JP2001169273A - Color video intercom device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color video intercom device usable in a state such that a screen is bright and easy to see at all times by stably controlling the luminance of a cold cathode type fluorescent lamp immediately after activation. SOLUTION: This color video intercom device is provided with a color liquid crystal panel and a backlight composed of a cold cathode type fluorescent lamp 3 for illuminating the color liquid crystal panel from a back surface side. A lamp current control circuit 13 for controlling a current value flowing to the cold cathode type fluorescent lamp 3 is provided so as to make the cold cathode type fluorescent lamp 3 emit light to yield sufficient luminance in the activation. The lamp current control circuit 13 controls the current value flowing to the cold cathode type fluorescent lamp 3 on the basis of input from an ambient temperature detection circuit 10, a timer circuit 11 and a lamp temperature detection circuit 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color television door phone apparatus comprising a color liquid crystal panel and a backlight comprising a cold cathode fluorescent lamp for illuminating the color liquid crystal panel from the back side.

[0002]

2. Description of the Related Art In recent years, television doorphones capable of visually recognizing visitors have been rapidly spreading in place of audio-only intercoms. Most of the television doorphones currently in wide use are black and white image types, but recently, color image type TV doorphones have also begun to spread gradually.

In the case of a black and white image type, a self-luminous flat CRT is used as a display means in such a TV door phone. In the case of a color image type television doorphone, a liquid crystal panel is used in order to have a thin shape in addition to a flat cathode ray tube.

A liquid crystal panel used in a color image type television door phone does not emit light by itself, and is generally provided with a backlight for illuminating the liquid crystal panel from the back side. In the backlight, a rod-shaped cold cathode fluorescent lamp is used as a light emitting means, and a surface light is emitted using a reflection plate, a diffusion plate, or the like.

By the way, the cold cathode fluorescent lamp, which is the light emitting means of the backlight, has a low self-heating temperature immediately after the start of lighting, so that the mercury vapor pressure in the tube is low and the brightness is low. Then, as the time elapses from the start of lighting, the tube temperature gradually rises and gradually becomes brighter. Further, the saturation temperature of the tube differs depending on the ambient temperature of the cold cathode fluorescent lamp, and finally, the brightness settles in proportion to the tube temperature.

[0006] In the case of a TV door phone, the backlight is turned on only when there is a visitor, so the TV door phone must be used immediately after the backlight starts to be turned on. For this reason, there is a problem that the TV door phone is used in a dark state in which the brightness of the backlight is low. In this regard, since a liquid crystal television or the like is originally used for a long time, a decrease in luminance immediately after the start of turning on the backlight is not a problem.

Further, the cold cathode fluorescent lamp has a temperature peak of the lamp brightness of 40 to 45 ° C., and the mercury vapor pressure in the lamp is greatly reduced on the low temperature side, and the ultraviolet output is reduced. There was also the problem of lowering.

That is, when the indoor temperature decreases in the morning or at night in winter in a cold region, the brightness of the backlight decreases, and the TV door phone becomes difficult to see.

On the other hand, on the high temperature side, the mercury vapor pressure in the lamp increases and the luminous efficiency deteriorates. However, when a cold-cathode fluorescent lamp is used as a backlight of a TV door phone, the TV door phone is used indoors.
There is no problem about a decrease in the brightness of the backlight at a high temperature of 5 ° C. or higher.

Therefore, due to the characteristics of the cold cathode fluorescent lamp described above, in order to use the TV door phone with a bright and easy-to-view screen, it is necessary to make some corrections for the brightness decrease immediately after the backlight is turned on and at low temperatures. is there.

Conventionally, in a liquid crystal display module using a cold-cathode fluorescent lamp as a backlight, a method for improving a decrease in luminance at startup and at low temperatures has been proposed.
A control method for changing the oscillation frequency of the cold cathode fluorescent lamp, a control method in which a heater is provided near the cold cathode fluorescent lamp and heating is performed, and the like are known.

