Voltage Clamp Circuit Research Articles

A Secondary-Side Phase-Shifted Bidirectional Soft-Switching DC–DC Converter Employing Step Voltage Switching for Eliminating Device Voltage Overshoot

This paper presents a modulation strategy for bidirectional power flow for the step voltage switched (SVS) secondary side phase-shifted (SPS) DC-DC converter that eliminates the device voltage overshoot problem. The voltage overshoot problem arises due to the resonance between transformer leakage inductance and the output capacitance of the current-fed side MOSFETs of the converter. Many snubber/clamp circuits were discussed in the literature to suppress this voltage overshoot. But the power loss in these clamp circuits will affect the converter efficiency. The bidirectional SVS SPS DC-DC converter presented in this paper eliminates the voltage overshoot problem instead of suppressing it and therefore nullifies the need for a voltage clamp circuit. And most of all switching devices undergo soft-switching (either ZVS or ZCS). These factors result in achieving a peak efficiency of 96%. The proposed topology is tested for 1.7KW at 100KHz switching frequency with voltage-fed side voltage being 72V and current-fed side voltage of 400V. The results obtained prove the feasibility of the proposed work.

Surge Current Interruption Capability of Discrete IGBT Devices in DC Hybrid Circuit Breakers

The power electronic interrupter (PEI) determines the current interruption rating of the dc hybrid circuit breaker (HCB). This paper deals with discrete insulated gate bipolar transistor (IGBT) based PEI modules. The influence of the voltage clamping circuit (VCC) on the surge current interruption capability (SCC) of the discrete IGBT is unveiled for the first time. Two commonly used VCC configurations are considered: a purely MOV based voltage clamp and an MOV-RC combination clamp designated as type I and type II PEI modules respectively. Comprehensive measurements are used to analyze the device turn-off behavior under each PEI module type to determine their limitations as well as their failure modes. The type I PEI is limited by the turn-off thermal stresses arising from the hard switching dynamics. The type II PEI, on the contrary, has the potential to achieve lower turn-off energy among other benefits but exhibits a unique failure mode during the tail current stage. Therefore, static and mixed-mode Technology Computer-Aided Design (TCAD) device simulations are introduced to provide further insights into the internal processes that alter the type II turn-off and in turn explain the failure mechanism. Finally, the influence of the various circuit parameters on the turn-off process are evaluated and methods to enhance the SCC of the IGBT based PEI are presented.

A Nine-Level Inverter with Adjustable Turn-Off Time for Helicopter Transient Electromagnetic Detection.

The current inverter is the core component of the helicopter transient electromagnetic (HTEM) detection system. It should meet the concerns of low loss, high power, and fast turn-OFF time. This article proposes a new circuit topology based on nine-level inverter technology to overcome the drawbacks of typical PWM (pulse width modulation) inverters, such as switching losses and harmonics. This circuit topology overcomes the shortcomings of the traditional single constant voltage clamp circuit in which the turn-OFF time is not adjustable. Using an inverter with the proposed topology is able to avoid the complex PWM control method and switching loss. In this way, the current rising edge and falling edge of this inverter are also improved effectively. The proposed inverter has adjustable turn-ON-time and turn-OFF time, which is significantly different from the conventional single-clamp inverter. Through subsequent experiments, the inverter proved to have the capability of generating trapezoidal current waveforms. Moreover, by modifying the FPGA (Field Programmable Gate Array) control program, three different turn-OFF times are achieved. The nine-level inverter has a peak current of 1.5 A with an adjustable turn-OFF time from 129 μs to 162 μs. Moreover, the switching frequency of the inverter is reduced from 10 kHz to below 100 Hz. The experimental results further demonstrate that it achieves lower switching losses and more flexible transmission. Our work in this article provides an efficient way to improve the performance of HTEM detection systems.

An optimized multi-modular resonant switched capacitor converter

The switched capacitor converters have the advantages of high efficiency and high power density, which are widely used in data centers, distributed photovoltaic power generation, and other fields. In this paper, an optimized multi-modular resonant switched capacitor converter (MMRSCC) is proposed for an intermediate bus converter in the power supply system of data centers. By removing the inductance of part of the coupled resonant circuit, the converter can eliminate the influence of the parameter difference of passive components, and no additional voltage clamp circuit is needed, which improves the power density. At the same time, the half-bridge with the same switching action on the rectifier side is combined into one, which reduces the number of switching devices and is more conducive to improving the voltage conversion efficiency. In addition, the inductor of the basic unit of the resonant switched capacitor with the same state is shared to reduce the volume of the passive device, further improve the power density, and optimize the MMRSCC. Finally, the correctness of the topology is verified by simulation on the PLECS.

