JPH10148808A - Backlight device and liquid crystal display device using the same - Google Patents

Abstract

(57) [Summary] In a backlight unit formed by a liquid crystal panel and a backlight, a backlight device that can secure stable backlight luminance without being affected by any use environment, and is inexpensive and has low power consumption. To achieve. SOLUTION: A pulse creating means for creating a backlight pulse, dimming means for modulating a pulse width of the backlight pulse to adjust backlight brightness, a reference voltage source for creating a reference voltage, and a backlight unit Temperature detecting means for detecting the surrounding temperature, period selecting means for setting a period for detecting the temperature by the temperature detecting means, and comparing means for comparing the detection result of the temperature detecting means with a voltage level of a reference voltage, The temperature around the display unit is detected over a period set by the period selection means, and the brightness of the backlight is adjusted according to the detected temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive non-luminous display panel, for example, a backlight device for a transmissive liquid crystal display device, and more particularly to a backlight in which the main body and the display unit are separately arranged. The present invention relates to a backlight device for realizing a backlight having a stable lighting property.

[0002]

2. Description of the Related Art In recent years, many liquid crystal display devices have been used in personal computers, televisions, and the like. However, since the liquid crystal display device is a non-light emitting type, image information of the liquid crystal display device cannot be visually recognized unless light is irradiated from behind the liquid crystal display device. In order to irradiate light from behind the liquid crystal display device, a backlight device using a fluorescent lamp, a cold cathode tube, or the like is required.

Here, as a backlight device, (1)
JP-A-5-135893 can be mentioned.

[0004]

The above-described backlight device corrects the backlight brightness only when the temperature falls below a certain temperature according to the temperature detected by the thermistor.

[0005] However, the use environment of the backlight device varies widely, and as described above, it is not possible to correct the use at a high temperature only by correcting only the low temperature side, and the temperature characteristics of the backlight tube itself. Not considered at all.

Further, there are problems such as an increase in power consumption due to continuous temperature detection and brightness control of the fluorescent lamp, and an increase in cost due to temperature control using a control IC. Was.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to firstly ensure that a stable luminance can always be ensured irrespective of the surrounding environment; It is an object of the present invention to realize a power-consuming backlight device with a simple configuration.

[0008]

According to a first aspect of the present invention, there is provided a backlight device having at least a backlight for irradiating a liquid crystal panel. The backlight driving circuit includes at least a pulse generation unit that generates a backlight pulse that is a signal for controlling the backlight driving circuit, and modulates a pulse width of the backlight pulse to adjust the brightness of the backlight. Dimming means, a reference voltage source for creating a reference voltage, a temperature sensor for detecting the temperature around the backlight, and a temperature detecting means including voltage converting means for converting the detection result of the temperature sensor to a voltage, A period selecting unit for setting a period for detecting the temperature by the temperature detecting unit; a detection result of the temperature detecting unit and a reference of the reference voltage source; And a voltage detector for detecting a temperature around the backlight over a period set by the period selector, and adjusting the brightness of the backlight according to the detected temperature. It is characterized by the following.

[0009] According to the above configuration, the use environment and condition desired by the user are various, and sometimes the use in the outdoors in winter, the use in a room with effective cooling, and the use in a high temperature greenhouse are conceivable. At low temperatures, the brightness decreases compared to normal temperature due to a decrease in the excitation ratio due to reduced electron emission capability inside the backlight tube and the temperature characteristics of the circuit that creates the backlight pulse. Therefore, the user cannot always visually recognize with a constant brightness. Therefore, by controlling the backlight pulse in accordance with the temperature detected by the temperature detecting means, the luminance desired by the user can be stably obtained regardless of the use environment, and a backlight device which can cope with any temperature condition can be realized. .

Furthermore, in an environment where the temperature change is small, the detected temperature does not change for the refresh cycle of the detection period, and the backlight brightness is not frequently controlled according to the ambient temperature. In other words, once the temperature is detected and the backlight pulse is controlled, it is sufficient even if the temperature is not detected for the time being and it is not necessary to constantly detect the temperature. If it can be set, the power consumed at the time of temperature detection can be suppressed to the minimum necessary.

