A modern low loss, high turn-off capability GCT gate drive concept

Abstract

AcknowledgementsAlthough based on new ideas to a great extend, the request, discussions and support from the works is absolutely necessary to make the development of a new gate driver a success. The authors therefore cordially thank all the members involved in the project activities for their continued support with a particular deep thank to Mr. Shimomura, Mr. Takao and Mr. Mizohata for their contributions to the 6inch OCT gate driver and to Mr. Yoneda, Mr. Tokunoh and Mr. Itoh for their contributions to the gate driver for SGCTs. AbstractIn GCT technology the gate drive has become a key component to widely deternine the mech-anical and electrical characteristics of the total power device. Based on recent improvements in switch-mode power supply technology, new circuit topology and mnechanical design of GCT gate drivers has been developed to enhance OCT turn-off capability, reduce gate drive power dissipation and shrink the dimensions and the weight of the gate drivers. In order to enhance service life, by mneans of the new topology gate driver for OCT are realized without firmly attached electrolytic capacitors for the first time. * In contrast to many othcr clcctronic compononts, cloctrolytic capacitors show tompcraturo dependent degradation over time (aging), which may result in a significant loss of capacitance. As hOE 2005 -I2'rc.Jcn 90-75815-08-5 P.1 A iiiodc,-ra low loss.. hig.i tLira-c-ff eapabihW GCT-gate.-d rivc: coaccp. GRUENING Hco1t DEl 2005 -L)i--;c11i ISBN :90-75815-08-5 1>q1 A 1w so,, higdlh tbCT GCr-gtdt,op GRIJNNG Hmot 12K 2005 -I2'rc.xkn PH A iiiodc,-ra low loss.. hig.i tLira-c-ff eapabihW GCT-gate.-d rivc: coaccp. GRUENING Hco1t DEl 2005 -L)i--;c11i ISBN:90-7581508-5 P.7X

Recent developments in IGCT gate units

“…2 shows ESR as a function of temperature for two types of electrolytic capacitor where "Type A" is the electrolytic capacitor currently used in the present IGCT-generation of gate units and "Type B" is a new type used in the newly developed generation called HPT-IGCT (High Performance Technology) and can be seen to have less losses at high ambient temperature. Despite the marked reduction of ESR of Type B, below -30°C the obverse is true and thus for low temperature applications such as Traction track-side choppers, the limitations of electrolytic capacitors can be avoided by the use of ceramic capacitors [5]. However, using ceramic capacitors exclusively, makes it more difficult to obtain the requisite capacitance in a given volume.…”

IGCT Gate Unit for Zero-Voltage-Switching Resonant DC Transformer Applications

“…This effect has been considered and studied in e.g. [12], [13], [17]. In gate units, this occurrence is usually coped with by adding an additional stage that reduces the gate current by dissipating the energy in the gate unit [12], [17].…”

“…To ensure that the GCT is homogeneously ready to take over the current again a so-called retrigger pulse, similar to the turn-on pulse, is applied to the gate. Reference [13] proposes a different approach to cope with negative gate voltage without the necessity to dissipate the energy on the PCB. However, the ON channel is supplied by a dedicated floating power supply, which increases the complexity.…”

“…In the literature, the capacitor C off is typically implemented using electrolyte aluminum capacitors [14], [17], [19] or the ceramic chip capacitors [13], [16], [19]. While the electrolyte aluminum capacitors have clear cost advantages, they are rather bulky, have high stray inductance, and allow for only low rms currents, which leads to typical high number of parallel-connected capacitors that populate large area of the gate unit.…”

“…In contrast, the ceramic capacitors allow for very high rms currents but have typically lower values of capacitance that further decreases with applied direct voltage. As a consequence, the solutions based on this technology are often costly and target minimum possible capacitance [13], which might impact the turn-OFF capability of the gate unit. In this paper, the polymer tantalum capacitors are selected as the technology, since these pose a trade-off between the two aforementioned technologies, allowing for higher capacitances while remaining small in size.…”