Resonant converters featuring soft switching are commonly used in domestic induction heating applications due to their high efficiency and high power density. In this paper, the design and implementation procedure of an improved efficiency and low-profile resonant inverter for induction heating applications is presented. The proposed converter is based on a multi-MOSFET cell implementation, reducing the equivalent on-state resistance per chip-area. By using automotive-grade MOSFET devices, a converter capable of delivering up to 4 kW has been built, reducing conduction losses against the classical IGBT-based converter. In addition to this, the reduced switching times of MOSFET devices decrease switching losses, further increasing the conversion efficiency. The main design challenges including the device selection, gate drive circuit, and cooling have been addressed. As a conclusion, a low-profile implementation without fan and heat sink is obtained, which significantly improves state-of-the-art technology in terms of efficiency and power density.

Multi-MOSFET-Based Series Resonant Inverter for Improved Efficiency and Power Density Induction Heating Applications

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 096 for a full-load condition For the measured charging time of a 4 mF capacitor, with 968 s for 10 kV charging, the average charging current was estimated as 413 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 (096), and reliability with a high power density (820 W/L)

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

The series configuration of fast semiconductor switches seems to be the key component in the high-voltage and fast rising time pulse generation In this approach, two important issues must be considered The first is to provide a safe operating condition for the switches in transient intervals The second is to design a gate drive system with the capability of driving a large number of discrete devices simultaneously The aim of this paper is to obviate these two requirements First, different factors affecting the unbalanced voltage sharing between the series switches are discussed In this investigation, the switch-to-ground parasitic capacitance effect has been recognized as the major effect on the unbalanced voltage sharing in the transient interval Two schemes for abating this effect are proposed To solve the unbalanced voltage distribution, the structure with a snubber circuit in the clamp mode operation is suggested This scheme can be used for any number of switches without destructively affecting their behavior In addition, the output pulse with a fast rising time could be obtained by the proposed gate drive system In order to evaluate the operation of the proposed structure, a stacked switch with the voltage capability of 36 kV is tested experimentally The characteristics of the obtained pulse are the fast rising time (695 ns) with the dV/dt of 460 kv/ $\mu \text{s}$ and the wide range of the pulsewidth adjusting to 05–15 $\mu \text{s}$  In addition, the voltage variance of the switches level in the series structure is about 10%

A Fast and Series-Stacked IGBT Switch With Balanced Voltage Sharing for Pulsed Power Applications

This paper describes the design of a robust high-voltage solid-state pulsed power modulator (SSPPM), which requires reliable series stacking and driving of a number of semiconductor switches. For voltage balancing against overvoltage during both at transient and at steady-state, the power-cell-based modular stacking structure consists of an energy storage capacitor, bypass diode, and switching device (such as an insulated-gate bipolar transistor or a metal-oxide-semiconductor field-effect transistor (mosfet)). In addition to the reliable voltage balancing of each switching device, the modular power cell stacking structure provides a fault-tolerant design by allowing individual protection circuit for each switching device. In this paper, the inclusion of a compensating third winding is proposed. This compensating third winding solves the voltage unbalance issue, which results from difference of leakage inductance of separate located transformer core, using magnetic flux compensation. A protection method using this compensating winding is also suggested to detect abnormal occurrences in each power cell under operating conditions. Additionally, an arc current protection circuit to ensure continuous operation of the SSPPM is designed. Through simulation and experimental results of tests on the SSPPM with the structure outlined earlier, it is verified that the proposed design can be used effectively, as it exhibits both robustness and reliability.

Robust Design of a Solid-State Pulsed Power Modulator Based on Modular Stacking Structure

This paper describes the design, implementation, and comparison of high-voltage capacitor chargers for a solid-state pulsed power modulator (SSPPM). The three different converter topologies are a series resonant converter operating at a discontinuous conduction mode with switching frequency control (SRC_DCM_SFC), a series resonant converter operating at a continuous conduction mode with phase shifted pulse width modulation control (SRC_CCM_PSPWMC), and a series-parallel resonant converter operating at the CCM with SFC (SPRC_CCM_SFC). On the basis of these converter topologies, 10-kWaverage high-voltage capacitor chargers are designed for the three types of SSPPMs, which have the following maximum output specifications: 1) SRC_DCM_SFC: 60 kV, 300 A, 3 kpps, and 50 μs; 2) SRC_CCM_PSPWMC: 10 kV, 50 A, 50 kpps, and 10 μs; and 3) SPRC_CCM_SFC: 40 kV, 150 A, 7 kpps, and 10 μs. Although the pulse output specifications are different, it is worth comparing the resonant inverter topologies and the control methods from the viewpoint of the losses, control characteristics, and merits and demerits of the high-voltage capacitor chargers. From the analysis and investigation of the three resonant inverters, the design procedure, including the determination of the resonant tank parameters, is provided, which considers the design of the high-voltage capacitor charger. PSPICE simulation is used to elucidate the effects of the resonant tank structure and its parameters, and the resonant current waveform and losses of the Insulated Gate Bipolar Transistor are compared. Finally, experiments for each charger are performed under various load conditions, and the comparison results of the three capacitor chargers, including the conduction and switching losses, control characteristics, and overall efficiency, are discussed in this paper.

Design and Comparison of Capacitor Chargers for Solid-State Pulsed Power Modulator

This paper describes a novel 10kW (10kV, 1A) high voltage capacitor charger which has the combined advantage both series loaded resonant inverter and ZVS full-bridge PWM inverter Series loaded resonant inverter has a wide ZV or ZC switching range regardless of load condition However it can generate audible noise at light load condition and requires careful filter design because it should be controlled by variable frequency On the other hand, ZVS full-bridge PWM inverter can be controlled by phase delay of each switching signal with fixed switching frequency, but when it is working at light load condition, efficiency will be decrease because of loosing soft switching condition The proposed charger has the same structure like series resonant inverter, and controlled at fixed frequency by way of phase shifted PWM The operational principle of proposed charger and soft switching mechanism is analyzed The developed charger is verified to have higher efficiency at light load condition and higher power density by way of simulation and experiments Developed charger and 10kV IGBT stack based solid state pulsed power modulator was combined and tested with various load conditions The experimental results verified that the proposed charger can be used effectively for high voltage pulsed power modulator which requires the various kinds of load condition with respect to the applications

Novel high voltage capacitor charger for pulsed power modulator

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.

S. R. Jang

Papers

Novel high voltage capacitor charger for pulsed power modulator

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