High step‐up buck–boost DC–DC converter with coupled inductor and low component count for distributed PV generation systems

AbstractThis paper presents a non‐isolated high step‐up buck–boost with a coupled inductor DC–DC converter relevant for distributed photovoltaic (PV) generation systems. The proposed topology can reach high voltage gain through the combination of a buck–boost converter with a coupled inductor. The configuration of the proposed converter allows to achieve a natural voltage clamp circuit for the switch, recovering the energy stored in the leakage inductance of the coupled inductor. Moreover, the converter allows soft‐switching conditions, that is, Zero Current Switching (ZCS) for the diodes and nearly ZCS for the active switch. Also, the proposed converter presents a low component count and common ground connection of the input and output. The proposed converter is evaluated theoretically by the principle of operation in continuous‐conduction mode (CCM) and discontinuous‐conduction mode (DCM), voltage gain derivation, external characteristics, semiconductor voltage stress, current stress, and design guidelines. Finally, a 650‐W, 36/380‐V, 50‐kHz prototype was built in the laboratory to experimentally evaluate the proposed converter, which reached a maximum efficiency rate of 96.58%.

Capacitor Clamped Coupled Inductor Bi-Directional DC-DC Converter with Smooth Starting

In this paper, a new type of capacitor clamped coupled inductor bidirectional DC–DC converter is proposed, which offers high voltage gain with smooth starting current transients, as well as reduced stresses on the capacitor. Steady state operation, mathematical modelling, and state space modelling for the proposed converter are presented in detail. A simplified single voltage clamped circuit is developed to mitigate the voltage spikes caused due to the coupled inductor by recovering the leakage energy effectively. Moreover, the clamping capacitor helps in reducing the ripples in output voltage, which in effect significantly reduces the stress on the switch and offers less ripple content at the load terminals. Simulation of the proposed converter is carried out using Simulink/MATLAB for the conversion of 24V DC to 200V DC. For this conversion, simulation results have proven that there is reduction of 13.64% of capacitor voltage stresses. Further, under line varying conditions, converter responses have proven that there is a 119% and 25.25% reduction in input current and output voltage transients, respectively. Similarly, 25.25% and 76.5% transient reductions of input current are observed for line and control parameter variations. The hardware investigation of the converter was carried out with a 100 W, 24 V/200 V setup. The converter achieved efficiency of 93.8%. The observations supplement the simulation results.

Integrated Multi-Port Flexible Voltage Clamp Circuit Breaker with Dc Chopper Applied to the Receiving End of Mmc-Hvdc System

Integrated Multi-Port Flexible Voltage Clamp Circuit Breaker with Dc Chopper Applied to the Receiving End of Mmc-Hvdc System

High-Performance Isolated Gate-Driver Power Supply With Integrated Planar Transformer

Wide-bandgap and silicon power semiconductor devices require advanced pulsewidth gate-driver capability to successfully convert power for high-performance operation. In this article, a simplified forward isolated resonant converter structure with an integrated planar transformer is proposed, a cost-effective solution which eliminates the need of an output filter inductor while rearranging the clamp circuit for reduced component ratings and voltage stress. The first design option uses a simple back-to-back Zener diode voltage clamp circuit for low-power dc–dc isolated power supply applications. The second design employs a lossless voltage-clamped converter with auxiliary energy-recovering winding with an application example for an isolated gate-driver power supply. Through analysis of the converter, the switching frequency has been selected in relationship to the transformer inductance and the equivalent circuit capacitance for the benefit of soft-switching power device transitions. The proposed resonant converter structure features an integrated planar transformer designed with a specific layer disposition to ensure low interwinding capacitance. The converter offers isolated supplies for a gate-driver power devices pair, such as half-bridge SiC devices. The simulation and experimental results are obtained from a gate-driver application platform to demonstrate the validity of the proposed isolated dc–dc converter design and integrated planar transformer with a total conversion efficiency of 87.7%.

An Improved Voltage Clamp Circuit Suitable for Accurate Measurement of the Conduction Loss of Power Electronic Devices.