According to the second aspect, the period selecting means includes:
At least the period signal output from the period selection unit is monitored by a detection control unit, and the temperature detection by the temperature detection unit is suspended during a non-selection period of the period signal.

According to the above arrangement, the detection control means monitors the period signal output from the period selection means, and suspends the temperature detection means during the non-detection period to make it in the non-detection state. During this time, the power consumed by the temperature detecting means can be suppressed.

According to the third aspect, the period selecting means includes:
At least an oscillation circuit, a counter for counting an oscillation clock output from the oscillation circuit, a decoder for decoding the output of the counter, and switching means for arbitrarily selecting the output of the decoder. According to the above-described configuration, the period selection unit can be configured with a simple circuit, so that power consumption can be reduced and a small-sized and low-cost backlight device can be realized. Further, the user can arbitrarily select a counter output that is a positive multiple of the clock output from the oscillation circuit, thereby easily selecting a detection period according to the use environment. In the case of use only at room temperature, setting the period selection signal to non-selection also leads to a reduction in power consumption.

According to a fourth aspect of the present invention, in the backlight device provided with a backlight for irradiating the liquid crystal panel, the backlight driving circuit for lighting the backlight is at least input from an image information source. Pulse generating means for generating a backlight pulse, which is a signal for controlling the backlight driving circuit by a horizontal synchronization signal, and dimming means for modulating the pulse width of the backlight pulse to adjust the brightness of the backlight; The backlight pulse output from the pulse generation means, and the self-oscillation means, which includes self-oscillation means for self-oscillation. The backlight is turned on by selecting one of the oscillation pulses by the determination unit. To.

According to the above configuration, in a conventional backlight device, particularly when the device body and the backlight device (display unit) are separately arranged, a backlight pulse is not input to the backlight at the same time when the power supply voltage is turned on. The backlight does not turn on. Therefore, even if there is no input of a backlight pulse, if the backlight is turned on by a self-oscillation pulse, the user can surely visually recognize the display, so that a safe and highly reliable backlight can be provided.

According to the fifth aspect, the dimming means and the self-oscillating means determine the initial pulse widths of the backlight pulse and the self-oscillating pulse generated at the same time when the power is turned on.
It has an initial setting means for setting and outputting the pulse width longer than the pulse width of the steady value.

According to the above configuration, the excited state of the interior of the backlight tube immediately after the power is turned on is unstable, and stable electron emission is not performed even at the discharge electrode portion. Therefore, by setting the pulse width of the backlight pulse applied immediately after turning on the power to be long (wide), the electron emission time becomes long,
A stable excited state can be maintained, and a stable discharge can be performed in a shorter time. Thereafter, if the pulse width can be arbitrarily set when the discharge becomes stable, power consumption can be reduced.

According to claim 6, the self-oscillation means includes:
The discriminating means for discriminating the presence or absence of the backlight pulse, when discriminating that the backlight pulse has been output from the pulse creating means, by the discriminating signal output from the discriminating means, from the self-oscillation means The output of the output self-oscillation pulse is stopped.

According to the above configuration, when the backlight pulse is generated by the pulse generating means, the self-oscillating means having exactly the same operation is unnecessary, so that the power consumed by the self-oscillating means is useless. Therefore, only when a backlight pulse is not output, a self-oscillation pulse can be generated only when necessary by operating the self-oscillation means, so that unnecessary power is not consumed.

According to a seventh aspect of the present invention, in the backlight device provided with a backlight for irradiating the liquid crystal panel, the backlight driving circuit for lighting the backlight controls at least the backlight driving circuit. Pulse creating means for creating a backlight pulse that is a signal to be adjusted, dimming means for adjusting the backlight brightness by modulating the pulse width of the backlight pulse, a reference voltage source for creating a reference voltage, Light detection means for detecting the amount of light emitted from the backlight, and comparison means for comparing the voltage level between the detection result of the light detection means and the reference voltage of the reference voltage source, the light emitted from the backlight. The pulse width of the backlight pulse is controlled by the dimming unit in accordance with the amount of light.

