功率器件发展及新型可关断晶闸管

本文介绍了功率器件的发展过程，重点阐述了近年来出现的可关断晶闸管的结构，工作机理，及它们各自的特点。     

Floating base thyristor

The floating base thyristor (FBT) is a new thyristor structure in which its p-base region, containing a p⁺ region is not shorted to the n⁺ emitter. Using the DMOS process, an n-channel and a p-channel MOSFET are integrated with the thyristor structure. The device operates in the thyristor mode with a low ON-state voltage drop at even high current densities when a positive bias is applied to, both gates. When a negative bias is applied to the OFF gate, the device operates in the IGBT mode with the saturated current controlled by the positive bias applied to the ON gate     

The MOS-controlled MCG-GTO thyristor

In the new MOS-controlled turn-off thyristor described, the recombination of holes in the n base by the shunt of the floating p-n junction in the n base occurs simultaneously with the recombination of holes in the p base due to the cathode emitter shunt using the two MOS gates. This turn-off operation offers two important improvements over the normal MOS-controlled thyristor by virtue of the recombination of holes in the n base during the turn-off process. These improvements are high-speed turn-off and high maximum controllable current. Experimental verification of the device's operation is achieved using a lateral minority-carrier control (MCC) GTO thyristor having two n-channel MOSFETs. In this device, the turn-off operation is achieved by the simultaneous recombination of holes in both the n and p bases due to the equivalence of one-gate driving accomplished by the connection of the two MOS gates     

A double-gate-type static-induction thyristor

A double-gate-type static-induction thyristor (DG-SIThy) with a high blocking voltage and a high current rating has been fabricated. In this paper, a basic operational mechanism, a fabrication procedure, and the electrical characteristics of the DG-SIThy are described. In the DG-SIThy, both electron injection and hole injection are controlled by signals applied to two gale regions so that the DG-SIThy is capable of higher frequency operations than a single-gate SIThy. In the DG-SIThy, described here, both a cathode and a gate (first gate) regions have been fabricated on one side of a semiconductor wafer and both an anode and gate.(second gate) regions on another side. For realizing the DG-SIThy with a high blocking voltage and a high current rating, we have tried attentively to form a p-n junction on one side of the wafer without influencing the p-n junction on the other side, and have developed a new counter-doping technique for epitaxial growth and an improved package structure for a compression-mounted device. The DG-SIThy fabricated with these techniques has shown a for-Ward blocking voltage of 1000 V, an average current rating of 100 A, and a forward voltage drop of 1.44 V at the rated anode current. A turn-on time of 0.95 its and a turn-off time of 0.48 µs have been observed at the rated anode current and at anode voltages of 650 and 550 V, respectively. As already speculated, the DG-SIThy shows a higher switching speed and a lower forward drop than the single-gate SIThy.     

The asymmetrical field-controlled thyristor

A new device structure has been developed for field-controlled thyristors. In this structure, the uniformly doped n base of the conventional device has been replaced with a very lightly doped region near the gate and a more heavily doped region at the anode. This change in the base doping profile results in a significant improvement in the tradeoff between the forward-blocking voltage capability and the on-state forward-voltage drop. In addition, the high-resistivity region around the gate area allows the device to pinch off anode current flow at zero gate bias due to the built-in potential of the gate junction. The devices can, however, be triggered to the on-state by applying a small forward gate voltage and exhibit a forward voltage drop in the on-state which is much lower than that of conventional devices. The high resistivity of the channel area between gates also results in these devices having dc blocking gains in excess of 60, which is the highest value achieved in devices of this type. Further, because these devices have been fabricated using conventional planar processing techniques, this structure is suitable for high-volume production with high processing yields.     

集成门极换流晶闸管IGCT

介绍了一种新型电力半导体器件——集成门极换流晶闸管 (IGCT)的特性、工作原理、关键技术及其应用情况 ,并指出它必将成为大功率应用中的首选电力半导体器件。     

The MOS-gated emitter switched thyristor

A monolithic device structure for obtaining MOS-gate-controlled turn-off of a thyristor is described. The device, called the emitter switched thyristor (EST), is designed so that the thyristor current flows through an enhancement-mode MOSFET, integrated into the base region of the thyristor, during the on state. Although this results in a small (0.25 V) increase in the forward voltage drop, it is demonstrated that excellent turn-off characteristics can be obtained, with typical turn-off of less than 1 μs     

Characteristics of the emitter-switched thyristor

The first experimental demonstration of 600-V emitter-switched thyristors fabricated using an IGBT (insulated-gate bipolar transistor) process sequence is reported. The forward drop is less than that for the IGBT, but larger than that for a thyristor by about 0.5 V due to the thyristor current flowing via the MOSFET channel. A unique characteristic observed for these devices, not exhibited by any previous MOS-gated thyristor structures, is gate-controlled current saturation even after thyristor latch-up. Switching tests were performed up to a current density of 1000 A/cm² on single-unit cells and the measured turn-off times were about 7 μs     

Current-zero detection in thyristor convertors

A method of detecting current zeros in thyristor convertors is described. The method utilises an optically coupled isolator to sense the voltage across each of the thyristors in the convertor, thereby detecting the conduction state of each device. This information is then processed by simple logic to detect current zeros from the convertor.     

