JP2012204338A - Safe and long-life ccfl lighting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide safe and long-life cold-cathode fluorescent lamp (CCFL) lighting by controlling a tube current in advance so that a tube temperature may be optimum for the CCFL.SOLUTION: A tube temperature control device measures a predetermined time interval after a CCFL is turned off, and detects a tube temperature and a tube current. The tube temperature control device compares the detected tube current with data on an optimum tube current value, which is stored in a control unit, corresponding to the CCFL tube temperature, and controls a tube current value so that the optimum tube temperature may be reached. By controlling the tube current value before the tube temperature is saturated so that the CCFL tube temperature, which changes significantly depending on the ambient temperature, may be at the optimum value, the CCFL can be turned on at the optimum luminance suited to the ambient temperature.

Description

The present invention relates to an illuminator using a cold cathode fluorescent tube (hereinafter referred to as CCFL).

The present invention relates to a CCFL tube temperature control method, which provides a safe and long-life CCFL illumination by performing tube temperature prediction processing and controlling tube current in advance so that the tube temperature is optimal for the CCFL. is there.

CCFL is a light source with many years of experience in backlights for liquid crystal panels.

Long life, low power consumption, and high-luminance light emission have led to widespread use in general lighting applications as a replacement for fluorescent and incandescent bulbs in recent years.

The inverter circuit used for lighting the CCFL is a DC-AC inverter that outputs a high-frequency, high-frequency AC voltage for driving the CCFL from a DC voltage.

FIG. 1 shows a circuit block diagram of a conventional CCFL DC-AC inverter. In FIG. 1, reference numeral 2 denotes a circuit unit that generates a DC power source from the AC power source 1. Reference numeral 3 denotes an oscillation circuit that operates by a DC voltage input from 2, and performs high-frequency oscillation operation with a transistor or the like. The output voltage of 3 is boosted by a transformer of 4, and a high-frequency high-frequency AC voltage necessary for driving the CCFL of 5 is supplied.

In the conventional DC-AC inverter operation, the frequency of the high-frequency AC voltage applied to the CCFL is set at 3 in FIG. 1 and the voltage value is determined by the transformer of 4, so that driving at a fixed frequency / voltage is the mainstream.

The CCFL tube current, that is, the luminance, is determined by the oscillation frequency and tube voltage of the fixed inverter.

However, the luminance characteristics of the CCFL vary greatly depending on the ambient temperature. FIG. 2 shows the relationship between the rise in CCFL brightness and the ambient temperature. Although the brightness immediately after lighting is low, it gradually becomes brighter when the tube is warmed up. The tube saturation temperature depends on the ambient temperature and saturates to a brightness proportional to the tube temperature.

FIG. 3 shows the optimum temperature characteristics of the CCFL. Whether the ambient temperature is high or low, the luminous efficiency tends to deteriorate and the luminance tends to decrease. The tube temperature of the CCFL has the same characteristics, and it is necessary to set the tube current so that the tube temperature is optimal for efficient lighting.

Problems to be solved by the invention

However, in the conventional fixed frequency oscillation DC-AC inverter, since the tube current is set regardless of the external environment such as temperature, the optimum operation in consideration of the ambient temperature cannot be performed.

In particular, in general lighting applications, many are used for downlights embedded in the ceiling, etc. If the heat dissipation is not done well and the CCFL heats up abnormally, the original life cannot be ensured and there is danger such as burning. Accidents may occur. Similarly, when exposed to cold, the luminance is lowered and the life of the CCFL is shortened.

The present invention solves the above-mentioned problem. After the CCFL is turned on, the saturation temperature of the tube is predicted, and the tube current is adjusted in advance so as to obtain an optimum tube temperature. The object is to provide CCFL lighting that ensures the above.

Means for solving the problem

In order to achieve this object, the present invention is characterized by predicting the saturation temperature of the tube from the constant interval time after the CCFL is turned on and the tube temperature at that time.

FIG. 4 shows a means for predicting the saturation temperature of the tube. The saturation temperature of the pipe is predicted by calculating the slope from the fixed interval time and the pipe temperature at that time. As shown in B of FIG. 4, the tube temperature and the ambient temperature are higher as the calculated gradient is higher than the optimum saturation temperature, and the ambient temperature is predicted to be lower as the gradient is smaller as shown in A.

