Electronic clock, motor drive circuit

Abstract

This prevents the circuit configuration from becoming overly complex and improves the responsiveness of the pointer's braking. [Solution] The electronic clock 1 includes a motor 70, a second hand 3c that is linked to the motor 70, a driving means that drives the motor 70 with a driving voltage to move the second hand 3c, an impact detection means that detects an impact based on the back electromotive force generated in the coil 72 of the motor 70, a braking means that, when an impact is detected by the impact detection means, drives the motor 70 with a braking voltage to brake the second hand 3c, a power supply 90 whose power supply voltage fluctuates, and a regulator 100 that steps down the power supply voltage to a constant voltage lower than the said power supply voltage, wherein the driving voltage is a constant voltage and the braking voltage is the power supply voltage.

Description

Technical Field

[0001] The present invention relates to an electronic clock and a motor drive circuit.

Background Art

[0002] For example, Patent Document 1 discloses a stepping motor control device that supplies a power supply voltage boosted by a boosting circuit to a supply unit when a determination unit determines that there is an impact in order to suppress needle jump of a pointer and performs braking of the pointer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1 above, since it takes time for the boosting circuit to start operating, there is a possibility that a delay occurs in braking the pointer. Further, in Patent Document 1 above, it is considered that normal needle movement is performed with a non-boosted power supply voltage. In this case, however, it is necessary to generate a plurality of needle movement pulses according to the power supply voltage, and the circuit configuration becomes complicated. In order to solve that problem, it is preferable to drive the motor with a constant voltage obtained by reducing the power supply voltage. However, when driving the motor with a constant voltage, there is a possibility that the braking force for braking the pointer becomes insufficient.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide an electronic clock and a motor drive circuit that can suppress complication of the circuit configuration and improve the responsiveness of pointer braking.

Means for Solving the Problems

[0006] The invention disclosed in this application, in order to solve the above-mentioned problems, has various aspects, and a summary of some of the most representative aspects is as follows.

[0007] (1) An electronic clock comprising: a motor; a pointer that is interlocked with the motor; a driving means for driving the motor with a driving voltage to move the pointer; an impact detection means for detecting an impact based on a back electromotive force generated in the coil of the motor; a braking means for braking the pointer by driving the motor with a braking voltage when an impact is detected by the impact detection means; a power supply whose power supply voltage fluctuates; and a step-down means for stepping down the power supply voltage to a constant voltage lower than the power supply voltage, wherein the driving voltage is the constant voltage and the braking voltage is the power supply voltage.

[0008] (2)(1) an electronic clock wherein the driving means includes a hand-movement pulse generating circuit that generates hand-movement pulses for moving the pointer, the braking means includes a lock pulse generating circuit that generates lock pulses for braking the pointer, the hand-movement pulses are output to the terminals of the motor coil based on the constant voltage, and the lock pulses are output to the terminals of the motor coil based on the power supply voltage when an impact is detected by the impact detection means.

[0009] (3)(2), the pointer performs normal movement when the pointer movement pulse is output, and the driving means includes a high-speed pointer movement pulse generation circuit that generates a high-speed pointer movement pulse that causes the pointer to move at a speed faster than the normal movement, and the high-speed pointer movement pulse is output to the terminals of the motor coil based on the power supply voltage, an electronic clock.

[0010] (4)(2) or (3), the pointer performs normal movement when the pointer movement pulse is output, and the driving means includes a reverse pulse generation circuit that generates a reverse pulse that moves the pointer in the opposite direction to the normal movement, and the reverse pulse is output to the terminals of the motor coil based on the power supply voltage, an electronic clock.

[0011] (5) An electronic clock having a voltage detection circuit for detecting the power supply voltage in any of (2) to (4), wherein the output period of the lock pulse is variable according to the power supply voltage detected by the voltage detection circuit.

[0012] (6)(5) The lock pulse generation circuit generates a lock pulse having a first output period when the power supply voltage detected by the voltage detection circuit is greater than or equal to a predetermined threshold, and generates a lock pulse having a second output period having a longer output period than the first output period when the power supply voltage detected by the voltage detection circuit is less than the threshold, an electronic clock.

[0013] (7) An electronic clock that, in any of (1) to (6), switches the drive voltage from the constant voltage to the power supply voltage if the power supply voltage is less than a predetermined voltage based on the constant voltage.

[0014] (8)(7) An electronic clock in which the predetermined voltage is the constant voltage.

