WO2010073401A1 - アナログ電流出力回路 - Google Patents
アナログ電流出力回路 Download PDFInfo
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- WO2010073401A1 WO2010073401A1 PCT/JP2008/073836 JP2008073836W WO2010073401A1 WO 2010073401 A1 WO2010073401 A1 WO 2010073401A1 JP 2008073836 W JP2008073836 W JP 2008073836W WO 2010073401 A1 WO2010073401 A1 WO 2010073401A1
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- Prior art keywords
- voltage
- output
- power supply
- analog
- internal control
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0032—Control circuits allowing low power mode operation, e.g. in standby mode
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0045—Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Definitions
- the present invention relates to an analog current output circuit that supplies an analog current to a load (for example, a solenoid valve or a current input amplifier) that is a control target in a control system.
- a load for example, a solenoid valve or a current input amplifier
- a control system for example, a water level control system that controls the water level in a tank configured using a PLC (programmable logic controller), the load to be controlled is an electromagnetic valve that controls the flow rate of water. is there.
- PLC programmable logic controller
- the specification range of the resistance value of the 4 to 20 mA current receiver provided in the solenoid valve is generally 600 ⁇ or less.
- an output transistor and a load are arranged in series in this order between the power source and the ground, and an analog current that matches the output current command value flows to the load. In this configuration, the passing current of the output transistor is controlled.
- the resistance value of the solenoid valve serving as a load connected to the analog current output circuit varies depending on the type of the solenoid valve within the specification range (for example, 0 ⁇ to 600 ⁇ ).
- the voltage needs to be high enough.
- Patent Document 1 proposes a method for reducing the power loss in the output transistor by using a switching-type low-loss power source and continuously changing the power voltage in order to solve the above problem.
- a switching type step-down circuit is used as a power source, and a potential difference between a voltage supplied from the step-down circuit to the collector of an output transistor and an output terminal to which an emitter terminal is connected is detected by an OP amplifier. This is given as a Ref voltage to the switching step-down circuit.
- a technique for reducing the power consumption of the output transistor by keeping the collector-emitter voltage Vce of the output transistor at a constant value of about + 1V is disclosed.
- the present invention has been made in view of the above, and realizes reduction of power loss when the resistance value of the connected load is small and securing of high-speed response when the resistance value of the connected load is large.
- An object of the present invention is to obtain an analog current output circuit.
- the present invention provides an output transistor and a load arranged in series between a power source and a ground, and the output so that an analog output current to the load matches an output command current.
- the voltage of the power supply is either a first power supply voltage switched by the power supply voltage switching circuit or a second power supply voltage lower than the first power supply voltage.
- the power source voltage switching circuit is configured to output the first power source when the internal control voltage is smaller than the load end voltage according to a comparison result of a comparator that compares the internal control voltage with the load end voltage.
- the internal control voltage is an analog output current 0 From the predetermined analog output current value to the maximum value of the analog output current, a voltage trajectory rising in proportion to the current is shown, and the maximum analog output current value is connected.
- the load resistance value is generated by an internal control voltage generation circuit so as to intersect with the load end voltage when the load resistance value is a resistance value near the center of the specification range.
- the load voltage at the analog output maximum current value matches the output voltage of the internal control voltage generation circuit with reference to the resistance value near the center of the specification range of the resistance value of the connected load.
- FIG. 1 is a block diagram showing a configuration of an analog current output circuit according to Embodiment 1 of the present invention.
- FIG. 2 is a characteristic diagram illustrating the switching operation of the power supply voltage.
- FIG. 3 is a diagram illustrating a characteristic example of power loss when the power supply voltage is not switched.
- FIG. 4 is a diagram showing a characteristic example of power loss when the power supply voltage is switched according to the present invention.
- FIG. 5 is a block diagram showing a configuration of an analog current output circuit according to the second embodiment of the present invention.
- FIG. 6 is a block diagram showing a configuration of an analog current output circuit according to Embodiment 3 of the present invention.
- FIG. 7 is a block diagram showing a configuration of an analog current output circuit according to Embodiment 4 of the present invention.
- FIG. 1 is a block diagram showing a configuration of an analog current output circuit according to Embodiment 1 of the present invention.
- FIG. 2 is a characteristic diagram illustrating the switching operation of the power supply voltage
- FIG. 8 is a block diagram showing a configuration of an analog current output circuit according to the fifth embodiment of the present invention.
