PFC Inductor Current Reconstruction for Low-Pin Converter Control
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Solution Overview
Problem
Existing power factor correction (PFC) stage circuits face challenges in efficiently determining the inductor current due to signal disturbances and limitations on the number of integrated circuit (IC) pins, which affects the control and performance of the PFC stage.
Innovation Solution
The proposed power converter employs an emulation circuit that generates an emulated inductor current without directly sensing the voltage at the inductor terminal, using a voltage-to-current error amplifier, integrator, and feedforward compensating circuit to overcome the limitations of IC pins and signal disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct sensing of inductor current is used, then measurement precision is improved, but device complexity increases due to additional IC pins and sensing circuits
Solution Approach 1:
The patent creates an emulated copy of the inductor current signal through mathematical reconstruction using the relationship iL = (1/L) ∫ vL dt. Instead of directly sensing the physical inductor current, the system generates an equivalent electrical signal that replicates the current waveform characteristics, allowing the controller to operate as if direct sensing were performed without requiring additional IC pins or complex sensing hardware.
2Measurement precision
If multiple sensing signals are implemented, then measurement precision is improved, but object-affected harmful factors increase due to signal disturbances
Solution Approach 1:
The patent extracts only the essential information needed for current measurement from the voltage signal across the inductor. By using the fundamental electrical relationship and integrating the voltage signal, the system obtains accurate current information without requiring multiple separate sensing paths that would be susceptible to disturbances. This extraction approach eliminates the harmful interactions between multiple sensing circuits.
3Device complexity
If emulated current reconstruction is used, then device complexity is reduced, but measurement precision may deteriorate due to signal processing errors
Solution Approach 1:
The patent implements a feedback mechanism where the emulated current signal is continuously compared with the actual inductor current characteristics. The controller uses this feedback to adjust and refine the reconstruction process, ensuring that the emulated signal accurately represents the true current waveform. This feedback loop compensates for potential errors in the mathematical reconstruction and maintains high measurement precision while keeping the device complexity low.
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AI summary
Embodiments of a power converter are disclosed. In an embodiment, the power converter comprises a power factor correction (PFC) stage circuit, an emulation circuit and a controller. The PFC stage circuit is configured to produce an output signal on an output terminal. The PFC stage circuit includes an inductor coupled between a rectifier and the output terminal and a switch coupled to the inductor. The emulation circuit is connected to the PFC stage circuit to generate an emulated current that corresponds to current through the inductor of the PFC stage circuit. The emulated current is generated based on a voltage signal at a node between the inductor and the output terminal and a sensed current at a sense resistor connected to the rectifier. The controller is connected to the emulation circuit to receive the emulated current and generate a control signal for the switch of the PFC stage circuit based on the emulated current.