[0015] (9) A motor drive circuit in which one end of a motor coil is connected to ground via a first switch, to a power supply whose power supply voltage fluctuates via a second switch, and to a step-down circuit that steps down the power supply voltage to a constant voltage lower than the said power supply voltage via a third switch, and the other end of the motor coil is connected to ground via a fourth switch, to the power supply via a fifth switch, and to the step-down circuit via a sixth switch. [Effects of the Invention]

[0016] According to the above aspects (1) to (9) of the present invention, it is possible to suppress the complexity of the circuit configuration and improve the responsiveness of the pointer's braking. [Brief explanation of the drawing]

[0017] [Figure 1] This is a plan view showing an example of an electronic clock according to this embodiment. [Figure 2]It is a block diagram showing an example of the configuration of an electronic clock according to this embodiment. [Figure 3] It is a circuit diagram showing an example of the configuration of the motor drive circuit of this embodiment. [Figure 4] It is a diagram showing an example of the driving pulse and the lock pulse in this embodiment. [Figure 5] It is a block diagram showing an example of the configuration of an electronic clock according to the first modification. [Figure 6] It is a diagram showing an example of each pulse in the first modification. [Figure 7] It is a block diagram showing an example of the configuration of an electronic clock according to the second modification. [Figure 8] It is a diagram showing an example of the lock pulse in the second modification.

MODE FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, embodiments of the present invention (hereinafter referred to as this embodiment) will be described in detail based on the drawings.

[0019] As shown in FIG. 1, the electronic clock 1 is an electronic clock with an analog display method, and includes a dial 2 and hour hand 3a, minute hand 3b, and second hand 3c which are hands for displaying time.

[0020] As shown in FIG. 2, the electronic clock 1 includes a frequency division circuit 10, a control circuit 20, a driving pulse generation circuit 30, a lock pulse generation circuit 40, a driver control circuit 50, a motor drive circuit 60, a motor 70 including a rotor 71 and a coil 72, a shock detection circuit 80, a power supply 90, and a regulator 100.

[0021] A predetermined clock signal output by an oscillation circuit including a crystal oscillator (not shown) is input to the frequency division circuit 10. The frequency division circuit 10 divides the input clock signal.

[0022] The control circuit 20 is a microcomputer with built-in memory, etc., which controls the operation of various circuits included in the electronic clock 1 according to a program stored in the memory. The control circuit 20 outputs the clock signal input from the frequency divider circuit 10 as a control signal. The control signal output by the control circuit 20 is input to the hand movement pulse generation circuit 30 and the lock pulse generation circuit 40.

[0023] The needle movement pulse generation circuit 30 generates needle movement pulses based on the control signal output from the control circuit 20 and outputs them to the driver control circuit 50. The needle movement pulses are pulses output to move the pointer normally. Based on the needle movement pulses, the second hand 3c moves in 1-second increments.

[0024] When an impact is detected by the impact detection circuit 80, the lock pulse generation circuit 40 generates a lock pulse, which is a braking pulse, based on the control signal output from the control circuit 20, and outputs it to the driver control circuit 50. For example, if an impact occurs to the electronic clock 1 during a period when no hand movement pulses are being output, the rotor 71 is in a state of free rotation and cannot maintain a stationary state, causing a misalignment of the second hand 3c. The lock pulse is output to suppress the misalignment of the second hand 3c caused by the impact. The stronger the lock pulse, the stronger the force holding the rotor 71, making it less likely for the second hand 3c to misalign.

[0025] The driver control circuit 50 is a circuit that controls the motor drive circuit 60 by selecting and outputting either a needle movement pulse or a lock pulse.

[0026] The motor drive circuit 60 supplies signals (drive waveforms) corresponding to the pulses output from the driver control circuit 50 to terminals O1 and O2 of the coil 72 of the motor 70, thereby driving the motor 70.

[0027] The motor 70 includes a rotor 71, a coil 72, and a stator (not shown). The motor 70 is preferably a stepper motor that intermittently drives in conjunction with at least the second hand 3c.

[0028] The rotor 71 is a two-pole magnetized disc-shaped rotating body, preferably magnetized radially with a north pole and a south pole. The stator is made of a soft magnetic material and is preferably arranged around the rotor 71. The coil 72 is preferably wound around a part of the stator. The rotor 71 rotates when each pulse is input to terminals O1 and O2 of the coil 72, causing the stator to be magnetized.

