JPH0142396B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to analog electronic timepieces, and more particularly to a method for determining the position of the rotor of a step motor, which is an electromechanical transducer thereof. In more detail,
The aim is to constantly drive the step motor with the optimum pulse width by determining the position of the rotor, thereby achieving low power consumption in analog electronic watches.

Conventionally, the display mechanism of a commonly used analog electronic timepiece is constructed as shown in FIG.
The output of a step motor composed of a stator 1, a coil 7, and a rotor 6 is transmitted to a fifth wheel 5, a fourth wheel 4, a third wheel 3, and a second wheel 2. is driving. On the other hand, the circuit configuration for driving this display mechanism, as shown in FIG. A drive pulse is applied that changes the direction of the current, and the bipolar magnetized rotor rotates 180 degrees every second, driving the wheel train.

However, with this conventional circuit configuration, only drive pulses of a certain width can be supplied to the motor, so even when a large load is applied, such as when driving a calendar mechanism, there is a sufficient safety factor to ensure that the step motor can rotate normally. The pulse width is set with Therefore, a large amount of current is consumed to drive the motor, and especially during normal low load conditions, the current is completely wasted. In addition, at low temperatures, the power supply voltage decreases due to an increase in battery internal resistance, so the motor drive pulse width must be set in advance to ensure that an output torque with sufficient margin is produced, taking into account the resulting decrease in motor output torque. It is necessary to keep it. This also results in wasted current consumption under normal temperatures. Furthermore, it is also necessary to take into consideration in advance the increase in frictional load due to aging. In any case,
In order to maintain a high degree of safety in normal rotation of the motor, current consumption is more than necessary, and this has been a major hindrance to reducing the power consumption of analog electronic watches incorporating step motors. As a means of solving this problem, it is usually driven with a shorter pulse width than before, and when it rotates, it supplies a pulse of the same width as before or an even narrower pulse, always depending on the load condition and the output torque condition of the motor. A method of driving a step motor with an optimal pulse width has been considered. The most important thing in realizing driving with such an optimal pulse width is "determining whether or not the rotor has rotated." Various methods have been proposed to date to detect rotor rotation, but they can be broadly classified into methods that detect the induced voltage caused by transient vibrations of the rotor, and methods that determine the position of the rotor at rest. It can be roughly divided into two types. The former is a method that is already in practical use, but since it detects the extremely unstable phenomenon of transient vibration of the rotor, various level settings, timing settings, etc. are very delicate, and it poses a burden in mass production. is large. On the other hand, in the latter case, there is no need to observe the movement of the rotor, and the rotation is determined at the most stable position where the rotor is stopped, so rotation can be easily determined without the same problem as in the former case. Against this background, methods have been introduced to measure whether the rotor rotates or not by determining the position of the rotor.

Conventionally, as a method for detecting the position of the rotor, a method has been proposed in which the difference in coil inductance caused by the difference in the position of the rotor is extracted as a difference in the rise of the detection current, and the position of the rotor is determined.

This method utilizes the fact that the direction of magnetic flux passing through the saturable parts 19-a and 19-b, which is unique to an integrated stator, differs depending on the stopping position of the rotor 16, as shown in FIGS. 3 and 4. It is. That is, the third
In the case of the figure, when the coil 15 is excited as shown in the figure, the magnetic fluxes 22-a and 22-b generated by the coil try to pass through the saturable parts 19-a and 19-b, but this method has already saturated or Since it is close to saturation, it is difficult for magnetic flux to pass through it, and the inductance of the coil shows a small value. On the other hand, in the case of FIG. 4, since the polarity of the rotor is reversed, the inductance of the coil shows a large value, contrary to the case of FIG. This difference in inductance is extracted as a difference in the rise of the detection current, and this conventional method is shown in FIG. In the figure, 23 is a step motor coil, 24 is a resistance element, 25, 26, 2
7, 28, 29, and 30 are switching elements.

