JP6868708B2 - Power supply monitoring device - Google Patents

Description

In the present invention, the external power supply is normally applied to the isolated power supply circuit from the secondary side of the insulated power supply circuit that inputs an external power supply different from the main power supply and outputs the secondary side power supply isolated from the external power supply. It relates to a power supply monitoring device that monitors whether or not it is installed.

In FA (Factory Automation) devices such as programmable logic controllers (hereinafter referred to as PLCs) and measuring devices, input / output is performed with various external devices. In this case, the interface with the external device is insulated for the purpose of preventing noise, preventing mutual interference between devices, and protecting the device.

Further, the FA device is required to diagnose whether or not the power supply is normally performed, stop the device and notify the user according to the diagnosis result.

Further, in order to improve reliability, it is important to monitor the insulated power supply circuit so that a state in which the power supply is unstable or a state in which the voltage is excessive or insufficient does not occur. When these conditions occur, the secondary of the insulated power supply circuit is used to prevent damage to the switching transformer, semiconductor element, etc., and to prevent the output voltage from chattering or dropping when the load suddenly changes. It is necessary to stop the load connected to the side.

Furthermore, in FA equipment, it is necessary to reduce the number of parts with a limited life and heat sources.

Consider a case where the external power supply input to the isolated power supply circuit to generate an insulated secondary power supply is monitored whether or not it is normally applied, and a power supply signal is output as a signal indicating the monitoring result. .. In this case, a method of insulating the power supply signal by using a photocoupler between the primary and secondary is generally used.

For example, a voltage monitoring circuit is provided on the primary side of the isolated power supply circuit, and a power supply signal output as a monitoring result from the voltage monitoring circuit is transmitted to the secondary side by a photocoupler.

Further, there is a conventional technique of monitoring the voltage across a rectifier diode on the insulated secondary side to detect a power failure (see, for example, Patent Document 1).

In addition, the photocoupler connected from the primary side to the secondary side monitors the presence or absence of power supply to the isolated power supply circuit, and the transistor on the secondary side of the photocoupler conducts when the power is supplied, so that the power supply of the reset IC is supplied. There is a prior art in which the supply is started (see, for example, Patent Document 2). In Patent Document 2, in this way, when the power is normally supplied to the isolated power supply circuit, the AND process for starting the power supply to the reset IC is performed.

Jitsukaisho 60-44439 JP-A-2007-192690

However, the prior art has the following problems.
In the circuit of Patent Document 1, instead of having no signal to be transmitted between the primary and secondary isolated by the photocoupler, the voltage of the diode of the rectifier circuit is detected by the power failure detection circuit. Therefore, in this case, it is necessary to insulate between the rectifier circuit and the power failure detection circuit. That is, since the power failure detection circuit is provided, the number of second insulation points is increased.

Further, the voltage across the rectifier circuit is not smoothed by the smoothing circuit. Therefore, the voltage across the rectifier circuit contains a large ripple. Further, in general, a rectifying element such as a diode has a voltage drop of about 1 V. Therefore, since the signal to be detected is minute and the disturbance due to ripple is large, there is a problem that it is difficult to detect a power failure with high accuracy in the circuit of Patent Document 1.

On the other hand, in the circuit of Patent Document 2, the reset IC on the secondary side, which is conducted by the photocoupler, is operated. Therefore, if the voltage at which the photocoupler can be turned on is applied to the primary side of the photocoupler and the VCS is normal, the reset IC is released. Therefore, there is a problem that the reset IC is released even when an excessive voltage is applied to the primary side.

Further, in the circuit of Patent Document 2, in order to supply power to the reset IC and peripheral circuits from the transistor on the secondary side of the photocoupler and to stabilize the voltage of the Zener diode on the primary side, the circuit is on the primary side of the photocoupler. It is necessary to pass a large current. In this case, there is a problem that the heat generated by the photocoupler becomes large and the life of the photocoupler itself is shortened.

Further, in the above-mentioned conventional technique, since a photocoupler is used, there is a problem that it is not possible to reduce heat generating parts and life-long parts.