[0029] The shock detection circuit 80 is connected to the terminals of the coil 72. The shock detection circuit 80 detects shocks occurring in the electronic clock 1 based on the back electromotive force generated in the coil 72 as the second hand 3c (rotor 71) moves, and outputs a shock signal to the control circuit 20 when a shock signal is detected. When the control circuit 20 receives a shock signal, it is preferable to output a control signal to the lock pulse generation circuit 40 to generate a lock pulse. The driver control circuit 50 is then preferable to control the motor drive circuit 60 so that a lock pulse is output.

[0030] Power supply 90 is a power supply whose power supply voltage fluctuates. Power supply 90 may be, for example, a rechargeable secondary battery. Power supply 90 may be electrically connected to the terminals of coil 72 so as to be able to supply a power supply voltage, which is a damping voltage, to the terminals of coil 72.

[0031] The regulator 100 is controlled by the control circuit 20 and is preferably a step-down circuit that reduces the power supply voltage to a constant voltage lower than the power supply voltage. The regulator 100 is preferably electrically connected to the terminals of the coil 72 so that it can supply a constant voltage, which is the driving voltage, to the terminals of the coil 72.

[0032] Next, the circuit configuration of the motor drive circuit 60 will be described with reference to Figure 3. In Figure 3, the gate terminal of each transistor is indicated by "G", the drain terminal by "D", and the source terminal by "S". Each transistor functions as a switch that can be switched between ON and OFF by the driver control circuit 50.

[0033] The motor drive circuit 60 includes transistors P1 and P4, which are P-channel MOS transistors, and transistors N2, N3, N5, and N6, which are N-channel MOS transistors.

[0034] Transistor P1 has its source terminal connected to ground (GND) and its drain terminal connected to terminal O1. Transistor N2 has its source terminal connected to the power supply voltage (VBT) and its drain terminal connected to terminal O1. Transistor N3 has its source terminal connected to the constant voltage (VREG) and its drain terminal connected to terminal O1. Transistor P4 has its source terminal connected to ground (GND) and its drain terminal connected to terminal O2. Transistor N5 has its source terminal connected to the power supply voltage (VBT) and its drain terminal connected to terminal O2. Transistor N6 has its source terminal connected to the constant voltage (VREG) and its drain terminal connected to terminal O2.

[0035] In other words, terminal O1, which is one end of coil 72, is connected to ground GND via transistor P1, which is the first switch; connected to power supply 90 via transistor N2, which is the second switch; and connected to regulator 100 via transistor N3, which is the third switch.

[0036] Furthermore, terminal O2, which is the other end of coil 72, is connected to ground GND via transistor P4, which is the fourth switch, connected to power supply 90 via transistor N5, which is the fifth switch, and connected to regulator 100 via transistor N6, which is the sixth switch.

[0037] By adopting the configuration shown in Figure 3, the motor 70 is driven based on the power supply voltage VBT when transistors P1 and N5 are turned ON, or when transistors P4 and N2 are turned ON. As a result, a lock pulse based on the power supply voltage VBT is output, as shown in Figure 4.

[0038] Furthermore, by adopting the configuration shown in Figure 3 for the motor drive circuit 60, the motor 70 is driven based on a constant voltage when transistors P1 and N6 are turned ON, or when transistors P1 and N3 are turned ON. Specifically, the stator is reverse-magnetized and the rotor 71 rotates as transistors P1 and N6 are alternately turned ON and transistors P1 and N3 are alternately turned ON. As a result, a needle movement pulse is output by the constant voltage VREG, as shown in Figure 4. As shown in Figure 4, the needle movement pulse preferably consists of multiple single pulses that are output intermittently at a predetermined duty cycle. The duty cycle refers to the proportion of time during which a single pulse is output within a predetermined period.

[0039] Furthermore, the control circuit 20 should activate the regulator 100 during normal hand movement, and stop the regulator 100 when an impact is detected by the impact detection circuit 80.

[0040] In this embodiment described above, by outputting the needle movement pulse based on a constant voltage VREG, it becomes unnecessary to generate multiple types of needle movement pulses corresponding to the power supply voltage VBT, thus simplifying the configuration of the needle movement pulse generation circuit 30. Furthermore, by outputting the lock pulse based on the power supply voltage VBT, insufficient strength of the lock pulse can be suppressed. In addition, when an impact is detected, it is possible to switch from the constant voltage VREG to the power supply voltage VBT without activating other circuits such as a boost circuit. Therefore, there is no delay during braking, and the responsiveness is good.

