JP2017182183A - Clock with constant current circuit, temperature sensor and temperature compensation function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constant current circuit capable of outputting a constant current even when a power supply voltage varies, and a temperature sensor and a timepiece with temperature compensation function.SOLUTION: A constant current circuit 1 comprises: a first current mirror circuit 10; a plurality of second current mirror circuits 21 through 24; a constant current adjustment circuit 30; and a control signal output circuit 40 outputting a control signal having a constant voltage level for controlling the constant current adjustment circuit. The first current mirror circuit comprises a first transistor for the first circuit P1 and a second transistor for the first circuit P2. The plurality of second current mirror circuits comprises: constant current adjustment resistors R4 through R1; first transistors for the second circuits N11 through N14; and second transistors for the second circuits N21 through N24. Resistance values of the constant current adjustment resistors in the individual second current mirror circuits are different from one another. The control signal output circuit outputs the control signal for turning on a switch and activates one second current mirror circuit from the plurality of second current mirror circuits.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a constant current circuit, a temperature sensor, and a timepiece with a temperature compensation function.

A timepiece with a temperature compensation function that corrects the temperature characteristics of a crystal oscillation circuit that outputs a time reference signal is known as a highly accurate timepiece such as a yearly timepiece. The temperature sensor mounted on the timepiece with temperature compensation function includes a temperature sensor that is driven by a constant current bias by a self-bias type constant current circuit. However, due to variations in the elements constituting the constant current circuit and the temperature sensor, the constant current bias cannot often be obtained as designed.
Thus, a circuit is known in which a resistance value is changed by a control circuit to obtain a desired constant current bias (see Patent Document 1).

  In Patent Document 1, a resistor is selected by switching an analog switch using a comparator output signal or a control signal obtained by inverting an output signal of a comparator with an inverter.

JP 2000-183652 A

However, in Patent Document 1, when the output signal of the comparator and the control signal obtained by inverting the comparator are at the power supply voltage level, the power supply voltage fluctuates, so that the voltage level of the control signal also changes. Since the control signal is input to the gate of the analog switch, when the voltage level of the control signal changes, the ON resistance of the analog switch also changes. Then, the change in the ON resistance is added to the selected resistance, and the current also changes.
In the case of a temperature sensor driven with a constant current bias by the constant current circuit as described above, when the power supply voltage fluctuates and the constant current bias changes, the temperature detected by the temperature sensor also changes.
For this reason, temperature detection by the temperature sensor cannot be performed correctly, and a watch with a temperature compensation function equipped with this temperature sensor has a high accuracy because the temperature detected by the temperature sensor fluctuates due to fluctuations in the power supply voltage, and the correction amount shifts. There is a problem that it is impossible to keep.

  The object of the present invention is that there are a constant current circuit that can output a constant current even if the power supply voltage fluctuates, a temperature sensor that can accurately detect the temperature even if the power supply voltage fluctuates, a temperature change and a power supply voltage fluctuation. It is another object of the present invention to provide a timepiece having a temperature compensation function with high accuracy of instruction time.

  The constant current circuit according to the present invention includes a first current mirror circuit connected to a first power source that is one of a high potential side power source and a low potential side power source, and a plurality of first current mirror circuits connected to the first current mirror circuit. Two current mirror circuits, a second power source that is the other power source of the high potential side power source and the low potential side power source, and a plurality of transistors connected between the plurality of second current mirror circuits A constant current adjustment circuit including a switch; and a control signal output circuit that outputs a control signal at a constant voltage level for controlling the operation of the plurality of switches. The first current mirror circuit includes a first circuit for a first circuit. A plurality of second current mirror circuits including a constant current adjusting resistor and the first circuit first transistor, the constant current adjusting circuit including a transistor and a second transistor for the first circuit; A plurality of second current mirrors, each including a first transistor for a second circuit connected via an adjusting resistor and a second transistor for a second circuit connected to the second transistor for the first circuit The resistance values of the constant current adjusting resistors in the circuit are different from each other, and the control signal output circuit outputs the control signal for turning on the switch, and outputs a second signal from a plurality of second current mirror circuits. A current mirror circuit is operated.

According to the constant current circuit of the present invention, a plurality of second current mirror circuits are prepared, and the second current mirror circuit to be operated is selected by controlling the constant current adjustment circuit with a control signal at a constant voltage level. By changing the resistance value of the constant current adjusting resistor, a desired constant current can be obtained.
In addition, since the control signal of the constant current adjustment circuit is set to a constant voltage level, the signal applied to the switch of the constant current adjustment circuit is constant without being affected by fluctuations in the power supply voltage. It is possible to prevent the constant current value from changing without changing.
Therefore, according to the constant current circuit of the present invention, the constant current set by the selected second current mirror circuit is not subject to fluctuations in the power supply voltage.
In addition, since the constant current adjustment circuit is connected between the second current mirror circuit and the second power supply, the potential between the gate and the source of the transistor constituting the constant current adjustment circuit is higher than the threshold voltage Vth of the transistor. It becomes easy to configure the circuit so as to be large. Thereby, even when driving with a low power supply voltage, the ability to flow the current of the transistor can be increased, so that it is very effective when a constant current circuit is incorporated in a product such as a wristwatch that needs to be driven with a low voltage.
Further, since it is not necessary to increase the area of the switching circuit, the area of the IC can be reduced, and the IC can be efficiently arranged on the substrate on which the IC is mounted, and the IC cost can be reduced.

  In the constant current circuit of the present invention, the first power source is the high potential side power source, the second power source is the low potential side power source, the first circuit first transistor and the first circuit second power source. The transistor is a P-channel field effect transistor, and the second circuit first transistor and the second circuit second transistor are N-channel field effect transistors, and the constant current adjustment The switch of the circuit is composed of an N-channel field effect transistor, and there are N second current mirror circuits from the first to the Nth (N is an integer of 2 or more), and the constant current adjustment circuit The resistors include N resistors from the first resistor to the Nth resistor, and the constant current adjusting resistor of the k-th (k is an integer not less than 1 and not more than N) second current mirror circuit. Preferably, the k number of the resistor from the first resistor to the first k resistor is connected in series.