The present invention has been made to solve the above-mentioned problems, and uses a photocoupler or a rectifier circuit between the primary side and the secondary side in order to monitor the voltage from the secondary side to the primary side. The purpose is to obtain a power supply monitoring device that can monitor an isolated power supply circuit without any problems.

The power supply monitoring device according to the present invention is provided on the primary side of an insulated power supply circuit and an isolated power supply circuit that inputs an external power supply different from the main power supply and outputs a secondary power supply isolated from the external power supply. It monitors whether or not the external power supply is normally applied to the power supply circuit, and if the external power supply is not normally applied, it is determined that the external power supply is abnormal, and the secondary power supply is not output from the isolated power supply circuit. A switch circuit including a voltage monitoring circuit that controls the voltage and a switch that turns on when the secondary power supply is normally output and turns off when the secondary power supply is not output normally. , On the secondary side of the isolated power supply circuit, a series circuit provided by connecting a pull-up resistor and a switch circuit in series between the logic power supply generated based on the input of the main power supply and the ground. The voltage at the connection point between the pull-up resistor and the switch circuit is output to the outside as a power supply signal .

According to the present invention, in order to monitor the voltage from the secondary side to the primary side, it is possible to monitor the isolated power supply circuit without using a photocoupler or a rectifier circuit between the primary side and the secondary side. A power supply monitoring device can be obtained.

It is a figure which showed the whole structure including the power supply monitoring apparatus which concerns on Embodiment 1 of this invention. It is a figure which showed the whole structure which has the structure different from FIG. 1 including the power supply monitoring apparatus which concerns on Embodiment 1 of this invention. It is a configuration example of the switch circuit which concerns on Embodiment 2 of this invention, and is the figure which showed the case where the transistor was used as a switch. It is a configuration example of the switch circuit which concerns on Embodiment 3 of this invention, and is the figure which showed the case where MOS-FET was used as a switch. It is a configuration example of the switch circuit which concerns on Embodiment 4 of this invention, and is the figure which showed the case where the protection circuit was provided. It is a configuration example of the switch circuit which concerns on Embodiment 5 of this invention, and is the figure which showed the case where the voltage adjustment circuit was provided. FIG. 6 is a diagram showing an overall configuration when the power supply monitoring device according to the present invention is applied to a PLC in the sixth embodiment of the present invention.

An embodiment suitable for an insulated power supply circuit in the present invention will be described with reference to the above drawings.

Embodiment 1.
FIG. 1 is a diagram showing an overall configuration including a power supply monitoring device according to a first embodiment of the present invention. The main power supply circuit 1 generates a logic power supply 111 based on the main power supply input 110. On the other hand, the isolated power supply circuit 2 generates a secondary power supply isolated from the external power supply based on the external power supply input 101, and outputs the secondary power supply as the secondary output 102. Here, the external power supply corresponds to an auxiliary power supply supplied from the outside, unlike the main power supply used in the apparatus.

The voltage monitoring circuit 4 is provided on the primary side of the insulated power supply circuit 2, and monitors whether or not the external power supply input to the insulated power supply circuit 2 as the external power supply input 101 has a voltage having a normal range. .. Here, the voltage having a normal range corresponds to the range of the rated voltage assumed at the time of design. Then, the voltage monitoring circuit 4 prevents the secondary power supply from being output from the isolated power supply circuit 2 when a monitoring result is obtained that the external power supply is not normally applied to the insulated power supply circuit 2. Control.

In the example of FIG. 1, the insulated power supply circuit 2 has a configuration in which it is possible to switch between a start state in which the output of the secondary side power supply is output and a stop state in which the output of the secondary side power supply is stopped according to an external signal. There is. When having such a configuration, the voltage monitoring circuit 4 outputs an external signal for stopping the insulated power supply circuit 2 to the insulated power supply circuit 2, thereby secondary to the insulated power supply circuit 2. It can be controlled so that the side power supply is not output.

Further, FIG. 2 is a diagram showing an overall configuration having a configuration different from that of FIG. 1, including the power supply monitoring device according to the first embodiment of the present invention. In the example of FIG. 2, a second switch 6 is provided between the external power supply input 101 and the input terminal for inputting the external power supply in the isolated power supply circuit 2. When having such a configuration, the voltage monitoring circuit 4 switches the second switch 6 to the off state in order to put the isolated power supply circuit 2 in the stopped state, so that the secondary power supply is output from the insulated power supply circuit 2. It can be controlled so that it is not done.

