JP3025935B2 - Alarm signal mask circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for an alarm signal generator for generating an alarm signal for a fixed period when the power supply voltage of a live line into which a panel is inserted or removed becomes unstable. The present invention relates to an alarm signal mask circuit that masks unnecessary alarm signals generated at the time of insertion, removal, and when a panel is not mounted.

[0002]

2. Description of the Related Art Conventionally, electronic devices in which a panel on which a signal processing circuit is mounted can be arbitrarily inserted into and removed from a live line of a power supply are increasing. In such a device, if the power supply voltage becomes unstable in a panel mounted state, the signal processing operation is adversely affected. Therefore, it is common to perform control such as generating an alarm signal to stop the processing operation. It is.

Here, factors that make the power supply voltage unstable include power-on, insertion / removal of a panel, and external noise. Of these, an alarm signal is not required when the power supply voltage fluctuates due to external noise when the power is turned on, the panel is inserted and removed, and no pulse is mounted. Therefore, conventionally, the alarm signal generation device is provided with an alarm signal mask circuit as shown in FIG.

In FIG. 3, reference numeral 1 denotes an input terminal for inputting a mounting state signal indicating mounting / non-mounting of a panel (not shown), which is connected to a VCC power supply via a pull-up resistor 2. Specifically, the input terminal 1 is connected to a ground line of the panel by panel mounting. Therefore, the mounting state signal is at a low level in the mounting state, and is pulled up to a high level in the non-mounting state.

The mounting state signal thus generated is sent to the VS terminal of the voltage monitoring circuit 3. The voltage monitoring circuit 3 generates a mask signal (high level) for a certain period after the mounting state signal supplied to the VS terminal is at the high level and for a certain period after the level is inverted from the high level to the low level, and is output from the R terminal. The output period is determined by the capacitance (charging time) of the capacitor 4 connected between the CT terminal and the ground.

The mask signal output from the voltage monitoring circuit 3 is inverted to a low level by a NOT (inverting) circuit 5,
The signal is sent to one input terminal of an AND (logical product) gate circuit 6. An alarm signal is supplied to the other input terminal of the AND gate circuit 6 through an input terminal 7. The alarm signal monitors the power supply voltage of the live line by a separately provided voltage monitoring circuit, and when the power supply voltage falls below a certain level,
Generated for a certain period of time. The output period of the mask signal is set to a time sufficiently longer than the alarm signal generation period.

That is, the AND gate circuit 6 has a NO
When the output of the T circuit 5 is at a high level (a state in which the mask signal is not output), an alarm signal is derived to the output terminal 8 and N
When the output of the OT circuit 5 is at a low level (a state in which a mask signal is being output), a mask process for blocking the derivation of an alarm signal is performed.

In the above configuration, when the power is turned on as shown in FIG. 4A, for example, as shown in FIG. 4A, and the power supply voltage of the live line temporarily becomes unstable, as shown in FIG. An alarm signal is generated.

However, at this time, the mounting state signal temporarily goes to a high level as shown in FIG. 4B, and the voltage monitoring circuit 3 detects this, and as shown in FIG. Outputs a mask signal. As a result, FIG.
As shown in (e), the alarm signal is output from the AND gate circuit 6.
Will be cut off. This operation is the same immediately after the panel is inserted (mounted) into the live line.

On the other hand, when the panel is not mounted, since the mounted state signal is always at the high level, the mask signal is continuously output from the voltage monitoring circuit 3. Therefore, the alarm signal is not output when the panel is not executed.

Here, when the panel is removed from the live line, an alarm signal is also generated. However, since this alarm signal is unnecessary, mask processing is required. However, in the mask circuit having the above configuration, even if the panel is removed from the live line (becomes an unmounted state) and the mounting state signal is switched from low to high as indicated by A in FIG. The circuit 3 outputs a mask signal after the discharge of the capacitor 4.

For this reason, as shown by B in FIG.
The mask signal is output later than the generation of the alarm signal (see FIG. 4D). Therefore, an unnecessary alarm signal is temporarily output from the AND gate circuit 6 as indicated by C in FIG. 4E.

The delay of the alarm mask start time is proportional to the capacitance of the capacitor 4. Therefore, a circuit that discharges a capacitor as quickly as possible by adding a diode or the like to both ends of the capacitor 4 is also recommended. However, only the discharge time is shortened, and it is impossible to set the alarm mask start time simultaneously with the inversion of the output of the mounting state signal.

[0014]

As described above, the conventional alarm signal mask circuit cannot completely mask an alarm signal generated when a panel is removed from a live line.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an alarm signal masking circuit which can completely mask an alarm signal generated when a panel is removed from a live line. And

[0016]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is used in an alarm signal generator for generating an alarm signal for a certain period when the power supply voltage of a live line into which a panel is inserted or removed becomes unstable. Based on a mounting state signal indicating mounting / non-mounting of the panel obtained by monitoring the power supply voltage of the panel, an alarm signal is generated when the power is turned on, when the live line of the panel is inserted or removed, and when the panel is not mounted. In the alarm signal masking circuit, the first mask signal is always generated while the mounting state signal is at the level indicating non-mounting, and when the level is inverted from this level to the level indicating mounting, the first mask signal is generated for a fixed time from the detection point. Mask signal generating means, and OR gate means for calculating a logical sum of the first and second mask signals using a level indicating that the mounting state signal is not mounted as a second mask signal Constituted by and a mask processing unit that masks the alarm signal with a mask signal generated by the OR gate means.

