JP2588428B2 - Drive circuit abnormality detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit abnormality detection device that drives a load such as a solenoid by an AC power supply applied through a semiconductor element.

2. Description of the Related Art A drive circuit for driving a load such as a solenoid by applying an AC power supply that is turned on and off by a switch such as a switch or an auxiliary relay is widely known.

By the way, for example, when driving a solenoid valve that supplies air for clutch brake of a press machine, timely and accurate drive is required, and from the viewpoint of further improving safety, the components of the drive circuit are carefully selected. Has been scrutinized. As one of them, a rotary cam switch or a relay is often adopted as a switch of the drive circuit of the solenoid valve. The reason for this is that the semiconductor element has a symmetrical fault property, that is, a property of breaking on the conduction side or breaking on the interruption side.

[Problems to be Solved by the Invention] However, in a press machine or the like that requires a high speed and an ultra-high speed of 400 to 1000 Spm, a semiconductor element has to be used for the switch in terms of the following speed.

Thus, in a drive circuit using a semiconductor element, a reliable and fail-safe abnormality detection device is required for safe and smooth operation as well as for improving the reliability of the semiconductor element and the circuit system.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a drive circuit abnormality detection device capable of quickly and accurately detecting an abnormality and determining the content of the failure.

Means for Solving the Problems The present invention is formed so as to generate a fail-safe side, that is, an abnormality detection signal due to the relationship with other safety devices, especially when the semiconductor element interrupts the load current. .

That is, in a drive circuit for driving a load by an AC power supply applied through a semiconductor element, an abnormality formed in parallel with the semiconductor element and generating a pulse signal synchronized with the AC power supply in a state where the semiconductor element cuts off a load current. A detection circuit; an identification signal detection circuit that detects an identification signal of a current flowing through the abnormality detection circuit of the semiconductor element or a load current; and a determination circuit that determines an abnormality content from output signals of the abnormality detection circuit and the identification signal detection circuit. This is a configuration including:

[Operation] In the present invention having the above-described configuration, a pulse signal is generated when the semiconductor element interrupts the load current, and the abnormality detection circuit does not generate a pulse signal when the load current continues to flow. Then, the determination circuit determines the abnormality instantaneously. Also,
The determination circuit can specifically notify the contents of the abnormality based on the identification information from the identification signal detection circuit.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

 This embodiment is shown in FIG.

In the figure, 1 is an AC power supply, 2 is a triac (trade name) as a semiconductor element for bidirectional three-terminal control rectification, 3 is an electric circuit, 4 is a solenoid valve for operating a clutch brake of a press machine. , 2, 3, 4) constitute a drive circuit.

Here, the abnormality detection device for the drive circuit includes an abnormality detection circuit 10, an identification signal detection circuit 20, and a determination circuit 30.

First, the abnormality detection circuit 10 is formed on the fail-safe side which is connected in parallel with the semiconductor element 2 and generates a pulse signal when the load current is cut off. Specifically, as shown in FIG.
This is a power supply synchronous pulse detection method including a resistor 11 as an asymmetric failure element and a photocoupler 12.

Reference numeral 13 denotes a diode for reverse breakdown voltage protection. Also,
Semiconductor device 2 consisting of resistor 14 and capacitor 15 and photocoupler
A protection circuit with 12 is provided.

Therefore, the abnormality detection circuit 10 outputs a pulse signal when the semiconductor element 2 is cut off so that the load current cannot flow through the solenoid valve 4 as a load. The pulse signal is a short wave having a frequency equal to the frequency of the AC power supply 1. On the other hand, when a failure occurs in the conduction state, no pulse signal is generated.

Similarly, when the abnormality detection circuit 10, that is, the resistor 11 is broken in the cutoff state and the photocoupler 12 is damaged, the electric circuit 3,
No pulse signal is generated when the solenoid 4 fails. In other words, the failure detection circuit 10, the electric circuit 3, and the solenoid 4 are stochastically low in failure, and there are many inconveniences when the semiconductor element 2 is broken into a conductive state. .

Next, the identification signal detection circuit 20 is a means for identifying and detecting the low level current flowing through the abnormality detection circuit 10 and the high level load current of the semiconductor element 2. In this embodiment, the identification signal detection circuit 20 is connected to the electric circuit 3. Transformer 21 including coil and diode 22
It is composed of

Further, the determination circuit 30 is means for determining the content of the abnormality of the entire drive circuit as well as the semiconductor element 2 from the pulse signal from the abnormality detection circuit 10 and the identification signal from the identification signal detection circuit 20. Then, the abnormality detection signal and the identification signal are simply displayed in FIG. 1. When these signals are expressed in relation to the AC power supply voltage, they are as shown in FIG. 4. In FIG. (B), (c), and (d) show types of abnormalities determined based on the states of the abnormality detection signal and the identification signal. The type of this abnormality corresponds to that of FIG.