In the figure, a shows a state in which the coil is turned off and the rotor remains at a stable position. In b, when the switching elements 25 and 30 are turned on from the state in a, current begins to flow through the coil 23 and the resistance element 24 connected in series with the coil in the circuit. At this time, the potential at the terminal x on one side of the resistive element 24 exhibits a waveform as shown in FIG. 6c. Note that a is the detection pulse, and TS in the figure is the detection pulse width. b is the detected current waveform, isp is the detected current waveform when the coil inductance is small, and isq is the detected current waveform when the coil inductance is large. In figure c, Vsp indicates the detected voltage (potential at point x) when the coil inductance is small,
Vsq indicates the detected voltage when the coil inductance is large. Since the threshold potential Vth of the detection element is set between the maximum values of Vsp and Vsq, there must be a sufficient potential difference between Vsp and Vsq. However, in this conventional example, when the coil is excited by the detection pulse, a detection resistor is inserted in series with the coil, so that only a small difference between the detection voltages Vsp and Vsq can be obtained. Therefore, it is necessary to strictly limit the variation in the value of the reference potential Vth of the detection element that determines Vsp and Vsq.

Therefore, the method of using the threshold potential of an inverter, which has large variations, as a detection element is unreasonable when considering the variations in mass production, and a comparator with a large number of elements and a large current consumption must be constructed inside the IC. . This unnecessarily complicates the IC configuration and is also undesirable from the standpoint of low power consumption. Also Vsp,
Since the difference in Vsq is small, a method has been proposed in which the detection pulse is sent in two directions, forward and reverse, and the difference between the two detection voltages obtained at this time is compared, but it is necessary to sample and hold one of the potentials. Since it requires analog signal processing, problems such as a complicated circuit configuration arise, and it has not been put to practical use. The biggest problem is that it requires an external detection resistor outside the IC. As can be easily understood from the detection principle of this method, the variation in detection resistance value is immediately caused by
This will lead to variations in the detection voltages Vsp and Vsq.
The accuracy of the detection resistance value must be kept to at least a few percent. As is well known, the variation in the diffused resistance value built inside an IC is at least 50
% to 100%, very large and accurate detection resistor
It is impossible to configure it inside the IC. this is
This means that an external resistor must be provided as a detection resistor outside the IC, which is extremely disadvantageous in today's electronic watches where thinness is paramount. Also, from a cost standpoint, it is not desirable to require an external resistor.

The present invention eliminates such conventional drawbacks, provides a rotor position detection method that does not require an external resistor, increases the difference between detection voltages Vsp and Vsq, and can easily determine the rotor position. The aim is to contribute to reducing the power consumption of electronic watches. The present invention will be explained in detail below based on the drawings.
Figure 7 is a diagram showing the rise of the current when the coil of a step motor is excited, and in the figure, isp is a diagram that shows the rise of the current when the coil of a step motor is excited. This shows the rise of the current when the coil is excited. In this case, the magnetic resistance is large, that is, the inductance of the coil is small, so the current shows a rapid rise.
isq indicates the rise of the current when the coil is excited so as to pass the magnetic flux in the direction opposite to the direction in which the saturable portion is already saturated, as shown in FIG. In this case, since the magnetic resistance is small, that is, the inductance of the coil is large, the current shows a gentle rise up to point r. After point r, the saturable portion saturates again in the opposite direction due to coil excitation, so the inductance suddenly decreases and the current rises rapidly. The specific values obtained from the experiment are: stator inner diameter 2.1 mm, stator thickness 0.5 mm.
mm, minimum width of saturable part δ = 0.1 mm, rotor inner diameter 1.5
mm, rotor thickness 0.5mm, number of coil turns = 10000 turns, coil DC resistance 2.7KΩ, power supply voltage 1.5V, T _R in Figure 7 is T _R = 0.93 msec, Ts =
At 0.25 msec, the currents at point p and point q were ip≈97, μA, and iq≈50 μA, respectively. In other words, if a current is passed through the coil with a pulse width of Ts = 0.25 msec as a detection pulse, the
The current value is either ip≒97μA or iq≒50μA, so if this is determined, the rotor position has been determined. In other words, it can be determined whether or not it has rotated. The present invention makes it possible to easily identify this difference in current as a difference in the waveform of the detected voltage without requiring an external resistor.

