JPH03287189A - Temperature control method for discharge tube - Google Patents

Abstract

PURPOSE:To suppress the temperature variation of other elements small by predicting the temperature variation of a sensor element from its element driving state variation and varying the set temperature of the sensor element according to the driving state. CONSTITUTION:A prediction block 301 estimates element heating value variation due to driving variation from a driving signal Lc and a thermal inertia block 302 adds time delay up to when the element driving variation appears as element temperature variation. Then the temperature of the sensor element which is estimated at the moment, i.e. predicted sensor element temperature Ts is obtained as the output, a comparator 303 compares the Ts with measured temperature corresponding to S4 to control the temperature of the sensor element S4 through a fan Fx, and then temperature variation due to the driving state variation of Pc becomes the temperature variation of Pc. Consequently, the temperature variation range of the element varies from + or -alpha to alpha and is reduced to half.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is capable of displaying characters and images on a large screen by arranging a large number of fluorescent lamp-emitting discharge tubes in a matrix and individually controlling the lighting of each discharge tube. The present invention relates to a discharge tube temperature control method for maintaining and controlling the temperature of the entire arc tube constituting the screen within a predetermined range in order to maintain good luminous efficiency of the arc tube in a large screen display device that displays.

Conventional Technology Generally speaking, the luminous efficiency of a discharge tube based on the luminous principle of a fluorescent lamp system is determined by the operating temperature of the luminous efficiency when an arc tube based on the luminous principle of a fluorescent lamp system is used as a light emitting element of a large screen display device. In order to maintain the brightness of the screen uniformly, it is necessary to maintain the operating temperature of the arc tube within a constant range over the entire screen, regardless of the ambient temperature.

Fluorescent lamp-type light-emitting elements emit light by utilizing the fact that the ultraviolet rays emitted by mercury vapor sealed in the discharge tube during discharge excites the phosphor, causing the phosphor to emit light. This is necessary because the contributing intensity of the generated ultraviolet rays greatly depends on the mercury vapor pressure and, later, on the operating temperature. In general, fluorescent lamp elements have high luminous efficiency at temperatures between 40° C. and 80° C., and the efficiency rapidly decreases at temperatures above and below that temperature. Therefore, in a large screen constructed by arranging light emitting elements in a matrix, if a part of the screen operates outside the above temperature range, that part becomes dark and the brightness of the screen becomes uneven.

In order to avoid such inconveniences, conventional large-screen devices using fluorescent light-emitting devices have been equipped with a temperature control loop, which maintains the temperature of the device within a predetermined temperature range during device operation. do. FIG. 5 is a block diagram showing the system and model of the conventional method. In Fig. 5, Pc is a specific discharge tube on a large screen constructed by arranging a large number of discharge tubes in a matrix, and this discharge tube is equipped with a temperature sensor So to measure the operating temperature. (hereinafter, this discharge tube will be referred to as a sensor element). Px is the sensor element P
Arbitrary elements other than c, no, and Dx are drive circuits that drive them, and drive currents flow through the elements in accordance with drive signals LO+LX. Fx is a fan for controlling the operating temperature of the discharge tube. Since the discharge tube normally raises the temperature required for operation by self-heating during lighting, if excessive temperature rise is controlled by the fan Fx, the operating temperature can be maintained within a predetermined range. That is, if the feedback loop is operated to maintain the actual temperature measured by So at the desired set temperature 're, many elements other than the sensor element PC will also have a temperature close to the temperature of PC, and the objective will be achieved. To achieve this, the fan Fx must act uniformly and evenly on the elements of the entire screen.

Problems to be Solved by the Invention However, in the conventional temperature control method described above, the operating temperature of the sensor element is fixed at the set temperature Tc regardless of the operating state of the sensor element, so that the operation of open loop elements other than the sensor element is The temperature range fluctuates depending on the operating state of the sensor element, and the temperature distribution range of the discharge tube elements becomes wide on the screen as a whole, making it difficult to keep all the elements on the entire surface of the screen 5 within a desired temperature range. The details will be explained using FIG.

FIG. 6 schematically shows how the temperature of PX changes under the control operation of the configuration shown in FIG.

In FIG. 6a, it is assumed that before time to, Pc and Px are in a non-lighted state, and the operating temperature is stable at 're. Assuming that the sensor element pc lights up on the current side to, and the other elements including Px change to a non-lighting state, the pc
If the temperature control did not work, the temperature would rise due to the heat generated by lighting, but the temperature control works and Fx operates in the direction of cooling the entire screen, and the PC temperature is maintained at Tc, but Px Since it is 11 which is not lit, it is excessively cooled and its temperature becomes Tc-α (α is a certain constant) at time t1. The temperature change when Pc changes from lighting to non-lighting does not change stepwise due to thermal inertia, but changes gradually as shown in the figure.

Considering the same way, at time t2, pcOFF, PxON,
P at t5. ON, PxON, poON at t4, Px
Figure 6 shows the Pc and Px temperatures when the ON and lighting conditions change. According to the figure, it can be seen that although the PC is maintained at a constant temperature 're, Px changes ±α. As already mentioned, the operating temperature of the discharge tube element is in the range of about 40° C. to 80° C., and ±α must be within this range. However, in an actual device, ±α becomes a large f value, making it difficult to realize sufficient temperature control for the discharge tube.

The present invention aims to halve the temperature fluctuation range ±α to ±1/2α, thereby narrowing the operating temperature distribution of the discharge tube.

