Inductor Current Emulation Circuit for Low-Duty Ratio Sensing
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Solution Overview
Problem
Conventional inductor current sensing circuits in switching power regulators experience imprecision, particularly at low duty ratios, leading to inaccurate current sensing in multi-phase power converters, especially at high frequencies.
Innovation Solution
The proposed inductor current emulator circuit employs a sensing circuit and an emulation control circuit to generate and sample-and-hold current emulation signals, ensuring precise emulation of inductor currents by adjusting the duty ratio thresholds and using sample-and-hold techniques to balance currents across channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sensing circuits are used to sense inductor current, then the circuit structure is simple, but the measurement precision deteriorates at low duty ratios
Solution Approach 1:
The patent introduces an emulation control circuit as an intermediary between the sensing circuits and the inductor current. This circuit generates current emulation signals that replicate the inductor current waveform, allowing the system to obtain accurate current information without directly relying on the potentially inaccurate sensing signals at low duty ratios. The emulation circuit acts as a mediator that transforms the imperfect sensing data into precise current representation.
Solution Approach 2:
The patent creates a copy of the inductor current through current emulation signals. Instead of directly using the sensed current signal which may be inaccurate at low duty ratios, the system generates a copied representation of the current waveform through the emulation control circuit. This copying mechanism allows the system to work with an idealized version of the current signal that maintains accuracy across all duty ratio conditions.
2Measurement precision
If sensing circuits sense switch currents to generate current sensing signal, then the implementation is straightforward, but the measurement precision deteriorates when duty ratio is very low
Solution Approach 1:
The emulation control circuit performs preliminary actions by generating current emulation signals in advance based on the switching control signals. Instead of waiting for potentially inaccurate current sensing during low duty ratio operations, the system pre-generates accurate current representation signals that are synchronized with the switching events. This preliminary generation of current information ensures accuracy before the actual current sensing takes place.
Solution Approach 2:
The patent implements a feedback mechanism where the emulation control circuit continuously monitors the switching control signals and adjusts the current emulation signals accordingly. The system uses feedback from the switching events to maintain accurate current emulation, compensating for any deviations that occur during low duty ratio operations. This closed-loop feedback ensures sustained measurement precision across varying operating conditions.
3Reliability
If conventional current sensing is used in multi-phase power converter, then the system is easier to implement, but the reliability of current balance deteriorates at high frequencies
Solution Approach 1:
The patent applies segmentation by dividing the current sensing and emulation functions into separate modules for each phase of the multi-phase power converter. Each phase has its own sensing circuits and emulation control circuit that independently generate current emulation signals. This segmentation allows each phase to be optimized independently while maintaining overall system reliability, and enables parallel processing of current information across multiple phases at high frequencies.
Solution Approach 2:
The emulation control circuit is designed with universal functionality that can handle multiple phases and various duty ratio conditions through the same fundamental mechanism. The circuit uses common techniques such as sample-and-hold, signal generation, and synchronization that apply universally across different phases and operating conditions. This multi-functionality reduces the need for phase-specific complex circuitry while maintaining reliability across all phases.
Data Source
AI summary
An inductor current emulator circuit is for use in a switching power regulator, wherein a first and a second switches of a power stage circuit switch an inductor. The first and second switches are ON during first and a second ON-times, respectively. The inductor current emulator circuit includes: a sensing circuit sensing an ON-current of the second switch to generate a current sensing signal; and an emulation control circuit configured to, when a duty ratio of the first switch is smaller than a first duty ratio threshold, generate a first part of a current emulation signal according to the current sensing signal during the second ON-time, and sample-and-hold the current sensing signal to generate a first sample-and-hold signal at an intermediate time point of the second ON-time, and generate a second part of the current emulation signal according to the first sample-and-hold signal at a following first ON-time.