JPH07107551B2 - Electromagnetic drive circuit - Google Patents

Description

The present invention relates to an electromagnetic drive circuit used for driving a pendulum or the like.

[Prior Art] For example, there is a drive circuit shown in FIG. 3 as a drive circuit for detecting and driving a pendulum of a timepiece with one coil. In operation of this circuit, as in the pendulum of the permanent magnet M is Figure 4 A, approaches the coil L _2, the induced voltage is generated in the direction to repel the magnets M to the coil L _2, Fig. 4 B Like a magnet M
Is opposite to the coil L ₂ , the induced voltage becomes 0, and when the magnet M is separated from the coil L ₂ as shown in FIG. 4C, the induced voltage is generated in the coil L ₂ in the direction of attracting the magnet. The polarity of the induced voltage varies depending on the winding direction of the coil L ₂ as shown in FIG. 5A or 5C. First, Fig. 5A
To explain the operation when the induced voltage of
The base voltage of the transistor T ₂ is clamped to a constant voltage V as shown in FIG. 5B by the diode characteristic of its base-emitter, but the fifth voltage generated at the terminal p of FIG.
When the induced voltage in FIG. A falls, this fall is caused by the capacitor C.
The lower the base voltage of the transistor T ₂ through, and becomes equal to or less than the threshold voltage v _t, the transistor T ₂ is turned off. Therefore, the transistor T ₁ is turned on, the drive current flows through the coil L ₂ for the time t ₁ determined by the time constant of the capacitor C ₁ and the resistor R ₁ , and the magnet M is attracted and driven.

Further, when the induced voltage is generated as shown in FIG. 5C, the base voltage of the transistor T ₂ becomes almost equal to the voltage V _{1 due} to its diode characteristic even if the voltage at the terminal p rises as shown in FIG. 5C. Is held. Then, when the above-mentioned induced voltage exceeds the peak, the base voltage of the transistor T ₂ also decreases due to the voltage drop, and the transistor T ₂ turns off when the voltage drops below the threshold voltage v _{t. A} driving current flows through the magnet ₂ , and the magnet M is repulsively driven.

That is, the base voltage of the transistor T ₂ is normally held at the voltage V, as shown in FIGS. 5B and 5C, but it rises via the capacitor C only when the voltage at the terminal p falls. The voltage follows the downward movement. for that reason,
In FIG. 5A, the base voltage of the transistor T ₂ becomes lower than the threshold voltage when the terminal p decreases from the voltage 0 by a constant voltage, and in FIG. 5C, the voltage of the terminal P decreases from the peak value by the constant voltage. By the way, the base voltage of the transistor T ₂ drops below the threshold voltage and the coil
The drive current will flow through L ₂ .

[Problems to be Solved by the Invention] In order to efficiently drive a magnet, in the case of suction drive, the coil is driven at the timing of FIG. 4A, and in the case of repulsive drive, the coil of FIG. It is preferable to drive the coil at a timing.

However, in the above configuration, the drive timing may be shifted depending on the winding direction of the coil, so that the drive may not be efficiently performed. That is, in the case of FIG. 5A, there is no problem because it is driven at the timing of FIG. 4A, but when the winding direction is opposite, as shown in FIG. The repulsive drive of the coil was started from a timing slightly before B, resulting in extremely low efficiency.
Therefore, it is necessary to assemble the circuit in consideration of the winding direction of the coil during manufacturing.

In addition, it is vulnerable to power supply noise, and the drive pulse of the coil may be generated due to fluctuations in the power supply voltage due to noise.

The present invention makes it possible to drive the coil always at an efficient timing regardless of the winding direction of the coil with an extremely simple structure.

[Means for Solving Problems] According to the present invention, a pulse having a predetermined width is generated when an output of a comparison circuit is generated when an induced voltage generated at a connection point between a coil and its driving transistor exceeds a reference voltage. The above-mentioned object is achieved by generating and supplying a drive current to the coil.

[Embodiment] In FIG. 1, L ₁ is a detection and drive coil of a permanent magnet (not shown), V _r is a reference voltage source, and CM is a comparison circuit for comparing the induced voltage of the coil L ₁ with the reference voltage. is there. W is a one-shot pulse generation circuit, and T is a transistor that forms a drive circuit.

In the above configuration, the induced voltage in coil L ₁ is
Reference voltage v is compared with _r, the induced voltage is the reference voltage v _r by
When it exceeds, the comparison circuit CM produces an output, and the one-shot pulse generation circuit W produces a pulse of time t. This pulse turns on the transistor T and the coil
A drive current flows through L ₁ to drive the permanent magnet.

That is, according to the winding direction of the coil L ₁ , the coil L ₁ shown in FIG.
Alternatively, an induced voltage is generated as in B, but in any case, when this induced voltage exceeds the reference voltage v _r , the time t
The drive current flows only during the period. Therefore, regardless of the winding direction of the coil, the drive current always flows at the peak of the induced voltage, and the drive is efficiently performed.

According to the present invention, the induced voltage generated at the connection point between the coil and its drive transistor is constantly compared with the reference voltage, and the output of the comparison circuit when the induced voltage exceeds the reference voltage. Since the coil is driven in synchronization with the generation, the coil can be always driven efficiently and at the optimum timing regardless of the winding direction of the coil with an extremely simple configuration.
Therefore, at the time of manufacture, the coil can be assembled without considering the winding direction of the coil, and the assembling time can be shortened.

Moreover, since it is resistant to noise on the power supply line and no capacitor is used, it is suitable for integration.

[Brief description of drawings]

1 is an electric circuit diagram showing an embodiment of the present invention, FIG. 2 is a voltage waveform diagram for explaining the operation of FIG. 1, and FIG. 3 is an electric circuit showing an example of a conventional electromagnetic drive circuit. 4 and 5 are explanatory views showing the positional relationship between the coil and the permanent magnet, and FIG. 5 is a voltage waveform diagram for explaining the operation of FIG. L ₁ …… Coil V _r …… Reference voltage generation source CM …… Comparison circuit W …… Pulse generation circuit T …… Drive transistor

Claims (1)

[Claims] 1. A coil for detecting and driving a permanent magnet,
When the drive transistor connected in series to this coil and the induced voltage of the coil generated at the connection point between the drive transistor and the coil are constantly compared with each other, and the induced voltage of the coil exceeds the reference voltage. An electromagnetic drive circuit comprising: a comparison circuit that produces an output and an output generation circuit that generates a drive pulse of a predetermined width and operates the drive transistor in synchronization with the generation of an output from the comparison circuit.