JP2001313484A - Alarm signal output circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To output surely an alarm signal with a small number of components without using an IC of exclusive use when a load stops. SOLUTION: When a fan motor 2 stops and an output signal stops at an L level or an H level, the impedance of a capacitor 5 becomes high, and a capacitor 8 is not charged. In this state, the capacitor 8 discharges, a voltage between terminals of the capacitor 8 decreases, the ON-state and the OFF-state of a MOS type FET 12 are changed over, and the alarm signal is outputted. As a result, the alarm signal can be surely outputted when the fan motor 2 stops. This operation can be realized by using only two capacitors 5, 8 and one resistor 9, so that the IC of exclusive use in the conventional device is made unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an alarm signal output circuit that outputs an alarm signal when the signal becomes either (low) or H (high).

[0002]

Generally, in the case of an electric product such as a power supply device having a built-in heat-generating component which requires cooling by a fan motor, if the fan motor stops for some reason, it is immediately sent to the outside. An alarm signal output circuit is provided to transmit an alarm signal (for example, the alarm signal is switched to L level during normal operation and to H level during abnormal operation).

FIG. 4 is a circuit diagram of a conventional alarm signal output circuit connected to a load. In the figure, reference numeral 51 denotes an input terminal to which an output signal of a fan motor 52 serving as a load is applied. The input terminal 51 has an L level (ground level) which is a first level when the fan motor 52 operates normally.
A square-wave pulse-like output signal is applied by repeating the H level (predetermined voltage level) as the second level. The input terminal 51 is connected to the cathode of a diode 53, while the anode of the diode 53 is connected to the input terminal of a dedicated IC. Also diode
The connection point between the anode of 53 and the input terminal of IC 54 is a resistor 55
To the operating voltage VCC line. Thus, when the output signal of the fan motor 52 becomes L level, the diode 53 becomes conductive and the input terminal of the IC 54 also becomes L level. Conversely, when the output signal of the fan motor 52 becomes H level, the diode 53 becomes non-conductive. As a result, the operating voltage VCC is supplied to the input terminal of the IC 54.

The IC 54 includes a resistor 56 and a capacitor.
A time constant circuit comprising a resistor 57 and a capacitor 59 is provided. In addition, a resistor 60 is connected to the IC 54. When a pulse-like output signal is repeatedly supplied from the fan motor 52 to the input terminal 51, the IC 54 outputs an alarm output terminal (ALM output) 61.
The alarm signal output to the
52 stops and its output signal goes low or high for a certain period of time.
When the level reaches the level, the alarm signal output to the alarm output terminal 61 is set to the H level. This allows the fan motor 52
Alarm was output to the outside of the abnormal stop.

In the above configuration, the output signal when the fan motor 52 stops is not always at either the L level or the H level.
To reliably detect the stop state of the 52, the L level or the H level
A dedicated IC 54 for outputting a predetermined alarm signal when the level state continues for a certain period of time has to be used.
However, such a dedicated IC 54 is expensive, and it has been desired to realize it with a small number of inexpensive components.

Accordingly, the present invention solves the above problems,
An object of the present invention is to provide an alarm signal output circuit that can reliably output an alarm signal when a load is stopped with a small number of components without using a dedicated IC.

[0007]

In order to achieve the above object, an alarm signal output circuit according to the present invention repeatedly supplies an output signal of a first level or a second level during operation and stops the operation. Sometimes the output signal of the load is applied to an alarm signal output circuit that is connected to a load whose output signal stops at either the first level or the second level and outputs an alarm signal when the load stops. A first capacitor having one end connected to an input terminal of the first capacitor, a charge / discharge circuit including a second capacitor and a resistor connected to the other end of the first capacitor, and a voltage between terminals of the charge / discharge circuit. A switch element for turning on and off, and when the load operates, charges are stored in the second capacitor via the first capacitor, and the charge and discharge circuit is connected between terminals of the charge / discharge circuit. While the pressure is kept constant, when the load is stopped, the application of the output signal is cut off by the first capacitor, the second capacitor is discharged by the resistor, and the on / off of the switch element is turned on / off. It is configured to switch and output an alarm signal.

In this case, during the operation of the load, when an output signal of the first level or the second level is repeatedly supplied from the load as if it were an AC waveform,
The impedance of the first capacitor decreases, and the second capacitor constituting the charge / discharge circuit passes through the first capacitor.
In this capacitor, more electric charge is stored than the amount discharged from the resistor. Therefore, the voltage between the terminals of the second capacitor and thus the charge / discharge circuit is kept constant, and the switch element stops outputting the alarm signal.

