JPH04340702A - Detecting equipment for counter electromotive force of coil - Google Patents

Abstract

PURPOSE:To obtain a detecting equipment for a counter-electromotive force of a coil which equipment can detect an abnormal counter-electromotive force generated in the coil. CONSTITUTION:A driving circuit switches the part between a coil 1 and a power supply 2 and absorbs a counter-electromotive force generated in a coil 1 with a counter-electromotive force absorbing element 4. In the above circuit, a Zener diode 7 whose Zener voltage is set to be higher than the counter- electromotive force generated in coil 1 in the normal state is connected with the coil 1. When the counter-electromotive force generated in the coil 1 is abnormally high, the Zener diode 7 is turned into a closed circuit state, so that said state is detected by a control means 12, which controls the switching action of a transistor 3. Thereby the current flowing into the coil 1 is automatically cut off, and breakdown of the counter-electromotive force absorbing element 4 is prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil back electromotive force detection device.

0002

2. Description of the Related Art When a coil of an electromagnet or other electromagnetic device is excited, a back electromotive force is generated in the coil. Therefore, in order to eliminate the influence of this back electromotive force, back electromotive force absorbing elements are connected to both ends of the coil.

0003

[Problem to be solved by the invention] The back electromotive force absorption element can absorb normal back electromotive force, but if the potential of the back electromotive force is abnormally high due to malfunction etc., the back electromotive force absorption element May be destroyed by back electromotive force.

0004

[Means for Solving the Problems] The invention according to claim 1 provides a transistor that opens and closes between a coil and a power source, a back electromotive force absorbing element connected to both ends of the coil, and a back electromotive force absorbing element connected to both ends of the coil. The device includes a Zener diode whose Zener voltage is set to a voltage higher than the voltage normally generated in the coil, and a control means that detects the operation of the Zener diode and controls the opening/closing operation of the transistor.

According to a second aspect of the invention, in the first aspect, a control means is connected between the Zener diode and a resistor connected to the Zener diode, and a capacitor is connected across the resistor.

[0006] The invention according to claim 3 provides a transistor for opening and closing between a coil and a power source, a back electromotive force absorbing element connected to both ends of the coil, and a back electromotive force absorbing element connected to the coil and when the Zener voltage is normally It is constructed of a Zener diode set to a voltage higher than the voltage generated in the coil, and a control means that detects the operation of the Zener diode and controls the display section.

[0007]

[Operation] According to the invention of claim 1, the back electromotive force generated in the coil is absorbed by the back electromotive force absorbing element, and when the back electromotive force is abnormally high, the Zener diode becomes a closed circuit. By detecting this and controlling the opening/closing operation of the transistor, it is possible to automatically cut off the current to the coil to prevent destruction of the back electromotive force absorption element and to prevent the effect on other circuits. Become.

[0008] In the invention of claim 2, even after the back electromotive force is reduced by a time constant determined by the resistor and the capacitor, a potential exists between the Zener diode and the resistor, so that a change in this potential can be prevented. Detection can be performed at arbitrary time intervals, and therefore a state in which an abnormal back electromotive force is generated can be easily detected.

According to the third aspect of the present invention, the state of the Zener diode is detected by the control means, and when an abnormally high back electromotive force is generated, the state can be displayed on the display section.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention according to claim 1 will be described with reference to FIGS. 1 and 2. 1 is a coil in an electromagnet; one end of this coil 1 is connected to a power source 2, and the other end is connected to the collector of a transistor 3. Further, a back electromotive force absorbing circuit 6 formed by connecting a Zener diode 4 and a diode 5 in series, which are back electromotive force absorbing elements, is connected to both ends of the coil 1. Furthermore, the Zener diode 7 and the resistor 8, whose Zener voltage is set to a voltage higher than the voltage generated in the coil 1 under normal conditions, connect the coil 1 and the transistor 3.
The connection between these Zener diodes 7 and the resistor 8 is connected to the positive side of a comparator 9, and the negative side of the comparator 9 is connected to resistors 10 and 11. The output side of the comparator 9 is connected to the control means 12 . This control means 12
turns off the transistor 3 when the output of the comparator 9 is input. For this purpose, the output terminal of the control means 12 is connected to the base of the transistor 3.

In such a configuration, the transistor 3
is turned on and off in response to the base voltage from the control means 12.
When the switch is turned on, current flows through the coil 1. At this time, a back electromotive force is generated in the coil 1, but when the back electromotive force becomes higher than the zener voltage of the zener diode 7, the zener diode 7 is turned on, and the potential between the zener diode 7 and the resistor 8 becomes the comparator. 9 is input. The comparator 9 outputs an output to the control means 12 when the input voltage becomes higher than the reference voltage determined by the resistors 10 and 11. The control means 12 turns off the transistor 3 based on the output from the comparator 9.