Lateral junction-isolated emitter switched thyristor

The operation of a 600-V junction-isolated lateral emitter switched thyristor (JI-LEST) is demonstrated. These devices exhibit an on-state voltage drop of 2.6 V at a current density of 100 A/cm² , a turn-off time of 20 μs, and a maximum controllable current density of about 200 A/cm²     

A new lateral MOS-controlled thyristor

A lateral MOS-controlled thyristor (LMCT) structure that uses an MOS gate to turn it both on and off is presented. The device structure offers improved maximum turn-off current capability and forward voltage drop. The former is achieved by using a DMOS transistor and a parasitic vertical p-n-p transistor, while the latter is achieved by eliminating a parasitic lateral p-n-p transistor in the conventional structure. The device utilizes the resurf technique to achieve high area efficiency, breakdown voltage, and reliability. Devices that have more than 250-V forward blocking capability were fabricated in dielectrically isolated silicon tubs using the standard bipolar-CMOS-DMOS process     

Geometry of thyristor cathode shunts

In the all-diffused thyristor, the shunt pattern can easily be introduced by photo masking or silk screen techniques. It is known that the emitter shunts of various designs affected the rate of rise of forward blocking voltage, the forward I-V characteristics, the loop effect, the turn-on time, the dynamic forward voltage drop, and the reverse recovery time. This paper will show their relations to several shunt patterns based on experimental results.     

A ROM-controlled thyristor trigger circuit

A circuit for application in microprocessor-based thyristorpower control is proposed. We specify the READ-ONLY memory (ROM) for linear average output voltage control design and for linear average output power control design.     

Oscillator-circuit thyristor converters for induction heating

For the induction heating of metals it is advisable in many cases to use higher frequencies. So far, the input required has been supplied by rotary converters or high-vacuum tubes. Recently, static converters with thyristors have also been employed. Equipment already installed is described, and details are given on the considerations leading to the solution adopted.     

Temperature dependence of field-controlled thyristor characteristics

The dependence of the characteristics of field-controlled thyristors upon the ambient temperature has been examined in the range of -30 to 200°C. Unlike conventional thyristors, these devices have been found to continue to exhibit forward blocking capability up to the highest measurement temperature (200°C). In fact, it is shown here that the forward blocking capability as well as the blocking gain improve with increasing temperature with the usual scaling of the leakage current for power devices. The reverse blocking capability is also retained. The forward voltage drop of the device in the conducting state decreases with increasing temperature. This behavior is shown to be similar to that of conventional rectifiers and thyristors operated at high injection levels. Further, the force gate turn-off time of the devices has been found to increase with increasing temperature. This has been correlated with a measured increase in the minority-carrier lifetime. The results of this study demonstrate that field-controlled thyristors are capable of being operated at higher temperatures than conventional thyristors.     

Dielectrically isolated lateral emitter switched thyristor

The operation of a 500 V dielectrically isolated lateral emitter switched thyristor (DI-LEST) is described for the first time. Experimental devices exhibit an on-state voltage drop of 2.35 V at a current density of 100 A/cm/sup 2/, and a maximum controllable current density of about 200 A/cm/sup 2/. The on-state voltage drop decreases with increasing drift layer thickness consistent with the uniform lateral current flow observed in two-dimensional numerical simulations.<>     

Adaptive thyristor power, control circuits

A solid-state circuit is described that provides electronically settable memory control (adaptive control) of thyristor power regulating devices. Electrical power delivered to ac loads, such as lighting, heating, or motors, can be smoothly varied or set to any value from zero to essentially full power by a manual, computer, or remote-controlled application of a voltage pulse to a circuit adapt terminal. Power settings of the circuit can be maintained indefinitely with or without applied power, yet they can be changed quickly (milliseconds) or slowly (dekaseconds) by the application of an appropriate adapt pulse. An adaptive ferroelectric transformer provides the analogue memory capabilities of the control circuit.     

A two-stage DC thyristor circuit breaker

High-current DC thyristor circuit breaker (TCB) devices, based on the parallel capacitor-current commutation-forced turn-off principle, require very large capacitors to effect correct operation as fault-current interrupters in electrical circuits. The commutation capacitors of TCB devices that interrupt current in a single switching operation absorb virtually all the electromagnetic energy stored in circuits, where they operate during the single switching process. These device types interrupt current extremely fast, but because of the scale of the energy transfer to the commutation capacitor, they are especially prone to producing short-duration switching overvoltages of excessive magnitude. A novel TCB device involving two switching operations or stages is presented and analyzed. With this device type, the circuit-stored energy is transferred to the commutation capacitor in two stages, which, in so doing, produces significantly lower switching overvoltages than the conventional “single-stage” TCB device. Results of a range of tests on a low-voltage two-stage TCB device and a high-power-prototype version are given together with the basis for determining their optimum design criteria. Comparative simulation studies are also provided. Finally, the limitations of TCB devices are examined and discussed in conjunction with cost comparisons and their merits and limitations for typical applications     

Design considerations for p-i-n thyristor structures

An analysis of a high-voltage gate turn-off (GTO) thyristor structure with a double-layered n base (p-i-n structure) is presented. From integration of Poisson's equation, an expression for the forward-blocking voltage at the onset of avalanche breakdown is obtained. Simple design criteria are developed to calculate the optimal thickness and doping density of the n base of a conventional pnpn structure designed for a specific voltage-blocking capability. The same principle is applied to design for the doping densities and thicknesses of the high-resistivity region and the buffer layer of the p-i-n GTO structure. The forward-blocking voltage, as well as the on-state voltage (at a current density of 300 A cm^-2) is predicted for a wide range of base layer thicknesses and doping densities to illustrate the available tradeoff options. Lowest on-state power dissipation for high blocking voltages (>6000 V) is predicted for a doping level of 5×10¹² cm^-3 in the high-resistivity layer