JPH10322932A - Power supply voltage monitoring circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor the feeding condition of AC voltage in real time by outputting an alarm signal, if the voltage value which is detected by a voltage detection means is a prescribed value or lower. SOLUTION: This power supply voltage monitoring circuit is formed such that a voltage detection circuit 40 is connected to the previous stage of a rectification circuit 20, to detect the voltage value of AC voltage before rectification is conducted at the rectifying circuit 20. If the supply of the AC voltage to an AC input terminal 10 is stopped due to the generation of a trouble, power supply output voltage is continuously outputted from an power supply output terminal 30 for a while thereafter, by electric charges which are stored in a smoothing capacitor 23 in the power supply voltage monitoring circuit. If the supply of the AC voltage to the AC input terminal 10 is stopped, the apply of the AC voltage to diodes 41, 42 is stopped immediately after that. Therefore, a voltage value detected at a voltage detection part 44 becomes a prescribed value or lower, and an alarm signal is outputted from an AC interrupt alarm 45. As a result of this, it is possible to monitor the feeding condition of the AC voltage in real time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply voltage monitoring circuit used in a power supply device or the like that operates by supplying an AC voltage and monitors a supply state of the AC voltage.

[0002]

2. Description of the Related Art Conventionally, as a power supply voltage monitoring circuit, for example, the one shown in FIG. 3 is known. This power supply voltage monitoring circuit is an AC power supply that receives an AC voltage from a power supply source.
An input terminal 10, a rectifier circuit 20 for rectifying an AC voltage supplied to the AC input terminal 10 and converting the AC voltage to a DC voltage;
It comprises a power supply output terminal 30 for outputting the DC voltage converted by the rectifier circuit 20, and a voltage detection circuit 50 for monitoring the power supply state to the AC input terminal 10.

The rectifier circuit 20 rectifies an AC voltage supplied to the AC input terminal 10 into a pulsating voltage, and smoothes the pulsating voltage generated by the rectifier 21. And a smoothing circuit 22 for setting a constant DC voltage. The smoothing circuit 22 includes a smoothing capacitor 23 for smoothing the pulsating voltage.

In the power supply voltage monitoring circuit having such a configuration, the voltage detection circuit 50 constantly detects the voltage value of the smoothing capacitor 23, and when the detection result becomes equal to or less than a predetermined value, AC voltage is detected. Input terminal 1
It is determined that the supply of the AC voltage to 0 has stopped, and an alarm signal indicating that fact is output. That is, in the conventional power supply voltage monitoring circuit, the state of power supply to the AC input terminal 10 is monitored by the voltage detection circuit 50 monitoring the voltage value at the smoothing capacitor 23 after rectifying the AC voltage. .

[0005]

However, in the above-described conventional power supply voltage monitoring circuit, since the voltage detection circuit 50 monitors the voltage value of the smoothing capacitor 23, the AC voltage applied to the AC input terminal 10 is changed. This cannot be detected immediately, even if the supply of is lost. this is,
This is because, in a normal state, since the smoothing capacitor 23 stores the electric charge, a time lag occurs after the supply of the AC voltage is stopped until the voltage of the smoothing capacitor 23 becomes equal to or lower than a predetermined value.

Further, the time lag varies depending on conditions such as the voltage value of the supplied AC voltage, the type (capacity, etc.) of the smoothing capacitor 23, the ambient temperature, the voltage value of the converted DC voltage, and the like. Therefore, it is very difficult to predict a time lag in advance or to compensate for the detection delay by processing control that allows for the time lag.

Further, in the conventional power supply voltage monitoring circuit, when the voltage detection circuit 50 outputs the alarm signal, the DC voltage output from the power supply output terminal 30 also becomes lower than a specified value. Therefore, based on the alarm signal, even if, for example, the switching of the supply source of the DC voltage or the stop instruction of the power supply device connected to the power supply output terminal 30 is performed, the power supply device causes a temporary voltage drop. The adverse effects may occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power supply voltage monitoring circuit capable of immediately detecting the supply of an AC voltage even when the supply of the AC voltage is lost, and capable of monitoring the supply state of the AC voltage in real time. And

[0009]

According to the present invention, there is provided a power supply voltage monitoring circuit devised to achieve the above object, comprising: an input terminal to which an AC voltage is supplied from a power supply source; Rectifying means for rectifying the AC voltage, a voltage detecting means connected to a stage preceding the rectifying means, and detecting a voltage value of the AC voltage before rectification by the rectifying means is performed, and the voltage detecting means detects Alarm means for outputting an alarm signal when the voltage value becomes equal to or less than a predetermined value.

