Sung-Roc Jang

Development and Optimization of High-Voltage Power Supply System for Industrial Magnetron

This paper describes the design and analysis of a 42-kW (14 kV, 3 A) high-voltage power supply for a 30-kW industrial magnetron drive. The design is based on a series resonant converter in discontinuous conduction mode (DCM) to take advantage of both the superior arc protection stemming from the current source characteristics and the high power density owing to the use of parasitic elements such as the leakage inductance in the high-voltage transformer. The detailed design procedure for the resonant tank and high-voltage transformer with respect to the input and output specifications is described on the basis of a simplified analysis of the DCM series resonant converter. Special considerations for designing high-power high-voltage power supplies are provided, such as series stacking of diodes for a voltage doubling rectifier and insulation between each winding of the high-voltage transformer. In addition, a comparative study using theoretical equations, simulation, and experimental results was carried out. This study yielded the output voltage and current characteristics at different switching frequencies and verified the advantages of this topology, such as arc protection without an additional protection circuit and high efficiency due to zero-current or zero-voltage switching. Moreover, the parallel operation of two converters with phase shifted gating signal is proposed to reduce the output current ripple and increase power capability for higher power magnetron drive. Additionally, the design considerations of two auxiliary power supplies (a filament power supply: 15 V, 150 A and a magnet power supply: 50 V, 5 A) are also provided and optimized for effective driving industrial magnetron. Finally, the developed power supply was tested with a 30-kW industrial magnetron, and the results prove the reliability and robustness of the proposed scheme.

Design of high voltage capacitor charger with improved efficiency, power density and reliability

This paper describes the design of a 48 kJ/s high-voltage capacitor charging power supply (CCPS), focusing on its efficiency, power density, and reliability. On the basis of a series-parallel resonant converter (SPRC) that provides high efficiency and high power density owing to its soft-switching, the design of the CCPS is explained in detail, including its input filter, resonant tank parameters, high-voltage transformer and rectifier, as well as its protection circuit. By using two resonances per switching cycle, which provides a trapezoidal instead of a sinusoidal waveform of the resonant current, the proposed CCPS can take advantage of the lower conduction loss and reduced switching loss by improving the crest factor and allowing a higher value of the snubber capacitor, respectively. In addition, the compact design of an input filter without bulky components such as a DC reactor and an electrolytic capacitor allows for high power density, a high power factor, and low cost. In addition, the control loops for the voltage and current were optimized with a fast response time in order to compensate for the low frequency ripple of the input voltage, which results from the reduced filter component. Experiments on the developed charger were carried out with both resistor and capacitor loads in order to measure not only its efficiency and power factor with respect to the output power but also its charging time, in order to estimate the average charging current. The experimental results obtained with a resistor load showed a maximum efficiency of 96% and a power factor of 0.96 for a full-load condition. For the measured charging time of a 4 mF capacitor, with 9.68 s for 10 kV charging, the average charging current was estimated as 4.13 A. Moreover, to verify the reliability of the developed CCPS, a variety of tests, including opening and shorting of the output terminal as well as misfiring of the discharge switch during the charging operation, were performed with a 200 kJ pulsed power system. Finally, it was experimentally confirmed that the developed CCPS shows high performance in terms of efficiency (96 %), power factor (0.96), and reliability with a high power density (820 W/L).

Design of a High-Efficiency 40-kV, 150-A, 3-kHz Solid-State Pulsed Power Modulator

This paper deals with the detailed design of a pulsed power modulator using insulated gate bipolar transistor (IGBT) switches for industrial applications. Output specifications of the proposed modulator are as follows: variable output pulse voltage 1~40 kV; pulse width 0.5~5 μs ; maximum pulse repetition rates 3 kHz, and average output power of 13 kW. The proposed pulsed power modulator consists of a high-voltage capacitor charger based on a high-efficiency resonant inverter and pulse generator part including a series of connected 24 pieces power cells. To verify the proposed design, PSpice modeling was performed. Finally, experimental results proved the reliability and robustness of the proposed solid-state pulsed power modulator.

