JP2004070709A - Power unit for intrinsically safe apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly supply power to an intrinsically safe apparatus without deteriorating voltage use efficiency or current use efficiency by feedback controlling the voltage of a shunt voltage limiting circuit. <P>SOLUTION: This power unit is provided with a constant voltage control circuit 2, a fuse 1, and a voltage limiting circuit 3 successively from an input side to an output side. The voltage limiting circuit 3 is provided with an output short-circuit 3a for short-circuiting a power source circuit when operating voltage exceeds a predetermined voltage, a shunt voltage limiting circuit 3b for limiting the operating voltage of the output short-circuiting circuit 3a, and a voltage detecting circuit 3c for detecting output voltage. When input voltage to a power source circuit 10 reaches or exceeds the limit voltage of the shunt voltage limiting circuit 3b, the difference between the input voltage and the limit voltage is detected by a voltage detecting circuit 3c, and when the detected voltage is the operating voltage of the output short-circuit 3a or less, a constant voltage control circuit 2 carries out feedback-control so that the output voltage matches reference voltage. When the detected voltage of the voltage detecting circuit 3c reaches or exceeds the operating voltage of the output short-circuit 3a, the power source circuit is short-circuited by the output short-circuit 3a. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power source for supplying electric power from an intrinsically safe explosion-proof structure (hereinafter, referred to as intrinsically safe equipment) to be used in a hazardous area in an explosive atmosphere where explosive gas may explode. The present invention relates to a power supply for low-cost equipment.
[0002]
[Prior art]
When supplying DC power when using intrinsically safe equipment, ensure that overvoltages generated on the power supply circuit side are not output to the intrinsically safe equipment, and that the voltage and current values of the supplied power supply are applied to explosive gas in the hazardous area. Accordingly, the reference value must be smaller than the standardized value. For this reason, a power supply device for an intrinsically safe device that supplies power to the intrinsically safe device from a safe area is provided with a safety maintaining function for limiting an output voltage and an output current to the intrinsically safe device.
[0003]
As shown in FIG. 5A, as a conventional power supply device for intrinsically safe equipment having a safety maintaining function, a shunt voltage limiting circuit 52 for limiting the output voltage to intrinsically safe equipment and an output current for intrinsically safe equipment are limited. And a shunt diode type safety retainer 50 including a fuse 51 for protecting the shunt voltage limiting circuit 52. The shunt voltage limiting circuit 52 includes a shunt diode, and a zener diode is generally used as the shunt diode.
[0004]
When the circuit voltage of the power supply device for intrinsically safe device becomes higher than the limit voltage of the shunt diode (for example, the Zener voltage of the Zener diode) in the shunt voltage limit circuit 52, a current flows through the shunt voltage limit circuit 52, The output voltage value for the safety device is limited to the limit voltage. However, in the shunt diode type safety retainer 50 shown in FIG. 5A, the shunt voltage limiting circuit 52 must be grounded in the best way to reduce the ground voltage.
[0005]
Therefore, as shown in FIG. 5B, an insulating transformer 61 is arranged between the shunt voltage limiting circuit 52 and the current limiting circuit 53, and the shunt voltage limiting circuit 52 does not need to be grounded. A shunt diode type safety retainer 60 has been proposed.
[0006]
[Problems to be solved by the invention]
However, in the conventional shunt diode type safety retainer shown in FIGS. 5A and 5B, when the limiting voltage of the shunt diode constituting the shunt voltage limiting circuit 52 is close to the circuit voltage, Even when the voltage slightly increases, a current flows through the shunt voltage limiting circuit 52, and there is a possibility that the fuse 51 is easily blown due to a change in the circuit voltage. In general, the work of replacing fuses in the safety retainer of the power supply unit for intrinsically safe equipment is complicated and requires a long time.Fuse blowing should be avoided as much as possible, and the circuit voltage should be sufficiently compared to the Zener voltage. The value must be low, and as a result, it is necessary to use a Zener diode having a high Zener voltage. In addition, the voltage utilization efficiency can be increased by constantly flowing a current that does not blow the fuse into the circuit regardless of the load current, but the current utilization efficiency is reduced.
