JPH03176227A - Display brightness controller - Google Patents

Abstract

PURPOSE:To change the brightness of a display device smoothly based on the brightness of circumference by changing-over the sensitiveness of a circuit which detects solar radiation sensor output, and changing-over automatically the sensitiveness based on input light quantity. CONSTITUTION:Two pull-up resistors Rp1, Rp2 which change-over the sensitiveness of a solar radiation sensor 3 are installed. This selective changing-over is performed by an analog switch 18 according to an instruction from a microcomputer 13. The pull-up resistor Rp1 is set at such a value as input voltage may not be saturated up to about 1.5 - 2.0 times as much as an incidence light quantity at the time of shining. On the other hand, the pull-up resistor Rp2 is set as Rp2 = 5 X Rp1. With this constitution, solar radiation quantity at the time of shining is detected based on a characteristic approximately equal to a conventional characteristic by selecting the pull-up resistance Rp1. As solar radiation reduces gradually, input voltage increases gradually, and when it exceeds the specified value, the pull-up resistance Rp1 is switched to the pull-up resistance Rp2, thus it is possible to detect solar radiation accurately even at the time of evening or cloudy weather with a small solar radiation quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for display brightness in an automotive air conditioner.

[Conventional technology]

In automobile air conditioners, control is performed to 1) detect the amount of radiation and correct the control temperature and air volume based on the detected value to eliminate the feeling of hot air for occupants caused by exposure to solar radiation. ing.

Fig. 2 shows an example of the configuration of an automobile air conditioner, which is integrated with a control device ff,1 for controlling the temperature, air volume, and input/output functions of the control panel of the air conditioner, and a control device 1 for controlling the temperature, air volume, and input/output functions of the control panel. Control panel 2 for receiving button operations and displaying the operating status of the air conditioner to passengers
, a radiation sensor 3 for detecting surrounding conditions, a temperature sensor 4.5, an air conditioning unit 6 that blows temperature-controlled air into the vehicle interior, and a plurality of control signals that transmit signals for switching the operation of the air conditioning unit 6. Line 7. and a plurality of return signal lines 8 for detecting operation of the air conditioning unit 6.

In the above configuration, the control device 1 performs necessary calculations based on the selection signal from the control panel 2 and the signals from each sensor 3 to 5, outputs a control signal to the air conditioning unit 6, and maintains the interior of the vehicle under comfortable conditions. Operate to maintain.

At the same time, the current operating status of the air conditioner, etc. is displayed on a display member within the control panel 2.

Figure 3 shows an example of the control panel 2.
Each operation button type IO1 operation indicator 11 and display panel 12 are provided. The operation buttons 10 include an AUTO button to select fully automatic control, a DEF button to select defroster blowout, and an OF button to select stop of the air conditioner.
The F button, the REC button to select recirculation of the air inside the vehicle, the set temperature (, Δ) button to select the desired temperature, the F A N button to select fixing the air volume to a fixed value, etc. ing. The activation indicator 11 lights up when recirculation is selected and informs the occupant of the activation. Also, display panel 1
2. The setting status of each operation button IO and the operating status of the air conditioner are displayed. Here, it is assumed that the operation indicator 11 and the display panel 12 use a fluorescent display tube (VFD) as a display member. Generally, such a display member is displayed with high display brightness in order to make the displayed content easier to read even when the surroundings are bright during the day. However, when the surroundings become dark, such as from evening to night, and the passengers' eyes change accordingly, it is difficult to see the display if it is displayed at the same brightness as during the day. For this reason, the brightness is controlled to be significantly lowered (attenuated) at night and the like.

Conventionally, high brightness operation during the day and low brightness operation at night have been controlled by turning on/off vehicle lamps and by outputting from a solar radiation sensor provided for air conditioning. FIG. 4 shows an example of the internal configuration of a conventional control device 1 that performs such 511 degree control, and the parts related to dimming control of the display member include a 1-chip microcomputer 13, a display Control signal line 15, display control circuit 1
4. vL input terminal to which signals to turn on/off the lamps in the car are input, pull-up resistor RP for solar radiation detection
It is equipped with Furthermore, details of the display control circuit 14 are shown in FIG.
, an operation indicator 11 using an emitting diode (
Corresponding to the same number 11 in Figure 3), driver TC16
, VFD17. Microcomputer 1
3, drive signals CI, , D^, L are sent to the driver 15.
^yBL is input.