  According to the present invention, since a part of the resistors can be used in common in the plurality of second current mirror circuits, the arrangement space of the resistors can be reduced as compared with the case where separate resistors are provided in each second current mirror circuit. The area of the IC can be reduced. By reducing the area of the IC, it can be efficiently placed on the substrate on which the IC is mounted, and the IC cost can be reduced.

  In the constant current circuit of the present invention, the first power source is the low potential side power source, the second power source is the high potential side power source, the first circuit first transistor and the first circuit second power source. The transistor is an N-channel field effect transistor, and the second circuit first transistor and the second circuit second transistor are P-channel field effect transistors, and the constant current adjustment The switch of the circuit is composed of a P-channel type field effect transistor, and there are N second current mirror circuits from the first to the Nth (N is an integer of 2 or more), and the constant current adjustment circuit The resistors include N resistors from the first resistor to the Nth resistor, and the constant current adjusting resistor of the k-th (k is an integer not less than 1 and not more than N) second current mirror circuit. Preferably, the k number of the resistor from the first resistor to the first k resistor is connected in series.

  According to the present invention, since a part of the resistors can be used in common in the plurality of second current mirror circuits, the arrangement space of the resistors can be reduced as compared with the case where separate resistors are provided in each second current mirror circuit. The area of the IC can be reduced. By reducing the area of the IC, it can be efficiently placed on the substrate on which the IC is mounted, and the IC cost can be reduced.

  In the constant current circuit of the present invention, the plurality of switches of the constant current adjustment circuit include a first switch transistor disposed between the second transistor first transistor and the second power source, and the second circuit. And a second switch transistor disposed between the second power transistor and the second power source, wherein the first switch transistor and the second switch transistor are preferably configured to have the same size. .

  According to the present invention, the first switch transistor and the second switch transistor that form a pair of the constant current adjustment circuit are configured with the same size, so that the ON resistances of the transistors are the same, and the constant current circuit When designing the transistor, it is not necessary to consider the difference in the ON resistance of the transistor, and can be designed easily.

In the constant current circuit of the present invention, it is preferable that the constant current adjusting resistor is made of polysilicon.
According to the present invention, since the constant current adjusting resistor is made of polysilicon having a small voltage dependency, the influence of the fluctuation of the power supply voltage can be further reduced, and a constant current that is not affected by the fluctuation of the power supply voltage can be obtained. .

  The temperature sensor of the present invention includes the constant current circuit described above and a CR oscillation circuit driven by a constant current bias of the constant current circuit, and a sign of a slope of a temperature characteristic of a discharge resistor provided in the CR oscillation circuit. Is the same as the sign of the slope of the temperature characteristic of the constant current adjusting resistor provided in the constant current circuit, and the temperature is detected by the oscillation frequency of the oscillation signal output from the CR oscillation circuit. .

According to the present invention, since the CR oscillation circuit can be driven with a constant current bias of a constant current circuit, even if the power supply voltage fluctuates, the temperature sensor does not fluctuate, so the temperature sensor outputs accurate temperature information. it can. Therefore, it is very effective when the temperature sensor is driven by a primary battery in which the battery voltage is reduced by discharging or a secondary battery in which the voltage is increased or decreased by charging / discharging.
In addition, since the signs of the slopes of the temperature characteristics of the constant current adjusting resistor of the constant current circuit and the discharge resistance of the CR oscillation circuit are made the same, the resistance value of the temperature characteristic of each resistor decreases as the temperature increases. In the case of the characteristic that the resistance value increases as the temperature decreases, the constant current increases in the constant current circuit and the charge discharge speed increases in the CR oscillation circuit as the temperature increases, and the oscillation frequency increases. On the contrary, when the temperature is lowered, the constant current is reduced in the constant current circuit, and the discharge rate of charge is reduced in the CR oscillation circuit, so that the oscillation frequency is reduced.
On the other hand, when the temperature characteristic of each resistor is such that the resistance value increases as the temperature increases, and the resistance value decreases as the temperature decreases, the constant current decreases in the constant current circuit when the temperature increases. In the oscillation circuit, since the discharge rate of electric charges is slow, the oscillation frequency becomes small. On the other hand, when the temperature decreases, the constant current increases in the constant current circuit, and the charge discharge speed increases in the CR oscillation circuit, so that the oscillation frequency increases.
By using resistors with the same sign of the temperature characteristic slope, it is possible to superimpose the temperature characteristics in both the constant current circuit and the CR oscillation circuit, and the temperature gradient of the oscillation frequency that is the output of the temperature sensor is increased. Can provide a highly sensitive temperature sensor.

  A timepiece with a temperature compensation function of the present invention includes an oscillation circuit that oscillates a vibrator, a frequency adjustment circuit that adjusts the frequency of the oscillation circuit, a constant voltage circuit that drives the oscillation circuit, the temperature sensor, and the temperature sensor. Based on an arithmetic circuit that calculates a correction amount based on the temperature detected by a temperature sensor, a frequency adjustment control circuit that controls the frequency adjustment circuit based on the correction amount, and an oscillation signal output from the oscillation circuit And a time display unit for displaying the time.

