JP2012182875A - Power supply circuit of explosion proof electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a voltage applied to a load and limit the voltage and a curent of the load with high accuracy even when the current flowing through the load of an explosion proof electronic apparatus varies.SOLUTION: A booster circuit 12 is connected with an electric power source 1, and a current is supplied from the booster circuit 12 to the load 10 through resistors 4, 5. A voltage applied to the load 10 is stabilized by controlling a booster voltage of the booster circuit 12 using the voltage applied to the load 10 when the current is supplied to the load 10. Zener diodes 6, 7 are connected in parallel with the load 10 and limit the voltage applied to the load 10 to a predetermined value. The voltage applied to the load 10 and a current flowing through the load 10 are limited by the booster circuit 12, the resistors 4, 5, and the zener diodes 6, 7 with high accuracy.

Description

  The present invention relates to a power supply circuit for an explosion-proof electronic device used in an environment where chemicals or solvents that are flammable or explosive are handled. The power supply circuit of the present invention is particularly suitable for a case where a stable power supply voltage is required even when the load current fluctuates in a wireless terminal using many ICs and electronic devices.

  A standard for ensuring safety is defined for an electrical machine apparatus used in an explosive atmosphere that requires explosion prevention, and is described in Non-Patent Document 1.

  This standard stipulates that the power circuit used in explosion-proof electronic equipment should keep the load power below a certain value. In other words, it is obliged to take measures to prevent an abnormal voltage from being applied to the load or excessive current to flow to generate heat or ignite. To this end, multiple resistors or current limiting circuits are connected in series between the power supply terminal and the load to suppress excessive current, and multiple Zener diodes are connected in parallel to the load so that the voltage does not increase more than necessary. Is commonly used.

Electromechanical devices used in explosive atmospheres, Part 0: General requirements, Part 11: Intrinsically safe explosion-proof structure “i”, Part 25: Intrinsic safety system, Japanese Industrial Standards, JIS C60017-1, JIS C60007-11 , JIS C60007-25

When the voltage applied to the load is V, the current flowing through the load is I, and the load resistance is R, the power consumption P of the load is
P = IV = I ² R = V ² / R (1)
Calculated by In explosion-proof electronic equipment, it is necessary to limit the voltage V and current I in order to keep the power P applied to the load below a certain value.

  FIG. 7 shows an example of a conventional power supply circuit used in explosion-proof electronic equipment. This power supply circuit will be described. The voltage Va between the output terminals 102 and 103 of the power supply 101 such as a battery is limited in power consumption of the load 110 by two resistors 104 and 105 and two Zener diodes 106 and 107.

  When a problem occurs in the load 110 and a short circuit occurs, the current is limited by the resistors 104 and 105, and heat generation on the load side is suppressed, so that an explosion-proof performance is obtained. Instead of using the resistors 104 and 105, a current limiting circuit may be used.

  In FIG. 7, the Zener diodes 106 and 107 prevent the voltage Vb between the terminals 108 and 109 from being applied to the load 110 beyond a certain value. The zener diodes 106 and 107 not only prevent the load 110 from being applied with an excessive voltage when the current flowing through the load 110 decreases, but also when the main power supply voltage Va becomes a high value. The voltage Vb is prevented from becoming abnormally high.

  The reason why the two resistors 104 and 105 are used as the resistors for limiting the current is to suppress the current flowing to the load by the other resistor to some extent even if a failure occurs in which one resistor becomes conductive. It is. Similarly, a plurality of Zener diodes 106 and 107 are connected in parallel so that even if one of them is cut off due to a failure, the other can suppress the voltage of Vb.

  In the power supply circuit of FIG. 7, when the current consumed by the load 110 fluctuates, the value of the voltage Vb fluctuates with the fluctuation, and there is a problem that stable power supply cannot always be performed. In particular, when a wireless terminal including many integrated components such as a signal processor is used as the load 110, the voltage fluctuation applied to the entire load 110 has been a serious problem in terms of performance such as spurious characteristics of the wireless terminal.

  These problems of voltage fluctuation applied to the load 110 are the same even if the resistors 104 and 105 are replaced with current limiting circuits, respectively, and the problem has not been solved.