According to the above configuration, since the amount of light emitted from the backlight changes depending on the use environment and state of the backlight device, the elapsed time, and the like, it is necessary to make detailed settings in accordance with each condition. And the number of adjustment points may be increased. Therefore, if the amount of light emitted from the backlight in question is directly detected by the electric light cell and the result of the light amount detection is fed back to the circuit for controlling the pulse width of the backlight pulse, a complicated adjustment / control circuit is not required, and the circuit scale is reduced. Can be suppressed.

According to claim 8, the initial setting means includes:
At least a pulse generating means for generating a backlight pulse which is a signal for controlling the backlight driving circuit; a light controlling means for modulating a pulse width of the backlight pulse to control the backlight luminance; and a reference voltage. The reference voltage source, the light detection means for detecting the amount of light emitted from the backlight, and comparison means for comparing the detection result of the light detection means with a voltage level of the reference voltage of the reference voltage source. And a heater disposed between the liquid crystal panel and the backlight, and heater control means for controlling the temperature of the heater. The heater controls the temperature of the heater according to the amount of light emitted from the backlight. Is controlled by the heater control means to adjust the brightness of the backlight.

According to the above configuration, if the brightness of the backlight is adjusted by controlling the heater temperature in accordance with the amount of light emitted from the backlight, the temperature characteristics of the backlight tube itself and the elapsed time from when the power is turned on. Light control can be performed in consideration of time and the like. In addition, even at low temperatures where lighting conditions are relatively severe, warming with a heater closely attached to the backlight makes it possible to approach a stable lighting state at room temperature, and similarly in a liquid crystal panel where low temperature operation is unstable, A backlight device with improved display characteristics and excellent visibility can be provided.

According to a ninth aspect of the present invention, there is provided the liquid crystal display panel, a backlight for illuminating the liquid crystal display panel from the back, and a backlight driving circuit for turning on the backlight. A pulse generating means for generating a backlight pulse which is a signal for controlling at least the backlight driving circuit, a dimming means for modulating the pulse width of the backlight pulse to dimming the brightness of the backlight, A reference voltage source for generating a reference voltage, a temperature sensor for detecting a temperature around the backlight, and a temperature detecting unit including a voltage converting unit for converting a detection result of the temperature sensor into a voltage; A period selecting means for setting a period for detecting the temperature,
A comparison unit configured to compare a voltage level between a detection result of the temperature detection unit and a reference voltage of the reference voltage source;
The temperature around the backlight is detected over a period set by the period selection means, and the brightness of the backlight is dimmed according to the detected temperature.

According to the above configuration, by controlling the backlight pulse in accordance with the temperature detected by the temperature detecting means, a liquid crystal display device having a screen whose brightness desired by the user is stable regardless of the use environment can be provided. Obtainable.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIGS. 1 to 4 are diagrams for explaining a stable operation using a temperature detecting means in a backlight device according to a first embodiment of the present invention. FIG. FIG. 2 is a diagram showing characteristics, FIG. 2 is a block diagram of a unit for controlling backlight luminance according to an ambient temperature, FIG. 3 is a diagram illustrating a backlight dimming method, and FIG. 4 is a diagram illustrating a period selection unit. .

FIG. 1A shows an example of the temperature change of the backlight luminance, and the pulse width of the applied pulse (BLDOUT) input to the backlight during the ON period is constant. Here, the backlight luminance at −10 ° C. and 60 ° C. differs from the luminance at room temperature (25 ° C.) by about ± 70%. Therefore, if the pulse width of BLDOUT is modulated at room temperature as shown in FIG. Based on the backlight luminance at room temperature (pulse width: p = 10 μS, luminance: K = 3000 nit), the luminance is corrected according to the temperature as shown in FIG.

For example, when the ambient temperature of (a) is 0 ° C. or less,
If the pulse width of BLDOUT is set to p = 12 μS,
A brightness of 3000 nit, which is approximately 70% lower than the room temperature brightness (K = 5500 nit) of p = 12 μS, can be secured. Instead of controlling the relationship between the ambient temperature and the pulse width stepwise as in (a), the ambient temperature and the pulse width may be controlled to be inversely proportional as in (a).

FIG. 2 is a circuit block diagram illustrating a method for dimming the backlight brightness according to the ambient temperature as described above.