According to the present invention, the time display unit can display the time based on an oscillation signal (for example, a signal of 1 Hz) that is an output of an oscillation circuit that oscillates the vibrator. However, since the vibrator has frequency temperature characteristics, when the temperature of the vibrator changes due to temperature or the like, the oscillation frequency of the oscillation signal output from the oscillation circuit also fluctuates, causing an error in the indicated time on the time display unit.
In the present invention, the frequency adjustment circuit, the temperature sensor, the calculation circuit, and the frequency adjustment control circuit are provided, the calculation circuit calculates a correction amount based on the temperature detected by the temperature sensor, and the frequency adjustment control circuit includes: The frequency adjustment circuit is controlled based on the calculated correction amount. For this reason, since the frequency adjustment circuit can adjust the frequency of the oscillation circuit based on the temperature of the vibrator, even if the temperature of the vibrator changes, the frequency variation of the oscillation signal output from the oscillation circuit can be suppressed. Therefore, the accuracy of the time displayed by the time display unit can be improved.
Furthermore, since the above-mentioned temperature sensor that can output accurate temperature information even if the power supply voltage fluctuates is used, the correction amount based on the temperature information detected by the temperature sensor can be accurately made regardless of the power supply voltage, and from the oscillation circuit Can output an oscillation signal with small frequency fluctuation until the end of discharge of the battery. For this reason, the time display accuracy of the time display unit driven based on this oscillation signal can be maintained high.

1 is a circuit diagram showing a constant current circuit according to a first embodiment of the present invention. It is a circuit diagram explaining operation | movement of the constant current circuit of 1st Embodiment. It is a graph which shows the relationship between the power supply voltage and constant current in a current mirror circuit. It is a circuit diagram which shows the constant current circuit which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the timepiece with a temperature compensation function of this invention. It is a circuit diagram which shows the circuit which concerns on the temperature sensor of this invention.

[First Embodiment]
A constant current circuit 1 according to a first embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a circuit diagram of a constant current circuit 1 according to the first embodiment.
The constant current circuit 1 includes a first current mirror circuit 10, a plurality (four in the present embodiment) of second current mirror circuits 20 (21 to 24), a constant current adjustment circuit 30, a control signal output circuit 40, Is provided.

The first current mirror circuit 10 includes first and second P-channel type (Pch) field-effect transistors (MOSFETs) P1 and P2. Here, the first transistor for the first circuit is constituted by the first field effect transistor P1, and the second transistor for the first circuit is constituted by the second field effect transistor P2.
The source of the first field effect transistor P1 is connected to the high potential side power supply VDD which is the first power supply, and the drain is connected to a constant current adjusting resistor R of second current mirror circuits 21 to 24 described later. The gate is connected to the gate of the second field effect transistor P2.
The second field effect transistor P2 has a diode coupling in which a drain and a gate are connected. The source of the second field effect transistor P2 is connected to the high potential side power supply VDD, the drain is connected to the second current mirror circuits 21 to 24, and the gate is connected to the gate of the first field effect transistor P1. It is connected.

The second current mirror circuit 20 includes four (N) second current mirror circuits 21 to 24 from the first (N = 1) to the fourth (Nth). Each of the second current mirror circuits 21 to 24 includes a constant current adjusting resistor R and first and second N-channel (Nch) field effect transistors N1 and N2.
Here, the constant current adjusting resistor R includes four (N) constant current adjusting resistors from the first resistor R1 to the fourth resistor (Nth resistor) R4. In the present embodiment, the first resistor R1 to the fourth resistor R4 are made of polysilicon.
The first transistor for the second circuit is configured by the first field effect transistor N1 (N11 to N14), and the second transistor for the second circuit is configured by the second field effect transistor N2 (N21 to N24). Is configured.

The first second current mirror circuit 21 includes a constant current adjustment resistor R, a first field effect transistor N11, and a second field effect transistor N21. Four resistors from the first resistor R1 to the fourth resistor R4 are connected in series.
The second second current mirror circuit 22 includes a constant current adjusting resistor R, a first field effect transistor N12, and a second field effect transistor N22. Three resistors from the first resistor R1 to the third resistor R3 are connected in series.
The third second current mirror circuit 23 includes a constant current adjustment resistor R, a first field effect transistor N13, and a second field effect transistor N23. Two resistors from the first resistor R1 to the second resistor R2 are connected in series.
The fourth second current mirror circuit 24 includes a constant current adjustment resistor R, a first field effect transistor N14, and a second field effect transistor N24. It is composed of one resistor R1.
Therefore, the constant current adjusting resistor R of the k-th (k is an integer not less than 1 and not more than N) second current mirror circuit is configured by connecting k resistors in series from the first resistor to the k-th resistor. ing.

In the second current mirror circuits 21 to 24, the drains of the first field effect transistors N11 to N14 are connected to the constant current adjustment resistor R, the source is connected to the constant current adjustment circuit 30, and the gate is 1 is connected to the drain of the field effect transistor P1.
In the second current mirror circuits 21 to 24, the drains of the second field effect transistors N21 to N24 are connected to the drain of the second field effect transistor P2, and the sources are connected to the constant current adjusting circuit 30. The gate is connected to the constant current adjusting resistor R, that is, the drains of the first field effect transistors N11 to N14.

The constant current adjustment circuit 30 includes a plurality of switches that intermittently connect between the current mirror circuits 21 to 24 and the low potential side power source VSS.
Specifically, the constant current adjustment circuit 30 includes N-channel field effect transistors N31 to N34, which are switches for intermittently connecting the first field effect transistors N11 to N14 and the low-potential-side power source VSS, Field-effect transistors N21 to N24 and N-channel field-effect transistors N41 to N44 which are switches for intermittently connecting the low-potential-side power supply VSS. Therefore, field effect transistors N31 to N34 constitute a first switch transistor, and field effect transistors N41 to N44 constitute a second switch transistor.

The drains of the field effect transistors N31 to N34 are connected to the sources of the field effect transistors N11 to N14, the sources are connected to the low potential power source VSS, and the gates are connected to the gates of the field effect transistors N41 to N44. Has been.
The drains of the field effect transistors N41 to N44 are connected to the sources of the field effect transistors N21 to N24, the sources are connected to the low potential power source VSS, and the gates are connected to the gates of the field effect transistors N31 to N34. Has been.
The field effect transistors N31 to N34 and the field effect transistors N41 to N44 are configured to have the same size.

