NTC Temperature Sensing With Notch Filtering in Power Modules
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Solution Overview
Problem
Temperature measurements in power modules with switched semiconductors are distorted by noise voltages induced in the bond wires of NTCs, leading to inaccurate readings due to magnetic coupling, which complicates the estimation of semiconductor die temperatures.
Innovation Solution
A temperature measurement arrangement that includes a Negative Temperature Coefficient Thermistor (NTC) and a notch filter to compensate for noise voltages at the switching frequency, allowing for accurate temperature sensing by neutralizing the induced noise voltage, thereby improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the NTC is directly integrated on the substrate close to the semiconductor dies, then the thermal coupling is improved and temperature measurement accuracy is enhanced, but magnetic coupling between the power loop and NTC bond wires increases causing noise voltage induction
Solution Approach 1:
A compensation winding is introduced as an intermediary element between the NTC bond wires and the magnetic field generated by the power loop. This winding is positioned to capture the magnetic flux and generate a compensating voltage that cancels the noise voltage induced in the NTC measurement circuit, thereby maintaining close thermal coupling while reducing magnetic interference
Solution Approach 2:
The magnetic coupling that causes harmful noise voltage induction is converted into a beneficial effect by using the same magnetic field to generate a compensating voltage through the compensation winding. The noise voltage and compensation voltage are configured to be equal in magnitude but opposite in polarity, effectively canceling each other out
2Speed
If the NTC is placed close to the semiconductor dies for accurate temperature sensing, then the thermal response is improved, but the induced noise voltage amplitude increases due to stronger magnetic coupling
Solution Approach 1:
The compensation winding acts as a mediator that intercepts the magnetic flux before it can induce excessive noise voltage in the NTC circuit. By positioning the compensation winding to maximize magnetic flux capture while maintaining NTC proximity to the semiconductor die, the system achieves fast thermal response with reduced noise interference
3Measurement precision
If the NTC measurement loop is positioned to capture magnetic flux for compensation, then noise voltage compensation is improved, but the loop area increases causing more noise induction
Solution Approach 1:
The compensation winding is designed with specific local characteristics: it is positioned to capture magnetic flux in the region where the power loop generates the strongest field, while the NTC measurement loop itself is minimized in area. The compensation winding's turn density and positioning are optimized locally to maximize compensation effectiveness without requiring a large overall loop area
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 notch filter effectively reduces noise interference, enabling precise temperature measurements even in close proximity to switched power semiconductors, maintaining accuracy while minimizing the impact of induced noise voltages.
Implementation Method 1
a sensing circuit including a Negative Temperature Coefficient Thermistor (NTC) for sensing a temperature
Implementation Method 2
the bond wires from the solder points of the NTC to the terminals of the NTC form a loop through which flows a magnetic field that changes with time and induces the noise voltage
Implementation Method 3
a filter for compensating the induced noise voltage at a filter frequency
Data Source
Figure 1~2
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Figure 5~6
AI summary
The invention relates to a temperature measurement arrangement (100) for measuring a temperature in a noise voltage-inducing environment comprising a sensing circuit (150) including a Negative Temperature Coefficient Thermistor (NTC) (102) for sensing a temperature and a filter (120) for compensating the induced noise voltage at a filter frequency.