Comparator-Based Voltage Sensing Without Op-Amp Signal Summing

Solution Overview

Problem

Conventional voltage sensing circuits for switching power converters require high-gain and high-bandwidth operational amplifiers for adding DAC output signals, leading to increased die area and substantial current consumption, necessitating a solution for improved density and reduced power consumption.

Innovation Solution

A voltage sensing circuit where the comparator includes a differential pair of transistors that adds the analog output signals from the main DAC and tracking DAC without the need for a separate operational amplifier, utilizing a current source and resistors to steer current between the transistors based on the sign of the tracking input word, allowing for equivalent signal addition without additional power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a separate operational amplifier is used to add DAC output signals, then the voltage sensing accuracy is improved, but the die area and power consumption increase significantly

Engineering Contradiction:

Improvevoltage sensing accuracyVSAvoiddie area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent merges the adder function with the comparator by integrating the DAC output addition directly into the comparator input stage. The comparator's differential pair transistors receive one input from the main DAC and another input from the tracking DAC, effectively combining the adder and comparator into a single functional block. This eliminates the need for a separate operational amplifier, significantly reducing die area while maintaining voltage sensing accuracy through the comparator's inherent high-gain differential amplification.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The comparator is designed to perform multiple functions simultaneously: it compares the feedback voltage with the reference voltage while also adding the main DAC and tracking DAC output signals. By making the comparator multi-functional, the patent eliminates the dedicated adder operational amplifier, reducing both die area and power consumption without compromising the voltage sensing accuracy that would otherwise require a separate high-gain amplifier.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If a separate operational amplifier is used to add DAC output signals, then the voltage sensing accuracy is improved, but the power consumption increases substantially

Engineering Contradiction:

Improvevoltage sensing accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by stationary object

Solution Approach 1:

The patent merges the adder function with the comparator by integrating the DAC output addition directly into the comparator input stage. The comparator's differential pair transistors receive one input from the main DAC and another input from the tracking DAC, effectively combining the adder and comparator into a single functional block. This eliminates the need for a separate operational amplifier, significantly reducing die area while maintaining voltage sensing accuracy through the comparator's inherent high-gain differential amplification.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The comparator is designed to perform multiple functions simultaneously: it compares the feedback voltage with the reference voltage while also adding the main DAC and tracking DAC output signals. By making the comparator multi-functional, the patent eliminates the dedicated adder operational amplifier, reducing both die area and power consumption without compromising the voltage sensing accuracy that would otherwise require a separate high-gain amplifier.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Speed

If a conventional adder with high-gain operational amplifier is used, then the voltage sensing speed is improved, but the device complexity increases

Engineering Contradiction:

Improvevoltage sensing speedVSAvoidcircuit complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent merges the adder function with the comparator by integrating the DAC output addition directly into the comparator input stage. The comparator's differential pair transistors receive one input from the main DAC and another input from the tracking DAC, effectively combining the adder and comparator into a single functional block. This eliminates the need for a separate operational amplifier, significantly reducing die area while maintaining voltage sensing accuracy through the comparator's inherent high-gain differential amplification.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS10281505B2Low-power and compact voltage sensing circuit

Publication Date: 2019.05.07 DIALOG SEMICONDUCTOR INC

AI summary

A voltage sensing circuit for a switching power converter includes a comparator having a comparator input stage that processes a voltage from a main DAC and a current from a tracking DAC.