In such a configuration, the output terminal of the microcomputer 13 connected to the base resistor RBI is 1'''
(high level), the transistor r1 turns on, and the current Va changes from the load resistance 1 to Ll to the operation indicator 1.
1. Current flows through the transistor 'r1, and the operation indicator 11 lights up with high brightness. On the other hand, when the vL terminal connected to the microcomputer 13 becomes 1111+, the output terminal of the microcomputer 13 connected to the base resistor RR2 is also set to tr 1'' at the same time.゛2 is also turned on, and the current flowing through the operation indicator ll is connected to the load resistance RLz.
, shunted to transistor T2, operating indicator 11
The activation indicator 11 dims as the current flowing into it decreases.

Next, a method of dimming the VFD 17 in FIG. 5 will be explained. Four driving signals are sent from the microcomputer 13 to the driver 16 by serial transmission. CL is a clock signal for data transmission timing, D^ is a data signal indicating information to turn on or off each segment of V F D, LA is a latch signal indicating completion of transmission of a set of data, and display contents is transmitted by the above three signal lines. The remaining BL terminal is a blanking signal, and when this is 111 IT, the above 3
Each segment of VF'D specified by the main signal line lights up, and when it is "0", all VFD segments go out. Therefore, during the day, the BL terminal is always
By setting it to II, the vFD is displayed with high brightness, and if dimming is required, +3. By switching the terminal output to "071 111" with a constant duty ratio, dimming control can be performed according to the duty ratio.

The inputs to the brightness control mechanism described above are the voltage vL indicating on/off of vehicle lamps and the output voltage 2 of the radiation sensor 3, which are input to the microcomputer 13. Therefore, the output of the solar radiation sensor 3 is small compared to the voltage vL when the lamp is turned on at night. By programming the processing contents of the microcomputer 13, it is possible to control the brightness in dark times such as at night. A conventional example of brightness jσ control using the output of a solar radiation sensor for air conditioning control is disclosed in Japanese Patent Laid-Open No. 101845/1984.

[Problem to be solved by the invention]

BACKGROUND ART In recent years, in order to ensure safety while driving, it has become common to turn on small lamps or headlamps even during the daytime when the weather is bad, such as cloudy or rainy. In particular, in some regions of North America, it is mandatory by law to turn on headlamps during rainy weather. For this reason, when conventional lamp on/off control is performed, the brightness of the display member decreases even during the day when the lamp is turned on, and this dimming rate is usually about 1/4 to 1/10, and is affected by the surrounding brightness. As a result, there has been a problem in that the displayed content on the display member may become unreadable. Further, this control based on lighting of the light has the problem that only control that rapidly changes the brightness can be performed, and smooth control that corresponds to the brightness of one surrounding cannot be performed.

Next, problems when using the solar radiation sensor output will be explained. Figure 6 shows an example of the human output characteristics of the diode to photo 1 that constitutes the solar radiation sensor 3, and shows excellent linear characteristics over a very wide range with a change ratio of about 108 to the input scene. Motsu. In the same figure, A shows the approximate value of the amount of input light when sunlight is received on a clear day, B shows the approximate value of the input light amount when it is cloudy, rainy, or in the evening, and C shows the approximate value of the amount of input light at night. When a photodiode having this characteristic is used as the solar radiation sensor 3 in FIG. 4 and the pull-up resistor R is set to an appropriate value, the relationship between the solar radiation amount Z and the input terminal 2 becomes as shown in FIG. Here, the value of pull-up resistor 1<P is.

For point A, which is the amount of solar radiation when receiving solar radiation on a clear day,
Considering some margin, the input terminal is set to a value that does not saturate the input terminal up to 1.5 to 2 times the amount of l'.

Here, since the change in the input voltage ■2 with respect to the solar radiation ff1Z is linear, point B in Figure 6 written on a logarithmic scale (during daytime cloudy or rainy weather, the brightness is 1/10 to 1/100 of A) ) has a value very close to O in FIG. Another 0 points (
At night, at a brightness of 1/10 to L/100 of B), it is small, and in FIG. 7, it is almost at the origin and cannot be displayed. In this way, in the conventional method using the 1" pair, the value of the pull-up resistor is determined to effectively detect the amount of solar radiation on a clear day. There were problems in that it was impossible to accurately detect the brightness, and it was impossible to perform accurate and smooth brightness control.

An object of the present invention is to accurately detect changes in ambient brightness from cloudy and rainy days to nighttime using a solar radiation sensor included in an automobile air conditioner, thereby detecting changes in the brightness of a display device. To provide a method for controlling display brightness that can be performed smoothly according to changes in brightness.

