Inductor Current Reconstruction Circuit Without Transistor State Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing inductor current reconstruction designs in switched-mode power supplies face challenges such as reduced precision and inaccuracy due to voltage drops across power transistors and the need to detect ON/OFF states of transistors, leading to inaccurate current reconstruction, especially during simultaneous turn-off of upper and lower power transistors.
Innovation Solution
An inductor current reconstruction circuit that uses an AC component reconstruction module with a charge/discharge capacitor, operational amplifiers, and current-controlled current sources to charge or discharge the capacitor based on voltage differences across the inductor, generating a reconstructed signal without requiring detection of transistor states, and includes a DC component calibration module to eliminate DC offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing inductor current reconstruction designs are used, then the circuit complexity is reduced, but the measurement precision of inductor current is degraded due to voltage drops across power transistors and inaccurate detection during simultaneous turn-off
Solution Approach 1:
The patent segments the inductor current reconstruction into two independent parts: AC component reconstruction using voltage difference across the inductor, and DC component calibration using transistor state detection. This segmentation allows each part to be optimized independently, improving overall precision without proportionally increasing complexity.
Solution Approach 2:
The patent introduces a charge/discharge capacitor as an intermediary element that accumulates voltage proportional to the integral of inductor voltage difference. This intermediary converts voltage measurements into current information without requiring direct current sensing, thereby improving measurement precision while maintaining reasonable circuit complexity.
2Speed
If voltage difference across power transistors is used for current reconstruction, then the response speed is improved, but the measurement precision is degraded due to voltage drops across transistors
Solution Approach 1:
The patent extracts only the voltage difference across the inductor (V_L = V_sw - V_out) for AC component reconstruction, eliminating the harmful voltage drops across power transistors from the measurement. This extraction approach maintains fast response speed while improving accuracy by focusing only on the relevant voltage component.
Solution Approach 2:
The patent performs preliminary calibration of the DC component offset before normal operation. By pre-characterizing and compensating for voltage drops across transistors during calibration phase, the system achieves high measurement precision during actual operation without sacrificing response speed.
3Measurement precision
If transistor ON/OFF state detection is required for current reconstruction, then the measurement precision can be maintained, but the device complexity and difficulty of detection increase
Solution Approach 1:
The patent uses dynamic timing control where the DC calibration phase is activated only during specific intervals (when both transistors are off), separating the complex detection function from continuous operation. This dynamic approach maintains measurement precision while reducing detection complexity during normal operation.
Solution Approach 2:
The patent implements periodic DC calibration at specific intervals in the switching cycle rather than continuous detection. This periodic action maintains measurement precision by regularly updating calibration data while reducing the overall complexity and burden of transistor state detection during normal operation.
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
This solution enhances the precision of inductor current reconstruction by isolating it from voltage drops and transistor states, providing accurate current reconstruction without detecting transistor states and improving overall control and protection in switched-mode power supplies.
Implementation Method 1
a first operational amplifier and a current-controlled current source, a first input terminal of the first operational amplifier coupled to the first end of the inductor and receiving the voltage at the first end of the inductor, a second input terminal of the first operational amplifier receiving the voltage at the second end of the inductor... the first operational amplifier generates, based on the voltage difference between the voltages at the first and second ends of the inductor, or on the voltage difference between the voltage at the first end of the inductor and the other voltage associated with the voltage at the first end of the inductor, a corresponding control signal
Implementation Method 2
an AC component reconstruction module having a charge/discharge capacitor, the AC component reconstruction module coupled to an inductor and configured to charge or discharge the charge/discharge capacitor, based on a voltage difference between voltages at opposing ends of the inductor, or on a voltage difference between a voltage at a first end of the inductor and another voltage associated with the voltage at the first end of the inductor, a current of charging or discharging the charge/discharge capacitor proportional to the voltage difference
Data Source
AI summary
An inductor current reconstruction circuit, a controller and a switched-mode power supply are disclosed. The inductor current reconstruction circuit includes an AC component reconstruction module having a charge/discharge capacitor, which is coupled to an inductor and configured to charge or discharge the charge/discharge capacitor, based on voltage difference between voltages at opposing ends of the inductor, or on voltage difference between a voltage at one end of the inductor and another voltage associated with the voltage at the end of the inductor, at a current proportional to the voltage difference. The AC component reconstruction module outputs a reconstructed signal characterizing an AC component in a current through the inductor. Inductor current reconstruction can be achieved without detecting ON/OFF states of power transistors. This makes the precision of inductor current reconstruction immune from influence of both any voltage drop across power transistors and simultaneous turn-off of upper and lower power transistors.