Chan-Hun Yu

Gate Driving Circuit With Active Pull-Down Function for a Solid-State Pulsed Power Modulator

This paper proposes a new gate driving circuit for the solid-state pulsed power modulator (SSPPM) based on semiconductor devices. The proposed circuit can be easily implemented by applying a short gate signal to the bypass insulated gate bipolar transistor (IGBT), i.e., switches connected in parallel with the load instead of a pull-down resistor. The IGBT_BPs are turned on at the end-point of the pulse. It can quickly discharge the pulse voltage applied to the load. In addition, it can operate as bypass diode, which is used to protect the semiconductor switches when the gate signal malfunctions, by using the antiparallel diode of the IGBT. Moreover, power loss in the pull-down resistor used to achieve fast falling pulses can be eliminated by turning off the IGBT while applying the pulse state. Thus, the proposed circuit can be used for implementing SSPPM with small values of falling time and high efficiency. The circuit configuration, operational principle, relevant analysis results, and a PSpice modeling are presented and verified by the 10-kV SSPPM.

Trapezoidal Approximation of LCC Resonant Converter and Design of a Multistage Capacitor Charger for a Solid-State Marx Modulator

This paper describes the circuit of a capacitor charger for a solid-state Marx modulator. A high-efficiency LCC resonant inverter is proposed for the simultaneous charging of many capacitors in parallel using a multistage transformer and rectifier. Using a high-voltage insulation cable, the charging loop, which represents the primary winding of transformer, is implemented to transfer the power from the resonant inverter to each stage. In addition to the simultaneous charging of separate capacitors, the advantages of the proposed circuit and structure include compact design and reliable insulation performance against high-voltage pulses. Based on the relevant approximation, the simplified analysis of an LCC resonant converter with a trapezoidal shape of resonant current is provided and a 50-kW high-voltage capacitor charger is designed for a 40-kV solid-state Marx modulator. The power stage, which consists of a transformer with four voltage-doubled rectifiers, is designed, and six power stages are configured for generating a pulse output of 40 kV. The detailed implementation of the multistage transformer and rectifier is presented in accordance with the design requirements of a high voltage modulator. Finally, the developed charger achieves 96% of the maximum efficiency and 0.96 of the maximum power factor. The experimental results verify that the proposed circuit and structure can be effectively used for a solid-state Marx modulator.

Simplified Design of a Solid State Pulsed Power Modulator Based on Power Cell Structure

This study presents a simplified design for a solid state pulsed power modulator (SSPPM) based on a power cell structure. Similar to the Marx generator, the power cell structure has advantages such as reliability and modularity. In addition, the proposed SSPPM includes a capacitor charger that is simple and compact. The operating principle of, and the design considerations taken for, the SSPPM are discussed from a practical viewpoint. Based on a reasonable approximation, simplified design equations are developed for a capacitor charger and a high-voltage pulse-switching part, which are comprised of an LCC resonant converter and a power stage, respectively. Accordingly, detailed design procedures are proposed to develop the SSPPM with the following specifications: 40 kV, 20 A, 300 μs, 200 Hz, and 50 kW. The experimental results verify the specifications at the rated operating condition with an efficiency of 92.4%, and also confirm reliable arc-protection performance. Finally, the proposed design methodology, which utilizes simplified equations, can be used for designing an SSPPM based on the power cell structure for extensive applications.

Active droop compensation circuit for solid state pulsed power modulator with long pulse width

In this paper, voltage droop compensation associated with long pulses generated by solid state pulsed power modulator (SSPPM) is discussed. The pulse modulator with proposed compensation circuit can achieve low voltage droop in many applications required long pulse width regardless of load condition by using active droop control. The proposed circuit is composed to current source capacitor charger based on resonant converter and flyback converter for discharging output capacitor. The series resonant converter with discontinuous conduction mode (SRC_DCM) operation is adopted for capacitor charger topology due to two reasons. SRC_DCM has current source characteristic so that it can easily make triangular waveform that is useful to compensate voltage droop. Moreover, voltage gain curve of SRC_DCM is proportional according to switching frequency. It is appropriate for active droop control that requires adjusting output peak voltage linearly according to load condition. For pulling down the output voltage before next pulse applied, the flyback converter is used. It can regenerate output capacitor energy to input capacitor as well as discharging output voltage. The circuit configuration, relevant analysis results, and a pspice modeling are presented and verified by 1kV, 200Hz, 300us prototype.

High voltage pulsed power modulator with high reliability and fast switching speed for medical lasers

This paper discusses a high voltage pulsed power modulator with high reliability and fast switching speed for medical lasers. The proposed circuit can improve reliability by employing a modular structure using bypass devices. Furthermore, since the developed pulsed power modulator utilizes metal oxide silicon field effect transistors (MOSFETs) as bypass devices as well as main switches, it can achieve fast switching speed. Experimental results from a 1 kV and 300 kHz pulsed power modulator is shown to verify the proposed work.

Design of a high efficiency 40kV, 300us, 200Hz solid-state pulsed power modulator with long pulse width

This paper deals with the design of a high efficiency solid-state pulsed power modulator(SSPPM) using semiconductor switches for industrial applications requiring long pulse width. Specifications of the proposed SSPPM are as follows: variable output pulse voltage, 1-40 kV; width, 1-300 us; pulse repetition rate, 1-200 pps; and average output power, 50 kW. The proposed SSPPM mainly consists of high-voltage capacitor charger and stacked switch part for applying pulse voltage to the load including a series of connected 48 pieces IGBT stack. For simultaneous charging of energy storage capacitors, a high efficiency LCC resonant inverter is proposed with multi-stage transformer and rectifier. The stacked switch part is designed based on power cell structure that has many advantages such as voltage balancing between each IGBTs, and reliable operation against synchronization failure of IGBT gate signals. In addition, a novel gate driving is proposed for fast discharging the stored energy from the capacitive load. This gate driving circuit removes pull-down resistor which induces additional power loss and achieves fast falling time. The experimental results of developed capacitor charger shows 95% and 0.96 of maximum efficiency and power factor, respectively. Finally, the performance of the proposed SSPPM is experimentally verified including rated operation, active pull-down operation, and reliable arc protection.