A control device based on a sensitive resistance

Abstract

The utility model discloses a control device based on sensitive resistance, including power chip, sensitive resistance, first resistance, PNP triode and voltage reference chip, and power chip provides power supply for the sampling circuit that sensitive resistance and first resistance are in series, voltage reference chip is provided with control end and diode circuit, and voltage reference chip is configured as when the voltage of control end reaches the voltage threshold value of prearrangement, and the diode circuit is turned on, the base of triode is grounded through diode circuit, and the intermediate connecting point of sensitive resistance and first resistance is connected with control end, the emitter of triode is connected with positive power voltage, and positive power voltage also is grounded through diode circuit, when the resistance of sensitive resistance reduces to the threshold value of prearrangement, and the on-off state of diode circuit switches, to pull down the base voltage of triode, and then make triode switch from cut-off state to conducting state. The utility model gives consideration to control precision and implementation cost.

Description

Technical Field

[0001] This utility model relates to the field of electronic control, and in particular to a control device based on a sensitive resistor. Background Technology

[0002] With the development of electronic technology, various control devices based on sensitive resistors are widely used in industrial control, home appliances and other fields. These devices typically utilize the characteristic that the resistance of a sensitive resistor changes with environmental parameters (such as temperature, light, pressure, magnetic field, etc.) to monitor and control specific parameters.

[0003] Taking temperature control as an example, there are many circuit solutions, among which thermistor-based temperature control circuits are the most common due to their low cost, simple circuitry, and wide application. Currently, thermistor-based control circuits are mainly divided into the following categories: Figure 1 The software solution using a microprocessor shown, and such as Figure 2 The hardware scheme shown uses a comparator.

[0004] Among them, the control scheme using a microprocessor, Figure 1 The temperature probe T1 and resistor R4 shown form the sampling circuit. U1 is a high-precision power supply chip that provides high-precision voltage to the sampling circuit and also serves as the sampling reference for the microprocessor M1. This software control scheme is costly due to the use of a microprocessor, and the sampling accuracy is affected by the microprocessor's sampling resolution.

[0005] In control schemes employing comparators, Figure 2 The temperature probe T1 and resistor R4 shown also form a sampling circuit, and U1, as a high-precision power supply chip, provides high-precision voltage to the sampling circuit. Figure 2 The circuit shown uses Zener diode Z1 to provide a reference voltage for comparison, but its voltage regulation accuracy is poor. Figure 3 The circuit shown uses a high-precision power supply reference U7, which provides very high control accuracy, but also significantly increases its cost.

[0006] The above background information is provided only to aid in understanding the concept and technical solution of this application. It does not necessarily belong to the prior art of this application, nor does it necessarily provide technical guidance. In the absence of clear evidence that the above information was disclosed before the filing date of this application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Utility Model Content

[0007] The purpose of this invention is to provide a control scheme that uses a voltage reference chip to replace the microprocessor and comparator. When the resistance value of the sensitive resistor changes to the monitoring standard, the control device drives the actuator.

[0008] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0009] A control device based on a sensitive resistor includes a power supply chip, a sensitive resistor, and a first resistor. The sensitive resistor and the first resistor are connected in series to form a sampling circuit, and the power supply chip provides a power supply voltage to the sampling circuit. Further, the control device also includes a PNP transistor and a voltage reference chip. The voltage reference chip is configured with a control terminal and a diode circuit. The voltage reference chip is configured to conduct the diode circuit when the voltage at the control terminal reaches a preset voltage threshold.

[0010] The base of the PNP transistor is grounded through the diode circuit of the voltage reference chip, and the midpoint between the sensitive resistor and the first resistor is connected to the control terminal of the voltage reference chip.

[0011] The emitter of the PNP transistor is connected to the positive power supply voltage, which is also grounded through the diode circuit of the voltage reference chip.

[0012] When the resistance of the sensitive resistor decreases to a preset threshold, the on / off state of the diode circuit of the voltage reference chip is switched to lower the base voltage of the PNP transistor, thereby switching the PNP transistor from the off state to the on state.

