Charge Pump Grounding Circuit for Audio Jack Noise Reduction
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Solution Overview
Problem
Audio jacks in electronic devices experience excessive ground noise when power is removed, leading to floating ground connections that can amplify hum or noise in connected speakers, especially when three or four-pole audio plugs are used.
Innovation Solution
The implementation of a charge pump-driven circuit using depletion mode transistors to maintain a grounded connection in audio jacks, ensuring that the ground contacts remain connected even when the device is powered off, and control logic to determine the type of audio plug and configure the grounding accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional grounding circuit is used that is powered by the device power supply, then the grounding circuit can be simplified and powered easily, but excessive ground noise occurs when power is removed causing floating ground connections
Solution Approach 1:
A charge pump circuit is introduced as an intermediary component between the power supply and the grounding transistors. The charge pump stores energy in a capacitor and releases it to maintain the grounding function during power transitions, mediating between the powered state and unpowered state to prevent floating ground connections.
Solution Approach 2:
The charge pump is pre-charged during the powered state before power removal occurs. This preliminary action stores sufficient energy in the capacitor to maintain the depletion mode transistor gate voltages during the subsequent unpowered period, ensuring continuous grounding without waiting for the problem to occur.
2Object-affected harmful factors
If depletion mode transistors are used to maintain grounding when powered off, then ground noise is reduced, but additional circuit components (charge pump) are required
Solution Approach 1:
The invention changes the operating parameters of the transistor from enhancement mode to depletion mode. Depletion mode transistors have the unique property of conducting at zero gate voltage, allowing them to remain on during power removal. This parameter change enables the grounding function to persist without active power supply.
3Use of energy by moving object
If the grounding circuit is powered down to save energy, then power consumption is reduced, but floating ground connections cause noise in connected speakers
Solution Approach 1:
The charge pump operates in periodic cycles, charging during the powered state and discharging during the unpowered state. This periodic action ensures that grounding is maintained during the critical transition period when power is removed, preventing noise while allowing power savings during steady unpowered operation.
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
This solution effectively reduces power supply noise in connected speakers by maintaining a stable ground path, regardless of the audio plug configuration, without requiring battery power to sustain the grounding circuit.
Implementation Method 1
A charge pump may be provided having an output coupled to gates of the first and second depletion mode transistors. The charge pump may be powered by an input supply voltage... When the charge pump is powered up, it may provide a voltage to the gate of the first depletion mode transistor and the gate of the second depletion mode transistor.
Data Source
AI summary
Circuits, methods, and apparatus for grounding contacts in an audio jack. One example may provide a driver, such as a charge pump, driving a first depletion mode transistor coupled between a first contact in an audio jack and ground, and a second depletion mode transistor coupled between a second contact in the audio jack and ground. The first depletion mode transistor and second depletion mode transistor may be p-channel transistors or n-channel transistors.