Voltage detection circuit and timepiece

Abstract

This voltage detection circuit (6) is provided with: a comparator (3) having a first input terminal (3a) and a second input terminal (3b) to which a reference voltage (Vref) is input; a plurality of trimming resistors (ri) disposed between the detection object and the second input terminal; at least one coarse tuning resistor (Rj) disposed between the detection object and the second input terminal; an inching switch unit (9) that connects an arbitrary number of inching resistors to the detection target and the coarse tuning resistor in series; a coarse tuning switch unit (10) that connects an arbitrary number of coarse tuning resistors, the subject to be detected, and the fine tuning resistors in series; and a control unit (50) for controlling the on-off operation of the switch of the fine tuning switch unit and the on-off operation of the switch of the coarse tuning switch unit, the coarse tuning resistor including a resistor having a resistance value R equal to a total value obtained by adding the resistance values r of the plurality of fine tuning resistors.

Description

Technical Field

[0001] The present invention relates to a voltage detection circuit and a clock. Background Art

[0002] Conventionally, there are voltage detection circuits. Patent Document 1 discloses a voltage detection circuit comprising: a resistance voltage divider circuit including a coarse adjustment variable resistor circuit and a fine adjustment variable resistor circuit; a coarse adjustment unit for controlling the coarse adjustment variable resistor circuit; a fine adjustment unit for controlling the fine adjustment variable resistor circuit; and a control unit that controls the coarse adjustment unit and the fine adjustment unit based on a detection signal from a comparison circuit.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-016578.

[0004] It is desirable to improve the detection resolution in a voltage detection circuit without increasing the circuit scale. For example, it is desirable to improve the detection resolution while reducing the number of resistors. Summary of the Invention

[0005] An object of the present invention is to provide a voltage detection circuit and a timepiece that solve the above-mentioned problems.

[0006] The voltage detection circuit of the present invention is characterized in that it comprises: a comparator having a first input terminal and a second input terminal to which a reference voltage is input; a plurality of fine-tuning resistors arranged between the detection object and the above-mentioned second input terminal; at least one coarse-tuning resistor arranged between the above-mentioned detection object and the above-mentioned second input terminal; a fine-tuning switch unit connecting any number of the above-mentioned fine-tuning resistors in series with the above-mentioned detection object and the above-mentioned coarse-tuning resistors; a coarse-tuning switch unit connecting any number of the above-mentioned coarse-tuning resistors in series with the above-mentioned detection object and the above-mentioned fine-tuning resistors; and a control unit controlling the opening and closing action of the switch of the above-mentioned fine-tuning switch unit and the opening and closing action of the switch of the above-mentioned coarse-tuning switch unit, wherein the above-mentioned coarse-tuning resistor includes a resistor having a resistance value equal to the total value obtained by adding the resistance values ​​of the plurality of the above-mentioned fine-tuning resistors.

[0007] The voltage detection circuit of the present invention includes: a plurality of trimming resistors; a coarse adjustment resistor disposed between a detection target and a second input terminal of a comparator; a trimming switch unit that connects an arbitrary number of trimming resistors in series with the detection target and the coarse adjustment resistors; and a coarse adjustment switch unit that connects an arbitrary number of coarse adjustment resistors in series with the detection target and the trimming resistors. The coarse adjustment resistors include a resistor having a resistance value equal to the sum of the resistance values ​​of the plurality of trimming resistors. The voltage detection circuit of the present invention achieves improved detection resolution by combining the trimming resistors and the coarse adjustment resistors. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a diagram showing a timepiece according to the embodiment.

[0009] Figure 2 It is a diagram showing a voltage detection circuit according to an embodiment.

[0010] Figure 3 This is a flowchart showing the operation of the voltage detection circuit according to the embodiment.

[0011] Figure 4 It is a diagram of a detection sequence in an embodiment.

[0012] Figure 5 It is a diagram of a detection sequence in an embodiment.

[0013] Figure 6 is a graph of the detection characteristics of the comparator.

[0014] Figure 7 This is a diagram of a voltage detection circuit according to a first modified example of the embodiment.

[0015] Figure 8 It is a diagram of a voltage detection circuit according to a second modified example of the embodiment. DETAILED DESCRIPTION

[0016] Hereinafter, the voltage detection circuit of the embodiment of the present invention will be described in detail with reference to the accompanying drawings. In addition, the present invention is not limited by this embodiment. In addition, the constituent elements in the following embodiments include structures that can be easily assumed by those skilled in the art or substantially the same structures.

[0017] [Implementation Method]

[0018] Reference Figures 1 to 6 The embodiment is described. This embodiment relates to a voltage detection circuit. Figure 1 As shown, the timepiece 1 according to the embodiment includes an outer case 2, a battery 4, a windshield 5, a voltage detection circuit 6, a dial 31, a second hand 32, a minute hand 33, and an hour hand 34. The timepiece 1 of this embodiment is an electronic timepiece that calculates internal time based on a clock signal generated by an oscillation circuit.

[0019] The exterior case 2 includes a generally cylindrical housing body 21. The battery 4, voltage detection circuit 6, dial 31, second hand 32, minute hand 33, and hour hand 34 are housed in the housing body 21. A windshield 5 is a transparent member that closes the front opening of the exterior case 2. The rear opening of the exterior case 2 is closed by a back cover.