An outline of such a conventional TV door phone will be described with reference to FIGS. FIG. 3 is a block diagram showing a schematic configuration of a TV door phone according to a first conventional example, and FIG. 4 is a block diagram showing a schematic configuration of a TV door phone according to a second conventional example.

The television doorphone according to the first conventional example adopts a control method for changing the oscillation frequency of a cold cathode fluorescent lamp as disclosed in Japanese Patent Application Laid-Open No. 9-102397, for example. The television doorphone according to the second conventional example adopts a control method in which a heater is provided in the vicinity of a cold cathode fluorescent lamp and heated as shown in Japanese Patent Publication No. 7-18994, for example. It is.

As shown in FIG. 3, a cold cathode fluorescent lamp 3 (referred to as a lamp in the figure) of a TV door phone according to a first conventional example is connected to an oscillation circuit 1 via a booster circuit 2. The light is turned on based on a predetermined oscillation frequency generated by the oscillation circuit 1.

A temperature sensor circuit 4 for detecting the ambient temperature of the cold cathode fluorescent lamp 3 is provided. The temperature sensor circuit 4 controls the oscillation frequency of the oscillation circuit 1 for controlling the oscillation frequency. It is connected to the circuit 5. In a normal case, the higher the oscillation frequency, the brighter the cold cathode fluorescent lamp 3 becomes.

In the TV doorphone having such a configuration, when the ambient temperature of the cold cathode fluorescent lamp 3 detected by the temperature sensor circuit 4 is lower than a predetermined value, the oscillation frequency control circuit 5 causes the oscillation circuit 1 to operate. Control is performed so that the oscillation frequency becomes higher than the stable lighting state. This allows
The cold cathode fluorescent lamp 3 can emit light with the same brightness as in the stable lighting state. On the other hand, when the ambient temperature of the cold-cathode fluorescent lamp 3 detected by the temperature sensor circuit 4 is higher than a predetermined value, the oscillation frequency of the oscillation circuit 1 is reduced by the oscillation frequency control circuit 5 to achieve a stable lighting state. Such control is performed.

In the television door phone shown in FIG. 3, the value of the current flowing through the cold cathode fluorescent lamp 3 is determined by the magnitude of the capacitance of the capacitor 6.

As shown in FIG. 4, a cold cathode fluorescent lamp 3 (referred to as a lamp in the figure) of a video door phone according to a second conventional example is connected to an oscillation circuit 1 via a booster circuit 2. The light is turned on based on a predetermined oscillation frequency generated by the oscillation circuit 1. At the same time, an ambient temperature detecting circuit 7 for detecting an ambient temperature of the cold cathode fluorescent lamp 3 is provided. The ambient temperature detecting circuit 7 is connected to the cold cathode fluorescent lamp 3 via a heater driving circuit 8. Heater 9 provided in the vicinity of
It is connected to the.

In the TV door phone having such a configuration, when the ambient temperature of the cold cathode fluorescent lamp 3 detected by the ambient temperature detecting circuit 7 is lower than a predetermined value, the heater 9 is driven by the heater driving circuit 8. Then, the cold cathode fluorescent lamp 3 is heated. Thereby, the cold cathode fluorescent lamp 3
Can emit light with the same brightness as in the stable lighting state.

On the other hand, when the ambient temperature of the cold cathode fluorescent lamp 3 detected by the ambient temperature detecting circuit 7 is higher than a predetermined value, heating by the heater 9 is not performed. In the TV door phone shown in FIG. 4, the value of the current flowing through the cold cathode fluorescent lamp 3 is determined by the magnitude of the capacitance of the capacitor 6.

[0021]

As described above, in a conventional TV door phone, a control method for changing the oscillation frequency of a cold-cathode fluorescent lamp or a cold-cathode fluorescent lamp is used in order to improve the brightness reduction at the time of startup and at low temperatures. A control method or the like in which a heater is provided near the cathode-type fluorescent lamp to heat it is adopted.

However, there is room for further improvement in order to use the TV doorphone with the screen always bright and easy to see by stably controlling the brightness of the cold cathode fluorescent lamp immediately after startup.

