Predictive Tracking for ADC Current Sensing

Solution Overview

Problem

High-resolution and high-bandwidth loop designs in digital power management products require a very high-resolution ADC and frequent updates, leading to high power consumption and complexity.

Innovation Solution

A predictive tracking scheme is implemented in a digital PWM controller, where the predicted inductor current derived from the PWM waveform is fed forward to the ADC, reducing the required conversion range and allowing only the least significant bits (LSBs) to be converted, enabling a lower frequency clock and lower power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a very high resolution ADC is used to achieve high resolution current sensing, then measurement precision is improved, but device complexity and power consumption increase

Engineering Contradiction:

Improvecurrent sensing resolutionVSAvoidADC complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The synthesizer performs preliminary action by generating a predicted current value before the ADC conversion. This predicted value represents the expected inductor current based on the PWM waveform and circuit parameters. By having this prediction ready in advance, the system only needs to measure the difference between the predicted and actual current, dramatically reducing the measurement range required by the ADC while maintaining high resolution for the actual current sensing.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If a very high resolution ADC is used to achieve high resolution current sensing, then measurement precision is improved, but power consumption increases

Engineering Contradiction:

Improvecurrent sensing resolutionVSAvoidADC power consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The synthesizer performs preliminary action by generating a predicted current value before the ADC conversion. This predicted value represents the expected inductor current based on the PWM waveform and circuit parameters. By having this prediction ready in advance, the system only needs to measure the difference between the predicted and actual current, dramatically reducing the measurement range required by the ADC while maintaining high resolution for the actual current sensing.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If many ADC updates are performed to quickly correct the synthesizer upon load steps, then productivity is improved, but use of energy increases

Engineering Contradiction:

Improveloop update speedVSAvoidADC power consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The synthesizer performs preliminary action by generating a predicted current value before the ADC conversion. This predicted value represents the expected inductor current based on the PWM waveform and circuit parameters. By having this prediction ready in advance, the system only needs to measure the difference between the predicted and actual current, dramatically reducing the measurement range required by the ADC while maintaining high resolution for the actual current sensing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by using the ADC measurement results to correct the synthesizer's predicted current value. The measured current difference is fed back to adjust the synthesizer parameters, ensuring accurate current control. This feedback mechanism allows the system to maintain high productivity by quickly correcting load steps while consuming less power due to the reduced ADC resolution requirements.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11067611B2Method for sensing inductor current across range exceeding ADC dynamic range and PWM controller system including ADC therefor

Publication Date: 2021.07.20 RENESAS ELECTRONICS AMERICA INC

AI summary

According to certain aspects, a predictive tracking scheme is provided for sampling inductor currents in a digital PWM controller used for high-bandwidth voltage regulation. In one or more embodiments, the predicted current derived from the PWM waveform is fed forward to the current sense ADC in order to reduce the required conversion range. These and other embodiments only need to convert a few of the LSB of the ADC in order to correct the largest error expected in the synthesizer.