Power Amplifier Switch Timing to Prevent Short-Through Current
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Solution Overview
Problem
High-power audio amplifiers face efficiency issues, particularly in class A and class B amplifiers, where class A has low efficiency due to continuous current supply and class B experiences crossover distortion when no input signal is present, while class AB amplifiers aim to mitigate these issues but may still face short through currents.
Innovation Solution
A power amplifier design utilizing a control circuit to generate specific control signals for switches, ensuring that switches are turned on or off during specific periods to avoid short through currents, with a fifth switch creating a short path between nodes during certain periods to manage current flow efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a class A amplifier continuously provides current from the output terminal, then the amplifier can maintain ready state for immediate signal processing, but the efficiency becomes lower compared to class B, class C, and class AB amplifiers
Solution Approach 1:
The amplifier switches between different operating states periodically based on input signal presence. During first and third periods, the amplifier operates in a state with current provided from output terminal. During second and fourth periods, the amplifier operates in a different state with no current provided, creating a periodic switching pattern that balances readiness with energy efficiency
2Loss of energy
If a class B amplifier operates only during half-cycle of input signal, then the amplifier efficiency improves compared to class A, but crossover distortion occurs when no input signal is present
Solution Approach 1:
The amplifier uses periodic switching with four distinct periods where different switch combinations are activated. This periodic operation ensures that during each half-cycle, the appropriate switches are turned on to maintain signal continuity and eliminate crossover distortion, while during idle periods, switches are turned off to maintain high efficiency
Solution Approach 2:
The control circuit proactively manages switch states in advance of signal transitions. By pre-positioning switches in appropriate states during each period, the amplifier ensures smooth signal continuity without waiting for crossover conditions to occur, thereby preventing distortion while maintaining efficiency
3Reliability
If a class AB amplifier combines advantages of class A and class B, then crossover distortion is eliminated, but short through currents may still occur
Solution Approach 1:
The amplifier implements periodic switching with four distinct periods where switch combinations are systematically controlled. During first and second periods, specific switches are turned on while others are off, preventing simultaneous conduction. During third and fourth periods, different switch combinations are activated. This periodic control eliminates short through currents while maintaining the class AB advantage of crossover distortion elimination
Solution Approach 2:
The operating cycle is segmented into four distinct periods with different switch configurations. This segmentation prevents overlapping current paths that could cause short through currents, while each segment maintains appropriate bias conditions to eliminate crossover distortion. The segmentation approach allows precise control of current flow paths
Data Source
AI summary
A processing device including a control unit and a power amplifier is disclosed. The control unit generates a plurality of control signals according to an input signal. The power amplifier includes a plurality of switches. The control signals control the switches to turn on or off such that a short through current does not occur in the power amplifier.