Linear Transition Totem Pole Amplifier for Low-THD Audio Output
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Solution Overview
Problem
Conventional switching amplifiers face challenges in minimizing total harmonic distortion (THD) and electromagnetic interference (EMI) while maintaining low switching losses, often requiring costly filter components and introducing power consumption issues and 'pop' noises.
Innovation Solution
A switching amplifier with a linear transition totem pole topology, incorporating a PWM control loop and a linear amplifier, which reduces THD by transitioning the low-frequency output slowly around zero crossing and eliminates the need for an inductor in the filter circuitry, thereby simplifying the filter design and reducing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If totem pole LSR modulation is used to reduce EMI pulses, then EMI is minimized and LC filter is not needed, but power consumption increases and pop noises are introduced
Solution Approach 1:
The patent changes the modulation parameters by implementing linear transition totem pole modulation where the low-frequency output transitions slowly around zero crossing rather than using conventional LSR modulation. This parameter change reduces switching activity and power consumption while maintaining low EMI.
Solution Approach 2:
The patent introduces dynamic control where the low-frequency output transitions slowly around zero crossing points. This dynamic approach adapts the switching behavior to the signal characteristics, reducing unnecessary switching and associated power consumption while maintaining low EMI.
2Object-affected harmful factors
If totem pole LSR modulation is used to reduce EMI pulses, then LC filter on OUTM is not needed, but pop noises occur during transitions
Solution Approach 1:
The patent changes the transition parameters by implementing linear transition around zero crossing points. This gradual transition approach eliminates abrupt voltage changes that cause pop noises while maintaining the low EMI characteristics of totem pole modulation.
Solution Approach 2:
The patent applies beforehand cushioning by preparing the transition in advance around zero crossing points. The linear transition smoothly prepares the output voltage changes before they occur, preventing sudden jumps that would generate pop noises.
3Loss of energy
If conventional switching amplifier topology is used, then switching losses are low, but THD increases and costly LC filters are required
Solution Approach 1:
The patent changes the modulation parameters by implementing linear transition totem pole modulation with slow transitions around zero crossing. This parameter optimization reduces THD by minimizing abrupt changes while maintaining the low switching losses characteristic of switching amplifier topology.
Data Source
AI summary
In one example, an apparatus comprises a control circuit, a first power stage, and a second power stage. The control circuit has an input, first control outputs, and second control outputs, the control circuit including a modulated signal generator coupled between the input and the first control outputs and an amplifier coupled between the input and the second control outputs. The first power stage has first control inputs and a first power stage output, the first control inputs coupled to the first control outputs. And the second power stage has second control inputs and a second power stage output, the second control inputs coupled to the second control outputs.