According to the power supply voltage monitoring circuit having the above configuration, if the AC voltage is correctly supplied to the input terminal, the detection result of the voltage value by the voltage detecting means becomes almost a desired value.
However, since the voltage detection means detects the voltage value of the AC voltage before the rectification is performed by the rectification means, if the AC voltage is not correctly supplied to the input terminal, the detection result of the voltage value immediately becomes the predetermined value. It is as follows. When the detection result of the voltage detecting means becomes equal to or less than a predetermined value, the warning means outputs a warning signal. That is, in this power supply voltage monitoring circuit, when the AC voltage is no longer supplied to the input terminal, the alarm unit immediately outputs an alarm signal.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A power supply voltage monitoring circuit according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a specific example of a power supply voltage monitoring circuit according to the present invention, and FIG. 2 is a block diagram showing an outline of the power supply voltage monitoring circuit. In FIGS. 1 and 2, the same reference numerals are given to the same components as those of the related art (see FIG. 3).

Before describing a specific example of the power supply voltage monitoring circuit of the present invention, an outline of the power supply voltage monitoring circuit will be described. As shown in FIG. 2, the power supply voltage monitoring circuit of the present invention includes an AC input terminal 10, a rectifier circuit 20, a power supply output terminal 30, and a voltage detection circuit 40, similarly to the conventional one. Is what it is.

However, in this power supply voltage monitoring circuit, unlike the conventional one, a voltage detection circuit 40 is connected to a stage preceding the rectification circuit 20, and the voltage of the AC voltage before the rectification in the rectification circuit 20 is performed. The value is detected.
Thus, in this power supply voltage monitoring circuit, when the AC voltage is not correctly supplied to the AC input terminal 10, the detection result of the voltage detection circuit 40 immediately becomes equal to or less than a predetermined value.
When the detection result becomes a predetermined value or less, the voltage detection circuit 4
0 outputs an alarm signal indicating that.

That is, in this power supply voltage monitoring circuit,
When the AC voltage is no longer supplied to the input terminal 10, an alarm signal is immediately output from the voltage detection circuit 40. As a result, the power supply state of the AC voltage can be monitored in real time.

Next, a specific example of the configuration of the power supply voltage monitoring circuit of the present invention will be described with reference to FIG. In this power supply voltage monitoring circuit, an AC input terminal 10, a rectifier circuit 2
0, a power supply output terminal 30, and a voltage detection circuit 40, a filter 11, a converter circuit 31, a battery 32, and a battery switching circuit 33 are provided.

In the power supply voltage monitoring circuit having such a configuration, the AC input terminal 10 is connected to the input terminal of the filter 11. The filter 11 passes or blocks a specific frequency component of the AC voltage from the AC input terminal 10. The filter 11 has two output terminals, one of which is connected to the input terminal of the bridge diode 21 functioning as a rectifier, and the other to the other input terminal of the bridge diode 21.

The output terminal of the bridge diode 21 is connected to the positive terminal of a smoothing capacitor 23 constituting a smoothing circuit and the input positive terminal of a converter circuit 31. The output negative terminal of the bridge diode 21 is connected to the negative terminal of the smoothing capacitor 23 and the input negative terminal of the converter circuit 31.

The converter circuit 31 includes a smoothing capacitor 2
3 for performing DC / AC conversion, conversion of a power supply frequency, the number of phases, etc., on the DC voltage after the smoothing is performed by 3, and whose output terminal is connected to the power supply output terminal 30. It is.

In this power supply voltage monitoring circuit, the voltage detection circuit 40 includes diodes 41 and 42, a capacitor 43, a voltage detection unit 44, and an AC disconnection alarm unit 45.

Each of the diodes 41 and 42 is a two-terminal element having a rectifying function, and has its anode terminal connected between the output terminal of the filter 11 and the input terminal of the bridge diode 21. As a result, the voltage supplied to the AC input terminal 10 is applied to the anode terminals of the diodes 41 and 42. In addition, these diodes 4
The cathode terminals of the capacitors 43
Is connected to the output minus terminal of the bridge diode 21 via the. However, the cathode terminals of the diodes 41 and 42 are also connected to the voltage detection unit 44.

