Dieter Polenov

PWM Dead Time Optimization Method for Automotive Multiphase DC/DC-Converters

This paper introduces a PWM dead time optimization method for multiphase DC/DC-converters with synchronous rectifiers. The aim of the method is to reduce power losses. After a perturbation of the dead times in one converter phase, the phase-currents starts to deviate, whereby the most efficient phase has the higher current. A current balancing controller compensates for this deviation by adjusting duty cycles. Consequently, optimal dead times can be detected by duty cycle differences of the phases. The proposed optimization approach was implemented in a two-phase boost-/buck converter prototype for automotive dual-voltage power-nets. No additional components or circuit modifications were necessary. The detection of optimal dead times, increasing efficiency and reduction of voltage transients are discussed and investigated experimentally.

Observer based PWM dead time optimization in automotive DC/DC-converters with synchronous rectifiers

An observer based PWM dead time optimization approach for DC/DC-converters with synchronous rectifiers is introduced. The method is well suited, if optimization of PWM dead times at varying converter bus-voltages is required. In order to minimize effects of uncertainties, disturbances and noise on the estimated state variables, an intrinsic hardware implemented observer is proposed. A two-phase DC/DC-converter prototype for an automotive dual-voltage power-net was developed. The optimization concept was realized in the converter control structure without using additional components. The detection of optimal PWM dead times, increasing efficiency and reduction of voltage transients were shown experimentally.

Bus-voltage ripple optimization method for automotive multiphase DC/DC-converters

Phase interleaving is a well known technique to increase output power, power density, and efficiency of DC/DC-converters. If the n-phase converter is ideal (symmetrical), the first n-1 harmonics of the ripple are canceled in the bus-capacitors and the cut-off frequency of the EMI-filters can be increased. But tolerances of real components and control circuit can seriously limit this theoretical benefit. Tolerances of phase-shift, storage inductors and phase-current sensors are investigated to determine the causes of an unsymmetrical converter system. In order to ensure near ideal ripple cancellation despite high phase-current sensor tolerances, an approach using closed-loop control of the 1st harmonic is introduced and tested experimentally. This approach significantly improves the current balancing performance of an automotive two-phase converter.