[0007]
SUMMARY OF THE INVENTION It is an object of the present invention to supply power to the intrinsically safe device without lowering the voltage use efficiency and the current use efficiency by performing feedback control of the voltage of the shunt voltage limiting circuit, and to easily fuse the device. It is an object of the present invention to provide a power supply device for intrinsically safe equipment that does not melt.
[0008]
[Means for Solving the Problems]
The present invention has the following arrangement as means for solving the above-mentioned problems.
[0009]
(1) In a power supply for intrinsically safe explosion-proof equipment that supplies DC power to intrinsically safe equipment,
A shunt voltage limiting circuit that limits the output voltage of the DC power supply, a voltage detection circuit that detects a voltage value of the output voltage limited by the shunt voltage limiting circuit, and a detection voltage of the voltage detection circuit is equal to or higher than the operating voltage. An output short-circuit that operates when the power supply circuit is short-circuited, and a constant-voltage control circuit that feedback-controls the output voltage so that the detection voltage of the voltage detection circuit matches the reference voltage. It is characterized in that the limiting voltage is set so that a current always flows.
[0010]
In this configuration, while the output voltage is feedback-controlled to the reference voltage based on the detection voltage of the voltage detection circuit, the output voltage is supplied to the output short circuit as the detection voltage after being limited by the restriction voltage of the voltage restriction circuit. Therefore, when the output voltage fluctuates within a range not exceeding the operating voltage of the output short circuit, the output voltage is maintained at the reference voltage, and when the output voltage fluctuates beyond the operating voltage of the output short circuit, the output short circuit occurs. The circuit operates and the power supply circuit is short-circuited. For this reason, the output voltage and the output current in the range standardized according to the type of the explosive gas in the dangerous area are not stably supplied to the intrinsically safe device. Further, the limit voltage of the voltage limit circuit is set lower than the output voltage, and the voltage use efficiency is improved. Further, when an abnormal voltage is input, the detection voltage increases due to the high voltage applied from the constant voltage control circuit to the voltage detection circuit, and the power supply circuit is short-circuited by the output short circuit.
[0011]
(2) It is characterized by including a current detection circuit for detecting the output current of the DC power supply, and a current control circuit for performing feedback control of the output current so that the detection current value of the current detection circuit becomes equal to or less than the reference current.
[0012]
In this configuration, not only is the output voltage equal to the reference voltage, but also the output current flowing through the fuse is controlled to be equal to or less than the reference current. Therefore, by setting the reference current to be equal to or less than the fusing characteristics of the fuse, the fusing of the fuse required in the standard of the power supply circuit for intrinsically safe equipment is prevented.
[0013]
(3) An insulation transformer is arranged in the input / output path of the DC power supply, and the output short circuit, the voltage detection circuit, and the constant voltage control circuit are provided on at least one of the primary side and the secondary side of the insulation transformer. It is characterized by the following.
[0014]
In this configuration, the primary side output short circuit, the voltage detection circuit and the constant voltage control circuit of the isolation transformer, the isolation transformer, and the secondary side output short circuit, the voltage detection circuit and the constant voltage of the insulation transformer The DC power supply and the intrinsically safe device are connected via the control circuit. Therefore, the insulation state between the DC power supply and the intrinsically safe equipment is reliably maintained, and the voltage fluctuations that occur on the primary and secondary sides of the insulation transformer are individually detected on the primary and secondary sides, respectively. Is absorbed by
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram showing a configuration of a power supply device for intrinsically safe equipment (hereinafter, simply referred to as a power supply device) according to a first embodiment of the present invention. Do not supply overvoltages generated in the power supply circuit due to component failures, etc., to intrinsically safe equipment used in hazardous areas in an explosive atmosphere where explosive gas may explode. In addition, the voltage value and the current value to be supplied to the intrinsically safe device are standardized according to the type of explosive gas in the dangerous area, and the output voltage and the output current of the power supply 10 are equal to or less than the standardized reference voltage value. And must be kept below the reference current value. For this reason, the power supply device 10 according to this embodiment includes a constant voltage control circuit 2, a fuse 1, a voltage limit circuit 3, and a current limit from the input side connected to the DC power supply to the output side connected to the intrinsically safe device. The circuit 8 is provided.