On the other hand, when the load stops, the output signal becomes the first level or the second level as if it were DC.
, The impedance of the first capacitor increases, and the second capacitor is no longer charged. When this happens, the electric charge stored in the second capacitor moves to the resistor and is discharged, and the voltage between the terminals of the second capacitor and thus the charging / discharging circuit is reduced. Is output.

As described above, even if the output signal stops at either the first level or the second level, the application from the input terminal is cut off by the first capacitor, so that the alarm signal is reliably output when the load stops. Can be output. In addition, since this can be realized with only two capacitors and one resistor, a dedicated IC as in the related art becomes unnecessary.

According to a second aspect of the present invention, in addition to the first aspect, the switch element is a MOS FET.

When a MOS-type FET is used, its input impedance is much higher than that of other switch elements. Therefore, the second capacitor does not need to consider the discharge of the MOS-type FET. Therefore, it is possible to reduce the capacity of the second capacitor and thus the size of the second capacitor.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an alarm signal output circuit according to the present invention will be described below with reference to the accompanying drawings. In FIG. 1 showing a circuit configuration, reference numeral 1 denotes an input terminal to which an output signal of a fan motor 2 as a load is applied.
And an H level, which is a second level, is applied to output a square pulse output signal. The input terminal 1 is connected to the cathode of a diode 3 while the anode of the diode 3 is connected to an operating voltage VCC.
A resistor 4 is connected between the line. As a result, when the output signal of the fan motor 2 goes low, the diode 3 conducts, the potential at the node A between the diode 3 and the resistor 4 goes low, and conversely, the output signal of the fan motor 52 goes high.
At this level, the diode 3 becomes non-conductive, the operating voltage VCC is supplied to the connection point A, and the potential thereof becomes H level. In other words, this series circuit of the diode 3 and the resistor 4 supplies the operating voltage VCC to the connection point A when the signal output of the fan motor 2 is at the H level, and particularly when the current of the output signal of the fan motor 2 is small. It is effective for

A series circuit of a capacitor 5 as a first capacitor and a resistor 6 is connected between the connection point A and the ground line. The connection point A is connected to one end of the capacitor 5, and the potential of the connection point B between the capacitor 5 and the resistor 6 changes as the potential of the connection point A is repeated at L level-H level. Is repeatedly shifted by a voltage Vc between both ends of the capacitor 5 below the potential at the connection point A. However, if the potential of the connection point A remains at the L level or the H level, the charge of the capacitor 5 stops moving and the impedance increases, so that the connection point A and the connection point B are separated from each other. The potential at the point B becomes zero (ground level). That is, when the output signal of the fan motor 2 is repeatedly output at L level-H level, the series circuit of the capacitor 5 and the resistor 6 outputs a positive or negative potential across the ground, that is, an AC-like waveform. When the output side of the fan motor 2 is shifted to either the L level or the H level by shifting the side (connection point B), it corresponds to a voltage shift circuit for setting the output side to the ground level potential.

A half-wave rectifying / smoothing circuit comprising a series circuit of a diode 7 and a capacitor 8 as a second capacitor is connected between the connection point B and the ground line. Also,
A discharging resistor 9 is connected between both ends of the capacitor 8,
The capacitor 8 and the resistor 9 constitute a charge / discharge circuit 10. Specifically, when the potential at the connection point B is on the plus side, the diode 7 conducts and the capacitor 8 stores electric charge. Conversely, when the potential at the connection point B is zero or on the negative side, the diode 7 is turned off, and the electric charge stored in the capacitor 8 is released from the resistor 9 as energy. At this time, while the output signal of the fan motor 2 is repeatedly output at L level-H level, and while the potential of the connection point B repeats the plus side and the minus side, the connection point C between the cathode of the diode 7 and the capacitor 8 Is stored in the capacitor 8 via the diode 7 so that the potential of the capacitor 8 is maintained at a substantially constant level. On the other hand, when the output signal of the fan motor 2 is L level or H level.
When the potential stops at any of the levels and the potential at the node B becomes zero, the diode 7 remains non-conductive, the capacitor 8 discharges through the resistor 9, and the potential at the node C eventually becomes zero. .

The connection point C is connected via a resistor 11 to the gate of a MOSFET 12 which is a switch element. The source of the MOS FET 12 is grounded, an alarm output terminal (ALM output) 13 is connected to the drain thereof, and a resistor 14 is connected between the drain of the MOS FET 12 and the operating voltage VCC line. When the voltage at the node C is equal to or higher than a predetermined voltage level, the MOS FET 12 is turned on and the alarm output terminal 13 is at the L level.
The ET 12 is turned off, and the operating voltage VCC is output from the alarm output terminal 13 via the resistor 14 as an alarm signal. The switch element is a MOS type FE
Various elements other than T12 may be used, and a configuration in which an alarm signal of L level is logically output from the alarm output terminal 13 may be employed.