A temperature sensor (40) for detecting temperature,
Voltage conversion means (41) for converting the measurement result of the temperature sensor to a voltage level, and period selection means (42) for setting a period for detecting the ambient temperature with the temperature sensor (40),
Temperature detection means (44), which is constituted by detection control means for controlling a period during which the temperature sensor (40) detects the temperature by the period signal output from the period selection means (42), detects the temperature around the device. It is to be measured.

The detection result (Vo) of the temperature detecting means (44) and the reference voltage (Vref) generated by the reference voltage source (45) are inputted to the comparing means (46), respectively, and the voltages of Vo and Vref are inputted. The levels are compared by comparing means (46). The comparing means (46)
Is output to the dimming means (6) for performing processing for determining the luminance of the backlight (8), and the pulse during the ON period of the BLP (102) created by the pulse creating means (2) is output. BL that can achieve the backlight luminance desired by the user by either the pulse width modulation that modulates the width or the voltage modulation that modulates the applied voltage applied to the booster circuit (9)
After being modulated into a DOUT (104) signal, it is sent to a booster circuit (9) for lighting a backlight (8).

Referring to FIG. 3, the operation from the comparison means (46) to the light control means (6) will be described.

Vo output from the temperature detecting means (44) is:
The comparing means (46) compares the voltage levels of a plurality of (here, j = 4 bits) Vref1 to Vref4 created by the reference voltage source (45), and each comparison result Ho = H1
To H4 are output to the light control means (6). The dimming means (6) includes a decoder (50) and a digital SW (51),
A region to which the ambient temperature according to the voltage levels of H1 to H4 belongs is derived from k types, and a BLP (1
Set the pulse width of the ON period of 02). For example, when the ambient temperature is 0 ° C. or less, Ho (= H1, H) which sets the pulse width p = 12 μS in FIG.
2, H3, H4) = L, L, L, L are output. Also,
At 40 ° C. or higher, Ho = suppressing to p = 8 μS
By outputting H, H, H, and H, a constant backlight luminance can be always realized. Here, as the number of Vrefs generated by the reference voltage source (45) increases, more accurate detection is possible, and detection over a wide range is also possible depending on how the set temperature is selected.

FIG. 4 is a diagram for explaining the above-mentioned period selecting means. The oscillation pulse (A) output from the oscillation circuit (60) which is transmitting itself is counted by an n-bit counter (61). You. The n-bit signal (b) output from the counter (61) is converted into an m-bit signal (c) by the decoder (62), and the switching means (63) sets an arbitrary period signal (d). Output. Here, a counter (61) of n = 4,
An example will be described in which the decoder (62) of m = 16 selects and outputs (C6) of the decoder (62) output as the period signal (D).

According to the present embodiment, by controlling the backlight luminance in accordance with the temperature detected by the temperature detecting means, the luminance desired by the user can be stably obtained regardless of the use environment. A backlight device that can respond to temperature conditions can be realized.

Further, the user can arbitrarily set the detection period suitable for the use environment, so that the power consumed at the time of temperature detection can be suppressed to the minimum necessary. Power loss can be prevented by suspending the temperature detection means.

Further, since the period selecting means can be realized with a simple circuit configuration, it is possible to provide a backlight device which is reduced in power consumption, small in size, light in weight and low in cost.

(Second Embodiment) FIGS. 5 and 6 are views for explaining a backlight device according to a second embodiment of the present invention. FIG. 5 is a block diagram, and FIG. FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description is omitted.

In FIG. 5, a horizontal synchronizing signal (HSYNC) (101) output from the image information source (1) is a pulse generating means for generating a BLP (102) which is a signal for controlling a backlight driving circuit. Entered in (2). In the pulse generation means (2), the cycle (n) of n times of HSYNC (101)
= Integer) and BLP (10) synchronized with HSYNC (101)
2) is created. In the present embodiment, HSYNC (101)
Although the case where the BLP (102) is created is described, the BLP (102) may be created from another signal such as DXOUT which determines the horizontal writing position of the liquid crystal panel (7) as a display element. .