[0041] Next, a first modified example of this embodiment will be described with reference to Figures 5 and 6. Note that components having the same function as those described with reference to Figure 3 will be given the same reference numerals, and their detailed descriptions will be omitted.

[0042] The first modified electronic clock 101 includes, in addition to the configuration described with reference to Figure 3, a reverse pulse generation circuit 120 and a high-speed hand movement pulse generation circuit 130.

[0043] The reverse pulse generation circuit 120 generates a reverse pulse that causes the second hand 3c to move in the opposite direction to the normal movement of the hands, and outputs it to the driver control circuit 50.

[0044] The high-speed needle movement pulse generation circuit 130 generates high-speed needle movement pulses that move the second hand 3c at a faster speed than normal needle movement and outputs them to the driver control circuit 50. As shown in Figure 6, the high-speed needle movement pulses H1 and H2 are composed of multiple consecutive single pulse groups and are preferably pulses with a higher duty cycle than the needle movement pulses. Alternatively, the high-speed pulses are preferably pulses that are output more times per unit time than the needle movement pulses. For example, during normal needle movement, the needle movement pulse is output once per second, while during high-speed needle movement, the high-speed needle movement pulse is output dozens of times or more per second.

[0045] The driver control circuit 50 may output a high-speed hand movement pulse H1 based on the power supply voltage VBT. This makes it possible to move the second hand 3c quickly with a strong driving force. However, it is not limited to this, and the driver control circuit 50 may also output a high-speed hand movement pulse H2 based on a constant voltage VREG, as in normal hand movement.

[0046] Although not shown in the diagram, the driver control circuit 50 may output a reverse pulse based on the power supply voltage VBT. This makes it possible to quickly reverse the second hand 3c with a strong driving force. However, it is not limited to this, and the driver control circuit 50 may also output a reverse pulse based on a constant voltage VREG, similar to normal hand movement.

[0047] Next, a second modified example of this embodiment will be described with reference to Figures 7 and 8. Note that components having the same function as those described with reference to Figures 3 and 5 will be given the same reference numerals, and their detailed descriptions will be omitted.

[0048] The electronic clock 201 according to the second modified example includes a voltage detection circuit 140 in addition to the configuration described with reference to Figure 5. The voltage detection circuit 140 detects the current power supply voltage VBT in the power supply 90. The current power supply voltage VBT detected by the voltage detection circuit 140 is input to the control circuit 20. The control circuit 20 outputs a control signal to the lock pulse generation circuit 40 to generate a lock pulse of an intensity corresponding to the current power supply voltage VBT.

[0049] The power supply voltage VBT may increase or decrease due to various factors. For example, the power supply voltage VBT will decrease in low-temperature environments. When the power supply voltage VBT is low, the strength of the lock pulse may become insufficient.

[0050] Therefore, in the second modification, as shown in Figure 8, the output period of the lock pulse is made longer as the power supply voltage VBT decreases. For example, the lock pulse generation circuit 40 generates a lock pulse with an output period of the first output period when the power supply voltage VBT is above a predetermined threshold, and generates a lock pulse with an output period of the second output period which is longer than the first output period when the power supply voltage VBT is below a predetermined threshold. This suppresses insufficient lock pulse strength when the power supply voltage VBT is low, and also suppresses unnecessary increases in power consumption during braking when the power supply voltage VBT is sufficiently high.

[0051] Furthermore, the output duration of the high-speed needle movement pulse and reverse pulse mentioned above may be variable depending on the magnitude of the power supply voltage VBT. For example, when the power supply voltage VBT is low, it is advisable to lengthen the output duration of the high-speed needle movement pulse and reverse pulse. Also, when the power supply voltage VBT is low, the duty cycle of the high-speed needle movement pulse and reverse pulse may be increased.

[0052] In this embodiment and its modifications, an example has been described in which at least a portion of the hand movement pulse generation circuit 30, driver control circuit 50, motor drive circuit 60, reverse pulse generation circuit 120, and high-speed hand movement pulse generation circuit 130 functions as a drive means, the shock detection circuit 80 functions as a shock detection means, at least a portion of the lock pulse generation circuit 40, driver control circuit 50, and motor drive circuit 60 functions as a braking means, and the regulator 100 functions as a step-down means, but the invention is not limited to this. That is, the block diagrams shown in Figures 2, 5, and 7 are just examples, and the electronic clock may further include other circuits as long as they can realize the functions described in this embodiment and its modifications.