FIG. 8 shows an example of the configuration of a drive circuit according to the present invention, in which 40, 41, 42, 43 are switching elements, 40, 41 are P channel MOS transistors (hereinafter abbreviated as P-MOS), 42, 43
is an N-channel MOS transistor (hereinafter N-
(abbreviated as MOS), _VDD indicates the source potential of P-MOS, and Vss indicates the source potential of N-MOS. 44,
43 is a resistance element having a high resistance value (for example, 1MΩ). Further, O ₁ and O ₂ indicate both ends of the coil. FIG. 9 is a timing chart showing one embodiment of the present invention, and signals a, b, c, and d each indicate the gate signals of P-MOS and N-MOS in FIG. 8. It should be noted that the signals a, b, c, and d are referred to as detection signals, and as can be easily understood from the timing chart, they indicate the width of the detection pulse or the detection period. FIG. 10 shows the operation when the timing chart as shown in FIG. 9 is configured. In the figure, A corresponds to the section in Figure 9, and 4
This is a diagram in which P-MOS 0 and N-MOS 43 are turned on and a detection current 46 flows. When reaching the section from this state, 42 P-MOSs as shown in b.
By turning ON, the _O1 terminal, which is one end of the coil, is shorted to Vss. At this time, the current flowing through the coil tries to decrease rapidly, so a high potential is generated at the O ₂ terminal, which is the other end of the coil. As is well known, when a high potential occurs at the _O2 terminal, the P-MOS
Since a parasitic diode is formed between the substrate and the drain as shown at 49 and 50 in FIG. 9, the potential of the _O2 terminal is clipped.
Current flows in a loop such as 47. The current is 47
As the coil flows in a loop, the energy stored in the coil is released. Along with this
This means that the potential at the _O2 terminal is going to drop,
When this potential drops below the potential clipped by the parasitic diode 50, the current increases
As shown in C in the figure, the 4
Current flows in 8 loops. In this case, since the resistance element 45 has a very high resistance value (for example, 1 MΩ), the potential of the O ₂ terminal rapidly approaches the potential of Vss. FIG. 11 shows the state of the current and the state of the voltage at the O ₂ terminal at this time. In the figure, a is a detected pulse waveform, b is a current waveform, and c is a voltage waveform at the _O2 terminal. Corresponding to the detection currents isp and isq, the detection voltage waveforms Vsp and Vsq are obtained at the _O2 terminal, so
By determining Vsp and Vsq, the rotor position can be determined. The method for identifying Vsp and Vsq is c
As shown in FIG. 2, it is only necessary to determine whether the potential of the O ₂ terminal is higher or lower than the reference potential Vth of the detection element after a certain period of time has elapsed (Δt in the figure) from the end of the detection pulse. Showing the specific numbers obtained in the experiment,
When the detection pulse is set to 0.36 msec with a step motor of the level described above, when △t = 1.12 msec
Vsp=1.8V, Vsq=0.3V, which provides a sufficient potential difference for determination. According to the method according to the present invention, a potential difference that is approximately 3 to 4 times larger than that of the conventional method can be obtained, making it extremely easy to determine the position of the rotor. In other words, since the difference between Vsp and Vsq is large, variations in the reference potential of the detection element can be relatively tolerated, and current consumption can be reduced by using, for example, the threshold potential of an inverter instead of the converter that was conventionally used as the detection element. Moreover, it is also possible to substitute it with a method that places less burden on the circuit. Furthermore, the large difference between Vsp and Vsq means that the allowable range for variations depending on the motor becomes wider, which is extremely effective in mass production.
Furthermore, the most significant effect of the present invention is that there is no need for an external resistor outside the IC. According to experiments, the high resistance elements 44 and 45 in FIG. 8 have almost no effect on the waveform of the detected voltage at 500KΩ or more, so if they are set to about 1MΩ, for example, there is no need to manufacture them with high precision. Therefore, it can be configured inside the IC and no external resistor is required. Even if the circuit configuration shown in FIG. 12 is used, in which this high-resistance element is completely removed, the waveform of the detected voltage will hardly be affected, and the effects of the present invention will not change in any way. Regardless of the circuit configuration, there is no need to provide an external resistor element outside the IC, just by changing the logic configuration inside the IC.
It becomes possible to determine the position of the rotor. Therefore, it is extremely advantageous in analog electronic watches where thinness is the most important thing these days, and it is also a great advantage from a cost standpoint.

