Predictive Current Feedback for Switched Mode Regulators
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Solution Overview
Problem
Existing methods for sensing inductor current in switched mode regulators, such as DCR sensing and high side sensing, are complex, costly, and inefficient, particularly during load transients, due to the need for external components and high voltage differential signals, which result in inaccuracies and reduced power conversion efficiency.
Innovation Solution
A predictive current feedback system that uses a modulator to generate a PWM signal based on sensed inductor current and output voltage, predicting inductor current levels during load transients by adjusting the HOLD signal with an OFFSET to improve accuracy and reduce sampling delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DCR sensing is used to detect inductor current, then current sensing is achieved, but additional external components are required and system complexity increases
Solution Approach 1:
The patent extracts the current sensing function from external components and implements it within the regulator IC itself. The sensing resistor is integrated inside the IC, and the sensing amplifier is coupled to detect voltage across this internal resistor, eliminating the need for external sensing components while maintaining current measurement capability
Solution Approach 2:
The regulator IC is designed to perform multiple functions including current sensing, voltage regulation, and control within a single integrated device. The sensing amplifier serves dual purposes by monitoring both the voltage across the sensing resistor for current detection and providing feedback for regulation control
2Measurement precision
If high side sensing is used to detect inductor current, then current sensing is achieved, but high voltage differential signals are required and power conversion efficiency is reduced
Solution Approach 1:
The patent introduces a low-value sensing resistor as an intermediary element to convert the high-voltage current measurement problem into a low-voltage measurement problem. The sensing resistor converts inductor current into a proportional voltage signal that can be accurately measured by the sensing amplifier without requiring high voltage differential signaling
Solution Approach 2:
The patent replaces the mechanical/electrical high voltage differential sensing method with an electrical voltage measurement method. Instead of directly measuring high voltage differential signals across the inductor, the system uses voltage measurement across the sensing resistor, which is a lower voltage signal that can be measured with standard amplifier circuits
3Measurement precision
If external components are used for current sensing, then sensing is achieved, but cost increases
Solution Approach 1:
The patent combines the sensing resistor, sensing amplifier, and current sensing function into a single integrated regulator IC. This merging of components eliminates the need for separate external sensing resistors and amplifiers, reducing the total component count and lowering manufacturing costs while maintaining full current sensing capability
4Measurement precision
If sampling is used to detect inductor current, then current measurement is achieved, but sampling delays occur and accuracy during load transients is reduced
Solution Approach 1:
The patent implements continuous current monitoring through the sensing amplifier that continuously detects the voltage across the sensing resistor. This continuous measurement approach eliminates sampling delays and provides real-time current information during load transients, maintaining measurement accuracy without time losses associated with periodic sampling
Data Source
AI summary
A predictive current feedback system for a switched mode regulator including a sample and hold network for sampling voltage across a lower switch of the regulator and for providing a hold signal indicative thereof, and a predictive current feedback network which adds an offset adjustment to the hold signal based on a duration of a pulse width of a pulse control signal developed by the regulator. Sampling may be done while the lower switch is on for providing a hold value indicative of inductor current while the pulse control signal is low. The offset adjustment may be added to the hold signal in response to a transient event when the pulse signal is high. The offset may be incremental values after each of incremental time periods after a nominal time period, or may be a time-varying value. Adjustment may be made while the pulse signal is low as well.