AC-DC Load Detection Circuit Using Phase-Switched Current Sourcing
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Solution Overview
Problem
In low power devices, it is challenging to determine whether a connected load is AC-coupled or DC-coupled, leading to inefficient power consumption as devices often continue to consume power even when no load is connected, due to the lack of industry standards for connections.
Innovation Solution
A circuit that includes a driver circuit, current source, and controller to detect the presence or absence of a load by measuring voltages during sourcing and sinking phases, enabling or disabling the driver circuit based on voltage stability, and distinguishing between AC- and DC-coupled loads through voltage responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the driver circuit is kept enabled to ensure immediate response to load connections, then the reliability of signal transmission is improved, but the power consumption increases when no load is connected
Solution Approach 1:
The circuit performs preliminary detection by applying test currents and measuring voltages to determine load presence and coupling type before enabling the driver circuit. This preliminary action allows the system to avoid unnecessary power consumption while maintaining readiness to respond to actual load connections.
Solution Approach 2:
The circuit uses feedback from voltage measurements during test phases to control the driver circuit state. The controller monitors voltage responses and adjusts the driver circuit enable state accordingly, creating a feedback loop that optimizes power consumption while maintaining signal transmission reliability when needed.
2Use of energy by moving object
If the driver circuit is disabled to save power when no load is connected, then the power consumption is reduced, but the ability to detect and respond to load connections is delayed
Solution Approach 1:
The circuit performs periodic load detection at specific phases (first phase and second phase) rather than continuously monitoring. This periodic action reduces power consumption compared to continuous monitoring while still providing timely detection of load connections through structured test sequences.
Solution Approach 2:
The circuit performs preliminary detection operations at defined phases before normal operation, preparing the system to quickly respond to load connections without requiring continuous active monitoring. This preliminary preparation maintains detection capability while reducing overall power consumption.
3Measurement precision
If continuous monitoring is performed to detect load presence accurately, then the measurement precision is improved, but the power consumption increases
Solution Approach 1:
The circuit performs measurement operations periodically at specific phases rather than continuously. By concentrating measurement activities into structured test phases with defined current sourcing and sinking sequences, the circuit achieves accurate load detection while minimizing the duration and frequency of high-power measurement operations.
Solution Approach 2:
The circuit applies test currents that are sufficient to produce measurable voltage responses for accurate detection, but limits the duration and frequency of these test currents to reduce overall power consumption. The measurement action is partial in time but excessive in intensity during measurement phases, achieving good signal-to-noise ratio for detection.
Data Source
AI summary
An integrated circuit includes an output terminal and a controller having a measurement input coupled to the output terminal, a first output adapted to couple to a current source to control a first current sourced into the output terminal, and a second output adapted to couple to a current sink to control a second current from the output terminal. The controller applies control signals to the first output and the second output to selectively enable the current source and disable the current sink during a first phase of a load detection period and to disable the current source and enable the current sink during a second phase of the load detection period. The controller detects the load coupled to the output terminal if a voltage at the measurement terminal during the first phase is substantially equal to a voltage at the measurement terminal during the second phase.