[0020] Battery 4 is a rechargeable secondary battery. Timepiece 1 uses the power supplied by battery 4 to keep the internal time and to move the second hand 32, minute hand 33, and hour hand 34. Timepiece 1 may also include a power generation unit such as a solar cell. In this case, the power generated by the power generation unit is stored in battery 4.

[0021] The voltage detection circuit 6 is a circuit for detecting the voltage of the battery 4 serving as the power source VSS. Figure 2 As shown, the voltage detection circuit 6 includes a comparator 3 , a first resistor group 7 for fine adjustment, a second resistor group 8 for coarse adjustment, a fine adjustment switch section 9 , a coarse adjustment switch section 10 , a variable resistor VR, and a control section 50 .

[0022] Comparator 3 is a comparator having a first input terminal 3a and a second input terminal 3b. A predetermined reference voltage Vref is input to first input terminal 3a. Reference voltage Vref can also be generated based on the output voltage of power supply VSS. Input voltage VM is input to second input terminal 3b. Input voltage VM is the voltage of power supply VSS divided by first resistor group 7, second resistor group 8, and variable resistor VR. The potential of power supply VSS relative to ground potential VDD is, for example, a negative value.

[0023] Comparator 3 outputs a signal corresponding to the comparison result between reference voltage Vref and input voltage VM. In this embodiment, comparator 3 outputs a detection signal when the potential of input voltage VM is lower than the potential of reference voltage Vref. The detection signal is, for example, a high-level ON signal. On the other hand, comparator 3 outputs a non-detection signal when the potential of input voltage VM is higher than the potential of reference voltage Vref. The non-detection signal is, for example, a low-level OFF signal.

[0024] The first resistor group 7, the second resistor group 8, and the variable resistor VR are arranged in series in this order, from the power supply VSS side to the ground potential VDD side. The variable resistor VR can be a switching resistor device having multiple resistors, or a potentiometer. The variable resistor VR changes the resistance value between the second input terminal 3b and the ground potential VDD. The variable resistor VR is controlled, for example, by the control unit 50.

[0025] The first resistor group 7 and the second resistor group 8 are arranged between the power supply VSS and the second input terminal 3b. The second resistor group 8 is used to roughly adjust the total resistance value between the power supply VSS and the second input terminal 3b. The first resistor group 7 is used to finely adjust the total resistance value between the power supply VSS and the second input terminal 3b.

[0026] The first resistor group 7 includes a plurality of trimming resistors ri (i=1, 2, ..., n). The plurality of trimming resistors ri have the same resistance value r [Ω]. The plurality of trimming resistors ri are connected in series. The trimming resistors r1, r2, ..., rn are arranged in this order from the second resistor group 8 toward the power supply VSS.

[0027] The fine-tuning switch section 9 connects an arbitrary number of fine-tuning resistors ri in series with the power supply VSS and the second resistor group 8. The fine-tuning switch section 9 includes a plurality of switches Sfi (i=1, 2, ..., n). The switch Sfi is, for example, an NMOS transistor. By closing, the switch Sf1 bypasses all the fine-tuning resistors ri. In other words, the switch Sf1 can short-circuit the two ends of the first resistor group 7. By closing, the switch Sf2 bypasses the fine-tuning resistor r2 to the fine-tuning resistor rn. In other words, the i-th switch Sfi bypasses the fine-tuning resistor ri to the fine-tuning resistor rn by closing. The switch Sfn bypasses the fine-tuning resistor rn by closing.

[0028] In the following description, the resistors in the plurality of trimming resistors ri that are not bypassed by the switches Sfi are referred to as “effective resistors.” The resistance value rs of the first resistor group 7 is the sum of the resistance values ​​of the effective trimming resistors ri.

[0029] The trimming switch section 9 can insert any number of trimming resistors (0 to n) as effective resistors between the power supply VSS and the second resistor group 8. When there is only one effective trimming resistor (ri), switch Sf1 is open, and switches Sf2 through Sfn are all closed. In other words, trimming resistor r1 is connected in series with the power supply VSS and the second resistor group 8. This results in a resistance value of r (Ω) for the first resistor group 7.

[0030] When p (2 < p < n) trimming resistors ri are enabled, switches Sf1 through Sfp are opened, and all other switches Sfi are closed. That is, trimming resistors r1, r2, ..., rp are connected in series with power supply VSS and second resistor group 8. Consequently, the resistance value rs of first resistor group 7 becomes p × r [Ω]. When all trimming resistors ri are enabled, all switches Sfi are opened. Consequently, the resistance value rs of first resistor group 7 becomes n × r [Ω].

[0031] The second resistor group 8 has at least one coarse adjustment resistor Rj (j=1, 2, ..., m). The coarse adjustment resistors Rj of this embodiment all have the same resistance value R [Ω]. In the case where the second resistor group 8 has multiple coarse adjustment resistors Rj, the multiple coarse adjustment resistors Rj are connected continuously and in series. The multiple coarse adjustment resistors R1, R2, ..., Rj are arranged in this order from the first resistor group 7 toward the ground potential VDD. The resistance value R [Ω] of one coarse adjustment resistor Rj is equal to the total value obtained by adding the resistance values ​​r [Ω] of multiple fine adjustment resistors ri. That is, the following formula (1) holds.

