JPS6359475B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic device containing a battery, and more particularly to a pressure reducing circuit for reducing the voltage of the battery and supplying the voltage. Most of the electronic devices with built-in batteries currently on the market, especially the electronic clocks that represent electronic devices, use the natural oscillation frequency of a crystal oscillator as the time reference source, and the signal is composed of dividers, counters, decoders, drivers, etc. The CMOS integrated circuit provides time signals and other information, which is transmitted to the display and displayed. A silver battery is used as the energy source for its operation. This silver battery is used in the range of 1.4~1.6V and has a current capacity of 100~
The 150mAH battery is most commonly used and has a battery life of 2 to 3 years. Recently, there has been a demand for thinner batteries from a design standpoint, and for longer battery life from an ease of use standpoint. As a countermeasure, efforts are being made to incorporate solar cells to make them semi-permanent, and to develop high-density batteries such as lithium batteries. Although lithium batteries have several times the electrical capacity of conventional silver batteries, they have the disadvantage that they require about twice as much power as silver batteries.

Figures 1 and 2 show circuit block diagrams of an electronic timepiece using a silver battery, and Figures 3 and 4 show circuit block diagrams of an electronic timepiece using a lithium battery to explain the conventional method. 1 is a block diagram of a pointer type timepiece using a silver battery, and is composed of an oscillation circuit 1, a frequency dividing circuit 2, a driver circuit 3, a step motor 4, a wheel train 6, hands 6, and a silver battery 7.
A voltage of 1.4 to 1.6 V is supplied from the silver battery 7 to the oscillation circuit 1, the frequency divider circuit 2, and the driver circuit 3, the oscillation circuit 1 oscillates at its natural frequency, and the signal is divided by the frequency divider circuit 2. , the step motor 4 is driven by the driver circuit 3 and moves once per second. The rotational movement of the step motor 4 is transmitted to the needle 6 through the wheel train 5. Assuming that the current consumed by the oscillation frequency division is 3μA, and the current consumed by the step motor is 3μA, for a total of 6μA, the current will be 100mAH.
The battery life is about 2 years using 2 batteries.

Figure 2 is a block diagram of a liquid crystal display type watch using a silver battery, including an oscillation circuit 8, a frequency division circuit 9, a frequency division circuit 10, a counter circuit 11, and a decoder circuit 1.
2, a driver circuit 13, a display 14, a booster circuit 15, and a silver battery 16. . 1.4~ directly from the silver battery 16 to the oscillation circuit 8 and frequency divider circuit 9
1.6V battery voltage is supplied, and booster circuit 1
The voltage 2.8 to 3.2V boosted by 5 is applied to the frequency divider circuit 10, the counter circuit 11, and the decoder circuit 1.
2. Driver circuit 13 is supplied. Oscillation circuit 8
The signal of the natural frequency caused by the oscillation of
The frequency is divided by 0 and passed through the counter circuit 11, decoder circuit 12, and driver circuit 13 to the display body 1.
Sent to 4. If we assume that the current consumed by 1.5V system oscillation frequency division is 3μA, the current consumed after 3V system frequency division is 0.5μA in 1.5V terms, and 2.5μA for the lamp, the battery life of a 100mAH battery is approximately It's been 2 years.

The case where a lithium battery is used is shown in FIGS. 3 and 4. FIG. 3 is a block diagram of a pointer type timepiece similar to FIG.
1. Consists of a needle 22 and a lithium battery 62. In this case, a voltage of 2.8 to 3 V from the lithium battery 62 is supplied to the oscillation circuit 17, the frequency dividing circuit 18, and the driver circuit 19. Therefore, even if the capacity of a lithium battery is three times that of a silver battery, if the same circuit as shown in Figure 1 is used and the same amount of battery power is consumed, the battery life will only be 1.5 times that of a silver battery. It won't happen. Moreover, when the voltage is raised to operate the IC, the current consumed usually increases, and even if the capacity of a lithium battery is several times that of a silver battery, the effect will be lost. On the other hand, the liquid crystal display type watch whose block diagram is shown in FIG.
5, decoder circuit 26, driver circuit 27,
It is composed of a display body 28 and a lithium battery 29. In this case, the voltage of 2.8 to 3.0V of the lithium battery is applied to the oscillator circuit 23, the frequency divider circuit 24, and the counter circuit 2.
5. It is supplied to the degauder circuit 26 and the driver circuit 27. In this case, the oscillation circuit 8 in FIG.
Since a voltage of 2.8 to 3.0V is applied to the oscillation circuit 23 and frequency division circuit 24 in FIG.
If you calculate this, it will consume more than 6μA of current, which is a huge waste of money.

