JPS62134344A - Dimmer circuit for vehicle-loaded equipment indicating part - Google Patents

Abstract

PURPOSE:To maintain good contrast at all times by providing a variable resistor for dimmer controlling, converting its output voltage into a digital value and inputting it into an MPU, to change the luminance of a vehicle-loaded equipment indicating part, in many stages. CONSTITUTION:The captioned circuit, when used in a vehicle-loaded electronic tuning radio receiver consisting of an antenna 1, a high frequency stage 2, a mixer 3, an intermediate frequency stage 4, a detecting circuit 5, a low frequency amplifier 6, and a speaker 7, has a manually operatable variable resistor R1, and an A/D converter 20 which converts the output voltage V of the resistor R1 into a digital value and input it into an MPU 11. And, when a digital value corresponding to the operated quantity of the variable resistor R1, is inputted into the MPU 11 from the A/D converter 20, the duty control of the luminance of a display 13 can be made in accordance with the digital value by means of the MPU 11. Thereby, the control of luminance can be carried out in many stages, to maintain good contrast at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a dimmer circuit for a display section of a vehicle-mounted device, and in particular allows brightness adjustment in multiple stages.

[Conventional technology]

Since the brightness inside a car cabin varies greatly depending on the environment outside the car, good contrast cannot be obtained unless the brightness of the indicators and displays of the on-board equipment is changed minutely. Additionally, some countries require this type of dimming control.

FIG. 11 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, and 8 is a reception local ( LO), 9 is a phase-locked loop (PLL), 1
0 is a low pass filter (LPF), 11 is a microcomputer (MPU), 12 is a key matrix, 13
is the display, 14 is the illuminated switch, 1
For example, 5 is one of the lamps for character illumination, and 10B is a battery.

In the radio receiver of this example, when the frequency division ratio of PLL9 is set from MPUII, LO8, PLL9. A closed loop consisting of LPFIO determines the frequency of LO8 and also determines the tuning frequency of RF2.

The MPU II is activated by inputting the key matrix 12.
Change the division ratio of 9 and display 13 at that time.
(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 II to reduce the brightness of the display 13 when the switch is turned on (for example, by dynamically driving the illumination switch 14). (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 you lower the brightness to make it suitable for nighttime, the display will not have enough light in the evening.
There is a drawback that the contrast of 3 is reduced. The difference in light intensity between the suburbs and the city also causes a decrease in contrast.

The present invention provides a variable resistor for dimmer control separately from the illumination switch, thereby making it possible to control dimming in multiple stages.

[Means for solving problems]

The present invention relates to a variable resistor for dimmer control, an A/D converter that converts its output voltage into a digital value, a microcomputer that reads the output digital value of the converter, and an in-vehicle device whose display is controlled by the computer. and a display section, and the computer is characterized in that it adjusts the brightness of the display section based on the digital value.

[Effect]

By providing a variable resistor for dimmer control and converting its output voltage into a digital value using 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, it becomes possible to adjust the brightness in multiple stages by manually operating the variable resistor.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention, which includes a manually operable variable resistor R1 and an A/D converter 2 that converts its output voltage V into a digital value and inputs it to the MPU II.
The difference from FIG. 11 is that 0 is provided. The variable resistor R1 is used for dimmer control 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 an illumination switch, for example. The A/D converter 20 is connected to the MPUI as shown in FIG.
When receiving the start signal from I, the analog voltage V is changed to 2.
AID conversion is performed into an N-bit digital value (data) with a resolution of , and when the conversion is completed, an end signal END is returned to the MPU 11. After receiving this END, the MPU 11 takes in N-bit data, and displays the display 13 according to the value.
Duty control of brightness. FIG. 4 is a time chart of FIG. 3, in which the start signal is repeatedly generated in synchronization with the cycle at which the MPU II 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 II 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 brightness is adjusted by controlling the on-time ratio (duty ratio) of the segments to be lit. In other words, the display period of the same segment (
For example, write 1 in half of 10m5) and write O in the remaining half.
If you write , 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.

In FIG. 6, N bit data is N1. N2. N3.・・・・・・
Corresponding to the value..., the duty ratio of the anode voltage of the segment to be lit is 50%.

This figure shows how the ratio changes from 75% to 25%. This duty control is performed by an MPU II program (described later).

FIG. 7 is a flowchart of display control, using a synchronization flag and a display ON flag. The synchronization flag is used to specify the display period (for example, 10m5), and is used to specify the display period (for example, 10m5).
Set the flag to 1 when displaying. Display data output is a step of writing display data into the register REG in FIG. The timing signals are T1 to T4 in FIG.
This is sequentially applied to the 4×4 key matrix 12 (FIG. 1) to read the key power. The A/D input is the digital value of the output voltage (■) of the variable resistor R1, which is the previous N-bit data.

After this, there is a SW (switch) determination process, and further display data editing such as frequency and channel is performed. last tl, t
The setting 2 is the setting of the lighting time t1 and the lighting time t2 in FIG. 9, in other words, the setting of the duty ratio, and this is the setting of the A/
This is done based on the D input. An interval timer is used to count tl and t2, and the interrupt processing is performed as shown in FIG. This interval timer alternately counts tl and t2 and generates an interrupt. FIG. 9 is a time chart showing this interrupt timing, display control, etc.

The target of the SW judgment process in Figure 7 is the accessory switch (
Ace), radio switch, auto search up (AS
U), power switch (power SW), etc. FIG. 10 is a flowchart of the power SW process. The above-mentioned display ON flag is set only while the radio is ON, and necessary display data is displayed on the display 13 during that time.

On the other hand, when the display ON flag is reset by turning off the radio, the interval timer operates constantly and no display is performed on the display 13 even if an interrupt is generated.

〔Effect of the invention〕

As described above, according to the present invention, by manually operating the variable resistor for dimmer control, the brightness of the in-vehicle device display section can be switched to multiple levels depending on the surrounding brightness, and the brightness is always maintained. Able to maintain contrast.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a characteristic diagram of a variable resistor for dimmer control, Fig. 3 is a detailed view of the main part of Fig. 1, and Fig. 4 is a time chart thereof. 5
The figure is a circuit diagram showing a specific example of a display, Figure 6 is an explanatory diagram of duty control, Figure 7 is a flowchart of display control, Figure 8 is a flowchart of duty control, Figure 9 is a time chart of display control, and Figure 9 is a time chart of display control. FIG. 10 is a flowchart of power SW processing, and FIG. 11 is a block diagram showing an example of a conventional dimmer circuit. In the figure, R1 is a variable resistor, 11 is a microcomputer, 13 is a display, and 20 is an A/D converter. Applicant: Fujitsu Ten Ltd. Representative Patent Attorney Minoru Aoyagi 811 reviews of Pro Softa Figure 1 Figure 1 of Nobufu Bonmei no Mi 7#j! iB exit Figure 3 Start; Time officer in the 3rd ward Figure 5 Example of actual display Duty 50% 50% 75F
: 75m/, 25% duty cycle control flowchart of g date/month cause display control Fig. 7, Sho control fimnamart Fig. 9 Power SW processing flowchart' M10 Fig. Conventional D7-recovery Fig. 11

Claims (2)

[Claims] (1) A variable resistor for dimmer control, an A/D converter that converts its output voltage into a digital value, a microcomputer that reads the output digital value of the converter, and an in-vehicle device whose display is controlled by the computer. A dimmer circuit for a display section of an in-vehicle device, comprising a display section, wherein the computer adjusts the brightness of the display section based on the digital value. (2) A dimmer circuit for a display section of an in-vehicle device according to claim 1, wherein the brightness of the display section is adjusted by duty control.