[0032] R=n×r……(1)

[0033] The coarse adjustment switch unit 10 connects an arbitrary number of coarse adjustment resistors Rj in series with the power supply VSS and the first resistor group 7. The coarse adjustment switch unit 10 includes a plurality of switches Scj (j=1, 2, ..., m). The switches Scj are, for example, NMOS transistors. By closing, the switch Sc1 bypasses all the coarse adjustment resistors Rj. In other words, the switch Sc1 can short-circuit both ends of the second resistor group 8. By closing, the switch Sc2 bypasses the coarse adjustment resistor R2 to the coarse adjustment resistor Rm. In other words, by closing the jth switch Scj, the coarse adjustment resistor Rj to the coarse adjustment resistor Rm is bypassed. By closing, the switch Scm bypasses the coarse adjustment resistor Rm.

[0034] In the following description, the resistors in the plurality of coarse adjustment resistors Rj that are not bypassed by the switches Scj are referred to as “effective resistors.” The resistance value Rs of the second resistor group 8 is the sum of the resistance values ​​of the effective coarse adjustment resistors Rj.

[0035] The coarse adjustment switch unit 10 can insert any number of coarse adjustment resistors Rj (from 0 to m) as effective resistors between the first resistor group 7 and the ground potential VDD. When only one coarse adjustment resistor Rj is effective, switch Sc1 is open, and switches Sc2 through Scm are all closed. In other words, coarse adjustment resistor R1 is connected in series with the power supply VSS and the first resistor group 7. Consequently, the resistance value Rs of the second resistor group 8 becomes R [Ω].

[0036] When q (2 < q < m) coarse adjustment resistors Rj are enabled, switches Sc1 through Scq are opened, and all other switches Scj are closed. In other words, coarse adjustment resistors R1, R2, ..., and Rq are connected in series with power supply VSS and first resistor group 7. Consequently, the resistance value Rs of second resistor group 8 becomes q × R [Ω]. When all coarse adjustment resistors Rj are enabled, all switches Scj are opened. Consequently, the resistance value Rs of second resistor group 8 becomes m × R [Ω].

[0037] The control unit 50 controls the operation of the voltage detection circuit 6. The control unit 50 is, for example, a control circuit configured to perform a predetermined operation. The control unit 50 controls the fine-tuning switch unit 9, the coarse-tuning switch unit 10, and the variable resistor VR. In more detail, the control unit 50 controls the opening and closing operation of each switch Sfi of the fine-tuning switch unit 9. The control unit 50 can control the opening and closing state of each switch Sfi independently of the opening and closing state of other switches Sfi. In addition, the control unit 50 controls the opening and closing operation of each switch Scj of the coarse-tuning switch unit 10. The control unit 50 can control the opening and closing state of each switch Scj independently of the opening and closing state of other switches Scj. In addition, the control unit 50 obtains the output signal of the comparator 3. The control unit 50 performs the voltage detection operation according to the instruction from the clock control unit, etc.

[0038] Figure 3 The flowchart of the voltage detection operation of the control unit 50 of this embodiment is shown. Figure 4 The picture shows Figure 3 The flowchart is an example of the voltage detection operation. Figure 4 In FIG, the left side is the coarse adjustment detection sequence, corresponding to steps S10 to S50 in the flowchart. Figure 4 The right side of is the detection sequence for fine adjustment, which corresponds to steps S60 to S90 in the flowchart. In the following description, the detection sequence for coarse adjustment is referred to as the "first timing" and the detection sequence for fine adjustment is referred to as the "second timing."

[0039] like Figure 4 As shown, in the first timing sequence, the total resistance value increases in units of R [Ω] until the signal from comparator 3 changes from detection to non-detection. The total resistance value is the sum of the resistance value rs of the first resistor group 7 and the resistance value Rs of the second resistor group 8. In other words, the total resistance value is the resistance value between the power supply VSS and the second input terminal 3b.

[0040] exist Figure 3 In step S10, the control unit 50 sets the resistance value Rs of the second resistor group 8 to 0 [Ω]. The control unit 50 closes all switches Scj of the coarse adjustment switch unit 10. If step S10 is executed, the process proceeds to step S20.

[0041] In step S20, the control unit 50 sets the resistance value rs of the first resistor group 7 to the maximum value, that is, n×r [Ω]. Step S20 corresponds to Figure 4 The initial resistance value increases during the first sequence of coarse adjustment (step 1). The control unit 50 opens all switches Sfi of the fine-tuning switch unit 9. Consequently, the serially connected fine-tuning resistors r1, r2, ..., rn serve as an effective resistor between the power supply VSS and the second input terminal 3b. Therefore, the total resistance value becomes R [Ω]. After executing step S20, the process proceeds to step S30.

[0042] In step S30, the control unit 50 determines whether a detection signal is obtained from the comparator 3. If the result of the determination in step S30 is affirmative, indicating that a detection signal is obtained, the process proceeds to step S40, and if negative, the process proceeds to step S60.

[0043] In step S40, the control unit 50 determines whether the resistance value Rs of the second resistor group 8 is the maximum value (m×R [Ω].) If the determination in step S40 is positive, the voltage detection ends; if the determination is negative, the process proceeds to step S50. If the determination in step S40 is positive, the sum of the resistance values ​​rs of the first resistor group 7 and Rs of the second resistor group 8 has reached the maximum value. Therefore, the control unit 50 determines that the voltage of the power supply VSS is greater than the detectable upper limit threshold value Vth and ends the voltage detection.

