Two Mode Audio Amplifier Converter for Rail Pumping Reduction
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Solution Overview
Problem
Half-bridge class-D amplifiers face inefficiencies due to rail pumping and require a dual rail supply, which complicates overload protection and output sensing, and existing solutions do not adequately address these issues for low output power conditions.
Innovation Solution
A power conversion system for single-ended or full-bridge class-D amplifiers that uses a transformer arrangement with two primary and two secondary windings, along with a controller to generate different output voltage levels without changing duty cycle or dead time, actively reducing rail pumping through a supply rail mirroring mechanism, allowing for zero voltage/zero current switching and efficient voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If half-bridge topology is used for class-D amplifier, then cost and component count are reduced, but rail pumping occurs and efficiency deteriorates at idle and low output power
Solution Approach 1:
The patent implements dynamic switching between two operational modes (first mode with both switches conducting, second mode with only one switch conducting) based on the amplifier's output power level. This dynamic adaptation allows the system to optimize efficiency at idle/low power while maintaining cost-effectiveness through the half-bridge topology, directly resolving the contradiction between component simplicity and energy efficiency.
Solution Approach 2:
The patent changes the operational parameters of the power converter by adjusting which switches are conducted and how the transformer windings are connected, depending on the amplifier's power demand. This parameter change enables the system to eliminate rail pumping at idle conditions while maintaining the economical half-bridge structure, resolving the efficiency-cost contradiction.
2Power
If dual rail supply is used in half-bridge topology, then output power capability is improved, but system complexity and overload protection difficulty increase
Solution Approach 1:
The patent makes the power converter universal by enabling it to operate in multiple modes (first mode providing dual rail outputs, second mode providing single rail output) depending on the amplifier type. This multi-functionality allows the same converter design to support both single-ended and full-bridge amplifiers, simplifying the overall system architecture while maintaining output power capability.
3Reliability
If voltage regulation is implemented in conventional class-D power supply, then output voltage stability is improved, but switching frequency or dead time must be changed causing performance degradation
Solution Approach 1:
The patent segments the voltage regulation function from the audio signal processing function by using separate control circuits. The first control circuit regulates the positive and negative rail voltages independently without affecting the second control circuit's audio signal modulation. This segmentation allows voltage regulation to occur without changing switching frequency or dead time, maintaining both stability and audio performance.
Solution Approach 2:
The patent introduces intermediary control circuits that manage the switching operations and voltage regulation separately from the audio signal path. These intermediary controls enable voltage stabilization through mode switching rather than by altering the audio-critical switching parameters, thus maintaining audio performance while achieving reliable voltage regulation.
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 system achieves improved efficiency and compactness by eliminating rail pumping, maintaining zero voltage/zero current switching during regulation, and providing maximum voltage regulation without frequency or dead-time changes, enhancing audio performance and reducing component size.
Implementation Method 1
a transformer arrangement (2) having two primary windings (W1, W2) and two secondary windings (W3, W4)
Implementation Method 2
The system is preferable arranged to run in resonant mode with zero voltage/zero current switching, by providing resonant tank capacitors
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
A power converter with positive and negative supply rails outputs (7, 8) for feeding a single ended class D amplifier, the converter comprising a transformer arrangement (2), a supply pump reduction arrangement (4) connected between the secondary windings and the positive and negative supply rail outputs, and a boost drive mode switching arrangement (5). A controller (3) is adapted to control the power converter in a negate drive mode and a boost drive mode, wherein the output voltage in the bost mode is increased by means of the transformer and the boost drive mode switching arrangement. The output voltages on the positive and negative rails can be generated at two different output voltage levels without changing the duty cycle or dead time of the control signals.