USB Pull-Up Resistor Control for Low-Power Modes

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Solution Overview

Problem

The high power consumption by the pull-up resistor in USB interfaces of electronic devices fails to meet the power-saving requirements of electronic products.

Innovation Solution

A universal serial bus device with a decision circuit and control circuit that selectively removes the resistor based on the device's state, using a removing signal to avoid unnecessary power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the pull-up resistor is kept connected in the USB interface, then the USB communication function is maintained, but the power consumption increases significantly

Engineering Contradiction:

ImproveUSB communication functionVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent implements dynamic control of the pull-up resistor by using a control circuit to selectively connect or disconnect the resistor based on the USB device's operational state. When the USB device is in a low-power mode or not in use, the control circuit disconnects the resistor to save power. When USB communication is needed, the resistor is connected to enable proper signal level detection. This dynamic adjustment resolves the contradiction between maintaining USB functionality and reducing power consumption.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the electrical state parameter of the pull-up resistor from a constant connected state to a variable state based on operational requirements. By controlling the resistance value (from connected to disconnected) according to different USB operational modes, the system achieves both reliable USB communication when needed and minimal power consumption when not in use.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If the resistor is removed to save power, then the power consumption is reduced, but the USB interface functionality is compromised

Engineering Contradiction:

Improvepower consumptionVSAvoidUSB interface functionality

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The control circuit dynamically adjusts the presence of the pull-up resistor based on real-time detection of USB operational states. The system transitions between connected and disconnected states of the resistor according to whether USB communication is active, ensuring functionality is maintained when needed while achieving power savings when not in use.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent employs periodic monitoring of USB interface states and correspondingly periodic connection/disconnection of the pull-up resistor. The control circuit continuously checks USB activity and adjusts the resistor connection status in response, creating a rhythmic pattern of connection that matches USB usage patterns and achieves both power efficiency and functional reliability.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS20250321914A1Universal serial bus device and control method thereof

Publication Date: 2025.10.16 REALTEK SEMICON CORP

AI summary

A universal serial bus device includes a resistor, a decision circuit, and a control circuit. The resistor is configured to receive a power supply voltage selectively. The decision circuit is configured to determine whether to remove the resistor based on at least one state of the universal serial bus device. If the decision circuit determines to remove the resistor based on the at least one state of the universal serial bus device, the decision circuit generates a removing signal. The control circuit is configured to remove the resistor based on the removing signal.