Compact and high repetitive pulsed power modulator based on semiconductor switches

This paper describes the design of a compact and highly repetitive pulsed power modulator based on semiconductor switches. Output specifications of the proposed modulator are as follows: variable output pulse voltage, 1-10 kV; width, 1-10 μs; pulse repetition rate (PRR), 1-50,000 pps; and average output power, 10 kW. The proposed solid-state pulsed power modulator has two main parts: an IGBT stack that hasa gate drive circuit for the pulse output with a variable pulse width and repetition rate, and a capacitor charger that has a controllable output voltage. To connect all the storage capacitors in a series for high voltage pulses, a simple and reliable IGBT stack structure was proposed based on the Marx generator. In addition, the gate driver circuit, which supplies power and signals to all the IGBTs simultaneously, was introduced. This providesa superior protection function against the arc and the short. To charge the storage capacitors, a novel 10 kW (10 kV, 1 A) high voltage capacitor charger with the combined advantage of a series-loaded resonant converter and a ZVS (zero-voltage-switching) full-bridge pulse width modulation (PWM) converter was proposed and designed especially for the solid-state pulsed power modulator. Theexperiment results verified that the proposed scheme and structure can be used effectively for a high voltage pulsed power modulator that requires variable voltage, repetition rate, and pulse width, depending on the process of the applications.

Design and Implementation of Enhanced Resonant Converter for EV Fast Charger

This paper presents a novel application of LCC resonant converter for 60kW EV fast charger and describes development of the high efficiency 60kW EV fast charger. The proposed converter has the advantage of improving the system efficiency especially at the rated load condition because it can reduce the conduction loss by improving the resonance current shape as well as the switching loss by increasing lossless snubber capacitance. Additionally, the simple gate driver circuit suitable for proposed topology is designed. Distinctive features of the proposed converter were analyzed depending on the operation modes and detail design procedure of the 10kW EV fast charger converter module using proposed converter topology were described. The proposed converter and the gate driver were identified through PSpice simulation. The 60kW EV fast charger which generates output voltage ranges from 50V to 500V and maximum 150A of output currents using six parallel operated 10kW converter modules were designed and implemented. Using 60kW fast charger, the charging experiments for three types of high-capacity batteries were performed which have a different charging voltage and current. From the simulation and experimental results, it is verified that the proposed converter topology can be effectively used as main converter topology for EV fast charger.

Low-Ripple and High-Precision High-Voltage DC Power Supply for Pulsed Power Applications

This paper describes the design and implementation of a three-phase resonant converter with low ripple and high control accuracy. Based on a three-phase LCC-type resonant converter-which has advantages of low ripple, highefficiency, and high-power density compared with a single-phase converter-a high-voltage power supply with low ripple (<;0.1%) was designed. In addition to the general merits of an LCC-type resonant converter operating at continuous conduction mode- including soft switching, low conduction loss, and current source characteristics-the proposed scheme uses only one phase under a light-load condition by having different leg designs of the gate drive circuit and snubber parameters. This allows the design to overcome the operational constraints of the general LCC-type resonant converter. The distinctive design of the three-phase converter structure provides high efficiency and low ripple not only during rated operation, but also under light-load conditions. In order to analyze the high performance of the proposed scheme from no load to rated load, a PSPICE simulation was carried out. Comparison results with a conventional LCC-type resonant converter based on a single-phase structure are analyzed from the viewpoints of output ripple, losses, and operable load range. Using the proposed converter, a 20-kV, 20-kW high-voltage dc power supply design and implementation was presented with a superior gate drive circuit. Finally, the superiority of the proposed converter was verified through a simulation and experimental results. It was experimentally confirmed that the developed power supply achieves high performance in terms of efficiency (98%), operable load range (0.5-20 kV), and low ripple (0.05%), with a high power density.