  The subject of the present invention is that it is possible to supply a stable voltage to the load side even when there is a fluctuation in the current consumption of the load after taking an explosion-proof measure based on the standard of Non-Patent Document 1. It is to greatly improve the electrical characteristics.

  Furthermore, the meaning of equation (1) means that if the voltage or current limit is inaccurate, the power limit will be accompanied by a larger error to “square” the voltage or current, It is an object of the present invention to provide means for limiting the power consumption of a load with higher accuracy than before by performing these limitations more accurately.

  In order to solve the above problems, a power supply circuit for an explosion-proof electronic device according to the present invention has a booster circuit for boosting a voltage between two poles of a power supply and at least one terminal on the output side of the booster circuit in series with one or more resistors. And a circuit configuration for supplying a current to the load, and further, one or more Zener diodes are provided in parallel with the load so that the voltage applied to the load does not exceed a certain value. The booster circuit is configured to control the boost value to a predetermined value using the voltage applied to the load. Also, a current limiting circuit can be used instead of the resistor.

  As a booster circuit used in the present invention, a charge pump circuit that is more accurate than a case where an inductor is used and can obtain high efficiency with respect to a light load is more suitable. That is, as an example of a booster circuit used for the explosion-proof power source of the present invention, a first series circuit is provided by connecting a first diode and a second diode in series from the first terminal of the power source, The first electronic switch and the second electronic switch are connected in series from the first terminal to provide a second series circuit, and an electrical coupling portion of the first diode and the second diode and the first The electrical coupling portion of the second electronic switch and the second electronic switch are connected via a first capacitor, and the termination of the second series circuit is connected to the termination of the first series circuit via the second capacitor. In addition to being connected, it is configured to be connected to the second terminal of the power source. Further, the booster circuit has a switch open / close signal generating means for controlling the opening / closing of the first electronic switch and the second electronic switch, and the switch open / close signal generating means receives the first electronic switch of the first electronic switch. A first ON / OFF signal is generated to control opening and closing, and a second ON / OFF signal is generated to control opening and closing of the second electronic switch. And the second electronic switch are controlled so as not to be turned on at the same time, and both the first and second electronic switches are turned off if the voltage applied to the load is a certain value or more. Control as follows.

  Further, according to the present invention, when a current limiting circuit is used instead of a resistor that suppresses a current value so that an excessive current does not flow to the load, the current limiting circuit accurately sets the current value supplied to the load to a certain reference value. Using this method, the supply is limited when the standard value is reached.

  As an example of this current limiting circuit, a current is supplied to the load via a first resistor and a current limiting switch circuit in order from the input terminal, and a Zener diode and a second resistor are connected in series from the input terminal. As a result, a first reference voltage is generated by subtracting a voltage of a predetermined value from the voltage at the input terminal, and a third resistor and a fourth resistor are used between the input terminal and the first reference voltage. A second reference voltage is generated by dividing the resistance, and the voltage of the electrical coupling portion between the first resistor and the current limiting switch circuit is compared with the second reference voltage using a comparison means. Thus, a circuit for controlling the amount of current of the current limiting switch circuit by the output obtained by the comparison by the comparison means can be used. The current limiting switch circuit used here is not limited to a general bipolar transistor, but also includes an FET (field effect transistor).

  In the present invention, in a power circuit of an explosion-proof electronic device that limits power consumption at a load by a resistor or current limiting circuit connected in series to the load and a Zener diode connected in parallel to the load, By providing a booster circuit on the output terminal side of the power supply and controlling the boosted value of the booster circuit with the voltage applied to the load, the voltage applied to the load is stabilized to a constant value. Even when it fluctuates, a stable power supply voltage can be supplied to the load. Further, if the voltage applied to the load is stabilized, there is an effect of accurately limiting the voltage applied to the load.

  Further, in the present invention, if a charge pump circuit is used as a booster circuit, the circuit can be reduced in size compared with the case where an inductor is used. Even when a wireless device is used, the influence on the wireless characteristics due to inductive noise can be greatly reduced.

  Furthermore, by using the charge pump circuit, it is possible to obtain a boosted voltage with higher accuracy than when using an inductor.

