Inductor Current Simulation Circuit for DC/DC Converters
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Solution Overview
Problem
Existing DC/DC converter systems face challenges in accurately measuring inductor current due to low DC resistance, which requires complex tuning of RC networks and is prone to errors from parasitic capacitance and temperature changes, making it difficult to provide reliable current feedback for control.
Innovation Solution
The implementation of inductor current simulation circuitry that uses a capacitor to simulate the current through the inductor by generating a voltage signal proportional to the inductor current, with error correction mechanisms to ensure accurate feedback without relying on tuned RC components, allowing for a wide range of inductors to be used.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DC resistance current sensing with RC network is used to measure inductor current, then current feedback can be provided for controlling the DC/DC converter, but the RC network requires complex tuning based on inductor characteristics and is prone to errors from parasitic capacitance and temperature changes
Solution Approach 1:
The patent introduces an intermediary RC network that couples the inductor to the error amplifier, where the RC time constant is specifically designed to match the inductor's L/R time constant. This intermediary network transforms the inductor current information into a voltage signal that can be directly compared by the error amplifier, eliminating the need for complex tuning while maintaining measurement accuracy across different inductor characteristics.
Solution Approach 2:
The patent changes the measurement approach by transforming the current measurement problem into a voltage comparison problem. By using the RC network to convert inductor current into a proportional voltage signal and comparing it with a reference voltage in the error amplifier, the system achieves accurate current feedback without requiring direct current sensing, thereby simplifying the overall device complexity.
2Loss of energy
If low DCR inductors are used to improve efficiency and reduce power dissipation, then less power is dissipated as heat, but current measurement through the inductor becomes more difficult
Solution Approach 1:
The RC network serves as an intermediary that couples the low-DCR inductor to the error amplifier, enabling current measurement without relying on the inductor's DC resistance. The RC time constant matching ensures that the voltage across the capacitor accurately reflects the inductor current, allowing precise measurement even when the inductor has very low DCR for high efficiency.
Solution Approach 2:
The patent replaces direct electrical current measurement (which becomes difficult with low DCR) with a voltage-based measurement system. The RC network transforms the current information into a voltage signal that can be easily measured and compared by the error amplifier, substituting the difficult current sensing task with a simpler voltage comparison task.
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 provides a reliable and accurate current feedback signal for controlling the power supply, reducing the need for complex tuning and improving the system's ability to handle variations in inductor characteristics, ensuring efficient power delivery to the load.
Implementation Method 1
a capacitor to simulate the current through the inductor by generating a voltage signal proportional to the inductor current
Data Source
AI summary
One embodiment described herein provides a circuit to approximate the inductor current of a power supply that includes a capacitor; charge/discharge circuitry configured to charge the capacitor with a voltage that is proportional to an input voltage rail of the power supply, and discharge the capacitor with a voltage that is proportional to the output voltage of the power supply; and error correction circuitry is configured to adjust the voltage that is proportional to the input voltage rail and the voltage that is proportional to the output voltage based on an instantaneous current of the inductor; and wherein the voltage on the capacitor is proportional to a current associated with the inductor.