Isolated Gate Driver Research Articles

Design and Testing of Isolated Gate Driver for Cryogenic Environments

Design and Testing of Isolated Gate Driver for Cryogenic Environments

Comprehensive Investigation of Promising Techniques to Enhance the Voltage Sharing among SiC MOSFET Strings, Supported by Experimental and Simulation Validations

This paper comprehensively reviews several techniques that address the static and dynamic voltage balancing of series-connected MOSFETs. The effectiveness of these techniques was validated through simulations and experiments. Dynamic voltage-balancing techniques include gate signal delay adjustment methods, passive snubbers, passive clamping circuits, and hybrid solutions. Based on the experimental results, the advantages and disadvantages of each technique are investigated. Combining the gate-balancing core method with an RC snubber, which has proven both technically and commercially attractive, provides a robust solution. If the components are sorted and binned, voltage-balancing techniques may not be necessary, further enhancing the commercial viability of series-connected MOSFETs. An investigation of gate driver topologies yields one crucial conclusion: magnetically isolated gate drivers offer a simple and cost-effective solution for high-frequency (HF) applications (2.5–50 kHz) above 8 kV with an increased number of series devices. Below 8 kV, it is advantageous to move the isolation barrier from the gate drive IC to an optocoupler and isolated supply, allowing for a simple design with commercially available components.

Electrical and thermal characterization of (250 °C) SiC power module integrated with LTCC-based isolated gate driver

The high-voltage SiC MOSFET power modules enable high-frequency and high-efficiency power conversion. The parasitic inductances induced by traditional packages of this device technology significantly deteriorate device switching performance, especially in high-temperature applications. In this paper, a novel low-cost discrete SMD component gate driver embedded in a SiC MOSFET power module is introduced. A newly integrated packaging structure has been introduced and proved to be efficient in reducing package-related turn-on loss and turn-off parasitic ringing. However, the gate propagation delay and optocoupler on-chip weak output signal in such a structure become limitations for further pushing the operating frequency and the output current level for high-efficiency power conversion. The electrical characterization of low-temperature co-fired ceramic (LTCC) gate drivers is covered. Furthermore, a 1200 V/120A SiC MOSFET phase-leg power module utilizing high-temperature packaging technologies has been developed. The static characteristics, switching performance, and thermal behavior of the fabricated power module are fully evaluated under operating temperature variations of up to 250 °C.

A Novel Isolated Gate Driver Power Supply Method for Self-Powered SiC DC Solid-State Switch Using Thermoelectric Generation

DC switches using power electronics technology are increasingly used in dc power systems. Unlike other typical power electronic equipment, it is difficult for the DC switch to acquire energy from the primary circuit in the long-term closure state without d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> or potential difference. As a result, the gate drivers of the devices in DC switches can only be powered from the ground via a complicated and expensive secondary isolation power supply system. This paper proposes a novel isolated gate driver power supply method based on thermoelectric generation for SiC DC switches. By utilizing the unique high operating temperature of wide-bandgap devices, self-power generation can be achieved through the temperature difference between the device and the environment even without d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> or voltage difference. Following the comprehensive integration of the thermoelectric generator and the radiator, a 1.7kV/400A DC switch prototype capable of long-term steady self-power supply is developed, proving the efficacy of the proposed method.

FPGA-Based Implementation of Reverse Electrical Pulse Stress and Measurement system for Gallium Nitride High-Electron-Mobility Transistors

This paper presents a pulse electrical stress and measurement system of GaN high-electron-mobility transistors based on FPGA to apply the electrical stress accurately in the form of square wave pulses and switch to the measuring state in time. The design processes for the FPGA program, software system, and hardware circuit are discussed. The system uses a bipolar isolated gate driver to apply pulses of electrical stress to the gate of GaN HEMTs. The mode switch circuit is used to switch from “stress mode” to “measuring mode” to realize the measuring of electrical parameters of the device under test after stress. The system can achieve electrical pulse stress and assist in analyzing the degradation mechanism of GaN HEMTs.