[0044] exist Figure 3 In step S50, control unit 50 increases resistance value Rs of second resistor group 8 by R [Ω]. Specifically, the number of effective coarse adjustment resistors Rj between first resistor group 7 and second input terminal 3b in second resistor group 8 increases by one. Control unit 50 opens switch Scj in coarse adjustment switch unit 10 corresponding to the effective coarse adjustment resistor Rj.

[0045] Step S50 corresponds to Figure 4 The resistance value increases after the second time in the first sequence (step 2 to step 5). If step S50 is executed, the process moves to step S30. Figure 4 During the coarse adjustment on the left side of the figure, while the total resistance value is below 4×R[Ω], the output of comparator 3 is a detection signal. When the total resistance value reaches 5×R[Ω], the output of comparator 3 changes to a non-detection signal. In other words, with the fifth increase in resistance value (step 5), the output of comparator 3 switches to a non-detection signal. Consequently, a negative determination is made in step S30, and the process proceeds to step S60, starting the second sequence of fine adjustment.

[0046] In step S60, the control unit 50 sets the resistance value rs of the first resistor group 7 to r [Ω]. The control unit 50 opens the switch Sf1 of the fine-tuning switch unit 9 and closes the other switches Sf2, ..., Sfn. Step S60 corresponds to Figure 4 The first resistance value change in the second sequence is shown on the right side of FIG. 1 (step 1). If step S60 is executed, the process proceeds to step S70.

[0047] In step S70, the control unit 50 determines whether a detection signal is obtained from the comparator 3. If the result of the determination in step S70 is affirmative, that is, the detection signal is obtained, the process proceeds to step S80, and if negative, the voltage detection ends.

[0048] If a negative determination is made in step S70, the control unit 50 determines that the voltage of the power supply VSS is lower than the threshold value Vth. In addition, the control unit 50 can calculate the voltage value of the power supply VSS based on the total resistance value. Figure 4In the second sequence, the output of the comparator 3 switches to a non-detection signal during the third resistance change (step 3). In this case, the voltage value of the power supply VSS is calculated based on the total resistance value of the previous step (step 2).

[0049] In step S80, the control unit 50 determines whether the resistance value rs of the first resistor group 7 is the maximum value n×r [Ω]. If the result of the determination in step S80 is affirmative, the voltage detection is terminated. If the result is negative, the process proceeds to step S90. If the resistance value rs of the first resistor group 7 is the maximum value and the determination in step S80 is affirmative, the process may be further executed. Figure 3 In this case, the process moves to step S10 and the voltage detection step is performed from the beginning.

[0050] In step S90, the control unit 50 increases the resistance value rs of the first resistor group 7 by r [Ω]. Specifically, the number of trimming resistors ri, which are interposed as effective resistors between the power supply VSS and the second resistor group 8 in the first resistor group 7, increases by one. The control unit 50 opens the switch Sfj corresponding to the effective trimming resistor ri in the trimming switch unit 9. After executing step S90, the process proceeds to step S70.

[0051] In addition, you can also Figure 3 In contrast to the flowchart of , voltage detection is performed while reducing the total resistance value. Figure 5 The first and second timings are shown when voltage detection is performed while reducing the total resistance value. In this case, the output of the comparator 3 switches from a non-detection signal to a detection signal, and each detection timing ends.

[0052] exist Figure 5 In the first sequence of coarse adjustment shown on the left side of FIG, the total resistance value is first set to the maximum (step 1). Then, the number of effective coarse adjustment resistors Rj in the second resistor group 8 is reduced one by one (step 2 to step 5). Figure 5 In the example shown in FIG5 , the output of comparator 3 is switched to the detection signal in step 5 , the first sequence ends and the process moves to the second sequence.

[0053] exist Figure 5 In the second sequence of fine-tuning on the right side, first, the number of effective coarse-tuning resistors Rj in the second resistor group 8 is increased by one (step 1). Then, the number of effective fine-tuning resistors ri is reduced one by one (step 2 to step 3). Figure 5 In the example, in step 3, the output of comparator 3 is switched to the detection signal, and the voltage detection ends.

[0054] In this way, when voltage detection is performed while reducing the total resistance value, the resistance value is reduced during both coarse and fine adjustments. In other words, the total resistance value increases and decreases in the same direction during coarse and fine adjustments. This prevents degradation of detection accuracy due to hysteresis. Figure 6 Indicates the detection characteristics of the comparator. Figure 6 As shown in FIG. 1 , there is hysteresis in the voltage value when switching from non-detection to detection and when switching from detection to non-detection. The voltage detection method of this embodiment can avoid the influence of this hysteresis.

[0055] As described above, the voltage detection circuit 6 of this embodiment includes a comparator 3, multiple trimming resistors ri, at least one coarse adjustment resistor Rj, a fine adjustment switch unit 9, and a coarse adjustment switch unit 10. The comparator 3 has a first input terminal 3a, to which a reference voltage Vref is input, and a second input terminal 3b. The multiple trimming resistors ri are arranged between the detection target and the second input terminal 3b. The coarse adjustment resistor Rj is arranged between the detection target and the second input terminal 3b.