Power electronic devices are essential components of high-capacity industrial converters. Accurate assessment of their power loss, including switching loss and conduction loss, is essential to improving electrothermal stability. To accurately calculate the conduction loss, a drain–source voltage clamp circuit is required to measure the on-state voltage. In this paper, the conventional drain–source voltage clamp circuit based on a transistor is comprehensively investigated by theoretical analysis, simulations, and experiments. It is demonstrated that the anti-parallel diodes and the gate-shunt capacitance of the conventional drain–source voltage clamp circuit have adverse impacts on the accuracy and security of the conduction loss measurement. Based on the above analysis, an improved drain–source voltage clamp circuit, derived from the conventional drain–source voltage clamp circuit, is proposed to solve the above problems. The operational advantages, physical structure, and design guidelines of the improved circuit are fully presented. In addition, to evaluate the influence of component parameters on circuit performance, this article comprehensively extracts three electrical quantities as judgment indicators. Based on the working mechanism of the improved circuit and the indicators mentioned above, general mathematical analysis and derivation are carried out to give guidelines for component selection. Finally, extensive experiments and detailed analyses are presented to validate the effectiveness of the proposed drain–source voltage clamp circuit. Compared with the conventional drain–source voltage clamp circuit, the improved drain–source voltage clamp circuit has higher measurement accuracy and working security when measuring conduction loss, and the proposed component selection method is verified to be reasonable and effective for better utilizing the clamp circuit.

A reliable voltage clamping submodule based on SiC MOSFET for solid state switch

The electron cyclotron resonance heating system is one of the most effective plasma heating systems for controlled nuclear fusion. The key part of the system called gyrotron is driven by a high voltage power supply with a rated output power of hundreds of kilowatts. When the system is in operation, breakdowns frequently occur in the gyrotron. During breakdowns, the gyrotron will endure a large volume of energy and may be damaged. A solid-state switch is required to protect it by blocking high voltage (∼40 kV) within 10 microseconds and limiting energy within a few joules. Compared with Si IGBT/MOSFET, SiC MOSFET with higher switching speed is more suitable for the switch. However, rapid switching speed exacerbates the voltage imbalance. To solve the problems, a reliable module named Advanced Chopper Sub-Model based on SiC MOSFETs for a solid-state switch is proposed. The module adopts a voltage-clamped circuit to achieve the capabilities of rapid switching-off speed, as well as low overvoltage and good voltage balancing. In addition, modules connected in series can tolerate large driver time delay. The SPICE simulation and the double-pulse test are used to validate the effectiveness of the proposed module. The protection performance test was also conducted by using a spark gap to simulate the breakdown fault. Finally, the switch that consists of 64 series-connected modules has been tested at 30 kV/6A. The turn-off time is ∼5 µs, and the energy during the turn-off transition is 0.283J. The results show that the switch has good performance.

Online Accurate Measurement of Steady-Thermal Resistance of SiC MOSFETs for DC Solid-State Power Controller

The steady-state thermal resistance R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> is the key characteristic of SiC MOSFETs, usually used as a failure indicator. Due to the operating mode of SiC MOSFETs in the dc solid-state power controller (dc-SSPC), the junction temperature measurement based on the steady on-state resistance R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dson</sub> of SiC MOSFETs is vital to the accurate online measurement of R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> . The accuracy of a digital oscilloscope is limited by its analog-to-digital converter; therefore, a drain-source voltage clamp circuit (DVCC) needs to be employed for the accurate online R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dson</sub> measurement. However, conventional DVCCs are unsuitable for either the use over a wide range of operating temperature T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">w</sub> or the integration into the dc-SSPC due to their bulk package. Therefore, in this article, a new design of DVCC is proposed that commonly used small-sized components can be easily integrated into the dc-SSPC with a little impact on its overall volume and can accurately perform the online R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dson</sub> measurement. The experimental results verify the high R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dson</sub> measurement accuracy (<; 0.6%) of the proposed DVCC over a wide T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">w</sub> range (25-100 °C), as well as, the accurate online measurement of R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> with an accuracy of 2.3%. The application of the proposed DVCC in the accelerated power cycling tests highlights its potential in the lifetime prediction.

