Abstract
Compared with conventional Class-A, Class-B, and Class-AB amplifiers, Class-D amplifier, also known as switching amplifier, employs pulse width modulation (PWM) technology and solid-state switching devices, capable of achieving much higher efficiency. However, PWM-based switching amplifier is usually designed for low-voltage application, offering a maximum output voltage of several hundred Volts. Therefore, a step-up transformer is indispensably adopted in PWM-based Class-D amplifier to produce high-voltage output. In this paper, a switching amplifier without step-up transformer is developed based on digital pulse step modulation (PSM) and hybrid multilevel converter. Under the control of input signal, cascaded power converters with separate DC sources operate in PSM switch mode to directly generate high-voltage and high-power output. The relevant topological structure, operating principle, and design scheme are introduced. Finally, a prototype system is built, which can provide power up to 1400 Watts and peak voltage up to ±1700 Volts. And the performance, including efficiency, linearity, and distortion, is evaluated by experimental tests.
Highlights
Class-A, Class-B, and Class-AB amplifiers are usually termed as linear amplifiers for their switching devices operate in linear mode, while Class-D amplifiers are known as switching amplifiers, in which the switching devices are either fully turned on or completely turned off, operating in switch mode
Part of power has been consumed as heat by switches, efficiencies over 85% can be achieved in most situations for Class-D amplifier
Given that input signal is a sine wave, total harmonic distortion (THD) is most commonly defined as the ratio of the rms amplitude of a set of harmonic
Summary
Class-A, Class-B, and Class-AB amplifiers are usually termed as linear amplifiers for their switching devices operate in linear mode, while Class-D amplifiers are known as switching amplifiers, in which the switching devices are either fully turned on or completely turned off, operating in switch mode. This means that when the switch is conducting (turned on) there is virtually no voltage across the switch and that when the switch is not conducting (turned off) there is no current flowing through the switch. Linear amplifier has a theoretical efficiency of 78% at the utmost [2]
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