[0056] The fine-tuning switch unit 9 connects an arbitrary number of fine-tuning resistors ri in series with the detection target and the coarse-tuning resistor Rj. The coarse-tuning switch unit 10 connects an arbitrary number of coarse-tuning resistors Rj in series with the detection target and the fine-tuning resistor ri. The coarse-tuning resistors Rj include resistors having a resistance value equal to the total value obtained by adding the resistance values ​​of the multiple fine-tuning resistors ri. In this embodiment, the resistance value R [Ω] of all coarse-tuning resistors Rj is equal to the above-mentioned total value n × r [Ω]. The voltage detection circuit 6 of this embodiment can improve versatility by improving the voltage detection resolution.

[0057] The voltage detection circuit 6 of this embodiment includes a variable resistor VR that changes the resistance value between the second input terminal 3b of the comparator 3 and the ground potential VDD. A voltage divided by the variable resistor VR, the fine adjustment resistor ri, and the coarse adjustment resistor Rj is input to the second input terminal 3b of the comparator 3. The variable resistor VR can change the voltage detection range and thus the resolution of the voltage detection.

[0058] The control unit 50 of this embodiment executes a first sequence, which serves as a coarse adjustment detection sequence, and a second sequence, which serves as a fine adjustment detection sequence. The first sequence is a sequence in which the number of coarse adjustment resistors Rj connected in series with the power supply VSS and the fine adjustment resistors ri to be detected is varied until the output of the comparator 3 switches. The second sequence is a sequence in which the number of fine adjustment resistors ri connected in series with the power supply VSS and the coarse adjustment resistors Rj to be detected is varied within a range of resistance values ​​before and after the output of the comparator 3 switches in the first sequence.

[0059] For example, in Figure 4In the first sequence shown on the left side of FIG, when the total resistance value increases from 4×R[Ω] to 5×R[Ω], the output of comparator 3 switches from detection to non-detection. In this case, in the second sequence on the right side, control unit 50 changes the number of effective trimming resistors ri within the resistance value range between 4×R[Ω] before the output change and 5×R[Ω] after the output change.

[0060] When the control unit 50 increases the number of coarse adjustment resistors Rj connected in series in the first sequence, it increases the number of fine adjustment resistors ri connected in series in the second sequence. On the other hand, when the control unit 50 decreases the number of coarse adjustment resistors Rj connected in series in the first sequence, it decreases the number of fine adjustment resistors ri connected in series in the second sequence. This avoids the influence of hysteresis in the comparator 3 and improves detection accuracy.

[0061] In the voltage detection circuit 6 of this embodiment, the first resistor group 7 is positioned closer to the power supply VSS (to be detected) than the second resistor group 8. Furthermore, the fine-tuning switch 9 is positioned closer to the power supply VSS (to be detected) than the coarse-tuning resistor Rj. This reduces the effect of the resistance of the switch Sfi on the voltage detection of the power supply VSS. Consequently, the voltage detection circuit 6 of this embodiment can improve voltage detection accuracy.

[0062] The voltage detection circuit 6 of this embodiment uses the trimming resistor ri to effectively perform rough detection in the first timing of coarse adjustment. By using the trimming resistor ri in both the fine adjustment and coarse adjustment detection timings, it is possible to improve the detection accuracy.

[0063] Furthermore, the voltage detection circuit 6 is not limited to detecting the voltage of the power supply VSS. The voltage detection circuit 6 can be used to detect various voltages within the timepiece 1. Furthermore, the application of the voltage detection circuit 6 is not limited to timepieces. The voltage detection circuit 6 can also be used in portable electronic devices and other devices.

[0064] [First Modification of the Embodiment]

[0065] Reference Figure 7 , a first variant example of the implementation method is described. Figure 7 1 is a diagram of a voltage detection circuit according to a first modification of the embodiment. The first modification of the embodiment differs from the above-described embodiment in that, for example, the resistance values ​​of the first resistor group 7 are weighted.

[0066] The first resistor group 7 of the first modified example includes four trimming resistors ri (i=1, 2, 3, 4) with different resistance values. The first resistor group 7 also includes a trimming resistor r5 that is always connected to the power supply VSS. Trimming resistor r5 is a resistor that is always active. The four trimming resistors r1, r2, r3, and r4 are arranged between the power supply VSS and the second resistor group 8 and are connected in series. Furthermore, trimming resistors r1, r2, r3, and r4 are arranged in this order from the power supply VSS side toward the second resistor group 8.

[0067] The four trimming resistors ri (i=1, 2, 3, 4) have a resistance value rf(i). The minimum value of the resistance value rf(i) of the four trimming resistors ri (i=1, 2, 3, 4) is r[Ω]. Figure 7 Among them, the trimming resistor r1 has the smallest resistance value r [Ω]. The resistance value rf(i) of the trimming resistor ri (i=1, 2, 3, 4) is determined as shown in the following formula (2).

[0068] rf(i)=2 i－1 ×r……(2)

[0069] That is, the resistance value rf(2) of the trimming resistor R2 is 2×r[Ω], the resistance value rf(3) of the trimming resistor R3 is 4×r[Ω], and the resistance value rf(4) of the trimming resistor R4 is 8×r[Ω]. In addition, the resistance value rf(5) of the trimming resistor R5 is r[Ω].

[0070] The trimming switch unit 9 connects any number of trimming resistors ri in series with the power supply VSS and the second resistor group 8. The trimming switch unit 9 of the first modified example includes multiple switches Sfi (i=1, 2, 3, 4). Closing a switch Sfi bypasses the corresponding trimming resistor ri. For example, switch Sf1 bypasses trimming resistor r1.