On the secondary side of the insulated power supply circuit 2, a series circuit of a pull-up resistor 5 and a switch circuit 3 is provided between the logic power supply 111 and the ground. Further, the voltage at the connection point between the pull-up resistor 5 and the switch circuit 3 is output to the outside as a power supply signal 103.

The switch circuit 3 is turned on when the secondary power supply, which is the output of the isolated power supply circuit 2, is output to the secondary output 102 as a normal voltage range. On the other hand, the switch circuit 3 is turned off when the secondary power supply is not output to the secondary output 102 as a normal voltage range. Therefore, when the switch circuit 3 is in the ON state, a low-level signal having the same potential as the ground is output as the power supply signal 103.

In other words, in the switch circuit 3, the first condition in which the external power supply is applied to the isolated power supply circuit 2 as a normal rated voltage and the secondary power supply which is the output of the isolated power supply circuit 2 are from the insulated power supply circuit 2. When both the second condition that is normally output is satisfied, the ON state is set.

Therefore, by providing the circuit configuration of FIG. 1 or 2, it is possible to suppress the abnormal operation of the insulated power supply circuit 2 due to an external power supply abnormality due to the voltage excess or deficiency on the primary side, and the insulated power supply circuit 2 operates due to damage or the like. It is possible to construct an AND condition that prevents the power supply signal 103 from being turned on when the secondary side voltage is not normally output. As a result, the power supply signal 103 can be generated without using a lifetime component such as a photocoupler and a heat generating component.

In the examples of FIGS. 1 and 2, one end of the pull-up resistor 5 is connected to the logic power supply 111. However, the same effect can be obtained by adopting a configuration in which the pull-up resistor 5 is pulled up by another power source. Further, the circuit that generates the power supply signal 103 can also be configured by a circuit that combines the switch circuit 3 and the pull-down resistor.

Further, the switch circuit 3 may be configured to include an electronic switch, or may be configured to include a mechanical switch. The specific configuration of the switch circuit 3 will be described in detail in Embodiments 2 to 5 described later.

As described above, according to the first embodiment, both the condition that the rated voltage assumed at the time of design is applied to the primary side of the insulated power supply circuit and the condition that the insulated power supply circuit outputs the voltage are satisfied. Therefore, it has a configuration that can turn on the switch circuit. As a result, it is possible to realize a power supply monitoring device capable of monitoring the insulated power supply circuit without using a photocoupler or a rectifier circuit and outputting a power supply signal based on the monitoring result.

Embodiment 2.
In the second embodiment, a specific example in which the switch circuit 3 is configured by using the transistor will be described. FIG. 3 is a configuration example of the switch circuit 3 according to the second embodiment of the present invention, and is a diagram showing a case where a transistor is used as a switch.

The switch circuit 3 shown in FIG. 3 includes two resistors 31, a base resistor 32, a pull-down resistor 33, and a transistor 34. Specifically, the switch circuit 3 according to the second embodiment includes a transistor 34 used as an element of an electronic switch, two resistors 31 for dividing the voltage supplied from the secondary output 102, and a voltage dividing component. It is composed of a transistor 34 which is switched via a circuit including a base resistor 32 and a pull-down resistor 33 according to the generated voltage.

When the voltage of the secondary output 102 is divided by the resistor 31 and a voltage exceeding the VBE of the transistor 34 is applied, the transistor 34 is turned on and the power supply signal 103 becomes low level. On the other hand, when the transistor 34 is off, the power supply signal 103 becomes the logic power supply 111 due to the pull-up resistor 5, and becomes a high level. As a result, a high / low signal at the voltage level of the logic power supply 111 is output as the power supply signal 103 according to the voltage of the secondary side output 102.

The base resistor 32 and the pull-down resistor 33 shown in FIG. 3 are general configurations for stabilizing the operation of the transistor, and do not limit the configuration of the switch circuit 3 according to the second embodiment.