However, an image signal or an HSYNC signal which should be output from the image information source (1) at the same time when the power supply voltage is turned on.
When (101) is not input to the backlight drive circuit, the BLP (102) cannot be created by the pulse creating means (2), so that the backlight (8) cannot be turned on. Therefore, even when no image signal or HSYNC (101) is input from the image information source (1), the BLP (102) created by the pulse creating means (2) is used.
When the self-oscillation pulse (JHP) (103) which is exactly the same as that described above is created by the self-oscillation means (4) and applied to the booster circuit (9), the backlight (8) is turned on.

The BLP (10) created by the pulse creating means (2)
2) and the JHP (103) created by the self-oscillating means (4) are input to the discriminating means (4). In the determination means (5),
It is detected whether or not the BLP (102) has been input, and if the BL
When it is determined that P (102) has been input, BLP (102) is output to the light control means (6) as it is. At that time, self-oscillation means (4)
Since the output of the JHP (103) is not used at all, the result of the judgment by the judging means (5) is fed back to the self-oscillating means (4) to stop the output of the JHP (103). Power consumption by the self-oscillating means (4) during the operation can be suppressed. On the other hand, when the BLP (102) is not inputted, the JHP (103) is output to the dimming means (6) as a backlight pulse instead of the BLP (102).

In the light control means (6), the user controls the backlight.
After performing the modulation of the BLP (102) so that the luminance of (8) can be arbitrarily adjusted, it is output as a BLDOUT (104) to a booster circuit (9) for lighting a backlight.

The luminance of the backlight (8) immediately after the power supply voltage of the entire apparatus is turned on gradually increases with time as shown in FIG. This is the backlight
(8) The reason is that the ability of emitting electrons between the electrodes is poor because the electrodes themselves are not warm. Therefore, the pulse creation means
By providing the initial setting means (3) in both (2) and the self-oscillating means (4), the pulse width of the BLP (102) and JHP (103) immediately after turning on the power is widened (in the backlight (8) The electron emission period can be set long), stable discharge can be performed immediately after the power is turned on, and the backlight luminance desired by the user can be stably secured in a short time. In addition, backlight (8)
When the discharge is stabilized, the backlight can be adjusted to an arbitrary backlight luminance to provide a backlight device that is highly versatile and convenient.

FIG. 6 is a diagram for explaining the initial setting means (3).

In a differentiating circuit (20) composed of a resistor (R1), a capacitor (C1) and a diode (D1),
Immediately after the power is turned on, electric charge starts to be gradually stored in C1.
After a lapse of a time constant (τ1 = R1 * C1) determined by 1 and C1, C1 is fully charged. This differentiation circuit (20)
The differential signal (a) output from the inverter (2)
It is input to the PNP transistor (Tr1) which is reverse-shaped (1) in 1) and biased by the resistors (R2) and (R3). The emitter of Tr1 is directly connected to the power supply voltage (Vc
c) and the collector is likewise connected to Vcc via volume (VR1).

The signal (a) input to Tr1 immediately after the power is turned on is a High voltage, and the base-emitter voltage (V _BE ) of Tr1 cannot be ensured.
In this state, current does not flow between the emitter and the collector of Tr1. As a result, the current becomes Vcc → VR1 →
Is supplied to the multivibrator (22) through VR2,
BL is determined by a time constant (τ2 = (VR1 + VR2) * C2) determined by (VR1 + VR2) and the capacitor (C2).
The pulse width (pulse width) of the ON period of P (102) (c) is modulated and output to the booster circuit (9) as BLDOUT (104) (d).

On the other hand, the signal (a) after the elapse of τ1 becomes a low voltage, and conversely, Tr1 is turned on and VR
A current is supplied to the multivibrator (22) through the emitter → collector → VR2 without passing through the circuit. As a result, τ
After one elapse, the output of the multivibrator (22) is VR2 and C
BLDOUT (104) having a pulse width of a time constant (τ3 = VR2 * C2) determined by the step 2 is output. Here, since the pulse width of the multivibrator (22) can be set wider as the time constant becomes larger, the pulse width of τ2 becomes wider than that of τ3. 8) Discharge can be stably performed inside, and the backlight luminance can be stabilized in a short time and the luminance desired by the user immediately after the power is turned on can be realized.