[0071] When all switches Sfi are closed, the fine-tuning switch section 9 connects one fine-tuning resistor r5 in series with the power supply VSS and the second resistor group 8 as an effective resistor. In this case, the resistance value rs of the first resistor group 7 is r[Ω]. The fine-tuning switch section 9 can connect any of 0 to 4 of the four fine-tuning resistors ri (i=1, 2, 3, 4) as effective resistors in series with the power supply VSS and the second resistor group 8. In other words, the fine-tuning switch section 9 can form a combined resistance of 0[Ω] to 15×r[Ω] by combining the four fine-tuning resistors ri (i=1, 2, 3, 4). Therefore, the fine-tuning switch section 9 can increase or decrease the resistance value rs of the first resistor group 7 from r[Ω] to 16×r[Ω] in units of r[Ω].

[0072] Second resistor group 8 in the first modified example, similar to second resistor group 8 in the aforementioned embodiment, includes at least one coarse adjustment resistor Rj (j = 1, 2, ..., m) having the same resistance value R [Ω]. Resistance value R [Ω] is equal to the sum of the resistance values ​​rf(i) of multiple fine adjustment resistors ri. In other words, the resistance value R of one coarse adjustment resistor Rj is 16 × r [Ω].

[0073] The coarse adjustment switch unit 10 connects any number of coarse adjustment resistors Rj in series with the power supply VSS and the first resistor group 7. The coarse adjustment switch unit 10 of the first modified example includes multiple switches Scj (j = 1, 2, ..., m). When a switch Scj is closed, the corresponding coarse adjustment resistor Rj is bypassed. For example, switch Sc1 bypasses coarse adjustment resistor R1. When all switches Scj are closed, all coarse adjustment resistors Rj are bypassed. In other words, the coarse adjustment switch unit 10 can connect any number of coarse adjustment resistors Rj, from 0 to m, in series with the power supply VSS and the first resistor group 7 as effective resistors.

[0074] The voltage detection circuit 6 of the first modified example can detect the voltage of the power supply VSS by substantially the same steps as the voltage detection circuit 6 of the above-described embodiment. Figure 3 The detection steps of the voltage detection circuit 6 of the first modified example are described with reference to the flowchart of FIG.

[0075] In step S10, the control unit 50 sets the resistance value Rs of the second resistor group 8 to 0 [Ω], and in step S20, sets the resistance value rs of the first resistor group 7 to its maximum value. In this case, the control unit 50 sets all trimming resistors ri of the first resistor group 7 to their effective resistances. Therefore, the resistance value rs of the first resistor group 7 reaches its maximum value, namely 16 × r [Ω].

[0076] Steps S30 to S50 are the same as those in the above embodiment. The control unit 50 increases the number of effective coarse adjustment resistors Rj in the second resistor group 8 until the output of the comparator 3 becomes a non-detection signal. If the non-detection signal is received from the comparator 3, the process shifts to the second sequence for fine adjustment.

[0077] In step S60, the control unit 50 closes all switches Sfi of the trimming switch unit 9 to set the resistance value rs of the first resistor group 7 to r [Ω]. If it is determined in step S70 that the output of the comparator 3 is a detection signal, the process proceeds to step S80.

[0078] In step S80, the control unit 50 determines whether the resistance value rs of the first resistor group 7 is 16×r [Ω], which is the maximum value. If a negative determination is made in step S80, the control unit 50 proceeds to step S90, whereupon the resistance value rs of the first resistor group 7 is increased by r [Ω]. If a positive determination is made in step S80, the voltage detection ends.

[0079] The voltage detection circuit 6 of the first modified embodiment can change the resistance value rs of the first resistor group 7 to 16 levels using five trimming resistors ri (i=1, 2, ..., 5), thereby improving the resolution and accuracy of voltage detection.

[0080] Furthermore, the number n of trimming resistors ri having different resistance values ​​is not limited to 4. The first resistor group 7 can include any n trimming resistors ri having different resistance values.

[0081] As described above, the voltage detection circuit 6 of the first modified example includes n trimming resistors ri having different resistance values. The above n is a natural number greater than 2. The minimum resistance value of the n trimming resistors ri is r [Ω]. The resistance value rf(i) of each of the n trimming resistors ri is 2 i－1 The voltage detection circuit 6 of the first modified example can improve the detection resolution while suppressing an increase in the number of switches Sfi to be fine-tuned.

[0082] In addition, in the second timing of fine-tuning, the number of fine-tuning resistors ri that are switched to be effective or not can also be determined according to the required resolution. Figure 7 The first resistor group 7 can achieve 16 levels of resistance value rs. In contrast, if the resolution is half that, with only eight levels, the switch Sf1 of the trimming resistor r1 can remain OFF (open). In this case, the resistance value rs can be switched to eight levels using switches Sf2, Sf3, and Sf4. This reduces the maximum number of steps required to confirm the detection result, shortening the detection time.

[0083] Furthermore, the fine-tuning resistor r5 may be omitted from the first resistor group 7. In this case, the resistance value of the coarse-tuning resistor Rj is R=15×r[Ω].

[0084] [Second Modification of the Embodiment]

[0085] Reference Figure 8 A second modified example of the embodiment will be described. Figure 8 This diagram shows a voltage detection circuit according to a second variation of the embodiment. The second variation differs from the first variation in that, for example, the resistance values ​​of the second resistor group 8 are weighted. Similar to the first resistor group 7 of the first variation, the first resistor group 7 of the second variation includes four trimming resistors ri (i = 1, 2, 3, 4) with different resistance values ​​and a trimming resistor r5 that is always active. Furthermore, the trimming switch section 9 of the second variation is configured similarly to the trimming switch section 9 of the first variation.