[0017]

According to the alarm signal masking circuit having the above configuration,
The mask signal generating means generates the first mask signal after the hot-line removal of the panel, with a delay from the generation timing of the alarm signal due to the inversion detection processing time of the mounting state signal. on the other hand,
The mounting state signal is inverted from the mounting level to the non-mounting level earlier than the alarm signal generation timing. Therefore, this unmounted level is used as a second mask signal, and the OR operation of the first and second mask signals is performed to mask the alarm signal. Mask it.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIG. However, in FIG. 1, the same portions as those in FIG. 3 are denoted by the same reference numerals, and different portions will be mainly described here.

FIG. 1 shows the configuration of an alarm signal mask circuit according to the present invention. A mask signal output from a voltage monitoring circuit 3 is supplied to one input terminal of an OR (logical sum) circuit 9. Further, the mounting state signal is also supplied to the other input terminal of the OR circuit 9. This OR circuit 9 calculates and outputs the logical sum of both inputs. This OR output is inverted by the NOT circuit 5 and sent to the AND gate circuit 6, where it is subjected to mask processing.

The operation of the above configuration will be described below with reference to FIG.

First, in a panel mounted state, for example, FIG.
When the power is turned on as shown in FIG. 2A and the power supply voltage of the live line temporarily becomes unstable, an alarm signal is generated as shown in FIG.

However, at this time, the mounting state signal temporarily goes to a high level as shown by A in FIG. 2B, and the voltage monitoring circuit 3 detects this, and the signal B in FIG.
The mask signal is output for a predetermined time as shown in FIG. As a result, the alarm signal becomes AND, as shown by C in FIG.
The gate circuit 6 is turned off. This operation is the same immediately after the panel is inserted (mounted) into the live line.

On the other hand, when the panel is not mounted, since the mounting state signal is always at the high level, the mask signal is continuously output from the voltage monitoring circuit 3. Therefore, the alarm signal is not output when the panel is not executed.

Here, as described above, an alarm signal is also generated when the panel is removed from the live line. However, since this alarm signal is unnecessary, a mask process is required. However, in the voltage monitoring circuit 3, even if the panel is removed from the live line (becomes an unmounted state) and the mounting state signal switches from low to high as shown in D in FIG. The mask signal cannot be output only after the discharge of.

For this reason, the voltage monitoring circuit 3 outputs
(C) As shown in E in FIG.
The mask signal is output later than (e). Therefore, in this state, the AND gate circuit 6 outputs from FIG.
Unnecessary alarm signals are output temporarily as shown in middle G.

On the other hand, the mounting state signal becomes high level at the same time when the panel is removed from the live line. This level is the same level as the mask signal generated by the voltage monitoring circuit 3. Moreover, since the alarm signal is generated after the detection of the voltage fluctuation, the inversion timing of the mounting state signal is earlier than the generation timing of the alarm signal, as shown at D in FIG.

Therefore, the unmounted level is used as a mask signal. That is, when the mounting state signal becomes a high level which is an unmounted level as shown by D in FIG. 2B, this signal is sent to the OR circuit 9 as a mask signal. Since the OR circuit 9 performs a logical sum operation, the mask signal of the unmounted level is derived as it is regardless of the presence or absence of the mask signal from the voltage monitoring circuit 3.

The output of the logical sum operation at this time is inverted by the NOT circuit 5, and then becomes low level as shown by F in FIG. As a result, the mask signal arrives at the AND gate circuit 6 earlier than the alarm signal, and the alarm signal generated when the live line is removed from the panel G in FIG. 2F is completely masked.

Therefore, the alarm signal mask circuit having the above configuration utilizes the fact that the inversion operation of the mounting state signal at the time of removing the panel is earlier than the alarm signal generation timing. Since the mask processing is performed immediately regardless of the presence or absence of the mask signal from the voltage monitoring circuit 3 as the mask signal, the alarm signal when the panel is removed can be reliably masked.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0031]

As described above, according to the present invention, it is possible to provide an alarm signal masking circuit which can completely mask an alarm signal generated when a panel is removed from a live line.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an alarm signal mask circuit according to one embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the embodiment.

FIG. 3 is a block diagram showing a configuration of a conventional alarm signal mask circuit.

FIG. 4 is a timing chart for explaining the operation of the mask circuit of FIG. 3 and its problems.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mounting state signal input terminal 2 pull-up resistor 3 voltage monitoring circuit 4 capacitor 5 NOT circuit 6 AND gate circuit 7 alarm signal input terminal 8 alarm signal output terminal 9 OR circuit

Claims (2)

(57) [Claims] 1. A panel mounting device which is used for an alarm signal generating device which generates an alarm signal for a certain period when a power supply voltage of a live line into which a panel is inserted and removed becomes unstable, and which is obtained by monitoring a power supply voltage of the panel. An alarm signal mask circuit for masking the alarm signal when power is turned on, when the panel is hot-plugged, when the panel is removed, and when the panel is not mounted, based on a mounting state signal indicating / not mounted, Mask signal generating means for generating a first mask signal for a certain period of time from the time of detection when the level is not mounted and when the level is inverted to the level indicating mounting, and when the mounted state signal is not mounted. OR gate means for taking the level of the second mask signal as a second mask signal and taking the logical sum of the first and second mask signals; Mask processing means for masking the alarm signal with a mask signal. A first mask signal generated by the mask signal generating means is at a high level; a second mask signal at a level indicating that the mounting state signal is not mounted is at a high level; The processing means includes an inverting circuit for inverting the OR output of the OR gate means, and an AND gate circuit for deriving an alarm signal when the output of the inverting circuit is at a high level and shutting off when the output is at a low level. 2. The alarm signal mask circuit according to claim 1, wherein: