Power Sensing Unit for Audio Systems Using RC Transient Detection
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Solution Overview
Problem
Existing power sensing methods in electrical systems, particularly in A/V systems, fail to accurately determine the presence or absence of main AC power, leading to unstable system conditions, delayed power-off notifications, and 'pop noise' issues due to reliance on DC voltage feedback, which is not fast enough to control audio mute circuits effectively.
Innovation Solution
A power sensing unit comprising an antenna and an analog signal processing circuit that detects the mains AC power by inducing a signal from the mains cable and converting it into a DC signal, providing a reliable indication of power presence or absence, enabling timely control signals to circuitry units, including audio amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DC voltage feedback is used to detect power status, then the system can detect power presence, but the detection is slow and causes system instability
Solution Approach 1:
The patent introduces an intermediary RC circuit connected to the secondary side DC voltage that converts the slow DC voltage change into a faster transient signal. The capacitor charges/discharges rapidly when power is applied or removed, creating a temporary voltage spike that quickly triggers the power detection circuit, thus mediating between the slow DC source and the need for fast detection
Solution Approach 2:
The patent uses the RC circuit to create a preliminary transient voltage signal before the main DC voltage stabilizes. This preliminary action (the voltage spike) occurs immediately when power is applied or removed, allowing the system to detect power status changes before the slow DC voltage transitions complete, thus enabling faster response
2Reliability
If DC voltage feedback is used, then power detection is possible, but system crashes occur during voltage transitions
Solution Approach 1:
The patent triggers the power detection signal in advance during voltage transitions using the RC circuit transient. This preliminary action ensures the microcontroller is notified before the DC voltage fully transitions, allowing it to preserve system state information and avoid crashes during the unstable transition period
Solution Approach 2:
The patent provides beforehand cushioning by detecting power status changes before the system enters unstable voltage transition states. The RC circuit anticipates the transition and triggers detection early, cushioning the system against the harmful effects of operating during unstable voltage conditions
3Ease of operation
If remote control power on is attempted without AC power, then user input is received, but the system enters continuous standby loop
Solution Approach 1:
The patent implements feedback by continuously monitoring the power detection signal from the RC circuit and using it to control system power state transitions. The microcontroller reads the power status and makes informed decisions about whether to transition from standby to on state, preventing erroneous transitions when AC power is absent
4Object-affected harmful factors
If fast voltage signal is used for audio mute control, then pop noise is reduced, but system complexity increases
Solution Approach 1:
The patent uses the RC circuit as an intermediary to generate the fast transient signal needed for audio mute control without requiring direct modification of the audio circuitry. The RC circuit mediates between the slow DC power source and the fast audio mute requirement, providing the necessary fast signal while keeping the audio path simple
Solution Approach 2:
The patent makes the RC circuit multi-functional by using it for both power status detection and audio mute control timing. The same transient signal serves dual purposes: triggering the power detection logic and timing the audio mute to prevent pop noise, thus reducing overall system complexity through functional consolidation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides direct and fast indication of AC power status, preventing system crashes, reducing 'pop noise', and ensuring stable power management by enabling timely disabling/enabling of circuitry units, thus improving system reliability and user experience.
Implementation Method 1
an antenna, adapted to be mounted on or near a mains cable of the electrical system, for providing, in use, an induced signal when the mains cable is conveying electrical power
Data Source
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AI summary
A power sensing unit for an electrical system (e.g. A/V system such as a TV receiver), comprising: an antenna (e.g. coil), adapted to be mounted on or near a mains cable of the electrical system, for providing, in use, an induced signal when the mains cable is conveying electrical power; signal processing circuitry, coupled to the antenna, for receiving the induced signal and outputting a power sense signal, indicative of whether or not the mains cable is conveying electrical power. The signal processing circuitry may use stages for amplifying and inverting the induced signal, eliminating the DC level, converting the AC signal to DC, and inverting the signal, output signal having a HIGH DC level indicates that the mains cable is conveying electrical power. Also disclosed is an electrical system, comprising: a power sensing unit; processing circuitry; a plurality of circuitry units; Ul circuitry; wherein the processing circuitry is coupled to the power sensing unit and to the plurality of circuitry units, and wherein the processing circuitry is programmed for receiving a first user input signal (POWER OFF) from the UI circuitry, and transmitting a first control signal to one or more of said plurality of circuitry units if the power sense signal indicates that the mains cable is not conveying electrical power, thereby disabling the or each of said circuitry units. Corresponding methods are also disclosed. This helps to address, among other things, "pop noise" problems.