[0016]
The voltage limiting circuit 3 is configured by connecting an output short circuit 3a in parallel to a series circuit including a shunt voltage limiting circuit 3b and a voltage detecting circuit 3c between power supply lines for the intrinsically safe device. The output short circuit 3a is made of, for example, a semiconductor such as a thyristor, has an input terminal connected between the shunt voltage limit circuit 3b and the voltage detection circuit 3c, and receives the detection voltage of the voltage detection circuit 3c. The output short circuit 3a short-circuits the power supply lines when the detected voltage exceeds a predetermined operating voltage, and prevents output voltage exceeding the reference voltage from being output to the intrinsically safe device. The shunt voltage limiting circuit 3b is constituted by, for example, a zener diode, and maintains the voltage between both ends at a constant zener voltage.
[0017]
Therefore, when the output voltage that is the voltage between the power supply lines fluctuates, the voltage across the voltage detection circuit 3c fluctuates, and the detection voltage input to the input terminal of the output short circuit 3a fluctuates. That is, the detection voltage input to the output short circuit 3a is a value obtained by subtracting the zener voltage (limit voltage) from the output voltage. The voltage detection circuit 3c is configured by, for example, a resistor, and indirectly detects the output voltage as a detection voltage obtained by subtracting the limit voltage from the output voltage.
[0018]
Note that the fuse 1 is provided based on a standard requirement for the voltage limiting circuit 3. Further, the current limiting circuit 8 is formed of, for example, a resistor, and limits an output current value supplied to the intrinsically safe device to a reference current value or less.
[0019]
The constant voltage control circuit 2 includes a voltage control circuit 2a, a feedback resistor 2b, a reference voltage circuit 2c, and a voltage error amplifier circuit 2d. The detection voltage of the voltage detection circuit 3c in the voltage limiting circuit 3 is input to the voltage error amplifier circuit 2d via the feedback resistor 2b. The voltage error amplifier circuit 2d compares the detection voltage input via the feedback resistor 2b with the reference voltage generated by the reference voltage circuit 2c, and supplies a difference voltage signal obtained by amplifying the difference between the two to the voltage control circuit 2a. The voltage control circuit 2a controls the output voltage based on the difference voltage signal from the voltage error amplifier 2d. As a result, feedback control is performed so that the output voltage indirectly detected by the voltage detection circuit 3c matches the reference voltage.
[0020]
With the above configuration, when the output voltage of the constant voltage control circuit 2 starts to increase, the voltage difference between the output voltage and the limit voltage of the shunt voltage limit circuit 3b also increases. This voltage difference is detected by the voltage detection circuit 3c. When the detected voltage is less than the operating voltage at which the output short circuit 3a operates, the constant voltage control circuit 2 performs feedback control so that the output voltage matches the reference voltage. When the output voltage of the constant voltage control circuit 2 further increases and the detection voltage of the voltage detection circuit 3c becomes higher than the operating voltage of the output short circuit 3a, the output short circuit 3a operates and the power supply circuit is short-circuited. Further, when an abnormal voltage is input to the power supply device 10, a high voltage is applied from the feedback resistor 2b of the constant voltage control circuit 2 to the output short circuit 3a of the voltage limiting circuit 3, and the output short circuit 3a operates. The power supply circuit is shorted. Furthermore, the input and the like of the output short circuit are protected from high voltage by the feedback resistance.
[0021]
As a result, DC power with an output voltage that matches the reference voltage is supplied to the intrinsically safe equipment, and excessive voltage is not input to the intrinsically safe equipment. Can prevent ignition of explosive gas.