- FIG. 9 is a block diagram showing a configuration of an analog current output circuit according to Embodiment 6 of the present invention.
- 10 is a block diagram showing a configuration of an analog current output circuit according to Embodiment 7 of the present invention.
- FIG. 1 is a block diagram showing a configuration of an analog current output circuit according to Embodiment 1 of the present invention.
- the power loss in the output transistor increases when the resistance value of the connected load is small and the analog output current value is large. Therefore, the analog current output circuit according to the present invention can reduce the power loss in such a situation, and the analog output can be applied regardless of whether the resistance value of the connected load is large or small.
- the current value is rapidly changed from the minimum to the maximum, it is configured to respond quickly.
- the analog current output circuit includes a switching type DC / DC converter 1 as a power source. Between the voltage output terminal 1a of the DC / DC converter 1 and the ground, the output transistor 2, the load (resistance value R L ) 3, and the current detection resistor 4 are arranged in series in this order.
- the current detection resistor 4 inserted between the load 3 and the ground is also connected to one input of an operational amplifier (hereinafter referred to as “OP amplifier”) 14, and the current detection resistor 4 is connected to the current detection resistor 4.
- OP amplifier operational amplifier
- the generated voltage is detected, the insertion position of the current detection resistor 4 between the emitter of the output transistor 2 and the load is changed, and the connection of the two inputs of the OP amplifier 14 is changed.
- the voltage across the current detector may be detected.
- a voltage dividing circuit is provided by connecting the resistors 5 and 6 in series.
- the connecting portion is connected to one input terminal of the OP amplifier 7.
- the other input terminal of the OP amplifier 7 is connected to the output terminal of the switch 8 as a switching circuit, and the output terminal of the OP amplifier 7 is connected to the reference voltage terminal 1 b of the DC / DC converter 1.
- One input terminal of the switch 8 is connected to the positive terminal of the first reference voltage source 9, and the other input terminal of the switch 8 is connected to the positive terminal of the second reference voltage source 10. Switching of the switch 8 is controlled by the output state of the comparator 11. Both the negative terminal of the first reference voltage source 9 and the negative terminal of the second reference voltage source 10 are connected to the ground.
- the first reference voltage source 9 outputs a first reference voltage H.
- the second reference voltage source 10 outputs a second reference voltage L that is lower than the first reference voltage H.
- the switch 8, the first reference voltage source 9, and the second reference voltage source 10 as a whole constitute a power supply voltage switching circuit.
- One input terminal of the comparator 11 is connected to a connection portion (load end) between the emitter of the output transistor 2 and the load 3, and the other input terminal of the comparator 11 is connected to an output terminal of the voltage shifter 12.
- the output terminal of the DA converter 13 to which a current output command is input from the outside is connected to one input terminal of the OP amplifier 14 and is connected to the ground via a voltage dividing circuit formed by connecting resistors 15 and 16 in series. Has been. Connection portions of the resistors 15 and 16 are connected to an input terminal of the voltage shifter 12. Note that the entire voltage dividing circuit by the resistors 15 and 16 and the voltage shifter 12 constitute an internal control voltage generation circuit.
- the other input terminal of the OP amplifier 14 is connected to the connection portion between the load 3 and the current detection resistor 4, and the output terminal of the OP amplifier 14 is connected to the base of the output transistor 2 via the resistor 17. .
- the analog current output circuit operates as follows. That is, the DA converter 13 converts the digital value of the current output command input from the outside into an output command analog voltage and outputs it.
- the OP amplifier 14 generates a resistance corresponding to the difference between the output command analog voltage from the DA converter 13 and the output voltage corresponding to the analog output current to the load 3 detected by the current detection resistor 4.
- the current passing through the output transistor 2 is controlled so that an analog current that matches the command value of the current output command can be stably output to the load 3 through the device 17.
- the DC / DC converter 1 includes a power supply voltage VccH, which is a first power supply voltage, and the power supply voltage VccH according to the magnitude of the reference voltage supplied to the reference voltage terminal 1b from the outside.
- VccH a first power supply voltage
- VccL a lower second power supply voltage
- the switch 8 selects the first reference voltage source 9
- the DC / DC converter 1 generates the power supply voltage VccH based on the first reference voltage H input through the OP amplifier 7, and
- the switch 8 selects the second reference voltage source 10
- the power supply voltage VccL is generated based on the second reference voltage L input via the OP amplifier 7.