When a control method is used in which a heater is provided near the cold cathode fluorescent lamp to heat the heater, heat from the heater reaches the liquid crystal panel, and the liquid crystal panel may be deteriorated. .

The present invention has been proposed in view of the above-described circumstances. By controlling the luminance of a cold cathode fluorescent lamp stably immediately after startup, it is possible to always use the cold cathode fluorescent lamp in a state where the screen is bright and easy to see. An object of the present invention is to provide a color television door phone device.

[0025]

SUMMARY OF THE INVENTION A color television door phone apparatus according to the present invention has the following features in order to achieve the above object.

That is, the color television door phone apparatus according to the present invention is a color television door phone apparatus comprising a color liquid crystal panel and a backlight comprising a cold cathode fluorescent lamp for illuminating the color liquid crystal panel from the back side. At the time of startup, the cold cathode fluorescent lamp is provided with current control means for controlling a current value flowing through the cold cathode fluorescent lamp so as to emit light with a predetermined luminance.

More specifically, a control signal for increasing a current value flowing through the cold cathode fluorescent lamp to the current control means for a predetermined time after the start corresponding to the starting characteristic of the cold cathode fluorescent lamp. Is provided, the cold cathode fluorescent lamp can emit light at a predetermined luminance.

The temperature of the cold-cathode fluorescent lamp is detected, and when the detected temperature of the cold-cathode fluorescent lamp is equal to or lower than a predetermined value, the current control means is supplied to the cold-cathode fluorescent lamp. The provision of the lamp temperature detecting means for transmitting a control signal for increasing the current value flowing through the lamp allows the cold cathode fluorescent lamp to emit light at a predetermined luminance.

Further, the ambient temperature of the cold-cathode fluorescent lamp is detected, and based on the detected ambient temperature of the cold-cathode fluorescent lamp, the current is supplied to the cold-cathode fluorescent lamp with respect to the current control means. The provision of the ambient temperature detecting means for transmitting a control signal for increasing / decreasing the current value enables the cold cathode fluorescent lamp to emit light at a predetermined luminance.

Here, the ambient temperature detecting means can include a diode. In this case, the current control means controls the value of the current flowing through the cold-cathode fluorescent lamp based on the temperature characteristics of the forward voltage of the diode, so that the cold-cathode fluorescent lamp emits light at a predetermined luminance. It is possible to do.

Further, the ambient temperature detecting means can include a thermistor. In this case, the current control means controls the current value flowing through the cold-cathode fluorescent lamp based on the ambient temperature of the cold-cathode fluorescent lamp detected by the thermistor, thereby controlling the cold-cathode fluorescent lamp. It is possible to emit light at a predetermined luminance.

Further, the current control means may include a variable capacitance diode connected in series to the cold cathode fluorescent lamp. In this case, by varying the external DC voltage applied to the variable capacitance diode, the current value flowing through the cold cathode fluorescent lamp is controlled,
The cold cathode fluorescent lamp can emit light at a predetermined luminance.

By the way, the brightness of the cold cathode fluorescent lamp is as follows.
It increases and decreases in proportion to the flowing current value (however, if the current value flowing through the cold cathode fluorescent lamp exceeds 50% of a predetermined value, the proportional relationship is not established). Therefore, with the above-described configuration, the current value flowing through the cold-cathode fluorescent lamp at the time of startup is controlled so as to increase, and the current value flowing through the cold-cathode fluorescent lamp is taken into consideration with the passage of time in consideration of the time characteristics. By reducing the number, it is possible to use the color television door phone apparatus in a state where the screen is bright and easy to see immediately after the startup.

Further, by controlling the value of the current flowing through the cold-cathode fluorescent lamp based on the change in the ambient temperature of the cold-cathode fluorescent lamp, the color television door phone apparatus can be used in a state where the screen is bright and easy to see immediately after startup. be able to.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a color television door phone according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a color television doorphone device according to the present invention, and FIG. 2 is an explanatory diagram showing a circuit configuration of the color television doorphone device shown in FIG. Note that members having the same functions as those of the above-described conventional TV doorphone are denoted by the same reference numerals and described.