[0022]
After the output short-circuit 3a short-circuits the power supply circuit, the power supply 10 is restored by turning off the power supply to the power supply 10 and then turning it on again.
[0023]
The shunt voltage limiting circuit 3b does not directly limit the output voltage but supplies a voltage for controlling the input voltage of the output short circuit 3a. The shunt voltage limiting circuit 3b and the voltage detecting circuit 3c always supply a current. The limit voltage is set so that the current flows. Therefore, the sum of the limit voltage of the shunt voltage limit circuit 3b and the detection voltage of the voltage detection circuit 3c becomes the output voltage of the power supply device 10. If there is no voltage drop of the voltage control circuit, the voltage utilization efficiency is approximately 100%. become.
[0024]
The fuse 1 can be arranged at an appropriate position on the input side of the output short-circuit 3a of the short-circuit control circuit 3 and, like the power supply device 20 shown in FIG. May be arranged.
[0025]
FIG. 3 is a block diagram showing a configuration of a power supply device according to the second embodiment of the present invention. A power supply device 30 according to this embodiment includes a constant voltage / current control circuit 4 instead of the constant voltage control circuit 2 shown in FIGS. The constant voltage / current control circuit 4 includes a feedback resistor 2b, a reference voltage circuit 2c, and a voltage error amplifier circuit 2d included in the constant voltage control circuit 2, and newly includes a voltage / current control circuit 4a, a current detection circuit 4b, It includes a voltage circuit 4c and a current error amplifier circuit 4d.
[0026]
The current detection circuit 4b detects an output current supplied from the power supply device 30 to the intrinsically safe device, and outputs a voltage corresponding to the detected current value as a detection voltage. The detection voltage of the current detection circuit 4b is input to the current error amplification circuit 4d together with the reference voltage generated by the reference voltage circuit 4c. The current error amplifier circuit 4d supplies the voltage / current control circuit 4a with a differential current signal obtained by amplifying a difference between the detection voltage input from the current detection circuit 4b and the reference voltage input from the reference current circuit 4c. The voltage / current control circuit 4a controls the output voltage of the DC power supply to match the reference voltage based on the difference voltage signal supplied from the voltage error amplifier circuit 2d, and controls the difference supplied from the current error amplifier circuit 4d. Control is performed based on the current signal so that the output current of the DC power supply becomes equal to or less than the reference current.
[0027]
With the above configuration, in the power supply device 30 according to this embodiment, the output voltage of the DC power supply to be supplied to the intrinsically safe device is made equal to the reference voltage, and the output current of the DC power supply to be supplied to the intrinsically safe device is the voltage. The current value is controlled so that the fuse 1 is not blown even when the limiting circuit 3 fails or the intrinsically safe device as a load is short-circuited.
[0028]
FIG. 4 is a block diagram showing a configuration of a power supply device according to a third embodiment of the present invention. A power supply device 40 according to this embodiment includes an insulating transformer 5 in a power supply circuit. In the power supply device 40, a voltage limiting circuit 3, a fuse 1, and a constant voltage / current control circuit 4 are provided on a primary side of an insulating transformer 5 to which an oscillation circuit 6 is connected, and an insulating transformer to which a rectifying / smoothing circuit 7 is connected. A constant voltage control circuit 2 and a voltage limiting circuit 3 are provided on the secondary side of the unit 5. In FIG. 4, the current limiting circuit is omitted.
[0029]
With this configuration, an insulation state between the power supply and the intrinsically safe device can be realized, and voltage fluctuations and current fluctuations due to the application of an abnormal voltage including noise to the power supply line on the primary side are reduced. Voltage fluctuations and current fluctuations caused by the application of abnormal voltage including noise on the power supply line between the voltage limiting circuit 3, the fuse 1, and the constant voltage / current control circuit 4 and between the secondary device and the intrinsically safe device are 2 This can be absorbed by the constant voltage control circuit 2 and the voltage limiting circuit 3 on the next side.
