How to adjust the supply voltage of Class H Power Amplifier Module by input signal?

1. Dynamically Adjusting the Supply Voltage
The core feature of a Class H power amplifier is that its supply voltage is dynamically adjusted based on the amplitude of the input signal. When the input signal amplitude is large, the supply voltage switches to a higher voltage rail; when the input signal amplitude is small, the supply voltage switches to a lower voltage rail. This dynamic adjustment reduces the power loss in the output transistors, thereby improving overall efficiency.

2. Working Principle
Class H amplifiers usually use a single supply rail, but dynamically adjust the voltage of this supply rail to adapt to changes in the input signal. For example, when the instantaneous peak of the input signal exceeds a certain threshold, the supply voltage is increased; when the signal peak is below the threshold, the supply voltage is reduced.
This dynamic adjustment mechanism is similar to the operation of Class D or Class B amplifiers, but the Class H design is more complex because it requires precise control of changes in the supply voltage.

3. Implementation
Multi-level supply voltage: Some Class H amplifiers use multiple discrete supply voltage levels to select the appropriate voltage rail based on the amplitude of the input signal.
Continuously adjustable supply voltage: Other implementations continuously adjust the size of the supply voltage to adapt to changes in the input signal.
Pulse Width Modulation (PWM) Technology: In some designs, the power supply voltage is modulated by PWM technology to achieve finer control.

4. Efficiency Optimization
Dynamically adjusting the supply voltage can significantly reduce the power loss of the output transistor. For example, when the input signal amplitude is low, reducing the supply voltage can avoid unnecessary energy waste.
In addition, Class H amplifiers can further improve efficiency by reducing the voltage drop at the output.