According to the present embodiment, in a conventional backlight device, even when a backlight pulse is not input to the backlight drive circuit at the same time when the power supply voltage is turned on, the backlight is turned on by a self-oscillation pulse. Since the display can be surely visually recognized by the user, a safe and highly reliable backlight can be provided.

Further, by setting a longer ON period of the pulse width of the backlight pulse applied immediately after the power is turned on,
The time of electron emission becomes longer, and a stable excited state can be set in a short time. Thereafter, if the pulse width can be set arbitrarily when the discharge becomes stable, a backlight device with reduced power consumption and high convenience can be provided.

Since the initial setting means can be constituted by a simple circuit, it is possible to reduce the power consumption and to realize a compact, lightweight and low-cost backlight device.

Further, by feeding back the discrimination signal output from the discrimination means, which is a signal for controlling the self-oscillation means, to the self-oscillation means, a self-oscillation pulse can be generated only when necessary, and wasteful power is consumed. You don't have to.

(Third Embodiment) FIG. 7 illustrates a method for dimming the backlight luminance according to the amount of light emitted from a display unit in a backlight device according to a third embodiment of the present invention. (A) is a block diagram illustrating a dimming method, and (b) is a diagram illustrating a relationship between heater temperature and luminance. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description is omitted.

Liquid crystal panel when ambient temperature is low
Although the internal (liquid crystal) state of (7) depends on the type of liquid crystal, most liquid crystals change from a liquid crystal phase to a solid phase at around 0 ° C., and the movement of the liquid crystal molecules is hindered. Rather than suddenly becoming a solid, there is a semi-solid phase, an intermediate phase between the liquid crystal phase and the solid phase. Normally, this is the main reason that the operation guarantee temperature is approximately 0 ° C. when used as a display unit. However, since the environment actually used may be 0 ° C. or lower, it is necessary to take measures for guaranteeing low-temperature operation.

FIG. 7A shows an electric light cell (80) for detecting the amount of light emitted from the display unit, and voltage conversion means (81) for converting the measurement result of the electric light cell (80) into a voltage level. The output of the light detection means (82) constituted by
The reference voltage generated by the reference voltage source (45) is compared with the voltage level by the comparing means (46). The reference voltage generated by the reference voltage source (83) can always set the luminance desired by the user by setting at least one parameter. Comparison means
The output of (46) is input to the dimming means (6) for dimming the backlight luminance, and the BLP generated by the pulse generating means (2) for setting the backlight luminance desired by the user.
The modulation of (102) is performed and transferred to the booster circuit (9) for lighting the backlight (8).

A method for controlling the temperature of the heater (87) based on the amount of light output from the display unit to adjust the brightness of the backlight is performed by first using the output of the light detecting means (82) and the reference voltage source (45). The plurality of (q bits) reference voltages are compared by the comparing means (46). The comparison result of the comparing means (84) is input to a q-bit input-r-bit output decoder (83). The temperature of the heater (87) arranged between the liquid crystal panel (7) and the backlight (8) is controlled by the temperature controller (85) by the signal selected by the digital SW (84) from the r bits. The heater temperature is adjusted to achieve the desired brightness. As for the heater temperature controlled by the heater control means (86), the backlight brightness using the temperature characteristics of the backlight (8) can be dimmed, and the dimming can be performed over a wide range without being affected by the ambient temperature. it can. In this case, BL
The pulse width of the ON period of the DOUT (104) may be constant, and unless the backlight pulse has a pulse width in which flicker occurs or light emission efficiency is poor (power loss is large), the liquid crystal panel (7) is driven or an image information source is used. Since it is sufficient to use a simple and existing signal input from (1), it is possible to configure a simple circuit and reduce power consumption.

FIG. 7B shows luminance dimming by controlling the temperature of the heater 87. FIG. 7A shows the case where the detection result by the light detecting means 82 is 1500 nits lower than the set luminance. The temperature of the heater (87) is adjusted to, for example, 50 ° C. As a result, as shown in FIG. 1A, the ambient temperature can be set to approximately 5000 nit, which is the backlight luminance near approximately 50 ° C., and therefore, as described in the above-described first embodiment, the desired temperature of the user can be set. A backlight luminance (3000 nit) can be realized. On the other hand, (a) shows a case where the luminance and the heater temperature are set to be completely in inverse proportion.

