High Voltage Current Saturation Research Articles

A New Protective Circuit to Improve Short-Circuit Withstanding Capability of a Lateral Emitter Switched Thyristor

A new circuit to protect lateral emitter switched thyristors (LESTs) for high voltage current saturation is proposed. We fabricated this circuit by employing a widely used process compatible with insulated gate bipolar transistors (IGBTs). When the floating n+ voltage is larger than the threshold voltage of protecting metal oxide semiconductor field effect transistor (MOSFET), the protective circuit alters the operation of the LEST from regenerative mode to non-regenerative mode. Experimental results showed that a high voltage current saturation exceeding 200 V was measured in the LEST with the proposed protective circuit, while the current saturation of the conventional LEST was limited to 17 V. This allowed the LEST to withstand the hard switching fault (HSF) condition over 10 µs during the hard switching fault (HSF) condition.

A new protection circuit for high-voltage current saturation of LEST

A new protection circuit for high-voltage current saturation of a lateral emitter switched thyristor (LEST) is proposed. We fabricated this circuit by employing a widely used insulated gate bipolar transistor compatible process. A high-voltage current saturation exceeding 200 V was measured in the EST with the proposed protection circuit, while the current saturation of the conventional LEST is limited to 17 V by the breakdown of the lateral MOSFET.

A New Protection Circuit of Emitter Switched Thyristor (EST) for Short-Circuit Withstanding Capability

A new protection circuit of Emitter Switched Thyristor (EST), which improves the short circuit withstanding capability is proposed and verified by 2-D simulation. The proposed EST with the new protection circuit can successfully achieve a highvoltage current saturation which can secure the shortcircuit withstanding capability because the protection circuit detects the potential of the floating n+ and decreases the gate voltage of EST while the conventional EST cannot exhibit a highvoltage current saturation. Simulation results show that a highvoltage current saturation over 600V and 10µs of short-circuit withstanding time can be successfully achieved employing a new protection circuit without increasing of the forward voltage drop.

A new MOS gate thyristor—The single-gate emitter controlled thyristor (SECT)

This article presents a new MOS gate controlled thyristor—single-gate emitter controlled thyristor (SECT). Its operation is verified by two-dimensional numerical simulations and the operation mechanisms are analyzed. Simulation results obtained on a 2500 V SECT show that the SECT has an excellent high voltage current saturation capability and much wider FBSOA and RBSOA than those of the IGBT and the DC-EST, while at the same time offering lower conduction and switching losses than those of the IGBT.

A new three-terminal thyristor-based high-power switching configuration with high-voltage current saturation

A new high-voltage power switch configuration having thyristor based on-state current conduction together with high-voltage current saturation characteristics is described. Current saturation is obtained in the new thyristor structure by diverting part of the base current at a predesigned current level to bring the NPN and PNP transistors comprising the thyristor out of their regeneratively-coupled conduction mode. The concept has been experimentally verified by fabricating 1200 V, 175 A devices.

The accumulation channel driven bipolar transistor (ACBT)

A new three-terminal power switch called the Accumulation Channel driven Bipolar Transistor (ACBT) is proposed and experimentally demonstrated. In the on-state, the characteristics of the ACBT have been found to approach those of a P-I-N rectifier with a MOSFET in series for regulating its current, an equivalent circuit considered to be an ideal for MOS/Bipolar power devices. Unlike previous devices, the high off-state voltage is supported by the formation of a potential barrier to the flow of electrons from the N/sup +/ emitter into the N-drift region within a depletion region. The absence of the P-base region within the ACBT cells eliminates the parasitic four layer PNPN thyristor which had limited the performance of previous MOS/Bipolar transistor structures. Consequently, the ACBT structure has large maximum controllable and surge current densities in addition to low on-state voltage drop and high-voltage current saturation capability.

