PTC Heater Temperature Sensing via Capacitance Under PWM Drive
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Solution Overview
Problem
Existing methods for determining the temperature of a PTC heater fail to accurately measure and control the temperature of the PTC heater due to the high cost and thermal inertia of the PTC heater, which can be damaged. In addition, the heated cabin air can harm the passengers. To avoid this, the PTC heaters are usually controlled by measuring or calculating the actual temperature of the PTC heater. By measuring the actual temperature of the PTC heater, temperature sensors are usually used. The temperature sensors are usually used. The temperature sensors are disadvantageously expensive and have a certain thermal inertia. By calculating the actual temperature of the PTC heater, temperature sensors are usually used. The temperature sensors are disadvantageously expensive and have a certain thermal inertia.
Innovation Solution
The method involves using the temperature-dependent permittivity of the PTC elements of the PTC heater to calculate the temperature of the PTC heater by applying a pulse-width modulated input voltage to the PTC heater and measuring the capacitance of the PTC elements to determine the temperature of the PTC heater through, capacitance of the PTC elements using the capacitance of the PTC elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature sensors are used to measure the actual temperature of the PTC heater, then the temperature measurement is direct and reliable, but the cost is high and the thermal inertia is significant
Solution Approach 1:
The patent replaces the mechanical/physical temperature sensor system with an electrical measurement system. Instead of using contact式 temperature sensors that have thermal inertia and high cost, the invention uses the electrical resistance characteristic of the PTC element itself to determine temperature, substituting a complex sensing system with a simple electrical measurement approach
Solution Approach 2:
The PTC element serves dual functions: it acts as both the heating element and the temperature sensing element. The temperature-dependent electrical resistance of the PTC element is used to determine its own temperature without requiring external sensors, making the system self-measuring and eliminating the need for separate temperature sensing components
2Device complexity
If the resistance-temperature characteristic curve is used to calculate the actual temperature, then no additional sensors are needed, but the measurement precision is low due to the flat characteristic curve in the relevant range
Solution Approach 1:
The patent applies periodic pulse-width modulated input voltage to the PTC heater and measures the transient current response. By analyzing the periodic charging and discharging behavior of the PTC element's capacitance during voltage pulses, the system extracts temperature information from the dynamic response rather than relying on static resistance measurements, significantly improving precision
Solution Approach 2:
The invention changes the measurement parameter from static electrical resistance to dynamic capacitance characteristics. By measuring how the PTC element's capacitance responds to periodic voltage changes and how this response varies with temperature, the system achieves high-precision temperature measurement even in the flat resistance-temperature range where traditional methods fail
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
Achieves efficient, cost-effective, and environmentally friendly simultaneous removal of Hg0 from flue gas and oxidized mercury in waste liquid, avoiding secondary pollution and reducing operational costs.
Implementation Method 1
the temperature-dependent permittivity of the PTC elements of the PTC heater to calculate the temperature of the PTC elements
Data Source
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Figure 3~4
AI summary
The invention relates to a method (1) for determining a current temperature (T) of a PTC heater (2) having at least one PTC element (3) during operation of the PTC heater (2) by means of a control unit (4). A capacitance (C) of the PTC element (3) and therefrom a capacitance-determined value of the current temperature (T) of the PTC element (3) are determined from measured characteristic values of the PTC element (3). The invention also relates to the PTC heater (2) with at least one PTC element (3) and a control unit (4) for carrying out the method (1).