- the generated power supply voltage VccH or power supply voltage VccL is stably supplied from the voltage output terminal 1a to the output transistor 2 by the action of the feedback circuit formed by the voltage dividing circuit (resistors 5 and 6) and the OP amplifier 7. Supplied to the collector.
- the comparator 11 compares the magnitude relationship between the internal control voltage Va output from the voltage shifter 12 and the load end voltage Vb appearing at the connection portion (load end) between the emitter terminal of the output transistor 2 and the load 3, and Va ⁇ Vb In the case of, the control signal for causing the switch 8 to select the first reference voltage source 9 and for Va> Vb to output to the switch 8 a control signal for causing the switch 8 to select the second reference voltage source 10.
- the output command analog voltage output from the DA converter 13 is a voltage-converted digital value of the current output command
- resistors 15 and 16 that divide the output command analog voltage output from the DA converter 13.
- the voltage shifter 12 subtracts from the divided voltage in the voltage dividing circuit, so that 0 V is maintained during a period until the analog output current supplied to the load 3 reaches 0 to a predetermined analog current value 18 (see FIG. 2).
- the predetermined analog current value 18 the divided voltage inputted from the voltage dividing circuit is outputted as it is.
- FIG. 2 is a characteristic diagram illustrating switching of the power supply voltage.
- the horizontal axis represents the analog output current
- the vertical axis represents the voltage.
- the resistance value RL of the connected load 3 is 600 ⁇ , 300 ⁇ , 200 ⁇ , and 50 ⁇
- the straight line locus of each load end voltage Vb and the broken line locus of the internal control voltage Va are shown. An example is shown.
- the analog output current range 19 in which the internal control voltage Va is 0V is an analog output current range in which the voltage shifter 12 shifts the divided voltage to 0V.
- the internal control voltage Va shows a change along a straight locus rising from the analog output current range 19 that shifts as the analog output current increases.
- the straight locus of the internal control voltage Va that rises to the right intersects with the straight locus of the load end voltage Vb when the resistance value RL is 50 ⁇ , 200 ⁇ , and 300 ⁇ in this order.
- the linear locus of the load end voltage Vb when the resistance value RL is 300 ⁇ intersects with the maximum value of the analog output current. It does not intersect with the linear locus of the load end voltage Vb when the resistance value RL is 600 ⁇ .
- the comparator 11 compares the magnitude relationship between the internal control voltage Va and the load end voltage Vb. Therefore, in this embodiment, for example, the power supply voltage is switched as shown in FIG.
- the switch 8 selects the reference voltage source 9, so that a high power supply voltage VccH is used and Va> In the period 21 that is Vb, the switch 8 selects the reference voltage source 10, so that the low power supply voltage VccL is used.
- the resistance value RL of the load 3 is 50 ⁇ , which is smaller, the same power supply voltage is switched.
- Va ⁇ Vb is always satisfied, and the switch 8 continues to select the reference voltage source 9, so that the power supply voltage is not switched and the high power supply voltage VccH is always maintained. Used.
- the resistance value RL of the load 3 when the resistance value RL of the load 3 is small, even if the power supply voltage Vcc is the high power supply voltage VccH or the low power supply voltage VccL, the operation of the analog current output circuit is not adversely affected.
- the collector-emitter voltage Vce uses the lower power supply voltage VccL as the power supply voltage Vcc. Smaller than.
- the power supply voltage Vcc when the resistance value RL of the load 3 is large, the power supply voltage Vcc must always be a high power supply voltage VccH. However, when R L ⁇ 300 ⁇ , as shown in FIG. 2, the power supply voltage VccH is always high. Is used.
- FIG. 3 is a diagram illustrating a characteristic example of power loss when the power supply voltage is not switched.
- FIG. 4 is a diagram showing a characteristic example of power loss when the power supply voltage is switched according to the present invention. 3 and 4 show the relationship between the power loss and the analog output current when the resistance value RL of the connected load 3 is 0 ⁇ , 100 ⁇ , 200 ⁇ , 300 ⁇ , 400 ⁇ , 500 ⁇ , and 600 ⁇ .
- the boundary of the case of not performing the case of performing the switching of the power supply voltage, the resistance value R L is set to the middle of 300 ⁇ and 400 [Omega.
- the load voltage at the analog output maximum current value is determined based on the resistance value near the center of the specification range of the resistance value of the connected load.
- a load having a resistance value smaller than the resistance value near the center of the load has a high power supply voltage when the analog output current is small, and the analog output current is When it is large, a low power supply voltage is supplied to the output transistor.