  Furthermore, the current limiting circuit between the booster circuit and the load can be accurately limited to a predetermined value by accurately measuring the amount of current flowing through the load by using the circuit of the present invention. It is. In other words, as a current limiting circuit, a reference voltage that makes the difference from the power supply voltage constant is obtained from the power supply voltage via a Zener diode, and the reference voltage and the voltage obtained by flowing the current flowing through the load through the resistor are compared. As a result, even when the power supply voltage fluctuates, the current can be limited accurately and accurately.

It is a figure which shows the 1st Example of this invention. It is a figure which shows the 2nd Example of this invention. It is a figure which shows the 3rd Example of this invention. It is a figure which shows the structural example of the booster circuit used by this invention. It is a time chart for demonstrating operation | movement of a booster circuit. It is a figure which shows the structural example of the current limiting circuit used by this invention. It is a figure which shows the example of the conventional power supply circuit used for explosion-proof electronic equipment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First embodiment]
FIG. 1 is a diagram showing a first embodiment of the present invention. In the first embodiment, as shown in FIG. 1, a voltage Va between two poles of the power supply 1 is input and boosted, and an output-side terminal 13 (terminal 14 may be used) of the booster circuit 12. A zener having two resistors 4 and 5 connected in series, a voltage between the terminal of the resistor 5 and the terminal 14 of the booster circuit 12 being applied to the load 10 and connected in parallel to the load 10 The configuration includes diodes 6 and 7.

  A voltage Vb between the input terminals 8 and 9 of the load 10 is input to the booster circuit 12, and the booster circuit 12 controls the boost value to a predetermined value using this voltage Vb.

  The operation of the circuit shown in FIG. 1 will be described. The voltage Va between the output terminals 2 and 3 of the power source 1 is boosted to the value of Vc by the booster circuit 12, the voltage and current are limited by the two resistors 4 and 5, and the two Zener diodes 6 and 7, and the terminal 8 , 9 is applied to the load 10 as the voltage of the output Vb. In FIG. 1, the voltage Vb applied to the load is also used to control the boost value of the booster circuit 12, and when the value of the voltage Vb is likely to fall below a certain reference voltage, the booster circuit 12 displays the average voltage of the output. Is increased to a high value and the average voltage of the output is controlled to a low value when the voltage Vb tends to increase.

  The voltage is limited by the Zener diodes 6 and 7 so that a voltage higher than a certain value is not applied to the load 10, and the current is limited by the resistors 4 and 5 when a short circuit occurs due to some trouble in the load 10. Thus, heat generation on the load 10 side is suppressed. For this reason, not only the performance as explosion-proof is obtained, but also the voltage Vb applied to the load is stabilized so as to be always constant.

  In the first embodiment, since the voltage applied to the load 10 is controlled so as to be accurately constant, not only the voltage of the load is stabilized, but also the accuracy can be made a sufficient value.

[Second Embodiment]
FIG. 2 is a diagram showing a second embodiment of the present invention. As shown in FIG. 2, the second embodiment has a configuration in which the resistors 4 and 5 in FIG. 1 are replaced with current limiting circuits 15 and 16, respectively. In the second embodiment, the current limiting circuits 15 and 16 limit the current flowing through the load 10 to an accurate value, thereby reducing the power consumption of the load 10 compared to the first embodiment shown in FIG. It can be strictly limited.

[Third embodiment]
FIG. 3 is a diagram showing a third embodiment of the present invention. In principle, a circuit configuration as shown in FIG. 3 is also conceivable. This is a case where the power supply terminals 8 and 9 of the load 10 are made independent of the terminals 13 and 14 on the booster circuit 12 side. As a third embodiment, not only the current limiting effect due to the resistors 4 and 5, but also, for example, a high-frequency noise source is included on the booster circuit 12 side, which is not only from the terminal 13 side but also from the terminal 14 side. Therefore, when the load 10 is affected, the configuration shown in FIG. 3 may be considered due to the noise reduction effect of the resistors 4 and 5 and the stray capacitance on the load 10 side or the capacitor included in the load 10. In the example of FIG. 3, the voltage at the terminal 8 can be stabilized with respect to the booster circuit 12 side power supply. In FIG. 3, when the resistors 4 and 5 are replaced with current limiting circuits, the same effect can be expected if the influence on the load 10 side with respect to high frequency noise is reduced. Such a case is also included in the technical scope of the present invention.