According to the present embodiment, even when the amount of light emitted from the display unit changes due to the use environment, elapsed time, etc., the amount of light emitted from the display unit can be detected directly by the lightning cell. It is only necessary to feed back the result of the light amount detection to the circuit for controlling the pulse width, and a complicated adjustment / control circuit is not required, and the circuit scale can be reduced.

Further, by controlling the heater temperature in accordance with the amount of light emitted from the display unit and adjusting the brightness of the backlight, it is possible to adjust the temperature in consideration of the temperature characteristics of the backlight tube itself and the time elapsed since the power was turned on. Light is also possible.
The operation at low temperature where the lighting conditions are severe can be brought close to a stable lighting state at normal temperature by heating with a heater closely attached to the backlight. Similarly, even in a liquid crystal panel whose low-temperature operation is unstable, a backlight device with improved display characteristics and excellent visibility can be provided. A head mounted display (head mounted display: HMD) in which the backlight device is used by a user by enlarging and displaying an image displayed on, for example, a liquid crystal display panel using an optical component such as a lens.
Can be used. In the case of an HMD, a display unit having a backlight and a device for supplying an image signal are often provided separately, and the effect of using the present invention is high.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

2A and 2B are diagrams illustrating an initial setting unit according to the first embodiment of the present invention, wherein FIG. 2A is a circuit block diagram, and FIG. 2B is a timing chart.

3A and 3B are diagrams illustrating temperature characteristics of a backlight according to a second embodiment of the present invention, in which FIG. 3A illustrates a relationship between ambient temperature and luminance, and FIG. 3B illustrates a relationship between pulse width and luminance. ,
(C) is a diagram illustrating a relationship between a pulse width and an ambient temperature.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

5A and 5B are diagrams illustrating a dimming method according to a second embodiment of the present invention, wherein FIG. 5A is a circuit block diagram, and FIG. 5B is a diagram illustrating a relationship between ambient temperature and luminance.

FIGS. 6A and 6B are diagrams showing a period selecting means according to the second embodiment of the present invention, wherein FIG. 6A is a circuit block diagram, and FIG. 6B is a timing chart.

FIGS. 7A and 7B are block diagrams illustrating a method of dimming backlight luminance according to the amount of light emitted from a display unit according to a third embodiment of the present invention. FIG. 7A is a block diagram illustrating pulse width modulation, and FIG. () Is a block diagram illustrating heater control.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image information source 2 pulse creating means 3 initial setting means 4 self-oscillating means 5 discriminating means 6 dimming means 7 liquid crystal panel 8 backlight 9 boosting circuit 20 differentiating circuit 21 inverter 22 multivibrator 40 temperature sensor 41 voltage converting means 42 period detection Means 43 Detection control means 44 Temperature detection means 45 Reference voltage source 46 Comparison means 47 Heater control means 48 Heater 50 Decoder 51 Digital SW 60 Oscillation circuit 61 Counter 62 Decoder 63 Switching means 80 Lightning cell 81 Voltage conversion means 82 Light detection means 83 Decoder 84 Digital SW 85 Temperature control unit 86 Heater control means 87 Heater 101 HSYNC 102 BLP 103 JHP 104 BLDOUT

Claims (9)