Means for Solving the Problems In order to achieve the above object, the present invention predicts temperature fluctuations due to changes in the driving state of the sensor element from the drive signal for driving the sensor element and thermal inertia characteristics, and adjusts the settings of the sensor element. The temperature is not set to a constant value Tc as described above, but is changed depending on the driving state to suppress temperature fluctuations of other elements Px.

Operation By configuring the present invention as described above, it is possible to obtain the effect of compactly compressing the temperature fluctuation range of the other elements PX.

Embodiment FIG. 1 shows a basic system for realizing the present invention. In FIG. 1, nc is a drive circuit for driving the sensor element pc, which receives a drive signal Lc and flows a drive current to the sensor element in accordance with the drive signal Lc. Since the power consumption of a PC is a function of the drive current, the temperature rise can also be estimated from the drive signal. Therefore, the prediction block (means) 301 estimates the element heat amount change 'rr due to the drive change from the drive signal LC, and further the thermal inertia block (means) 302 estimates the element drive change (power consumption change).
By adding the time delay at 1, so-called thermal inertia, which appears as a change in element temperature, we obtain the temperature that the sensor element will be at at that moment as an output, that is, the predicted sensor element temperature (Ts), and the actual measured temperature by this Ts and Sc. are compared by the comparator 303, and the temperature of the sensor element Sc is controlled by the output of the comparator 303 via the fan FX as a temperature control means, the temperature fluctuation caused by the change in the driving state of the PC becomes the temperature fluctuation of the PC, and the fifth
As in the case shown in the figure, the temperature of Pc is constant and the temperature of PX does not fluctuate. As a result, the temperature of PC9Px in various drive states changes as shown in Figure 6 to Figure 2, and the drive fluctuation of the sensor element is caused by the temperature change of the sensor element, and the drive change of other elements is caused by each element. The temperature change will be . As a result, as shown in Figure 2, the element temperature change range is ±α-
・It becomes α and is halved.

In FIG. 1, if there is no thermal inertia block 302, in a transient state where the drive of the PC changes, the temperature of the PC changes rapidly following the change in the drive signal, so the temperature control ability The temperature of Px changes rapidly, resulting in an overshoot that would not be present if the thermal inertia block 302 were present. This state is shown in FIG.

FIG. 4 shows the configuration of a second embodiment of the present invention. In FIG. 4, Pu, Pd, Pl, and Pr are discharge tubes arranged on the upper, lower, left, and right sides of the sensor element pc, and are driven by respective drive circuits Du, Dd, Dl, and Dr.

The temperature of the sensor element PC is strongly influenced not only by the heat generated by the nine vanes itself, but also by the heat generation status of peripheral elements, so it is better to predict the driving status of the peripheral elements more accurately. can be predicted.

Since the coefficients by which the drive signals of the peripheral elements contribute to the temperature change of the sensor element pc are different, the coefficient calculation block 3
00, coefficients are calculated for each drive signal component, and a prediction block 301 calculates the temperature change of the sensor element Pc. The temperature change of the sensor element is influenced by the lighting state of the sensor element and peripheral elements as well as the ambient temperature (the temperature difference between the sensor temperature and the ambient temperature). This is because the effectiveness of the cooling fan F) increases as the ambient temperature decreases, and its operating state changes depending on the ambient temperature. Therefore, the temperature change in the prediction block 301 is usually determined by taking the ambient temperature into account. The thermal inertia block 302 adds a response delay due to thermal inertia, as described above. Since the change in element temperature with respect to the change in heat amount can be approximated by an exponential function, the contents of block 302 are stored in memory 30 as shown in FIG.
This can be realized by a recursive filter whose feedback coefficient is K, which is a combination of 4 and 10 and the calculator 305. By increasing K, the time constant can be lengthened.0 As described in detail, according to the present invention, the temperature distribution range of a large number of discharge tubes constituting a large screen can be controlled in a manner similar to that achieved by conventional control methods. It becomes possible to compress the image to approximately 100%, and it is possible to realize a uniform screen with little unevenness in brightness.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of a temperature control method for a discharge tube according to an embodiment of the present invention, FIG. 2 is a characteristic diagram for explaining the temperature characteristics of an element with the same configuration, and FIG. A waveform diagram for explaining characteristic deterioration when a part of the same configuration is omitted, FIG. 4 is a block diagram showing the second embodiment of the present invention, and FIG. 6 is a block diagram showing the configuration of the conventional example. , FIG. 6 is a characteristic diagram showing the temperature fluctuation characteristics of the element according to the configuration of the same block diagram. PX...discharge tube, pc...specific discharge tube, Fx...11...fan, 301...predicted flock, 30
2...Thermal inertia block, 303...Comparator.

Claims (2)

[Claims] (1) By arranging a large number of small discharge tubes in a matrix and controlling the light emission of the small discharge tubes individually, when displaying certain information as a whole on a large screen display, one of the small discharge tubes arranged in a large number identify the individual as a specific discharge tube,
At the same time as actually measuring the temperature of the specific discharge tube, drive signals of the specific discharge tube whose temperature is actually measured and a plurality of discharge tubes around it are detected, and an operating temperature value that should originally be set for the specific discharge tube is determined from the detected drive signal. is estimated by an estimating means, the estimated temperature value is compared with the actually measured temperature value by a comparing means, and the temperature control method is used to control the actually measured temperature value by a temperature control means so as to approach the estimated temperature value. . (2) The temperature control method for a discharge tube according to claim 1, wherein when determining the estimated temperature value, a delay in temperature change with respect to a change in the drive signal due to the thermal inertia means is taken into consideration.