[Configuration example of booster circuit]
FIG. 4 shows a configuration example of the booster circuit used in the first, second, or third embodiment. FIG. 5 is a time chart for explaining the operation of the booster circuit of FIG.

4, the voltage Va, Vc, Vd, Vx, Vy, Vz, V 24 are both voltage for terminal 3. In the booster circuit 12, the terminal 3 and the terminal 14 are electrically connected.

  A diode 20 and a diode 21 are connected in series from the terminal 2 to form a first series circuit, and further, an electronic switch 18 and an electronic switch 19 are connected in series from the terminal 2 to form a second series circuit. Has been.

  An intermediate portion between the diode 20 and the diode 21 and an intermediate portion between the electronic switch 18 and the electronic switch 19 are connected via a capacitor 22, and the output side of each of the first series circuit and the second series circuit is a capacitor. 23 is connected. An intermediate portion between the electronic switch 19 and the capacitor 23 is connected to the terminal 14.

In addition, a switch control circuit 17 is provided as a switch opening / closing signal generating means for controlling the opening / closing of the electronic switch 18 and the electronic switch 19, and the switch control circuit 17 provides an ON / OFF for controlling the opening / closing of the electronic switch 18. An OFF signal S ₁₈ is input to the electronic switch 18, and an ON / OFF signal S ₁₉ for controlling opening / closing of the electronic switch 19 is input to the electronic switch 19.

  The switch control circuit 17 controls the electronic switch 18 and the electronic switch 19 so that the electronic switch 18 and the electronic switch 19 are not turned on at the same time, and turns off both the electronic switches 18 and 19 if the voltage applied to the load is a certain value or more. It is controlled to become. In this case, since the voltage Va at the terminal 2 is sufficiently high, sufficient current is supplied to the terminal 13 via the diode 20 and the diode 21 even when both the electronic switches 18 and 19 are OFF. Can do.

The switch control circuit 17 inputs a voltage Vb applied to the load to the comparator 25, compares the voltage Vb with a reference voltage Vx obtained by using the resistor 26 and the Zener diode 27, and compares the voltage Vb with the comparator 25. The reference voltage Vy of 32 and the reference voltage Vz of the comparator 33 are generated. If Vb is a sufficiently high voltage, Vy is a high voltage and Vz is a low voltage. Comparator 32 and comparator 33, with the triangular wave V ₂₄ from the triangular wave generating circuit 24, by comparing Vy, and Vz, respectively, to obtain an ON / OFF signal S ₁₈ and S _19.

If Vb is higher than Vx voltage, Vy is high value, S ₁₈ becomes a signal of OFF, Vz at this time is low, S ₁₉ also outputs a signal OFF. However, if Vb is lower than Vx value, Vy is a little higher than the intermediate voltage of the triangular wave V _24, and Vz is set to be slightly lower voltage than the intermediate voltage of the triangular wave V _24, S the ₁₈ and S _19, the pulse of the waveform is output.

FIG. 5 illustrates this as a time chart. If Vb is the reference voltage Vx or more, Vy is above the highest value of the triangular wave V _24, Vz since is below the lowest value of the triangular wave V _24, ON / OFF signals S _18, S ₁₉ are both , A low value (OFF state). Vb is, to come down, and becomes equal to or less than the Vx, Vy and Vz are both made in the vicinity of the center voltage of the triangular wave V _24. In this case, Vy is slightly higher than the vicinity of the center voltage of the triangular wave V _24, Vz is as will become slightly lower than the vicinity of the center voltage of the triangular wave V _24, the resistance values of the resistors 28, 29 and the resistor 30 and 31 is determined It has been.

