JPH045624A - Liquid crystal panel temperature control circuit - Google Patents

Abstract

PURPOSE:To suppress temperature variation of a liquid crystal panel small by varying the driving source voltage for a fan with the output of a temperature detecting circuit and varying the cooling ability of the fan continuously. CONSTITUTION:This liquid crystal panel temperature control circuit is constituted by adding a temperature detecting circuit 5 which detects the ambient temperature of an optical shutter 2, a DC voltage varying circuit 6 which supplies a variable DC voltage to the cooling fan 4, a multi-output switching power circuit 7 which supplies an output voltage to the circuit 5, a fan soft start circuit 8 which actuates the cooling fan 4 slowly, etc., to a known circuit. The liquid crystal panel temperature control circuit which is thus constituted is used to vary the cooling ability of the fan 4 continuously and the temperature variation of the liquid crystal panel is suppressed small to project a stable image without being affected by the variation in the variation in the ambient temperature, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a temperature control circuit for a liquid crystal panel of a liquid crystal light valve type display device.

2. Description of the Related Art In recent years, liquid crystal light valve type projection display devices that use a liquid crystal panel and a high-intensity lamp such as a metal halide lamp have been attracting attention. Compared to the conventional CRT light bulb type, it has advantages such as being compact, faithful color reproduction, no blooming, less geometric distortion of raster, and no installation adjustment required, and is seen as promising in the future.

Hereinafter, the liquid crystal panel temperature control circuit of the liquid crystal light valve type projection display device described above will be explained with reference to the drawings. FIG. 3 shows an example of a conventional configuration, which includes a light source 1, an optical shank 2 consisting of a liquid crystal panel and a polarizing plate, a projection lens 3,
Consists of a cooling fan. The light from the light St is incident on a light beam controller 2 controlled by a video signal, and by using a projection lens 3, an enlarged image is projected onto a screen (not shown). In order to ensure brightness on the screen, the light source 1 is required to have high brightness, and the optical shutter 2 is required to have high reliability in terms of light resistance and heat resistance. The optical shutter 2 consists of a liquid crystal panel and a polarizing plate, and for example, it is necessary to suppress the surface temperature of the liquid crystal panel to 50 degrees or less and the polarizing plate to 60 degrees or less, and forced air cooling by the cooling fan 4 is essential. In the conventional example shown in FIG. 3, the cooling fan 4 operates at the same time as the light source 1 is turned on to cool the optical shank 2 with a constant air volume.

Problems to be Solved by the Invention However, the conventional device shown in FIG. 3 has the following problems. The voltage and transmittance characteristics of the liquid crystal panel are strongly temperature dependent. Therefore, even if the surface temperature of the liquid crystal panel is kept below 50 degrees, the time required for the temperature to reach a constant level after the light source 1 emits light and the equipment installation will be affected. When the indoor temperature changes, the transmittance changes2, and the brightness of the image on the screen, the darkening of the black, etc. may change significantly.

In view of the above problems, the present invention attempts to perform more effective cooling by varying the cooling capacity of the fan according to the temperature.

Means for Solving the Problems In order to solve the above problems, the liquid crystal panel temperature control circuit of the present invention is constructed as follows.

(1) A temperature detection circuit of the optical shutter section, a variable DC voltage circuit that continuously varies the voltage according to the output signal of the temperature detection circuit, and a cooling fan driven by the variable output voltage of the variable DC voltage circuit. LCD panel temperature control circuit consisting of.

(2) A multi-output switching power supply circuit that supplies one output voltage to the variable DC voltage circuit and another output voltage to another circuit; The LCD panel temperature control circuit consists of a fan soft start circuit that starts up the fan slowly with a time constant.

Effects In this configuration, temperature changes in the liquid crystal panel can be suppressed by varying the fan drive power supply voltage and continuously varying the cooling capacity of the fan based on the output of the temperature detection circuit.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows an example of the configuration of a liquid crystal panel temperature control circuit according to the present invention. In contrast to the conventional example shown in FIG. A supply variable DC voltage circuit 6, a source circuit 7 for multi-output switching that supplies one output voltage to the variable DC voltage circuit 6, and a fan soft start circuit 8 for slowly starting the cooling fan 4 are newly configured. .

FIG. 2 shows an example of a specific circuit configuration of the temperature detection circuit 2, the variable DC voltage circuit 6, and the fan soft start circuit 8.The temperature sensor 9 uses a thermistor, and changes in the midpoint potential with the resistor 10 are detected by the buffer amplifier 11. Amplify with. The DC voltage variable circuit 6 is composed of a transistor 12 having an emitter as an input and a collector as an output, and transistors 13 and 14 that provide negative feedback based on the collector output voltage of the transistor 12 to stabilize the collector output voltage. By varying the above feedback voltage with the output voltage of the amplifier 11, the DC voltage for driving the fan is varied. Also, transistor 15
is a fan on/off switch that cuts off transistor 14 and cuts off transistor 12 when the on/off input is at a high level. Further, the fan soft start circuit 8 is composed of a resistor 16 and a capacitor 17, and when the fan 4 is turned on from an off state, it turns on the transistor 12 with a fixed time constant, and gradually raises the collector potential of the transistor 12. As described above, inrush iui when the fan is turned on is suppressed.

Effects of the Invention As described above, by using the liquid crystal panel temperature control circuit of the present invention, it is possible to continuously vary the cooling capacity of the fan and to suppress temperature changes in the liquid crystal panel. As a result, stable images can be projected without being affected by changes in environmental temperature, etc.

In addition, by using a multi-output switching power source and a fan soft start circuit, a single switching power supply circuit can supply the fan drive power and other circuit power. Fluctuations in the current power source can be made extremely small. As a result, it is possible to configure a fan drive power source that is compact and has cost advantages.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the liquid crystal panel temperature control circuit of the present invention, and FIG. 2 is a concrete circuit 4 of the present invention.
DC cooling fan, 5...Temperature detection circuit, 6...
....DC voltage variable circuit, 7..Multi-output switching power supply, 8..Fan soft start circuit. Name of agent: Patent attorney Shigetaka Awano (1 person) Figure 7-'ft, blind light, fan temperature detection circuit; IT support circuit multi-output switch Electric sacrilege circuit F7 synft start []Route 1! Nnn P-ku Kabe Dolha Ha IIlbo) Ha≦1b Light source Shutter 79 lens;

Claims (2)

[Claims] (1) A liquid crystal panel consisting of a temperature detection circuit for the optical shutter section, a DC voltage variable circuit that continuously varies the voltage according to the output signal of the temperature detection circuit, and a cooling fan driven by the variable voltage. Temperature control circuit. (2) a multi-output switching power supply circuit that supplies one output voltage to the variable DC voltage circuit and another output voltage to another circuit; 2. The liquid crystal panel temperature control circuit according to claim 1, further comprising a fan soft start circuit that slowly starts the fan by giving a time constant to startup.