- a high power supply voltage is always supplied to the output transistor for a load having a resistance value larger than the resistance value near the center.
- Embodiments 2 to 5 modifications of the power supply voltage switching circuit will be described as Embodiments 2 to 5, and modifications of the method for generating the internal control voltage Va will be described as Embodiments 6 and 7.
- FIG. FIG. 5 is a block diagram showing a configuration of an analog current output circuit according to the second embodiment of the present invention.
- the same or similar components as those shown in FIG. 1 are denoted by the same reference numerals.
- the description will be focused on the portion related to the second embodiment.
- FIG. 5 in the analog current output circuit according to the second embodiment, the configuration shown in FIG. 1 (first embodiment) is replaced with a power supply voltage switching circuit (switch 8, reference voltage sources 9, 10).
- a power supply voltage switching circuit (a power supply 25, a resistor 26, Zener diodes 27 and 28, and a switching transistor 29 as a switching circuit) is provided.
- the zener diodes 27 and 28 have cathodes connected in parallel to the power supply 25 via the resistor 26 and to the other input terminal of the OP amplifier 7.
- the anode of the Zener diode 27 is connected to the ground, and the anode of the Zener diode 28 is connected to the collector of the switching transistor 29.
- the base of the switching transistor 29 is connected to the output terminal of the comparator 11, and the emitter of the switching transistor 29 is connected to the ground.
- the Zener voltage Vzh of the Zener diode 27 is the first reference voltage H
- the Zener voltage Vzl of the Zener diode 28 is the second reference voltage L. Therefore, the voltage of the power supply 25 is higher than the Zener voltage Vzh.
- the comparator 11 sets the output level to a low level when the magnitude relationship between the input internal control voltage Va and the load end voltage Vb is Va ⁇ Vb.
- the transistor 29 maintains the OFF operation state, so that the Zener voltage Vzh (first reference voltage H) of the Zener diode 27 is input to the reference voltage terminal 1 b of the DC / DC converter 1 via the OP amplifier 7.
- the power supply voltage VccH is output from the voltage output terminal 1a of the DC / DC converter 1.
- the comparator 11 sets the output level to a high level when the magnitude relation between the input internal control voltage Va and the load end voltage Vb is Va> Vb.
- the transistor 29 is turned on, so that a current flows through the Zener diode 27 and the Zener voltage Vzl (second reference voltage L) passes through the OP amplifier 7 to the reference voltage terminal 1b of the DC / DC converter 1.
- the power supply voltage VccL is output from the voltage output terminal 1 a of the DC / DC converter 1.
- the high power supply voltage VccH and the low power supply voltage VccL corresponding to the resistance value RL of the connected load 3 are switched and supplied to the output transistor 2. be able to.
- FIG. 6 is a block diagram showing a configuration of an analog current output circuit according to Embodiment 3 of the present invention.
- the same or similar components as those shown in FIG. 1 (Embodiment 1) are denoted by the same reference numerals.
- the description will be focused on the portion related to the third embodiment.
- the power source DC / DC converter 1
- the power source DC / DC A DC converter 35
- the power supply voltage switching circuit switch 8, reference voltage sources 9, 10
- a power supply voltage switching circuit reference voltage source 37 for outputting another reference voltage, switch 36 as a switching circuit
- One terminal of the switch 36 is connected to the reference voltage terminal 35 b of the DC / DC converter 35, and the other terminal of the switch 36 is connected to the positive terminal of the reference voltage source 37.
- the negative terminal of the reference voltage source 37 is connected to the ground.
- the reference voltage source 37 outputs a predetermined reference voltage.
- the switching type DC / DC converter 35 has a reference voltage source that outputs the second reference voltage L inside, and when the reference voltage is not supplied from the outside to the reference voltage terminal 35b, the built-in reference voltage source Is used to generate the power supply voltage VccL and output it from the voltage output terminal 35a to the collector of the output transistor 2.
- the DC / DC converter 35 adds the first reference voltage H added to the second reference voltage L containing the reference voltage from the outside.
- the power supply voltage VccH is used to generate and output from the voltage output terminal 35a to the collector of the output transistor 2.
- the switch 36 is closed when the comparator 11 makes a comparison determination of Va ⁇ Vb, and connects the positive terminal of the reference voltage source 37 to the reference voltage terminal 35 b of the DC / DC converter 35.