Next, the operation of the above configuration will be described with reference to the waveform diagrams of FIGS. FIG. 2 shows the state of the fan motor 2 when the fan motor 2 is stopped.
3 shows the waveform of each part when the output signal of the fan motor 2 stops at the H level. FIG. 3 shows the waveform of each part when the output signal of the fan motor 2 stops at the L level when the fan motor 2 stops. It shows. In each of these figures, the output signal of the fan motor 2 at the input terminal 1 and the respective voltage waveforms at the connection points B and C and the alarm output terminal 13 are shown from the top.

During normal operation of the fan motor 2, an output signal in the form of a square wave pulse by repetition of the L level and the H level is applied to the input terminal 1 as described above. At this time,
When the output signal of the fan motor 2 becomes L level, the diode 3 becomes conductive and the potential at the connection point A becomes L level. Conversely, when the output signal of the fan motor 2 becomes H level, the diode 3 becomes non-conductive. Thus, the operating voltage VCC is supplied to the connection point A, and the potential of the operating voltage VCC becomes H level. The capacitor 5 repeats charging and discharging as the potential of the connection point A repeats to the L level and the H level, so that the potential of the connection point B is higher than the potential of the connection point A by the voltage between both ends of the capacitor 5. Shift downward by Vc. Thereby, the connection point B becomes
Positive or negative potential is repeated across the ground.

The diode 7 and the capacitor 8 forming the rectifying / smoothing circuit convert the AC waveform at the connection point B into
Rectified and smoothed to DC at connection point C. Each time the potential at the connection point B becomes positive, the diode 7 conducts and the capacitor 8
Is stored in the connection point C due to the discharge of the resistor 9.
, And the connection point C is kept at a substantially constant potential. Therefore, the MOS FET 12 having the gate and the source connected between both ends of the capacitor 8 is turned on, and the potential of the alarm output terminal 13 is always at the L level.

Here, when the fan motor 2 stops for some reason and the output signal of the fan motor 2 remains at the H level as shown in FIG. 2, the potential at the connection point A also remains at the H level. The impedance of the capacitor 5 that has been repeatedly charged and discharged increases. And connection point A
The connection between the node and the connection point B is cut off by the capacitor 5, the connection point B becomes zero, that is, the ground level, and the diode 7 is turned off. In this case, the charging of the capacitor 8 is stopped, and the electric charge stored in the capacitor 8 moves to the resistor 9 and is discharged, and the voltage between the terminals of the capacitor 8, that is, the potential of the connection point C decreases. Therefore, when the gate voltage of the MOSFET 12 drops to a certain level, the MOSFET 12 is switched from ON to OFF, and the operating voltage VCC is output from the alarm output terminal 13 via the resistor 14 as an H-level alarm signal. .

Conversely, when the output signal of the fan motor 2 remains at the H level as shown in FIG. 3, the potential at the connection point A remains at the L level, and charging and discharging are performed until then as in FIG. The repeated impedance of the capacitor 5 increases. The connection between the connection points A and B is cut off by the capacitor 5, the connection point B becomes zero, that is, the ground level, and the diode 7 is turned off. In this case, the charging of the capacitor 8 is stopped, and the electric charge stored in the capacitor 8 moves to the resistor 9 and is discharged, and the voltage between the terminals of the capacitor 8, that is, the potential of the connection point C decreases. Therefore, MOS type F
When the gate voltage of ET12 drops to a certain level, M
The OS-type FET 12 is switched from on to off, and the operating voltage VCC is output from the alarm output terminal 13 via the resistor 14 as an H-level alarm signal.

As described above, according to the above embodiment, the output signal of the L level which is the first level or the H level which is the second level is repeatedly supplied at the time of operation, and the L level or the H level at the time of stoppage. In an alarm signal output circuit which is connected to the fan motor 2 as a load at which the output signal stops and outputs an alarm signal when the fan motor 2 stops, one end is connected to the input terminal 1 to which the output signal of the fan motor 2 is applied. , A charging / discharging circuit 10 comprising a parallel circuit of a capacitor 8 as a second capacitor and a resistor 9 connected to the other end of the capacitor 5, and a terminal of the charging / discharging circuit 10. A MOS type FET 12 is provided as a switch element which is turned on / off according to a voltage between the nodes (connection point C). While the electric charge is stored in the capacitor 8 via the capacitor 5 and the voltage between the terminals of the charge / discharge circuit 10 is kept constant, the application of the output signal of the fan motor 2 is cut off by the capacitor 5 when the fan motor 2 is stopped. Then, the capacitor 8 is discharged by the resistor 9, and the ON / OFF of the MOS FET 12 is switched to output an alarm signal.