The control signal output circuit 40 includes a level shifter (not shown), and outputs constant voltage level control signals SEL1 to SEL4 to the constant current adjustment circuit 30.
A constant voltage control signal SEL1 output from the control signal output circuit 40 is input to the gates of the field effect transistors N31 and N41. By this control signal SEL1, the field effect transistors N31 and N41 are simultaneously turned on and off.
A constant voltage control signal SEL2 output from the control signal output circuit 40 is input to the gates of the field effect transistors N32 and N42. By this control signal SEL2, the field effect transistors N32 and N42 are simultaneously turned on and off.
A constant voltage control signal SEL3 output from the control signal output circuit 40 is input to the gates of the field effect transistors N33 and N43. By this control signal SEL3, the field effect transistors N33 and N43 are simultaneously turned on and off.
A constant voltage control signal SEL4 output from the control signal output circuit 40 is input to the gates of the field effect transistors N34 and N44. By this control signal SEL4, the field effect transistors N34 and N44 are simultaneously turned on and off.

  Therefore, the control signal output circuit 40 uses any one of the control signals SEL1 to SEL4 as an on signal of the Nch field effect transistor and the rest as an off signal, so that the second current mirror circuits 21 to 24 can be controlled. One second current mirror circuit can be selected and operated.

Next, the operation of the constant current circuit 1 by the first current mirror circuit 10 and the second current mirror circuits 21 to 24 of the present embodiment will be described with reference to FIG. FIG. 2 is an equivalent circuit in the case where the control signal SEL1 is an ON signal and the other control signals SEL2 to SEL4 are OFF signals in FIG.
When the control signal SEL1 is an on signal and the field effect transistors N31 and N41 are turned on, the self-biased Nagata reference current having the first current mirror circuit 10 and the second current mirror circuit 21 shown in FIG. A constant current circuit 1 known as a circuit is constructed.
In the present embodiment, when β of the first field effect transistor P1 of the first current mirror circuit 10 is β _P1 and β of the second field effect transistor P2 is β _P2 , β _P1 = β _P2 . . Here, β is one of the parameters representing the characteristics of the MOS transistor. If the channel width is W, the channel length is L, the mobility is μ, and the capacitance per unit area of the gate oxide film is Cox, β = ( W / L) · μ · Cox.

Further, when β of the first field effect transistor N11 of the second current mirror circuit 21 is β _N11 and β of the second field effect transistor N21 is β _N21 , β _N11 <β _N21 . When the resistance value of the constant current adjusting resistor R is R, the constant current Id is expressed by the following equation (1).

  As apparent from the equation (1), the value of the constant current Id varies depending on the manufacturing variation of the resistor R. Therefore, in order to obtain a desired constant current, a resistance switching circuit is required. In this embodiment, as shown in FIG. 1, the plurality of second current mirror circuits 21 to 24 are switched by controlling the constant current adjustment circuit 30 with the control signals SEL1 to SEL4. Thereby, the resistance R for the constant current adjustment can be switched in four stages from the state where the four resistors R1 to R4 are connected in series to the state where only the resistor R1 is configured. Thus, a desired constant current can be obtained.

That is, if the control signal SEL1 is turned on by the control signal output circuit 40 and the others are turned off, the constant current circuit 1 is composed of the first current mirror circuit 10 and the second current mirror circuit 21, and is constant. The current adjustment resistor R includes four resistors R1 to R4 connected in series.
If the control signal SEL2 is turned on by the control signal output circuit 40 and the others are turned off, the constant current circuit 1 is composed of the first current mirror circuit 10 and the second current mirror circuit 22, and the constant current adjustment is performed. The resistance R is composed of three resistors R1 to R3 connected in series.
If the control signal SEL3 is turned on by the control signal output circuit 40 and the others are turned off, the constant current circuit 1 is composed of the first current mirror circuit 10 and the second current mirror circuit 23, and constant current adjustment. The resistance R is composed of two resistors R1 to R2 connected in series.
If the control signal SEL4 is turned on by the control signal output circuit 40 and the others are turned off, the constant current circuit 1 is composed of the first current mirror circuit 10 and the second current mirror circuit 24, and constant current adjustment. The resistance R is composed of one resistor R1 connected in series.

  In the constant current circuit 1, the control signals SEL1 to SEL4 are sequentially turned on to detect the constant current when the first current mirror circuit 10 and the second current mirror circuits 21 to 24 are combined. Then, the settings of the control signals SEL1 to SEL4 when a desired constant current is obtained can be written in the nonvolatile memory or formed by the control circuit inside the IC. Thereby, when the constant current circuit 1 is operated, the control signal output circuit 40 can output the set control signals SEL1 to SEL4 by reading the setting data of the nonvolatile memory, and the power supply voltage A desired constant current Id can be obtained from the constant current circuit 1 without being affected by fluctuations.

[Effect of the first embodiment]
According to such 1st Embodiment, there exist the following effects.
The constant current circuit 1 includes a first current mirror circuit 10 and a plurality of second current mirror circuits 21 to 24, and field effect transistors N31 to N34 and N41 which are switching elements of the constant current adjustment circuit 30. The resistance value of the constant current adjusting resistor R can be switched in four stages by controlling ON / OFF of .about.N44 with constant voltage level control signals SEL1.about.SEL4 output from the control signal output circuit 40. Therefore, even if there is a manufacturing variation in resistance, a desired constant current can be obtained by selecting a circuit that operates from the second current mirror circuits 21 to 24.

  Since the control signal output circuit 40 outputs the control signals SEL1 to SEL4 at the constant voltage level, the control signal applied to the gates of the field effect transistors N31 to N34 and N41 to N44 of the constant current adjustment circuit 30. Since SEL1 to SEL4 are at a constant level without being affected by fluctuations in the power supply voltage, there is no change in the ON resistance of each of the field effect transistors N31 to N34, N41 to N44, and the constant current value is changed by the fluctuation in the ON resistance It can be prevented from changing.