- the switch 36 is in an open state when the comparator 11 makes a comparison determination of Va> Vb, and disconnects the positive terminal of the reference voltage source 37 from the reference voltage terminal 35b of the DC / DC converter 35. .
- the high power supply voltage VccH and the low power supply voltage VccL corresponding to the resistance value RL of the connected load 3 are switched and supplied to the output transistor 2. be able to.
- FIG. 7 is a block diagram showing a configuration of an analog current output circuit according to Embodiment 4 of the present invention.
- the same or similar components as those shown in FIG. 1 (Embodiment 1) are denoted by the same reference numerals.
- the description will be focused on the portion related to the fourth embodiment.
- a power source DC / DC converter 1 is used instead of the power source (DC / DC converter 1).
- DC converter H40, DC / DC converter L41) are provided, and a power supply voltage switching circuit (switch 42 as a switching circuit) is provided in place of the power supply voltage switching circuit (switch 8, reference voltage sources 9, 10). .
- the switching type DC / DC converter H40 has a reference voltage source that outputs a first reference voltage H therein, and generates a power supply voltage VccH using the built-in reference voltage source.
- the switching type DC / DC converter L41 has a reference voltage source for outputting the second reference voltage L therein, and generates the power supply voltage VccL using the built-in reference voltage source.
- the switch 42 selects the voltage (power supply voltage VccH) output from the DC / DC converter H40 to the voltage output terminal 40a and applies it to the collector of the output transistor 2 when the comparator 11 makes a comparison determination of Va ⁇ Vb. Output.
- the switch 42 selects the voltage (power supply voltage VccL) output from the DC / DC converter L41 to the voltage output terminal 41a and selects the collector of the output transistor 2 when the comparator 11 makes a comparison determination of Va> Vb. Output to.
- the high power supply voltage VccH and the low power supply voltage VccL corresponding to the resistance value RL of the connected load 3 are switched and supplied to the output transistor 2. be able to.
- FIG. 8 is a block diagram showing a configuration of an analog current output circuit according to the fifth embodiment of the present invention.
- the same or similar components as those shown in FIG. 7 (Embodiment 4) are denoted by the same reference numerals.
- the description will be focused on the portion related to the fifth embodiment.
- the power source (DC / DC converter H40, DC / DC converter L41) is used in the configuration shown in FIG. 7 (fourth embodiment). Instead, a power source (voltage source 45, DC / DC converter L44) is provided.
- the voltage source 45 outputs the power supply voltage VccH to one input terminal of the switch 42.
- the switching type DC / DC converter L44 generates a power supply voltage VccL based on the voltage of the built-in reference voltage source, and outputs it to the other input terminal of the switch 42.
- the switch 42 selects the output voltage (power supply voltage VccH) of the voltage source 45 and outputs it to the collector of the output transistor 2 when the comparator 11 makes a comparison determination of Va ⁇ Vb.
- the switch 42 selects the voltage (power supply voltage VccL) output from the DC / DC converter L44 to the voltage output terminal 44a when the comparator 11 makes a comparison determination of Va> Vb, and the collector of the output transistor 2 Output to.
- the high power supply voltage VccH and the low power supply voltage VccL corresponding to the resistance value RL of the connected load 3 are switched and supplied to the output transistor. Can do.
- FIG. 9 is a block diagram showing a configuration of an analog current output circuit according to Embodiment 6 of the present invention.
- the same reference numerals are given to the same or equivalent components as those shown in FIG. 5 (Embodiment 2).
- the description will be focused on the portion related to the sixth embodiment.
- an internal control voltage generation circuit (voltage dividing circuit and voltage by resistors 15 and 16) Instead of the voltage shifter 12 in the shifter 12), a voltage source 31 and a resistor 32 for the output voltage Vc are provided.
- the voltage dividing output terminal of the voltage dividing circuit (resistors 15 and 16) is directly connected to the other input terminal of the comparator 11.
- the positive end of the power supply 31 is connected to the ground, and the negative end of the power supply 31 is connected to the other input terminal of the comparator 11 via the resistor 32.
- the voltage source 31 and the resistor 32 are for realizing the function of the voltage shifter 12 of the first embodiment by another means, and the resistor is used so that the analog output current becomes the predetermined analog current value 18 shown in FIG. 32 and the voltage Vc are adjusted.
- FIG. 1 Since the reverse voltage ( ⁇ Vc) from the voltage source 31 is added to the divided voltage of the voltage dividing circuit (resistors 15 and 16) and input to the other input terminal of the comparator 11, FIG.
