Choke Current Sensing Circuit With NTC Feedback for Bidirectional Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current current measurement methods through chokes in power electronic systems, such as DC-DC converters, face limitations in accuracy due to high tolerance and temperature dependence of copper resistance, and are unable to accurately measure bidirectional currents without additional circuitry and temperature compensation issues.
Innovation Solution
A device comprising an integrator circuit and an amplifier circuit with an NTC resistor in the feedback path, decoupled from offset voltage generation, allows for accurate measurement of bidirectional currents while maintaining temperature compensation using a reference voltage source and filter capacitors to maintain constant amplification over temperature and frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bidirectional current measurement is enabled by injecting a bias offset voltage, then the measurement range is expanded for negative currents, but the current value cannot be accurately derived due to temperature-dependent NTC resistor changes
Solution Approach 1:
The second NTC resistor serves as a compensating intermediary that counteracts the temperature-dependent changes in the bias offset voltage, allowing the measurement range to be expanded while maintaining measurement accuracy through temperature compensation
Solution Approach 2:
The second NTC resistor is positioned in the feedback path of the amplifier circuit, creating a temperature compensation feedback mechanism that automatically adjusts to counteract temperature-dependent offset voltage changes, thereby maintaining accurate current measurement across the expanded bidirectional range
2Measurement precision
If the NTC resistor is connected in the feedback path of the amplifier circuit, then temperature compensation is achieved without affecting offset voltage, but additional circuit complexity is introduced
Solution Approach 1:
The second NTC resistor is integrated into the existing feedback path of the amplifier circuit, merging the temperature compensation function with the existing circuit architecture rather than adding a completely separate compensation circuit, thereby limiting the increase in overall circuit complexity
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
Enables precise and temperature-stable measurement of bidirectional currents through chokes, avoiding interference and maintaining a constant transfer function across the frequency range, thus improving measurement accuracy and range without the need for bipolar supply voltage.
Implementation Method 1
Temperature compensation can be achieved using an NTC resistor connected in parallel with the capacitor of the integrator circuit. The temperature-dependent gain of the sensor circuit is varied so that it counteracts the temperature coefficient of the copper resistance of the choke
Implementation Method 2
The current through the choke is measured indirectly by recording the voltage drop across the choke and continuously integrating it. For this purpose, an integrator circuit is used
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a device (200) for measuring a current through a choke (130) of a voltage converter (100) comprising an integrator circuit (140), an amplifier circuit and an NTC resistor (160). The amplifier circuit comprises an inverting and a non-inverting amplifier input connection (152, 154) and an amplifier output connection (156). The non-inverting amplifier input connection (154) is supplied with an amplifier input signal according to an integrator output signal. A voltage signal characterising the current through the choke (130) is applied at the amplifier output connection (156) of the amplifier circuit. The NTC resistor (160) is arranged in the feedback path of the amplifier circuit between the inverting amplifier input connection (152) and the amplifier output connection (156).