Embodiment 3.
In the third embodiment, a specific example in which the switch circuit 3 is configured by using the MOS-FET will be described. FIG. 4 is a configuration example of the switch circuit 3 according to the third embodiment of the present invention, and is a diagram showing a case where a MOS-FET is used as the switch.

The switch circuit 3 shown in FIG. 4 includes two resistors 31 and a MOS-FET 35. Specifically, the switch circuit 3 according to the third embodiment is divided into a MOS-FET 35 used as an element of an electronic switch and two resistors 31 for dividing the voltage supplied from the secondary output 102. It is composed of a MOS-FET 35 in which a compressed voltage is applied to the gate. Then, when the applied voltage exceeds the threshold value between the gate and the source of the MOS-FET 35, the MOS-FET 35 is turned on and the power supply signal 103 becomes low level.

On the other hand, when the MOS-FET 35 is off, the power supply signal 103 becomes the logic power supply 111 due to the pull-up resistor 5, and becomes a high level. As a result, a high / low signal at the voltage level of the logic power supply 111 is output as the power supply signal 103 according to the voltage of the secondary side output 102.

The threshold value between the gate and the source is a parameter preset according to the characteristics of the MOS-FET 35. Therefore, by selecting the MOS-FET 35 having a desired threshold value, it is possible to design the switch circuit 3 that performs an appropriate operation.

Embodiment 4.
In the fourth embodiment, a specific example in which the switch circuit 3 is configured by using the MOS-FET and the gate voltage of the MOS-FET is clamped by using the Zener diode will be described. FIG. 5 is a configuration example of the switch circuit 3 according to the fourth embodiment of the present invention, and is a diagram showing a case where a protection circuit is provided.

The switch circuit 3 shown in FIG. 5 includes a current limiting resistor 36, a Zener diode 37, a pull-down resistor 33, and a MOS-FET 35. Specifically, the switch circuit 3 according to the fourth embodiment includes a MOS-FET 35 used as an element of an electronic switch, a current limiting resistor 36 for dividing the voltage supplied from the secondary output 102, and a pull-down resistor. 33 and are arranged. Further, in the switch circuit 3 according to the fourth embodiment, a Zener diode 37 having one end connected to the ground is arranged at a connection point between the current limiting resistor 36 and the pull-down resistor 33. Then, when the divided voltage exceeds the threshold value between the gate and the source of the MOS-FET 35, the MOS-FET 35 is turned on and the power supply signal 103 becomes a low level.

On the other hand, when the MOS-FET 35 is off, the power supply signal 103 becomes the logic power supply 111 due to the pull-up resistor 5, and becomes a high level. As a result, a high / low signal at the voltage level of the logic power supply 111 is output as the power supply signal 103 according to the voltage of the secondary side output 102.

When the voltage of the secondary output 102 is large, the Zener diode 37 clamps the voltage applied to the gate of the MOS-FET 35 to protect the MOS-FET 35. Therefore, the switch circuit 3 provided with the protection circuit can be realized by the configuration shown in FIG.

The Zener current of the Zener diode 37 is determined by the current limiting resistor 36 and the secondary output 102.

Further, the Zener diode 37 can substitute another element as long as it is an element that can clamp the voltage. As an example, the voltage applied to the gate of the MOS-FET 35 may be clamped by the forward voltage of the silicon diode or the light emitting diode (LED). Alternatively, the voltage may be constantized by an IC such as a shunt regulator to clamp the voltage applied to the gate of the MOS-FET 35.

Embodiment 5.
In the fifth embodiment, a specific example in which the switch circuit 3 is configured by using the MOS-FET and the on-voltage of the MOS-FET is raised by using the Zener diode will be described. FIG. 6 is a configuration example of the switch circuit 3 according to the fifth embodiment of the present invention, and is a diagram showing a case where a voltage adjusting circuit is provided.

The switch circuit 3 shown in FIG. 6 includes a current limiting resistor 36, a Zener diode 37, a pull-down resistor 33, and a MOS-FET 35. Specifically, the switch circuit 3 according to the fifth embodiment includes a MOS-FET 35 used as an element of an electronic switch, a Zener diode 37 that divides the voltage supplied from the secondary output 102, and a current limiting resistor. 36 and are arranged. Further, in the switch circuit 3 according to the second embodiment, the connection point between the Zener diode 37 and the current limiting resistor 36 is connected to the pull-down resistor 33 and the gate of the MOS-FET 35.