Fully Decoupled Current Control and Current Balancing of the Modular Structure for LED Color-Mixing System

For LED color-mixing, the different color LEDs need to be controlled independently, so a fully decoupled current control and current balancing of the modular structure is proposed for LED color-mixing system. The capacitive current-balancing structure is combined with the quasi-boost converter to realize the decoupled current control and current balancing in each module. The capacitive current-balancing structure is based on the relative reactance of the capacitor with respect to the equivalent resistance of the associated LED string. The inductor in quasi-boost converter is used to further stable the output current flowing through each LED string, and the switch in quasi-boost converter for controlling the current of each LED string adopts the parallel connection to protect LEDs from the current-spike caused by the switch. The structure is modularity and scalability so that the different color LEDs can be added and removed easily. Compared with SIMO (Single-Inductor-Multiple-Output) structure, the proposed structure has no cross-coupling issues. The LED string currents working with PWM mode have a good current-balancing performance since the equivalent resistance of LED string is much smaller than the reactance of capacitors. In addition, the resonant capacitors separate the grounds of the power source and LED strings, so all the switches in parallel with LED strings do not need the isolated gate drivers. A prototype with RGB modules has been built and evaluated, and the experimental results have a good agreement with the theoretical analysis.

Design and experiments of isolated gate driver using discrete devices for silicon carbide MOSFET

The high temperature (HT) characteristics of silicon carbide (SiC) devices enable power electronic converters to operate at higher ambient temperature, and the importance of HT isolated gate drivers is becoming increasingly significant. Compared with the complex silicon on insulator (SOI) HT chips and normal silicon (Si) ICs, the Si-based discrete devices can well balance the temperature capability and design cost. A feasible isolated gate driver design method is proposed in this paper by using discrete MOSFETs, discrete BJTs and other passive components with consideration of cost and can be with less leakage current than normal integrated circuits. The function of gate driver includes signal isolation and signal amplification. In the signal isolation part, a CMOS-based isolation circuit is proposed with its merits. In the signal amplification part, normal topologies are improved to get better efficiency and high-speed capability. SiC power module-based double pulse test is used to verify the switching performance, and experiments are done to verify the continuous operating capability. The main factors which affect the performance of the proposed isolated gate driver are summarized. This technology provides a novel solution for SiC MOSFET gate driver in HT environment.

A MHz-Pulse-Transformer Isolated Gate Driver With Signal-Power Integrated Transmission for Medium-Voltage SiC MOSFETs

The conventional isolated gate driver (GD) solution for the medium-voltage (MV) SiC <small>mosfet</small> separates the signal and power transmissions and requires a bulky GD power supply (GDPS). This article presents a signal-power integrated GD for MV SiC <small>mosfet</small>s with a compact footprint. The proposed GD transmits both the pulsewidth modulation (PWM) signal and GD power by 20-MHz modulated class-E resonant flyback converters, where the transmitted GD power can maintain constant within the full PWM duty-cycle range (i.e., 0&#x0025;&#x2013;100&#x0025;). In addition, the PWM signal transmission of the proposed GD achieves a low total propagation delay time &lt; 75 ns by utilizing the fast transient of 20-MHz RFCs and the edge-based envelope detector. A printed-circuit-board-based coreless transformer is integrated into the proposed GD to achieve an insulation voltage higher than 10 kV_RMS and a low coupling capacitance of 5.85 pF. The common-mode transient immunity of proposed GD is higher than 100 V&#x002F;ns, which is beneficial to drive MV SiC <small>mosfet</small>s with high <i>dv&#x002F;dt</i>. The proposed GD does not require additional GDPSs nor fiber-optics, which achieves a smaller size compared to conventional isolated GDs and is promising to be integrated into SiC <small>mosfet</small> module packages. Experimental results on 3.3 kV and 10 kV SiC <small>mosfet</small>s are provided to validate the effectiveness of the proposed GD.