The present invention has been made to improve the above-mentioned drawbacks, and an object of the present invention is to extend battery life by supplying reduced pressure battery voltage to part or all of an electronic circuit. Another object of the present invention is to use a differential amplifier circuit in a pressure reduction circuit of an electronic device and supply a reference voltage to one of the differential inputs, thereby making it possible to supply a reduced voltage of any level corresponding to the reference voltage. At the same time, the present invention aims to reduce current consumption by performing a sampling operation on the pressure reducing circuit. Another object of the present invention is to stably supply battery voltage from a pressure reducing circuit when the battery is turned on, thereby stabilizing the electronic circuit quickly and reliably.

The present invention will be described below with reference to FIGS. 5 and 7 showing block diagrams of a pointer type timepiece, and FIGS. 6 and 8 showing block diagrams of a liquid crystal display type timepiece. Fifth
The voltage of the lithium battery 37 as shown in the figure
The voltage of 2.8 to 3.0 V is reduced to 1.4 to 1.6 V by a pressure reducing circuit 36 and supplied to the oscillation circuit 30, the frequency dividing circuit 31, and the driver circuit 32. The efficiency when depressurizing is approximately
If it is 100%, the life will be about twice as long as when supplying 2.8 to 3.0V as is, and if the capacity of a lithium battery is three times that of a silver battery with the same volume, then 3.
With double the lifespan, a watch that lasts three years with a silver battery will last nine years with a lithium battery.

FIG. 6 is a block diagram of a liquid crystal display type watch.
The voltage of the lithium battery 45 as shown in FIG.
The voltage from 2.8 to 3.0 V is reduced to 1.4 to 1.6 V by a pressure reducing circuit 44 and supplied to the entire oscillation circuit 38, frequency dividing circuit 39, counter circuit 40, decoder circuit 41, and driver circuit 42. In this case, if the lamp is not taken into consideration, the lifespan will be approximately twice as long as that of the system shown in FIG. 4, and approximately three times as long as that of the system using silver batteries as shown in FIG.

FIG. 7 is another block diagram of the pointer type timepiece.
Voltage 2.8 to 3.0V of lithium battery 54 is reduced by pressure reducing circuit 5
3, the voltage is reduced to 1.4 to 1.6 V and supplied to the oscillation circuit 46 and the frequency dividing circuit 47, and 2.8 to 3.0 V is directly supplied to the frequency dividing circuit 48 and the driver circuit 51.

FIG. 8 is another block diagram of the liquid crystal display type timepiece. The voltage of 2.8 to 3.0 V of the lithium battery 64 is reduced by the pressure reducing circuit 63 and supplied to the oscillation circuit 55 and the frequency dividing circuit 56, the frequency dividing circuit 57, and the counter circuit 5.
8. 2.8 to 3.0V is directly supplied to the decoder circuit 59 and driver circuit 60.

In the block diagrams of FIGS. 7 and 8, the frequency divider circuit is divided into two groups and each is driven by a reduced voltage and a battery voltage. There are various variations of FIG.
A modification of FIG. 7 is to drive the oscillation circuit and frequency divider circuit with a reduced voltage, and drive the driver circuit with battery voltage. Further, as a modification of FIG. 8, the oscillation circuit and the frequency divider circuit are driven with a reduced voltage, and the counter circuit, decoder circuit, and driver circuit are driven with battery voltage, or the oscillation circuit,
The frequency divider circuit and counter circuit are driven by reduced voltage,
For example, the decoder circuit and driver circuit are driven by battery voltage, the oscillation circuit, frequency dividing circuit, counter circuit, and decoder circuit are driven by reduced voltage, and the driver circuit is driven by battery voltage.

In either example, the battery voltage is supplied at a reduced pressure to part or all of the electronic circuit, thereby reducing current consumption and extending the life of the battery.

