JPS6136953Y2 - - Google Patents

Description

[Detailed description of the invention] The invention is capable of automatically keeping the illuminance of the watch's illumination device constant regardless of fluctuations in the power supply voltage value, and the illuminance control mechanism is completely built into an integrated circuit. The present invention relates to a lighting device for a watch that is configured to be illuminated.

Conventionally, the illuminance of a lighting device for a watch that uses a battery as a power source depends on the voltage value of the power source battery. Therefore, when the power supply battery is new and has a high voltage value, the illuminance of the lighting device may be unnecessarily bright, and when the power supply voltage value decreases, the time display may become difficult to see.

In order to solve these problems, it is conceivable to increase the resistance value when the voltage value is high, and to decrease the resistance value when the voltage value decreases. To this end, it is conceivable to attach a variable resistor to the illumination lamp that illuminates the time display section and vary the resistance value, but this would require the user to make adjustments each time. It takes time and effort. In addition, in order to save time and effort, multiple resistors are arranged, and an electronic switch selects a number of resistors whose resistance value can maintain a constant current value according to the voltage of the power supply battery, and the current flows through the resistors. It is also conceivable to adopt a configuration in which the water flows into the illumination lamp. In this way, the illuminance can be kept constant without the user having to operate it one by one, but the number of parts increases and it is difficult to integrate the device into an integrated circuit. In recent years, clock circuits have become increasingly integrated, and attaching multiple resistors externally has been extremely problematic in terms of manufacturing and cost.

The present invention has been devised in view of the above-mentioned conventional problems, and its purpose is regardless of fluctuations in power supply voltage.
The objective is to keep the illumination intensity constant and to enable such an illumination control mechanism to be completely built into an integrated circuit.

In order to achieve the above object, the present invention includes a power supply voltage detection means capable of detecting a plurality of different power supply voltage values, and a plurality of MOSFETs whose one end is connected to a power supply and the other end is connected to a lighting circuit. It is configured to supply current to the lighting circuit via the on-resistance of the MOSFET, and increases the on-resistance when the power supply voltage detection means detects a high voltage value, and increases the on-resistance when a low voltage value is detected. It is characterized by the addition of an illuminance control circuit that maintains a constant current flowing through the illumination circuit by decreasing the value.

The present invention will be described in detail below based on preferred embodiments.

FIG. 1 is a circuit diagram showing an embodiment of the present invention. The reference signal generator 2, the frequency dividing circuit 4, the clock circuit 6, the decoder/driver 8, and the display section 10 constitute a clock circuit.

The power supply voltage detection circuit 12 is a circuit that detects the voltage value of a power supply battery (not shown).
When the voltage is 1.5V or more, only the signal on the output line 14 becomes a high potential (hereinafter referred to as H), and the other output lines 16,
Signals 18, 20, and 22 are configured to have a low potential (hereinafter referred to as L). Furthermore, when the battery voltage is 1.49V to 1.40V, only the signal on the output line 16 becomes H, when the battery voltage is 1.39 to 1.30V, only the signal on the output line 18 becomes H, and when the battery voltage is 1.29V to 1.20V, the output line 16 signal becomes H. The configuration is such that only the signal of the output line 22 becomes H when the voltage is 1.19 to 1.10V.

The lighting control circuit 24 includes MOSFETs 26, 28, 3
0 and AND gates 32, 34, and 36.
The drains of MOSFETs 26, 28, and 30 are normally H
signal is applied, and the source is connected to the lighting circuit 40 via the output line 38. And MOSFET2
The output line 42 of the AND gate 32 is connected to the gate of MOSFET 6, and the output line 44 of the AND gate 34 is connected to the gate of MOSFET 28.
The output line 46 of the AND gate 36 is connected to the gate of 0. This and gate 32, 34, 36
A power supply voltage detection circuit 1 is connected to one of the inputs of each
Two output lines 14, 16, and 18 are connected.
Further, an output line 54 of a lighting switch circuit 52 composed of a switch 48 and a flip-flop 50 is connected to the other inputs of the AND gates 32, 34, and 36.