The voltage detector 44 includes diodes 41 and 42.
And the negative terminal of the bridge diode 21 to detect the value of the voltage applied to the diodes 41 and 42. The output terminal of the voltage detection unit 44 is connected to the AC disconnection alarm unit 45.

When the voltage detector 44 detects the voltage value of the voltage applied to the diodes 41 and 42, the AC disconnection alarm unit 45 compares the detection result with a predetermined value (threshold). , When the detection result is below a predetermined value,
It outputs an alarm signal. This alarm signal is output to the battery switching circuit 33. However, the alarm signal may be output to a host device that manages the power supply voltage monitoring circuit.

As described above, the diodes 41 and 42, the capacitor 43, the voltage detector 44, and the AC disconnection alarm 45
Is connected before the bridge diode 21, that is, between the filter 11 and the bridge diode 21, and detects the voltage value of the AC voltage before the rectification is performed by the rectifier circuit 20. It is designed to detect.

The battery 32 and the battery switching circuit 33 provided in the power supply voltage monitoring circuit are for realizing a so-called battery backup function. The battery 32 is composed of a primary battery or a secondary battery that stores a DC voltage in advance. The DC voltage stored by the battery 32 has the same rating as the DC voltage converted by the rectifier circuit 20. The battery switching circuit 33 includes the converter circuit 31 and the battery 3
2, connected to the AC disconnection alarm unit 45,
Based on the alarm signal from the disconnection alarm unit 45, the battery 32
Switches whether or not to supply the stored DC voltage to the converter circuit 31.

Next, in the power supply voltage monitoring circuit configured as described above, an example of operation when an AC voltage is supplied to the AC input terminal 10 and when no AC voltage is supplied will be described.

In this power supply voltage monitoring circuit, a specified voltage value (for example, AC 100
When the AC voltage of V) is supplied, the AC voltage passes through the filter 11, is rectified by the bridge diode 21, and is smoothed to a substantially DC voltage by the smoothing capacitor 23. Then, the DC voltage after the smoothing is applied to a converter circuit 31 and then supplied from a power supply output terminal 30 to a power supply output voltage (for example, DC5V or DC12).
V).

At this time, the AC voltage supplied to the AC input terminal 10 is applied to the diodes 41 and 42 of the voltage detection circuit 40. When an AC voltage is applied to the diodes 41 and 42, the AC voltage is applied to the diodes 41 and 4.
After being rectified by 2 and smoothed by the capacitor 43,
The voltage is input to the voltage detector 44. That is, the voltage detector 44
Then, the voltage value of the AC voltage applied to the diodes 41 and 42 is detected. Therefore, if an AC voltage is correctly supplied to the AC input terminal 10, the detection result of the voltage value by the voltage detection unit 44 becomes a desired value (specified value).
No alarm signal is output from the AC disconnection alarm unit 45.

On the other hand, if the AC voltage is not supplied to the AC input terminal 10 due to, for example, a trouble at the power supply source, the power supply voltage monitoring circuit sets the smoothing capacitor 2
Due to the electric charge stored in 3, the power supply output voltage continues to be output from the power supply output terminal 30 for a while. However, when the supply of the AC voltage to the AC input terminal 10 is stopped, the AC voltage is not applied to the diodes 41 and 42 immediately thereafter. Therefore, the voltage detection unit 44
Is a predetermined value (for example, a specified value of 20).
% Reduction value) or less, and an alarm signal is output from the AC interruption alarm unit 45.

That is, in this power supply voltage monitoring circuit,
When the AC voltage is no longer supplied to the input terminal 10, an alarm signal is immediately output from the AC disconnection alarm unit 45, and as a result, the power supply state of the AC voltage can be monitored in real time.

