CN216050047U - Mixed connection detection circuit for residual current and temperature - Google Patents

Abstract

The utility model relates to a mixed connection detection circuit of residual current and temperature, which comprises an MCU (microprogrammed control unit), a residual current INPUT port INPUT1 and a temperature detection INPUT port INPUT2 which are arranged in parallel, a filter circuit, a field-effect tube Q1 and an ADC (analog to digital converter) sampling unit, wherein the filter circuit, the field-effect tube Q1 and the ADC sampling unit are connected with the residual current INPUT port INPUT1 and the temperature detection INPUT port INPUT2, the field-effect tube Q1 is used for switching a residual current or temperature detection mode, and the ADC sampling unit is used for collecting residual current or temperature information and uploading the residual current or temperature information to the MCU. The utility model discloses a through rational multiplexing residual current and temperature detection circuit, greatly reduced circuit complexity and hardware cost, improved system reliability simultaneously, can effectively eliminate the drawback that traditional detection means exists.

Description

Mixed connection detection circuit for residual current and temperature

Technical Field

The utility model relates to the field of electricity, in particular to a mixed connection detection circuit for residual current and temperature.

Background

The residual current and temperature mixed connection detection is mainly applied to combined type electric fire monitoring detectors. The hybrid connection means that a sensor channel of the detector can be configured into a residual current or temperature detection mode according to actual requirements so as to meet different electrical fire monitoring application scenarios.

The traditional mixed detection of residual current and temperature generally switches a residual current detection circuit and a temperature detection circuit through an analog switch or a plurality of field effect transistors, and the two detection circuits are mutually independent, so that the circuit is complex and the hardware cost is high.

SUMMERY OF THE UTILITY MODEL

Aiming at the existing defects, the utility model provides a mixed connection detection circuit of residual current and temperature.

The technical scheme adopted by the utility model for solving the technical problems is as follows: a mixed connection detection circuit of residual current and temperature comprises an MCU, a residual current INPUT port INPUT1 and a temperature detection INPUT port INPUT2 which are arranged in parallel, a filter circuit and a field effect transistor Q1 which are connected with the residual current INPUT port INPUT1 and the temperature detection INPUT port INPUT2, and an ADC sampling unit; the field-effect transistor Q1 is used for switching a residual current or temperature detection mode, one end of the field-effect transistor Q1 is connected with a power supply VCC for providing an excitation signal, the other end of the field-effect transistor Q1 is connected with a pull-up resistor R1, the pull-up resistor R1 is connected with a load resistor R2, and the other end of the load resistor R2 is grounded; the residual current INPUT port INPUT1 is connected between a pull-up resistor R1 and a load resistor R2, the temperature detection INPUT port INPUT2 is connected to the grounding end of the load resistor R2, and the ADC sampling unit takes residual current or temperature information and uploads the residual current or temperature information to the MCU.

Preferably, the filter circuit comprises a capacitor C1 and a capacitor C2 connected in parallel, a resistor R3 connected in series with a capacitor C1, and a resistor R4 connected in series with a parallel circuit formed by a capacitor C1 and a capacitor C2.

Preferably, the residual current INPUT port INPUT1 is connected with a residual current transformer, the MCU controls the model select to output a high level, the fet Q1 is disconnected, the residual current transformer is connected, the load resistor R2 converts the current signal into an ac voltage signal, and the ac voltage signal is transmitted to the ADC sampling unit through the filter circuit.

Preferably, the MCU controls the model select to output a low level, turns on the fet Q1, and the pull-up resistor R1 injects an excitation signal into the detection circuit and transmits the excitation signal to the ADC sampling unit.

Preferably, the temperature detection INPUT terminal INPUT2 is connected to a temperature sensor Rt, the MCU controls the model select to output a low level, the fet Q1 is turned on, and the temperature sensor Rt, the pull-up resistor R1, and the load resistor R2 form a resistor divider circuit.

Preferably, the temperature sensor Rt is an NTC temperature sensor.

The utility model has the beneficial effects that: the utility model discloses a through rational multiplexing residual current and temperature detection circuit, greatly reduced circuit complexity and hardware cost, improved system reliability simultaneously, can effectively eliminate the drawback that traditional detection means exists.