- the analog output current range 19 shown is 0 V, and an internal control voltage Va indicating a change in a straight locus rising from there is applied.
- the load end voltage Vb when the resistance value RL of the connected load 3 is 300 ⁇ is crossed at the maximum value of the analog output current.
- a control voltage Va can be generated.
- the application example to the second embodiment is shown, but the present invention can be similarly applied to the first and third to fifth embodiments.
- FIG. 10 is a block diagram showing a configuration of an analog current output circuit according to Embodiment 7 of the present invention.
- the same or similar components as those shown in FIG. 5 are denoted by the same reference numerals.
- the description will be focused on the portion related to the seventh embodiment.
- the comparator 11 has an offset adjustment function. Then, the voltage shifter 12 in the internal control voltage generation circuit (the voltage dividing circuit and the voltage shifter 12 by the resistors 15 and 16) is deleted, and the divided voltage of the voltage dividing circuit (the resistors 15 and 16) is directly applied to the comparator 11. The voltage is applied to the other input terminal.
- the offset adjustment volume 46 is operated so that an offset voltage is generated with respect to the divided voltage Va applied to the other input terminal, and the offset voltage is 0 V in the section of the analog output current range 19 shown in FIG. Adjust so that:
- the other input terminal of the comparator 11 is applied with 0 V during the analog output current range 19 shown in FIG. Therefore, the comparator 11 can correctly perform the comparison determination of Va ⁇ Vb and Va> Vb.
- An internal control voltage Va can be generated.
- the application example to the second embodiment is shown, but the present invention can be similarly applied to the first and third to fifth embodiments.
- the analog current output circuit according to the present invention can be applied to a system that performs control by an analog output current, such as a control system using an instrumentation system or a control computer, in addition to a sequence control system using a PLC. It is. Therefore, in the first to seventh embodiments described above, the solenoid valve is described as an example of the load to be connected, but a current input amplifier is also included as another load, for example.
- the analog current output circuit according to the present invention can reduce power loss and ensure high-speed response when the resistance value of the connected load is small, and can also ensure resistance of the connected load.