The lighting control circuit 24 also includes MOSFETs 58 and 6.
0, 62, and gate 66, nand gate 6
8, 70, 72, inverters 74, 76, and an OR gate 78. And gate 64,
79 constitutes a blinking circuit 77 that outputs a signal to blink the illumination. Normally, an H signal is applied to the drains of MOSFETs 58 and 60, and the sources are connected to the output line 38 along with the drain of MOSFET 62.
It is connected to the lighting circuit 40 via. this
An output line 80 of a NAND gate 68 is connected to the gate of the MOSFET 58 via an inverter 74. The output line 82 of the flip-flop 79, the output line 54 of the lighting switch circuit 52, and the output line 20 of the power supply voltage detection circuit 12 are connected to the input of the NAND gate 68.

The gate of the MOSFET 60 is connected to an output line 84 of the NAND gate 70 via an inverter 76. The inputs of the NAND gate 70 are connected to an output line 86 of the AND gate 64 and a line connected to the power supply voltage detection circuit 1.
The input of the AND gate 64 is connected to the output line 22 of the flip-flop 79. The input of the AND gate 64 is connected to the output line 82 of the flip-flop 79 and to the constant period signal 88 from the frequency divider circuit 4. The constant period signal 88 from the frequency divider circuit 4 is also applied to the input φ of the flip-flop 79.

AND gate 66 for the gate of MOSFET62
An output line 90 is connected thereto. The output line 84 of the NAND gate 70 is connected to the input of the AND gate 66.
, the output line 80 of the NAND gate 68, and the output line 92 of the NAND gate 72 are connected. The output line 54 of the lighting switch circuit 52 and the output line 93 of the OR gate 78 are connected to the input of the NAND gate 72, and the output line 14 of the power supply voltage detection circuit 12,
16 and 18 are connected. Among these, AND gate 32, 34, 36, 66, NAND gate 6
8, 70, 72, inverters 74, 76, and OR gate 78, MOSFET 26,
A control gate circuit 56 is configured to turn on any one of 28, 30, 58, and 60.

The lighting circuit 40 includes an amplification transistor 9
4 and an illumination lamp 96.

FIG. 2 is a circuit diagram of the power supply voltage detection circuit 12. The power supply voltage detection circuit 12 includes resistors 98 and 100 connected in series, and an inverter 1 connected in series.
02a, 102b, 104a, 104b, 1
06a, 106b, 108a, 108b, 1
10a, 110b and AND gates 112, 11
4, 116, 118, 120.

A power supply battery (not shown) is connected in parallel to the series-connected resistors 98 and 100, and when the voltage of the battery is 1.5V or higher, only the signal on the output line 122 of the inverter 102b becomes L; The signals on the output line 124 of the other inverter 104b, the output line 126 of the output line 106b, the output line 128 of the output line 108b, and the output line 130 of the output line 110b become H. When the voltage of the battery is 1.49 to 1.40V, only the signals on the output lines 122 and 124 are L, and when the voltage is 1.39 to 1.30V, the signals on the output lines 122, 124, and 126 are L, and 1.29
~1.20V output lines 122, 124, 126,
The signal of 128 becomes L, and when the voltage is 1.19 to 1.10V, all the signals of output lines 122, 124, 126, 128, and 130 become L. Therefore, the output line 122,
The output line 14 of the AND gate 112 to which 124, 126, and 130 are connected is connected to the voltage of the power supply battery.
An H signal is generated only when the voltage is 1.5V or higher, and the voltage is not present on the output line 16 of the AND gate 114 to which the output lines 124, 126, 128, and 130 are connected.
An H signal is generated only when the voltage is between 1.49 and 1.40V. Similarly, the output line 18 of the AND gate 116 to which the output lines 126, 128, and 130 are connected has a voltage.
AND gate 1 generates an H signal only when the voltage is between 1.39 and 1.30V, and output lines 128 and 130 are connected.
An H signal is generated on the output line 20 of No. 18 only when the voltage is 1.29 to 1.20V. Furthermore, a signal that becomes H is generated on the output line 22 of the inverter 120 to which the output line 130 is connected only when the voltage is between 1.19V and 1.10V.

The operation of the circuit shown in FIG. 1 will be explained below.

