JPH0375363B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a dimer circuit that adjusts the brightness of a display section, and particularly to a dimer circuit that allows brightness adjustment values to be preset and switched in multiple stages.

[Prior Art] Since the brightness inside an automobile cabin varies greatly depending on the environment outside the vehicle, good contrast cannot be obtained unless the brightness of the indicators and displays of the in-vehicle equipment is minutely changed. Also,
In some countries, this type of dimming control is mandatory.

FIG. 14 shows an example of a conventional dimmer circuit, which attempts to switch the brightness of the display of a car-mounted electronically tuned radio receiver between day and night. In the figure, 1 is an antenna, 2 is a high frequency stage (RF), 3 is a mixer (MIX), 4 is an intermediate frequency stage (IF), 5 is a detection circuit (DET), 6 is a low frequency amplifier (AFAMP),
7 is a speaker, 8 is a reception local (LO), 9 is a phase locked loop (PLL), 10 is a low pass filter (LPF), 11 is a microcomputer (MPU),
12 is a key matrix, 13 is a display unit whose brightness is adjusted, 14 is an illumination switch, and 15 is a display 1 whose brightness is adjusted.
A display unit other than 3, such as a character illumination lamp, +
B is boring.

The radio receiver in this example has MPU11 to PLL9.
Setting the division ratio of LO8, PLL9, LPF1
The frequency of LO8 is determined in a closed loop consisting of 0,
Also, the tuning frequency of RF2 is determined. MPU11
changes the frequency division ratio of the PLL 9 by inputting the key matrix 12, and also changes the display 1 at that time.
3. Change the display (frequency or channel display, etc.).

[Problem that the invention seeks to solve]

The dimmer circuit of the radio receiver described above regards the existing illumination switch 14 as part of the key matrix 12, and controls the MPU 11 to reduce the brightness of the display 13 when the switch is turned on (for example, by dynamic drive). (duty control). However, since the switch 14 turns on the side lamps in addition to the lamps 15 inside the vehicle, it is turned on not only at night but also in the evening. Therefore, if the brightness is also lowered to be suitable for nighttime, there is a drawback that the contrast of the display 13 decreases due to insufficient light in the evening. The difference in light intensity between the suburbs and the city also causes a decrease in contrast.

In the present invention, a variable resistor for dimer control is provided separately from the illumination switch, thereby enabling dimming control by presetting desired brightness in multiple stages.

[Means for solving problems]

The present invention includes a variable resistor for controlling the dimmer of in-vehicle equipment, an A/D converter that converts the output voltage into a digital value, and an A/D converter that reads the output digital value of the converter and performs each operation process of the in-vehicle equipment. a key matrix having a dayr switch and a plurality of channel switches, the computer presetting the output digital value of the A/D converter with a first instruction of the dayr switch and the channel switch; and a function of adjusting the brightness of the display section by reading out one of a plurality of preset digital values in response to a second instruction of the dimmer switch and the channel switch, and further having a function of adjusting the brightness of the display section by reading out one of a plurality of preset digital values in response to a second instruction of the dimmer switch and the channel switch. The present invention is characterized in that an A/D converter is provided to convert the preset digital value into an analog voltage, and the analog voltage is used as a power source for other display sections.

[Effect]

Equipped with a variable resistor for daymer control,
When the output voltage is converted into a digital value by an A/D converter, the computer that controls the display section of the vehicle equipment can read the digital value.
Therefore, by incorporating a program that adjusts the brightness of the display section based on the digital value, multi-step brightness adjustment becomes possible. This multi-step brightness adjustment can be done by manually operating the variable resistor each time, but in the present invention, the brightness at several points is preset by operating a key matrix, and then the variable resistor is operated. To switch brightness by operating the key matrix without having to do so.