If the Zener voltage value of the Zener diode 37 is not exceeded, the Zener diode 37 does not conduct. Therefore, the on-voltage of the MOS-FET can be increased. Therefore, with the configuration shown in FIG. 6, a switch circuit 3 provided with a voltage adjusting circuit for adjusting the on-voltage of the MOS-FET can be realized.

In the above-described embodiments 2 to 5, the case where the switch included in the switch circuit 3 is configured as an electronic switch has been described, but it is also possible to configure the switch to include a mechanical switch by using a relay.

Embodiment 6.
FIG. 7 is a diagram showing an overall configuration when the power supply monitoring device according to the present invention is applied to the PLC in the sixth embodiment of the present invention. Specifically, in the sixth embodiment, the case where the power supply monitoring device according to the above-described first to fifth embodiments is applied to the analog output unit of the building block type PLC will be described.

The analog output 114 and the D / A circuit 11 are isolated from the PLC by the isolated power supply circuit 2 and the isolator 12.

The main power supply of the unit supplied from the base is connected to the main power supply input 110. The voltage of the main power supply is monitored by the voltage monitoring circuit 4b. When the step-down circuits 7a and 7b are turned on, the microcomputer 8 corresponding to the controller of the analog output unit is started. The microcomputer 8 performs bidirectional communication with the CPU of the PLC via the I / F circuit 9 and the external I / F 113, and executes control of the analog output unit.

The controller that captures whether the switch is in the on state or the off state as an input signal and executes control according to the input signal is not limited to the microcomputer 8. The controller also includes a device that controls input / output with a logic circuit or a relay circuit without using a microcomputer.

When the analog output unit is activated, the microcomputer 8 and the CPU can communicate with each other even if the external power input 101 is not applied, and the analog output unit can be controlled by the CPU. However, when the external power input 101 is not applied, the microcomputer 8 does not issue an output command to the D / A circuit 11.

Further, when the external power input 101 is not applied, the microcomputer 8 can output a notification signal to notify the user that the external power input 101 is not applied by the LED 10. At this time, the CPU of the PLC can detect this notification signal by performing bidirectional communication with the microcomputer 8.

The LED 10 is used to visually notify the user, and the LED 10 can be notified by a display, a buzzer, or the like in addition to the LED 10.

In FIG. 7, the configuration for generating a power supply signal based on the external power supply input 101 using the isolated power supply circuit 2, the switch circuit 3, and the voltage monitoring circuit 4a is a power supply having the configurations of FIGS. 1 and 4. Corresponds to a monitoring device.

Therefore, by applying the power supply monitoring device shown in FIG. 7, the rated voltage assumed at the time of design is normally applied to the external power supply input 101, and the insulated power supply circuit 2 operates to generate the secondary output 102. When it is output, the power supply signal 103 is notified to the microcomputer 8 as an input signal.

As a result, by taking in the power supply signal 103, the microcomputer 8 does not use a photocoupler or the like, and does not use the signal between the primary and secondary of the insulated power supply circuit 2, from the secondary side to the primary side. It is possible to indirectly determine whether or not a certain external power supply input 101 is supplied.

Further, when the insulated power supply circuit 2 does not operate due to damage or the like, the power supply signal 103 is invalidated. Therefore, the microcomputer 8 can detect an abnormality even when the isolated power supply circuit 2 fails. Therefore, the microcomputer 8 can also use the power supply signal 103 as a fail-safe.

As is clear from the above description, the power supply monitoring device according to the present invention has an external power supply that is isolated from the main power supply, such as a PLC and a measuring instrument, and operates according to a determination result of whether or not an external power supply is supplied. It can be used in industrial equipment that changes.

Specific examples of the operation of industrial equipment include an insulated D / A output, an insulated A / D output, an instrument, a temperature input, a network unit, a unit having a communication I / F, and the like. Further, as an application example, by applying the power supply monitoring device according to the present invention to the servo amplifier, the servo control can be stopped when the power supply voltage of the motor is abnormal.

