Elimination of zero-crossing distortion for high-precision amplifiers

Abstract

Switch blanking time, also referred to as dead-time, is one of the dominant sources of output current and voltage distortion in pulse width modulated amplifiers. Extensive studies are known on elimination, minimization, and compensation of the effect. Most techniques achieve a reduction but are not capable of completely removing it. This paper demonstrates that it is possible to fully eliminate dead-time effects by applying the socalled opposed current converter topology in combination with advanced feedforward techniques. The zero-crossing behavior of the opposed current converter is analyzed and compared to a conventional full-bridge converter with equivalently filtered output. Simulations and measurements on a full-bridge and an opposed current converter of 1.5 kW are included to demonstrate the effectiveness of the proposed ideas for high-precision applications.

A Numerical Method for Calculating the Output Spectrum of an H-Bridge Inverter with Dead-time Based on Switching Mode Analysis

“…The H-bridge inverter with sine-pulse-width-modulation (SPWM) is widely used in industry. Some applications, such as lithography and magnetic resonance imaging (MRI), demand a high precision and high linearity output [1]. Taking lithography for example, the position error of the moving stage is determined by the non-linearity error of the current amplifier and it requires less than -100 dB current distortion for the high-precision motor control [2].…”

A 1 MHz Wide Bandgap Power Amplifier for High-Precision Applications

“…Since the switching speed of GaN transistors is faster than Si-based MOSFETs, the switching loss is largely reduced thus making it possible to switch at a higher frequency. To overcome the dead-time distortion, a different topology named by opposed current converter (OCC) is proposed in [4], which fully eliminates the dead-time and results in high linearity.…”

An Analysis of the Highly Linear Transfer Characteristics of Dual-Buck Converters

“…The impact of blanking time can indeed be reduced by feedback. However, due to the extremely fast change of the output voltage as a function of current and modulation index, as pointed out in [1] and further detailed in [2], it is not practical to eliminate the distortion due to blanking time with feedback only. However, improvements can be gained by using interleaving or multilevel techniques, as suggested in many papers including [3]- [5], to allow higher bandwidth and better disturbance rejection of the closed loop converter system compared to conventional 2-level PWM converters.…”

“…From (1) it can be seen that ideally a linear relation exists between the switch-node voltages and modulation indices when both legs of the DB are operated in CCM. For discontinuous conduction mode (DCM) that relation becomes nonlinear, as shown in [1], and should thus be avoided for high quality output. Both legs are effectively operated in parallel and can be analyzed separately when assuming u C f constant over one switching cycle (T sw ).…”