Vaishnavi Ravi

Bio: Vaishnavi Ravi is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Flyback converter & High voltage. The author has an hindex of 2, co-authored 6 publications receiving 20 citations.

Modeling, Analysis, and Implementation of High Voltage Low Power Flyback Converter Feeding Resistive Loads

Abstract: In High Voltage flyback converters, the dominant factor that influences a converter operation is the parasitic capacitance. A significant portion of input energy is utilized in charging the parasitic capacitances of the circuit, which is circulated back to the source at the end of every switching cycle. The circulating energy is a function of output voltage, load power, and parasitic capacitances and remains significant in High Voltage Low Power (HVLP) applications. This energy transfer phenomenon involving parasitic capacitances results in a reduced fraction of input energy reaching the load in every cycle, thereby resulting in an apparent deviation in the converter operating point compared to ideal flyback in case of resistive loads. An analytical energy-based model is derived, which includes the effect of parasitic capacitances, and is valid for steady state and dynamics of HVLP flyback converters feeding resistive loads. The influence of parasitic capacitances on the switch voltage of the converter is exploited to achieve Zero Voltage Switching (ZVS), thereby minimizing the turn- on loss. The proposed analytical model is verified through simulation and experimental results on 1.5 kV/ 5 W and 1.5 kV/ 200 mW resistive loads.

An Energy-Based Analysis for High Voltage Low Power Flyback Converter Feeding Capacitive Load

Abstract: Generally, battery-fed capacitive loads are charged to high voltages in series of switching cycles with smaller fragments of energy delivered to the load in every cycle to ensure an efficient charging process. In high voltage low power (HVLP) flyback charging circuit, significant portion of input energy drawn from the source in a cycle is utilized by the effective parasitic capacitance of the HV transformer and semiconductor devices and circulated back to the source at the end of the cycle. This reduces the energy delivered to the load per cycle and hence the net energy delivered in the charging process. In this paper, an energy-based analysis and simplified energy-based model for HVLP charging circuits is derived. An energy-based approach is appropriate to describe and define the HVLP converter behavior in terms of load energy component and circulating energy component. The derived energy-based model is extended to obtain analytical closed-form expressions governing the essential parameters of the charging circuit. The proposed energy-based model and analytical formulation of essential parameters are experimentally validated on a 0–2.5 kV programmable high voltage charging circuit prototype fed from 12 V input battery source.

Steady state voltage gain of flyback converters for high voltage low power applications

Abstract: A significant influence of parasitics is perceived in high voltage low power flyback converters. The sinusoidal resonance between the magnetising inductance and the parasitic capacitance results in apparent deviations in voltage gain unlike the conventional flyback converter. This effect is predominant in case of very lightly loaded converter where the major portion of the input energy is consumed in charging the parasitic capacitances. The paper presents an analytical expression for steady state voltage gain of flyback converter in high voltage low power applications. Insight on sinusoidal resonance between the magnetising inductance and the parasitic capacitances is outlined and the effects of converter operating with fixed frequency is addressed. Profile of converter voltage gain and switch stress with variation in switching frequency is examined from which a range of frequency which offers optimal gain along with zero voltage stress during turn on is observed. A control scheme which deploys variable switching frequency thereby facilitating Zero Voltage Switching is investigated. Analysis of converter employing zero voltage switching scheme is carried out and the analytical equations governing the operation are derived. Simulation model and hardware prototype is built to validate the analytical results.

High Voltage Flyback Converter for Pulsed Loaded Applications

Abstract: High voltage pulses of the output power ranging from 5 W to 200 W are employed in food processing systems, water treatment process, electroporation, industrial and medical applications etc. The power converter configuration implemented to generate high voltage pulses is selected depending on the peak power rating requirement. In this work, a flyback converter configuration is selected to charge the energy storage capacitor meeting the desired voltage magnitude and charging time constraint. The energy storage capacitor is charged following peak current mode control with boundary conduction mode. In this proposed work, high voltage rectangular pulses of 1000 V magnitude with the desired pulse repetitive rate and pulse width is designed for various case studies and validated through corresponding simulation results.

