Active Gate Control Research Articles

A Partial Active Gate Control for Improvement of a Trade-Off Relation Between Surge Voltage and Efficiency in a Three-Phase Inverter

A Partial Active Gate Control for Improvement of a Trade-Off Relation Between Surge Voltage and Efficiency in a Three-Phase Inverter

Junction temperature balance control for paralleled SiC MOSFETs based on active gate control

Power devices operating in parallel often experience thermal stress imbalances, which can lead to failures, especially in silicon carbide (SiC) MOSFETs. To enhance their reliability, controlling the junction temperature becomes crucial. Existing research focuses on addressing current imbalances in parallel devices, neglecting the issue of junction temperature imbalances. It is worth noting that even with balanced currents, the junction temperatures may still vary. To address this challenge, we propose a novel active gate control-based method for achieving junction temperature balance in parallel devices. This method not only ensures junction temperature balance but also effectively suppresses dynamic current peaks. To validate the effectiveness of our approach, we conducted experimental tests on a BUCK converter utilizing two parallel SiC MOSFETs. The experimental results demonstrate the achievement of junction temperature balance and excellent suppression of dynamic current peaks through the proposed method.

Time-Domain and Frequency-Domain Analysis of SiC MOSFET Switching Transients Considering Transmission of Control, Drive, and Power Pulses

Three types of pulses, namely the control, drive, and power pulses, coexist in power electronics systems. The transmission of them embodies the idea to control energy flow with signal flow. However, due to the nonideal performance of the semiconductor switches and the parasitic elements, significant delay and distortion are inevitable during the transmission, causing severe challenges in terms of both device- and system-level performance. Taking silicon carbide (SiC) MOSFET-based system as an example, this article studies the transmission of the three pulses. Time-domain studies are provided first to derive the characteristic parameters of the delay and distortion. Based on the time-domain expressions, a pulse decomposition method is proposed to study the frequency spectrum of the power pulse considering all major transient factors. Experimental results are provided to verify the proposed method and the acquired results. Based on the analyses, the impact of pulse delay and distortion on system performance is summarized, and the general idea of active gate controlling for the power pulse is briefly discussed. This article provides quantitative studies and relevant discussions from the perspective of pulse transmission to improve the analysis, gate-drive design, and active gate control of switching transient.

A Closed-Loop Current Source Gate Driver With Active Gate Current Control for Dynamic Voltage Balancing in Series-Connected GaN HEMTs

The voltage rating of commercial Gallium Nitride (GaN) power semiconductors is limited to 600/650 V because of the lateral structure. Stacking low-voltage switches is an effective way to block higher dc-link voltage. However, unbalanced voltage sharing can occur even with well-matched gate drivers and semiconductors due to the device-to-ground displacement currents. As a result, the low-voltage switches may suffer from over-voltage breakdown. This study presents a novel closed-loop current source gate driver to address the unbalanced dynamic voltage sharing issue. Additional compensation current is actively injected into the switch gate to counteract the voltage imbalance brought by the device-to-ground displacement currents. Compared with the conventional voltage source gate driver-based active gate control method, the proposed current source gate driver tunes the switch turn-off timing and dv/dt more accurately because the switch gate current is directly regulated. Meanwhile, since both the pulse width and amplitude of the compensation gate current can be adjusted, the proposed active gate control is more flexible for adapting to different operating conditions. Moreover, without employing snubber circuits or extra Miller capacitors, the switching speed and switching energy of the GaN devices are not compromised. By implementing the proposed gate driver and voltage balancing schemes, well-balanced voltage sharing can be obtained for both soft-switching and hard-switching scenarios. A series-connected GaN-based multiple pulse tester (MPT) is built to prove the effectiveness of the proposed approach under different load and different switching speed (dv/dt) conditions.

A bidirectional non-isolated hybrid modular DC–DC converter with zero-voltage switching

In this paper, a bidirectional non-isolated hybrid modular DC–DC converter for high-voltage (HV) applications is investigated. In this configuration, conventional Half-Bridge Sub-Modules (HB-SMs) are employed. The proposed DC–DC converter is based on connecting the SMs capacitors in series across the high DC voltage level while connecting them sequentially across the low DC voltage level. On another frontier, an HV valve, based on series-connected Insulated-Gate Bipolar Transistors (IGBTs), is required at the HV side. The main confronted challenge of the series-connected IGBTs is the voltage sharing during turn-on and turn-off periods, which necessitates the engagement of an intricate voltage sharing technique. In this work, a switching pattern is proposed to ensure zero-voltage switching (ZVS) of the involved HV valve. In order to reduce the switching losses and avoid complex active gate control recruited for dynamic voltage sharing, the zero-voltage state is extended beyond the switching time. A detailed illustration of the hybrid modular DC–DC converter is presented, elucidating the proposed switching pattern. Simulation results, using Matlab/Simulink platform, are presented to validate the contribution of the paper. Finally, a scaled-down prototype is employed for experimental verification.

