Ground-Centered Headphone Amplifier With Charge Pump Noise Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional headphone amplifiers in portable devices face challenges with noise introduction, power wastage, and increased chip area due to the use of DC-to-DC converters and external power rails, which also result in reduced bass response and higher power dissipation.
Innovation Solution
A monolithic, low-voltage, high-swing amplifier circuit with an input stage operable on a single power supply and an output stage using a feedback network, level shifting unit, charge pump, and offset correction circuit to generate a negative supply voltage, minimizing noise and eliminating the need for external capacitors and dual power supplies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a DC-to-DC converter is used to boost the power supply voltage, then the voltage swing requirement is met, but noise is introduced and significant chip area is required
Solution Approach 1:
The patent replaces the DC-to-DC converter (electrical system) with a charge pump circuit that generates the necessary negative supply voltage through capacitive charging and discharging cycles, eliminating the noise-generating converter while achieving the required voltage swing
Solution Approach 2:
The patent introduces a charge pump as an intermediary circuit between the power supply and the output stage, which converts the single positive supply voltage into the required dual-rail voltage configuration, thereby avoiding direct use of noisy DC-to-DC converters
2Power
If a DC-to-DC converter is used to boost the power supply voltage, then the voltage swing requirement is met, but significant chip area is required
Solution Approach 1:
The patent replaces the bulky DC-to-DC converter with a compact charge pump implementation that achieves the same voltage boosting function using smaller capacitive elements and simpler switching circuitry, reducing the overall chip area
Solution Approach 2:
The patent changes the operating parameters by using a charge pump frequency and capacitor sizing optimized for the specific voltage swing requirement, achieving the necessary voltage multiplication with minimal area compared to conventional DC-to-DC converter designs
3Adaptability or versatility
If a capacitor is used to couple the core with the headphone amplifier, then the different reference voltages are handled, but chip area increases and bass response is reduced
Solution Approach 1:
The patent extracts the voltage level adaptation function from the coupling capacitor and implements it through the charge pump-generated negative supply voltage, which actively compensates for reference voltage differences without requiring large coupling capacitors
Solution Approach 2:
The patent replaces the passive capacitive coupling method with an active voltage regulation approach using the charge pump and level shifting circuitry, eliminating the need for large area coupling capacitors while maintaining reference voltage compatibility
4Adaptability or versatility
If a capacitor is used to couple the core with the headphone amplifier, then the different reference voltages are handled, but bass response is reduced
Solution Approach 1:
The patent extracts the voltage level adaptation function from the coupling capacitor and implements it through the charge pump-generated negative supply voltage, allowing the use of smaller capacitors that do not attenuate bass frequencies
Solution Approach 2:
The patent replaces the passive capacitive coupling method with an active voltage regulation approach using the charge pump and level shifting circuitry, eliminating the frequency response degradation caused by large coupling capacitors
5Reliability
If an LDO regulator is used to provide power supply, then voltage regulation is achieved, but power consumption increases
Solution Approach 1:
The patent replaces the LDO regulator with a charge pump-based voltage generation system that achieves the required voltage regulation through capacitive switching and feedback control, eliminating the continuous power dissipation inherent in LDO regulators
Solution Approach 2:
The patent uses periodic charging and discharging of capacitors in the charge pump circuit to generate and regulate the negative supply voltage, achieving voltage regulation through pulsed energy transfer rather than continuous dissipation
6Adaptability or versatility
If an external negative power rail is generated, then dual supply requirements are met, but noise in the form of ripples is introduced
Solution Approach 1:
The patent introduces a charge pump as an intermediary circuit that generates the negative supply voltage internally, acting as a clean buffer between the single positive power supply and the dual-rail amplifier stages, thereby eliminating external ripple sources
Solution Approach 2:
The patent replaces the external negative power rail generation system with an internal charge pump circuit that synthesizes the required negative voltage, eliminating the noise and ripple associated with external power supply circuits
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 a compact, power-efficient amplifier with reduced noise and power dissipation, maintaining bass response while achieving a high signal swing, thus enhancing the audio output quality in portable devices.
Implementation Method 1
a charge pump coupled to the output amplifier stage. The charge pump is operational to generate a negative supply voltage provided to the output amplifier stage and to minimize a noise associated with the negative supply voltage
Implementation Method 2
The amplifier includes a feedback network coupled between the first input terminal and an output of the output amplifier stage
Implementation Method 3
The level shifting unit is responsive to a difference in magnitude between an external sense pin and the second input terminal to generate a level shifting current that enables the output amplifier stage to bring down a DC value in the output signal
Data Source
AI summary
A minimal area, power efficient, high swing and monolithic ground centered headphone amplifier circuit operable on a low voltage. An input amplifier stage includes a first input terminal and a second input terminal and having a first gain. An output amplifier stage is coupled to an output of the input amplifier stage to provide an output signal and having a second gain. A feedback network coupled between the first input terminal and the output of the output amplifier stage. A level shifting unit coupled to the first input terminal and the feedback network. A charge pump coupled to the output amplifier stage to generate a negative supply voltage and to minimize a noise associated with the negative supply voltage using a loop gain of the amplifier, wherein the loop gain is a combination of the first gain, the second gain, and a gain of the feedback network.