JPH0613012Y2 - Brightness adjustment circuit for automobile watches - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a brightness adjusting circuit for an automobile timepiece, and in particular, adjusts the brightness of only the timepiece by a switch that lights the timepiece when the accessory switch is off. Regarding what is possible.

(Prior Art) When a conventional automobile timepiece operates a volume of a brightness adjusting circuit for adjusting the brightness of the illumination of an instrument provided on an instrument panel, a signal for turning on the display is displayed. The duty ratio was variable, and the brightness was adjusted at the same time as the lighting of the instrument.

(Problems to be Solved by the Invention) As described above, the brightness adjustment of the conventional automobile timepiece is performed at the same time as the illumination of the instrument.

The balance of the brightness of the conventional timepiece and the illumination of the measuring instrument is set in advance at the time of assembly and is fixed.

For this reason, the user cannot arbitrarily adjust the brightness of only the timepiece.

Further, in order to independently adjust the brightness of the timepiece, it is generally necessary to provide a switch for adjusting the brightness separately from that for lighting the instrument.

SUMMARY OF THE INVENTION An object of the present invention is to provide a brightness adjusting circuit for an automobile timepiece, which can independently adjust the brightness of the timepiece without adding a switch and can adjust the brightness arbitrarily.

(Means for Solving the Problems) A brightness adjusting circuit for an automobile timepiece according to the present invention includes a clock circuit for clocking time, a display circuit for outputting a display signal based on the clock signal output from the clock circuit, A display unit that displays the time based on the display signal, an accessory switch that can be operated externally, an external switch that lights the display unit when the accessory switch is in an off state, and an instrument provided on an instrument panel Brightness adjustment of an automobile timepiece including a light switch for turning on the illumination of the instrument, and a brightness adjustment signal output circuit for outputting a brightness adjustment signal for adjusting the brightness of the illumination of the instrument provided on the instrument panel. In the circuit, a lighting signal is output in response to an operation signal from the external switch when the accessory switch is in an off state, and A switch switching circuit that outputs a lighting signal when the accessory switch is in the ON state and outputs a duty selection start signal in response to the operation signal; and a response to the brightness adjustment signal and the first clock signal from the timing circuit. A duty generating circuit for generating a pulse group having different duty ratios, and a pulse having different duty ratios output from the duty generating circuit in response to the duty selection start signal when the light switch is on. A duty selection circuit that sequentially switches and outputs in synchronism with a second clock signal from the clock circuit and that maintains the output of the pulse of the duty ratio selected when the duty selection start signal is stopped, and the duty selection circuit outputs Pulse, lighting signal from the switch switching circuit, and the light switch And a luminance signal output circuit for applying a selected luminance signal to the display circuit in response to the signal from the.

(Operation) In the brightness adjusting circuit of the automobile timepiece of the present invention, the brightness of the timepiece can be adjusted by turning on the external switch that lights the display unit when the accessory switch is in the off state.

That is, when the external switch is operated while the accessory switch is in the ON state, the switch selecting circuit outputs the duty selection start signal.

At this time, if the light switch is in the ON state, the duty selecting circuit sequentially switches and outputs the pulses of different duty ratios generated from the duty generating circuit in response to the output signal and the duty selecting starting signal.

The pulse output from the duty selection circuit is applied to the display circuit via the luminance signal output circuit, and changes the luminance of the display section.

Therefore, the brightness of the timepiece is adjusted by turning off the external switch when the display reaches the desired brightness, stopping the operation of the duty selection circuit, and maintaining the output of the pulse of the selected duty ratio. be able to.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a brightness adjusting circuit for an automobile timepiece according to an embodiment of the present invention.

Reference numeral 2 is a clock circuit, which is composed of an oscillation circuit 4, a frequency dividing circuit 6 that divides the output signal of the oscillation circuit 4, and a counter 8 that inputs and outputs a 1 Hz signal output from the frequency dividing circuit 6.

Reference numeral 10 denotes a display circuit, which receives a time signal from the counter 8 and outputs a code signal, and a decoder 12 which inputs the code signal and a brightness signal I from a brightness signal output circuit described later and outputs a display signal. The display driver 14 is included.

Reference numeral 16 denotes a display unit, which is connected to the electrode 16a of each digit to which a display signal from the display driver 14 is supplied, a common electrode 16b to which a lighting signal from a switch switching circuit described later is supplied, and a battery 17. Grid 16
and c.

Reference numeral 18 is an accessory switch for making an in-vehicle radio or the like operable.

Reference numeral 20 denotes an external switch for turning on the display unit 16 when the accessory switch 18 is in the off state, and also serves as a switch for brightness adjustment in this embodiment.

Reference numeral 22 is a light switch for turning on the illumination of the instrument provided on the instrument panel.

Reference numeral 24 is a brightness adjustment signal output circuit, which outputs a pulse generation circuit 26 that generates a pulse when adjusting the illumination of the instrument, and a brightness adjustment signal ILL composed of the pulse set by the variable resistor 30 when the pulse output from the pulse generation circuit 26 is input. It is composed of a one-shot multivibrator 28 for outputting.