As shown in FIG. 1, a cold cathode fluorescent lamp 3 (referred to as a lamp in the figure) of a color television door phone apparatus according to the present invention is connected to an oscillation circuit 1 via a boosting circuit 2. Lights up based on a predetermined oscillation frequency generated by the oscillation circuit 1.

Further, a lamp current control circuit 13 for controlling a current value flowing through the cold cathode fluorescent lamp 3 is connected to the cold cathode fluorescent lamp 3. Further, an ambient temperature detection circuit 10, a timer circuit 11, and a lamp temperature detection circuit 12 are connected to the lamp current control circuit 13.

The lamp current control circuit 13 is a circuit functioning as a current control means. By controlling the value of the current flowing through the cold cathode fluorescent lamp 3, the brightness of the cold cathode fluorescent lamp 3 can be adjusted. . In a normal case, when the current value flowing through the cold cathode fluorescent lamp 3 increases, the cold cathode fluorescent lamp 3 becomes bright.

The ambient temperature detecting circuit 10 is a circuit functioning as an ambient temperature detecting means. Based on the detected ambient temperature of the cold cathode fluorescent lamp 3, the lamp current control circuit 13
In response, a control signal for increasing or decreasing the current value flowing through the cold cathode fluorescent lamp 3 is transmitted. Upon receiving the control signal, the lamp current control circuit 13 adjusts the value of the current flowing through the cold cathode fluorescent lamp 3 to emit light with the same brightness as in the stable lighting state.

That is, the detected cold cathode fluorescent lamp 3
If the ambient temperature of the cold cathode fluorescent lamp is lower than a predetermined value, a control signal for increasing the value of the current flowing through the cold cathode fluorescent lamp 3 is sent to the lamp current control circuit 13, and conversely, the detected cold cathode fluorescent lamp When the ambient temperature of the lamp 3 is higher than a predetermined value, a control signal for reducing the value of the current flowing through the cold cathode fluorescent lamp 3 is sent to the lamp current control circuit 13 so that the cold cathode fluorescent lamp The brightness of No. 3 is constant.

The timer circuit 11 is a circuit functioning as time control means. The lamp current control circuit 1 operates only for a predetermined time after starting according to the starting characteristics of the cold cathode fluorescent lamp 3.
A control signal for increasing the value of the current flowing through the cold cathode fluorescent lamp 3 is transmitted to the fluorescent lamp 3. Upon receiving the control signal, the lamp current control circuit 13 increases the value of the current flowing through the cold cathode fluorescent lamp 3 to emit light with the same brightness as in the stable lighting state.

On the other hand, when a predetermined time has elapsed after the start, the above signal is not transmitted, and the current value in the stable lighting state for the cold cathode fluorescent lamp 3 is controlled by the lamp current control circuit 13 under the control of the lamp current control circuit 13. Shed.

The lamp temperature detecting circuit 12 is a circuit functioning as a lamp temperature detecting means. When the detected temperature of the cold cathode fluorescent lamp 3 is equal to or lower than a predetermined value, the lamp temperature control circuit 13 supplies a cold current to the lamp current control circuit 13. A control signal for increasing the value of the current flowing through the cathode fluorescent lamp 3 is transmitted. Upon receiving the control signal, the lamp current control circuit 13 increases the value of the current flowing through the cold cathode fluorescent lamp 3 to emit light with the same brightness as in the stable lighting state.

On the other hand, if the detected temperature of the cold cathode fluorescent lamp 3 is equal to or higher than the predetermined value, the above signal is not transmitted, and the cold cathode fluorescent lamp 3 is controlled by the lamp current control circuit 13. To flow a current value in a stable lighting state.

In the above-described embodiment, the ambient temperature detection circuit 10, the timer circuit 11, and the lamp temperature detection circuit 12 are connected to the lamp current control circuit 13, but not all of them. The circuits need not be connected, and it is sufficient that at least one or more of these circuits be connected.

In particular, in order to improve the starting characteristics, substantially the same effect can be obtained with either the timer circuit 11 or the lamp temperature detecting circuit 12.

