Maximum Input Supply Selector Circuit for Low-Leakage Power Switching

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Solution Overview

Problem

Power management integrated circuits (PMICs) face challenges in efficiently selecting the maximum input supply voltage from multiple power sources, particularly in battery-operated devices, where they need to manage power efficiently while minimizing current consumption and preventing leakage, especially when dealing with varying and noisy input voltages.

Innovation Solution

A maximum input supply selection circuit is implemented, comprising a parallel array of comparators, input supply detectors, comparator enable logic, maximum input supply selection logic, and power switches, which generates selection signals and control signals to select the highest input supply voltage, ensuring ultra-low current consumption and preventing oscillation between input supplies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a voltage regulator is used to manage power from multiple sources, then power management capability is improved, but current consumption increases

Engineering Contradiction:

Improvepower management capabilityVSAvoidcurrent consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The power management function is segmented into two independent parts: (1) a maximum input supply selector circuit that selects the highest voltage source with ultra-low current consumption, and (2) a voltage regulator that conditions the selected voltage. This segmentation allows the selector to operate passively without continuous power consumption, while the regulator only processes the selected supply.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The maximum input supply selector acts as an intermediary component between multiple power sources and the voltage regulator. It introduces selection logic that compares input voltages and routes only the maximum voltage to the regulator, preventing the regulator from continuously managing all power sources and reducing overall current consumption.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If multiple power sources are monitored continuously to select the maximum voltage, then selection accuracy is improved, but oscillation between inputs occurs

Engineering Contradiction:

Improvevoltage selection accuracyVSAvoidinput supply stability

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The selector circuit performs preliminary voltage comparison and selection before the voltage regulator operates. By pre-selecting the maximum input supply based on voltage level detection, the system establishes a stable single input to the regulator, preventing oscillation that would occur if all inputs were continuously monitored and switched.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The selection function is extracted as a separate maximum input supply selector circuit independent from the voltage regulator. This extraction allows the selector to make a definitive choice of the maximum voltage source without the regulator's control loop interfering, thereby preventing oscillation between multiple inputs.

Inventive Principle:

Principle #2Taking out (Extraction)

3Use of energy by moving object

If a simple voltage selection circuit is used, then current consumption is reduced, but noise tolerance decreases

Engineering Contradiction:

Improvecurrent consumptionVSAvoidnoise tolerance

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The maximum input supply selector incorporates feedback mechanisms where the output voltage is monitored and fed back to the selection logic. This feedback ensures that the selected supply remains stable and that noise or transient drops do not cause incorrect selection, thereby improving noise tolerance while maintaining ultra-low current consumption through passive selection.

Inventive Principle:

Principle #23Feedback

4Use of energy by moving object

If passive selection method is used to minimize current consumption, then power efficiency is improved, but leakage prevention becomes difficult

Engineering Contradiction:

Improvepower efficiencyVSAvoidleakage current

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The maximum input supply selector serves as an intermediary that actively manages the connection between power sources and the load. By using controlled switches or transmission gates in the selection circuit, it prevents leakage current from flowing through non-selected power paths while maintaining passive operation for the selected path, thus preventing leakage without sacrificing power efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11086342B1Low power high speed maximum input supply selector

Publication Date: 2021.08.10 QUALCOMM INC

AI summary

Techniques and apparatus for selecting a maximum input supply voltage from multiple input power supplies. An example maximum input supply selection circuit includes a parallel array of comparators and selection logic to select the maximum input supply voltage, supply present detectors, comparator settling logic including a warm-up delay timer to provide for comparator settling, and comparator enable logic for disabling all comparators and entering an ultra-low power mode.