Design and Implementation of Bipolar Bidirectional High Voltage Flyback Converter for Capacitive Loads

Abstract: This paper presents a modular circuit structure to generate bipolar high voltage pulses from a low voltage battery source Smart material based actuators and ion analysers require bipolar high voltage output in the range of ± 1 kV to 3 kV for their effective operation In this paper, two bidirectional flyback converter modules are connected in differential manner to achieve pulses of opposite polarities respectively Dedicated CPLD control cards are designed to govern the operation of individual module Each module operate with a two loop control scheme where inner loop detects Minimum Voltage Point (MVP turn on) and output loop controls the peak charging current The modules operate in a phase shifted manner with control signals communicated between the individual controllers to ensure module level coordination An experimental prototype fed from 12 V input is designed and control scheme is implemented to obtain ± 25 kV bipolar output voltage The experimental results observed are in good concordance with the simulation results

Modeling, Analysis, and Implementation of High Voltage Low Power Flyback Converter Feeding Resistive Loads

Abstract: In High Voltage flyback converters, the dominant factor that influences a converter operation is the parasitic capacitance. A significant portion of input energy is utilized in charging the parasitic capacitances of the circuit, which is circulated back to the source at the end of every switching cycle. The circulating energy is a function of output voltage, load power, and parasitic capacitances and remains significant in High Voltage Low Power (HVLP) applications. This energy transfer phenomenon involving parasitic capacitances results in a reduced fraction of input energy reaching the load in every cycle, thereby resulting in an apparent deviation in the converter operating point compared to ideal flyback in case of resistive loads. An analytical energy-based model is derived, which includes the effect of parasitic capacitances, and is valid for steady state and dynamics of HVLP flyback converters feeding resistive loads. The influence of parasitic capacitances on the switch voltage of the converter is exploited to achieve Zero Voltage Switching (ZVS), thereby minimizing the turn- on loss. The proposed analytical model is verified through simulation and experimental results on 1.5 kV/ 5 W and 1.5 kV/ 200 mW resistive loads.

An Energy-Based Analysis for High Voltage Low Power Flyback Converter Feeding Capacitive Load

Abstract: Generally, battery-fed capacitive loads are charged to high voltages in series of switching cycles with smaller fragments of energy delivered to the load in every cycle to ensure an efficient charging process. In high voltage low power (HVLP) flyback charging circuit, significant portion of input energy drawn from the source in a cycle is utilized by the effective parasitic capacitance of the HV transformer and semiconductor devices and circulated back to the source at the end of the cycle. This reduces the energy delivered to the load per cycle and hence the net energy delivered in the charging process. In this paper, an energy-based analysis and simplified energy-based model for HVLP charging circuits is derived. An energy-based approach is appropriate to describe and define the HVLP converter behavior in terms of load energy component and circulating energy component. The derived energy-based model is extended to obtain analytical closed-form expressions governing the essential parameters of the charging circuit. The proposed energy-based model and analytical formulation of essential parameters are experimentally validated on a 0–2.5 kV programmable high voltage charging circuit prototype fed from 12 V input battery source.

High Step-Up Quasi-Resonant Converter Featuring Minimized Switching Loss Over Wide Input Voltage Range

Abstract: This article proposes a high step-up quasi-resonant converter that minimizes switching loss over a wide range of input voltages. By employing a bidirectional switch and corresponding switching modulation, the proposed converter achieves the main switch with almost zero voltage, and therefore incurs very little switching loss at all active switches. Moreover, no instantaneous reactive current flows through the circuit under wide variations of input voltages and loads. The duty cycle of primary-side switches is fixed to 0.5; then, the input and clamp capacitor voltages become identical, and thereby the following resonant capacitor voltages remain in balance. As a consequence, the proposed converter becomes compact and achieves high boost-ratio and high efficiency over a wide range of input voltages. The operating principle of the converter is presented along with its design procedure. 400-W/380-V prototype of the proposed converter has been implemented and tested at 40–60 V to verify its effectiveness.

A bidirectional power converter

Abstract: Some embodiments are directed to a three-phase power converter for converting power between a power grid network and a battery that includes a three-phase grid transformer, a three-phase switching converter for coupling to a positive terminal of the battery, a first, second and third series inductors coupled between the three-phase grid transformer and the three-phase switching converter, a control circuit configured for controlling a first, second and third phase differences between first, second and third time-periodical power grid voltage signals provided by the grid transformer and first, second and third converter time-periodical voltage signals provided to the switching converter such that the first, second and third time-periodical power grid voltage signals and first, second and third converter time-periodical currents are in phase. The three-phase grid transformer provides electrical isolation between the power grid network and the battery.