Specifically, the determination is made as shown in FIG. That is,
(A) If there is a pulse from the abnormality detection circuit and there is no pulse from the identification signal detection circuit, it can be said that the semiconductor element has failed. (B) In the case where there is no pulse from the abnormality detection circuit and there is a pulse from the identification signal detection circuit, it can be said that the semiconductor element is a failure in which conduction has occurred.
(C) When there is no pulse from the abnormality detection circuit and there is no pulse from the identification signal detection circuit, it can be said that the failure has occurred in the electric circuit. (D) If there is no pulse from the abnormality detection circuit and there is a pulse from the identification signal detection circuit, it can be said that the above-mentioned failure (b) has occurred. Further, if there is no pulse from the abnormality detection circuit and a low level pulse of the current flowing through the abnormality detection circuit from the identification signal detection circuit (the height of the pulse peak is low), the disconnection of the electric circuit in (c) will occur. Therefore, it can be said that the failure is caused by the failure of the abnormality detection circuit.

According to this embodiment, since the abnormality detection circuit 10 that generates a pulse signal when the semiconductor element 2 is in the cut-off state is provided in parallel with the semiconductor element 2, it becomes a fail-safe, and a countermeasure can be taken reliably and quickly. Can be taken. In other words, in a press machine, if the semiconductor element 2 breaks down in the conductive state, it becomes a serious matter that the press cannot be stopped without releasing the clutch brake. Does not generate a pulse signal, that is, the signal is cut off, so that fail-safe operation is performed. Therefore, the speed of the drive circuit of the solenoid valve 4 for clutch brake of the press machine can be increased.

In addition, since the abnormality detection circuit 10 is provided with the identification signal detection circuit 20 and the determination circuit 30, the conduction state of the semiconductor element 2, the disconnection of the electric circuit 3, and the failure of the abnormality detection circuit 10 itself can be known. . Therefore, more specific measures can be taken.

In the above embodiment, the semiconductor element 2 is a triac (trade name), but may be a thyristor 2 ', 2' as shown in FIG. In this embodiment, the first
The semiconductor element 2 of the embodiment shown in the figure, i.e., a phase-directional (bidirectional) semiconductor element, is replaced by two unidirectional semiconductor elements.
In the case of the phase-directional semiconductor element 2, if one of them fails, the output becomes a half-wave instead of a full-wave, so that the detection may be incomplete. In consideration of this point, in the present embodiment, only the phase-directional semiconductor device of the embodiment of FIG. 1 is replaced by two unidirectional semiconductor devices, and the other operation and effects are the same as those of the embodiment of FIG. And does not change.

Further, the identification signal detection circuit 20 includes the transformer 21 and the like, but may be formed by other means such as a photocoupler. However, in the case of a transformer, there is an advantage that the number of failures is small.

[Effects of the Invention] The present invention has a configuration in which an abnormality detection circuit that emits a pulse signal when a semiconductor element is in a cutoff state is provided, and an identification signal detection circuit and a determination circuit are provided. As a result, quick and reliable countermeasures can be taken for failsafe, and press machines and the like can be operated safely and at high speed.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, FIG. 2 is a diagram for explaining the same operation, FIG. 3 is a diagram showing another embodiment of the semiconductor device, and FIG. FIG. 4 is an explanatory diagram illustrating a relationship between an abnormality detection signal and the like and an AC power supply voltage. 1 AC power supply 2 Semiconductor element 3 Electric circuit 4 Solenoid valve 10 Abnormality detection circuit 20 Identification signal generation circuit 30 Judgment circuit

Claims (1)

(57) [Claims] 1. A drive circuit for driving a load by an AC power supply applied through a semiconductor element, wherein the drive circuit is connected in parallel to the semiconductor element and generates a pulse signal synchronized with the AC power supply in a state where the semiconductor element interrupts a load current. An abnormality detection circuit formed as described above, an identification signal detection circuit for identifying a current flowing through the abnormality detection circuit of the semiconductor element and a load current, and determining an abnormality content from output signals of the abnormality detection circuit and the identification signal detection circuit An abnormality detection device for a drive circuit comprising a determination circuit.