JPH04115078U - lighting equipment - Google Patents

Abstract

(57) [Summary] [Purpose] The present invention is characterized in that outputs corresponding to the positive and negative peak voltages of the tube voltage of a discharge lamp can be detected with a small number of parts. [Structure] A voltage dividing circuit having a plurality of resistors 14, 15, 16, and 17 that alternately outputs divided voltages having opposite polarities and being equal to each other with respect to the tube voltage of a discharge lamp 13 lit by an AC power source 11. A pair of diodes 18 and 19 separately rectify the divided voltages outputted from the voltage dividing circuits and output the rectified voltages.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention relates to a lighting device used as a backlight for a liquid crystal display. It is something that

0002

[Conventional technology]

Recently, LCD TVs using liquid crystal displays have been widely used as small portable TVs. It is widespread.

0003 By the way, with this type of LCD TV, the screen can be viewed even in dark surroundings, such as indoors. In order to display clearly, a hot cathode tube is used as a substitute for a liquid crystal display. A lighting device incorporating discharge lamps as a backlight is installed.

0004 However, the discharge lamps used as backlights in such lighting devices are made of liquid. Compared to crystal displays, discharge lamps have a shorter lifespan, so if used for a long time, discharge lamps will deteriorate. , the display quality on the LCD screen may be significantly impaired.

[0005] Therefore, conventionally, as a way to know the deterioration of discharge lamps for backlights in advance, The idea is to monitor the tube voltage and detect deterioration from fluctuations in this tube voltage. . Figure 2 is for detecting the tube voltage of such a discharge lamp, and is connected to the AC power supply 1. A discharge lamp 3 is connected through a capacitor 2, and resistors 4 and 5 are connected in series to both ends of the discharge lamp 3. Connect the circuit and configure the half-wave rectifier circuit across the resistor 5 of this series circuit with the polarity shown. By connecting the output circuit of diode 6 and capacitor 7, the voltage according to the tube voltage of discharge lamp 3 is The divided voltage V1 is output to the connection point of resistors 4 and 5, and the voltage V1 at this connection point is output to the diode. It is half-wave rectified by the terminal 6, smoothed by the capacitor 7, and output from the output terminal t. The voltage VOUT is detected.

[0006] However, according to such a circuit, the tube voltage of the discharge lamp 3 becomes the indicated polarity and becomes a resistance. If the positive peak voltage is output at the connection point of resistors 4 and 5, half-wave rectification is performed using diode 6. The flowing output voltage VOUT can be detected, but the tube voltage of discharge lamp 3 has the opposite polarity as shown. When the negative peak voltage is output at the connection point of resistors 4 and 5, diode 6 blocked and cannot be detected.

[0007] This means that when a discharge lamp deteriorates, one side of the discharge lamp becomes polarized due to fluctuations in the tube voltage. Only the peak voltage on the negative side may become abnormally large, but if the negative peak voltage becomes large If this occurs, the circuit described above will not be able to detect the deterioration, making stable deterioration detection possible. It had the disadvantage that it could not be used.

[0008] Therefore, as shown in Figure 3, in which the same parts as in Figure 2 are given the same symbols, three discharge lamps are installed. A full-wave rectifier circuit is constructed across resistor 5 in a series circuit of resistors 4 and 5 connected to the ends. There is one in which the output circuit of a diode bridge 8 and a capacitor 9 are connected. According to such a circuit, the peak voltage at the connection point of the resistors 4 and 5 is on the positive side or the negative side. The output voltage VOUT can be detected from the output terminal t regardless of the output voltage.

[0009] However, in this way, a full-wave rectifier circuit consisting of a diode bridge 8 is used in the output circuit. The use of .

0010

[Problem that the idea aims to solve]

In this way, conventional products that use a half-wave rectifier circuit for the output circuit are not suitable for discharge lamps. If the peak voltage of only one polarity fluctuates abnormally due to deterioration, Stable deterioration detection cannot be expected, and the output circuit may not be detected. If a full-wave rectifier circuit was used, there was a problem in that it would be expensive.

[0011] This invention was developed in view of the above circumstances, and can be expected to provide stable deterioration detection. At the same time, we provide a lighting device that has a simple output circuit configuration and is inexpensive. The purpose is to

0012

[Means to solve the problem]

The lighting device of the present invention is designed to be mutually responsive to the tube voltage of a discharge lamp lit by an AC power source. A voltage divider circuit that has multiple resistors that alternately output divided voltages that are equal but opposite in polarity. The divided voltages output from this voltage dividing circuit are connected to a pair of dies in the output circuit. The configuration is such that each signal is rectified and output separately using an ode.

[0013]

[Effect]

As a result, according to the present invention, the polarity obtained from the voltage divider circuit for the tube voltage of the discharge lamp is Peak voltages on the positive and negative sides of the tube voltage based on divided voltages with opposite and equal polarities. It is possible to detect the output corresponding to each of the If the peak voltage of one polarity of the light becomes abnormally large, this can also be dealt with. Output can be detected.