Normal MOSFET26, 28, 30, 58, 60
is off, and MOSFET 62 is on. Here, when the user presses the switch 48 of the lighting switch circuit 52 and the constant periodic signal 132 applied to the input φ of the flip-flop 50 rises, the signal on the output line 54 changes from L to H. In this state, if the power supply voltage is 1.5V or higher, only the signal on the output line 14 of the power supply voltage detection circuit 12 becomes H. As a result, only the signal on the output line 14 of the AND gate 32 becomes H, and MOSFET 2
6 turns on. At this time, the signal on the output line 93 of the OR gate 78 is H, and the signal on the output line 54 is also H, so the output line 92 of the NAND gate 72 becomes L, turning off the MOSFET 62. As a result, the current is input to the amplifying transistor 94 of the lighting circuit 40 via the on-resistance of the MOSFET 26, and the lighting lamp 96 is turned on.

When the voltage of the power supply battery reaches 1.49 to 1.40V, only the signal on the output line 16 of the power supply voltage detection circuit 12 becomes H. As a result, output line 4 of AND gate 34
Only the signal of 4 goes from L to H, and MOSFET28
turns on. As a result, current flows to the lighting circuit 40 via the on-resistance of the MOSFET 28, and the lighting lamp 96 is turned on.

When the voltage of the power supply battery reaches 1.39 to 1.30V, only the signal on the output line 18 of the power supply voltage detection circuit 12 becomes H. As a result, output line 4 of AND gate 36
Only the signal of 6 changes from L to H, and this time
MOSFET30 turns on. As a result, the current
The light flows to the lighting circuit 40 via the on-resistance of the MOSFET 30, and the lighting lamp 96 is turned on.

When the voltage of the power supply battery reaches 1.29 to 1.20V, only the signal on the output line 20 of the power supply voltage detection circuit 12 becomes H. Here, since the output line 82 of the flip-flop 79 is applied with a signal with a duty ratio of 50%, which is obtained by dividing the constant period signal 88 from the frequency divider circuit 4 by 1/2, the output line 80 of the NAND gate 68 is applied with a signal having a duty ratio of 50%. A signal on output line 82 is obtained. In this state, the signal on the output line 93 of the OR gate 78 becomes L, so the output line 92 of the NAND gate 72 becomes H, and the signal on the NAND gate 70 continues to be H, so the output line 90 of the AND gate 66 shows the output of the NAND gate 68. A signal that is in phase with line 80 is obtained. Therefore, when the output line 80 of the NAND gate 68 becomes L, the MOSFET 62 is turned off and the MOSFET
The signal on the output line 80 is inverted by the inverter 74 and applied to the gate of the MOSFET 58.
58 is turned on. As a result, the current is MOSFET58
The light flows to the lighting circuit 40 via the on-resistance of , and the lighting lamp 96 lights up. Conversely, when the signal on the output line 80 of the NAND gate 86 becomes H, the MOSFET 62 is turned on, and an L signal is applied to the gate of the MOSFET 58 by the inverter 74.
8 is off. As a result, no current flows through the illumination circuit 40, so the illumination lamp 96 is turned off.
Thereafter, the above operation is repeated every time the signal on the output line 82 becomes H or L, and the illumination lamp 96 blinks.

When the voltage of the power supply battery reaches 1.19 to 1.10V, only the signal on the output line 22 of the power supply voltage detection circuit 12 becomes H. Here, the output line 8 of the AND gate 64
6 has a constant period signal 90 and a flip-flop 79.
When the signals on the output lines 88 of the NAND gate 70 are both high, a signal with a duty ratio of 25% is generated by dividing the constant period signal 90 by 1/2, so the output line 84 of the NAND gate 70 has an inverted Output line 8
6 signals are obtained. In this state, the output line 92 of the NAND gate 72 becomes H as before, and the signal on the output line 80 of the NAND gate 68 also becomes H, so the output line 90 of the AND gate 66 receives a signal that is in phase with the output line 84 of the NAND gate 70. is obtained.
Therefore, when the signal on the output line 84 becomes L,
MOSFET 62 is turned off, and an H signal is applied to the gate of MOSFET 60 by inverter 76, so MOSFET 60 is turned on. As a result, current flows to the lighting circuit 40 via the on-resistance of the MOSFET 60, and the lighting lamp 96 is turned on. Conversely, when the signal on the output line 84 becomes L, the MOSFET 62
turns on and MOSFET 60 turns off. As a result, no current flows through the lighting circuit 40, and the lighting lamp 96 is turned off. Thereafter, the above operation is repeated until the signal on the output line 86 becomes H or L, and the illumination lamp 96 blinks.

