Inductor Current Reconstruction Circuit Using Switching Current Sampling
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Solution Overview
Problem
In power electronics, real-time detection of inductor current is crucial but challenging due to space and integration limitations, especially in switched-mode power supplies where direct output current detection may not be feasible.
Innovation Solution
The proposed solution involves an inductor current reconstruction circuit that uses a switching current sampling circuit and an inductor current generating circuit to reconstruct the inductor current waveform in a complete switching cycle by sampling currents through main power and rectifier transistors, and utilizing inductor voltage signals for accurate tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct output current detection is used, then measurement precision is improved, but device complexity and space requirements increase
Solution Approach 1:
The patent uses an intermediary approach by detecting switching currents through transistors as mediators to infer the inductor current. Instead of directly measuring the inductor current, the system measures the currents through the main power transistor and rectifier transistor, which are easily accessible intermediaries that provide information about the inductor current state without requiring direct contact with the inductor itself.
Solution Approach 2:
The patent creates a copied representation of the inductor current waveform by reconstructing it from switching current samples. The control circuit generates a reconstructed inductor current waveform based on the detected switching currents during ON and OFF states, providing a copy of the original current information that can be used for control purposes without requiring direct measurement of the inductor current.
2Reliability
If inductor current is not detected, then device complexity is reduced, but reliability deteriorates due to inability to prevent transistor damage
Solution Approach 1:
The system uses the transistors' own switching characteristics and inherent current paths to provide self-service for current detection. The main power transistor and rectifier transistor naturally conduct currents that can be measured during their switching operations, and these self-generated current signals are used to monitor and protect the system without requiring external sensing components.
Solution Approach 2:
The patent implements feedback by continuously monitoring the switching currents through the transistors and using this information to control the switching power supply operation. The control circuit receives feedback from the detected switching currents and adjusts the switching timing to prevent overcurrent conditions that could damage the transistors, creating a closed-loop protection mechanism.
Data Source
AI summary
An inductor current reconstruction circuit of a power converter can include: a switching current sampling circuit configured to acquire at least one of a current flowing through a main power transistor and a current flowing through a rectifier transistor to generate a switching current sampling signal; an inductor current generating circuit configured to generate a reconstruction signal representing an inductor current in one complete switching cycle; and where the reconstruction signal comprises the switching current sampling signal and a current analog signal generated according to the switching current sampling signal and an inductor voltage signal representing a voltage across an inductor in the power converter.