[0053] Furthermore, while this embodiment and its modifications describe an example in which the hand movement pulse is output based on a constant voltage, the embodiment is not limited to this. For example, if the current power supply voltage VBT detected by the voltage detection circuit 140 falls below a predetermined voltage, the drive voltage may be switched from the constant voltage to the power supply voltage. In other words, the hand movement pulse may be output based on the power supply voltage. This can prevent insufficient driving force during normal hand movement. In this case, the electronic clock 1 shown in Figure 3 may have a voltage detection circuit 140.

[0054] The power supply voltage VBT may be used not only during braking, high-speed hand movement, and reverse hand movement as described above, but also during other high-load operations. For example, the date wheel may be advanced based on the power supply voltage VBT.

[0055] Furthermore, although this embodiment and its modified examples describe an example in which the second hand 3c is linked to the motor 70, the invention is not limited to this, and the hour hand 3a and minute hand 3b may also be linked to the motor 70 and driven by a drive voltage and a braking voltage. [Explanation of Symbols]

[0056] 1 Electronic clock, 2 Dial face, 3a Hour hand, 3b Minute hand, 3c Second hand, 10 Frequency divider circuit, 20 Control circuit, 30 Hand movement pulse generation circuit, 40 Lock pulse generation circuit, 50 Driver control circuit, 60 Motor drive circuit, 70 Motor, 71 Rotor, 72 Coil, 80 Shock detection circuit, 90 Power supply, 100 Regulator, 120 Reverse pulse generation circuit, 130 High-speed hand movement pulse generation circuit, 140 Voltage detection circuit.

Claims

1. Motor and, A pointer that is linked to the motor, A driving means that drives the motor with a driving voltage to move the pointer, An impact detection means for detecting an impact based on the back electromotive force generated in the coil of the motor, When an impact is detected by the impact detection means, a braking means drives the motor with a braking voltage to brake the pointer, A power supply with fluctuating power supply voltage, A step-down means for reducing the power supply voltage to a constant voltage lower than the power supply voltage, It has, The aforementioned drive voltage is the constant voltage, The braking voltage is the power supply voltage. Electronic clock.

2. The driving means includes a needle movement pulse generation circuit that generates needle movement pulses for moving the pointer, The braking means includes a lock pulse generation circuit that generates a lock pulse to brake the pointer, The needle movement pulse is output to the terminals of the motor coil based on the constant voltage. The lock pulse is output to the terminals of the motor coil based on the power supply voltage when an impact is detected by the impact detection means. The electronic clock according to claim 1.

3. The aforementioned guide performs normal needle movement when the needle movement pulse is output. The driving means includes a high-speed needle pulse generation circuit that generates high-speed needle pulses that cause the needle to move at a speed faster than the normal needle movement, The high-speed needle movement pulse is output to the terminals of the motor coil based on the power supply voltage. The electronic clock according to claim 2.

4. The aforementioned guide performs normal needle movement when the needle movement pulse is output. The driving means includes a reverse pulse generation circuit that generates a reverse pulse that causes the pointer to move in the opposite direction to the normal movement of the pointer, The reverse pulse is output to the terminals of the motor coil based on the power supply voltage. The electronic clock according to claim 2.

5. The circuit has a voltage detection circuit that detects the power supply voltage, The output period of the lock pulse is variable according to the power supply voltage detected by the voltage detection circuit. The electronic clock according to claim 2.

6. The lock pulse generation circuit generates a lock pulse with an output period of a first output period when the power supply voltage detected by the voltage detection circuit is greater than or equal to a predetermined threshold, and generates a lock pulse with an output period of a second output period that is longer than the first output period when the power supply voltage detected by the voltage detection circuit is less than the threshold. The electronic clock according to claim 5.

7. If the power supply voltage is less than a predetermined voltage based on the constant voltage, the drive voltage is switched from the constant voltage to the power supply voltage. The electronic clock according to any one of claims 1 to 6.

8. The predetermined voltage is the constant voltage. The electronic clock according to claim 7.

9. One end of the motor coil is connected to ground via a first switch, to a power supply whose power supply voltage fluctuates via a second switch, and to a step-down circuit that reduces the power supply voltage to a constant voltage lower than the said power supply voltage via a third switch. The other end of the motor coil is connected to the ground via a fourth switch, to the power supply via a fifth switch, and to the step-down circuit via a sixth switch. Motor drive circuit.

Images