Full-Bridge Class D Amplifier With Common-Mode Choke Output
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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 switch characteristics.
Innovation Solution
A full-bridge class D amplifier design with half-bridge circuits featuring output inductors and coupled coils that enable zero voltage switching, reduce dead time, and suppress common mode signals, while using control signals phase-shifted by 180 degrees to drive the half-bridges differentially.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low-pass filter is added to filter out switching frequency components, then signal quality is improved, but power efficiency deteriorates due to additional power losses in the filter
Solution Approach 1:
The patent combines the low-pass filter function with the output impedance network of the class D amplifier. The output inductors and resistors that form part of the amplifier's output stage also serve as the filtering elements, eliminating the need for a separate low-pass filter circuit. This integration maintains signal quality by filtering switching frequency components while avoiding the additional power losses that would result from a separate filter stage.
2Reliability
If dead time is introduced to prevent simultaneous conduction of switches, then reliability is improved, but power efficiency deteriorates due to losses during the dead time period
Solution Approach 1:
The patent dynamically adjusts the dead time parameter based on the operating conditions of the amplifier. By monitoring the state of the output switches and the load conditions, the control system optimizes the dead time duration to be just sufficient to prevent simultaneous conduction, minimizing it to the lowest possible value that still ensures reliable switching. This reduces the time during which power losses occur while maintaining the necessary safety margin against switch overlap.
3Object-affected harmful factors
If separate low-pass filters are used for each half-bridge circuit, then signal quality is improved, but device complexity increases
Solution Approach 1:
The patent designs the output impedance network of each half-bridge circuit to serve dual functions: as part of the power amplification stage and as the low-pass filter for that channel. The same output inductors and resistors that are necessary for the amplifier operation also provide the filtering function, making the circuit elements universal and multi-functional. This eliminates the need for separate filter components and reduces overall device complexity.
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 minimizing dead time and filtering out switching frequency components, resulting in a high-power, low-distortion output signal.
Implementation Method 1
the full-bridge class D amplifier further comprises a first and second coil, that are coupled to form a common mode choke
Implementation Method 2
Each half-bridge circuit further comprises an output terminal inductor connected between the half-bridge output terminal and ground
Data Source
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 between a high-side switch and a low-side switch. 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 connected between the half-bridge output terminal and ground. The amplifier further comprises a first and second coil coupled to form a common mode choke, wherein the first half-bridge output terminal is connected to an input terminal of the first coil, and wherein the second half-bridge output terminal is connected to an input terminal of the second coil.