[0014]

【Example】

An embodiment of the present invention will be described below with reference to the drawings.

[0015] FIG. 1 shows the circuit configuration of the same embodiment. In the figure, 11 is an AC power supply, This AC power supply 11 uses an inverter. Then, to this AC power supply 11 A discharge lamp 13 is connected via a DC cut capacitor 12. This discharge lamp 13 is used as a backlight for a liquid crystal display (not shown). A hot cathode tube is used here.

[0016] A series circuit of resistors 14, 15, 16, and 17 is connected to both ends of the discharge lamp 13. this In this case, resistors 14 and 17 and resistors 15 and 16 have the same resistance value. It is.

[0017] Then connect the connection point of resistors 14 and 15 and the connection point of resistors 16 and 17 to the illustrated poles, respectively. diodes 18 and 19, and connect this common connection point to the output terminal t. At the same time, a smoothing capacitor is connected between the output terminal t and the connection point of the resistors 14 and 15. A capacitor 20 is connected to form an output circuit. In this case, the resistors 14 and 15 The connection point is grounded. Next, the operation of the embodiment configured as above will be explained.

[0018] Now, when AC power is supplied from the AC power supply 11 to the discharge lamp 13, the discharge lamp 13 It will be lit. In this state, now set the tube voltage of the discharge lamp 13 to VAB, and set the tube voltage of the discharge lamp 13 to VAB. If the tube current flows from point A to point B, the divided voltage V at the connection point between resistors 14 and 15 C is VC = R2 / (R1 + R2 + R3 + R4)・VAB (However, R1 is a resistor of 14, R2 is a resistor of 15, R3 is a resistor of 16, and R4 is a resistor of 1. The resistance value is 7. ) Similarly, the divided voltage VD at the connection point with the resistor 16 is VD = -R3 / (R1 +R2 +R3 +R4)・VAB becomes. Since R2 = R3 here, VC = -VD is obtained.

[0019] As a result, the divided voltage VC at the connection point between resistors 14 and 15 is increased by the diode 18. It is half-wave rectified and smoothed by a capacitor 20, and the output voltage is output from the output terminal t. Detected as VOUT. Next, when the tube current of the discharge lamp 13 starts to flow from point B to point A, the above two According to the formula, -VC =VD is obtained.

[0020] As a result, the divided voltage VD at the connection point between resistors 16 and 17 is now It is half-wave rectified by 9 and smoothed by capacitor 20, and from the output terminal t. Detected as output voltage VOUT.

[0021] Therefore, in this way, the discharge lamp 13 can emit light regardless of the direction in which the tube current flows. The output voltage VOUT corresponding to the positive and negative peak voltages of the tube voltage of the lamp 13 is then Therefore, if the discharge lamp 13 deteriorates, the discharge lamp 13 Even if the peak voltage on one polarity side of Now that the output voltage VOUT can be detected, we hope to be able to stably detect the deterioration of the discharge lamp 13. can do. In addition, the output circuit consists of two diodes and a capacitor. The configuration is simple, the number of parts can be minimized, and the price can be reduced. .

[0022] The present invention is not limited to the above embodiments, and may be modified as appropriate without changing the gist. It can be shaped and implemented. For example, in the embodiment described above, a hot cathode tube is used as a discharge lamp. However, it is also possible to use cold cathode tubes. In addition, the lighting device of this invention , not only for LCD TVs, but also for LCD displays such as word processors and computers. can also be applied.

[0023]

[Effect of the idea]

According to the lighting device of the present invention, with respect to the tube voltage of a discharge lamp lit by an AC power source, A resistor that has multiple resistors that alternately output equal divided voltages with opposite polarities. A voltage circuit is provided, and the divided voltages output from the voltage divider circuits are connected to a pair of output circuits. Since each diode is used to rectify and output separately, the tube voltage of the discharge lamp can be reduced. Since the output corresponding to the positive and negative peak voltages can also be detected, it is possible to In addition, due to deterioration of the discharge lamp, only the peak voltage of one polarity becomes abnormally large. Even in such cases, the corresponding output can be detected and stable discharge lamp deterioration can be achieved. We can expect detection. In addition, the output circuit consists of two diodes and a capacitor. The configuration is simple, the number of parts can be minimized, and the price can be reduced. .

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram showing an example of a conventional lighting device.

FIG. 3 is a circuit configuration diagram showing a different example of a conventional lighting device.

[Explanation of symbols]

11... AC power supply, 12, 20... Capacitor, 13... Discharge lamp, 14, 15, 16, 17... Resistor, 18, 19... Diode.

Claims (1)

[Scope of utility model registration request] 1. A discharge lamp that is lit by an AC power source; a voltage divider circuit having a plurality of resistors that alternately output divided voltages that are equal and opposite in polarity to the tube voltage of the discharge lamp; 1. A lighting device comprising: an output circuit having a pair of diodes that separately rectify and output divided voltages output from the voltage divider circuits.