[0013] Furthermore, in accordance with any or a combination of the aforementioned technical solutions, the control device based on a sensitive resistor provided by this utility model further includes a second resistor and a third resistor, wherein the positive power supply voltage is connected to the diode circuit of the voltage reference chip through the second resistor;

[0014] The base of the PNP transistor is connected to the diode circuit of the voltage reference chip through the third resistor.

[0015] Furthermore, following any one or a combination of the aforementioned technical solutions, the positive terminal of the diode circuit in the voltage reference chip is grounded.

[0016] Furthermore, following any one or a combination of the aforementioned technical solutions, the collector of the PNP transistor is configured to be connected to the actuator.

[0017] Furthermore, following any one or a combination of the aforementioned technical solutions, the actuator is a solenoid valve or a relay.

[0018] Furthermore, following any one or a combination of the aforementioned technical solutions, the input terminal of the power chip is connected to the positive power supply voltage.

[0019] Furthermore, in accordance with any one or a combination of the aforementioned technical solutions, the first resistor is a potentiometer or rheostat with adjustable resistance.

[0020] Furthermore, in accordance with any or a combination of the aforementioned technical solutions, the sensitive resistor is a thermistor, photoresistor, varistor, or magnetoresistive resistor.

[0021] Furthermore, following any or a combination of the aforementioned technical solutions, the power chip, the sensitive resistor, and the first resistor are connected in sequence and then grounded.

[0022] Furthermore, following any or a combination of the aforementioned technical solutions, the power chip, the first resistor, and the sensitive resistor are connected in sequence and then grounded.

[0023] The beneficial effects of the technical solution provided by this utility model are as follows:

[0024] a. Using a voltage reference chip as the comparison reference simplifies the circuit structure, reduces the number of components compared to comparator circuits, and lowers the component cost compared to solutions based on microprocessors and comparators.

[0025] b. It achieves an organic combination of lower cost and higher control precision. By combining the voltage divider circuit of the sensitive resistor and the first resistor with the voltage reference chip, when the temperature / pressure / light conditions / magnetic field conditions of the measured substance change, causing the resistance value of the sensitive resistor to change, it can accurately control the conduction state of the PNP transistor, thereby achieving precise control of the actuator.

[0026] c. The voltage reference chip used (such as TL431) can achieve a voltage accuracy of 0.5% or 1%, which is much higher than the reference accuracy generated by the Zener diode solution. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of a microprocessor-based temperature control circuit in the prior art.

[0029] Figure 2 This is a schematic diagram of a comparator-based temperature control circuit in the prior art.

[0030] Figure 3This is a schematic diagram of a temperature control circuit based on a comparator and a high-precision reference source in the prior art.

[0031] Figure 4 A schematic diagram of a control circuit employing a voltage reference chip is provided as an exemplary embodiment of this utility model;

[0032] Figure 5 A schematic diagram of a control circuit employing a voltage reference chip is provided for another exemplary embodiment of this utility model. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0034] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, apparatus, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0035] While microprocessor-based control circuits offer powerful functionality, they are costly and their sampling accuracy is limited by the processor's sampling resolution, making them unsuitable for cost-sensitive or high-precision applications. Comparator-based control circuits, if using a Zener diode as the reference voltage source, suffer from poor voltage regulation accuracy, easily affected by temperature and current variations, resulting in low precision. Using a high-precision power supply as the reference increases costs, hindering large-scale application. Furthermore, comparator-based control circuits are complex, with numerous components, increasing product size and cost while reducing system reliability.

