Hybrid Differential Amplifier Without LC Filters for High Linearity
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Solution Overview
Problem
Class D amplifiers require passive lossless LC filters, which increase cost, size, and weight, limiting bandwidth and efficiency in applications like electric vehicles and wireless earphones.
Innovation Solution
A hybrid differential amplifier that combines inductive switching converters with linear amplifiers, incorporating local feedback and filters, to reduce inductor current ripple and support multiple input sources, enhancing speed and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional Class D amplifiers use passive lossless LC filters to demodulate signals and limit bandwidth, then electromagnetic interference is reduced, but cost, size, and weight increase
Solution Approach 1:
The patent extracts and removes the inductor from the traditional LC filter configuration. By using a switched capacitor circuit to replace the inductor's filtering function, the design eliminates the heavy inductive component while maintaining the necessary signal demodulation and bandwidth limiting functions. This extraction of the inductor directly reduces weight and cost without compromising EMI reduction capabilities.
Solution Approach 2:
The patent substitutes the passive inductive filtering mechanism with an active switched capacitor filtering system. The switched capacitor circuit uses capacitors and switches to synthesize the inductive impedance and perform signal demodulation, replacing the traditional mechanical/passive inductor-based LC filter. This substitution maintains filtering performance while eliminating the weight and cost penalties of physical inductors.
2Ease of operation
If traditional Class D amplifiers use passive lossless LC filters, then signal demodulation is achieved, but device complexity increases
Solution Approach 1:
The patent merges the filtering function with the output stage of the amplifier. The switched capacitor circuit is integrated into the amplifier's output path, combining signal demodulation, filtering, and power delivery functions into a unified structure. This integration eliminates the need for separate LC filter components and reduces overall device complexity while maintaining signal demodulation capability.
Solution Approach 2:
The switched capacitor circuit performs multiple functions simultaneously: it acts as a filter, a demodulator, and an impedance transformation network. This multi-functional design replaces the traditional separate LC filter and simplifies the overall amplifier architecture, reducing device complexity while achieving the necessary signal processing functions.
3Device complexity
If feedback loop filter is configured within the switching first amplification stage circuit, then unity gain bandwidth is limited by switching frequency, but implementation is simplified
Solution Approach 1:
The patent segments the feedback loop into distinct functional stages: the switching amplification stage and the filter stage. By separating the feedback filter from the switching stage and placing it in the second amplification circuit, the design allows the feedback loop to operate at a lower frequency than the switching frequency, thereby increasing the unity gain bandwidth without complicating the overall implementation.
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 hybrid amplifier achieves reduced inductor current ripple, improved linearity, and immunity to filtering circuits, while eliminating the need for LC filters, thus reducing size, weight, and extending battery life.
Implementation Method 1
a first amplifier, configured as an inductive switching converter, to perform pulse-width modulation (PWM) conversion based on a first input signal of the differential input signal to switch an inductor and generate a first output signal of the differential output signal
Data Source
AI summary
A hybrid differential amplifier that generates a differential output signal based on a differential input signal to drive a load, includes: a first amplifier configured as an inductive switching converter to perform pulse-width modulation (PWM) conversion based on a first input signal of the differential input signal to switch an inductor and generate a first output signal of the differential output signal; and a second amplifier configured to generate a second output signal of the differential output signal based on a second input signal of the differential input signal. The second amplifier is configured as a different type of amplifier distinct from the inductive switching converter. The second amplifier further generates the second output signal based on feedback from the differential output signal, thereby the differential output signal being linearly correlated with the differential input signal.