Forward converter using a resonant auxiliary circuit to provide soft‐switching and reset the magnetic core

In this paper, a new ZVT forward converter is presented in which the third winding of the forward converter is utilised to transfer power from the input to the output, recover the energy of the leakage inductance and snubber capacitance, and also provide ZVS condition for the converter switch. In the proposed converter, the main switch is turned ON and OFF under ZVS condition, and the auxiliary switch operates under ZCS condition. Besides, all the diodes are turned OFF under ZCS condition, and their reverse recovery losses are alleviated. Moreover, in the proposed converter, the voltage stress of the auxiliary switch is limited to the input voltage. As a result, the efficiency is improved. Since both converter switches and the input voltage share the same ground, no isolated gate driver is required in the implementation of the introduced converter. Also, due to the almost flat efficiency curve of the proposed converter, it is suitable for applications where the load range is wide. The proposed converter analysis, operating principals and design considerations are discussed in this paper, and the converter performance is justified by the implementation results from a 240 W prototype converter.

Electrical characterization of a 1200V GaN HEMT at cryogenic temperatures

The cryogenic operation of power converters integrated with the superconducting electric machines can leverage the lower parasitic, lower core material, and insulation requirement to reduce weight and increase power density in aerospace applications. To that end, Gallium Nitride High Electron Mobility Transistor (GaN HEMT) has recently proven to be the most viable option for the cryogenic converter operation. However, the topology selection and optimization are greatly influenced by the current/voltage rating of the power devices. Although series connected HEMTs can increase the blocking voltage, the dynamic voltage imbalance issue stemming from device parameter fluctuations, the larger number of required isolated gate driver makes the need for single high blocking voltage devices more compelling. This is even more pronounced in GaN due to its higher operating frequency which stems from the lower input capacitance. Although 900V cascode GaN HEMTs are now commercially available, single-chip high voltage HEMTs are attractive due to their zero reverse recovery charge, and lower package bonding parasitics. In this paper, a 1200V enhancement-mode GaN HEMT from GaNPower International has been characterized at cryogenic temperature. A 63% decrease has been demonstrated in the on-resistance, Rds(on) from room temperature to -150°C. The threshold voltage shows a 1.2x increase from room temperature to cryogenic temperature (-178°C). The transconductance (Gfs) shows a 1.34x increase for a temperature difference of 175°C. The results translate to a lower conduction loss and a faster switching speed and unfold further possibility of GaN in cryogenic converter applications.

Soft Switched Flyback Converter Using Active Lossless Snubber

In this paper, a new active lossless snubber circuit is proposed which provides soft switching condition for the traditional pulse width modulation (PWM) fly-back converter. This active lossless snubber circuit creates Zero Voltage Switching (ZVS) condition for the main switch, while Zero Current Switching (ZCS) condition is achieved for the auxiliary switch. Moreover, based on soft-switching condition, diode reverse recovery problem is omitted that leads to reduction of switching losses and increased efficiency. Also, the voltage stress of the auxiliary switch is clamped to the input voltage level which leads to its low capacitive turn ON loss. Furthermore, the presented active lossless snubber circuit provides soft-switching condition independent of load condition. The main and auxiliary switches do not need isolated gate driver, since their source pins are connected to the input ground. In this manuscript, the different operating modes are explained in details and also, a comprehensive design procedure is presented. Furthermore, loss breakdown for converter elements is offered at full load. The simulation results of the proposed converter using PSPICE software are shown for 155V input, 24 V, 120 W output and 100 kHz switching frequency to justify the theoretical analysis. The proposed converter has a high efficiency of 94.08% at full load.

Development of Miniaturized Monolithic Isolated Gate Driver

Development of Miniaturized Monolithic Isolated Gate Driver

Investigating the Shielding Effect of Pulse Transformer Operation in Isolated Gate Drivers for SiC MOSFETs

Wide-bandgap technology evolution compels the advancement of efficient pulse-width gate-driver devices. Integrated enhanced gate-driver planar transformers are a source of electromagnetic disturbances due to inter-winding capacitances, which serve as a route to common-mode (CM) currents. This paper will simulate, via ANSYS Q3D Extractor, the unforeseen parasitic effects of a pulse planar transformer integrated in a SiC MOSFET gate-driver card. Moreover, the pulse transformer will be ameliorated by adding distinctive shielding layers aiming to suppress CM noise effects and endure high dv/dt occurrences intending to validate experimental tests. The correlation between stray capacitance and dv/dt immunity results after shielding insertion will be reported.

