JP2726843B2 - Electromagnetic drive circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic drive circuit used for driving a pendulum or the like. 2. Description of the Related Art FIG. 4 shows a drive circuit for detecting and driving a pendulum of a timepiece with a single coil, for example. This circuit is of a type in which one pole of a permanent magnet M of a pendulum is driven to face a coil L2 as shown in FIG. 5 and a circuit in which two poles of a permanent magnet are faced to a coil L2 as shown in FIG. It can be used for both of the driving type. Here, the operation when the type shown in FIG. 6 is driven will be described. When the magnet M moves in the direction of the arrow as shown in FIG. 7A and faces the coil L2, a maximum induced voltage v1 of FIG. 8A is generated in the coil L2, which excites the magnet M in a direction to stop it. Conversely, as shown in FIG. 7B, the magnet M moves from the opposite direction and the coil L
2A, the maximum induced voltage v2 in FIG. 8A is generated which also excites the magnet M in the direction to stop. At this maximum point, that is, at the timing shown in FIG. 7A or 7B, it is most preferable from the viewpoint of efficiency to drive the magnet by supplying a drive current to the coil. Therefore, the threshold voltage of the transistor T2 in FIG. 4 is set to the voltage vr in FIG. As a result, when the induced voltage exceeds the voltage vr, the transistor T2 is turned off, and the transistor T1 is turned on. As shown in FIG. 8A, a drive current flows through the coil L2 at the timing of the induced voltage v1 and the magnet M is turned on. Be energized. [0008] The type shown in FIG. 5 is also set so that a drive current flows through the coil at the maximum point of the induced voltage in the same manner as described above. [0007] Generally, the amplitude of the induced voltage varies depending on the number of turns of the coil, the strength of the magnetic force of the magnet, the distance between the coil and the magnet, and the like. In the above-described conventional configuration, the drive timing of the coil may be shifted due to the variation in the amplitude of the induced voltage, and the drive efficiency may be reduced. That is, when the amplitude of the induced voltage is reduced as shown in FIG. 8B, for example, the timing at which the voltage reaches the voltage vr is delayed, and the drive current flows through the coil later than the optimum timing. Conversely, when the amplitude of the induced voltage increases, the drive current flows through the coil earlier than the optimum timing, and in any case, the drive efficiency is reduced. Therefore, in order to maintain the driving efficiency at an optimum, it is necessary to eliminate variations in various factors affecting the amplitude of the induced voltage, and precision in manufacturing and assembling is strictly required. According to the present invention, a reference voltage for detecting an induced voltage from a coil is set to a low level in which the amplitude variation of the induced voltage is small, and the induced voltage of the coil is reduced. By generating a drive pulse delayed by a predetermined time when the voltage exceeds the reference voltage, the coil can be driven at an efficient timing without being affected by the amplitude of the induced voltage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A coil for generating an induced voltage with the reciprocation of a permanent magnet and energizing the movement of the permanent magnet, a driving transistor connected in series to the coil,
A comparison circuit that compares an induced voltage of the coil generated at a connection point between the drive transistor and the coil with a reference voltage and generates an output when the induced voltage of the coil exceeds the reference voltage; And an output generating circuit for generating a drive pulse of a predetermined width with a delay of a predetermined time from the generation of the output from the drive circuit to operate the drive transistor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, L1 is a permanent magnet (not shown). )
Is a reference voltage generating source, which is set so as to generate a lower reference voltage vr than in the prior art, as shown in FIG. CM is a comparison circuit for comparing the induced voltage of the coil L1 with the reference voltage vr. G1 and G2 are gate circuits, and G3 is a gate circuit constituting a control circuit. W1 to W3 are one-shot pulse generation circuits for generating pulses having widths T1 to T3, respectively. One-shot pulse generators W1 and W2 constitute an output generator, and one-shot pulse generators W2 and W3 and gate circuits G1 and G2 constitute an inhibit circuit. T is a drive transistor. In the above configuration, the induced voltage of the coil L1 is compared with the reference voltage vr by the comparison circuit CM, and when the induced voltage exceeds the reference voltage vr as shown in FIG. The one-shot pulse generation circuit W1 is triggered via the gate circuit G1, and a pulse having a width T1 is generated from its output. The time T1 is set to a time from when the induced voltage exceeds the reference voltage vr to when a drive pulse is generated at an optimum timing at the maximum point of the induced voltage. That is, the falling of the pulse triggers the one-shot pulse generation circuit W2, and a drive pulse having a width T2 is generated from its output. The transistor T is turned on by this driving pulse, and the coil L1