FIG. 8 shows one embodiment of a pressure reducing circuit according to the present invention, in which a capacitive element 77 and a MOS transistor 7 are shown.
8 and 81 to 91 and voltage dividing elements 79 and 80. The voltage dividing elements 79 and 80 divide the battery voltage of a lithium battery 92 which is a driving source, and together with a MOS transistor 81 which controls this voltage dividing operation, constitute a voltage dividing circuit which becomes a reference voltage source. Furthermore, MOS transistors 82 to 89
is a differential amplifier circuit that uses a voltage divided by a voltage dividing circuit as a reference. This differential amplifier circuit consists of a MOS transistor 8 whose gate receives a divided voltage.
6 and a MOS transistor 87 whose gate is connected to the output terminal of the reduced voltage; load MOS transistors 88 and 89 connected in series to this transistor pair; current source that supplies current
It consists of a bias circuit consisting of a MOS transistor 85 and further MOS transistors 82, 83, and 84 that form a reference voltage serving as a gate bias voltage of this MOS transistor. The MOS transistors 78, 90, 91 and the capacitor 77 constitute a current source circuit A, and the MOS transistor 78 is a MOS transistor whose gate is supplied with the output of the differential amplifier circuit. A reduced voltage is obtained from the connection point of the element 77.

A timing chart of the signals ψ and φ in FIG. 9 is shown in FIG. 11. , are respectively ψ,
It is an inverted signal of φ, and ● indicates a logical product.
The sampling signal φ is generated by a timing signal from an electronic clock circuit when the battery is connected and the voltage is fixed. ψ is a signal that remains high for a while (can be set between several seconds to several minutes) after the battery is inserted, and during this high state, the MOS transistors 81 and 84 are off. Therefore, no current flows in the voltage divider circuit or bias circuit, and the current source
Since the MOS transistor 85 is also in the off state,
The pressure reducing circuit does not work. Furthermore, the current source circuit MOS
MOS for controlling conduction of transistor 78
The transistor 91 is turned on and the transistor 90 is turned off, a high control signal is supplied to the gate of the current source MOS transistor in place of the output signal of the differential amplifier circuit, the current source MOS transistor 78 is turned on, and the battery is supplied to the electronic clock circuit. This is because the characteristics of the oscillation circuit are not stable for a while after the battery is inserted, so the battery voltage is supplied only during this time. In addition, a large amount of current is consumed when outputting a lamp in a liquid crystal display type electronic watch, alarm, buzzer, voice, etc. Therefore, due to the internal resistance of the battery, the battery voltage and the voltage reduced by the pressure reducing circuit are used as a fixed value. The operation of the clock circuit becomes unstable. ψ is then used as a signal to supply the battery voltage instead of the reduced voltage. Next, when the operation of the electronic clock circuit becomes stable and ψ becomes low, the pressure reducing circuit starts operating. The differential amplifier circuit inputs the divided voltage from the voltage dividing circuit and the voltage at the output terminal, and operates so that the voltage at the output terminal becomes equal to the divided voltage. However, since the differential amplifier circuit has a current path between the power supplies and has the disadvantage of increasing current consumption, here, the pressure reducing circuit is operated when the signal φ is high. Therefore, when φ is high, the differential amplifier circuit charges the capacitive element 77 until V _SS becomes equal to the divided voltage, and when φ is low, the current source MOS transistor 78 does not supply current. This capacitive element 77
The electric charge stored in the circuit is gradually discharged by the electronic clock circuit. During this discharge, the MOS transistor 9
0 turns on, turns off the current source MOS transistor 78, and the reduced voltage is reliably supplied.

In other words, the capacitive element included in the current source circuit A always outputs a stable reduced voltage even when the pressure reducing circuit performs sampling operation.

In this pressure reducing circuit, voltage dividing elements 79, 80
By selecting the element value of , the terminal voltage (V _DD -
V _SS ) 1.4~1.6V is taken out. As this voltage dividing element, each pair of resistors (diffusion resistor, ion implantation resistor, polysilicon resistor, etc.), diode, transistor, and capacitor (insulating film capacitor, etc.) are used.

FIG. 10 shows another embodiment of the pressure reducing circuit according to the present invention, in which a capacitive element 93 and a MOS transistor 9
4 to 110. MOS transistors 101 to 108 constitute a differential amplifier circuit, and MOS transistors 94, 109, 110 and capacitive element 93 constitute a current source circuit A. The above circuit is the same as that shown in FIG.

