High-precision current control through opposed current converters

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 power amplifiers. Extensive studies are known on elimination, minimization, and compensation of the effect. Most techniques achieve a reduction of the distortion but are not capable of completely removing it. This paper demonstrates that it is possible to fully eliminate dead-time effects by applying the so-called opposed current converter topology in combination with decoupled output and bias current control. The bias current guarantees continuous conduction mode, resulting in almost linear behavior and no zero crossing distortion. The zero-crossing behavior of the opposed current converter is 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.