- the power loss is low, but it has a feature that can ensure high-speed response, so it is particularly useful as a high-speed analog current output circuit that suppresses temperature rise. Is suitable.
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Abstract
Description
2 出力トランジスタ
3 負荷
4 電流検出用抵抗器
5,6,15,16,17,26,32 抵抗器
7,14 演算増幅器(OPアンプ)
8,36,42 スイッチ(切替回路)
9 第1の基準電圧源
10 第2の基準電圧源
11 コンパレータ
12 電圧シフタ
13 DA変換器
25,47 電源
27,28 ツェナーダイオード
29 切替トランジスタ(切替回路)
31,45 電圧源
37 基準電圧源(別の基準電圧源)
46 ボリューム
図1は、この発明の実施の形態1によるアナログ電流出力回路の構成を示すブロック図である。前記したように、出力トランジスタでの電力損失が大きくなるのは、接続される負荷の抵抗値が小さく、かつ、アナログ出力電流値が大きいときである。そこで、この発明にかかるアナログ電流出力回路は、そのような状況において、電力損失を低減でき、かつ、接続される負荷の抵抗値が、大きい場合であっても小さい場合であっても、アナログ出力電流値を最小から最大に急激に変化させたときに高速に応答できるように構成した。
図5は、この発明の実施の形態2によるアナログ電流出力回路の構成を示すブロック図である。なお、図5では、図1(実施の形態1)に示した構成要素と同一ないしは同等である構成要素には同一の符号を付してある。ここでは、この実施の形態2に関わる部分を中心に説明する。
図6は、この発明の実施の形態3によるアナログ電流出力回路の構成を示すブロック図である。なお、図6では、図1(実施の形態1)に示した構成要素と同一ないしは同等である構成要素には同一の符号を付してある。ここでは、この実施の形態3に関わる部分を中心に説明する。
て、電源電圧切替回路(別の基準電圧を出力する基準電圧源37、切替回路としてのスイッチ36)を設けてある。
る。また、スイッチ36は、コンパレータ11がVa>Vbの比較判定をしているときは開状態になり、基準電圧源37の正極端をDC/DC変換器35の基準電圧端子35bとの接続を切り離す。
図7は、この発明の実施の形態4によるアナログ電流出力回路の構成を示すブロック図である。なお、図7では、図1(実施の形態1)に示した構成要素と同一ないしは同等である構成要素には同一の符号を付してある。ここでは、この実施の形態4に関わる部分を中心に説明する。
図8は、この発明の実施の形態5によるアナログ電流出力回路の構成を示すブロック図である。なお、図8では、図7(実施の形態4)に示した構成要素と同一ないしは同等である構成要素には同一の符号を付してある。ここでは、この実施の形態5に関わる部分を中心に説明する。
図9は、この発明の実施の形態6によるアナログ電流出力回路の構成を示すブロック図である。なお、図9では、図5(実施の形態2)に示した構成要素と同一ないしは同等である構成要素には同一の符号を付してある。ここでは、この実施の形態6に関わる部分を中心に説明する。
図10は、この発明の実施の形態7によるアナログ電流出力回路の構成を示すブロック図である。なお、図10では、図5(実施の形態2)に示した構成要素と同一ないしは同等である構成要素には同一の符号を付してある。ここでは、この実施の形態7に関わる部分を中心に説明する。
Claims (9)
- 電源とグランドとの間に、出力トランジスタと負荷とを直列に配置し、前記負荷へのアナログ出力電流が出力指令電流と一致するように前記出力トランジスタの通過電流を制御するアナログ電流出力回路において、
前記電源の電圧は、電源電圧切替回路が切り替えた第1の電源電圧と該第1の電源電圧よりも低い第2の電源電圧とのいずれかの電圧であり、
前記電源電圧切替回路は、内部制御電圧と負荷端電圧とを比較するコンパレータの比較結果に応じて、前記内部制御電圧が前記負荷端電圧よりも小さいときは前記第1の電源電圧を選択し、前記内部制御電圧が前記負荷端電圧よりも大きいときは前記第2の電源電圧を選択するように構成され、
前記内部制御電圧は、アナログ出力電流0から所定アナログ出力電流値までが0Vで、該所定アナログ出力電流値よりアナログ出力電流の最大値までは電流に比例した右肩上がりの電圧軌跡を示し、かつアナログ出力電流の最大値で、接続される前記負荷抵抗値が仕様範囲の中央付近の抵抗値である場合の負荷端電圧と交差するように内部制御電圧生成回路にて生成される、
ことを特徴とするアナログ電流出力回路。 - 前記内部制御電圧生成回路は、
前記出力指令電流に対応した電圧を分圧する分圧回路と、
前記分圧回路から出力される分圧電圧に一定の電圧シフトを行って前記内部制御電圧を出力する電圧シフタと、
を備えていることを特徴とする請求項1に記載のアナログ電流出力回路。 - 前記内部制御電圧生成回路は、
前記出力指令電流に対応した電圧を分圧する分圧回路と、
前記分圧回路から出力される分圧電圧をアナログ出力電流0から所定アナログ電流値に至るまでの期間の間だけ0Vに保持するのに必要な逆極性の電圧を出力する電圧源と、を備え、前記分圧電圧と前記電圧源の出力電圧とを加算した電圧が前記内部制御電圧として出力される、
ことを特徴とする請求項1に記載のアナログ電流出力回路。 - 前記電源は、供給される第1の基準電圧及び該第1の基準電圧よりも低い第2の基準電圧のいずれかに基づき、対応する前記第1の電源電圧と前記第2の電源電圧とを生成するスイッチング方式のDC/DC変換器であり、
前記電源電圧切替回路は、
前記第1の基準電圧を出力する第1の基準電圧源と、
前記第2の基準電圧を出力する第2の基準電圧源と、