[0030]
Note that, on the primary side of the power supply device 40, the constant voltage control circuit 2 can be used instead of the constant voltage / current control circuit 4.
[0031]
【The invention's effect】
According to the present invention, the following effects can be obtained.
[0032]
(1) While the output voltage is controlled to the reference voltage based on the detection voltage of the voltage detection circuit, while the output voltage limited by the shunt voltage limiting circuit is supplied to the output short circuit as the detection voltage, the output voltage is short-circuited. If the output voltage fluctuates within the range not exceeding the operating voltage of the circuit, the output voltage is maintained at the reference voltage, and if the output voltage fluctuates beyond the operating voltage of the output short circuit, and if an abnormal voltage is input, The power supply circuit can be short-circuited by operating the output short circuit. As a result, it is possible to stably supply the intrinsically safe device with a voltage and a current in a range standardized according to the type of explosive gas in a dangerous area. Further, the limit voltage of the voltage limit circuit can be set to a value close to the output voltage, and the voltage use efficiency can be improved.
[0033]
(2) By not only making the output voltage equal to the reference voltage but also controlling the output current flowing through the fuse to be equal to or lower than the reference current, it is possible to prevent the fuse from being blown and to eliminate a complicated replacement operation.
[0034]
(3) Output short circuit, voltage detection circuit and constant voltage control circuit on the primary side of the isolation transformer, insulation transformer, and output short circuit, voltage detection circuit and the constant voltage control circuit on the secondary side of the insulation transformer By connecting the DC power supply and the intrinsically safe equipment through the, the insulation state between the DC power supply and the intrinsically safe equipment can be reliably maintained, and at the primary and secondary sides of the insulation transformer. The generated voltage fluctuation can be individually absorbed on each of the primary side and the secondary side. As a result, it is possible to stably supply the intrinsically safe device with an output voltage and an output current in a range standardized according to the type of explosive gas in a dangerous area.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a power supply device according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing another configuration of the power supply device.
FIG. 3 is a block diagram illustrating a configuration of a power supply device according to a second embodiment of the present invention.
FIG. 4 is a block diagram showing a configuration of a power supply device according to a third embodiment of the present invention.
FIG. 5 is a block diagram showing a configuration of a safety protector provided in a conventional power supply device.
[Explanation of symbols]
1-Fuse 2-Constant voltage control circuit 2a-Voltage control circuit 2b-Feedback resistor 2c-Reference voltage circuit 2d-Voltage error plastic clothing circuit 3-Voltage limiting circuit 3a-Output short circuit 3b-Shunt voltage limiting circuit 3c-Voltage Detection circuit 4-constant voltage / current control circuit 10, 20, 30, 40-power supply (power supply for intrinsically safe equipment)

Claims (3)

A power supply for intrinsically safe equipment that supplies DC power to intrinsically safe explosion-proof electrical equipment,
A shunt voltage limiting circuit that limits the output voltage of the DC power supply, a voltage detection circuit that detects a voltage value of the output voltage limited by the shunt voltage limiting circuit, and a detection voltage of the voltage detection circuit is equal to or higher than the operating voltage. An output short-circuit that operates when the power supply circuit is short-circuited, and a constant-voltage control circuit that feedback-controls the output voltage so that the detection voltage of the voltage detection circuit matches the reference voltage. Power supply for cheap equipment. 2. The method according to claim 1, further comprising: a current detection circuit that detects an output current of the DC power supply; and a current control circuit that performs feedback control of the output current such that a detection current value of the current detection circuit is equal to or less than a reference current. Power supply unit for intrinsically safe equipment as described. An insulation transformer is arranged in an input / output path of a DC power supply, and the output short circuit, a voltage detection circuit, and a constant voltage control circuit are provided on at least one of a primary side and a secondary side of the insulation transformer. The power supply device for intrinsically safe equipment according to claim 1.

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