Figure 3 shows MOSFET 2 when the power supply voltage is constant.
6, 28, 30, 58, and 60 and a characteristic diagram showing the relationship between the on-resistance values and the current flowing through the output line 38, where R shows the resistance value and I shows the current value. As shown in Figure 3, MOSFET26, 28, 30, 58, 6
If the on-resistance value of 0 is set to gradually decrease, when the voltage of the power supply battery decreases, the current flowing into the base of the amplification transistor 94 of the lighting circuit 40 through the output line 38 will increase. .
Therefore, due to the decrease in battery power, the lighting lamp 9
6 can be prevented from decreasing, and conversely, when the voltage is high, excessive current can be suppressed from flowing into the lighting lamp 96. As a result, the illuminance of the lighting lamp 96 can be maintained regardless of fluctuations in the power supply voltage. . It becomes a constant and appropriate value.

FIG. 4 is a waveform diagram showing signals on output lines 82 and 86. As mentioned above, the voltage of the power supply battery is
When the voltage is 1.29 to 1.20V, the illumination lamp 96 lights up only when the signal on the output line 82 becomes H, and the voltage is 1.19V.
When the voltage drops to ~1.10V, the illumination lamp 96 lights up only when the signal on the output line 86 goes high. As a result, the voltage of the power supply battery decreases to 1.29~
It can be seen that when the voltage reaches 1.20V, the lighting time becomes 50% of that when the voltage is 1.3V or higher, and when the voltage becomes 1.19 to 1.10V, it becomes 25%. As described above, according to the present embodiment, by flashing the lighting when the voltage of the power battery decreases, consumption of the power battery due to lighting is reduced, and the user is notified that the battery life has reached the end. Can be done.

In this example, when the life of the power supply battery reaches the end of its life and the voltage drops to a certain value, the lighting time is shortened by switching on the flashing lighting, but the lighting time is shortened by turning off the lights after lighting for a certain period of time. It is also possible to do so.

As described above, according to the present invention, the current flowing through the illumination lamp can be kept constant even if the power supply voltage value fluctuates, so that the illuminance can be kept constant. Moreover, this illuminance control means has multiple
Since it has a MOSFET and the on-resistance value of this MOSFET changes in proportion to the voltage value, there is no need to add an external resistor as in the past, making it easy to integrate and manufacture. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. FIG. 2 is a circuit diagram showing the power supply voltage detection circuit in FIG. 1. FIG. 3 is a characteristic diagram showing the relationship between the on-resistance value of the MOSFET and the current flowing through the output line 38 when the power supply voltage is constant. FIG. 4 is a waveform diagram showing signals on output lines 82 and 86. 12...Power supply voltage detection circuit, 24...Lighting control circuit, 26, 28, 30, 58, 60...
MOSFET, 40...Lighting circuit, 52...Lighting switch circuit, 56...Control gate circuit, 96...
lighting lamp.

Claims (1)

[Scope of utility model registration request] A lighting device for a watch having a lighting circuit including a lighting lamp that illuminates a time display section by operation of a lighting switch, comprising a power supply voltage detection means for detecting a plurality of different power supply voltage values, one end of which is connected to a power supply terminal, and the other end of which is connected to a power supply terminal. is connected to the lighting lamp of the lighting circuit, and the plurality of MOSFETs each having a different on-resistance and the power supply voltage detection means gradually detect a lower voltage value.
and a control gate circuit that outputs a signal to select and turn on the MOSFET.
1. A lighting device for a watch, comprising: lighting control means for keeping illuminance constant by keeping constant current supplied to the lighting lamp in the lighting circuit via a MOSFET.