Active Gate Control in Half-Bridge Inverters Using Programmable Gate Driver ICs to Improve Both Surge Voltage and Converter Efficiency

The requirements for peripheral circuits of power converters are becoming more restrictive due to the enhancement of Si-based power devices and due to practical use of SiC device. In the design of modern high-speed switching converters, the stray inductances and capacitances both in the device package and in the gate drive circuit in addition to those in the main circuit of the power converter must be considered. In these situations, the gate driving technique represents the key technology for enhancement of high-speed switching ability of power devices, as there are design limitations to reduce the stray inductances and capacitances. So far, several active gate control methods have been proposed. Most conventional active gate drivers are configured using analog circuits such as transistors and diodes. Thus, it is difficult to reconfigure their control parameters to fit the stray inductances and capacitances after the implementation of power converter and gate circuits. As a solution to these problems, the authors have proposed a programmable gate driver IC, which is a digitally controlled circuit. This gate driver IC can control the gate current at 63 separate levels, operated by programmable fully digital 12-bit and clock signals. In this paper, an active gate current control based on the load current in a half-bridge inverter with two programmable gate driver ICs is demonstrated. This developed gate control is different to the general current feedback control followed the reference value. It is verified that the proposed active gate control can effectively improve the tradeoff relationship between the surge voltage and switching loss of the pulsewidth modulation half-bridge inverter circuit.

Series Connection of Insulated Gate Bipolar Transistors (IGBTs)

High-voltage switches required in present power electronics applications are realized by connecting existing devices in series. Unequal sharing of voltage across series-connected devices can be minimized by using active gate control techniques, snubber circuits, and active clamping circuits. The primary objectives of this paper are to discuss existing voltage-balancing techniques, to present a novel hybrid voltage-balancing technique, and to optimize the number of insulated gate bipolar transistors (IGBTs) in a series string in terms of power losses. The novel voltage-balancing technique can achieve good voltage balancing with a minimum number of components and minimum total losses (i.e., IGBT losses and balancing circuit losses). This technique was validated by both simulation and experimental work. The power loss of a high-voltage switch depends on the voltage-balancing circuit and the number of IGBTs in series and switching frequency. For a given application, the optimum number of IGBTs, in terms of power losses, depends on device characteristics and switching frequency.

Analysis and Comparison of Turn-off Active Gate Control Methods for Low-Voltage Power MOSFETs With High Current Ratings

An analysis and improvement of the switching behavior of low-voltage power MOSFETs with high current ratings is presented. At turn-off, a high overvoltage arises for power MOSFETs. An improvement can be achieved by means of lowering the current slope via the driving stage during switching. Likewise, the current slope can exceed the required limits despite high gate resistances. These problems are of major concern for low-voltage power MOSFETs and can be solved via the driving stage. Thus, turn-off active gate control methods are analyzed and their performance is investigated focusing on reducing the overvoltage at turn-off under the precondition of only a minor increase of switching losses. With only a small number of additional components, a remarkable reduction of turn-off losses is achieved. Thus, these methods are well suited to industrial applications. The control concepts are experimentally compared to a basic gate drive circuit.

An Experimentally Verified Active Gate Control Method for the Series Connection of IGBT/Diodes

The series connection of insulated gate bipolar transistor (IGBT)/diode devices allows the operation at voltage levels higher than the rated voltage of one IGBT/diode. However, due to individual parameter differences of the series-connected IGBT/diodes, it is difficult to ensure a proper voltage balance between them, and transient or steady-state voltage unbalances could cause the failure of these devices. This paper presents an active gate driver developed by the authors that is suitable for the series connection of IGBTs. The proposed active gate driver achieves the transient and steady-state voltage balance between the series-connected IGBT/diode devices. The effectiveness of the gate driver and the active gate control method has been experimentally validated, and promising results have been obtained.