When the waveform of the triangular wave V ₂₄ is below Vz, S ₁₉ rises, and above Vy, S ₁₈ rises. The (state of ON) when S ₁₉ is up, one of the capacitor 22 to discharge to the terminal 3, Vd is can not be a high voltage, it remains close to the Va value. When S ₁₉ becomes a low value (OFF state) and S ₁₈ becomes a high value (ON state), Va is added and charged to the capacitor 22 through the electronic switch 18, so that Vd is twice as large as Va. It becomes a value close to the voltage (2Va). As a result, the voltage Vd near 2Va is applied to the capacitor 23 through the diode 21, so that the voltage near 2Va is maintained in the capacitor 23.

  The booster circuit shown in FIG. 4 is an example of a charge pump circuit in principle. When the load is light, not only can the booster be more efficient than when the inductance is used, but the booster circuit also boosts. The value can also be a precise and accurate value.

[Configuration example of current limiting circuit]
FIG. 6 shows a configuration example of the current limiting circuit used in the second embodiment. The current limiting circuit in FIG. 6 corresponds to the current limiting circuit 15 in FIG. Regarding the circuit configuration and operation, the current limiting circuit 15 and the current limiting circuit 16 are exactly the same.

  FIG. 6 shows a case where the transistor 42 is used as a current limiting switch circuit. How the transistor 42 is turned on / off will be described below.

The voltages Vc, Vp, Vq, and Vs of each part shown in FIG. The voltage V ₃₄ is a voltage difference between both ends of the Zener diode 34. Voltage Vp at the point P between the resistor 37 and the resistor 38, the voltage Vc of the input terminal 13, since a value obtained by subtracting only V _34, is calculated as Vp = Vc-V _34.

Further, assuming that the resistance values of the resistors ₃₆ and ₃₇ are R ₃₆ and R ₃₇ and the current flowing through the resistor 36 is I ₃₆ , the voltage difference between the terminal 13 and the point P is determined by the Zener diode 34. since always the value of V _34, a value of _{I 36 = V 34 / (R} 36 + R 37). That is, even when the value of Vc fluctuates due to fluctuations in the power supply voltage, the current I ₃₆ is always set to a constant value.

Therefore, the voltage Vs at the point S between the resistor 36 and the resistor 37 is calculated as Vs = Vc−R ₃₆ × I ₃₆ , but the current I ₃₆ is constant even when Vc fluctuates. The value is always a value obtained by subtracting a constant value (R ₃₆ × I ₃₆ ) from the voltage Vc at the terminal 13.

On the other hand, assuming that the resistance value of the resistor 35 is R ₃₅ and the current flowing through the resistor 35 is I ₃₅ , the voltage at the point Q between R ₃₅ and the transistor 42 is calculated as Vq = Vc−R ₃₅ × I ₃₅ .

  The transistor 42 is used to pass or block current flowing to the terminal 11. The comparator 39 compares the voltage Vs at the S point and the voltage Vq at the Q point. If Vs> Vq, the comparator 39 increases the base voltage of the transistor 42 to cut off the current flowing through the transistor 42, and Vs <Vq. If so, the base voltage of the transistor 42 is lowered to pass the current flowing through the transistor 42.

  If the output voltage of the comparator 39 is high, the resistors 40 and 41 turn off the transistor 42 to cut off the current flowing to the terminal 11. If the output voltage of the comparator 39 is low, the resistors 40 and 41 turn off the transistor 42. The value is selected so as to allow the current flowing to the terminal 11 to pass through.

  The comparator 39 obtains an output by comparing Vs and Vq. If Vs−Vq> 0, a high voltage is output, and if Vs−Vq <0, a low voltage is output.

The difference between the voltage Vs and the voltage Vq is
Vs−Vq = (Vc−R ₃₆ × I ₃₆ ) − (Vc−R ₃₅ × I ₃₅ )
= R ₃₅ × I ₃₅ −R ₃₆ × I ₃₆
= R ₃₅ × I ₃₅ - (constant voltage which is not affected by Vc)
Therefore, even if the power supply voltage fluctuates and the value of Vc changes, it can be seen that Vs−Vq is not affected by the power supply voltage fluctuation.

That is, the current limiting circuit shown in FIG. 6 can determine the passage and blocking of the transistor 42 by measuring the value of the voltage generated by the current I ₃₅ flowing through the resistor 35 without being affected by the power supply voltage fluctuation. . This means that the passage and blocking of the transistor 42 are determined by the current flowing through the resistor 35 even when the power supply voltage varies.