[0086] Second resistor group 8 of the second modified example includes m coarse adjustment resistors Rj (j = 1, 2, ..., m) with different resistance values. The m coarse adjustment resistors Rj are connected in series between first resistor group 7 and second input terminal 3b. Coarse adjustment resistors R1, R2, ..., Rm are arranged in this order from the power supply VSS side toward second input terminal 3b.

[0087] The m coarse adjustment resistors Rj (j=1, 2, ..., m) have a resistance value Rc(j). The minimum value of the resistance value Rc(j) of the m coarse adjustment resistors Rj is R[Ω]. Figure 8 Among them, the coarse adjustment resistor R1 has the smallest resistance value R [Ω]. The resistance value R of the coarse adjustment resistor R1 is 16×r [Ω]. The resistance value Rc(j) of each coarse adjustment resistor Rj is determined as shown in the following formula (3).

[0088] Rc(j)=2 j－1 ×R……(3)

[0089] That is, the resistance value Rc(2) of the coarse adjustment resistor R2 is 2×R[Ω], the resistance value Rc(3) of the coarse adjustment resistor R3 is 4×R[Ω], and the resistance value Rc(m) of the coarse adjustment resistor Rm is 2 m－1 ×R[Ω].

[0090] The coarse adjustment switch section 10 connects an arbitrary number of coarse adjustment resistors Rj in series with the power supply VSS and the first resistor group 7. The coarse adjustment switch section 10 of the second modified example has a plurality of switches Scj (j=1, 2, ..., m). The switch Scj bypasses the corresponding coarse adjustment resistor Rj by closing. The coarse adjustment switch section 10 can set any coarse adjustment resistor Rj of 0 to m among the m coarse adjustment resistors Rj as an effective resistor. In other words, the coarse adjustment switch section 10 can form 0 [Ω] to (2 m -1) × R[Ω]2 m In addition, the coarse adjustment switch section 10 can adjust the resistance value Rs of the second resistor group 8 from 0 [Ω] to (2 m -1)×R[Ω] increases or decreases in units of R[Ω].

[0091] The voltage detection circuit 6 of the second modified example can detect the voltage of the power supply VSS by substantially the same steps as the voltage detection circuit 6 of the above embodiment. Figure 3 The detection steps of the voltage detection circuit 6 of the second modified example are described with reference to the flowchart of FIG.

[0092] In step S10, the control unit 50 sets the resistance value Rs of the second resistor group 8 to 0 [Ω], and in step S20, sets the resistance value rs of the first resistor group 7 to its maximum value. In this case, the control unit 50 sets all trimming resistors ri of the first resistor group 7 to their effective resistances. Therefore, the resistance value rs of the first resistor group 7 reaches its maximum value, namely 16 × r [Ω].

[0093] In step S30, the control unit 50 determines whether a detection signal is obtained from the comparator 3. If a positive determination is made in step S30 and the process proceeds to step S40, the control unit 50 determines whether the resistance value Rs of the second resistor group 8 is the maximum value (2 m If a negative determination is made in step S40 and the process proceeds to step S50 , the control unit 50 increases the resistance value Rs of the second resistor group 8 by R [Ω].

[0094] That is, the control unit 50 increases the resistance value Rs of the second resistor group 8 by R [Ω] until the output of the comparator 3 becomes a non-detection signal. If the non-detection signal is received from the comparator 3, the second timing of fine adjustment is entered.

[0095] In step S60, the control unit 50 closes all switches Sfi of the trimming switch unit 9 to set the resistance value rs of the first resistor group 7 to r [Ω]. If an affirmative determination is made in step S70 that the output of the comparator 3 is a detection signal, the process proceeds to step S80.

[0096] In step S80, the control unit 50 determines whether the resistance value rs of the first resistor group 7 is 16×r [Ω], which is the maximum value. If a negative determination is made in step S80, the control unit 50 proceeds to step S90, whereupon the resistance value rs of the first resistor group 7 is increased by r [Ω]. If a positive determination is made in step S80, the voltage detection ends.

[0097] The voltage detection circuit 6 of the second modified embodiment can change the resistance value Rs of the second resistor group 8 to 2 by using m (2≤m) coarse adjustment resistors Rj. m In this way, the voltage detection range can be expanded. In addition, the voltage detection circuit 6 has n (2≤n) weighted trimming resistors ri, which can change the resistance value rs of the first resistor group 7 to 2 n Therefore, the voltage detection circuit 6 of the second modified example can expand the detection range while reducing the number of resistors and improve the resolution.

[0098] As described above, the voltage detection circuit 6 of the second modified example includes m coarse adjustment resistors Rj having different resistance values. The above m is a natural number greater than 2. The minimum resistance value of the m coarse adjustment resistors Rj is R[Ω]. The resistance value Rc(j) of each of the m coarse adjustment resistors Rj is 2 j－1 ×R. The voltage detection circuit 6 of the second modified example can expand the voltage detection region while suppressing an increase in the number of switches Scj for coarse adjustment.

