High-precision current and voltage output switchable circuit

Abstract

The utility model relates to the technical field of switching circuits, in particular to a high-precision current and voltage output switchable circuit, which comprises a voltage follower used for being connected to a Vin end; the analog switch S1 is connected with the voltage follower, and the analog switch S1 is connected with a current output circuit and a voltage output driving circuit; the current output circuit is used for current output, the voltage output driving circuit is used for voltage output, and the output of the current output circuit and the output of the voltage output driving circuit are simultaneously connected together and are connected with a Vout end; the analog switch S1 is controlled by the MCU and controls the MCU to simulate voltage or current output so as to select the analog switch S1 to be connected with the voltage output driving circuit or the current output circuit. According to the utility model, current output and voltage output are simultaneously connected together, and output switching can be automatically realized.

Description

Technical Field

[0001] The utility model relates to the technical field of switchable circuits, in particular to a high-precision current and voltage output switchable circuit. Background Art

[0002] Currently, in automation control equipment, it is often necessary to use a voltage source or a current source to realize analog setting or feedback of the control quantity.

[0003] Commonly used methods include 0-10V voltage setting or 0-20mA / 4-20mA current setting, etc. These control devices usually need to be compatible with both voltage source output and current source output, and usually use a dip switch or jumper to achieve the switching between voltage source output and current source output. However, this method is cumbersome to use and requires manual switching. This method has poor reliability, especially in vibration or oily environments, which can easily lead to circuit failure. Utility Model Content

[0004] The purpose of the utility model is to provide a high-precision current and voltage output switchable circuit to solve the problems raised in the above background technology.

[0005] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0006] A high-precision current and voltage output switchable circuit, comprising:

[0007] A voltage follower, used to connect to the Vin terminal;

[0008] An analog switch S1 is connected to the voltage follower, and the analog switch S1 is connected to a current output circuit and a voltage output drive circuit;

[0009] The current output circuit is used for current output, and the voltage output driving circuit is used for voltage output. The outputs of the current output circuit and the voltage output driving circuit are connected together and connected to the Vout terminal.

[0010] The analog switch S1 is controlled by the MCU to control the MCU to output analog voltage or current, so as to select the analog switch S1 and the voltage output driving circuit or the current output circuit to realize the path.

[0011] Preferably, the voltage follower is based on op amp U1C.

[0012] Preferably, the current output circuit includes an operational amplifier U1B, a transistor Q3, an operational amplifier U1A and a transistor Q1 connected in sequence.

[0013] Preferably, the pull-down resistor R5 is connected between the analog switch S1 and the operational amplifier U1B, and is used to clamp the input voltage of the Vin terminal;

[0014] A resistor R4 is connected between U1B and transistor Q3 to limit the base current of transistor Q3;

[0015] A resistor R3 for limiting the base current of the transistor Q1 is connected between the operational amplifier U1A and the transistor Q1;

[0016] Resistor R1 is connected to transistor Q1, resistor R2 is connected to operational amplifier U1A and transistor Q3, resistor R8 is connected to transistor Q3, and resistor R1, resistor R2 and resistor R8 are used for input sampling of operational amplifier U1A to control the amplification ratio.

[0017] Preferably, the resistors R1 and R2 are connected with diodes D1 and D2 for avoiding full-scale distortion of the amplifier, and the transistor Q3 is connected with a diode D3 for output reverse connection protection.

[0018] Preferably, the voltage output driving circuit includes an operational amplifier U1D and a transistor Q5 connected in sequence.

[0019] Preferably, the pull-down resistor R11 is connected between the analog switch S1 and the operational amplifier U1D, and is used to clamp the input voltage of the Vin terminal.

[0020] Preferably, the transistor Q5 is connected to the resistors R12 and R13 for input sampling of the operational amplifier U1D and controlling the amplification ratio, and the connecting resistor R10.

[0021] Preferably, the Vout terminal has a capacitor C1 and a diode D4 connected to ground.

[0022] Preferably, a fuse F1 is connected between the capacitor C1 and the diode D4.