  FIG. 6 shows an example in which a PNP type transistor is used as the current limiting switch circuit, but it can also be realized by using an NPN type transistor. When using an NPN type transistor, the polarity of the comparator 39 is reversed, the emitter and collector of the transistor 42 are reversed, and the emitter side is connected to the terminal 11. The circuit is not limited to a general NPN or PNP type bipolar transistor, and a FET (field effect transistor) may be used.

  The current limiting circuit shown in FIG. 6 is an example, and the current limiting circuits 15 and 16 shown in FIG. 2 may have other circuit configurations having similar functions.

1,101 power supply 2,3,8,9,11,13,14,102,103,108,109,111 terminal 4,5,26,28-31,35-38,40,41,104,105 resistance 6, 7, 27, 34, 106, 107 Zener diode 10, 110 Load 12 Booster circuit 15, 16 Current limiting circuit 17 Switch control circuit 18, 19 Electronic switch 20, 21 Diode 22, 23 Capacitor 24 Triangular wave generating circuit 25, 32 , 33, 39 Comparator 42 Transistor

Claims (4)

A power supply circuit for supplying current to a load including an explosion-proof electronic device with limited power,
Power supply,
A booster circuit for boosting a voltage between two poles of the power source;
One or more resistors or current limiting circuits connected in series with the load between the output terminal of the booster circuit and the load;
One or more Zener diodes connected in parallel to the load so that the voltage applied to the load does not exceed a certain value,
The booster circuit inputs a voltage applied to the load, and controls a boost value based on the input voltage so that an output voltage from the booster circuit becomes a predetermined value. circuit. In the power circuit of the explosion-proof electronic device according to claim 1,
The booster circuit is a charge pump circuit composed of at least a plurality of capacitors and a plurality of electronic switches, and compares the voltage applied to the input load with a reference voltage generated from a voltage between two poles of the power supply. If the voltage applied to the input load is smaller than the reference voltage, the voltage between the two poles of the power supply is boosted by a charge pump and output. Otherwise, the voltage between the two poles of the power supply is A power circuit for explosion-proof electronic equipment, characterized by output without boosting. The power circuit of the explosion-proof electronic device according to claim 2, wherein the booster circuit is:
A first series circuit in which a first diode and a second diode are connected in series from the first terminal of the power supply;
And a second series circuit in which a first electronic switch and a second electronic switch are connected in series from the first terminal of the power source,
An electrical coupling portion of the first diode and the second diode, and an electrical coupling portion of the first electronic switch and the second electronic switch are connected via a first capacitor;
The termination of the second series circuit is connected to the termination of the first series circuit via a second capacitor and to the second terminal of the power source,
A switch opening / closing signal generating means for controlling opening / closing of the first electronic switch and the second electronic switch;
The switch opening / closing signal generating means generates a first ON / OFF signal for controlling the opening / closing of the first electronic switch, and a second ON / OFF for controlling the opening / closing of the second electronic switch. The first electronic switch and the second electronic switch are controlled so as not to be turned on simultaneously, and if the voltage applied to the load exceeds a certain value, the first electronic switch and the second electronic switch are controlled. A power supply circuit for an explosion-proof electronic device, wherein both the electronic switch and the second electronic switch are controlled to be OFF. In the power circuit of the explosion-proof electronic device according to claim 1, claim 2 or claim 3,
The current limiting circuit is:
A current is supplied to the load through a first resistor and a current limiting switch circuit in order from the input terminal,
By connecting a Zener diode and a second resistor in series from the input terminal, a voltage of a fixed value is subtracted from the voltage of the input terminal to generate a first reference voltage,
A second reference voltage is generated by resistance-dividing between the input terminal and the first reference voltage using a third resistor and a fourth resistor;
The voltage of the electrical coupling portion between the first resistor and the current limiting switch circuit and the second reference voltage are compared using a comparison means, and the current is determined by the output obtained by comparison using the comparison means. A power supply circuit for explosion-proof electronic equipment, characterized in that it is a circuit for controlling the amount of current of a limiting switch circuit.

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