〔Example〕

FIG. 1 is a block diagram showing the basic configuration of the present invention, including a manually operable variable resistor R1 for controlling a dimmer of in-vehicle equipment, and a variable resistor R1 that converts its output voltage V into a digital value and inputs it to the MPU 11. /
The difference from FIG. 14 is that a D converter 20 is provided. The variable resistor R1 is used to control the dimmer of the entire vehicle interior or individual vehicle equipment, and has a linear conversion characteristic as shown in FIG. The power divided by this variable resistor R1 is a constant voltage, and is supplied through, for example, an illumination switch. The A/D converter 20 is configured as shown in FIG.
When it receives a start signal from the MPU 11, it A/D converts the analog voltage V into an N-bit digital value (data) with a resolution of ^2N , and when the conversion is completed, it returns an end signal END to the MPU 11. MPU11
takes in N bit data after receiving this END. The preset operation will be described later, but when adjusting the brightness by manual operation of R1, the brightness of the display 13 is duty-controlled in accordance with the value of the captured N-bit data. FIG. 4 is a time chart of FIG. 3, in which the start signal is repeatedly generated in synchronization with the cycle in which the MPU 11 reads the state of the key matrix 12.

FIG. 5 shows a specific example in which the display 13 is a fluorescent display tube, where A is an anode of each segment, G is a grid, and H is a heater. The MPU 11 writes display data for each segment into the output register REG, and when the data is 1, the corresponding segment is turned on (0 is turned off). FET is a driver transistor that drives anode A. At this time, a dynamic drive method is adopted, and the brightness is adjusted by controlling the on-time ratio (duty ratio) of each segment to be lit. In other words, write 1 in half of the display period (for example, 10ms) of the same segment,
If 0 is written to the remaining half, the duty ratio will be 50%. 0 is written in the segments that are to be turned off throughout one cycle. The duty ratio in this case is 0
%. As the duty ratio increases, the brightness increases, and conversely, as the duty ratio decreases, the brightness also decreases. FIG. 6 shows that the duty ratio of the anode voltage of the segment to be lit is 50%, 75%, 25%, etc., corresponding to the N bit data taking the values N ₁ , N ₂ , N ₃ , ...
This shows how things change. This duty control is performed by the MPU 11 program.

FIG. 7 is a general flowchart of the MPU 11, which uses a synchronization flag and a display ON flag. The synchronization flag is used to define the display cycle (for example, 10 ms), and the display ON flag is set to 1 when displaying. Display data output is a step in which display data is written to the register REG in FIG. The timing signals are ₁ to ₄ in Figure 9,
This is sequentially applied to the 4×4 key matrix 12 (FIG. 1) to read key inputs. The A/D input is the digital value of the output voltage V of the variable resistor R1, which is the previous N-bit data. After this, the process moves to switch judgment processing, and display data such as frequency and channel are further edited. The last setting of t1 and t2 is the setting of the lighting time t1 and the lighting time t2 in FIG. 9, or in other words, the setting of the duty ratio. An interval timer is used to count t1 and t2, and the interrupt processing is performed as shown in FIG. This interval timer counts t1 and t2 alternately and generates an interrupt. FIG. 9 is a time chart showing this interrupt timing, display control, etc.

The key matrix 12 in Figure 1 has 4x4=16 switches (keys), of which the keys in Figure 7 are
In the SW judgment process, accessory switch (Acc), radio switch, auto search up (ASU), power switch (power SW), daymer switch,
This applies to channel switches (CHn). The dammer SW is used in conjunction with the channel switch CHn when performing brightness adjustment using a preset method.
CHn is a general term for CH ₁ , CH ₂ , . . . , and here it also serves as a radio preset channel switch.
For this reason, when adjusting the brightness, use a dimmer SW,
Even for the same CHn, a memory address different from the radio mode is selected.

Daymer presetting is performed by pressing and holding down the daymer SW and CHn simultaneously for a certain period of time (hereinafter referred to as 2 seconds). FIG. 10 is a flowchart showing details of this process. Damer SW and CHn
If you press and hold for more than 2 seconds at the same time (first instruction),
When 2 seconds have elapsed, the brightness (duty) is preset in the CHn memory. This duty is
Since the voltage V of the variable resistor R1 at that time is A/D converted and calculated from the N-bit data, this N-bit data may be preset. In any case, after presetting, a preset completed flag is set, indicating that the CHn memory contains preset data. Since this presetting can be performed for n channels by changing CHn, presetting can be performed sequentially by changing several points of R1 to obtain multi-level brightness.