Figure 10 shows that instead of the voltage divider circuit in Figure 9,
A reference voltage source circuit consisting of MOS transistors 95 to 100 is used. This reference voltage source circuit sets the threshold voltages of MOS transistors 96 and 98 to be equal, and determines the ratio of the conductance coefficients of MOS transistors 96 and 97 and the ratio of the conductance coefficients of MOS transistors 96 and 97.
After setting the ratio of the conductance coefficients of MOS transistors 8 and 99 to be equal, the threshold voltages of MOS transistors 97 and 99 are made different, and MOS transistor 97 is connected to the gate of MOS transistor 105 of the differential amplifier circuit.
The voltage that is the difference between the threshold voltages of and 99 is output as a reference voltage. By setting this threshold voltage, a terminal voltage (V _DD -V _SS ) of 1.4 to 1.6V is taken out.

Here, in the MOS transistors 95 and 97,
φ and MOS transistor 100 are applied to the gate, and MOS transistors 97 and 100 are turned off for a while after the battery is inserted, and do not operate as a reference voltage source. Also, ψ
Even after becomes low, it only operates when φ is high.

Therefore, the battery voltage, not the reduced voltage, is supplied to the electronic clock circuit from the V _SS terminal until the circuit stabilizes after the power is turned on, and after the voltage reduction starts, the voltage of the difference between the threshold voltages is stabilized as the reduced voltage. The pressure reducing circuit operates as supplied.

MOS transistor 97 in this FIG.
The threshold voltage difference of 99 is formed by implanting ions into one of the channels of 97 and 99 (channel doping) and changing the threshold voltage depending on the amount of implanted charge.

The gate material of one of 97 and 99 is changed, and the threshold voltage shift amount is determined by the work function difference.

Note that the feedback from the V _SS terminal to the differential input transistor can also be divided by a voltage dividing element connected between V _DD and V _SS and then fed back.

The gist of any of the embodiments of the pressure reduction circuit is that the pressure reduction circuit is formed of elements formed on the same semiconductor integrated circuit board as the capacitive element and the electronic circuit. In particular, it is important to integrate electronic circuits on CMOS integrated circuits in order to reduce the cost of electronic devices.

FIG. 12 shows a circuit that generates a signal ψ for selectively using a battery voltage or a reduced voltage as a voltage to be supplied to an electronic circuit. The circuit shown in FIG. 12 will be explained with reference to the timing chart shown in FIG. 13. Potential of front capacity 142 without battery
A′ is at V _DD . When the battery is inserted, the MOS transistor 141 is turned on and A' becomes the potential of V _CC . The set/reset circuit is set by the inverted potential A, and ψ becomes _VDD . After a while, it is reset by timing signal C from the electronic circuit.
The potential V _DD is held until it reaches V _CC . Also, when a switch B for lamps, alarms, buzzers, audio, etc. is turned on, ψ becomes V _DD while B is at V _CC . Signals from the electronic circuit to the circuit shown in FIG. 12 undergo logic level conversion through an appropriate interface circuit if the electronic circuit is driven by a reduced voltage system. This interface circuit is also used to convert the logic level of signal transmission between an electronic circuit driven by a reduced voltage system and an electronic circuit driven by a battery voltage system. This interface circuit is shown in FIG. The reduced voltage (V _DD - V _SS ) system signal α is changed to the logic level of the battery voltage system (V _DD - V _CC ) by this interface circuit composed of MOS transistors 147 to 152, and the respective β, becomes.

In addition to the embodiments shown in FIGS. 9 and 10, the pressure reducing circuit includes various circuits combining capacitors, resistance diodes, and transistors, and methods using transformers.

As described above, a differential amplifier circuit that performs sampling operation is used in the pressure reducing circuit, a capacitive element is provided in the current source circuit that serves as the output, and a reduced voltage is always stably supplied.When the battery is inserted, the battery voltage is stably supplied from the pressure reducing circuit. According to the method of the present invention, when the battery is turned on, the battery voltage is reliably supplied from the current source MOS transistor, so the electronic circuit can operate stably at an early stage, and during normal operation, the battery voltage is reduced and supplied, so the lithium battery It is possible to effectively use high-density batteries with high output voltage, such as batteries. This results in a longer battery life, about three times longer than current silver batteries. The current 2-3 year battery life will now be 6-9 years, which is about the same as the average lifespan of a wristwatch. Furthermore, if emphasis is placed on the design aspect, it is possible to make the battery thinner and smaller. As an example of the present invention, a case has been described in which a lithium battery is used with the battery voltage reduced, but the present invention is equally effective for any battery. Furthermore, this concept of reducing the battery voltage and using it is applied to battery-powered watches as well as general electronic devices that use batteries as a driving source, such as calculators.

