Headphone Driver Sequencing to Attenuate Pop and Click Noise
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Solution Overview
Problem
Existing multimedia devices, such as headphones, generate pop and click noise during power-up and power-down operations due to transient load currents when amplifiers are activated or deactivated, which existing technologies have not effectively attenuated.
Innovation Solution
A headphone driver and system-on-chip (SOC) design that includes pre-main and main amplifiers, switches, capacitors, and feedback resistors, controlled by a digital sequencer to manage voltage levels and maintain an output node at ground voltage during power operations, thereby minimizing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If amplifiers are activated or deactivated during power operations, then the headphone driver can perform power-up and power-down operations, but pop and click noise is generated due to transient load currents
Solution Approach 1:
The digital sequencer activates pre-main amplifiers before the main amplifier during power-up, and deactivates them after the main amplifier during power-down. This preliminary action prepares the circuit gradually, preventing sudden transient load currents that cause pop and click noise while maintaining full power operation capability
Solution Approach 2:
The amplifier system is divided into multiple pre-main amplifiers and a main amplifier, with each stage controlled independently by the digital sequencer. This segmentation allows gradual activation and deactivation, reducing transient load currents and eliminating pop and click noise during power operations
2Object-generated harmful factors
If multiple switches and pre-main amplifiers are added to control voltage levels, then pop and click noise is attenuated, but the device complexity increases
Solution Approach 1:
The digital sequencer serves multiple functions: it controls the activation sequence of pre-main amplifiers, manages switch operations, and coordinates power operations. This multi-functionality reduces the need for separate control circuits, attenuating pop and click noise without proportionally increasing device complexity
Solution Approach 2:
The patent combines multiple amplifiers and switches into an integrated circuit structure where components share common control signals and power rails. This merging approach implements noise attenuation functionality while minimizing the increase in overall device complexity through shared resources
Data Source
AI summary
A headphone driver includes a pre-main amplifier and a main amplifier. The pre-main amplifier receives an input signal from first and second node and outputs the input signal to a third node. The main amplifier is between the third node and a fourth node. A first switch is between the fourth node and a fifth node. A second switch is between the fourth node and a sixth node. A third switch is between the fourth node and a seventh node. A fourth switch is between the fifth and seventh nodes. A fifth switch is between the first and fifth nodes. A capacitor is between the third and fifth nodes. A first feedback resistor is between the first and seventh nodes. A second feedback resistor is between the second and sixth nodes, and the sixth and seventh nodes are connected to a speaker.