32 is a switch switching circuit, which is an accessory switch 1
8 and the output signals ACC and S of the external switch 20, respectively.
OR gate 34 and AND gate 36 that input WA together
It consists of and.

38 is a duty generation circuit, which is a brightness adjustment signal ILL.
Is input to the reset input and the first clock signal φ ₁ from the intermediate stage of the frequency dividing circuit 6 is input to the clock input C, and its outputs Q _{0 to} Q ₃ and Q _{1 to} Q.
₃ and a, _{Q 2} and _{Q 3} to enter outputs signals B~D AND gate 42-46 Prefecture.

Reference numeral 48 denotes a duty selection circuit, which is a duty selection start signal and a second clock signal φ from the final stage of the frequency dividing circuit 6.
An AND gate 50 for inputting ₂ , an AND gate 52 for inputting the output signal thereof and a write signal LIG from the write switch 22, an OR gate 56 having one input terminal connected to the battery 17 via a capacitor 54, The output signal is input to the reset input R and the AND gate 52
Of the binary counter 58 for inputting the output signal A of the clock input C to the clock input C, and the NOR gate for inputting the inverted signals of the signals Q ₀ and Q ₁ and the clock signal φ ₂ to the other input terminal of the OR gate 56. 60, the signal from the output Q ₀ and the inverted signal from the output Q ₁ , the inverted signal from the output Q ₀ and the signal from the output Q ₁ , and the output Q ₀ ,
AND gates 62 to 66 for inputting the signals from Q ₁ to the respective two input terminals, NOR gates 68 for inputting the output signals F, G, H, and signals B, F, signals C, LIG.
And AND gates 70 to 76 for inputting the output signals of the NOR gate 68, the signals G and D and the signal H, and the signal E from the counter 40, respectively, and an OR gate 78 for inputting the output signals thereof.

Reference numeral 80 denotes a luminance signal output circuit, which is a duty selection circuit 4
An AND gate 82 for inputting the signal from the OR gate 78 in 8 and the write signal LIG, and an OR gate 84 for inputting an inverted output signal thereof and the write signal LIG.
An AND gate 86 that inputs the output signal and the lighting signal and applies the signal I to the display driver 14 is configured.

Next, the operation of the brightness adjusting circuit having the above structure will be described with reference to FIGS.

First, as shown in FIG. 2, the accessory switch 1
8 is off, its output signal ACC is at L level, and the brightness adjustment signal output circuit 24 is inactive, its output signal ILL.
Is at the L level, the light switch 22 is in the off state and the output signal LIG is at the L level, and when the external switch 20 is turned on, the operation signal SWA rising to the H level is the lighting signal output from the OR gate 32. It occurs only in J.

The H-level lighting signal J is applied to the electrode 16b of the display unit 16.
AND gate 86 applied to the
Output signal I and is applied to the display driver 14.

As a result, the display driver 14 applies a signal to each electrode 16a based on the code signal indicating the time from the decoder 12 to turn on the display unit 16.

On the other hand, as shown in FIG. 3, when the brightness adjustment signal output circuit 24 is operated by an external operation and the brightness adjustment signal ILL output from the circuit becomes H level, the counter 40 is released from reset and starts counting. When the counter 40 operates and a signal indicating the count value is generated at its outputs Q _{0 to} Q ₃ , the output signals B to D and the signal E of the AND gates 42 to 46 are 1/16, 1/8, 1 /, respectively. A pulse signal with a duty ratio of 4 1/2 is generated.

At this time, the counter 58 is not operating and the output signals F to H of the AND gates 62 to 66 are kept at L level.

Therefore, the AND gate 7 for inputting these signals F to H
0, 74 and 76 are closed.

If the light switch 22 is turned on here,
The AND gate 72, which receives the H-level signal from the NAND gate 68 for inputting the signals F to H and the H-level write signal LIG, is opened. Therefore, the signal C having a duty ratio of 1/8 is generated only at the output of the AND gate 72 and applied to the AND gate 86 via the OR gate 78, the AND gate 82, and the OR gate 84.

Here, when the accessory switch 18 is in the ON state, the lighting signal J is in the H level and the AND gate 86 is in the open state.

Therefore, a pulse having a duty ratio of 1/8 is generated in the output signal I of the AND gate 86, and the display unit 16 is driven by the display driver 14 at the brightness corresponding to this pulse.

In this way, when the brightness adjustment signal output circuit 24 outputs the H level brightness adjustment signal ILL, the display unit 16 is lit at a predetermined brightness. Note that the external operation of the brightness adjustment signal output circuit 24 is stopped and the output signal ILL is output.
Goes to the L level, the counter 40 for inputting it returns to the reset state again, and the signals B to H go to the L level.

Therefore, the pulse generated in the output signal I of the AND gate 86 is also stopped, and the display unit 16 is turned off.