[0023] Compared with the prior art, the beneficial effects of the utility model are:

[0024] The utility model controls the MCU high and low level output through menu options, and is used to select the analog voltage / current output line, and is mainly used to provide occasions where the sensor needs analog output. The MCU controls the analog switch S1 to automatically select current or voltage output, which is convenient and avoids the problem of poor reliability.

[0025] The utility model uses a current output circuit and a voltage output driving circuit to connect current and voltage outputs together at the same time, and output switching is achieved: when voltage is output, current output is zero, which has no effect on voltage output; when current is output, voltage output is zero, and the values ​​of resistors R12, R13, and R10 are relatively large, and the effect on current output can be ignored. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 This is a high-precision current and voltage output switchable circuit diagram of an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation on the utility model and its application or use. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps described in these embodiments do not limit the scope of the utility model. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0031] In the description of the present utility model, it needs to be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present utility model and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present utility model; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0032] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" may include both "above" and "below". The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0033] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the utility model.

[0034] See also Figure 1 , the utility model provides a technical solution:

[0035] A high-precision current and voltage output switchable circuit, comprising:

[0036] A voltage follower, used to connect to the Vin terminal;

[0037] An analog switch S1 is connected to the voltage follower, and the analog switch S1 is connected to a current output circuit and a voltage output drive circuit;

[0038] The current output circuit is used for current output, and the voltage output driving circuit is used for voltage output. The outputs of the current output circuit and the voltage output driving circuit are connected together and connected to the Vout terminal.

[0039] The analog switch S1 is controlled by the MCU to control the MCU to output analog voltage or current, so as to select the analog switch S1 and the voltage output driving circuit or the current output circuit to realize the path.

[0040] In a specific embodiment, op amp is short for operational amplifier, such as Figure 1 As shown, in the op amps U1A, U1B, U1C and U1D, "+" represents the non-inverting input terminal, and "-" represents the inverting input terminal. In the transistors Q1, Q3 and Q5, "1" is the B pole representing the base, "2" is the E pole representing the emitter, and "3" is the C pole representing the collector.

[0041] In a specific embodiment, if Figure 1 As shown, diodes D1 and D2 are used to control the operating voltage of the amplifier to be slightly lower than the power supply voltage of the amplifier to avoid full-scale distortion of the amplifier, and D3 is used to prevent output reverse connection protection.

[0042] In a specific embodiment, if Figure 1 As shown, operational amplifiers U1B, U1A, transistors Q3, Q1, resistors R1-R5, R8, etc. form a current output circuit. When the current is output, the analog switch connects the Vin segment to the positive input of U1B (i.e., the in-phase input terminal, serial number is 10). The amplification factor of transistor Q3 is much greater than the base input current, and the transistor base current is ignored in the calculation.

[0043]

[0044] Where, Iout is the output current value, VDD is the power supply voltage, i1 is the current passing through resistor R1, i2 is the current passing through resistor R2,

[0045] U1D and Q5 form a voltage output drive circuit. When the voltage is output, the analog switch connects Vin to the positive input of U1D. U1B, U1A, Q3, Q1, R1-R5, R8, etc. form a current output circuit. When the current is output, the analog switch connects Vin to the positive input of U1B. Diodes D1 and D2 are used to control the operating voltage of the amplifier to be slightly lower than the power supply voltage of the amplifier to avoid full-scale distortion of the amplifier, and D3 prevents output reverse connection protection.

[0046] In a specific embodiment, if Figure 1 As shown, the current and voltage outputs are connected together at the same time, and the output switching is realized: when the voltage is output, the current output is zero, and there is no effect on the voltage output. When the current is output, the voltage output is zero. The values ​​of resistors R12, R13, and R10 are relatively large, and the effect on the current output can be ignored.

[0047] In a specific embodiment, if Figure 1 As shown, resistors R4 and R3 are used to limit the base current of the transistor, so that the transistor is in an amplified state to prevent saturation distortion. Resistors R1, R2, and R8 are used for input sampling of the op amp to control the amplification ratio. The op amp U1C is used to form a voltage follower for input signal buffering, increasing input impedance, and increasing output load capacity. Resistor R5 is used as a pull-down resistor for Vin input voltage clamping.