SIMFCT: a MOS-gated FCT with high voltage-current saturation

This paper describes the SIMFCT: a new MOS-gated power device in which SIMOX technology is used to integrate a series MOSFET with a vertical FCT structure. The SIMFCT, exhibits high voltage-current saturation beyond the breakdown voltage of the lateral series MOSFET, and since it does not have a parasitic thyristor, it possesses a superior FBSOA when compared to the IGBT. The physics of device operation, results of two-dimensional numerical simulations and experimentally measured characteristics on SIMFCT structures fabricated using a nine mask SIMOX Smart Power process are presented.

The dual gate emitter switched thyristor (DG-EST)

A new device structure, called the dual gate emitter switched thyristor (DG-EST), is introduced for simultaneously obtaining on-state voltage drops lower than that of the conventional emitter switched thyristor (C-EST) and the high-voltage current saturation features of the Dual Channel EST (DC-EST). The DG-EST contains a DC-EST section and a C-EST section with a common thyristor section that can be controlled using two independent gate electrodes. When a positive bias is applied to both the gates, the device operates in a thyristor mode with the thyristor current constrained to flow through two lateral MOSFETs which minimizes the on-state voltage drop. When a "zero" bias is applied to the gate of the conventional EST, the device exhibits high-voltage current saturation, with the bias on the gate of the DC-EST controlling the saturated current. In this paper, the results of measurements performed on devices fabricated with a six-mask IGBT-like process are reported.

CRMGT: a MOS-gated power switch

A new MOS-gated thyristor structure with low on-state voltage drop, known as a channel regulated MOS-gated thyristor (CRMGT) is reported for the first time. The CRMGT uses a thin silicon layer, formed above a buried oxide layer, to control current flow through a four layer thyristor structure. It is demonstrated via simulations that the CRMGT has excellent high voltage current saturation with an FBSOA superior to that of the IGBT.

The SIMEST: an EST structure without parasitic thyristor achieved using SIMOX technology

A new emitter switched thyristor (EST) structure, in which the lateral N-channel MOSFET is isolated from the thyristor by using SIMOX technology to eliminate the parasitic thyristor, is presented. This structure is experimentally demonstrated to exhibit high voltage current saturation at large gate biases beyond the breakdown voltage of the lateral N-channel MOSFET and a lower on-state voltage drop than the dual channel EST.

High-voltage current saturation in emitter switched thyristors

Current saturation at high voltages in MOS-gated emitter switched thyristors (ESTs) is demonstrated. It is shown that by using an improved EST structure containing a dual-channel lateral MOSFET, the thyristor current can be saturated to high voltages through MOS gate control. In experimental devices with 600-V forward blocking capability, it is observed that current densities of 110 A/cm/sup 2/ could be saturated up to 450 V with a gate bias of 3.5 V. Experimental measurements and numerical simulations indicate that, during current saturation, the voltage appears across the junction between the P-base region and the N/sup -/ drift region and not across the lateral MOSFET. >

Report on the Work on Discrete Devices: High Voltage Transistors and Varactor Diodes

The important electrical parameters (such as breakdown voltage, current gain and rating, power dissipation, switching times, saturation voltage etc.) of the high-voltage power transistor are achieved by controlling the physical parameters of the device such as base and collector resistivities, widths and emitter geometry. There are several tradeoffs necessary, such as between high voltage rating and current gain or saturation voltage.Triple-diffusion technology has been chosen for the voltage ratings above 1000 V in comparison with other technologies. Methods of passivation such as surface contouring, surface coatings are chosen from considerations of ease of operation, yield and cost considerations so as to give low leakage with the high voltage requirement. For attaining the current rating, the choice of metallization is important. Some of the results obtained are: BVCEO(1A)=1000 V, BVCBO= 1500 V, hFE=2 to 5.The electrical parameters of tuning varactor (for the VHF and UHF bands) are the capacitance ratio at the working voltage range, the quality factor at the frequencies of operation and variation of tuning with voltage.The retrograde impurity profile is achieved by precise control of diffusion of impurities; C(3)/C(25) of 4 to 6 has been achieved. High Q is achieved by low series resistance and low leakage current.