[0036] This invention aims to provide a control device based on a sensitive resistor, which uses a voltage reference chip instead of a microprocessor and comparator to achieve both guaranteed control accuracy and reduced cost. In one embodiment of this invention, the sensitive resistor on which the control device is based can be a thermistor, photoresistor, varistor, or magnetoresistive. This embodiment uses a thermistor as an example to provide a detailed description of the temperature control device based on a thermistor:

[0037] The control device includes a power supply chip U1, a sensitive resistor T1, a first resistor R7, a second resistor R9 and a third resistor R10, a PNP transistor Q3, and a voltage reference chip U4 (TL431 or CJ431 model or SiPenh H70XXA series voltage monitoring chip). The sensitive resistor T1 and the first resistor R7 are connected in series to form a sampling circuit. The input terminal of the power supply chip U1 is connected to the positive power supply voltage VCC, and the output terminal of the power supply chip U1 provides the power supply voltage for the sampling circuit. This allows the power supply chip U1 to obtain energy from the main power supply VCC of the system and convert it into a voltage level suitable for the operation of the sampling circuit, thereby improving the system's compatibility and adaptability.

[0038] The voltage reference chip U4 is equipped with a control terminal ( Figure 4 and Figure 5 The R terminal (i.e., pin 1) and the diode circuit, wherein the positive terminal of the diode circuit ( Figure 4 and Figure 5 The A terminal (pin 3) of the circuit is grounded. The voltage reference chip U4 is configured to turn on the diode circuit when the voltage at the control terminal reaches a preset voltage threshold. This connection method makes the control terminal of the voltage reference chip U4 unique in controlling the diode circuit. That is, the diode circuit can only be turned on when the voltage at the control terminal reaches the voltage threshold. Furthermore, the grounding effect is that when the diode circuit is turned on, it can effectively pull down the base voltage of the PNP transistor Q3 to near ground potential, ensuring that the transistor Q3 can reliably switch from the cutoff state to the on state.

[0039] like Figure 4 and Figure 5 As shown, the base of the PNP transistor is connected to the diode circuit of the voltage reference chip through the third resistor R10 and grounded. The midpoint between the sensitive resistor and the first resistor R7 is connected to the control terminal of the voltage reference chip.

[0040] The emitter of the PNP transistor is connected to the positive power supply voltage, which is connected to the diode circuit of the voltage reference chip and grounded through the second resistor R9. The setting of the second resistor R9 and the third resistor R10 can provide appropriate bias voltage and current limiting protection to ensure the stability of the circuit under different operating conditions.

[0041] Taking the TL431 chip as an example, it integrates a 2.5V reference power supply, typically with 1% or 0.5% accuracy. Its working principle involves comparing the voltage at pin 1 of the voltage reference chip U4 (i.e., the control voltage) with the internal 2.5V reference voltage. When the voltage at pin 1 is less than 2.5V, pin 2 of the voltage reference chip U4 is in a high-impedance state (i.e., the diode circuit is not conducting). At this time, due to the presence of the second resistor R9, the potential at pin 2 of the voltage reference chip U4 is close to VCC. When the voltage at pin 1 is greater than 2.5V, the voltage reference chip U4 will pull pin 2 low.

[0042] When the resistance of the sensitive resistor decreases to a preset threshold, the on / off state of the diode circuit of the voltage reference chip switches, thereby pulling down the base voltage of the PNP transistor and causing the PNP transistor to switch from the off state to the on state. The collector of the PNP transistor is configured to be connected to an actuator, optionally a solenoid valve or a relay; when the PNP transistor is on, the collector current can drive the actuator to work, realizing the control of external devices.

[0043] In this embodiment, the first resistor is a potentiometer or rheostat with adjustable resistance. By adjusting the resistance of the first resistor, the voltage value between the sensitive resistor and the voltage divider point of the first resistor can be changed, thereby adjusting the trigger threshold of the control device, so that the system can adapt to different application scenarios and control requirements.

[0044] First embodiment: as follows Figure 4 As shown, the power chip, sensitive resistor, and first resistor are connected to ground in sequence. The corresponding control device operates as follows:

[0045] The power supply chip obtains energy from the positive power supply voltage and outputs a stable power supply voltage to the sampling circuit. In the sampling circuit, the sensitive resistor and the first resistor form a voltage divider. When the sensitive resistor senses a change in an external physical quantity, its resistance will change accordingly.