[Brief explanation of the drawing]

FIGS. 1, 2, 3, and 4 are block diagrams of conventional electronic timepieces. Figures 5, 6,
7 and 8 are block diagrams of an electronic timepiece according to the present invention. 9 and 10 show embodiments of a pressure reducing circuit for an electronic device according to the present invention. FIG. 11 is a timing chart of signals in each embodiment of the pressure reducing circuit. FIG. 12 is a diagram showing a signal ψ generating circuit in each embodiment of the pressure reducing circuit. Figure 13 is the first
Figure 2 is a timing chart for the circuit. FIG. 14 is a diagram showing an interface circuit for transmitting signals from the reduced voltage system to the battery voltage system. 1, 8, 17, 23, 30, 38, 46, 55
...Oscillation circuit, 2, 9, 10, 18, 24, 3
1, 39, 47, 48, 56, 57... frequency divider circuit, 3, 13, 19, 27, 32, 42, 49,
60...Driver circuit, 4, 20, 33, 50
...Step motor, 5, 21, 34, 51...
... Gear train, 6, 22, 35, 52... Needle, 7, 16
...Silver battery, 29, 37, 45, 54, 62, 6
4,92,111...Lithium battery, 11,2
5, 40, 58... Counter circuit, 12, 2
6, 41, 59...Decoder circuit, 14, 2
8, 43, 61...display body, 15...boost circuit,
36, 44, 53, 63... pressure reducing circuit, 77, 9
3,142...Capacity, 78,81~91,94~
110,141,147-152...MOS transistor, 79,80...Voltage dividing circuit, 143,1
46... Inverter circuit, 144, 145... NAND circuit, V _DD - V _SS ... Reduced voltage, V _DD -
V _CC ……Battery voltage.

Claims (1)

[Claims] 1. A pressure reducing circuit that supplies a reduced voltage obtained by reducing the battery voltage of a battery to an electronic circuit, and outputs a control signal to the pressure reducing circuit for causing the electronic circuit to supply the battery voltage for a predetermined period from the application of the battery voltage. In the electronic device, the pressure reduction circuit includes a differential amplifier circuit, a reference voltage source circuit, and a current source circuit, and the differential amplifier circuit includes a constant current source MOS transistor that flows a constant current, and a constant current source MOS transistor that flows a constant current. A pair of differential input MOS transistors connected in series with a constant current source MOS transistor, and each differential input MOS
a load MOS transistor connected in series with the transistor, gate electrodes of the pair of load MOS transistors are commonly connected to one of the connection points of the differential input MOS transistor and the load MOS transistor, and the reference voltage source A circuit is connected between the battery voltages and forms a reference voltage lower than the battery voltage and supplies it to one gate electrode of the differential input MOS transistor pair, and the differential amplifier circuit or the reference voltage source circuit receives a clock signal. The first step is to intermittently interrupt the current path of the circuit according to the
MOS transistor switch, the current source circuit is connected in series with the electronic circuit between the battery voltages and has a gate electrode connected to the differential input.
A current source MOS transistor connected to the other of the connection points between the MOS transistor and the load MOS transistor, and the reduced voltage applied to the connection point between the current source MOS transistor and the electronic circuit regardless of the intermittent operation of the differential amplifier circuit. a capacitive element connected between the battery voltage and the current source MOS transistor to output the voltage, and a capacitive element connected between the battery voltage and the gate electrode of the current source MOS transistor to supply the battery voltage to the electronic circuit. a second MOS transistor switch that receives the control signal to conduct the current source MOS transistor and thereby makes the current source MOS transistor conductive, and a connection point between the current source MOS transistor and the electronic circuit is connected to the differential input MOS transistor. An electronic device, characterized in that the electronic circuit, the pressure reducing circuit, and the capacitive element are formed on the same semiconductor substrate, the electronic circuit being feedback-connected to the other gate electrode of the pair.