Dynamic Amplifier Rail Boosting for Higher Output Swing
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Solution Overview
Problem
Conventional power amplifiers are limited by voltage swing and load impedance, leading to restricted output power and increased distortion, with existing methods like bridging and switching power supplies having limitations and complications.
Innovation Solution
A power boost circuit that temporarily increases the power supply voltage by drawing current from a reservoir capacitor when the amplifier output approaches the rail voltage, allowing independent boosting of positive and negative supply rails to achieve a larger peak-to-peak voltage swing without requiring a bridged amplifier or switching power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the amplifier rail voltage is increased to increase output power, then the voltage swing and output power are improved, but the power supply complexity and heat dissipation increase
Solution Approach 1:
The reservoir capacitor is pre-charged to a voltage higher than the amplifier rail voltage during periods when maximum output is not required. This preliminary energy storage allows the capacitor to immediately supply additional voltage during transient peaks, eliminating the need for complex switching power supplies while maintaining high output power capability.
Solution Approach 2:
The reservoir capacitor acts as an intermediary energy storage device between the power supply and the amplifier. It decouples the amplifier from the main power supply, allowing the amplifier to draw transient current from the capacitor when needed, thereby simplifying the overall power supply architecture while enabling higher output power.
2Power
If the load impedance is reduced to increase output power, then the power delivery capability is improved, but the current requirement and distortion increase
Solution Approach 1:
The invention changes the voltage parameter dynamically by allowing the amplifier to operate with a time-varying supply voltage. The reservoir capacitor enables the supply voltage to increase during transient peaks, which allows the amplifier to maintain lower current levels while delivering the same power, thereby reducing distortion and avoiding the need to reduce load impedance.
3Power
If a bridged amplifier configuration is used to increase voltage swing, then the output power is improved, but the current requirement and load impedance requirements worsen
Solution Approach 1:
Instead of using a bridged configuration to achieve voltage swing, the invention uses preliminary energy storage in the reservoir capacitor to provide temporary voltage boosts. This allows a single amplifier to achieve the same voltage swing capability as a bridged amplifier without the associated complexity and current requirements.
4Power
If a switching power supply is used to increase power supply voltage, then the voltage swing capability is improved, but the interference and design complexity increase
Solution Approach 1:
The reservoir capacitor provides transient voltage boosts only when needed, acting as a simple, passive energy storage device. Unlike a switching power supply that continuously operates at high frequency, the capacitor remains inert during normal operation and only discharges during transient peaks, eliminating electromagnetic interference while providing the same voltage swing capability.
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
This solution enables a voltage swing of up to three times the supply voltage, delivering approximately 27 Watts into an 8Ω load while reducing distortion and heat dissipation, and allowing normal load impedance usage.
Implementation Method 1
The power boost circuit tracks the output signal from the amplifier and temporarily boosts the power supply input voltage signal feeding the amplifier, by drawing current from a reservoir capacitor when the output signal from the amplifier approaches the power supply rail voltage
Data Source
AI summary
A dynamic power supply for N amplifiers includes first and second power boost circuits which temporarily boost the positive or negative power supply rail, respectively. A control circuit monitors amplifier output signal levels and provides power boost control signals to the power boost circuits, which temporarily raise the positive supply voltage above the nominal voltage level in tandem with the highest output signal from the N amplifiers and lower the negative supply voltage below the nominal voltage level in tandem with the lowest output signal level from the N amplifiers. The power boost circuits each may be coupled to a reservoir capacitor from which current is drawn to provide the power boost. When inactive, the reservoir capacitors charge up from the respective power supply rails. The dynamic power supply is well suited for audio amplification systems.