In the above explanation, a method has been described in which one end of the coil is short-circuited to the VSS potential at the end of the detection pulse, but a method of short-circuiting the coil to the _VDD potential may be used as described below. FIG. 13 shows high resistance elements 44 and 45 at both ends of the coil, O ₁ and O _{2 .}
This shows an example of a circuit configuration in which the voltage is dropped from V DD to the V _DD side.
FIG. 14 shows a timing chart for driving this. a', b', c', and d' in FIG. 14 indicate the gate signals of the P-MOS and N-MOS in FIG. 13. In other words, the section 40 is the section where P-MOS 43 and the N-MOS 43 are ON, and the section indicating the detection pulse width is the section where P-MOS 41 is turned ON at the same time as the coil terminal _O2 ends the detection pulse. It is shorted to V _DD potential. In this case, the voltage at the _O1 side, which is the other end of the coil, is determined. The following determination method is based on the same principle as the above-mentioned determination method, so a detailed description of the determination method will not be given here.

As explained above, according to the present invention, the IC
It is possible to obtain a large difference in detection voltage without requiring an external resistor. Therefore, regarding the detection element, there is no need to configure a comparator with a large number of elements and large current consumption, and it is possible to make a determination using the threshold potential of the inverter, which is less of a burden on the circuit; It is effectively reduced. Furthermore, conventionally, an external detection resistor has been required outside the IC, but according to the present invention, there is no need for an external resistor at all, which contributes to making the electronic timepiece thinner and lower in cost. Furthermore, if this rotor position determination method is used to determine rotor rotation/non-rotation in the pulse width control function, it is possible to eliminate the burdensome method of detecting the induced voltage in the rotor, such as by setting various levels and timing. , rotation/non-rotation can be determined and pulse width control can be easily realized.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the step motor and wheel train structure of an analog electronic watch. Figure 2 shows a conventional step motor drive circuit. FIGS. 3 and 4 are explanatory diagrams of step motor operation. FIG. 5 is a circuit diagram illustrating a conventional rotor position detection method. Figure 6 shows the detected current waveform and detected voltage waveform by the conventional detection method. FIG. 7 is a diagram showing the rise of the detection current. FIG. 8 shows an example of a circuit configuration for realizing the present invention. FIG. 9 is a timing chart showing one embodiment of the present invention. FIG. 10 is a circuit diagram explaining the operation of the present invention. FIG. 11 shows an example of the detected current and detected voltage according to the present invention. FIG. 12 shows another example of a circuit configuration for realizing the present invention. FIG. 13 shows yet another example of a circuit configuration for realizing the present invention. FIG. 14 is a timing chart showing another embodiment of the present invention. 1... Stator, 2... 2nd wheel, 3... 3rd wheel, 4... 4th wheel, 5... 5th wheel, 6... Rotor, 7... Coil, 10... Oscillation circuit, 11 ……
Frequency division circuit, 12...Pulse width synthesis circuit, 13...
Motor drive circuit, 14, 15... Coil, 16...
...Rotor, 17...Stator, 18-a, 18-
b...outer notch, 19-a, 19-b...saturable part, 20-a, 20-b...inner notch, 21-
a, 21-b, 22-a, 22-b...magnetic flux, 2
3... Coil, 24... Resistance element, 25, 26,
27, 28, 29, 30... switching element,
38...Coil, 40, 41...P-MOS, 4
2,43...N-MOS, 44,45...Resistance element, 46,47,48...Detection current loop, 4
9,50...parasitic diode.

Claims (1)

[Claims] 1. A frequency divider that divides the output signal of an oscillation circuit, a drive circuit that operates based on the output signal of the frequency divider, and a step motor that is driven by the drive circuit and includes a rotor, a stator, and a coil having a plurality of magnetic poles. In the rotor position determination method for an electronic timepiece, the drive circuit includes a first transistor and a second transistor that connect both ends of the coil to a first potential, and a third transistor that connects both ends of the coil to a second potential. and a fourth transistor, and a high resistance element that connects both ends of the coil to the first potential, and the drive circuit includes the first transistor and the fourth transistor, or the second transistor and the third transistor. A detection pulse with a small pulse width that cannot drive the rotor is passed through the coil with the transistor in an open state, and after the application of the detection pulse ends, only the transistor that was in the closed state when the detection pulse was applied is on the first potential side. A detection signal is applied so as to short-circuit one end of the coil to the first potential in an open state and conduct the energy stored in the coil to the second potential via a parasitic diode of a transistor on the second potential side. A method for determining a rotor position of an analog electronic watch, characterized in that the rotor position is determined based on the output voltage on the non-shorted side of the coil end after a certain period of time has elapsed from the end of application of the detection pulse. .