Henrik Schneider

Efficiency Optimization by Considering the High-Voltage Flyback Transformer Parasitics Using an Automatic Winding Layout Technique

This paper presents an efficiency optimization approach for a high-voltage bidirectional flyback dc-dc converter. The main goal is to optimize the converter for driving a capacitive actuator, which must be charged and discharged from 0 V to 2.5 kV dc and vice versa, supplied from a 24 V dc supply. The energy efficiency is optimized using a proposed new automatic winding layout (AWL) technique and a comprehensive loss model. The AWL technique generates a large number of transformer winding layouts. The transformer parasitics, such as dc resistance, leakage inductance, and self-capacitance are calculated for each winding layout. An optimization technique is formulated to minimize the sum of energy losses during charge and discharge operations. The efficiency and energy loss distribution results from the optimization routine provide a deep insight into the high-voltage transformer design and its impact on the total converter efficiency. The proposed efficiency optimization approach is experimentally verified on a 25 W (average charging power) with a 100 W (peak power) flyback dc-dc prototype.

Investigation of Transformer Winding Architectures for High-Voltage (2.5 kV) Capacitor Charging and Discharging Applications

Transformer parasitics such as leakage inductance and self-capacitance are rarely calculated in advance during the design phase, because of the complexity and huge analytical error margins caused by practical winding implementation issues. Thus, choosing one transformer architecture over another for a given design is usually based on experience or a trial and error approach. This paper presents analytical expressions for calculating leakage inductance, self-capacitance, and ac resistance in transformer winding architectures (TWAs), ranging from the common noninterleaved primary/secondary winding architecture, to an interleaved, sectionalized, and bank winded architecture. The calculated results are evaluated experimentally, and through finite-element simulations, for an RM8 transformer with a turns ratio of 10. The four TWAs such as, noninterleaved and nonsectioned, noninterleaved and sectioned, interleaved and nonsectioned, and interleaved and sectioned, for an EF25 transformer with a turns ratio of 20, are investigated and practically implemented. The best TWA for an RM8 transformer in a high-voltage bidirectional flyback converter, used to drive an electro active polymer based incremental actuator, is identified based on the losses caused by the transformer parasitics. For an EF25 transformer, the best TWA is chosen according to whether electromagnetic interference due to the transformer interwinding capacitance, is a major problem or not.

Bidirectional flyback converter with multiple series connected outputs for high voltage capacitive charge and discharge applications

This paper evaluates two different implementations of a bidirectional flyback converter for driving a capacitive electro active actuator, which must be charged and discharged from 0 V to 2.5 kV DC and vice versa, supplied from a 24 V battery. In one implementation, a high voltage MOSFET (4 kV) in series with a high voltage blocking diode is added, in parallel with a high voltage freewheeling diode of a conventional flyback topology, to enable bidirectional operation. Experimental result from a digitally controlled bidirectional flyback converter shows that the discharge energy efficiency is limited by the parasitics of the high voltage active components, which also prevent full utilization of valley switching during discharge process. A second implementation is therefore proposed, where the secondary of flyback transformer winding is split into multiple windings which are connected in series by lower voltage rating MOSFETs driven by a gate drive transformer. Simulation results to compare the operation of conventional and proposed converters are provided. The advantages of proposed implementation are improved energy efficiency and lower cost. Experimental results with two series connected secondary windings are provided to validate the proposed implementation.

New Incremental Actuators Based on Electroactive Polymer: Conceptual, Control, and Driver Design Considerations

This paper presents an overview of the widely used conventional linear actuator technologies and existing electroactive polymer-based linear and rotary actuators. It also provides the conceptual, control, and driver design considerations for a new dielectric electroactive polymer (DEAP)-based incremental actuator. The DEAP incremental actuator consists of three independent DEAP actuators with a unique cylindrical design that potentially simplifies mass production and scalability compared to existing DEAP actuators. To accomplish the incremental motion, a high-voltage (HV) bidirectional dc-dc converter independently charges and discharges each capacitive DEAP actuator. The topology used for the HV driver is a peak current controlled bidirectional flyback converter. The scalability of the proposed DEAP incremental actuator is discussed, and different scaled designs are provided. The estimated speeds and forces for various scaled incremental actuator designs are provided. The HV drivers are experimentally tested with a prototype of the DEAP incremental actuator. The energy efficiency measurement results of one of the HV driver are presented. The DEAP incremental actuator prototype achieved bidirectional motion with a maximum velocity of 1.5 mm/s, at 2.87 Hz incremental driving frequency, when all actuators are driven with 1.8 kV. Finally, two new improved concepts of DEAP-based incremental actuator are presented.