A Study of Integrated Signal and Power Transfer for Compact Isolated SiC MOSFET Gate-Drivers

This work discusses a novel set of alternate implementations of isolated gate driver circuits for power electronic transistors. The proposed topologies for the driver have been designed specifically for SiC power MOSFET. Three different solutions are discussed, all of them providing the required gate turn-on and turn-off command signal with galvanic isolation, but also supplying power to the secondary side of the driver by means of magnetic transformers. The resulting solutions, all of them implemented with simple circuitry, enable the integration of the driver into the power cell, allowing for theoretical higher power density values in the final system. The principle of operation of the different solutions is discussed, and then the main relevant implementation details are presented. After that, the operation of the circuits is demonstrated experimentally, by testing a set of prototypes of these drivers. This provides a comprehensive design example that assesses the feasibility of the proposed solutions. Finally, the main results of the performance of the three gate drivers, on an SiC MOSFET-based prototype are presented and compared.

Isolated Ultrafast Gate Driver with Variable Duty Cycle for Pulse and VHF Power Electronics

Ultrafast and isolated gate drivers advance the development of pulse and very high frequency power electronics for applications that include LiDAR, space systems, miniaturized hardware, and testing of emerging ultrafast devices. The isolated ultrafast gate driver in this letter achieves a gate voltage slew rate above 12 GV/s with rise and fall times below 260 ps with the proper choice of components. Magnetic isolation provides transient immunity and positive feedback enables dynamic dc restoration to allow arbitrarily long on - and off -times and preserve variable duty cycles. With the isolated ultrafast gate driver, an EPC 2038 GaN FET achieves a drain voltage slew rate of over 37 GV/s when hard-switching and improves total efficiency by 8% (including gating loss) with a careful choice of logic inverters in a symmetric 100 MHz current-mode class D (CMCD) wireless power transfer system. The ultrafast gate driver with isolation and positive feedback was implemented with a commercial radio frequency signal transformer and discrete logic inverters and validated in a hard-switching double pulse test, a narrow pulse test repeating at 165 MHz, and a 100 MHz soft-switching CMCD resonant converter.

Isolated Gate Driver for Medium-Voltage SiC Power Devices Using High-Frequency Wireless Power Transfer for a Small Coupling Capacitance

A high-voltage operation and breakneck switching speed of medium-voltage (MV) silicon carbide (SiC) devices demand gate drivers (GDs) with high voltage withstanding capability, high common-mode (CM) transient immunity and a reliable short-circuit protection. An isolated GD to meet these challenging requirements is presented in this article. A novel isolated gate driver power supply using high-frequency wireless power transfer (WPT) with a nonoverlapped winding arrangement for a small coupling capacitance is proposed. Moreover, a grounded shield is added to further reduce the effective coupling capacitance and the CM current. The receiver (Rx) coil of the WPT system along with its power processing circuit have been epoxy encapsulated to achieve a very high breakdown voltage and an extremely small form factor without violating very demanding clearance and creepage distance requirements. The impact of epoxy, winding arrangement, Rx circuits, and the grounded shield on the coupling capacitance is analyzed in details. In addition, a sophisticated overcurrent protection (OCP) scheme with soft-turn-off capability for MV SiC devices is developed. The designed OCP scheme achieves fast protection and simultaneously avoids false tripping due to very high current overshoot associated with the MV SiC devices during turn-on transitions. An experimental prototype is developed and the performance of the proposed GD under various operating conditions is evaluated experimentally.