High-performance single-input three-output DC–DC high gain converter for fuel cell-based electric vehicles

The electric vehicle (EV) requirement has various glitches and solutions in EV technology. Alternate energy that delivers the required power to the EVs is derived from the fuel cell with high performance. Nevertheless, the output voltage obtained from the fuel cell system is very less, and it is not enough to drive the motor of the EVs. The DC–DC converter increases the output voltage of the fuel cell system, and the EV also requires a different output voltage for the entire system. The DC–DC converter for fuel cell-based EVs requires high voltage gain with high conversion efficiency. However, the converter based on single-input three-output (SITO) DC–DC unidirectional converter can reduce loss and the cost of the system, and hence the overall efficiency. In this paper, a new single power-switch-based SITO converter topology is proposed to improve the voltage gain and conversion efficiency. The converter presented in this paper acts as a front-end DC–DC converter for the DC–AC inverter, and it supplies power to the auxiliary DC loads or for charging the auxiliary battery in EV. The converter has a single-stage voltage multiplier cell with a voltage clamp circuit to improve the voltage gain with soft-switching to reduce the loss, and hence the efficiency. The proposed converter is operated with a single MOSFET switch which delivers three different output levels with less voltage stress across the switch is the main feature of the proposed converter. The theoretical analysis is validated through the experimental results, and results verify that the proposed converter is best suitable for EV applications.

Drain–Source Voltage Clamp Circuit for Online Accurate ON-State Resistance Measurement of SiC MOSFETs in DC Solid-State Power Controller

To obtain the online ON-state resistance ( ${\text{R}}_{\mathrm {dson}}$ ) of the SiC power MOSFET, during its operation in the dc solid-state-power controller (dc-SSPC), the drain current ( ${\text{I}}_{d}$ ) and the ON-state voltage ( ${\text{V}}_{\mathrm {dson}}$ ) need to be accurately measured in real time. Compared to that of ${\text{I}}_{d}$ , the measurement of ${\text{V}}_{\mathrm {dson}}$ needs to solve more problems, i.e., the high accuracy, the influence of the operating temperature ( ${\text{T}}_{w}$ ), and the high OFF-state voltage. The drain–source voltage clamp circuit (DVCC) can be accurately used to measure ${\text{R}}_{\mathrm {dson}}$ at low operating temperatures. However, the SiC power MOSFETs, owning the low ${\text{R}}_{\mathrm {dson}}$ characteristics, in the dc-SSPC often operate at the high ${\text{T}}_{w}$ . Under this high ${\text{T}}_{w}$ , the existing DVCCs cannot perform well and give inaccurate measurements of ${\text{V}}_{\mathrm {dson}}$ in real time. Therefore, this article presents an innovative design of the DVCC with improved real-time measurement accuracy ( ${\text{T}}_{w}$ range (25 °C–100 °C). The DVCC is analyzed and tested by integrating into a dc-SSPC for measuring the online ${\text{R}}_{\mathrm {dson}}$ of the SiC power MOSFET at the high ${\text{T}}_{w}$ of 100 °C. The experimental results validate the accuracy of the proposed DVCC-based measurement method and highlight the potential for its use in the accurate junction temperature measurement.

A Self-Powered 50-Mb/s OOK Transmitter for Optoisolator LED Emulation

Isolators are used to eliminate ground loops, and also to protect circuits that are sensitive to high voltages. Optoisolators are normally deployed for these purposes, but they suffer from several limitations, such as low speed of operation and temperature instability. In this paper, an ON-OFF keying (OOK) transmitter (TX) is designed so as to emulate and serve as an alternative to optoisolators, without significant changes to the rest of the system. The TX primarily consists of a voltage clamp circuit to convert input current into voltage, a discharge circuit to avoid metastability, and a 300-700-MHz spread-spectrum (SS) oscillator. The start-up and die-down times of the oscillator are optimized for maximum data speed. SS modulation of the oscillator output restricts radiative emissions to within permissible limits. The TX derives power from the input data (current) signal itself, thereby operating without any external power supply, and supports speeds of up to 50 Mb/s. The TX was fabricated in a BiCMOS semiconductor process and tested using an OOK receiver.

High-Gain Zero-Voltage Switching Bidirectional Converter With a Reduced Number of Switches

A nonisolated bidirectional dc-dc converter has been proposed in this brief for charging and discharging the battery bank through a single circuit in applications of uninterruptible power supplies and hybrid electric vehicles. The proposed bidirectional converter operates under a zero-voltage switching condition and provides large voltage diversity in both modes of operation. This enables the circuit to step up the low-battery bank voltage to high dc-link voltage, and vice versa. The bidirectional operation of the converter is achieved by employing only three active switches, a coupled inductor, and an additional voltage clamped circuit. A complete description of the operation principle of the circuit is explained, and the design procedure of the converter has been discussed. The experimental results of a 300-W prototype of the proposed converter confirmed the validity of the circuit. The maximum efficiency of 96% is obtained at half load for boost operation mode and 92% for buck mode of operation.

