Temperature sampling circuit capable of reducing interference

Abstract

The utility model discloses a temperature sampling circuit capable of reducing interference, which comprises a thermistor close to a heating source and used for temperature detection, two ends of the thermistor are respectively connected with a group of RC low-pass filter circuits, and each group of RC low-pass filter circuits is provided with a group of common-mode filter circuits. And the two groups of RC low-pass filter circuits share one group of common-mode filter circuit. According to the utility model, the two ends of the thermistor are respectively connected with a group of RC low-pass filter circuits, the two groups of RC low-pass filter circuits can effectively filter differential-mode interference generated on two connecting wires of the thermistor, and the common-mode filter circuit shared by the RC low-pass filter circuits can filter common-mode interference. Finally, the sampling signal transmitted to the MCU is clean and stable, so that the temperature sampling precision is improved, and the working stability of the power supply is enhanced; the number of used elements is limited, the layout is simple, the internal space of the power supply is hardly occupied, and the design cost and the manufacturing cost are reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to temperature sampling technical field more specifically, is related to a temperature sampling circuit of reducing interference. BACKGROUND

[0002] In the electronic product with temperature sampling of thermistor, the position of thermistor generally will be placed close to heat source, and the MCU for processing data will be away from heat source, which leads to that the signal wire connected to thermistor is longer, the longer signal wire will cross or parallel with other wires, the capacitance coupling between lines, electromagnetic interaction and mutual coupling crosstalk, cause temperature sampling data inaccurate.

[0003] To solve the above problems, generally all through hardware to temperature sampling signal does RC low pass filter or through software does digital filter, but for relatively strong interference, these measures cannot completely solve. UTILITY MODEL CONTENT

[0004] In order to overcome the signal wire connected to thermistor of MCU for processing data is longer, is easily interfered, causes temperature sampling data inaccurate, present through hardware to temperature sampling signal does RC low pass filter or through software does digital filter, but for relatively strong interference, these measures cannot completely solve the problem, the utility model provides a temperature sampling circuit of reducing interference.

[0005] The utility model technical scheme is as follows:

[0006] A temperature sampling circuit of reducing interference, including the thermistor for temperature detection close to heat source, both ends of the thermistor are connected to a group of RC low pass filter circuit, a group of common mode filter circuit is equipped in each RC low pass filter circuit, and a group of common mode filter circuit is shared by two groups of RC low pass filter circuit.

[0007] According to the utility model of above -mentioned scheme, the common mode filter circuit includes first capacitor and second capacitor, the first capacitor and the second capacitor are arranged at both ends of the thermistor respectively, and the first capacitor is grounded, and the second capacitor is grounded.

[0008] According to the utility model of above -mentioned scheme, the RC low pass filter circuit includes resistance, the first capacitor and the second capacitor, one end of the thermistor is connected to one end of the second capacitor, the other end of the second capacitor is grounded, the other end of the thermistor is connected to one end of the resistance, one end of the first capacitor is connected to the other end of the resistance, and the other end of the first capacitor is grounded.

[0009] The utility model discloses according to above-mentioned scheme still include power supply voltage port, power supply voltage port connects one end of thermistor, be equipped with first voltage dividing resistance between power supply voltage port and thermistor.

[0010] The utility model discloses according to above-mentioned scheme, the first end of first voltage dividing resistance connects the public end of resistance and first capacitor, and the second end of first voltage dividing resistance connects power supply voltage port.

[0011] The utility model discloses according to above-mentioned scheme still include MCU analog signal acquisition port, another end of thermistor is connected to MCU analog signal acquisition port, and be equipped with second voltage dividing resistance between MCU analog signal acquisition port and thermistor.

[0012] The utility model discloses according to above-mentioned scheme, one end of second voltage dividing resistance connects the public end of resistance, first capacitor and MCU analog signal acquisition port, and another end of second voltage dividing resistance is grounded.

[0013] The utility model discloses according to above-mentioned scheme, still be equipped with a phase shift circuit at MCU analog signal acquisition port, and the phase shift circuit includes second resistance and third capacitor, one end of second resistance connects the public end of resistance, first capacitor and second voltage dividing resistance, and another end of second resistance connects the public end of MCU analog signal acquisition port and third capacitor, and another end of third capacitor is grounded.

[0014] The utility model discloses according to above-mentioned scheme, its beneficial effect lies in, a kind of temperature sampling circuit of reducing interference of the utility model, one set of RC low pass filter circuit is connected respectively at the two ends of thermistor, and the differential mode interference generated on the two connection wires of thermistor can be effectively filtered out by the two sets of RC low pass filter circuit, and common mode interference can be filtered out by the common mode filter circuit shared by RC low pass filter circuit, finally ensure that the sampling signal clean and stable that is transmitted to MCU, to improve temperature sampling precision, strengthen the stability of power supply work;The number of elements used is limited, and the layout is simple, almost does not occupy power supply internal space, reduces design cost and manufacturing cost. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is the circuit structure schematic diagram of the utility model. DETAILED DESCRIPTION

[0016] In order to make the technical problem, technical scheme and beneficial effect that the utility model wants to solve more clearly, the following is combined with the embodiment, and the utility model is further explained in detail.