Further, as another application example, by applying the power supply monitoring device according to the present invention to the measuring instrument, the measurement can be stopped when the power supply for the communication device is not supplied.

For devices that use a battery as the main power source and can connect an AC power source as an auxiliary power source equivalent to an external power source, it is also possible to save data and put it in a standby state when the auxiliary power supply is no longer supplied. ..

1 Main power supply circuit, 2 Insulated power supply circuit, 3 Switch circuit, 4, 4a, 4b Voltage monitoring circuit, 5 Pull-up resistor, 6 Second switch, 7a, 7b Step-down circuit, 8 Microcomputer, 9, I / F circuit, 10 LED (notifier), 11 D / A circuit, 12 isolator, 31 resistor, 32 base resistor, 33 pull-down resistor, 34 transistor, 35 MOS-FET, 36 current limiting resistor, 37 Zener diode, 101 external power supply input, 102 Next side output, 103 power supply signal, 110 main power input, 111 logic power supply, 112 microcomputer power supply, 113 external I / F, 114 analog output.

Claims (9)

An isolated power supply circuit that inputs an external power supply different from the main power supply and outputs a secondary power supply that is isolated from the external power supply.
It is provided on the primary side of the insulated power supply circuit and monitors whether or not the external power supply is normally applied to the insulated power supply circuit. If the external power supply is not normally applied, the external power supply is abnormal. A voltage monitoring circuit that controls the secondary power supply so that it is not output from the insulated power supply circuit.
A switch circuit including a switch that is turned on when the secondary power supply is normally output and is turned off when the secondary power supply is not normally output .
A series circuit provided on the secondary side of the isolated power supply circuit by connecting a pull-up resistor and the switch circuit in series between the logic power supply generated based on the input of the main power supply and the ground. equipped with a door,
A power supply monitoring device in which the voltage at the connection point between the pull-up resistor and the switch circuit is output to the outside as a power supply signal. In the isolated power supply circuit, a second switch provided between the input terminal for inputting the external power supply and the external power supply and capable of switching between an on state and an off state is further provided.
Wherein the voltage monitoring circuit, when it is determined that the external power failure, the second switch switched Rukoto the off state, wherein the insulating power supply circuit the secondary power supply is controlled so as not to be outputted, the If it is determined not to be an external power failure, the second switch by switching the oN state, the power supply according to claim 1, wherein the insulating power supply circuit the secondary power supply is controlled to Ru output Monitoring device. The insulated power supply circuit can switch between a start state in which the secondary side power supply is output and a stop state in which the output of the secondary side power supply is stopped according to an external signal.
When the voltage monitoring circuit determines that the external power supply is abnormal, the voltage monitoring circuit outputs the external signal so as to put the insulated power supply circuit in the stopped state, so that the secondary power supply is output from the insulated power supply circuit. When it is determined that the external power supply is not abnormal, the external power supply is output so as to bring the insulated power supply circuit into the activated state, so that the secondary power supply is supplied from the insulated power supply circuit. power supply monitoring apparatus according to claim 1 for controlling so as Ru is output. The switch included in the switch circuit is an electronic switch using a transistor or a MOS-FET that switches to an on state when the secondary power supply is normally output, according to any one of claims 1 to 3. The power supply monitoring device described. The power supply according to any one of claims 1 to 3, wherein the switch included in the switch circuit is a mechanical switch by a relay that switches to an on state when the secondary power supply is normally output. Monitoring device. The power supply monitoring device according to any one of claims 1 to 5, wherein the switch circuit further includes a protection circuit that protects the switch according to the magnitude of the voltage of the secondary power supply. Any of claims 1 to 5, wherein the switch circuit further includes a voltage adjusting circuit that switches the switch to the on state when the magnitude of the voltage of the secondary power supply becomes equal to or larger than a preset on voltage value. The power supply monitoring device according to item 1. The power supply according to any one of claims 1 to 7, further comprising a controller that captures whether the switch is in the on state or the off state as an input signal and executes control according to the input signal. Monitoring device. The power supply according to claim 8, wherein the controller outputs a notification signal for notifying the outside that the secondary power supply is not normally output when the switch is in the off state. Monitoring device.

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