In the tube temperature control method of the present invention, the tube current is determined in advance based on the predicted tube temperature. For this purpose, it has storage means for storing the tube current value for each optimum tube temperature, and means for measuring a certain interval time and detecting the tube temperature and the tube current at that time. Further, it has a control unit that compares the optimum tube temperature and tube current value with the current tube temperature and tube current value to determine the tube current.

Effect of the invention

According to the tube temperature control method of the present invention, it is possible to obtain a tube current suitable for the CCFL tube temperature, that is, luminance, so that it is possible to avoid lighting at a severe tube current for the CCFL tube.

In addition, since the ambient temperature, that is, the surrounding environment can be predicted from the CCFL tube temperature, lighting suitable for the environment where the CCFL lighting is installed can be performed, and unstable operation such as abnormal heat generation or temperature drop of the CCFL can be suppressed. Is possible.

Further, since the present invention is a prediction process, the CCFL lighting operation can be determined before the tube temperature is saturated.

The outline of the present invention will be described with reference to FIG. FIG. 5 is a circuit block diagram in the present invention.

FIG. 5 shows a conventional DC-AC inverter with a temperature detection function, a CCFL tube current detection function, and a program control unit for determining tube current.

Reference numeral 6 in FIG. 5 denotes a temperature sensor, which detects the temperature of the electrode portion having the highest temperature in the CCFL tube.

The CCFL tube current is detected by a current sensing resistor 7.

The program control unit 8 in FIG. 5 has a timer and a storage medium, and an optimum tube temperature and tube current are stored in association with each time table. Then, the set time is measured, and the stored tube temperature / tube current is compared with the detected tube temperature / tube current.

The program control unit gives an optimal frequency signal to the oscillation circuit based on the compared data, and the tube current changes as the oscillation circuit switches at the frequency.

FIG. 6 is a flowchart of two processes mainly performed by the program control unit, that is, comparison and tube current determination. The tube temperature and tube current detected at regular intervals are compared with the optimum tube temperature and tube current at that time, and the tube current is raised or lowered to approach the optimum tube temperature for CCFL. . This control is executed in a period until the tube temperature is saturated.

As described above, by controlling the tube current value supplied to the CCFL tube to change in accordance with the tube temperature, the optimum tube current can be selected before the tube temperature is saturated. In this way, the CCFL tube continues to saturate at the optimum tube temperature.

In addition, the optimum tube temperature and tube current corresponding to the time table differ depending on the type such as the length and thickness of the tube, so various types of CCFL tubes can be selected by selecting the optimum data for comparison according to the tube type. It can correspond to. In other words, it can be dealt with only by changing the program.

Circuit block diagram of conventional DC-AC inverter CCFL brightness rise and ambient temperature CCFL ambient temperature and luminance characteristics CCFL tube saturation prediction method showing means for implementing the present invention The circuit block diagram which shows embodiment of this invention The flowchart of the process which the program control part of this invention implements

DESCRIPTION OF SYMBOLS 1 ... AC power supply 2 ... Circuit part 3 which generates DC power supply ... Oscillation circuit 4 ... Transformer 5 ... Cold cathode tube (CCFL)
6 ... Temperature sensor 7 ... Current detection resistor 8 ... Program control unit

Claims (4)

In the CCFL tube temperature control method, a certain interval time is measured after lighting, the tube temperature and tube current at that time are detected, and compared with the optimum tube current value corresponding to the CCFL tube temperature, the optimum saturation temperature is obtained. How to control tube temperature by controlling tube current in advance. A tube temperature control method characterized in that the tube temperature control described above is performed before the tube temperature is saturated, and the saturation temperature of the tube is predicted by calculating a slope from a certain interval time and the tube temperature at that time. CCFL tube temperature control device, means for measuring time, temperature sensor for detecting tube temperature, means for detecting tube current, and means for storing optimum tube current value data corresponding to CCFL tube temperature And a tube temperature control device having a program control unit for controlling the tube current value so as to obtain an optimum tube temperature compared with the stored data. CCFL illumination with the tube temperature control device described above.

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