Statistical Approach to Robust Design of Control Schemes for Series or Parallel Connected Power Devices

High power, high speed operation of circuits requires that devices such as IGBTs and MOSFETs be connected in series and/or parallel. Such systems are being increasingly used in high power drives, traction, active power filters and other high power industrial applications. But no matter how perfect the design and fabrication may be, no two devices can be identical, resulting in some level of incompatibility in such systems. Therefore, there is a reduction in the overall reliability unless, care is taken to optimize the parameters of their control schemes which govern the operation of such systems. This paper reports a reliability enhancement scheme for such systems. Example of series connected IGBTs using a current feedback active gate control scheme has been considered in conjunction with the Taguchi method for this purpose. The complete strategy and calculations involved are presented, as are the experimental results to validate theoretical predictions. Results show a significant improvement in performance when the control scheme parameters are optimized using the Taguchi method. A similar approach may be followed for parallel connected devices (e.g. MOSFETs connected in parallel).

Active Gate Control for Current Balancing of Parallel-Connected IGBT Modules in Solid-State Modulators

In modern pulsed power systems, often, fast solid-state switches like MOSFETs and insulated gate bipolar transistor (IGBT) modules are used to generate short high power pulses. In order to increase the pulsed power, solid-state switches have to be connected in series or in parallel. Depending on the interconnection of the switches, parameter variations in the switches and in the system can lead to an unbalanced voltage or current. Therefore, the switches are generally derated, which results in an increased number of required devices, cost, and volume. With an active gate control, derating and preselection of the switching devices can be avoided. In this paper, an active gate control of paralleled IGBT modules, which has been developed for converters with inductive load, is explained in detail and adapted to a solid-state modulator. This paper focuses on achieving a low-inductance IGBT current measurement, the control unit implementation with a field-programmable gate array and a digital signal processor, as well as the balancing of the pulse currents.

Development of a Scalable Power Semiconductor Switch (SPSS)

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents the design and development of a 4800-V, 300-A, 10-kHz scalable power semiconductor switch (SPSS) based on series connecting low voltage insulated gate bipolar transistors (IGBTs). The static and dynamic voltage balance among IGBTs is achieved using a hybrid approach of active clamp circuit and an active gate control that is also effective during tail current phase. The developed SPSS derives its control power directly from the main power bus. Control, packaging, and thermal characteristics are an integral part of the SPSS design. From a user's standpoint, the SPSS is a three-terminal optically controlled high-power switch. Experimental evaluation of the prototype SPSS shows it fully achieved the design objectives. In principle, the approach can be extended to building switches with higher voltages, currents, and switching frequencies, or even with other types of devices than IGBTs. </para>

Review of series and parallel connection of IGBTs

The availability of high power handling devices is of a great importance in the present power electronics industry. These high power ratings can be achieve by connecting existing devices in series or parallel depending on the application. The main problems associated with series and parallel connections are unequal sharing of voltage and current respectively. The active gate control techniques, snubber circuits and clamping circuits are some of the most common methods used to minimise the problem of unequal sharing of voltage and current. The aim of the paper is to review the available techniques to minimise the problems in series and parallel connections of insulated gate bipolar transistors.

Active gate control of series connected IGBTs using positive current feedback technique

Controllable devices like insulated gate bipolar transistors (IGBTs) are very popular on account of their highly desirable features. This prompts their use in high-voltage applications. But high-voltage IGBT development is facing constraints and there is a requirement for series connection of these devices to enhance their voltage withstanding capability. The series connection of IGBTs, however, has its own problems (e.g., dynamic voltage imbalances leading to device break down etc.). Active gate control offers a good solution to this problem. In this brief, a novel scheme of active gate control using a positive current feedback is proposed. The system uses a current feed back network where the gate voltage is dependent on the current through the device but not on the overvoltage across the device (the existing trend). The scheme has been simulated using PSPICE and validated experimentally. Analytical and control aspects are discussed. All the results are included. It is concluded that the proposed technique leads to a simple modular control circuit, wider range of operating currents, and increased system stability.

Flexible dv/dt and di/dt control method for insulated gate power switches

Active gate control techniques are introduced in this paper for flexibly and independently controlling the dv/dt and di/dt of insulated gate power devices during hard-switching events. In the case of dv/dt control, the output voltage dv/dt can be controlled over a wide range by electronically adjusting the effective gate-to-drain (-collector) capacitance (i.e., Miller capacitance). For di/dt control, similar techniques are applied for electronically adjusting the output current di/dt over a wide range using voltage feedback from a small inductor connected in series with the switch's source (emitter) terminal. Both techniques are designed to maximize their compatibility with power module implementations that combine the power switch and its gate drive, including integrated circuit gate drives. Simulation and experimental results are included to verify the desirable performance characteristics of the presented dv/dt and di/dt control techniques.