Next, as shown in FIG. 4, when the accessory switch 18 and the light switch 22 are turned on as described above and the brightness adjustment signal output circuit 24 outputs the H level brightness adjustment signal ILL, as shown in FIG. When the switch 20 is turned on, the duty selection start signal output from the AND gate 36 which is already in the open state becomes H level.

As a result, the AND gate 50 is opened, and the clock signal φ ₂ is generated at its output.

This clock signal φ ₂ is generated in the output signal A of the AND gate 52 which is also in the open state, and the counter 5
8 to clock input C.

This counter 58 generates a clock signal φ generated on the signal A.
Counting is started in synchronization with ₂ , and the outputs Q ₀ and Q ₁ are set to H level according to the count value.

For this reason, the output signals F to H of the AND gates 62 to 66 to which the signals from the outputs Q ₀ and Q ₁ are input sequentially become H level at regular intervals, and all become L level. return.

Therefore, AND gates 70, 74, 76 and 72 for inputting the signals F to H and the output signal of the NOR gate 68, respectively.
Are sequentially opened and the signals B, D, E and C are output at their outputs.
The signals are generated in this order.

These signals are output signals I of the AND gate 86 via the OR gate 78, the AND gate 82 and the OR gate 84.
Occurs in.

As a result, until the external switch 20 is turned on, the display unit 16 which has been lit with the brightness corresponding to the signal C having the duty ratio of 1/8 has a duty ratio of 1/16, 1/4,
The brightness is switched to 1/2 and 1/8 in this order at a constant interval.

Here, when the signal H is at the H level and the signal E is generated at the output of the AND gate 76, if the external switch 20 is returned to the OFF state, the duty selection start signal becomes the L level, and the AND gates 50, 52. Is closed.

Therefore, the signal A becomes L level, and the counter 58 stops with the count value at this point. As a result, the state in which the signal H is at the H level and the signal E is generated at the output of the AND gate 76 is maintained as it is.
Will be driven with the brightness corresponding to the signal with a duty ratio of 1/2. After that, when the brightness adjustment signal ILL becomes L level, the light switch 22 is turned off and the write signal LIG becomes L level, as described above, the pulses generated in the signals B to E stop, and The output signal of the OR gate 84 becomes H level, and the AND gate 86
Output signal I is maintained at H level.

Therefore, the display unit 16 lights up regardless of the selected brightness.

Further, when the brightness adjustment signal output circuit 30 and the light switch 22 are operated again in this state, the display unit 16
Will be driven at the selected brightness.

As described above, the external switch 20 in this embodiment has the display unit 16 when the accessory switch 18 is in the off state.
, And also as a switch for switching the duty ratio of the drive pulse that determines the brightness of the display section 16 when the accessory switch 18 and the light switch 22 are in the ON state.

(Effect of the Invention) According to the present invention, the external switch for turning on the display part of the timepiece is also used as the switch for adjusting the brightness of the display part of the timepiece. The brightness can be adjusted independently.

In particular, the range of this adjustment is wide because the duty ratio of the pulse for driving the display can be selected to 1/2, 1/4, 1/8, 1/16, and the external switch is turned on. By doing so, the duty ratio is periodically selected, so that the operability is excellent.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a brightness adjusting circuit for an automobile timepiece according to an embodiment of the present invention, and FIGS. 2 to 4 are time charts of signals in FIG. 2 ... Timer circuit, 10 ... Display circuit, 16 ... Display section, 18 ... Accessory switch, 20 ... External switch, 22 ... Light switch, 24 ... Brightness adjustment signal output circuit, 32 ... Switch switch Circuit, 38 ... duty generation circuit, 48 ... duty selection circuit, 80 ... luminance signal output circuit.

Claims (1)

[Scope of utility model registration request] 1. A clock circuit for clocking time, a display circuit for outputting a display signal based on a clock signal output from the clock circuit, a display section for displaying time based on the display signal, and an external operation. A possible accessory switch, an external switch that lights the display unit when the accessory switch is in an off state, a light switch that lights the instrument illumination provided on the instrument panel, and an instrument switch provided on the instrument panel A brightness adjustment signal output circuit for outputting a brightness adjustment signal for adjusting the brightness of the illumination of the instrument, and a brightness adjustment circuit for an automobile timepiece comprising: an external switch from the external switch when the accessory switch is in an off state. The lighting signal is output in response to the operation signal of and the lighting signal is output when the accessory switch is in the ON state. And a switch switching circuit that outputs a duty selection start signal in response to the operation signal, and pulse groups having different duty ratios in response to the brightness adjustment signal and the first clock signal from the timing circuit. A duty generating circuit, and a pulse of a different duty ratio output from the duty generating circuit in response to the duty selection start signal when the light switch is on, synchronized with a second clock signal from the timing circuit. A duty selection circuit that outputs the pulse of the duty ratio selected when the duty selection start signal is stopped, and the pulse output by the duty selection circuit and the lighting signal from the switch switching circuit. Luminance signal selected by the display circuit in response to the signal from the light switch A luminance signal output circuit for applying a voltage, and a luminance adjustment circuit for an automobile timepiece, which is provided.