EPE Association: 06 - Madep - M1.2 - MEDIUM POWER DEVICES 01

06 - Madep - M1.2 - MEDIUM POWER DEVICES 01
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1991 - EPE-MADEP Joint Sessions > 06 - Madep - M1.2 - MEDIUM POWER DEVICES 01

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   A NEW SPECIFYING METHOD FOR POWER DIODES
By H. Gebhardt; K. Heumann [View]
[Download]

Abstract: The application of fast recovery diodes with high voltage blocking capabilities is increasing rapidly, thinking of the availability of turn-off devices in higher power ranges. Both devices find their use in nearly every modern power electronic switching design. Hereby, the features of the switches have been improved and for quite some time diodes have been neglected. Now new power diodes are available and data sheets promise superb freewheeling operation. But presumptions once made for small signal devices don't correspond to the true behaviour in power electronics of today. Especially turn-off characteristics are important, but with common data sheets it is unpredictable how the used diode will work in the chosen circuit. Many parameters are to be taken into account, and a special look has to be taken at probable voltage overshoots and stray inductances. The often given value of the soft factor S can only describe a narrow range of operational behaviour, if ever. A new specifying method reduces data to be given and makes it easier to choose the best diode possible in advance.

   INVESTIGATIONS ON THE TURN-ON PROCESS IN FAST RECOVERY POWER DIODES
By S. Winternheimer [View]
[Download]

Abstract: A model describing the transient turn-on behaviour of a fast recovery power diode is derived and implemented into a simulation program for analysis of electrical networks. The model is based on the physical processes in a p+nn+-doped diode. The time- and geometric-dependent carrier concentration in the low doped middle region which has the main influence on the turn-on process is investigated. The behaviour of this concentration is approximated by a time-dependend resistance in the middle region which causes mainly the voltage spike during the turn-on process. The model is compared to experimental measurements in a chopper circuit with a MOSFET as switching element.

   ON THE OPTIMUM SWITCHING OPERATION OF POWER MOSFETs
By M. I. Castro Simas; A. Ferreira; J. Costa Freire [View]
[Download]

Abstract: This paper discusses the optimized switching behaviour of Power MOS transistors using reverse conduction through the channel, which disables body diode conduction. This procedure is aimed at high frequency applications which require bidirectional current paths. An insight into MOSFET reverse conduction modelling is presented in order to achieve an accurate tool for computer aided design or topologies using MOSFETs bidirectional current paths. Simulation results are shown in a most demanding topology, a series resonant converter, to evaluate the accuracy of the model.

   MOSFET OPERATING UNDER HARD SWITCHING MODE: VOLTAGE AND CURRENT GRADIENTS CONTROL
By J. P. Berry [View]
[Download]

Abstract: Classically, the operating safety of MOSFET in hard switching mode and the limitation in electromagnetic radiations require an open loop acting on the gate load rate. Another disturbing rate consists of a dampened sine transient response mode corresponding to a transfer function of order 2 which can be obtained by computation using AC low signal model. The control of current and voltage gradients is proposed via a closed loop (correctors connected in parallel on MOSFET). Current sense can be implemented by shunt but, better, direct current gradient measurement can be done by a very little inductor of some nanohenries. Such driving circuits providing transient stability, current and voltage gradient control, peak current limitation as well as efficient short-circuit protection were breadboarded. Electrical measurements in good agreement with simulation results are presented. So circuit simulation tools are validated and the advantage of investigating a specific integrated intelligent driving circuit is shown .

   CONTACT ETCHING TO INCREASE BREAKDOWN VOLTAGE OF GRADED NMOSTs
By Nebojsa D. Jankovic [View]
[Download]

Abstract: The influence of silicon contacts etch in freon plasma on short channel breakdown characteristics of Fully Graded (FG) NMOSTs has been examined. An experimental FG NMOSTs, featuring Leff=3.7μm, 8Vds=46V and BVsus=35V, has been fabricated and subjected to contacts etch process . It appears that carefully optimized plasma etching of source-drain contacts can completely eliminates bipolar-like breakdown sustaining voltage (BVsus) without affecting other FG NMOST's electrical parameters.

   THE DV/DT CAPABILITY OF POWER MOSFETS AND MERGED BIPOLAR-MOS DEVICES
By Edmond Cretu; Andrei Silard; Mirom Duta; Daniel Poenar [View]
[Download]

Abstract: A thorough theoretical investigation of dV/dt-induced effects in power MOSFET's and merged bipolar-MOS devices is performed in this work. Analytical expressions enabling the estimation of dV/dt-capability as a function of devices structures and gate circuitry have been obtained. The criteria which tilt the dV/dt-triggering of MOSFETs, IGTs and MCTs toward either MOS-type or bipolar-type turn-on have been established. It was shown that the actual limitation in dV/dt-capability of power MOSFETs and IGTs is due primarily to faulty MOS-type turn-on, while in MCTs the dV/dt-capability is limited by bipolar-type turn-on. The predictive relationship developed in this work projects dV/dt-capabilities close to those recorded in experimental devices.