[0048] In a specific embodiment, if Figure 1 As shown, the output voltage of the circuit is: 0-5V, and the output current is 4-20mA. The output voltage / current of the circuit is adjusted by adjusting the Vin output voltage. The output of Vin voltage is realized by the front-end digital-to-analog conversion IC. The MCU outputs the digital signal through the SPI bus, and the analog signal is output after the digital-to-analog conversion IC. At the same time, the Vout and Iout of the product are measured by an external 5.5-digit multimeter to calibrate the starting point and maximum value of the current / voltage. At the same time, the relationship table between the analog-to-digital IC digital input and the corresponding voltage / current input of the circuit is written into the flash for later call and output.

[0049] In a specific embodiment, if Figure 1 As shown, the analog switch S1 is controlled by the MCU, and the menu options are used to control the high and low level output of the MCU, which is used to select the analog voltage / current output line, and is mainly used to provide the occasion where the sensor needs analog output. The analog acquisition signal terminal of the conventional PLC is connected.

[0050] The present utility model, the undescribed parts are prior art.

[0051] The above are only preferred specific implementation methods of the utility model, but the protection scope of the utility model is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the utility model, who makes equivalent replacements or changes based on the technical scheme and utility model concept of the utility model, should be covered by the protection scope of the utility model.

Claims

1. A high-precision current and voltage output switchable circuit, characterized in that: include: A voltage follower, used to connect to the Vin terminal; An analog switch S1 is connected to the voltage follower, and the analog switch S1 is connected to a current output circuit and a voltage output drive circuit; The current output circuit is used for current output, and the voltage output driving circuit is used for voltage output. The outputs of the current output circuit and the voltage output driving circuit are connected together and connected to the Vout terminal. The analog switch S1 is controlled by the MCU to control the MCU to output analog voltage or current, so as to select the analog switch S1 and the voltage output driving circuit or the current output circuit to realize the path.

2. A high-precision current and voltage output switchable circuit according to claim 1, characterized in that: The voltage follower is based on op amp U1C.

3. The high-precision current and voltage output switchable circuit according to claim 1, characterized in that: The current output circuit includes an operational amplifier U1B, a transistor Q3, an operational amplifier U1A and a transistor Q1 which are connected in sequence.

4. A high-precision current and voltage output switchable circuit according to claim 3, characterized in that: The pull-down resistor R5 is connected between the analog switch S1 and the operational amplifier U1B to clamp the input voltage of the Vin terminal; A resistor R4 is connected between U1B and transistor Q3 to limit the base current of transistor Q3; A resistor R3 for limiting the base current of the transistor Q1 is connected between the operational amplifier U1A and the transistor Q1; Resistor R1 is connected to transistor Q1, resistor R2 is connected to operational amplifier U1A and transistor Q3, resistor R8 is connected to transistor Q3, and resistor R1, resistor R2 and resistor R8 are used for input sampling of operational amplifier U1A to control the amplification ratio.

5. A high-precision current and voltage output switchable circuit according to claim 4, characterized in that: The resistors R1 and R2 are connected with diodes D1 and D2 for avoiding full-scale distortion of the amplifier, and the transistor Q3 is connected with a diode D3 for preventing output reverse connection protection.

6. The high-precision current and voltage output switchable circuit according to claim 1, characterized in that: The voltage output drive circuit includes an operational amplifier U1D and a transistor Q5 connected in sequence.

7. A high-precision current and voltage output switchable circuit according to claim 6, characterized in that: The pull-down resistor R11 is connected between the analog switch S1 and the operational amplifier U1D and is used to clamp the input voltage of the Vin terminal.

8. The high-precision current and voltage output switchable circuit according to claim 6, characterized in that: The transistor Q5 is connected to the resistors R12 and R13 for input sampling of the operational amplifier U1D, controlling the amplification ratio, and connecting the resistor R10.

9. The high-precision current and voltage output switchable circuit according to claim 1, characterized in that: The Vout terminal has a capacitor C1 and a diode D4 connected to ground.

10. The high-precision current and voltage output switchable circuit according to claim 9, characterized in that: A fuse F1 is connected between the capacitor C1 and the diode D4.

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