[Means to solve the problem]

In order to achieve the above object, in a method for controlling brightness by detecting ambient brightness using a solar radiation sensor, the sensitivity of the circuit that detects the sensor output can be switched, and the The system was configured to automatically switch this sensitivity.

[For production]

The brightness during clear skies and the brightness from evening to night are as follows:
Since the ratio varies greatly from 102 to 104, it was not possible to accurately detect the ambient brightness from evening to night. Therefore, if the sensitivity of the solar radiation A detection circuit is controlled by a microcomputer so that it increases when the amount of incident light decreases, brightness from evening to night can be detected with high accuracy. Furthermore, during clear daytime weather, the amount of incident light is sufficiently large and the sensitivity of the solar radiation detection circuit is low, so the photodiode sensor will not become saturated due to the large amount of incident light.

〔Example〕

The present invention will be explained below using examples. FIG. 1 shows an embodiment of the present invention, and a conventional control device 1 (FIG. 4)
1A is shown. With this configuration, the fourth
What is different from the diagram is the two pull-up resistors tap, +
RP2 is provided, and the analog switch 18 can perform this selection change with support from the microcomputer 13. Here, the pull-up resistor +<p, similar to the pull-up resistor 11<P in Figure 4, is a value that will not saturate the input terminal 2 up to about 1.5 to 2 times the incident photoacid on clear skies. is set, while pull-up resistor RP2
is set to R,·2=5XRP.

FIG. 8 is a characteristic diagram when the amount of solar radiation is read by switching these pull-up resistors.

The normal amount of solar radiation on a clear day is shown at point A in the figure, and in such a case, by selecting the pull-up resistor Rpl in Figure 1, a straight line almost equal to the conventional characteristic shown in Figure 7 can be obtained. Solar radiation is detected according to the characteristics of g1. On the other hand, 1] As the amount of radiation gradually decreases, the input voltage ■ gradually increases, but when this input terminal exceeds a predetermined threshold value VZI, a pull-up resistor RP2 is applied instead of the pull-up resistor RP+.
Switch to

Then, the characteristic becomes g2 in the figure, and the amount of solar radiation can be detected with high accuracy even in the evening or on cloudy days when the amount of solar radiation is small as at point B. In addition, when the pull-up resistor 1<P2 is selected and the 1'' resistance increases again, the input voltage V2
gradually decreases, and if left as it is, it will soon reach saturation, making it impossible to read the amount of solar radiation. Therefore, under this condition, the pull-up resistor is switched from Rp2 to RP+ again to make it possible to read the amount of L in clear weather, but the threshold value VzZ at this time of switching is set to a value slightly larger than VZI to provide hysteresis characteristics. . This is to prevent the pull-up resistor from switching frequently and making the reading of the solar radiation unstable if the solar radiation slightly changes near the switching point. In addition, in order to effectively switch between the two characteristics, it is preferable to set the threshold value Vzl l Vz2 to a voltage value that is about 10% from both ends of the maximum change width of the input terminal.

The above-mentioned switching of the pull-up resistor and detection of the l'' ground are performed by the microcomputer 13, and the procedure is shown in FIG. This shows only the procedure for reading L1 shooting, but first step +
00, it is determined whether the R gate is selected as the pull amplifier resistor.

If the R gate is selected, the process proceeds to step 1 old, and it is determined whether the input voltage 2 is greater than Vzl.

If V Z > V a1, it can be estimated that the current ejection is small, so in order to accurately read the weak l' logarithm, proceed to step 102, and set r< as a pull-up resistor.
Select P2. On the other hand, at step lol ■2≦Vz
If it is l, it can be determined that strong solar radiation is being received, so the process directly goes to the next step 105. Also step 10
If R1・1 is not selected at 0, that is, I<pz
is selected, the process advances to step IO:3, and from then on, R is selected in step 104 only when v4<vz2.
Select p. Next, in step 105, the input terminal ■1 to the microcomputer 1:1 is input. wait until it stabilizes. . This is necessary to read a stable input voltage without being affected by stray capacitance, etc., because when the pull-up (tl/) switching is performed, ■2 changes suddenly due to this switching.Next In step 106, the input voltage V2 is read as digital data by the A/Di conversion function of the microcomputer 13.In step 107, the conversion coefficient is set to 2, depending on the value of the currently selected pull-up resistor. 1 or 2 is selected as the value of Kl+. 2 corresponds to the slope of the characteristic of gL g2 in FIG. 8. Next, in step 110,
2. Given above. According to this embodiment, the actual amount of solar radiation Z is calculated from the constant voltage vc given in advance and the value of (2) read earlier.
h? The brightness of the display member can be smoothly adjusted according to the signal Z of the rE irradiance (brightness) of Niku et al. since the brightness in the sky, the brightness in rainy weather, and even lower brightness can be detected accurately and continuously. It can be changed.

