Multi-Level Class D H-Bridge With On-Demand Boosted Voltage Switching
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Solution Overview
Problem
Conventional Class D amplifiers have low efficiency, particularly in portable applications, due to their operation at approximately 90% efficiency, which negatively impacts battery life, and voltage boosters further decrease overall efficiency to about 81%.
Innovation Solution
A multi-level boosted Class D amplifier is introduced, featuring a multi-level H-bridge with pairs of transistor switches coupled to multiple supply potentials, including a boost converter to generate amplitude-boosted supply potentials, a filter to remove noise, a quantizer to determine reference voltages, and a controller to generate pulse-modulated control signals for efficient switching, increasing efficiency by allowing current draw from the boost converter only when higher voltages are needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional transistor H-bridge is used in a Class D amplifier, then the amplifier can generate switched output voltage levels, but the operating efficiency is only approximately 90%, which negatively impacts battery life in portable applications
Solution Approach 1:
The H-bridge is segmented into multiple levels with separate transistor pairs (first pair for +VDD/-VDD switching, second pair for +VBOOST/-VBOOST switching). This segmentation allows selective activation of transistor pairs based on required output voltage levels, reducing unnecessary switching operations and improving overall efficiency.
Solution Approach 2:
The amplifier dynamically selects which transistor pair to activate based on the required output voltage level. The controller adjusts switching behavior in real-time, activating only the necessary transistor pair for each operating condition, thereby reducing energy loss from unnecessary switching operations.
2Power
If a voltage booster is added to increase amplifier output power, then higher voltage levels can be achieved, but the overall efficiency decreases to approximately 81% due to the booster's 90% efficiency
Solution Approach 1:
The system segments power delivery into two pathways: standard H-bridge switching for normal operation and boosted voltage pathway for high-power demands. This segmentation allows the amplifier to operate at high efficiency during normal conditions while only engaging the booster when maximum output power is required.
Solution Approach 2:
The amplifier changes operating parameters dynamically by switching between standard and boosted voltage modes based on demand. This parameter change allows the system to optimize efficiency for the current operating condition, using the booster only when high power output is necessary rather than continuously.
3Adaptability or versatility
If multiple transistor pairs are used in a multi-level H-bridge, then more voltage levels can be generated, but the device complexity increases
Solution Approach 1:
The multi-level H-bridge is segmented into functional pairs of transistor switches, where each pair handles specific voltage level transitions. This segmentation makes the complex multi-level structure more manageable and controllable, with each pair responsible for specific switching functions.
Solution Approach 2:
Each transistor pair in the multi-level H-bridge is designed to perform multiple functions: they can operate individually for standard voltage levels and work in combination for boosted voltage levels. This multi-functionality reduces the need for completely separate circuit paths for different operating modes.
Data Source
AI summary
Techniques to generate boosted multi-level switched output voltages from a boosted multi-level Class D amplifier. The amplifier may include a multi-level H-bridge, which may include pairs of transistor switches coupled to a first, second, and third supply potential. The second supply potential may be a boosted representation of the first supply potential. The amplifier may receive an input signal, and from the input signal may generate pulse-modulated control signals to control the switching for the transistor switches of the multi-level H-bridge. The amplifier may generate the boosted multi-level switched output voltages from output nodes of the multi-level H-bridge.