[0012] In this way, when the back electromotive force generated in the coil 1 becomes abnormally high, the current supply to the coil 1 is cut off, thereby preventing the elements of the back electromotive force absorption circuit 6 from being destroyed and preventing damage to other circuits. influence can be prevented.

Next, an embodiment of the invention of claim 2 is shown in FIG.
This will be explained based on FIG. Components that are the same as those in the embodiment described above are designated by the same reference numerals, and description thereof will be omitted (the same applies hereinafter). In this embodiment, a capacitor 13 is connected to both ends of a resistor 8.

In such a configuration, when the back electromotive force generated in the coil 1 becomes higher than the Zener voltage of the Zener diode 7, the Zener diode 7 is turned on, and the potential between the Zener diode 7 and the resistor 8 becomes the comparator 9.
is input. The comparator 9 outputs an output to the control means 12 when the input voltage becomes higher than the reference voltage determined by the resistors 10 and 11. The control means 12 turns off the transistor 3 based on the output of the comparator 9. At this time, due to the time constant determined by the resistor 8 and capacitor 13, voltage is applied to the comparator 9 even after the back electromotive force has decreased, so it is possible to detect changes in this voltage at arbitrary time intervals. can. Therefore, a state in which an abnormal back electromotive force is generated can be easily detected.

Furthermore, an embodiment of the invention according to claim 3 is shown in FIG.
This will be explained based on FIG. In this embodiment, the control means 12
A display section 14 is connected to the display section 14.

Therefore, when the back electromotive force generated in the coil 1 becomes abnormally high, the control means 12 receives the output from the comparator 9 and turns off the transistor 3 to cut off the current supply to the coil 1. The state of occurrence of back electromotive force (error display) is displayed on the display unit 14.

[0017]

Effects of the Invention The invention according to claim 1 provides a transistor that opens and closes between a coil and a power source, a back electromotive force absorbing element connected to both ends of the coil, and a transistor connected to the coil that has a Zener voltage normally Since the configuration includes a Zener diode set to a voltage higher than the voltage generated in the coil, and a control means that detects the operation of the Zener diode and controls the opening/closing operation of the transistor, the back electromotive force generated in the coil can be reduced. is absorbed by the back electromotive force absorption element,
If the back electromotive force is abnormally high, the Zener diode will close, so by detecting this state and controlling the opening/closing operation of the transistor, the current to the coil will be automatically cut off and the back electromotive force will be removed. This has effects such as being able to prevent damage to the power absorption element and also prevent influence on other circuits.

According to a second aspect of the invention, in the first aspect, a control means is connected between the Zener diode and the resistor connected to the Zener diode, and a capacitor is connected across the resistor. Because a potential exists between the Zener diode and the resistor even after the back emf has decreased by a time constant determined by This has the effect of easily detecting a state in which an abnormal back electromotive force is generated.

The invention according to claim 3 provides a transistor for opening and closing between a coil and a power source, a back electromotive force absorbing element connected to both ends of the coil, and a back electromotive force absorbing element connected to the coil and when the Zener voltage is normal. The structure consists of a Zener diode set to a voltage higher than the voltage generated in the coil, and a control means that detects the operation of this Zener diode and controls the display, so the state of the Zener diode is detected by the control means and an abnormality is detected. This has the effect that when a high back electromotive force is generated, the state can be displayed on the display section.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the invention according to claim 1.

FIG. 2 is a timing chart thereof.

FIG. 3 is a circuit diagram showing an embodiment of the invention according to claim 2.

FIG. 4 is a timing chart thereof.

FIG. 5 is a circuit diagram showing an embodiment of the invention according to claim 3.

FIG. 6 is a timing chart thereof.

[Explanation of symbols]

1 Coil 2 Power supply 3 Transistor 4 Back electromotive force absorption element 7 Zener diode 8 Resistance 12 Control means 13 Capacitor 14 Display section

Claims (3)

[Claims] 1. A transistor that opens and closes between a coil and a power source, a back electromotive force absorbing element connected to both ends of the coil, and a Zener voltage that is connected to the coil and that is normally generated in the coil. 1. A back electromotive force detection device for a coil, comprising a Zener diode set to a higher voltage, and a control means for detecting the operation of the Zener diode and controlling the opening/closing operation of the transistor. 2. The coil back electromotive force detection according to claim 1, wherein a control means is connected between the Zener diode and a resistor connected to the Zener diode, and a capacitor is connected to both ends of the resistor. Device. 3. A transistor that opens and closes between a coil and a power source, a back electromotive force absorbing element connected to both ends of the coil, and a Zener voltage that is connected to the coil and that is normally generated in the coil. A coil back electromotive force detection device comprising a Zener diode set to a higher voltage and a control means for detecting the operation of the Zener diode and controlling a display section.