Biswarup Basak

Gate drive methods for IGBTs in bridge configurations

The insulated gate bipolar transistor (IGBT) combines the advantages of both MOS and bipolar transistor technologies into a near-ideal power semiconductor switch. Of the various application areas, the use of IGBTs in the half or full-bridge power convertor configuration is very common. Such applications have typical requirements like isolated drivers, high dv/dt stress withstand, protection against shoot-through fault, etc. This paper presents various types of gate drive circuits suitable for such situations and their relative performance under actual circuit conditions. This includes pulse-transformer circuits (where a secondary power supply is not required) for PWM control, as well as opto-isolator circuits where the secondary power supply may be derived from the inverter DC bus. Protection schemes for the IGBT that can be incorporated into the drive circuit are also discussed.<<ETX>>

A three-phase half-controlled rectifier with pulse width modulation

A three-phase pulse-width-modulated (PWM) half-controlled rectifier using a novel PWM control strategy whereby the low-order harmonic content in both the input current and the output voltage is reduced is presented. The circuit operates with a unity displacement factor at its input and uses minimum power components. The PWM strategy developed can be implemented on a three-phase half-controlled rectifier bridge with only three controlled switches to obtain PWM controlled rectification. Although the circuit operation is explained with force-commutated SCR switches, the basic controlled PWM operation is valid for any type of switch control. The circuit has wide applications ranging from rectifiers to battery chargers to motor drives. Even if an input current filter is desired, its size will be small due to the PWM pattern used. >

Performance analysis of an asymmetrical phase-converter-fed induction motor

Of the various types of single-phase-to-three-phase static power converters used to interface a three-phase motor to single-phase supply, one simple type uses an open delta connection of a sinusoidal supply and a pulsewidth modulated (PWM) waveform to feed the motor. This paper presents an analysis of the performance of the three-phase motor when fed from such an asymmetrical supply. The analysis is based on the steady-state approximate-equivalent circuit of the motor, using the method of symmetrical components. The analysis is directed toward prediction of motor phase and line currents, along with the nature of generated torque. The computer-simulated waveforms are presented and compared with results from tests on a laboratory setup.

An autoprotecting gate drive circuit for GTO thyristors

The authors present a gate drive circuit for gate turn-off thyristors which provides the combined functions of reliable switching, overcurrent protection to the device through on-state voltage monitoring, self-protection of the drive circuit by isolation against damage due to high voltage in the event of gate turn-off destruction, and galvanic isolation with good common mode rejection. The implementation details of the drive circuit used in conjunction with a gate turn-off thyristor chopper are included. >

A low distortion inverter without low-frequency magnetics for UPS application

The increasing usage of digital data processing equipment has increased the demand for small capacity, compact, low-cost and energy-efficient UPS systems as a reliable power source. UPS systems utilise a power conversion stage from the battery backup to an output AC voltage compatible with the commercial supply, conventionally using a power frequency isolated step-up transformer. Recently, high frequency power conversion techniques have been used to replace the low frequency transformer by a high frequency power stage and transformer design reducing the size and weight of the overall equipment significantly. This paper presents an alternative approach to a compact inverter for UPS application by synthesizing a low distortion stepped waveform from a high voltage DC bus, without the need for output transformer or filter. A high frequency DC to DC power converter is used to generate the high voltage DC bus from the low voltage battery using a lightweight high frequency transformer. Thus, no low frequency magnetics are necessary.<<ETX>>

Some aspects in the design of discrete MOS-bipolar Darlington power switches

The operation of a high-speed, high-power discrete MOS-bipolar Darlington switch is studied, and the influence of principal parameters is examined. It is determined that the power MOSFET should be selected with adequate safe operating area, low drain-source resistance, and low gate-charge factor. A device with a higher current rating than what is predicted is preferable. The bipolar transistor should have adequate SOA, low base-emitter drop, and high current gain. The drive circuit should have a low impedance and should provide a steady negative drive during off-period. A circuit layout with reduced wire lengths and loops should be used for the interconnections between the MOSFET and bipolar transistor as well as for drive signal connection.<<ETX>>

A New Three-Phase Current Source Inverter with Flexible PWM Capability

A new three-phase current source inverter topology is presented, consisting of three single-phase bridge inverters connected in series and feeding the isolated windings of a standard three-phase induction motor. Because a current zero in one phase now does not affect the others, it enables the implementation of a wide range of current PWM patterns for the reduction and selective elimination of torque pulsations. Furthermore, this system allows for very fast control of the fundamental load current through the use of sinusoidal PWM, a method that was not possible to implement on existing inverter topologies.

Safe operation of IGBTs in switching converters

IGBTs are fast replacing other devices in all industrial power control systems up to the hundreds of kW range. The IGBT has been considered as an efficient controllable switch which combines the advantages of both MOS and bipolar technologies. However, in order to ensure safe and reliable operation of the IGBT in actual circuit applications, numerous device aspects must be taken into account during circuit design. The paper presents a detailed study of such behaviour of the IGBT as relevant to actual application in typical switching power converters and discusses actual methods of ensuring safe operation of the IGBT by implementing these requirements into circuit design.<<ETX>>

IGBT-bipolar discrete Darlington power switches: performance and design

An IGBT (insulated-gate bipolar transistor)-bipolar discrete Darlington power switch is presented. The main high-current bipolar power switch is driven by a lower current IGBT, yielding a switch with low drive requirements and high current handling capacity. The power dissipation is lower than that of a MOS-bipolar Darlington. The behavior of such a switch is investigated using discrete device models and an important parasitic network. Some of the important design parameters of the switch and drive circuit are discussed together with possible ways of improving circuit performance. Some aspects of protection and paralleling are also presented. The analysis and discussions are supported by oscillograms from laboratory experiments.<<ETX>>