JPH0630538B2 - Solenoid drive circuit abnormality detection device - Google Patents

Description

The present invention relates to an abnormality detection device for a solenoid drive circuit.

[Prior Art] If an excessive current flows to the solenoid due to some accident such as a solenoid failure, the solenoid will be in a considerably high temperature state, and if it has a small capacity, there is a problem of burnout. It adversely affects circuit elements. For this reason, a circuit for detecting an excessive current flowing in the solenoid drive circuit is incorporated.

As such a device, the one shown in FIG. 4 is conventionally known. That is, one end of the solenoid 1 is + V ₁
The other end is connected to the power supply terminal and the other end is connected to the ground point via the NPN transistor 2 and the resistor 3 which are switching elements in series, and the resistors 4 and 5 are connected in series between the + V ₂ power supply terminal and the ground point. The voltage divider circuit for generating the reference voltage connected to is connected. An input signal S _I for controlling a solenoid is input to the base of the transistor 2 via a resistor 6. The inspection voltage E ₁ generated in the resistor 3 and the resistor 4,
The comparator 7 compares the reference voltage E ₂ generated at the connection point of 5 with the comparator 7, and outputs the signal S ₀ from the output terminal of the comparator 7.

In this circuit, when the input signal S _I as shown in FIG. 5A is input, the transistor 2 is turned on during the high level period of the signal, and the current flows through the solenoid 1.
At this time, the inspection voltage E ₁ as shown in FIG. Then, when a normal current flows through the solenoid 1, the level of the inspection voltage E ₁ is lower than the level of the reference voltage E ₂ , so that the output S ₀ from the comparator 7 is always as shown in (c) of FIG. It is in a low level state. However, when an excessive current flows through the solenoid 1 due to a failure of the solenoid 1 or the like, the level of the inspection voltage E ₁ generated in the resistor 3 is higher than that of the reference voltage E ₂ as shown by the alternate long and short dash line in FIG. 5B. Also, the comparator 7 outputs a high-level abnormality detection signal as indicated by the alternate long and short dash line in FIG. 5 (c). In this way, when an excessive current flows through the solenoid 1, it is detected and notified.

[Problems to be Solved by the Invention] However, if the transistor 2 in this circuit fails and becomes conductive, current continues to flow in the solenoid 1, but as shown by the alternate long and short dash line in FIG. Since the inspection voltage E ₁ generated in the resistor 3 is lower than the reference voltage E ₂ level forever as long as the current amount is normal, there is a problem that the comparator 7 cannot detect abnormality forever. Therefore, even if the current amount is normal, the current continues to flow through the solenoid 1, which causes problems such as malfunction of the solenoid 1 and abnormal heat generation resulting in shortened life.

The present invention has been made in order to solve such a problem, and it goes without saying that an abnormality is detected when an excessive current flows in the solenoid, and an abnormality detection that the switching element is in a conductive state and current continues to flow in the solenoid. It is an object of the present invention to provide an abnormality detection device for a solenoid drive circuit that can reliably perform the above.

[Means for Solving the Problems] In the solenoid drive circuit for turning on the switching element in response to an input signal and energizing the solenoid for a predetermined time, the present invention provides a test voltage for generating the amount of current flowing through the solenoid in a resistor. , And compares the inspection voltage with the reference voltage for abnormality detection generated by the reference voltage generation circuit in the comparator, and outputs the abnormality detection signal when the inspection voltage is equal to or higher than the reference voltage. In response to the input signal, a level change means for changing the reference voltage level from the reference voltage generation circuit is provided, and the reference voltage level from the reference voltage generation circuit is supplied to the solenoid in response to the input signal. Set to a level slightly higher than the level of the inspection voltage generated in the resistance when flowing, and respond to the stop of the input signal The reference voltage level from the voltage generation circuit is set to a level lower than the level of the inspection voltage generated in the resistance when a normal current flows through the solenoid.