06 - Madep - M1.2 - MEDIUM POWER DEVICES 01
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 1991 - EPE-MADEP Joint Sessions > 06 - Madep - M1.2 - MEDIUM POWER DEVICES 01
	[return to parent folder]

	A NEW SPECIFYING METHOD FOR POWER DIODES By H. Gebhardt; K. Heumann	[View] [Download]
Abstract: The application of fast recovery diodes with high voltage blocking capabilities is increasing rapidly, thinking of the availability of turn-off devices in higher power ranges. Both devices find their use in nearly every modern power electronic switching design. Hereby, the features of the switches have been improved and for quite some time diodes have been neglected. Now new power diodes are available and data sheets promise superb freewheeling operation. But presumptions once made for small signal devices don't correspond to the true behaviour in power electronics of today. Especially turn-off characteristics are important, but with common data sheets it is unpredictable how the used diode will work in the chosen circuit. Many parameters are to be taken into account, and a special look has to be taken at probable voltage overshoots and stray inductances. The often given value of the soft factor S can only describe a narrow range of operational behaviour, if ever. A new specifying method reduces data to be given and makes it easier to choose the best diode possible in advance.

	INVESTIGATIONS ON THE TURN-ON PROCESS IN FAST RECOVERY POWER DIODES By S. Winternheimer	[View] [Download]
Abstract: A model describing the transient turn-on behaviour of a fast recovery power diode is derived and implemented into a simulation program for analysis of electrical networks. The model is based on the physical processes in a p+nn+-doped diode. The time- and geometric-dependent carrier concentration in the low doped middle region which has the main influence on the turn-on process is investigated. The behaviour of this concentration is approximated by a time-dependend resistance in the middle region which causes mainly the voltage spike during the turn-on process. The model is compared to experimental measurements in a chopper circuit with a MOSFET as switching element.

	ON THE OPTIMUM SWITCHING OPERATION OF POWER MOSFETs By M. I. Castro Simas; A. Ferreira; J. Costa Freire	[View] [Download]
Abstract: This paper discusses the optimized switching behaviour of Power MOS transistors using reverse conduction through the channel, which disables body diode conduction. This procedure is aimed at high frequency applications which require bidirectional current paths. An insight into MOSFET reverse conduction modelling is presented in order to achieve an accurate tool for computer aided design or topologies using MOSFETs bidirectional current paths. Simulation results are shown in a most demanding topology, a series resonant converter, to evaluate the accuracy of the model.

	MOSFET OPERATING UNDER HARD SWITCHING MODE: VOLTAGE AND CURRENT GRADIENTS CONTROL By J. P. Berry	[View] [Download]
Abstract: Classically, the operating safety of MOSFET in hard switching mode and the limitation in electromagnetic radiations require an open loop acting on the gate load rate. Another disturbing rate consists of a dampened sine transient response mode corresponding to a transfer function of order 2 which can be obtained by computation using AC low signal model. The control of current and voltage gradients is proposed via a closed loop (correctors connected in parallel on MOSFET). Current sense can be implemented by shunt but, better, direct current gradient measurement can be done by a very little inductor of some nanohenries. Such driving circuits providing transient stability, current and voltage gradient control, peak current limitation as well as efficient short-circuit protection were breadboarded. Electrical measurements in good agreement with simulation results are presented. So circuit simulation tools are validated and the advantage of investigating a specific integrated intelligent driving circuit is shown .

	CONTACT ETCHING TO INCREASE BREAKDOWN VOLTAGE OF GRADED NMOSTs By Nebojsa D. Jankovic	[View] [Download]
Abstract: The influence of silicon contacts etch in freon plasma on short channel breakdown characteristics of Fully Graded (FG) NMOSTs has been examined. An experimental FG NMOSTs, featuring Leff=3.7μm, 8Vds=46V and BVsus=35V, has been fabricated and subjected to contacts etch process . It appears that carefully optimized plasma etching of source-drain contacts can completely eliminates bipolar-like breakdown sustaining voltage (BVsus) without affecting other FG NMOST's electrical parameters.

	THE DV/DT CAPABILITY OF POWER MOSFETS AND MERGED BIPOLAR-MOS DEVICES By Edmond Cretu; Andrei Silard; Mirom Duta; Daniel Poenar	[View] [Download]
Abstract: A thorough theoretical investigation of dV/dt-induced effects in power MOSFET's and merged bipolar-MOS devices is performed in this work. Analytical expressions enabling the estimation of dV/dt-capability as a function of devices structures and gate circuitry have been obtained. The criteria which tilt the dV/dt-triggering of MOSFETs, IGTs and MCTs toward either MOS-type or bipolar-type turn-on have been established. It was shown that the actual limitation in dV/dt-capability of power MOSFETs and IGTs is due primarily to faulty MOS-type turn-on, while in MCTs the dV/dt-capability is limited by bipolar-type turn-on. The predictive relationship developed in this work projects dV/dt-capabilities close to those recorded in experimental devices.