A New Measurement Circuit to Evaluate Current Collapse Effect of GaN HEMTs Under Practical Conditions

The gallium nitride transistors suffer from current collapse effect in operation regions, which leads the dynamic ON-resistance to increase when high voltage is applied to the transistor. Dynamic ON-resistance under practical application conditions is also an important factor for the reliability and conduction efficiency of transistors. To measure the dynamic ON-resistance and evaluate the current collapse effect, a softswitching circuit based on synchronous buck topology is proposed in this paper. To apply high-voltage and high-current stresses to the device without additional spikes and oscillation, resonance technique has been employed. As a result, the proposed circuit could produce sufficient power stresses to the devices with general equipment. To achieve accurate measurement of ON-resistance under switching operations and eliminate the saturation of oscilloscope probes, an active voltage clamp circuit is developed. Operation principles and design analysis of the circuit are described in this paper. The dynamic ON-resistance measurement method is illustrated in detail. Furthermore, a prototype circuit has been built. A simulation and experiments were carried out to verify the performance of the system. A comparison of the active clamp circuit with common voltage probes is presented through the measurement results. The experimental results confirm that dynamic ON-resistance can be accurately measured using the proposed circuit and the current collapse effect can be evaluated under practical operation conditions with high precision.

A Fast Voltage Clamp Circuit for the Accurate Measurement of the Dynamic ON-Resistance of Power Transistors

For determining the dynamic on -resistance $R_{{\rm dyn},{\rm on}}$ of a power transistor, the voltage and current waveforms have to be measured during the switching operation. The novel heterostructure wide-bandgap (e.g., AlGaN/GaN) transistors inherently suffer from the current collapse phenomenon, causing the dynamic on -resistance to be different from the static. Measuring voltage waveforms using an oscilloscope distorts the characteristics of an amplifier inside the oscilloscope when the range of the measurement channel is not set wide enough to measure both on -state and off -state voltage levels, resulting in failure to accurately measure the voltage waveforms. A novel voltage clamp circuit improving the accuracy of the transistor's on -state voltage measurement is presented. Unlike the traditional clamping circuit, the presented voltage clamp circuit does not introduce delay caused by $RC$ time constants, keeping the voltage waveform clear, even during state transitions of the device under test. The performance of the presented circuit is illustrated by measurements on a 2-MHz inverted buck converter.

High Step-Up Converter Based on Coupling Inductor and Bootstrap Capacitors With Active Clamping

As generally acknowledged, the high step-up dc-dc converter is widely used in the sustainable energy system as the front-end stage of the dc-ac converter. Therefore, a high step-up converter combining one coupling inductor and two bootstrap capacitors, together with the active voltage-clamping circuit which pumps portion of the leakage inductance energy to the output, is presented herein. By doing so, the efficiency at light load can be upgraded greatly, and hence tends to be flat between the minimum load and the rated load. In this letter, the basic operating principles of this converter are first illustrated in detail, and second some experimental results are provided to demonstrate the effectiveness of the proposed high step-up converter topology.

Constant Voltage-clamping Bipolar Pulse Current Source for Transient Electromagnetic System

This article proposes a bipolar pulse current source for the transient electromagnetic system. This current source consists of a full-bridge converter circuit, a constant voltage-clamping circuit, and a damping-snubber circuit. Bipolar pulses are generated by the full-bridge converter circuit. During the rising edge of the pulse current, the high voltage generated by the constant voltage-clamping circuit is added to the load, which will enhance the rising speed of the pulse current and help the current quickly stabilize. Similarly, for the falling edge, the constant voltage acts on the load, brings out a linear falling edge, and efficiently shortens the turn-off time. The damping snubber circuit is then used to eliminate the ringing happening in the current-reduced-to-zero vicinity. Its operation principles are described, and calculations of the main parameters are also provided. Simulation and experimental results show that the current source has a fast rising edge, a highly linear falling edge, and a short turn-off time, which helps to enhance the transmitting frequency of the current source and the efficiency of the transient electromagnetic system.

DC Bus Voltage Clamp Method to Prevent Over-Voltage Failures in Adjustable Speed Drives

The influences of PWM switching and long cable length on motor insulations have been discussed in numerous papers. This paper investigates their effect on the voltage insulation components inside an adjustable speed drive (ASD). This paper shows that high potential voltage insulation issue may exist on various components inside the ASD and cause earlier failures under very long cable or multiple drive conditions. A system model to describe this phenomenon is described in the paper. A dc bus voltage clamp circuit is proposed to reduce these voltage stresses. The effectiveness of this circuit is verified by both simulation and experimental results.