a provided for each projection tube 2, 3.4.
4a is the emitter resistance of the shunt transistor Q2゜Q3. Q4 is connected to the collector of a diode D2. D3. D4, and this parallel connection circuit is branch-connected between voltage dividing resistors R2 and R3, and transistors Q2, Q3, . Q4 is made conductive by the monochromatic signal detection circuit 13a activated when a monochromatic signal is applied, and the beam current is shunted.

The monochromatic signal detection circuit 13a has color difference signals R-Y, G-Y, B-Y, which are generated by the video output circuit 6, applied to its base, and emitter resistors RI2. R13゜Resistance R common to R14
Three transistors Q+2.15 connected to ground. Q
I3. Q! 4 and these three transistors Q12 to Q
Each of the 14 collectors has a diode D12°DI3. It is connected to the base via DI4, and the collector output is voltage-divided to the shunting transistor Q2.
- It has a transistor Q+ etc. which becomes the base input of Q4. 3 transistors Q+2~Q! 4 mutually constitute a differential pair, and one of the transistors QI2 .
When the emitter current of Q+3 or Q10 increases, the corresponding diode DI2°DI3 or 014 becomes conductive, and the monochromatic signal application state is detected. Note that the transistor Q12
~The line connecting the collector of Q14 and diodes DI2 to DI4 and the DC power supply +Bl are capacitors C2, C3゜C4
The monochromatic signal detecting circuit 13a is connected to the monochromatic signal detection circuit 13a through the monochromatic signal to ensure smooth operation so that the monochromatic signal detection circuit 13a does not operate due to an instantaneous monochromatic signal. Furthermore, a parallel connection circuit consisting of a resistor R5 and a capacitor C5 is connected between the emitter of the transistor Q1 and the emitter resistor R6 in order to stabilize the emitter voltage.

Here, when the ambient temperature of the projection tubes 2 to 4 increases, the resistance value of the ambient temperature sensor 12a decreases, and as a result, a portion of the beam current is shunted more than before, and as a result, the beam current is limited. , projection tube due to rise in temperature inside the set 2.3.
4, particularly the plastic lens mechanism 7b, from being deformed or cracked due to temperature rise.

Moreover, when a monochromatic signal is applied, an excessive beam current flows biasedly to only one of the projection tubes 2 to 4. in this case,
The imbalance of the beam current flowing through each projection tube 2, 3.4 is due to the transistor Q! in the monochromatic signal detection circuit 13a! It is detected that the balance of the emitter currents flowing through diodes D12 to Q14 is disrupted, and one of the diodes D12 to DI4 becomes conductive, thereby activating the sub-shunt circuit I3. As a result, the temperature of each projection tube 2, 3.4?
The beam current is divided accordingly, and the problem of abnormal overheating of a single projection tube due to an excessive beam current is prevented. In this case, for example, the beam current shunted by the transistor Q2 is caused by the emitter resistance R of the transistor Q1.
The value obtained by subtracting the base-emitter voltage from the voltage obtained by dividing the power supply voltage of the DC power supply +B2 by the base bias resistance of the transistor Q2 and the base bias resistance of the transistor Q2 is divided by the resistance value of the tube body temperature sensor 2a.

In this way, the projection type image receiving device 11 has a main shunt circuit 12 that operates according to the ambient temperature of the plurality of projection tubes 2, 3.4.
This divides the beam current supplied to all the projection tubes 2 to 4 to limit the rise in ambient temperature, and distributes the beam current to any one of the plurality of projection tubes 2 to 4, 2.3 or 4. A sub-shunt circuit 13 operates according to the tube temperature of each projection tube 2, 3.4 only when an excessive beam current flows.
As a result, the beam current supplied to all the projection tubes 2 to 4 is diverted to limit the increase in the temperature of the tube body, so an overall monitoring point that constantly monitors the ambient temperature of the plurality of projection tubes 2 to 4 is provided. If only one of the projection tubes 2.3 or 4 causes an increase in tube body temperature due to excessive beam current,
Through individual monitoring that uniformly limits the beam current of all projection tubes 2 to 4, fine-grained beam current limitation is possible, which is different from the conventional method that takes into account the worst-case condition of tube body temperature and provides a safety margin. On the other hand, as shown in Figure 2, the actual room temperature setting is suppressed to a sufficiently low value, and the large beam N flow is allowed to flow until the tube body temperature of projection tubes 2 to 4 reaches the practical limit. By placing a limit on the beam current when the beam current increases more than that, it is possible to effectively utilize the beam current margin that can actually be energized and provide a high-brightness screen. can be well protected from damage caused by overheating.

In the above embodiment, the projection type image receiving device 11 has a three-tube configuration, but the number of projection tubes is not limited to three, but may be four or more. The present invention is not limited to the one using the liquid-cooled plastic lens mechanism 7b, but may be one using a non-liquid-cooled glass lens mechanism.

[Effects of the Invention] As explained above, the present invention divides the beam current supplied to all projection tubes by using a main shunt circuit that operates according to the ambient temperature of a plurality of projection tubes, thereby reducing the rise in the ambient temperature. In addition, a sub-shunt circuit operates according to the body temperature of each projection tube only when an excessive beam current flows unevenly to one of the multiple projection tubes.
The beam current supplied to all projection tubes is divided to limit the rise in tube temperature, so there is an overall monitoring eye that constantly monitors the ambient temperature of multiple projection tubes, and one projection tube In cases where an excessive beam current causes a rise in tube body temperature, fine-grained beam current limitation is possible through individual monitoring that uniformly limits beam current for all projection tubes. Unlike the conventional method that considers the worst-case temperature conditions and allows for a safety margin, the actual room temperature setting is kept to a sufficiently low value, and the temperature of the projection tube body is kept at the practical limit.
By allowing a large beam current to flow and limiting the beam current when the tube body temperature increases beyond that, the beam current margin that can actually be passed is effectively used to provide a high-brightness screen. In addition, the projection tube can be well protected from damage due to overheating, and other excellent effects can be achieved.

[Brief explanation of the drawing]

Fig. 1.2 is a circuit configuration diagram and beam current limiting characteristic diagram showing an embodiment of the projection type image receiving device of the present invention, respectively, and Fig. 3.4 is a circuit showing an example of a conventional projection type image receiving device, respectively. FIG. 2 is a configuration diagram and a beam current limiting characteristic diagram. 2. 3.4. ,,projection tube, 2a, 3a, 4a,. , tube body temperature sensor, 5. ,,Screen,11. . , projection type image receiving device, 12. ,, main shunt circuit, 12゜00
Ambient temperature sensor, 13. ,,sub-shunt circuit.

Claims (1)

[Claims] A projection type image receiving device that projects images onto a screen from a plurality of projection tubes, which operates according to the ambient temperature of the plurality of projection tubes, and divides the beam current supplied to all the projection tubes to adjust the temperature of the surrounding area. a main shunt circuit that limits temperature rise, and operates according to the tube body temperature of each projection tube only when an excessive beam current flows biasedly to any one of the plurality of projection tubes; A projection type image receiving apparatus comprising a sub-shunt circuit that limits the rise in temperature of the tube by dividing the beam current supplied to all the projection tubes.