Design of symmetrical half-bridge converter with a series coupling capacitor

Purpose With the advancement of technology, size, cost, and losses of the switched mode power supply (SMPS) have been decreasing. However, due to the high frequency switching, design of magnetic drives and isolation circuits are becoming a crucial factor in SMPS. This paper presents design criteria, procedure and implementation of AC-DC half bridge (HB) converter with lower cost, smaller size and lower voltage stress on the power switch. Design/Methodology/approach The HB converter is designed in a symmetrical mode with a series coupling capacitor. Isolated power supplies are used for the converter and control circuit. Further, a transformer based isolated gate driver is used to drive both MOSFETs. The control IC works in voltage control mode to regulate voltage by controlling the duty cycle of the MOSFETs. Findings Control characteristics and performance of the HB converter is simulated using the MATLAB software and prototype of 170 W HB converter is built to validate the analytical results under variable load current and source voltage. The power quality and variation of load voltage at 2 A, 5 A, 7 A are reported. Originality/value This paper presents the design of a low-cost HB converter in a symmetrical mode which saves the additional cost of symmetric correction circuit normally required in asymmetrical mode design. This paper also focuses on the selection of primary and secondary side switch, series coupling capacitor, commuting diode, isolated drive and charge equalizer resistor.

A High-Input Voltage Two-Phase Series-Capacitor DC-DC Buck Converter

A high-input voltage 2-phase series-capacitor (2-pscB) DC-DC buck converter is theoretically analyzed, designed, and implemented. A new design approach for an automatic current sharing scheme was presented for a 2-phase series-capacitor synchronous buck converter. The series-capacitor voltage is used to achieve current sharing between phases without a current sensing circuit or external control loop as each phase inductor charges and discharges the series capacitor to maintain its average capacitor voltage constant. A novel isolated gate driver circuit to accommodate an energy storage capacitor is proposed to deliver isolated gate voltages to the switching transistors. An I2 control scheme that uses only one feedback path control for the four gate drivers is proposed to enable higher voltage conversion. An experimental 110-12 V 6 A load prototype converter was designed, and its current sharing characteristics were experimentally verified.

A Simultaneous Wireless Power and Data Transmission Method for Multi-Output WPT Systems: Analysis, Design, and Experimental Verification

Multiple power outputs are necessary in applications such as isolated gate drivers for multilevel converters or DC motor drive. Meanwhile, efficient and reliable data transfer is also essential to achieve satisfactory control performance. In this letter, a simultaneous power and data transmission method is proposed for multi-output wireless power transfer (WPT) systems. An intermediate unit, formed by two unipolar coils with ferrite cores and an aluminum plate in between for mutual coupling enhancement and coupling area shaping, not only can transfer power to adjacent units but also supply power to local loads. Hence, multiple outputs can be achieved. Then, bipolar coils, placed in overlap with the same-side power transfer coils to form a compact and symmetrical structure, are used to transfer data. Such data transfer coils are naturally decoupled with the power transfer coils, leading to a straightforward design of the data processing circuit. Besides, data can be transferred between adjacent circuit units, which facilitates the monitoring and control of all outputs. The feasibility of the proposed coupling structure and the parallel transmission of power and data are verified on a laboratory prototype with two output voltages, and the transfer distance is 20mm while the output power is 180W. The system efficiency reaches 90%, and the data transfer rate is 19.2kb/s.

Self-Powering High Frequency Modulated SiC Power MOSFET Isolated Gate Driver

A novel implementation of an isolated gate driver for power switches is proposed in this study. The driver is bespoke designed for SiC power mosfet s. The proposal achieves the main driver characteristics—isolation capability, gate switching command, and power transfer to the secondary side by using a unique magnetic transformer. The resulting simple circuitry enables the integration of the driver into the power cell, achieving theoretical higher power density values of the final system. The principle of operation of the driver is described in detail. The original pulsewidth modulation signal is modulated with a pure ac square waveform under a two-level modulation scheme, that guarantees no saturation of the magnetic core. The signal is then magnetically coupled to the secondary side, where it is rectified and reconstructed to effectively drive the target device. In addition, the steps needed to provide a suitable design taking into account the parameters of the target power switch are also detailed. The resulting driver is characterized and a prototype of the driver is built and tested. The main results of the driver performance on a SiC mosfet -based prototype are presented. Based on the analysis of these results, this study experimentally demonstrates the feasibility of the proposal.