Reading of the preset data is performed by pressing the same daimer SW and CHn as at the time of presetting for less than 2 seconds (second instruction). Therefore, the first
The preset process shown in FIG. 10 before the read process shown in FIG. 1 is performed halfway. However, since the preset processing is completed incompletely, the preset is not performed in the CHn memory, and conversely, the preset brightness (duty) is stored from the CHn memory as shown in Figure 11.
data is read.

If the variable resistor R1 is varied without pressing the dammer SW, the duty will change based on the A/D conversion value, and the brightness will change. This is not only necessary for presetting, but it is convenient to have this function as it allows you to continuously vary the duty. Note that the steps within the broken line frame in FIG. 7 are those used in the embodiment of FIG. 13. Furthermore, in order to prevent malfunctions due to slight changes in the A/D conversion result due to noise or the like, the number of effective bits in the A/D conversion result may be reduced.

By the way, the above explanation describes the basic configuration of the present invention, but since the present invention also uses other display devices as in the past, the variable display as shown in FIG. Output voltage V of resistor R1
If you drive the display 15 with The balance between them is disrupted.

The present invention also solves this problem,
FIG. 13 shows an embodiment of the present invention. In this example, the first
A D/A converter 21 and a power selector switch 22 are added to the configuration shown in Figure 2, and the output port P of the MPU is also added.
1 to output a switching signal for the switch 22. The D/A converter 21 converts the data read from the memory of CHn mentioned above (in the previous example, it was the duty, but in order to simplify the explanation, the A/D converted value at the previous stage) into an analog voltage V'. This is a reverse conversion.

Returning to FIG. 7 again, since the MPU 11 can determine the state of the key matrix 12 and the state of the variable resistor R1, it can output a switch change signal of 1 or 0 to the output port P1 based on the results. In other words, when the dimer SW and CHn are pressed to adjust the display 13 to the preset brightness, the A/D conversion value stored in the memory of CHn is inversely converted by the D/A converter 21, and the analog The voltage V' is transmitted through the switch 22 to the display 15.
to be applied. In this way, the display devices 13, 1
5's brightness balance remains unchanged. Also, when the variable resistor R1 is operated, the brightness of the display 13 is adjusted by the A/D converted value, so in this case, the brightness balance can be maintained by switching the switch 22 to the V side as shown. can.

[Effects of the Invention] As described above, according to the present invention, the brightness of the display section can be switched in multiple stages according to the surrounding brightness, and there is an advantage that several brightness points can be preset and selected. be. Furthermore, since the preset digital value is converted back into an analog value and used as a power source for other display sections, it is possible to maintain the brightness balance between the display section that is subject to preset type dimmer control and the other display sections.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the basic configuration of the present invention, Fig. 2 is a characteristic diagram of the variable resistor for dimmer control, Fig. 3 is a detailed view of the main part of Fig. 1, and Fig. 4 is its time chart. , Fig. 5 is a circuit diagram showing a specific example of the display, Fig. 6 is an explanatory diagram of duty control, Fig. 7 is a general flowchart, Fig. 8 is a flowchart of duty control, and Fig. 9 is a time diagram of display control. 10 is a flowchart of preset processing, FIG. 11 is a flowchart of readout processing, FIG. 12 is a block diagram showing a modification of FIG. 1, and FIG. 13 is a block diagram showing an embodiment of the present invention. 14 are block diagrams showing an example of a conventional dimmer circuit. In the figure, R1 is a variable resistor, 11 is a microcomputer, 13 is a display section, 15 is another display section, 2
0 is an A/D converter, 21 is a D/A converter, and 22 is a power changeover switch.

Claims (1)

[Claims] 1. A variable resistor for dayr control of in-vehicle equipment, an A/D converter that converts its output voltage into a digital value, and a microcomputer that reads the output digital value of the converter and processes each operation of the in-vehicle equipment. and a key matrix having a dimmer switch and a plurality of channel switches, and the computer is configured to switch the A/P on a first instruction of the dimmer switch and the channel switch.
A function to preset the output digital value of the D converter and one of the multiple preset digital values.
It also has a function to adjust the brightness of the display section by reading out the second instruction of the dimmer switch and the channel switch, and further converts the preset digital value read out by the computer into an analog voltage. A dimmer circuit comprising a D/A converter and using the analog voltage as a power source for another display section.