  In the plurality of second current mirror circuits 21 to 24, some of the resistors R1 to R3 can be used in common by the plurality of second current mirror circuits 21 to 24. Compared with the case of providing the resistor, the arrangement space of the resistor can be reduced, and the area of the IC can be reduced. By reducing the area of the IC, it can be efficiently placed on the substrate on which the IC is mounted, and the IC cost can be reduced.

  Since the constant current circuit 1 has the constant current adjustment circuit 30 connected between the second current mirror circuits 21 to 24 and the low potential side power supply VSS, the field effect transistor N31 that constitutes the constant current adjustment circuit 30. It is easy to configure the circuit so that the potentials between the gates and the sources of N34 and N41 to N44 are larger than the threshold voltage Vth of the field effect transistors N31 to N34 and N41 to N44. Thereby, even when driving with a low power supply voltage, the ability to flow the current of the transistor can be increased, so that it is very effective when the constant current circuit 1 is incorporated in a device such as a wristwatch that needs to be driven with a low voltage. . Further, since it is not necessary to increase the area of the switching circuit, the area of the IC can be reduced, and the IC can be efficiently arranged on the substrate on which the IC is mounted, and the IC cost can be reduced.

  Further, in the current mirror circuit, if the power supply voltage for driving the current mirror circuit is increased, the influence of channel length modulation increases, so that the constant current value increases as the power supply voltage increases. That is, as shown in FIG. 3, when the power supply voltage for driving the current mirror circuit is Vds and the constant current value Ids, if the power supply voltage is constant at the constant voltage Vd1, the channel length modulation is not affected. Since the constant current value Ids is also a constant value, a constant current that is more unaffected by fluctuations in power supply voltage can be obtained.

  Further, by connecting the substrate (SUB) of the field effect transistors N31 to N34 and N41 to N44 used in the constant current adjusting circuit 30 to the constant voltage power source, the threshold voltage Vth is affected by the back gate effect. Therefore, a constant current that is more unaffected by fluctuations in the power supply voltage can be obtained.

  Since the field effect transistors N31 to N34 and the field effect transistors N41 to N44 that are paired with the constant current adjustment circuit 30 are configured with the same size, the ON resistances of the transistors are the same, and the constant current circuit 1 When designing the transistor, it is not necessary to consider the difference in the ON resistance of the transistor, and can be designed easily.

Further, since the constant current adjusting resistors R1 to R4 are made of polysilicon having a small voltage dependency, it is possible to obtain a constant current that is not further affected by fluctuations in the power supply voltage. That is, generally, the resistor is constituted by polysilicon or diffusion. However, the resistance value of the resistor formed by diffusion varies depending on the power supply voltage. Since the resistance change of the polysilicon resistor due to the fluctuation of the power supply voltage is small, the constant current adjustment resistors R1 to R4 are made of polysilicon to obtain a constant current that is more unaffected by the fluctuation of the power supply voltage.
Further, even when the constant current circuit 1 is driven at a constant voltage, the resistance value fluctuates due to the influence of the power supply voltage unless the other part of the watch IC 110 is driven at a constant voltage. Therefore, also in this respect, the constant current adjusting resistors R1 to R4 are preferably made of polysilicon.

[Second Embodiment]
FIG. 4 is a circuit diagram showing a configuration of a constant current circuit 1A of the second embodiment. In the constant current circuit 1A, the same or similar components as those of the constant current circuit 1 of the first embodiment are denoted by the same reference numerals, and description thereof is simplified.
In the constant current circuit 1A, the first power source is the low potential side power source VSS and the second power source is the high potential side power source VDD. Therefore, the first current mirror circuit 10A is composed of Nch field effect transistors N1 and N2, and the plurality of second current mirror circuits 21A to 24A is composed of Pch field effect transistors P11 to P14 and P21 to P24. It is configured.
The first current mirror circuit 10A is connected to the low potential side power supply VSS, and the constant current adjustment circuit 30A is connected between the high potential side power supply VDD and the current mirror circuits 21A to 24A.
The constant current adjustment circuit 30A includes Pch field effect transistors P31 to P34 and P41 to P44, and is controlled by control signals SEL1 to SEL4 from the control signal output circuit 40.

[Effects of Second Embodiment]
Also in such a constant current circuit 1A, a constant current is generated between the first current mirror circuit 10A and the circuits selected from the second current mirror circuits 21A to 24A by the control signals SEL1 to SEL4 output from the control signal output circuit 40. The circuit 1A can be configured, and the constant current adjusting resistor R can be switched in four stages. Therefore, the same effect as the constant current circuit 1 of the first embodiment can be obtained.

[Third Embodiment]
Next, a third embodiment relating to a temperature sensor 2 using the constant current circuit 1 of the first embodiment and a timepiece 100 having a temperature compensation function using the temperature sensor 2 will be described with reference to FIGS. .

[Clock with temperature compensation function]
FIG. 5 is a block diagram showing the configuration of the timepiece 100 with a temperature compensation function.
The timepiece with temperature compensation function 100 includes a power supply 102, a timepiece IC 110 driven by the power supply 102, a crystal resonator 104, and a step motor 105.

The power source 102 is composed of a primary battery or a secondary battery. When a secondary battery is used, a generator for charging the secondary battery may be provided in the timepiece 100 with temperature compensation function, or may be configured to be charged from the outside of the timepiece 100 with temperature compensation function. As the generator, a clock generator such as a solar cell or a generator that generates electricity with a rotating weight can be used.
The step motor 105 drives hands such as a minute hand, a second hand and an hour hand through a train wheel (not shown). Therefore, the timepiece with temperature compensation function 100 is an analog type timepiece.

  The watch IC 110 includes a crystal oscillation circuit constant voltage circuit 111, an oscillation device 120, a frequency divider circuit 112, a motor pulse forming circuit 113, a temperature sensor control circuit 130, a temperature sensor constant voltage circuit 131, and a temperature. The sensor 2, the arithmetic circuit 141, and the frequency adjustment control circuit 142 are provided. A level shifter (L / S) (not shown) is arranged between the temperature sensor control circuit 130 and the temperature sensor 2, and a control signal input from the temperature sensor control circuit 130 to the temperature sensor 2 is a constant voltage signal.