[0099] Furthermore, the fine-tuning resistor r5 may be omitted from the first resistor group 7. In this case, the minimum resistance value of the coarse-tuning resistor Rj is R=15×r[Ω].

[0100] [Third Modification of the Embodiment]

[0101] A third modified embodiment of the embodiment will be described. In the above embodiment, voltage detection is terminated when the output of the comparator 3 switches during the second trimming sequence. Alternatively, voltage detection may be terminated when the output of the comparator 3 is predicted to switch.

[0102] Reference Figure 4 The voltage detection method of the third modified example is described. Figure 4 In the second trimming sequence shown on the right side of the diagram, when the resistance value rs of the first resistor group 7 increases to 3×r[Ω] (step 3), the output of comparator 3 becomes a non-detection signal, and voltage detection ends. Here, we examine the case where the detection voltage V13 does not reach the threshold value Vth when the resistance value rs is 3×r[Ω]. In this case, if the resistance value rs of the first resistor group 7 is set to the maximum value, 4×r[Ω], it is estimated that the output of comparator 3 switches to a non-detection signal.

[0103] In the third modified example, voltage detection is terminated when the output of comparator 3 remains a detection signal even if the resistance value rs increases to 3×r[Ω]. This determination is based on the results of the first sequence of coarse adjustment. In the first sequence, when the total resistance value reaches 5×R[Ω], the detection of comparator 3 switches to a non-detection signal. Therefore, if the total resistance value also reaches 5×R[Ω] in the second sequence of fine adjustment, it can be expected that the detection of comparator 3 will switch to a non-detection signal. In this way, voltage detection can also be terminated without switching the output of comparator 3 at a stage where the resistance value rs of the first resistor group 7 is one resistance value less than the maximum value. The detection voltage value of the power supply VSS in this case is the value adopted when the output of comparator 3 is switched, assuming that the resistance value rs of the first resistor group 7 is set to the maximum.

[0104] The contents disclosed in the above-mentioned embodiment and modified examples can be combined and executed as appropriate.

[0105] Description of Reference Numerals

[0106] 1…electronic watch; 2…external case; 3…comparator; 3a…first input terminal; 3b…second input terminal; 4…battery; 5…windshield; 6…voltage detection circuit; 7…first resistor group; 8…second resistor group; 9…fine-adjustment switch section; 10…coarse-adjustment switch section; 21…main body; 31…dial; 32…second hand; 33…minute hand; 34…hour hand; 50…control section; ri…fine-adjustment resistor; Rj…coarse-adjustment resistor; Sfi, Scj…switches; VDD…ground potential; VSS…power supply; Vref…reference voltage; VR…variable resistor.

Claims

1. A voltage detection circuit, characterized in that: have: A comparator having a first input terminal to which a reference voltage is input, and a second input terminal; a plurality of fine-tuning resistors, arranged between the detection object and the second input terminal; at least one coarse adjustment resistor, disposed between the detection object and the second input terminal; a fine-tuning switch unit, connecting any number of the fine-tuning resistors in series with the detection object and the coarse-tuning resistor; a coarse adjustment switch unit, connecting any number of the coarse adjustment resistors in series with the detection object and the fine adjustment resistor; as well as a control unit that controls the opening and closing actions of the switches included in the fine adjustment switch unit and the opening and closing actions of the switches included in the coarse adjustment switch unit, The coarse adjustment resistor includes a resistor having a resistance value equal to a total value obtained by adding resistance values ​​of the plurality of fine adjustment resistors.

2. The voltage detection circuit according to claim 1, wherein: having n trimming resistors having resistance values ​​different from each other, The n is a natural number greater than 2, The minimum resistance value of the n fine-tuning resistors is r, The resistance value rf(i) of each of the n trimming resistors is 2 i－1 ×r, where i = 1, 2, ..., n.

3. The voltage detection circuit according to claim 1, wherein: m coarse adjustment resistors having mutually different resistance values, The m is a natural number greater than 2, The minimum resistance value of the m coarse adjustment resistors is R, The resistance value Rc(j) of each of the m coarse adjustment resistors is 2 j－1 ×R, where j = 1, 2, ..., m.

4. The voltage detection circuit according to claim 1, wherein: a variable resistor for changing the resistance value between the second input terminal of the comparator and the ground potential; The second input terminal receives a voltage divided by the fine adjustment resistor, the coarse adjustment resistor, and the variable resistor.

5. The voltage detection circuit according to claim 1, wherein: The control unit executes a first sequence as a detection sequence for coarse adjustment and a second sequence as a detection sequence for fine adjustment. The first timing is a timing in which the number of the coarse adjustment resistors connected in series with the detection target and the fine adjustment resistor is changed until the output of the comparator is switched. The second timing is a timing in which the number of the fine adjustment resistors connected in series with the detection object and the coarse adjustment resistor is changed within a range of resistance values ​​before and after the output of the comparator is switched in the first timing. When the control unit increases the number of the coarse adjustment resistors connected in series at the first timing, the control unit increases the number of the fine adjustment resistors connected in series at the second timing. When the control unit reduces the number of the coarse adjustment resistors connected in series at the first timing, the control unit reduces the number of the fine adjustment resistors connected in series at the second timing.

6. The voltage detection circuit according to claim 1, wherein: The fine adjustment switch portion is arranged on the detection target side relative to the coarse adjustment resistor.

7. A timepiece comprising: The voltage detection circuit according to claim 1; and The battery as the detection object.

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