[0017] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of the present application are intended to cover the non-exclusive inclusion of the listed steps or elements. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but can optionally also include steps or units not listed, or can optionally also include other steps or units inherent to such processes, methods, products or devices. The term "arrangement" and other terms should be broadly understood, for example, it can be fixed connection, or detachable connection, or integrated; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, it can be the internal communication of two elements or the interaction relationship of two elements, unless otherwise explicitly limited. The terms "upper", "lower", "left", "right", "front", "back", "bottom" and the like indicate the orientation or position based on the orientation or position shown in the drawings, and are only for convenience of description, and cannot be understood as a limitation on the technical solution.

[0018] It should be noted that in electronic products with temperature sampling using thermistors, the position of the thermistor is generally close to the heat source, and the MCU for processing data is away from the heat source, which results in a longer signal line connected to the thermistor. Longer signal lines can cross or parallel with other lines, and the lines can be capacitively coupled, electromagnetically interacted and mutually coupled crosstalk, resulting in inaccurate temperature sampling data.

[0019] To solve the above problems, generally, RC low-pass filtering is performed on the temperature sampling signal by hardware or digital filtering is performed by software, but these measures cannot completely solve the relatively strong interference.

[0020] As shown in Figure 1 The connection line of the thermistor in the temperature sampling circuit is too long and can be affected by other signals to generate interference. The embodiment provides a temperature sampling circuit for reducing interference. A set of RC low-pass filter circuits is connected to both ends of the thermistor. The two sets of RC low-pass filter circuits can effectively filter out the differential mode interference generated on the two connection lines of the thermistor. The common mode filter circuit shared by the RC low-pass filter circuits can filter out common mode interference. Finally, the sampling signal transmitted to the MCU is clean and stable, thereby improving the temperature sampling precision and enhancing the stability of the power supply.

[0021] Specifically, the temperature sampling circuit for reducing interference includes a thermistor for temperature detection close to a heat source. A set of RC low-pass filter circuits is connected to both ends of the thermistor. A set of common mode filter circuits is arranged in each set of RC low-pass filter circuits, and the two sets of RC low-pass filter circuits share a set of common mode filter circuits.

[0022] In one embodiment, the common-mode filter circuit includes a first capacitor and a second capacitor, which are respectively disposed across the two ends of a thermistor, with the first capacitor grounded and the second capacitor grounded.

[0023] The RC low-pass filter circuit includes a resistor, a first capacitor, and a second capacitor. One end of the thermistor is connected to one end of the second capacitor, and the other end of the second capacitor is grounded. The other end of the thermistor is connected to one end of the resistor, and the other end of the resistor is connected to one end of the first capacitor, and the other end of the first capacitor is grounded.

[0024] Specifically, such as Figure 1 As shown, the +3V3 power supply from the power supply port runs from the control board to the thermistor RT1, and then from the thermistor RT1 back to the control board. The lines entering and exiting the thermistor RT1 are typically quite long. When the lines are long, they may cross or run parallel to other lines, leading to capacitive coupling, electromagnetic interactions, and crosstalk between the lines. These interferences cause ripples of varying magnitudes at the intersections of resistors R1 and R2, and resistors R3 and R4, affecting the stability of the +3V3 power supply port and the TEM_MCU temperature sampling signal from the MCU analog signal acquisition port, thus causing the sampled data to exceed the error range.

[0025] Therefore, in the temperature sampling circuit for reducing interference in this embodiment, after connecting resistor R2 and capacitor C1 and resistor R3 and capacitor C2 to the thermistor RT1 connection line near the MCU, resistor R2 and capacitor C1 + capacitor C2 form an RC low-pass filter circuit, and resistor R3 and capacitor C2 + capacitor C1 form another RC low-pass filter circuit. These two RC low-pass filter circuits can effectively filter out differential-mode interference generated on these two connection lines. Since one end of capacitor C1 and capacitor C2 is grounded, capacitor C1 and capacitor C2 can form a common-mode filter circuit to filter out common-mode interference, ultimately ensuring that the sampling signal transmitted to the MCU is clean and stable. It should be noted that the resistors are not equal to resistors R2 and R3, the first capacitor is not equal to capacitor C1, and the second capacitor is not equal to capacitor C2.

[0026] In one embodiment, the temperature sampling circuit for reducing interference further includes a power supply voltage port connected to one end of a thermistor, and a first voltage divider resistor is provided between the power supply voltage port and the thermistor. The first end of the first voltage divider resistor is connected to the common terminal of the resistor and the first capacitor, and the second end of the first voltage divider resistor is connected to the power supply voltage port.

