JPH0660882U - Display dimming circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] Prevent the characteristic curve for dimming from being switched by switching the lighting switch. A display dimming circuit for dimming the brightness of a display based on a switching signal from a lighting switch is provided with means for reducing the dimming function when the lighting switch is turned on.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a display dimming circuit for adjusting display brightness of a display.

[0002]

[Prior art]

 A conventional display dimming circuit of this type will be described with reference to FIG. That is, 1 is a battery, 2 is a lighting switch, and 3 is a dimming operation unit, which is provided with adjusting means for operating the degree of dimming, and the dimming voltage whose voltage value changes according to the operation amount of the adjusting means. A signal (voltage value corresponding to the horizontal axis in FIG. 3) is output.

Reference numeral 4 denotes a duty conversion circuit, which is high with respect to the transistor 5 in order to display the display unit 9 such as a fluorescent display tube at the maximum brightness when the lighting switch 2 is opened (that is, in the daytime). When the level signal is output (the lamp 6 is off at this time) and the lighting switch 2 is closed (that is, at night), the lamp 6 has the brightness shown in FIG. The dimming characteristic curve A is selected, and the display unit 9 such as a fluorescent display tube selects the brightness dimming characteristic curve B.

As a result, according to the selected characteristic curve, the duty conversion circuit 4 converts the voltage value of the dimming signal supplied from the dimming operation unit 3 into the duty of the pulse, and the transistor 5 according to the duty of the pulse. To turn on or off.

Reference numeral 6 denotes an illumination lamp, which is turned off while the lighting switch 2 is open, and when closed, the collector terminal voltage becomes 0 (V) every time the transistor 5 is turned on, and The lamp 6 lights up. A display signal conversion circuit 7 converts a detection signal C supplied from a sensor (not shown) into a digital display signal, and further converts the converted display signal into a signal from the duty conversion circuit 4 via the transistor 5. Based on the pulse width modulation, it is supplied to the display unit 9 via the display drive circuit 8 in the next stage.

That is, in the above configuration, the detection signal C from the sensor is converted into a digital display signal by the display signal conversion circuit 7. At this time, if the lighting switch 2 is opened, that is, during the daytime. The output of the duty conversion circuit 4 is maintained at a high level regardless of the external operation of the dimming operation unit 3. As a result, the display lamp 6 is turned off, and the display portion 9 such as a fluorescent display tube is lit up with maximum brightness.

When the lighting switch 2 is closed, that is, at night, the transistor 5 turns on the display lamp 6 in accordance with the brightness characteristic curve A with the brightness according to the output signal from the duty conversion circuit 4. The display signal from the display signal conversion circuit 7 is pulse-width modulated according to the brightness characteristic curve B and supplied to the display unit 9, and is displayed with brightness according to the degree of the pulse width modulation.

[0008]

[Problems to be solved by the device]

 However, in such a conventional display dimming circuit, by switching the lighting switch 2 from the open state to the closed state, the display unit 9 such as the fluorescent display tube is controlled from the maximum brightness display to the nighttime dimming. Since it can be switched to the characteristic curve B for light, the lighting switch is closed for safety in the evening or when the fog is standing up, and when the small lamp or headlamp is turned on, the surroundings are bright. There was a problem that the brightness of the image was dark and it was difficult to see.

The present invention has been made to solve the above problems, and an object thereof is to prevent the characteristic curve for dimming from being switched by switching the lighting switch.

[0010]

[Means for Solving the Problems]

 The display dimming circuit according to the present invention is a display dimming circuit for dimming the brightness of a display based on a switching signal from a lighting switch, and when the lighting switch is turned on, the dimming control is performed. It is provided with a means to reduce (or cancel) the function.

[0011]

[Action]

 According to this invention, even if the lighting switch is closed in the fog, the dimming characteristic curve does not switch, and the brightness is the same as when the lighting switch is open, so it is easy to see.

[0012]

【Example】

 Hereinafter, the present invention will be described in detail with reference to FIG. In FIG. 1, the same or equivalent components as those shown in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted.

That is, 11 is a cancel switch (means for reducing or canceling the dimming function). When the cancel switch 11 is closed, the input of the display signal conversion circuit 7 is input to the display signal conversion circuit 7. A signal is supplied to bring the collector voltage of the transistor 5 supplied to the terminal to a high level.

As a result, even if the lighting switch 2 is closed and the transistor 5 is alternately turned on and off repeatedly according to the duty of the pulse signal supplied from the duty conversion circuit 4, the display signal conversion circuit does not. The signal is input as a low level signal to generate a display signal, which is supplied to the display unit 9 via the display drive circuit 8 so that the display unit 9 is illuminated and displayed with the maximum brightness.

[0015]

[Effect of device]

 As described above, according to the present invention, even if the lighting switch is turned on in the evening or in the dim light of fog, if the driver feels that the display is dark, he / she operates one switch. The effect of being able to easily obtain a display with daytime display brightness is demonstrated.

[Brief description of drawings]

FIG. 1 is a circuit block diagram according to an embodiment of the present invention.

FIG. 2 is a circuit block diagram showing a conventional example.

FIG. 3 is a characteristic diagram for explaining dimming of a display lamp and a display unit in the circuit block diagram of FIG.

[Explanation of symbols]

 2 Lighting switch 3 Dimming operation section 4 Duty conversion circuit 5 Transistor 6 Display lamp 7 Display signal conversion circuit 8 Display drive circuit 9 Display section 11 Cancel switch

Claims (1)

[Scope of utility model registration request] 1. A display dimming circuit for dimming the brightness of a display (6, 9) based on a switching signal from the lighting switch (2), when the lighting switch (2) is turned on, A display dimming circuit comprising a means (11) for reducing the dimming function.