, A driving current flows, and the magnet is energized at an optimal timing. The falling of the drive pulse triggers the one-shot pulse generation circuit W3, and a pulse having a width T3 is generated from its output. This pulse and the preceding drive pulse are supplied to the gate circuit G2, and the gate circuit G1 is closed during the generation of each pulse. That is, during the times T2 and T3 in FIG. 2, even if an output is generated from the comparison circuit CM, the one-shot pulse generation circuit W1 is not triggered, and malfunction is prevented. This is because the reference voltage vr is set to a low level, so that the induced voltage may exceed this reference voltage even at times other than the local maximum, and in this case, a drive pulse is prevented from being generated. . The output of the one-shot pulse generating circuit W1 may also be supplied to the gate circuit G2 so that the gate circuit G1 is closed during the time T1. Incidentally, although omitted in the above description, the output of the one-shot pulse generation circuit W1 is supplied to the gate circuit G3, and the gate circuit G3 is open while the pulse is being generated. . Therefore, during this time, the comparison circuit C
When the output of M stops, the one-shot pulse generation circuit W
1 to W3 are reset, and no drive pulse is generated. This is to prevent malfunction due to noise or induced voltage other than the maximum point. When the voltage exceeds the reference voltage vr continuously for the time T1 or more, it is regarded as the maximum induced voltage. Is to be generated. In the above configuration, even if the amplitude of the induced voltage is reduced as shown in FIG. 2B, the reference voltage vr is set to a low level, so that the amplitude fluctuation in this vicinity is extremely small. Figure 2 shows the output timing of
It is almost the same as A. Therefore, the generation timing of the drive pulse is hardly shifted, and the drive pulse can be reliably generated at the maximum point of the induced voltage. The same applies to the case where the amplitude of the induced voltage increases. In the above example, the case where a two-pole magnet as shown in FIG. 6 is used has been described. However, the same can be applied to a case where a one-pole magnet as shown in FIG. 5 is used.
The induced voltage waveform in this case is as shown in FIG. 3, and the drive current flows through the coil at the maximum point of the induced voltage in the same manner as described above. According to the present invention, when the induced voltage of the coil exceeds the reference voltage, the drive current is supplied to the coil with a delay of a predetermined time, so that the reference voltage is set to a low level. Therefore, the generation timing of the drive pulse is hardly affected by the fluctuation of the induced voltage, and the drive current can be supplied to the coil at an efficient timing. Therefore, high precision is not required for the manufacturing and assembling, and the manufacturing and assembling process can be simplified.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electric circuit diagram showing one embodiment of the present invention. FIG. 2 is a voltage waveform diagram for explaining the operation of FIG. FIG. 3 is a voltage waveform diagram when the circuit of FIG. 1 is used in another example. FIG. 4 is an electric circuit diagram showing an example of a conventional electromagnetic drive circuit. FIG. 5 is an explanatory diagram showing an example of a relationship between a permanent magnet and a coil of a pendulum. FIG. 6 is an explanatory diagram showing another example of the relationship between the pendulum and the permanent magnet. FIG. 7 is an explanatory diagram showing excitation polarities of a coil in the example of FIG. 6; FIG. 8 is a voltage waveform diagram for explaining the operation of FIG. [Explanation of Signs] L1 ... coil Vr ... reference voltage source CM ... comparison circuits W1 to W3 ... one-shot pulse generation circuit T ... drive circuit G3 ... control circuit

Claims (1)

(57) [Claims] A coil that generates an induced voltage with the reciprocation of the permanent magnet and energizes the movement of the permanent magnet, a drive transistor connected in series to the coil, and a connection point generated between the drive transistor and the coil. A comparison circuit that compares the induced voltage of the coil with the reference voltage and generates an output when the induced voltage of the coil exceeds the reference voltage; and a drive pulse having a predetermined width delayed by a predetermined time from the generation of the output from the comparison circuit. And an output generating circuit for operating the driving transistor to generate the driving transistor.