[Operation] In the present invention having such a configuration, the switching element is turned on by an input signal, and when an excessive current flows through the solenoid at that time, the level of the inspection voltage generated in the resistor becomes equal to or higher than the level of the reference voltage and abnormal Detection is possible, and when the input signal is stopped when the switching element fails and becomes conductive, the level change means causes the level of the reference voltage to exceed the level of the inspection voltage generated in the resistor when a normal current flows through the solenoid. Since the value is also changed to a low value, abnormality can be detected in this case as well.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, one end of the solenoid 11 is connected to the + V ₁ power supply terminal, and the other end of the solenoid 11 serves as a switching element.
A PN type first transistor 12 and a resistor 13 are connected in series to a ground point. Also, the resistors 14, 15, 1
6 are connected in series to form a reference voltage generating circuit 17, one end of which, that is, one end of the resistor 14 is connected to the + V ₂ power supply terminal, and the other end, that is, one end of the resistor 16 is connected to the ground point. The base of the first transistor 12 is connected to the input terminal 19 of the input signal S _I via the resistor 18.

Further, a comparator 20 is provided, the connection point P between the emitter of the first transistor 12 and the resistor 13 is connected to the non-inverting input terminal (+) of the comparator 20, and the inverting input terminal (-) thereof is connected.
Is connected to the connection point Q of the resistors 14 and 15. The comparator 20 compares the voltage levels of the connection points P and Q, and when the level of the connection point P becomes equal to or higher than the level of the connection point Q, outputs a high level output signal S ₀ to the output terminal 21 as an abnormality detection signal. I have to.

A second NPN-type transistor 22 is connected in parallel to the resistor 16, and the input terminal 19 is connected to the base of the transistor 22 via an inverter 23 and a resistor 24 in series to form level changing means. .

In the embodiment of the present invention having such a structure, when the input signal S _I as shown in FIG. 2A is input to the input terminal 19, the first transistor 12 is turned on during the high level period of the signal. Then, a current flows through the solenoid 11.
Further, during the low level period of the signal, the first transistor 12 is turned off and the energization of the solenoid 11 is stopped. Then, when the first transistor 12 is turned on, the current flowing through the solenoid 11 flows through the resistor 13, so that the voltage at the connection point P, that is, the inspection voltage E ₁ is the input signal S as shown in FIG. _{When I} is at a high level, it rises to a certain potential. On the other hand, when the input signal S _I is at the high level, the second transistor 22 is turned off and the reference voltage E ₂ which is the voltage at the connection point Q rises. Conversely, when the input signal S _I is at the low level, the second transistor 22 is turned on. Since 22 is turned on and short-circuits the resistor 16, the reference voltage E ₂ which is the voltage at the connection point Q is lowered. That is, the reference voltage E ₂ also rises and falls in level as shown in FIG. 2B in response to the presence or absence of the input signal S _I. Then, when the reference voltage E ₂ becomes a high potential, the level is the solenoid 1
1 is slightly higher than the inspection voltage E ₁ generated in the resistor 13 when a normal current flows through the resistor ₁ . Then solenoid 1
As long as the first and first transistors 12 are operating normally, the inspection voltage E _{1 at the} connection point P is the reference voltage E _{2 at the} connection point Q not only when the input signal S _I is at the low level but also when it is at the high level. Never exceeds. Therefore, the output of the comparator 20 is always in the low level state as shown in FIG.

However, if an abnormality occurs such that an excessive current flows through the solenoid 11 due to a failure of the solenoid 11 or the like, the inspection voltage E at the connection point P is indicated by the one-dot chain line in (b) of FIG.
₁ becomes larger and exceeds the reference voltage E ₂ . However, the comparator 20 outputs a high-level signal S ₀ as indicated by the alternate long and short dash line in FIG. 2C as an abnormality detection signal.

