Common Mode Choke Coil Layout for Single-End and BTL Class-D Amplifiers
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Solution Overview
Problem
Existing power amplifiers with class-D amplifiers and common mode choke coils cannot effectively switch between single-end and BTL connection modes without causing magnetic flux saturation, which prevents effective noise removal in both modes.
Innovation Solution
A power amplifier design featuring two class-D amplifiers with a common mode choke coil device consisting of four coils wound on a common core, allowing for effective noise removal in both single-end and BTL connection modes by canceling magnetic fluxes for normal signals while creating impedance for common mode noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a common mode choke coil is provided in a class-D amplifier for removing common mode noise, then noise removal capability is improved, but the amplifier cannot be used in BTL connection mode due to magnetic flux saturation
Solution Approach 1:
The common mode choke coil is divided into multiple windings (first winding and second winding) that can be independently connected to different output terminals. This segmentation allows the same choke coil structure to serve multiple connection modes by reconfiguring which windings are connected to hot-side or ground-side terminals.
Solution Approach 2:
The common mode choke coil is designed with multiple windings that can be configured for both single-end connection mode and BTL connection mode. The same choke coil structure performs the dual function of noise filtering in single-end mode and differential signal transmission in BTL mode, eliminating the need for separate choke coils for each mode.
2Productivity
If two class-D amplifiers are provided for stereo signals, then audio output capability is improved, but noise removal becomes problematic when switching between single-end and BTL modes
Solution Approach 1:
Two class-D amplifiers are combined in a single power amplifier unit with a shared common mode choke coil. The choke coil's multiple windings are strategically connected to handle common mode noise from both amplifiers simultaneously, whether operating in single-end mode (each amplifier to separate speakers) or BTL mode (amplifiers driving single speaker differentially).
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
Enables the power amplifier to remove common mode noise without affecting normal signals, regardless of the connection mode, ensuring effective noise reduction in both single-end and BTL connection configurations.
Implementation Method 1
common mode currents (noise components), transmitted in the common mode, flow over the hot-side winding 52 and ground-side winding 53 in phase with each other, so that magnetic fluxes are produced in the two windings 52 and 53 in the same direction. Consequently, magnetic fluxes of the core 51 are added together to produce a great impedance.
Implementation Method 2
For a current transmitted in a normal mode (i.e., output signal of the class-D amplifier), on the other hand, because a current flowing through the hot-side winding 52 to a speaker and a current flowing from the speaker to the ground-side winding 53 in an opposite direction to the former current counterbalance each other, magnetic fluxes produced in the hot-side winding 52 and the ground-side winding 53 cancel out each other.
Data Source
AI summary
Common mode choke coil device includes four coils wound on a core in a same direction. Hot-side outputs of first and second class-D amplifiers are connected to respective ones of first ends of two of the four coils, and first and second hot-side output terminals are connected to respective ones of second ends of the two coils. Ground-side outputs of the first and second class-D amplifiers are connected to respective ones of the first ends of remaining two of the four coils, and first and second ground-side output terminals are connected to respective ones of the second ends of the remaining two coils. Single-end connection is realized by connecting a separate load to each of the class-D amplifiers via the corresponding first (or second) hot-side and ground-side output terminals. BTL connection is realized by connecting a single load to the class-D amplifiers via the first and second hot-side output terminals.