Full-Bridge Class D Amplifier With Common-Mode Choke Filtering
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Solution Overview
Problem
Class D amplifiers suffer from inefficiencies due to switching frequency leakage into the output signal, signal artifacts, and power losses from dead time, especially in full-bridge implementations requiring separate low-pass filters and non-ideal semiconductor switch characteristics.
Innovation Solution
A full-bridge class D amplifier design with half-bridge circuits featuring output inductors for zero voltage switching, coupled coils for common mode signal suppression, and a differential mode operation to minimize signal distortions and power losses, utilizing control signals with phase shifts and snubber circuits for efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low-pass filter is used to filter the output signal of the class D amplifier, then the switching frequency leakage is attenuated, but the power efficiency is reduced
Solution Approach 1:
The patent merges the low-pass filter function with the output coupling inductor already present in the full-bridge circuit. By utilizing the inherent inductance of the output coupling inductor, a separate low-pass filter is eliminated, thus maintaining power efficiency while still attenuating switching frequency leakage through proper inductor selection and circuit configuration.
Solution Approach 2:
The output coupling inductor is given multiple functions: it serves as both the output coupling element and the low-pass filter inductor. This multi-functionality reduces the overall component count and eliminates the power loss associated with a dedicated low-pass filter, while still providing the necessary filtering of switching frequency components.
2Object-affected harmful factors
If a dead time is introduced to prevent simultaneous conduction of switches, then switching artifacts are reduced, but power efficiency is reduced due to lost conduction time
Solution Approach 1:
The patent uses the output coupling inductor to preliminarily store energy during the dead time period. When one switch turns off and the other turns on, the inductor maintains current flow and prevents voltage spikes, thereby reducing switching artifacts without requiring a prolonged dead time that would reduce power efficiency.
Solution Approach 2:
The output coupling inductor acts as an intermediary element between the switches during the dead time transition. It absorbs and releases energy to smooth out the switching transitions, reducing voltage spikes and ringing artifacts while allowing for minimized dead time, thus maintaining power efficiency.
3Object-affected harmful factors
If separate low-pass filters are used for each half-bridge in a full-bridge implementation, then switching frequency leakage is filtered, but device complexity and power loss increase
Solution Approach 1:
The patent combines the filtering function into a single shared output coupling inductor that serves both half-bridges. This eliminates the need for separate low-pass filters for each half-bridge, reducing device complexity and minimizing the total power loss while still effectively filtering switching frequency leakage from the differential output.
Solution Approach 2:
The output coupling inductor performs multiple functions simultaneously: it couples the differential output to the load, provides common-mode rejection, and acts as the low-pass filter inductor for both half-bridges. This universal component approach reduces overall system complexity and power consumption.
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 design achieves higher efficiency and reduced signal distortions by enabling zero voltage switching with minimal dead time, effectively filtering out high-frequency components while maintaining low power consumption and amplifying audio signals with minimal artifacts.
Implementation Method 1
Each half-bridge circuit further comprises an output terminal inductor connected between the half-bridge output terminal and ground
Implementation Method 2
the full-bridge class D amplifier further comprises a first and second coil, that are coupled to form a common mode choke
Data Source
Figure 1
Figure 2a~2c
Figure 3
AI summary
The present disclosure relates to a full-bridge class D amplifier comprising a first and second half-bridge circuit, wherein each half-bridge comprises a half-bridge output terminal (OB1, OB2) between a high-side switch (SH1, SH2) and a low-side switch (SL1, SL2). Wherein the first and second half-bridge circuits are controlled by a respective control signal to operate in differential mode with a predetermined switching frequency and wherein each half-bridge circuit further comprises an output terminal inductor (OL1, OL2) connected between the half-bridge output terminal (OB1, OB2) and ground. The amplifier further comprises a first and second coil (C1, C2) coupled to form a common mode choke, wherein the first half-bridge output terminal (OB1) is connected to an input terminal of the first coil (C1), and wherein the second half-bridge output terminal (OB2) is connected to an input terminal of the second coil (C2).