The crystal oscillation circuit constant voltage circuit 111 converts the power supply voltage of the power supply 102 into a constant voltage and supplies the constant voltage to the oscillation device 120.
The oscillation device 120 includes an oscillation circuit 121, a frequency adjustment circuit 122, a level shifter (L / S) 123, and a waveform shaping circuit 125.
The oscillation circuit 121 is a general circuit for causing the crystal resonator 104 to oscillate. For example, a circuit including an oscillation inverter, a feedback resistor, a gate capacitor, and a drain capacitor can be used.
The oscillation circuit 121 drives the crystal resonator 104 as an oscillation source and outputs a 32 kHz (32768 Hz) oscillation signal as a source oscillation to the waveform shaping circuit 125. At this time, the frequency adjustment circuit 122 adjusts the frequency of the oscillation signal.
The waveform shaping circuit 125 is configured by a waveform shaping inverter or the like, and shapes the oscillation signal output from the oscillation circuit 121 and outputs it as a clock signal to the frequency dividing circuit 112.

The frequency dividing circuit 112 is a general frequency dividing circuit used in the watch IC 110 and includes a plurality of frequency dividers, and divides the oscillation signal to a certain period (for example, 1 Hz) to become a reference for time measurement. Output as a reference signal.
The motor pulse forming circuit 113 forms and outputs a motor pulse that drives the step motor 105 using the signal output from the frequency dividing circuit 112. The motor pulse is output from the motor pulse forming circuit 113 to the step motor 105, and the step motor 105 is driven. By driving the step motor 105, the pointer moves through the train wheel, and the time is displayed. Therefore, the time display unit 107 includes the motor pulse forming circuit 113, the step motor 105, the train wheel and the pointer (not shown).

  The clock signal output from the frequency dividing circuit 112 is also input to the temperature sensor control circuit 130. The temperature sensor control circuit 130 drives the temperature sensor 2 and the temperature sensor constant voltage circuit 131 at a predetermined timing by the input of the clock signal. At this time, the control signal output from the temperature sensor control circuit 130 to the temperature sensor 2 is a constant voltage control signal by a level shifter (not shown), and the temperature sensor 2 is driven by the constant voltage control signal.

[Temperature sensor]
The temperature sensor 2 includes the constant current circuit 1 and the CR oscillation circuit 60. Based on the oscillation frequency that varies depending on the temperature characteristics of the CR oscillation circuit 60, the temperature sensor 2 is a space (watch case). )).

Details of the temperature sensor 2 will be described with reference to FIG.
The temperature sensor 2 includes the constant current circuit 1 of the first embodiment, a CR oscillation circuit 60, and an output buffer 90. In the temperature sensor 2, at least one of the high potential side power source VDD and the low potential side power source VSS is set to a constant voltage by the temperature sensor constant voltage circuit 131, and the constant current circuit 1 is also driven by the constant voltage. In this embodiment, the high potential side power supply VDD output from the temperature sensor constant voltage circuit 131 is set to a voltage level lower than the power supply voltage of the power supply 102, and the high potential side power supply VDD is constant even if the power supply voltage fluctuates. The voltage level is maintained. Further, since the low potential side power supply VSS is a ground voltage, it is a constant voltage.

[Configuration of CR oscillation circuit]
The CR oscillation circuit 60 is a circuit composed of a capacitor (C) and a resistor (R), and outputs an oscillation signal having a preset frequency. As shown in FIG. 6, the CR oscillation circuit 60 of the present embodiment includes three stages of inverters 61, 62, and 63. Pch field effect transistors 611 and 611 that constitute the inverters 61 to 63 of the respective stages. The sources of 621 and 631 are connected to the high potential side power supply VDD via the Pch field effect transistor 80 of the current mirror circuit for supplying a constant current, and the sources of the Nch field effect transistors 612, 622 and 632 are connected. Is connected to the low-potential-side power supply VSS.
A resistor 641 and a capacitor 651 are connected in series to the drain of the inverter 61. A connection point between the resistor 641 and the capacitor 651 is connected to the gate of the inverter 62.
A resistor 642 and a capacitor 652 are connected in series to the drain of the inverter 62, and the connection point therebetween is connected to the gate of the inverter 63.
A resistor 643 and a capacitor 653 are connected in series to the drain of the inverter 63, and a connection point therebetween is connected to the gate of the output buffer 90 and further to the gate of the inverter 61.
The output buffer 90 is an inverter including a Pch field effect transistor 91 and an Nch field effect transistor 92.

  One end of each of the capacitors 651 to 653 is connected to the low potential side power source VSS. The output from the output buffer 90 is an output of the oscillation signal oscillated by the CR oscillation circuit 60 and is input to the arithmetic circuit 141 as the output of the temperature sensor 2.

The frequency of the oscillation signal of the CR oscillation circuit 60 is determined by the charge / discharge speed of the charges charged in the capacitors 651 to 653. Therefore, the drains of the inverters 61 to 63, the resistors (discharge resistors) 641 to 643 connected in series between the ground voltage VSS, the values of the capacitors 651 to 653, and the constant current supplied from the constant current circuit 1 Determines the oscillation frequency.
The resistors 641 to 643 of the CR oscillation circuit 60 are made of polysilicon which is the same type as the constant current adjusting resistors R1 to R4 of the constant current circuit 1.

  Since the resistors R1 to R4 constituting the constant current circuit 1, the resistors 641 to 643 and the capacitors 651 to 653 constituting the CR oscillation circuit 60 have temperature characteristics, they are supplied to the CR oscillation circuit 60. The constant current varies with temperature, and the frequency of the oscillation signal output from the CR oscillation circuit 60 varies with temperature. By utilizing this temperature characteristic, the temperature sensor 2 can be configured by combining the constant current circuit 1 and the CR oscillation circuit 60.

