JPH0592586A - Electromagnetic drive circuit - Google Patents

Abstract

PURPOSE:To make attracting time of reverse inductive power faster so as to shorten quenching time of field and improve responsiveness at load driving, by flowing current to other coil connected to a coil which drives load when the reverse inductive power is generated in this coil. CONSTITUTION:When a transistor 4 is made to be a conductive state, current flows to a first coil 1 and load is driven. At this time, a current 12 which is going to flow to a second coil 2 is stopped at a diode 3a in the reverse direction. On the other hand, when the state of the transistor 4 is changed to a non- conductive state, a reverse inductive power generates in the first coil 1. At this time, a current 11 caused by the reverse inductive power is attracted at a diode 3b in the forward direction. In this case, the current 12 is inducted to the second coil 2 by the reverse inductive power generated at the first coil 1. The current 12 is attracted at the diode 3a in the forward direction. Thus, the magnetic field generated in the first coil 1 is weakened and quenched quickly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic drive circuit.

[0002]

2. Description of the Related Art Conventionally, an electromagnetic drive circuit has been used, for example, in an impact printer to drive a print pin. As shown in FIG. 4, the configuration is such that a coil 1'for driving a load such as a print pin, a transistor 2'for controlling the current supply to the coil 1 ', and a current supply to the coil 1'. And a diode 3'which absorbs a back electromotive force generated in the coil 1'when the coil is stopped. This is because the load is driven by the magnetic force generated when the transistor 2'is turned on and a current is supplied to the coil 1 ', and the back electromotive force generated in the coil 1'when the transistor 2'is turned off is converted into a diode. The current is extinguished quickly by passing a current through 3 '.

[0003]

Recently, there has been a strong demand for high-speed printing for printers, and manufacturers are developing printing means for realizing higher-speed printing. Improving the responsiveness of the printing pin is considered as one means for realizing high-speed printing, but the conventional electromagnetic drive circuit described above can absorb the back electromotive force generated in the coil 1'to such an extent that it can meet the above demand. I could not shorten the time required. Therefore, it takes a long time to extinguish the magnetic field generated in the coil 1 ', which hinders the improvement of the responsiveness of the print pin.

It is an object of the present invention to provide an electromagnetic drive circuit with better response.

[0005]

According to the present invention, there is provided a first coil for driving a load, a second coil magnetically coupled to the first coil, and a back electromotive force generated in the first coil. The above problem is solved by providing current control means for causing a current to flow through the second coil when the above occurs.

[0006]

First, a first embodiment of the present invention will be described with reference to FIG.

In the figure, 1 is a first coil for driving a load such as a print pin of an impact printer, 2 is a second coil magnetically coupled to the first coil 1, and The coil 1 and the second coil 2 are wound around the same core in the same direction. 3a and 3b are diodes. The diode 3a is a current control means for supplying a current to the second coil 2 when a back electromotive force is generated in the first coil 1. Reference numeral 4 is a transistor that controls the supply of current to the first coil 1.

Next, the operation will be described. First, when the transistor 4 is turned on, the current I1 flows through the first coil 1 to drive the load. At this time, the current -I2 tends to flow through the second coil 2 due to electromagnetic induction, but since the direction thereof is the direction opposite to that of the diode 3a, the current -I2 does not flow.
Therefore, when driving the load, the current I1 flows without being affected by the magnetic field of the second coil 2.

Next, when the transistor 4 is switched from the conducting state to the non-conducting state, the current I1 flowing in the first coil 1 is about to stop, so that the back electromotive force is generated in the first coil 1 at this time. To do. Since the direction of the current I1 due to this back electromotive force is the forward direction of the diode 3b, it is absorbed by the diode 3b and the magnetic field generated in the first coil 1 disappears. Up to this point, it is the same as the conventional one, but in the present example, the second coil 2
A current I2 is induced at. Since the direction of the current I2 is the forward direction of the diode 3a, the current I2 is absorbed by the diode 3a. The magnetic field generated in the first coil 1 is also weakened by this current I2, so that the magnetic field generated in the first coil 1 disappears earlier than in the conventional case.

Next, a second embodiment according to the present invention will be described with reference to FIG.
It will be explained based on.

In the figure, the same numbers as in FIG. 1 indicate the same items. The operation will be described. When the transistor 4 is turned on, the current I1 flows through the first coil 1 to drive the load. At this time, depending on the direction of the diode 3a, the second
No current flows through the coil 2 of.

Next, when the transistor 4 is turned off, the current I1 tends to stop, so that the first coil 1
A back electromotive force is generated at. Current I due to this back electromotive force
1 is absorbed by the diode 3b. Further, the current I2 is induced in the second coil 2 by the back electromotive force generated in the first coil 1. Since the direction of the current I2 is the forward direction of the diode 3a, the current I2 is absorbed by the diode 3a. With the above operation, like the first embodiment, the magnetic field generated in the first coil 1 can be quickly extinguished, but in the second embodiment, the current I2 is fed back to the power source, and Energy consumption of the drive circuit can be reduced.

Next, a third embodiment according to the present invention will be described with reference to FIG.
It will be explained based on.

In the figure, 3a is a diode, 4 is a transistor, and 5 is a coil with a midpoint tap. Next, the operation will be described. First, when the transistor 4 is turned on, the current I1 flows and the load is driven.

Next, when the transistor 4 is turned off, the current I1 tends to stop, so that a magnetic field is generated in the coil 5 by the back electromotive force. This magnetic field causes the current I2
Current flows in the forward direction of the diode 3a, the current I2 is absorbed by the diode 3a, and the magnetic field generated in the coil 5 disappears.

[0016]

According to the present invention, it is possible to shorten the absorption time of the back electromotive force generated in the coil for driving the load and shorten the disappearance time of the magnetic field. Responsiveness is improved. For example, when used in an impact printer, the response frequency of the printing pin is improved, and printing can be performed at higher speed.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing a first embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing a second embodiment of the present invention.

FIG. 3 is an electric circuit diagram showing a third embodiment of the present invention.

FIG. 4 is an electric circuit diagram showing a conventional example.

[Explanation of symbols]

 1 1st coil 2 2nd coil 3a diode

Claims (1)

[Claims] 1. A first coil for driving a load, a second coil magnetically coupled to the first coil, and the second coil when a back electromotive force is generated in the first coil.
And a current control means for supplying a current to the coil.