Comparative Study of MOSFET and IGBT for High Repetitive Pulsed Power Modulators

This paper presents an investigation of semiconductor switches for high voltage solid-state pulsed power modulators from the viewpoint of pulse rising time, efficiency, and reliability. A comparative study of insulated gate bipolar transistor (IGBT) and metal oxide semiconductor field effect transistor (MOSFET) devices is provided, focusing particularly on the characteristics of each device for pulsed power applications. Two kinds of stacks for 10-kV pulses are developed with a high voltage capacitor charger in order to experimentally compare the characteristics of each device. Although the structure of each stack is similar, the number of power cells for the 10-kV pulse is different due to the device voltage rating. The power cell voltage for IGBT and MOSFET-based stacks is about 840 V and 560 V, respectively. Therefore, two types of transformer, with six secondary windings for the IGBT stack and nine secondary windings for the MOSFET stack, are also designed for storage capacitor charging. Moreover, the ease of varying the pulse repetition rate and the pulse width shows the advantages of the developed modulators in facilitating the measurement of device characteristics in different pulse output conditions. The experiments are performed with noninductive resistor loads, and the results of the comparison tests are discussed. In addition, the results prove that the developed modulator can be effectively used for high repetitive pulsed power applications.

Pulsed-Power System for Leachate Treatment Applications

This paper presents a water treatment system for leachate from sewage-filled ground that uses a pulsed-power modulator developed based on semiconductor switches in order to realize a long life, a high repetition rate, and a fast rising time. The specifications of the developed pulsed-power modulator are the pulsed output voltage, the output current, the pulse repetition rate (PRR), the pulse width, and an average output power of 60 ㎸ max , 300 A max , 3000, 50 ㎲, and 15 ㎾, respectively. The pulsed-power water treatment system was introduced and analyzed using an equivalent electrical circuit model to optimize the output voltage waveform. The experimental results verify that the proposed water treatment system can be effectively used for industrial applications.

A comparative study of the gate driver circuits for series stacking of semiconductor switches

For the high voltage semiconductor switch based pulsed power application, series operation of semiconductor switches is generally required because of limitation of device ratings. However, there are many considerations to design gate driver circuit for stacking the IGBTs because of the complexity and difficulty of synchronization and protection. Gate driver circuit of series connected IGBTs usually requires high number of high voltage insulated gate power source and complex gate signal schemes depending on the total number of switches. Furthermore, since it is difficult to synchronize switching operations, complex protection circuit should be employed to protect semiconductors switches from arc or short circuit condition which is frequently generated during normal operation of pulsed power application. The purpose of this study is the introducing of the simple and reliable gate driver circuits for series connected semiconductor switches based on the expected problems and considerations. The advantages of each driver circuit are analyzed based on comparative study of proposed gate driver circuits with PSpice simulation. By combining driver circuit with 12 series connected IGBT stack for 10kV pulsed modulator, the various kinds of testing were performed including normal operation and arc or short condition. The experimental results is confirmed that proposed gate driver circuit can be effectively used at semiconductor based pulsed power modulator.

Design and analysis of series resonant converter for 30kW industrial magnetron

This paper deals with the design and analysis of 42kW (14kV, 3A) high voltage power supply for 30kW industrial magnetron. The developed high voltage power supply was designed based on the series resonant converter discontinuous conduction mode (DCM) to takes advantage of the superior arc protection because of their current source characteristic. The detail design procedure for resonant tank and high voltage transformer with respect to the input and output specifications is described based on the basic analysis of DCM series resonant converter. A comparative study with theoretical equations, simulation and experimental results was given. It provides the output voltage and current characteristics with variable switching frequency and verifies the advantage of this topology such as the function of arc protection without any additional protection circuit and high efficiency because of the zero current or zero voltage switching. Also, the developed power supply was tested with 30kW magnetron and the results prove the reliability and robustness of proposed scheme.