When an alarm signal is output from the AC interruption alarm section 45, the battery switching circuit 33 outputs the output from the power output terminal 30 to the rectifier circuit 20 based on the alarm signal.
Not the DC voltage after the smoothing was performed, but the battery 3
2 is switched to be performed by the stored DC voltage. As a result, even if power supply to the AC input terminal 10 is stopped, power supply from the battery 32 is performed immediately thereafter. In addition, the electric charge in the smoothing capacitor 23 is output for a while after the power supply is stopped. Therefore, in this power supply voltage monitoring circuit, the power supply output voltage from the power supply output terminal 30 does not drop even if the power supply to the AC input terminal 10 is stopped.

As described above, in this power supply voltage monitoring circuit, the diodes 41 and 42 and the capacitor 43 are connected in front of the bridge diode 21, and the voltage detector 44 detects the voltage value of the voltage applied to the diodes 41 and 42. Is detected, and when the detection result of the voltage detection unit 44 becomes equal to or less than a predetermined value, the AC disconnection alarm unit 45 outputs an alarm signal. As a result, even if the power supply to the AC input terminal 10 is lost, it is possible to detect the power supply immediately, and the power supply state of the AC voltage can be monitored in real time.

Therefore, when the power supply state is monitored by the power supply voltage monitoring circuit, control such as a stop instruction of the power supply target device connected to the power supply output terminal 30 is performed based on the alarm signal from the AC disconnection alarm unit 45. Even in such a case, there is no need to consider a time lag or the like due to the charge stored in the smoothing capacitor 23, and there is no adverse effect of the temporary voltage drop on the power-supplied device.

Further, in this power supply voltage monitoring circuit,
When there is an alarm signal from the disconnection alarm unit 45, power is supplied from the battery 32 immediately after the switching by the battery switching circuit 33. Thereby, even if the power supply to the AC input terminal 10 is lost,
A reliable battery backup function can be realized. Also,
By inputting an alarm signal from the AC disconnection alarm unit 45 to the battery switching circuit 33, it is possible to change the battery switching circuit 33, which is usually composed of a diode, to a semiconductor switch, thereby achieving a significant reduction in loss. Will be able to do it.

In the above-described embodiment, AC10
5V DC, 12V DC or D for 0V input
Although a power supply voltage monitoring circuit suitable for use in a power supply device or the like that outputs C24V or the like has been described, the present invention is not limited to this. For example, any other device that operates by supplying AC voltage can be applied. Specifically, it may output an AC voltage instead of the DC voltage as described above. Further, a motor, a heater, or the like is provided as an output unit, and the DC voltage is not directly output from the terminal, but is converted into another energy and output.

[0035]

As described above, in the power supply voltage monitoring circuit of the present invention, the voltage detecting means detects the voltage value of the AC voltage before the rectification is performed in the rectifier circuit, and the voltage value is set to the predetermined value. When the following occurs, the alarm means immediately outputs an alarm signal. Therefore, when the AC voltage is no longer supplied to the input terminal, the fact can be immediately recognized, and as a result, the power supply state of the AC voltage can be monitored in real time.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a detailed configuration of an example of an embodiment of a power supply voltage monitoring circuit according to the present invention.

FIG. 2 is a block diagram illustrating an outline of an example of a power supply voltage monitoring circuit according to the present invention.

FIG. 3 is a block diagram illustrating an outline of an example of a conventional power supply voltage monitoring circuit.

DESCRIPTION OF SYMBOLS 10 AC input terminal 20 Rectifier circuit 21 Bridge diode (rectifier) 23 Smoothing capacitor 30 Power output terminal 32 Battery 33 Battery switching circuit 40 Voltage detection circuit 41, 42 Diode 43 Capacitor 44 Voltage detection unit 45 AC disconnection alarm unit

Claims (2)

[Claims] 1. An input terminal to which an AC voltage is supplied from a power supply source, a rectifier for rectifying the AC voltage supplied to the input terminal, and a rectifier connected to a preceding stage of the rectifier and rectifying by the rectifier. Voltage detection means for detecting the voltage value of the AC voltage before the voltage detection is performed, and an alarm means for outputting an alarm signal when the voltage value detected by the voltage detection means becomes a predetermined value or less. Power supply voltage monitoring circuit. 2. An output unit for outputting a power supply voltage after rectification by the rectification unit, a power storage unit for storing a DC voltage in advance, and an output of an alarm signal by the alarm unit. 2. The power supply voltage monitoring circuit according to claim 1, further comprising: switching means for outputting the DC voltage in the power storage means to the output means instead of the power supply voltage.