[Claims] In a backlight device provided with a backlight for irradiating a liquid crystal panel, a backlight driving circuit for lighting the backlight is at least a signal for controlling the backlight driving circuit. Pulse generating means for generating a write pulse; dimming means for modulating the pulse width of the backlight pulse to adjust the brightness of the backlight; a reference voltage source for generating a reference voltage; Temperature detection means comprising a temperature sensor for detecting temperature and voltage conversion means for converting the detection result of the temperature sensor into a voltage, and a period selection means for setting a period for detecting the temperature by the temperature detection means,
A comparison unit configured to compare a voltage level between a detection result of the temperature detection unit and a reference voltage of the reference voltage source;
A backlight device, wherein the temperature around the backlight is detected over a period set by the period selection means, and the brightness of the backlight is adjusted according to the detected temperature. 2. The backlight device according to claim 1, wherein the period selection unit is configured to monitor at least the period signal output from the period selection unit by a detection control unit, and to detect the temperature by the temperature detection unit. The backlight is stopped during the non-selection period of the period signal. 3. The backlight device according to claim 1, wherein the period selection means includes at least an oscillation circuit,
A backlight device comprising: a counter for counting an oscillation clock output from the oscillation circuit; a decoder for decoding the output of the counter; and switching means for arbitrarily selecting an output of the decoder. . 4. A backlight device having a backlight for irradiating a liquid crystal panel, wherein a backlight drive circuit for lighting the backlight is at least a horizontal synchronization signal input from an image information source. Pulse generating means for generating a backlight pulse which is a signal for controlling a backlight driving circuit; dimming means for modulating a pulse width of the backlight pulse to adjust the luminance of the backlight; The backlight pulse output from the pulse generation means, or the self-oscillation pulse output from the self-oscillation means. A backlight, characterized in that one of them is selected by the discriminating means to turn on the backlight. apparatus. 5. The backlight device according to claim 4, wherein the dimming unit and the self-oscillation unit set the initial pulse widths of the backlight pulse and the self-oscillation pulse generated at the same time when power is turned on to a constant value. A backlight device comprising an initial setting means for setting and outputting a value longer than a pulse width of a value. 6. The backlight device according to claim 4, wherein the self-oscillation unit is configured such that the determination unit for determining the presence or absence of the backlight pulse outputs the backlight pulse from the pulse generation unit. When it is determined that the
A backlight device, wherein output of the self-oscillation pulse output from the self-oscillation unit is stopped. 7. A backlight device provided with a backlight for irradiating a liquid crystal panel, wherein the backlight driving circuit for lighting the backlight is at least a signal for controlling the backlight driving circuit. Pulse creating means for creating a write pulse, dimming means for adjusting the backlight brightness by modulating the pulse width of the backlight pulse, a reference voltage source for creating a reference voltage, and light emitted from the backlight. Light detecting means for detecting the amount of light emitted from the backlight, and a comparing means for comparing the detection result of the light detecting means with a voltage level of the reference voltage of the reference voltage source, and according to the amount of light emitted from the backlight, A backlight device, wherein a pulse width of the backlight pulse is controlled by the dimming unit. 8. The backlight device according to claim 8, wherein the initial setting unit includes at least a pulse generating unit that generates a backlight pulse that is a signal for controlling the backlight driving circuit, and the backlight pulse. Dimming means for modulating the pulse width of the backlight to adjust the brightness of the backlight; the reference voltage source for creating a reference voltage; and the light detection means for detecting the amount of light emitted from the backlight device; Comparing means for comparing the voltage level between the detection result of the light detecting means and the reference voltage of the reference voltage source; a heater disposed between the liquid crystal panel and the backlight; and a heater for controlling the temperature of the heater. It is constituted by heater control means, and controls the temperature of the heater by the heater control means according to the amount of light emitted from the backlight. A backlight device for adjusting the brightness of the backlight. 9. A liquid crystal display panel, a backlight for illuminating the liquid crystal display panel from the back, and a backlight driving circuit for turning on the backlight, wherein the backlight driving circuit includes at least the backlight. Pulse generating means for generating a backlight pulse which is a signal for controlling a light driving circuit; dimming means for modulating the pulse width of the backlight pulse to adjust the brightness of the backlight; and generating a reference voltage. A reference voltage source, a temperature sensor that detects the temperature around the backlight, and a temperature detection unit that includes a voltage conversion unit that converts a detection result of the temperature sensor into a voltage, and a period in which the temperature detection unit detects the temperature. Period setting means to be set, and comparing means for comparing the voltage level of the detection result of the temperature detecting means with the reference voltage of the reference voltage source Be more configuration over a set period of time by the period selection unit, a liquid crystal display device wherein the detecting the temperature around the backlight, and wherein the dimming the brightness of the backlight in accordance with the detection temperature.