  The output of the constant current circuit 1 is connected to the gate of the field effect transistor 80, and the transistor P2 and the transistor 80 constitute a current mirror circuit. For this reason, the CR oscillation circuit 60 which is a temperature detection unit in the temperature sensor 2 is driven by the constant current bias of the constant current circuit 1. The constant current of the constant current circuit 1 is controlled by the control signals SEL1 to SEL4 from the control signal output circuit 40 as in the first embodiment so that the CR oscillation circuit 60 of the temperature sensor 2 can be driven by an appropriate constant current device. Is set.

As shown in FIG. 5, the output of the temperature sensor 2 (the oscillation frequency serving as temperature information) is input to the arithmetic circuit 141. The arithmetic circuit 141 calculates a correction amount of the frequency of the oscillation signal output from the oscillation device 120 based on the temperature measured by the temperature sensor 2 (the oscillation frequency of the CR oscillation circuit 60), and adjusts the frequency of the calculation result. Input to the control circuit 142.
The frequency adjustment control circuit 142 outputs a control signal for controlling the frequency adjustment circuit 122 based on the calculation result. At this time, the control signal output from the frequency adjustment control circuit 142 is converted to a constant voltage by the level shifter 123 and input to the frequency adjustment circuit 122.

The frequency adjustment circuit 122 adjusts the frequency of the oscillation signal output from the oscillation circuit 121 by the control signal. The frequency adjustment circuit 122 outputs, for example, an output from the oscillation circuit 121 by changing a connection time of an adjustment capacitor (capacitor) connected to the oscillation circuit 121 or changing the number of adjustment capacitors connected to the oscillation circuit 121. A conventionally used frequency adjustment circuit 122 such as one that adjusts the frequency of the oscillation signal to be generated can be used.
Therefore, the oscillation device 120 outputs an oscillation signal having a frequency adjusted by the frequency adjustment circuit 122.

[Effect of the third embodiment]
Since the temperature sensor 2 can drive the CR oscillation circuit 60 having temperature characteristics with the constant current bias of the constant current circuit 1, even if the power supply voltage of the power supply 102 fluctuates, the detection temperature of the temperature sensor 2 does not fluctuate. The temperature sensor 2 can output accurate temperature information.
For example, when the variation of the detected temperature due to the power supply voltage of the temperature sensor 2 was tested, when the power supply voltage was changed from 1.58 V to 1.20 V, a difference in detected temperature of about 10 ° C. occurred in the prior art. On the other hand, in the present embodiment, the detected temperature changes only at about −0.1 ° C., and it was confirmed that even if the power supply voltage fluctuates, the fluctuation of the detected temperature can be suppressed and accurate temperature information can be output.
Therefore, the correction amount calculated by the arithmetic circuit 141 is accurate without being affected by the power supply voltage, and the oscillation signal output from the oscillation device 120 is adjusted by adjusting the frequency adjustment circuit 122 by the frequency adjustment control circuit 142. Can be kept constant without being affected by fluctuations in the power supply voltage. For this reason, the timepiece with temperature compensation function 100 can maintain high accuracy until the end of discharge of the battery (power supply 102), and can also be applied to an annual difference timepiece.

  Since the temperature sensor 2 detects the temperature based on the oscillation frequency of the CR oscillation circuit 60, the arithmetic processing in the arithmetic circuit 141 inside the watch IC 110 is easy, and the correction processing by the frequency adjustment control circuit 142 and the frequency adjustment circuit 122 is performed. Can also be done easily.

In the temperature sensor 2, since the constant current adjusting resistors R1 to R4 of the constant current circuit 1 and the resistors 641 to 643 of the CR oscillation circuit 60 are formed of the same type (for example, polysilicon), the resistance change with respect to temperature. Can be set to the same inclination.
Therefore, if the temperature characteristics of the constant current adjusting resistors R1 to R4 and resistors 641 to 643 are such that the resistance value decreases as the temperature increases and the resistance value increases as the temperature decreases, Is increased, the constant current is increased in the constant current circuit 1 and the discharge rate of charge is increased in the CR oscillation circuit 60, so that the oscillation frequency is increased. On the other hand, when the temperature decreases, the constant current decreases in the constant current circuit 1 and the charge discharge speed decreases in the CR oscillation circuit 60, so the oscillation frequency decreases.
On the other hand, if the temperature characteristics of the constant current adjusting resistors R1 to R4 and resistors 641 to 643 are such that the resistance value increases as the temperature increases and the resistance value decreases as the temperature decreases, When it becomes higher, the constant current becomes smaller in the constant current circuit 1, and in the CR oscillation circuit 60, the charge discharge rate becomes slower, so the oscillation frequency becomes smaller. On the other hand, when the temperature decreases, the constant current increases in the constant current circuit 1, and the discharge rate of charges increases in the CR oscillation circuit 60, so that the oscillation frequency increases.
That is, by using resistors having the same sign of the temperature characteristic slope, it is possible to superimpose the temperature characteristic in both the constant current circuit 1 and the CR oscillation circuit 60, and the temperature of the oscillation frequency that is the output of the temperature sensor 2. The inclination can be increased. As a characteristic of the temperature sensor 2, the temperature sensor 2 can be made more sensitive as the inclination with respect to the temperature is larger.

[Modification]
In addition, this invention is not limited to the said embodiment, Other structures which can achieve the objective of this invention are included, and the modification etc. which are shown below are also contained in this invention.
For example, as the constant current circuit 1 in the temperature sensor 2, the constant current circuit 1A of the second embodiment may be used.

  The temperature sensor 2 of the present invention is not limited to the one used for the timepiece 100 with a temperature compensation function, and can be applied to a device that requires temperature measurement. In particular, since the temperature sensor 2 of the present invention includes the constant current circuit 1 and the CR oscillation circuit 60, it can be incorporated in the IC and can be applied to various devices.