前記コンパレータでの比較結果に応じて、前記内部制御電圧が前記負荷端電圧よりも小さいときは前記第1の基準電圧を前記DC/DC変換器に供給し、前記内部制御電圧が前記負荷端電圧よりも大きいときは前記第2の基準電圧を前記DC/DC変換器に供給する切替回路と、
を備えたことを特徴とする請求項1に記載のアナログ電流出力回路。 - 前記電源は、供給される第1の基準電圧及び該第1の基準電圧よりも低い第2の基準電圧のいずれかに基づき、対応する前記第1の電源電圧と前記第2の電源電圧とを生成するスイッチング方式のDC/DC変換器であり、
前記電源電圧切替回路は、
前記第1の基準電圧を出力する第1のツェナーダイオードであって、カソード端子が所定電圧の電源と前記DC/DC変換器とに接続され、アノード端子がグランドに接続される第1のツェナーダイオードと、
前記第2の基準電圧を出力する第2のツェナーダイオードであって、カソード端子が前記所定電圧の電源と前記DC/DC変換器とに接続される第2のツェナーダイオードと、
前記コンパレータでの比較結果、前記内部制御電圧が前記負荷端電圧よりも小さいときは前記第2のツェナーダイオードのアノード端子とグランドとの間の接続を遮断し、前記内部制御電圧が前記負荷端電圧よりも大きいときは前記第2のツェナーダイオードのアノード端子とグランドとの間を接続する切替回路と、
を備えたことを特徴とする請求項1に記載のアナログ電流出力回路。 - 前記電源は、内蔵する基準電圧源の電圧に基づき前記第2の電源電圧を生成するとともに、外部から別の基準電圧が入力されたとき、該別の基準電圧を前記内蔵する基準電圧源の電圧に加算して前記第1の電源電圧を生成するスイッチング方式のDC/DC変換器であり、
前記電源電圧切替回路は、
前記別の基準電圧を出力する基準電圧源と、
前記コンパレータでの比較結果に応じて、前記内部制御電圧が前記負荷端電圧よりも小さいときは前記基準電圧源を前記DC/DC変換器に接続し、前記内部制御電圧が前記負荷端電圧よりも大きいときは前記基準電圧源と前記DC/DC変換器との接続を切り離す切替回路と、
を備えていることを特徴とする請求項1に記載のアナログ電流出力回路。 - 前記電源は、内蔵する基準電圧源の電圧に基づき前記第1の電源電圧を生成するスイッチング方式の第1のDC/DC変換器と、内蔵する基準電圧源の電圧に基づき前記第2の電源電圧を生成するスイッチング方式の第2のDC/DC変換器とで構成され、
前記電源電圧切替回路は、前記コンパレータでの比較結果に応じて、前記内部制御電圧が前記負荷端電圧よりも小さいときは前記第1のC/DC変換器の出力電圧を前記出力トランジスタに供給し、前記内部制御電圧が前記負荷端電圧よりも大きいときは前記第2のDC/DC変換器の出力電圧を前記出力トランジスタに供給する切替回路、
を備えていることを特徴とする請求項1に記載のアナログ電流出力回路。 - 前記電源は、前記第1の電源電圧を出力する電圧源と、内蔵する基準電圧源の電圧に基づき前記第2の電源電圧を生成するスイッチング方式のDC/DC変換器とで構成され、
前記電源電圧切替回路は、前記コンパレータでの比較結果に応じて、前記内部制御電圧が前記負荷端電圧よりも小さいときは前記電圧源の出力電圧を前記出力トランジスタに供給し、前記内部制御電圧が前記負荷端電圧よりも大きいときは前記DC/DC変換器の出力電圧を前記出力トランジスタに供給する切替回路、
を備えていることを特徴とする請求項1に記載のアナログ電流出力回路。 - 前記出力トランジスタのエミッタと前記負荷との間、または前記負荷とグランドとの間に、アナログ出力電流を検出する抵抗器が設けられていることを特徴とする請求項1に記載のアナログ電流出力回路。
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EP08879196.7A EP2372887A4 (en) | 2008-12-26 | 2008-12-26 | Analog current output circuit |
PCT/JP2008/073836 WO2010073401A1 (ja) | 2008-12-26 | 2008-12-26 | アナログ電流出力回路 |
JP2010543742A JP5247824B2 (ja) | 2008-12-26 | 2008-12-26 | アナログ電流出力回路 |
US13/141,203 US8810078B2 (en) | 2008-12-26 | 2008-12-26 | Analog current output circuit |
CN200880132531.9A CN102265493B (zh) | 2008-12-26 | 2008-12-26 | 模拟电流输出电路 |
KR1020117013297A KR101307000B1 (ko) | 2008-12-26 | 2008-12-26 | 아날로그 전류 출력 회로 |
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US9960673B2 (en) * | 2015-02-16 | 2018-05-01 | Tdk Corporation | Control circuit and switching power supply |
KR20190015231A (ko) * | 2016-06-02 | 2019-02-13 | 니폰 제온 가부시키가이샤 | 환경 발전장치 및 전류 제어회로 |
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CN102265493B (zh) | 2014-09-17 |
KR20110082629A (ko) | 2011-07-19 |
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EP2372887A1 (en) | 2011-10-05 |
JPWO2010073401A1 (ja) | 2012-05-31 |
KR101307000B1 (ko) | 2013-09-11 |
US20110254527A1 (en) | 2011-10-20 |
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