Electric Heating Temperature Control Apparatus with Differential Signal Processing
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Solution Overview
Problem
Existing electric heating blankets suffer from imprecise temperature detection and lack of comprehensive safety protection, leading to potential overheating and safety hazards due to errors in temperature sensing and voltage fluctuations.
Innovation Solution
An electric heating temperature control apparatus using an AC power supply with an electric heating wire comprising a temperature sensing conductor, an insulating layer, and a heating conductor, along with a temperature detecting circuit, heating switching circuit, and safety protection circuit, which includes differential signal processing and leakage current detection to ensure precise temperature control and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If NTC layer is used for temperature detection, then localized hot spot detection is enabled, but temperature detection precision deteriorates due to plus/minus 30% error margin and temperature coefficient changes over time
Solution Approach 1:
The patent introduces a differential amplifier circuit as an intermediary to amplify the voltage difference signal from the thermocouple while suppressing common-mode voltage fluctuations. This mediator enables precise temperature detection by converting the small thermoelectric voltage into a usable signal that is insensitive to power supply variations and electromagnetic interference.
Solution Approach 2:
The patent replaces the NTC layer's resistance-based temperature sensing with a thermocouple's thermoelectric effect-based sensing. This substitution eliminates the issues of NTC layers by using the Seebeck effect, where temperature differences directly generate voltage signals that are inherently immune to power supply fluctuations and have stable characteristics over time.
2Measurement precision
If PTC conductor is used for overall temperature detection, then temperature sensing is enabled, but detection precision deteriorates due to current leakage between PTC conductor and NTC layer
Solution Approach 1:
The patent introduces a differential amplifier as an intermediary that processes the voltage difference between the thermocouple wires. This mediator rejects common-mode leakage currents and electromagnetic interference, extracting only the differential temperature signal, thereby eliminating the impact of current leakage on detection precision.
Solution Approach 2:
The patent extracts only the differential voltage signal from the thermocouple that contains temperature information, while rejecting the common-mode leakage current and electromagnetic interference. By taking out only the useful signal component, the system achieves precise temperature detection despite the presence of leakage currents in the PTC conductor.
3Power
If AC power supply is used for heating, then heating function is enabled, but temperature detection precision deteriorates due to voltage fluctuations affecting the detection circuit
Solution Approach 1:
The patent introduces a differential amplifier circuit as an intermediary between the thermocouple and the control system. This mediator amplifies the small thermoelectric voltage while suppressing common-mode voltage fluctuations from the AC power supply, enabling precise temperature detection in the presence of power supply noise and fluctuations.
Solution Approach 2:
The patent implements a feedback control system where the amplified temperature signal is continuously fed back to the control circuit, which adjusts the heating power accordingly. This feedback mechanism compensates for voltage fluctuations by maintaining stable temperature control through real-time adjustments based on the differential temperature measurement.
4Ease of operation
If existing temperature control circuit is used, then basic temperature control is achieved, but safety protection is insufficient when circuit components fail and cause continued heating
Solution Approach 1:
The patent incorporates a safety protection circuit that performs preliminary detection of abnormal conditions such as open-circuit failures in the heating element. By detecting these failures before they cause dangerous overheating, the system can preemptively shut down heating to prevent safety hazards.
Solution Approach 2:
The patent implements comprehensive feedback monitoring that continuously checks the status of heating circuit components. When feedback indicates abnormal conditions such as component failures or temperature excursions, the control system automatically adjusts or shuts down heating to maintain safe operation, providing multiple layers of safety protection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the precision of temperature detection and provides comprehensive safety protection by minimizing the impact of voltage variations and detecting abnormal conditions, thereby preventing overheating and ensuring user safety.
Implementation Method 1
a first terminal of the temperature sensing voltage dividing and sampling unit is connected to a second terminal of the temperature sensing conductor... the temperature sensing voltage dividing and sampling unit is used for converting a signal flowing through the temperature sensing conductor into a temperature voltage signal
Implementation Method 2
the insulating layer can change its resistance or result in a short circuit between the conductors when a local or overall temperature of the heating conductor changes... the safety protection circuit uses a characteristic that the insulating layer can change its resistance or result in a short circuit between the conductors
Implementation Method 3
the heating conductor is used at least for heating... the heating switching circuit is connected to the temperature detecting circuit and to the heating conductor, and is used for turning off a power supply circuit of the heating conductor
Data Source
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AI summary
An electric heating temperature control apparatus (100) is provided, which is connected with an external electric heating wire (200) including a temperature sensing conductor (210), an insulating layer (220) and a heating conductor (230), and includes a temperature detecting circuit (110) including a temperature sensing voltage dividing and sampling unit (112), an AC voltage dividing and sampling unit (111) and a differential signal processing unit (113), the AC voltage dividing and sampling unit (111) is for converting an input signal of the AC power supply into a reference voltage signal, the temperature sensing voltage dividing and sampling unit (112) is for converting a signal flowing through the temperature sensing conductor (210) into a temperature voltage signal, and the differential signal processing unit (113) is for performing a differential comparison between the two signals. An electric heating device is further provided, which includes the electric heating temperature control apparatus (100).