Drawings

FIG. 1 is a circuit diagram of an embodiment of the present invention;

FIG. 2 is a circuit diagram of an embodiment of the utility model in a residual current detection mode;

FIG. 3 is a diagram of normal state excitation and output waveforms of a residual current transformer in accordance with an embodiment of the present invention;

FIG. 4 is a diagram of excitation and output waveforms of a residual current transformer in a short-circuit state according to an embodiment of the present invention;

FIG. 5 is a diagram of excitation and output waveforms for an open circuit condition of a residual current transformer in accordance with an embodiment of the present invention;

FIG. 6 is a circuit diagram of a temperature detection mode according to an embodiment of the present invention;

FIG. 7 is a graph of excitation and output waveforms in the temperature sensing mode of an embodiment of the present invention;

Detailed Description

To more clearly illustrate the objects, technical solutions and advantages of the embodiments of the present invention, the present invention will be further described in detail with reference to the accompanying drawings and embodiments, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without inventive step, are within the scope of the present invention. In addition, directional terms used in the present invention, such as "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc., refer to directions only as shown in the attached drawings, and are used for better and clearer explanation and understanding of the present invention, and do not indicate or imply orientation which the present invention must have, and thus, should not be construed as limiting the present invention.

The embodiment of the utility model is shown in fig. 1 to 7, and the mixed connection detection circuit of residual current and temperature comprises an MCU, a residual current INPUT port INPUT1 and a temperature detection INPUT port INPUT2 which are arranged in parallel, a filter circuit and a field effect transistor Q1 which are connected with the residual current INPUT port INPUT1 and the temperature detection INPUT port INPUT2, and an ADC sampling unit; the field-effect tube Q1 is used for switching a residual current or temperature detection mode, the filter circuit, the field-effect tube Q1 and the ADC sampling unit are connected and conducted with different ports for use in different modes, circuit multiplexing is achieved, circuit complexity and hardware cost are greatly reduced, meanwhile, system reliability is improved, and defects existing in a traditional detection means can be effectively eliminated, at the moment, one end of the field-effect tube Q1 is connected with a power supply VCC for providing an excitation signal, the other end of the field-effect tube Q1 is connected with a pull-up resistor R1, the pull-up resistor R1 is connected with a load resistor R2, and the other end of the load resistor R2 is grounded; the residual current INPUT port INPUT1 is connected between the pull-up resistor R1 and the load resistor R2, the temperature detection INPUT port INPUT2 is connected with the grounding end of the load resistor R2, the ADC sampling unit takes residual current or temperature information and uploads the residual current or temperature information to the MCU, and the ADC sampling unit becomes the sampling INPUT port of the MCU. The filter circuit comprises a capacitor C1 and a capacitor C2 which are connected in parallel, a resistor R3 connected with a capacitor C1 in series, and a resistor R4 connected with a parallel circuit formed by a capacitor C1 and a capacitor C2 in series.

In a further improvement, as shown in fig. 2, when the residual current is detected, i.e. in the residual current detection mode, the residual current INPUT port INPUT1 is connected with a residual current transformer, the detection comprises two parts of residual current effective value detection and residual current transformer wiring fault detection, when the residual current effective value is detected, the MCU controls the ModelSelect to output high level, a field effect transistor Q1 is disconnected, a residual current transformer is connected, a pull-up resistor R1 is disconnected with other parts of the circuit, a residual current signal (primary current) generated by a main circuit is converted into a secondary current signal according to a certain transformation ratio through the residual current transformer, then the current signal is converted into an alternating current voltage signal through a load resistor R2, the alternating current voltage signal is filtered through a filter circuit and then transmitted to an ADC (analog to digital converter) sampling unit for sampling by the MCU, and finally the MCU obtains a residual current effective value through conversion; in order to ensure reliable operation, the MCU needs to regularly detect the wiring condition of the external residual current transformer, when the wiring fault of the residual current transformer is detected, the MCU controls the ModelSelect to output low level, the field effect transistor Q1 is conducted, the pull-up resistor R1 injects an excitation signal to the detection circuit and transmits the excitation signal to the ADC sampling unit, then the corresponding output waveform is detected at the ADC end, the three states of normal, short circuit and open circuit of the external mutual inductor can be judged, when the residual current mutual inductor is connected normally, since the secondary of the residual current transformer is a coil winding, which is equivalent to an inductor, and the inductor has the characteristic of preventing the current from suddenly changing, the output waveform is a sawtooth wave as shown in fig. 3, and it is assumed that the voltage amplitude measured when the excitation signal is added is V1, the voltage amplitude is measured to be V2 before the excitation signal is turned off, and if V1 is larger than V2 and exceeds a certain amplitude, the residual current transformer can be judged to be in a normal state; it can be known from the circuit schematic diagram that when the residual current transformer is in short circuit, the two ends of the load R2 are also internally short-circuited at the same time, the output waveform is shown in fig. 4, the voltage V1 and the voltage V2 measured under the condition are both close to OV, and the residual current transformer can be judged to be in a short-circuit state; as can be seen from the schematic circuit diagram, when the residual current transformer is disconnected, the resistor R1 and the resistor R2 form a resistor voltage divider circuit, the output waveform is as shown in fig. 5, and assuming that the excitation signal voltage is VCC, both the voltage V1 and the voltage V2 measured in this case are close to the theoretical voltage division value, i.e., VCC R2/(R1+ R2), it can be determined that the residual current transformer is in the disconnected state.