In this case, during the operation of the fan motor 2, when an L level or H level output signal is repeatedly supplied from the fan motor 2 as if it were an AC waveform, the impedance of the capacitor 5 becomes low, and 5, more charge is stored in the capacitor 8 of the charge / discharge circuit 10 than is discharged by the resistor 9. Therefore, the voltage between the terminals of the capacitor 8 and the charge / discharge circuit 10 is kept constant, and the MOS FET 12
Stops the output of the alarm signal.

On the other hand, when the fan motor 2 stops, the output signal becomes L level or H level as if it were DC.
When the level remains at the level, the impedance of the capacitor 5 is increased, and the capacitor 8 is not charged. In this case, the charge stored in the capacitor 8 moves to the resistor 9 and is discharged, and the voltage between the terminals of the capacitor 8 and the charge / discharge circuit 10 is reduced. Is output.

As described above, the output signal is at L level or H level.
In any of the levels, the application of the output signal from the input terminal 1 is interrupted by the capacitor 5, so that the alarm signal can be output reliably when the fan motor 2 stops. And this is two capacitors 5, 8
And a single resistor 9 alone, it is not necessary to use a conventional dedicated IC.

In this case, it is preferable to use the MOS FET 12 as the switch element as in this embodiment. MOS
When the type FET 12 is used, the input impedance of the type FET 12 is much higher than that of other switch elements. Therefore, it is possible to reduce the capacity of the capacitor 8 and hence the size.

In this embodiment, the fan motor 2 is used as a load. However, the output signal of the first level or the second level is repeatedly supplied during operation, and the first level or the second level is output during stoppage. The invention is applicable to any load where the output signal stops at any of the levels. Further, the first level in the embodiment is the ground level, but may be a minus level or a plus level.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention.

[0029]

The alarm signal output circuit according to the first aspect of the present invention repeatedly supplies an output signal of the first level or the second level during operation, and outputs the first level or the second level when stopped. An alarm signal output circuit for outputting an alarm signal when the load is stopped, the first capacitor having one end connected to an input terminal to which the output signal of the load is applied; A charge / discharge circuit including a second capacitor and a resistor connected to the other end of the first capacitor; and a switch element that is turned on / off according to a voltage between terminals of the charge / discharge circuit. During the operation, the charge is stored in the second capacitor via the first capacitor, the voltage between the terminals of the charge / discharge circuit is kept constant, and the load is stopped. Is configured to cut off the application of the output signal by the first capacitor, discharge the second capacitor by the resistor, switch on / off the switch element, and output an alarm signal. Thus, an alarm signal can be reliably output when the load is stopped with a small number of parts without using a dedicated IC.

According to a second aspect of the present invention, there is provided an alarm signal output circuit according to the first aspect, wherein the switch element is a MOS FET, and in this case, a second capacitor is further provided. It is possible to reduce the capacity and thus the size.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an alarm signal output circuit showing one embodiment of the present invention.

FIG. 2 is a waveform diagram showing waveforms of respective parts when the output signal of the fan motor stops at an H level when the fan motor stops.

FIG. 3 is a waveform diagram showing waveforms of respective units when the output signal of the fan motor stops at an L level when the fan motor stops.

FIG. 4 is a circuit diagram of an alarm signal output circuit showing a conventional example.

[Explanation of symbols]

 Reference Signs List 1 input terminal 2 load (fan motor) 5 capacitor (first capacitor) 8 capacitor (second capacitor) 9 resistor 10 charge / discharge circuit 12 MOS type FET (switch element)

Claims (2)

[Claims] A first level or a second level output signal that is repeatedly supplied during operation;
And an alarm signal output circuit that outputs an alarm signal when the load is stopped, wherein the input signal is applied to an input terminal to which the output signal of the load is applied. A first capacitor having one end connected thereto, a charge / discharge circuit including a second capacitor and a resistor connected to the other end of the first capacitor, and turned on / off according to a voltage between terminals of the charge / discharge circuit. A switch element for storing a charge in the second capacitor via the first capacitor during the operation of the load, keeping a voltage between terminals of the charge / discharge circuit constant, and stopping the load. Sometimes, the application of the output signal is cut off by the first capacitor, the second capacitor is discharged by the resistor, and the on / off of the switch element is turned off. Ete, alarm signal output circuit, characterized by being configured to output an alarm signal. 2. The alarm signal output circuit according to claim 1, wherein said switch element is a MOS FET.