[0046] When the resistance of the sensitive resistor decreases (for example, due to increased temperature causing a decrease in the thermistor's resistance), the voltage at the connection point between the sensitive resistor and the first resistor increases. When this voltage reaches the preset voltage threshold of the voltage reference chip, the diode circuit of the voltage reference chip conducts.

[0047] When the diode circuit is turned on, the base voltage of the PNP transistor is pulled low, causing the PNP transistor to switch from the cutoff state to the on state. After the PNP transistor is turned on, its collector current can drive the connected actuator to work, such as opening a solenoid valve or closing relay contacts, thereby realizing the control of external devices.

[0048] Second embodiment: as follows Figure 5As shown, the power chip, the first resistor, and the sensitive resistor are connected in sequence and then grounded. Unlike the first embodiment where monitoring temperature increases leading to a decrease in the thermistor resistance (or other changes in conditions causing a decrease in the sensitive resistor resistance), this embodiment monitors that when the sensitive resistor resistance increases, the voltage at the connection point between the sensitive resistor and the first resistor increases. When this voltage reaches the preset voltage threshold of the voltage reference chip, the diode circuit of the voltage reference chip conducts.

[0049] When the diode circuit is turned on, the base voltage of the PNP transistor is pulled low, causing the PNP transistor to switch from the cutoff state to the on state. After the PNP transistor is turned on, its collector current can drive the connected actuator to work, such as opening a solenoid valve or closing relay contacts, thereby realizing the control of external devices.

[0050] It is understood that the thermistor in the first and second embodiments can be replaced by a varistor, a photoresistor, or a magnetoresistor. The control process and control principle can be deduced from the thermistor embodiment, and will not be repeated here.

[0051] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0052] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A control device based on a sensitive resistor, comprising a power supply chip, a sensitive resistor, and a first resistor, wherein, The sensitive resistor and the first resistor are connected in series to form a sampling circuit, and the power chip provides a power supply voltage for the sampling circuit; the control device further includes a PNP transistor and a voltage reference chip, the voltage reference chip is configured with a control terminal and a diode circuit, and the voltage reference chip is configured to conduct the diode circuit when the voltage at the control terminal reaches a preset voltage threshold. The base of the PNP transistor is grounded through the diode circuit of the voltage reference chip, and the midpoint between the sensitive resistor and the first resistor is connected to the control terminal of the voltage reference chip. The emitter of the PNP transistor is connected to the positive power supply voltage, which is also grounded through the diode circuit of the voltage reference chip. When the resistance of the sensitive resistor decreases to a preset threshold, the on / off state of the diode circuit of the voltage reference chip is switched to lower the base voltage of the PNP transistor, thereby switching the PNP transistor from the off state to the on state.

2. The control device based on a sensitive resistor according to claim 1, characterized in that, It also includes a second resistor and a third resistor, wherein the positive power supply voltage is connected to the diode circuit of the voltage reference chip through the second resistor; The base of the PNP transistor is connected to the diode circuit of the voltage reference chip through the third resistor.

3. The control device based on a sensitive resistor according to claim 1, characterized in that, The positive terminal of the diode circuit in the voltage reference chip is grounded.

4. The control device based on a sensitive resistor according to claim 1, characterized in that, The collector of the PNP transistor is configured to be connected to the actuator.

5. The control device based on a sensitive resistor according to claim 4, characterized in that, The actuator is a solenoid valve or a relay.

6. The control device based on a sensitive resistor according to claim 1, characterized in that, The input terminal of the power chip is connected to the positive power supply voltage.

7. The control device based on a sensitive resistor according to claim 1, characterized in that, The first resistor is a potentiometer or rheostat with adjustable resistance.

8. The control device based on a sensitive resistor according to claim 1, characterized in that, The sensitive resistor is a thermistor, photoresistor, varistor, or magnetoresistive resistor.

9. The control device based on a sensitive resistor according to any one of claims 1 to 8, characterized in that, The power chip, sensitive resistor, and first resistor are connected to ground in sequence.

10. The control device based on a sensitive resistor according to any one of claims 1 to 8, characterized in that, The power chip, the first resistor, and the sensitive resistor are connected to ground in sequence.

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