Next, the circuit configurations of the lamp current control circuit 13 and the ambient temperature detection circuit 10 will be described in more detail with reference to FIG.

As shown in FIG. 2, the lamp current control circuit 1
3 and the ambient temperature detection circuit 10 include an operational amplifier 14,
It comprises resistors R1 to R7, a capacitor C1, a variable capacitance diode D1, and a diode D2.

The input side of the operational amplifier 14 is connected to a power supply Vcc, one of a timer circuit 11 and a lamp temperature detection circuit 12, and an ambient temperature detection circuit 10 including a diode D2. Note that the ambient temperature detection circuit 10 may include a thermistor 15.

The output side of the operational amplifier 14 is connected to a cold-cathode fluorescent lamp 3 (denoted as a lamp in the figure). 1 connected. The operational amplifier 14 is
The gain is set based on the ratio R2 / R1 of the resistors R2 and R1.

In the lamp current control circuit 13 having such a circuit configuration, when the output voltage of the operational amplifier 14 decreases, the capacitance of the variable capacitance diode D1 connected in series to the cold cathode fluorescent lamp 3 increases. Therefore, the capacitance including the capacitor C1 connected in series to the cold cathode fluorescent lamp 3 increases, the current value flowing through the cold cathode fluorescent lamp 3 increases, and the cold cathode fluorescent lamp 3 becomes bright.

That is, when the ambient temperature of the cold-cathode fluorescent lamp 3 decreases, the forward voltage of the diode D2 constituting the ambient temperature detecting circuit 10 increases, and the output voltage of the operational amplifier 14 decreases to reduce the cold-cathode fluorescent lamp 3. It operates in a direction to increase the value of the current flowing through the lamp 3. Thus, the brightness of the cold cathode fluorescent lamp 3 is maintained at the same level as in the stable operation.

On the other hand, when the ambient temperature of the cold cathode fluorescent lamp 3 rises, the forward voltage of the diode D2 constituting the ambient temperature detecting circuit 10 decreases, and the output voltage of the operational amplifier 14 increases, and It operates in a direction to reduce the value of the current flowing through the lamp 3. Thus, the brightness of the cold cathode fluorescent lamp 3 is maintained at the same level as in the stable operation.

The resistance of the thermistor 15 constituting the ambient temperature detecting circuit 10 increases as the ambient temperature decreases, and the same effect as that of the diode D2 can be obtained.

The timer circuit 11 outputs an L signal (Low signal) for a certain period of time from when the power is turned on.
As a result, the resistor R5 is short-circuited, the output voltage of the arithmetic intensifier 14 decreases, and the current value flowing through the cold cathode fluorescent lamp 3 increases. Therefore, the brightness of the cold cathode fluorescent lamp 3 is maintained at the same level as in the stable operation.

Similarly, from the lamp temperature detection circuit 12,
The L signal (L) is output until the cold cathode fluorescent lamp 3 reaches a predetermined temperature.
ow signal) is output. As a result, the resistor R5 is short-circuited, the output voltage of the arithmetic intensifier 14 decreases, and the current value flowing through the cold cathode fluorescent lamp 3 increases. Therefore, the brightness of the cold cathode fluorescent lamp 3 is maintained at the same level as in the stable operation.

[0058]

Since the color television door phone apparatus according to the present invention has the above-described configuration, the following effects can be obtained. That is, in the color television doorphone device according to the present invention, at the time of startup, the current value flowing through the cold-cathode fluorescent lamp is increased by using the current control means for a predetermined time or until the cold-cathode fluorescent lamp reaches a predetermined temperature. This makes it possible to maintain the brightness of the cold cathode fluorescent lamp in the same manner as in the stable operation, and to use the color television doorphone device in a state where the screen is always bright and easy to see.

Further, by controlling the value of the current flowing through the cold cathode fluorescent lamp based on the temperature characteristics of the forward voltage of the diode using the ambient temperature detecting means including the diode, The brightness of the cold cathode fluorescent lamp can be maintained in the same manner as in the stable operation, even when the ambient temperature of the fluorescent lamp changes, so that the color TV door phone can be used with the screen always bright and easy to see. .