  Furthermore, the constant current adjusting resistors R1 to R4 of the constant current circuit 1 and the resistors 641 to 643 of the CR oscillation circuit 60 are preferably the same type of resistors, but different types of resistors may be used. These resistors R1 to R4 and 641 to 643 are preferably made of polysilicon, but are not limited to polysilicon.

  In the constant current circuits 1 and 1A, the number of the second current mirror circuits 21 to 24 and 21A to 24A is not limited to four, and may be two or three, or five or more.

  DESCRIPTION OF SYMBOLS 1, 1A ... Constant current circuit, 2 ... Temperature sensor 10, 10A ... 1st current mirror circuit, 21-24, 21A-24A ... 2nd current mirror circuit, 30, 30A ... Constant current adjustment circuit, 40 ... Control signal Output circuit 60 ... CR oscillation circuit, 80 ... field effect transistor, 90 ... output buffer, 100 ... watch with temperature compensation function, 102 ... power supply, 104 ... crystal oscillator, 105 ... step motor, 107 ... time display unit, DESCRIPTION OF SYMBOLS 110 ... Clock IC, 111 ... Constant voltage circuit for crystal oscillation circuits, 112 ... Frequency dividing circuit, 113 ... Motor pulse formation circuit, 120 ... Oscillator, 121 ... Oscillation circuit, 122 ... Frequency adjustment circuit, 125 ... Waveform shaping circuit , 130 ... temperature sensor control circuit, 131 ... temperature sensor constant voltage circuit, 141 ... arithmetic circuit, 142 ... frequency adjustment control circuit, N DESCRIPTION OF SYMBOLS 1-N14 ... 1st field effect type transistor, N21-N24 ... 2nd field effect type transistor, N31-N34 ... Field effect type transistor, N41-N44 ... Field effect type transistor, P1 ... 1st field effect type Transistor, P2 ... second field effect transistor, R ... constant current adjusting resistor, R1 ... first resistor, R2 ... second resistor, R3 ... third resistor, R4 ... fourth resistor, SEL1-SEL4 ... control signal , VDD: high potential side power supply, VSS: low potential side power supply.

Claims (7)

A first current mirror circuit connected to a first power source which is one of a high potential side power source and a low potential side power source;
A plurality of second current mirror circuits connected to the first current mirror circuit;
Constant current adjustment comprising a plurality of switches composed of transistors connected between a second power source that is the other power source of the high potential side power source and the low potential side power source and a plurality of the second current mirror circuits Circuit,
A control signal output circuit for outputting a control signal at a constant voltage level for controlling the operation of a plurality of the switches,
The first current mirror circuit includes a first transistor for a first circuit and a second transistor for a first circuit,
The plurality of second current mirror circuits include:
A constant current adjusting resistor;
A first transistor for a second circuit connected to the first transistor for a first circuit via the constant current adjusting resistor;
A second circuit second transistor connected to the first circuit second transistor, respectively.
The resistance values of the constant current adjusting resistors in the plurality of second current mirror circuits are different from each other,
The control signal output circuit is
A constant current circuit, wherein the control signal for turning on the switch is output to operate one second current mirror circuit from the plurality of second current mirror circuits. The constant current circuit according to claim 1,
The first power source is the high potential side power source, the second power source is the low potential side power source,
The first transistor for the first circuit and the second transistor for the first circuit are composed of P-channel field effect transistors,
The first transistor for the second circuit and the second transistor for the second circuit are composed of N-channel field effect transistors,
The switch of the constant current adjustment circuit is composed of an N-channel field effect transistor,
N second current mirror circuits are provided from the first to the Nth (N is an integer of 2 or more),
The constant current adjusting resistor includes N resistors from a first resistor to an Nth resistor,
The constant current adjusting resistor of the k-th (k is an integer not less than 1 and not more than N) second current mirror circuit is characterized in that k resistors from the first resistor to the k-th resistor are connected in series. A constant current circuit. The constant current circuit according to claim 1,
The first power source is the low potential side power source, the second power source is the high potential side power source,
The first circuit first transistor and the first circuit second transistor are N-channel field effect transistors,
The first transistor for the second circuit and the second transistor for the second circuit are composed of P-channel field effect transistors,
The switch of the constant current adjustment circuit is composed of a P-channel field effect transistor,
N second current mirror circuits are provided from the first to the Nth (N is an integer of 2 or more),
The constant current adjusting resistor includes N resistors from a first resistor to an Nth resistor,
The constant current adjusting resistor of the k-th (k is an integer not less than 1 and not more than N) second current mirror circuit is characterized in that k resistors from the first resistor to the k-th resistor are connected in series. A constant current circuit. In the constant current circuit according to any one of claims 1 to 3,
The plurality of switches of the constant current adjustment circuit are:
A first switch transistor disposed between the second circuit first transistor and the second power source;
A second switch transistor disposed between the second circuit second transistor and the second power source;
The constant current circuit, wherein the first switch transistor and the second switch transistor have the same size. In the constant current circuit according to any one of claims 1 to 4,
The constant current adjusting resistor is made of polysilicon. A constant current circuit according to any one of claims 1 to 5,
A CR oscillation circuit driven by a constant current bias of the constant current circuit,
The sign of the slope of the temperature characteristic of the discharge resistor provided in the CR oscillation circuit is the same as the sign of the slope of the temperature characteristic of the constant current adjustment resistor provided in the constant current circuit,
A temperature sensor for detecting a temperature based on an oscillation frequency of an oscillation signal output from the CR oscillation circuit. An oscillation circuit for oscillating the vibrator;
A frequency adjustment circuit for adjusting the frequency of the oscillation circuit;
A constant voltage circuit for driving the oscillation circuit;
A temperature sensor according to claim 6;
An arithmetic circuit that calculates a correction amount based on the temperature detected by the temperature sensor;
A frequency adjustment control circuit for controlling the frequency adjustment circuit based on the correction amount;
And a time display unit for displaying time based on an oscillation signal output from the oscillation circuit.

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