Prasanth Thummala

Battery powered high output voltage bidirectional flyback converter for cylindrical DEAP actuator

DEAP (Dielectric Electro Active Polymer) actuator is essentially a capacitive load and can be applied in various actuation occasions. However, high voltage is needed to actuate it. In this paper, a high voltage bidirectional flyback converter with low input voltage is presented. The fundamental operating principle for both energy transfer process and energy recovery process is analyzed in detail. In order to verify the analysis, critical simulation results are provided. So far, a unidirectional flyback converter, which can realize the energy transfer process, has been implemented in the lab. The design parameters for flyback transformer and snubber circuits are illustrated. Moreover, the experimental waveforms are provided.

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.

Dielectric electro active polymer incremental actuator driven by multiple high-voltage bi-directional DC-DC converters

This paper presents driving circuit for a recently invented dielectric electro active polymer (DEAP) incremental actuator. The basic operation of such an actuator is bio-inspired from the movement of an inchworm. The actuator consists of three electrically isolated, and mechanically connected capacitive sub-actuators. It needs to be driven by three high voltage (~2.5 kV) DC-DC converters, to achieve the linear incremental motion. The topology used for this application is a bi-directional flyback DC-DC converter. The control of the incremental actuator involves, implementation of digital controller used for controlling charge and discharge sequences of the individual sub-actuators, and monitoring and adjustment of the output voltages of three high voltage DC-DC converters to provide over-voltage protection capability. Three power stages of the proposed converter were experimentally tested. The experimental results and efficiency measurements are shown.

Digital control of a high-voltage (2.5 kV) bidirectional DC-DC converter for driving a dielectric electro active polymer (DEAP) based capacitive actuator

This paper presents a digital control technique to achieve valley switching in a bidirectional flyback converter used to drive a dielectric electro active polymer based incremental actuator. The incremental actuator consists of three electrically isolated, mechanically connected capacitive actuators. The incremental actuator requires three high voltage (~2.5 kV) bidirectional DC-DC converters, to accomplish the incremental motion by charging and discharging the capacitive actuators. The bidirectional flyback converter employs a digital controller to improve efficiency and charge/discharge speed using the valley switching technique during both charge and discharge processes, without the need to sense signals on the output high-voltage side. Experimental results verifying the bidirectional operation of a single high voltage flyback converter are presented, using a film capacitor as the load. Energy efficiency measurements are provided.

High voltage Bi-directional flyback converter for capacitive actuator

This paper presents a high voltage DC-DC converter topology for bi-directional energy transfer between a low voltage DC source and a high voltage capacitive load. The topology is a bi-directional flyback converter with variable switching frequency control during the charge mode, and constant switching frequency control during the discharge mode. The converter is capable of charging the capacitive load from 24 V DC source to 2.5 kV, and discharges it to 0 V. The flyback converter has been analyzed in detail during both charge and discharge modes, by considering all the parasitic elements in the converter, including the most dominating parameters of the high voltage transformer viz., self-capacitance and leakage inductance. The specific capacitive load for this converter is a dielectric electro active polymer (DEAP) actuator, which can be used as an effective replacement for conventional actuators in a number of applications. In this paper, the discharging energy efficiency definition is introduced. The proposed converter has been experimentally tested with the film capacitive load and the DEAP actuator, and the experimental results are shown together with the efficiency measurements.

Investigation of transformer winding architectures for high voltage capacitor charging applications

Transformer parameters 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 work presents equations regarding calculation of leakage inductance, self-capacitance and AC resistance in transformer winding architectures, ranging from the common non-interleaved primary/secondary winding architecture, to an interleaved, sectionalized and bank winded architecture. The analytical results are evaluated experimentally and through FEM simulations. Different transformer winding architectures are investigated in terms of the losses caused by the transformer parasitics for a bidirectional high-voltage (~1500 V) flyback converter used to drive a dielectric electro active polymer based incremental actuator. The total losses due to the transformer parasitics for the best transformer architectures is reduced by more than a factor of ten compared to the worst case transformer architectures.

Digital Control of a High-Voltage (2.5 kV) Bidirectional DC--DC Flyback Converter for Driving a Capacitive Incremental Actuator

This paper presents a digital control technique to achieve valley switching in a bidirectional flyback converter used to drive a dielectric electroactive polymer-based capacitive incremental actuator. This paper also provides the design of a low input voltage (24 V) and variable high output voltage (0-2.5 kV) bidirectional dc-dc flyback converter for driving a capacitive incremental actuator. The incremental actuator consists of three electrically isolated mechanically connected capacitive actuators. It requires three high-voltage (HV) (2-2.5 kV) bidirectional dc-dc converters to accomplish the incremental motion by charging and discharging the capacitive actuators. The bidirectional flyback converter employs a digital controller to improve the efficiency and charge/discharge speed using the valley switching technique during both charge and discharge processes, without the need to sense signals on the output HV side. Experimental results verifying the bidirectional operation of a HV flyback converter are presented using a 3-kV polypropylene-film capacitor as the load. The energy-loss distributions of the converter are presented when 4- and 4.5-kV HV mosfets are used on HV side. The flyback prototype with a 4 kV mosfet demonstrated 89% charge energy efficiency to charge the capacitive load from 0 V to 2.5 kV, and 84% discharge energy efficiency to discharge it from 2.5 kV to 0 V.

Optimization of bi-directional flyback converter for a high voltage capacitor charging application

This paper presents an optimization technique for a flyback converter with a bidirectional energy transfer. The main goal is to optimize the converter for driving an incremental dielectric electro active polymer actuator, which must be charged and discharged from 0 V to 2500 V DC, supplied from a 24 V battery. The proposed optimization routine sweeps through a database of low voltage switching devices, and transformer core types and sizes. For each core, important winding parameters such as, the vertical winding space allocation for primary and secondary windings, and the spacing between the secondary windings layers are also swept. This enables the optimization routine to calculate and optimize the losses caused by transformer parasitics such as leakage inductance, self-capacitance and AC resistance which is crucial in achieving a high energy efficiency and high power density required for this application. The efficiency and loss distribution results provided by the optimization routine provide a deep insight into the transformer design and its impact on total converter efficiency. Finally, experimental work on a prototype of the bi-directional flyback converter is presented. The maximum charging and discharging energy efficiencies of the optimized design, are 96.1% and 85%, respectively.

Analysis of Dielectric Electro Active Polymer actuator and its high voltage driving circuits

Actuators based on dielectric elastomers have promising applications in artificial muscles, space robotics, mechatronics, micro-air vehicles, pneumatic and electric automation technology, heating valves, loud speakers, tissue engineering, surgical tools, wind turbine flaps, toys, rotary motors, and grippers for material handling, etc. This paper focuses on the application of Dielectric Electro Active Polymer (DEAP) technology as an actuation mechanism for different applications. The DEAP material requires very high voltage (~2.5 kV DC) to fully utilize it as an actuator. In this paper the DEAP actuator is analyzed in detail and the actuator structures, for the wind turbine flap and the heating valve applications are shown. Different high voltage switch mode power supply topologies for driving the DEAP actuator are discussed. The simulation and experimental results are discussed.

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.