In a further improvement, as shown in fig. 6, when detecting temperature, the temperature detection INPUT terminal INPUT2 is connected to a temperature sensor Rt, the temperature sensor selects an NTC temperature sensor, including a temperature value detection method and temperature sensor wiring fault detection, when detecting temperature value, the MCU controls the model select to output low level, turns on the fet Q1, the temperature sensor Rt, the pull-up resistor R1 and the load resistor R2 form a resistor divider circuit, the INPUT waveform is as shown in fig. 7, assuming that the excitation signal voltage is VCC, Rx is a resistor formed by connecting Rt and R2 in parallel, the measured voltage amplitude before the excitation signal is turned off is V3, V3 is VCC Rx/(R1+ Rx), according to the "resistance/temperature" correspondence table of the NTC thermistor, and in combination with the calculation formula of V3, a "temperature/voltage" correspondence table has been preset in the MCU program space, and after the MCU samples output voltage, the current temperature value can be calculated; similarly, when short circuit occurs, the output voltage approaches 0V. When the circuit is disconnected, the output voltage is close to VCC R2/(R1+ R2), and the CU can judge whether the sensor wiring is short-circuited or the circuit is disconnected by detecting the amplitude of the output voltage.

It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the utility model as defined in the appended claims.

Claims (6)

1. The mixed connection detection circuit of the residual current and the temperature is characterized by comprising an MCU, a residual current INPUT port INPUT1 and a temperature detection INPUT port INPUT2 which are arranged in parallel, a filter circuit, a field effect transistor Q1 and an ADC sampling unit, wherein the filter circuit, the field effect transistor Q1 and the ADC sampling unit are connected with the residual current INPUT port INPUT1 and the temperature detection INPUT port INPUT 2; the field-effect transistor Q1 is used for switching a residual current or temperature detection mode, one end of the field-effect transistor Q1 is connected with a power supply VCC for providing an excitation signal, the other end of the field-effect transistor Q1 is connected with a pull-up resistor R1, the pull-up resistor R1 is connected with a load resistor R2, and the other end of the load resistor R2 is grounded; the residual current INPUT port INPUT1 is connected between a pull-up resistor R1 and a load resistor R2, the temperature detection INPUT port INPUT2 is connected to the grounding end of the load resistor R2, and the ADC sampling unit takes residual current or temperature information and uploads the residual current or temperature information to the MCU.

2. The mixed connection detection circuit of the residual current and the temperature as claimed in claim 1, characterized in that the filter circuit comprises a capacitor C1 and a capacitor C2 connected in parallel, a resistor R3 connected in series with a capacitor C1, and a resistor R4 connected in series with a parallel circuit formed by a capacitor C1 and a capacitor C2.

3. The residual current and temperature mixed connection detection circuit according to claim 1, wherein the residual current INPUT port INPUT1 is connected with a residual current transformer, the MCU controls the ModelSelect to output high level, the FET Q1 is disconnected, the residual current transformer is connected, the load resistor R2 converts the current signal into an AC voltage signal, and the AC voltage signal is transmitted to the ADC sampling unit through the filter circuit.

4. The mixed connection detection circuit of the residual current and the temperature as claimed in claim 3, wherein the MCU controls the ModelSelect to output a low level, the field effect transistor Q1 is turned on, and the pull-up resistor R1 injects an excitation signal into the detection circuit and transmits the excitation signal to the ADC sampling unit.

5. The mixed connection detection circuit of the residual current and the temperature according to claim 1, wherein a temperature sensor Rt is connected to the temperature detection INPUT end INPUT2, the MCU controls the Modelselect to output a low level, a field effect transistor Q1 is turned on, and the temperature sensor Rt, a pull-up resistor R1 and a load resistor R2 form a resistor voltage division circuit.

6. The mixed connection detection circuit of residual current and temperature as claimed in claim 5, wherein the temperature sensor Rt is an NTC temperature sensor.

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