In this case, assuming that the display control circuit 14 in FIG. 5 is used to smoothly control the brightness, the brightness of V F l) is controlled by the blanking signal line) 31. This can be achieved by gradually changing the duty of the signal.

On the other hand, regarding the operation indicator 11, instead of using the dimming method using the transistor T2 and the resistor RB29 RL2, the transistor '17+ is turned on and off via the resistor RB+ and its dani-ity is changed, so that the conventional circuit method is used. Achieves smooth brightness changes.

FIG. 10 shows another embodiment of the present invention, which differs from FIG. 1 in that it includes an amplifier circuit 20 for amplifying the output Hia current of the solar radiation sensor 3, and that multiplexer (analog switch) instead of
4 negative feedback resistors Rf I” R switched by 19
(This is where 4 is used.

Resistors R,, R2 are the power rudder V. The basic voltage is created by dividing the voltage. The resistor Rfl is a resistor with a value equivalent to the resistor 1'<p in Fig. 1, and the other negative feedback resistors are R(I(R(2(R(3't: )((4)). Operational amplifier 20, fixed resistance R+, ■<z,
The negative feedback resistors Rfl-Rf4 form an inverting amplifier circuit, and the amplification factor thereof is proportional to the resistance value of the negative feedback resistor.
By setting the ratio of the resistance values of each negative feedback resistor to a large value, it is possible to detect a wide range of brightness from the amount of solar radiation on a clear day to the range of a dark night.

According to this embodiment, it becomes possible to accurately perform dimming control of the display member over a wider range of brightness changes, and also to read brightness signals accurately even in darker areas, so the solar radiation sensor The control circuit itself can determine a disconnection failure (previously, the accuracy was low and it was not possible to distinguish between no solar radiation and a disconnection failure), which has the effect of improving serviceability and operational reliability of the air conditioning system.

〔Effect of the invention〕

According to the present invention, by using the solar radiation sensor included in the automatic i1L air conditioner, the surrounding I/H
It is possible to accurately detect changes in the brightness of the display device, and the brightness of the display device can be smoothly changed in response to the detected surrounding brightness. Problems such as display contents becoming unreadable due to significant dimming of the light can be resolved, and changes in brightness become smoother, which has the effect of allowing natural brightness control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. Figure 2 is a block diagram showing an example of the system configuration of an automotive air conditioner, Figure 3 is a diagram showing an example of a control panel, and Figure 4 is a diagram showing an example of a control panel.
5 and 5 are diagrams showing a conventional control device, FIG. 6 is a photodiode input/output characteristic diagram, FIG. 7 is a relationship diagram between incident amount and input voltage, and FIG. 8 is an embodiment of FIG. 1. FIG. 9 is a diagram showing the program processing procedure in the embodiment of FIG. 1, and FIG. 10 is a block diagram showing another embodiment of the present invention. IA...control device, 2...control panel, 3
...Solar radiation sensor, 11...Operation indicator, 1
2...Display panel, 18.19...Analog switch (multiplexer), Rp+t RP2...Pull-up resistor, Rf+~Rf4...Negative feedback resistor, 20
...Operation amplifier.

Claims (1)

[Scope of Claims] 1. A solar radiation sensor for detecting the amount of solar radiation, a solar radiation amount determining means for determining the amount of solar radiation from the output of the sensor, and the brightness decreases more as the amount of solar radiation determined by the means increases. In the display brightness control device comprising a display control means for changing the display brightness of the display member so as to
The solar radiation amount sensor has a configuration in which a plurality of input sensitivities can be set, and a switching means is provided for switching the input sensitivity of the solar radiation amount determining means in accordance with the value of the solar radiation determined by the solar radiation amount determining means. A display brightness control device characterized by: 2. The switching means switches the sensitivity with a hysteresis characteristic by making the determined threshold value for switching when the amount of solar radiation increases larger than the threshold value for switching when the amount of solar radiation decreases. The display brightness control device according to claim 1.