Dual H-Bridge Audio Amplifier for Low-Level EMI Reduction

The patent changes the electrical parameters of the amplifier output stage by implementing dual H-bridge configurations with different output impedances. The first H-bridge operates with low output impedance for high-level signals, while the second H-bridge operates with high output impedance for low-level signals. This parameter switching approach reduces electromagnetic noise coupling without adding physical shielding structures.

The patent applies different output impedance characteristics to different operating conditions. The first H-bridge provides low output impedance (first quality) for large signal amplitudes, while the second H-bridge provides high output impedance (second quality) for small signal amplitudes. This local quality differentiation allows noise reduction specifically when needed for low-level signals without affecting overall system performance.

The patent implements dynamic switching between two H-bridge configurations based on the instantaneous amplitude of the audio signal. The control circuit dynamically selects which H-bridge to activate: the first H-bridge for high-level signals and the second H-bridge for low-level signals. This dynamic adaptation allows the system to maintain high power efficiency for most of the time (when processing large signals) while providing noise reduction only when necessary (during low-level signals).

The patent applies high output impedance (second H-bridge) only partially - specifically during low-level signal conditions where noise coupling is most problematic. For the majority of operating conditions (high-level signals), the system uses the first H-bridge with low output impedance and high efficiency. This partial application of the noise-reduction mechanism minimizes the energy loss while still providing effective noise reduction when needed.

The patent segments the audio amplification function into two separate H-bridge circuits, each optimized for specific signal levels. The first H-bridge handles high-level signals with low output impedance, while the second H-bridge handles low-level signals with high output impedance. The control circuit segments the signal processing based on amplitude thresholds, activating the appropriate H-bridge for each signal level. This segmentation allows the system to achieve noise reduction for low-level signals without requiring a completely complex redesigned amplifier architecture.

The patent creates a universal amplifier structure where two H-bridge circuits share common components such as the audio input, power supply, and control logic. Both H-bridges are capable of amplifying audio signals, but they serve different functions based on signal level: one for high-level and one for low-level signals. This multi-functionality approach allows the system to handle different signal conditions with a unified design rather than requiring separate amplifier circuits for different signal levels.