Audio Amplifier Current Control for High-Frequency Reproduction
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Solution Overview
Problem
Existing audio amplifiers face limitations in efficiency, high-frequency reproduction, and maximum power due to delays in current measurement, particularly during high-frequency sound signal reproduction, which affect the ratio of current supplied by class A and class D amplifiers.
Innovation Solution
An audio amplifier with an open-loop control loop that estimates the derivative of the current supplied to the load using the complex impedance of the load and the audio signal, allowing for precise control by introducing a signal representative of the product of the coupling inductance and the derivative of the current, thereby optimizing the ratio of currents between class A and class D amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a negative feedback loop is used to measure the current supplied to the load, then the current measurement can be obtained, but a delay in control is introduced which is detrimental during high frequency sound signal reproduction
Solution Approach 1:
The patent calculates the derivative of the current signal in advance using predictive algorithms before the actual control action is needed. By computing the rate of change of current based on previous measurements and feeding this predictive information forward, the system eliminates the delay inherent in traditional feedback loops while maintaining accurate current measurement capability.
2Power
If the ratio of current supplied by class A amplifier to class D amplifier is not optimized for high frequencies, then the amplifier can operate at high power, but heating of the class A amplifier increases and useful bandwidth is reduced
Solution Approach 1:
The patent dynamically adjusts the current distribution ratio between class A and class D amplifiers based on the frequency content of the input signal. At high frequencies, the system automatically shifts more current to the class D amplifier which has better high-frequency response and lower heat generation, while maintaining adequate power output. This dynamic adaptation optimizes both thermal performance and bandwidth.
3Device complexity
If the derivative of current supplied to the load is not accurately determined, then the control of power current generator is simplified, but the efficiency and high frequency reproduction capability of the amplifier is limited
Solution Approach 1:
The patent replaces direct physical measurement of current derivative with a computational approach. Instead of using complex hardware circuits to measure and differentiate the current signal in real-time, the system uses digital signal processing algorithms to calculate the derivative from sampled current measurements. This substitution of computational methods for mechanical/electrical measurement systems maintains accuracy while simplifying the overall device architecture.
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 enhances the amplifier's efficiency and bandwidth by accurately controlling the current supply, reducing heating in class A amplifiers and improving high-frequency reproduction without introducing significant delays.
Implementation Method 1
a power voltage generator, the output of which is connected to the output of the reference voltage generator, through a coupling inductance to form the power supply output of the load
Data Source
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AI summary
This amplifier comprises: - a reference generator (18); - a power generator (19), comprising a generator (20) whose output is connected to the output of the reference generator (18) via an inductor (22); and - control means (30) for the power generator (19) designed to input, for its control: - a signal representing the product of the value (L(iD)) of the inductor (22) and the time derivative of the current supplied to the load (16). The control means (30) comprise a control loop having a transfer function dependent on the complex impedance (Z(f)) of the load (16).