Moreover, since even current normal current flowing through the solenoid 11 and the failure first transistor 12 becomes conductive condition occurs the input signal S _I is current continues to flow to the solenoid 11 and the resistor 13 also becomes low level The inspection voltage E ₁ at the connection point P is maintained at the same level as when the input signal S _I is at the high level, as shown by the alternate long and short dash line in FIG. On the other hand, the reference voltage E ₂ becomes lower than the inspection voltage E _{1 when} the level of the input signal S _I becomes low level, the second transistor 22 is turned on. Therefore, also at this time, the comparator 20 detects an abnormal state and outputs the high-level signal S ₀ as an abnormal detection signal.

Thus, not only when the excessive current flows, but also when the first transistor 12 fails and the current continues to flow, it is possible to reliably detect the abnormality. Therefore, solenoid 1
It is possible to prevent the circuit element from being adversely affected by the abnormal heat generation of No. 1 and the accidental burnout of the solenoid, and the malfunction of the solenoid due to the destruction of the transistor and the shortening of the life of the solenoid can be prevented.

Next, another embodiment of the present invention will be described with reference to the drawings.
The same parts as those in the above embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 3, the reference voltage generating circuit 17 is formed by a series circuit of resistors 14 ', 15' and 16 ', and a PNP type third transistor 25 constituting a level changing means in the resistor 14'. Are connected in parallel and the transistor 25
The output terminal of the inverter 23 is connected to the base of the above through a resistor 24.

In this embodiment the input signal S _I to the contrary to the above embodiment will short-circuit the third transistor 25 is turned on operating resistance 14 'at a high level. When the resistor 14 'is short-circuited, the reference voltage E ₂ generated at the connection point Q rises. When the input signal S _I is at low level, the third transistor 2
5 is turned off, the reference voltage E ₂ is applied to the resistors 14 'and 1
The signal S is determined by the voltage division of the series circuit with 5'and the resistor 16 '.
_It is lower than when _I is at high level. Thus the level of the reference voltage E ₂ is increased when also the input signal S _I is at the high level in this embodiment, since the level of the reference voltage E ₂ is low when a low level, the foregoing embodiment the level of the time If the same value is set, the same effect as the above embodiment can be obtained.

It should be noted that in the above-described embodiment, a transistor is used as a switching element, but the invention is not limited to this, and a mechanical contact such as a relay may be used.

[Effects of the Invention] As described in detail above, according to the present invention, not only abnormality detection when an excessive current flows in the solenoid, but also abnormality detection that the switching element is in a conductive state and current continues to flow in the solenoid. It is possible to provide a reliable and highly reliable solenoid drive circuit abnormality detection device.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a voltage waveform diagram of each part in the same embodiment, FIG. 3 is a circuit diagram showing another embodiment of the present invention, and FIG. FIG. 5 is a circuit diagram showing an example, and FIG. 5 is a voltage waveform diagram of each portion in the conventional example. 11 ... Solenoid, 12 ... First transistor, 13 ...
Resistance, 17 ... Reference voltage generating circuit, 20 ... Comparator, 22 ...
Second transistor, 25 ... Third transistor.

Claims (1)

[Claims] 1. In a solenoid drive circuit for turning on a switching element in response to an input signal to energize a solenoid for a predetermined time, a resistor inserted in series in an energizing path to the solenoid and an anomaly detecting circuit. A reference voltage generating circuit for generating a reference voltage, a comparator for comparing the reference voltage from the reference voltage generating circuit with the inspection voltage generated in the resistor, and for outputting an abnormality detection signal when the inspection voltage is equal to or higher than the reference voltage; And level changing means for changing the reference voltage level from the reference voltage generating circuit in response to the presence or absence of the input signal, wherein the level changing means responds to the input signal and outputs the reference voltage from the reference voltage generating circuit. The voltage level is set to a level slightly higher than the level of the inspection voltage generated in the resistance when a normal current flows through the solenoid, and the input signal is stopped. In response to this, the reference voltage level from the reference voltage generating circuit is set to a level lower than the level of the inspection voltage generated in the resistor when a normal current flows through the solenoid. Anomaly detection device.