The same effect can be obtained by controlling the value of the current flowing through the cold cathode fluorescent lamp using ambient temperature detecting means including a thermistor with respect to the change in the ambient temperature of the cold cathode fluorescent lamp. Can play.

Further, by configuring the current control means including a variable capacitance diode connected in series to the cold cathode fluorescent lamp, the external DC voltage applied to the variable capacitance diode can be varied, and Of the cold cathode fluorescent lamp can be very easily improved in the starting characteristics and the ambient temperature characteristics.

[0062]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a color television door phone apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a detailed circuit configuration example of the color television door phone apparatus shown in FIG. 1;

FIG. 3 is a block diagram showing a schematic configuration of a TV door phone according to a first conventional example.

FIG. 4 is a block diagram showing a schematic configuration of a TV door phone according to a second conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oscillation circuit 2 Booster circuit 3 Cold cathode fluorescent lamp 4 Temperature sensor circuit 5 Oscillation frequency control circuit 6 Capacitor 7 Ambient temperature detection circuit 8 Heater drive circuit 9 Heater 10 Ambient temperature detection circuit 11 Timer circuit 12 Lamp temperature detection circuit 13 Lamp current Control circuit 14 Operational amplifier 15 Thermistor R1 to R7 Resistance C1 Capacitor D1 Variable capacitance diode D2 Diode Vcc Power supply

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 9/30 H04N 9/30 5G435 F term (Reference) 2H088 EA22 EA68 HA06 HA28 MA06 2H093 NC42 NC57 NC76 ND02 ND08 5C006 AA01 AA22 AF62 AF67 BB29 BF25 BF29 BF36 BF37 BF38 BF46 EA01 EC08 FA21 5C054 FA02 FB04 HA22 5C060 BA04 BA09 DB00 HA00 HA05 HA07 HA10 HA14 HD03 JA00 JB00 5G435 AA00 AA01 BB12 BB15 CC12 EE25 EE30

Claims (7)

[Claims] 1. A color television door phone apparatus comprising: a color liquid crystal panel; and a backlight comprising a cold cathode fluorescent lamp for illuminating the color liquid crystal panel from the back side. A color television door phone device comprising: current control means for controlling a current value flowing through the cold cathode fluorescent lamp so as to emit light at a predetermined luminance. 2. A control signal for increasing a current value flowing through the cold-cathode fluorescent lamp to the current control means for a predetermined time after the start corresponding to the starting characteristic of the cold-cathode fluorescent lamp. 2. The color television intercom apparatus according to claim 1, further comprising a time control unit for controlling the time. And detecting the temperature of the cold-cathode fluorescent lamp and, when the detected temperature of the cold-cathode fluorescent lamp is equal to or lower than a predetermined value,
3. The color television doorphone device according to claim 1, further comprising a lamp temperature detecting unit for transmitting a control signal for increasing a current value flowing through the cold cathode fluorescent lamp. 4. An ambient temperature of the cold-cathode fluorescent lamp is detected, and based on the detected ambient temperature of the cold-cathode fluorescent lamp, a current flows to the cold-cathode fluorescent lamp with respect to the current control means. The color television doorphone device according to any one of claims 1 to 3, further comprising an ambient temperature detecting means for transmitting a control signal for increasing or decreasing the current value. 5. The ambient temperature detecting means includes a diode, and the current control means controls a current value flowing through the cold cathode fluorescent lamp based on a temperature characteristic of a forward voltage of the diode. The color television door phone device according to claim 4, wherein 6. The cold-cathode fluorescent lamp based on the ambient temperature of the cold-cathode fluorescent lamp detected by the thermistor, wherein the current control means includes a thermistor. 5. The color television door phone device according to claim 4, wherein 7. The cold cathode fluorescent lamp according to claim 7, wherein said current control means includes a variable capacitance diode connected in series to said cold cathode fluorescent lamp, and varies an external DC voltage applied to said variable capacitance diode. The color television intercom apparatus according to any one of claims 1 to 6, wherein a value of a current flowing through the door is controlled.