[0027] The temperature sampling circuit for reducing interference further comprises an MCU analog signal acquisition port, the MCU analog signal acquisition port is connected to the other end of the thermistor, and a second voltage dividing resistor is arranged between the MCU analog signal acquisition port and the thermistor. One end of the second voltage dividing resistor is connected to the common end of the resistor, the first capacitor and the MCU analog signal acquisition port, and the other end of the second voltage dividing resistor is grounded.

[0028] As shown in Figure 1 , the first voltage dividing resistor is resistor R1, resistor R1 is connected in series with the thermistor RT1, and a voltage dividing circuit is formed between the power supply voltage port +3V3 and the thermistor RT1. This voltage dividing circuit divides the 3V3 power supply voltage according to the resistance ratio of resistor R1 and thermistor RT1, thereby generating a voltage signal that changes with the resistance value of thermistor RT1 at the input end of the MCU analog signal acquisition port TEM_MCU. R1 can also limit the current passing through thermistor RT1, preventing damage to the thermistor or affecting the accuracy of the measurement due to excessive current.

[0029] The second voltage dividing resistor is resistor R4, resistor R4 is connected in series with the MCU analog signal acquisition port TEM_MCU, and another voltage dividing circuit is formed between the thermistor RT1 and the ground terminal (GND). This voltage dividing circuit further adjusts the voltage signal transmitted from the thermistor RT1 to the MCU, ensuring that the MCU can receive a suitable voltage range.

[0030] In one embodiment, a phase shift circuit is further arranged at the MCU analog signal acquisition port, the phase shift circuit comprising a second resistor and a third capacitor, one end of the second resistor being connected to the common end of the resistor, the first capacitor and the second voltage dividing resistor, the other end of the second resistor being connected to the common end of the MCU analog signal acquisition port and the third capacitor, and the other end of the third capacitor being grounded.

[0031] As shown in Figure 1 , resistor R5 and capacitor C3 form a set of phase shift circuits to filter out interference ripples generated in long line transmission in front of the MCU analog signal acquisition port TEM_MCU, so that the temperature signal collected by the MCU is more pure and stable, thereby ensuring that the temperature sampling value is within the error range.

[0032] It should be understood that those skilled in the art can make improvements or changes according to the above description, and all such improvements and changes shall fall within the scope of protection of the appended claims of the present application.

[0033] The utility model discloses has been described exemplarily above in combination with the drawing, obviously the implementation of the utility model patent is not limited by above-mentioned mode, as long as the various improvements of the method concept and technical scheme of the utility model patent are adopted, or the concept and technical scheme of the utility model patent are directly applied to other occasions without improvement, all are within the protection scope of the utility model.

Claims

1. An interference-reduced temperature sampling circuit, characterized by The application relates to a temperature detection device, which comprises a thermistor close to a heat source, two groups of RC low-pass filter circuits connected to the two ends of the thermistor respectively, a group of common-mode filter circuits arranged in each of the RC low-pass filter circuits, and a group of common-mode filter circuits shared by the two groups of RC low-pass filter circuits.

2. The temperature sampling circuit of claim 1, wherein, The common-mode filter circuit comprises a first capacitor and a second capacitor, the first capacitor and the second capacitor are arranged at the two ends of the thermistor respectively, the first capacitor is grounded, and the second capacitor is grounded.

3. The temperature sampling circuit of claim 2, wherein, The RC low-pass filter circuit comprises a resistor, the first capacitor and the second capacitor, one end of the thermistor is connected to one end of the second capacitor, the other end of the second capacitor is grounded, the other end of the thermistor is connected to one end of the resistor, one end of the first capacitor is connected to the other end of the resistor, and the other end of the first capacitor is grounded.

4. The temperature sampling circuit of claim 3, wherein, The application further comprises a power supply voltage port, the power supply voltage port is connected to one end of the thermistor, and a first voltage dividing resistor is arranged between the power supply voltage port and the thermistor.

5. The temperature sampling circuit of claim 4, wherein, The first end of the first voltage dividing resistor is connected to the common end of the resistor and the first capacitor, and the second end of the first voltage dividing resistor is connected to the power supply voltage port.

6. An interference-reducing temperature sampling circuit according to claim 4 or 5, characterized in that, The application further comprises an MCU analog signal acquisition port, the MCU analog signal acquisition port is connected to the other end of the thermistor, and a second voltage dividing resistor is arranged between the MCU analog signal acquisition port and the thermistor.

7. The temperature sampling circuit of claim 6, wherein, One end of the second voltage dividing resistor is connected to the common end of the resistor, the first capacitor and the MCU analog signal acquisition port, and the other end of the second voltage dividing resistor is grounded.

8. The temperature sampling circuit of claim 7, wherein, The MCU analog signal acquisition port is further provided with a phase shift circuit, the phase shift circuit comprises a second resistor and a third capacitor, one end of the second resistor is connected to the common end of the resistor, the first capacitor and the second voltage dividing resistor, the other end of the second resistor is connected to the common end of the MCU analog signal acquisition port and the third capacitor, and the other end of the third capacitor is grounded.

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