A. Galluzzo

A new driving circuit for IGBT devices

IGBT devices are increasingly used in power electronic equipment due to their high power handling capability. This paper deals with the problems that concern the turn-on, turn-off, and short-circuit of these devices. An optimal new driving circuit is proposed which gives excellent device output performances. Experimental oscillogram traces of transient condition tests are given, which demonstrate the advantages of using the new driving circuit. The suitability of the driving circuit for integration is analyzed. >

Control of the switching transients of IGBT series strings by high-performance drive units

In the field of power electronics, the use of series-connected insulated gate devices, such as insulated gate bipolar transistors or power MOSFETs, is interesting in order to obtain fast and efficient power switches in medium-range power converters. In this kind of application, the control of the voltage sharing across the series strings of devices is an important aspect to be considered. The proposed technique allows obtaining safe commutations of the switches by simple and effective control circuits acting on the gate side of the power devices. In particular, the gate drive units are arranged in order to ensure good performance during the switching transients, while preventing overvoltage peaks on the devices. Both the design criteria and analysis of the control circuit are developed. Several experimental tests are reported in order to demonstrate the validity and correctness of the proposed approach.

Snubberless voltage sharing of series-connected insulated-gate devices by a novel gate control strategy

Insulated gate devices, such as metal oxide semiconductor field effect transistors (MOSFETs) or insulated gate bipolar transistors (IGBTs), are increasingly used in high-voltage power converters where a request for fast power switches is growing. Series connection of devices is a viable approach to manage voltages higher than the blocking voltage of the single device. The main problem in such an application is to guarantee the voltage balance across the devices both in steady-state and during switching transients. In this paper, a novel approach is presented, which is used to equalize the voltage sharing during the switching transients. The main advantages of the proposed method consist in avoiding the traditional use of the snubber capacitors, in the output power side, and in working on the gate side. The application of the proposed gate drive technique is firstly discussed and compared with different solutions, hence, validated by experimental tests applied to the control of series connected devices. Finally, a comparison is performed between the transient behaviors of two different configurations: a single switch with high-voltage blocking capability, and in alternative a series of two devices which together ensure the voltage blocking capability of the single switch. The better performances of the latter configuration, working with the proposed control circuit, over the former have been experimentally demonstrated.

A new adaptive driving technique for high current gate controlled devices

MOSFETs and IGBTs devices are increasingly used in electronic circuits due to both the easy driving and the capability to handle high currents and voltages at high switching frequencies. This paper deals with a new driver circuit that allows optimisation of the switching speed, reduction of the energy losses during the switching time, and limiting of the electromagnetic interference (EMI). Firstly an analysis of voltage and current switching waveforms of gate insulated devices is performed. Hence, it is shown how to control voltage and current slopes independently by using a suitable adaptive driving technique based on a PLL approach. Such a technique has been adapted in order to correctly generate the gate signals regardless of the operating conditions. Finally, practical tests of the proposed driving circuit obtained using a single switch converter and IGBT devices are reported.<<ETX>>

Snubberless balancement of series connected insulated gate devices by a novel gate control strategy

The series connection of insulated gate devices, such as MOSFETs or IGBTs, is increasingly used in high-voltage power converters where the demand for fast power switches is growing. The main problem in such an application is to guarantee the voltage balance across the devices both at steady-state and during switching transients, in order to avoid damaging overvoltages. In this paper, a novel approach is used to balance the voltage during switching transients by controlling the charge profile of the input gate capacitance. The main advantages of the proposed method consist in avoiding the common use of balancing capacitors in the output power side, and in working on the gate drive signals only. The application of the proposed gate drive technique is discussed first and then validated by experimental tests applied to the control of two series connected devices (MOSFETs or IGBTs). The proposed approach is also applicable for more than two devices. In particular, the validity has been proven by computer simulations for three components. Finally, a comparison is performed between the switching behaviors of two different configurations: a high-voltage application having for a high-voltage single switch device; or a series of two lower voltage rated devices. The advantage of the latter configuration, having the proposed active voltage balancing, over the former has been experimentally demonstrated with regard to the turn-off power losses.

A new high voltage power MOSFET for power conversion applications

The aim of this paper is to explore the switching capability of a new kind of high-voltage power MOSFET device called multiple drain mesh (MDmesh). This new power MOSFET shows very interesting characteristics in terms of both die size reduction and switching performances. By the used technological process a considerable reduction in silicon conduction losses per area unit has been observed, thus allowing a noticeable resizing of the devices and the use of smaller packages. Moreover, a strong reduction in the parasitic capacitance (i.e. gate charge) with an improved switching behavior has been observed. The power MOSFET that we are now introducing can replace standard power MOSFET devices in switch mode power supply (SMPS) or power factor correction (PFC) applications, thus allowing a valuable reduction of the power losses to be obtained and an increase in the converter efficiency, whereas the switching frequency is unchanged. This paper starts by describing the main technological issues of the new device, which is compared to more standard devices. The switching transients have been carried out looking for actual applications, and the advantages of the new device are discussed in terms of energy saving and performance improvement. Finally, a comparison with a standard device with the same voltage and current ratings is made and discussed, showing the improved performances of the new device.

Smart power devices in soft switching applications

A smart power device, having a monolithic cascode structure with a high-voltage bipolar junction transistor and a low voltage power MOSFET, is presented and investigated in soft switching applications. The basic characteristics of this device are described both in terms of its structure and electrical performances. In particular, the device behavior is investigated in a zero-voltage quasi-resonant boost converter switching at a frequency of 100 kHz in order to show the high performances of this switch in the field of high voltage, and high-frequency applications. The experimental tests are carried out in several working conditions, and emphasis is given to a comparison with alternative switches as power MOSFETs, and IGBTs in order to understand better the main advantages and drawbacks of this switch. Finally, some figures relative to the power losses versus the switching frequency and the limit on the working frequency of the devices are given with reference to the actual converter used as a benchmark. The experimental results show the superiority of the cascode in the field of the considered switching frequency.

Bipolar-MOS monolithic cascode switch in VIPower technology

In this paper a bipolar-power MOSFET cascode monolithic device, realized in ST-SGS Thomson VIPower (Vertical Intelligent Power) Technology called M3, is presented. The basic device features a three-stage deep-base NPN BJT and a vertical power MOSFET, realized inside the emitter of the trilinton output stage itself for emitter switching. The paper starts with a survey of the main characteristics of the SGS-Thomson Vertical Intelligent Power technology. Then the switching performances of the device are compared to power MOSFET and fast-switching IGBTs in terms of their forward conduction current density turn-off times and breakdown voltages.<<ETX>>

Cascode monolithic switches in resonant circuit applications

Applications of new high-voltage bipolar-power MOSFET cascode monolithic devices are developed. The device features of this smart-power emitter-switching component are described both in terms of physical structure and electrical performance. Firstly, the device is characterized in a soft-switching zero-voltage (ZV) test circuit. Experimental tests are carried out under several working conditions in order to understand the main advantages and drawbacks of the switch. Finally, actual ZV applications, such as a step-down ZV quasi-resonant converter (QRC) and a TV deflection circuit, are presented and discussed.