John P. Walden

Improving the reverse recovery of power mosfet integral diodes by electron irradiation

Abstract This paper demonstrates that controlled electron irradiation of silicon power MOSFET devices can be used significantly improve the reverse recovery characteristics of their integral reverse conducting diodes without adversely affecting the MOSFET characteristics. By using 3 MeV electron irradiation at room temperature it was found that the reverse recovery charge in the integral diode could be continuously reduced in a well controlled manner from over 500 nC to less than 100 nC without any significant increase in the forward voltage drop of the integral diode under typical operating peak currents. The reverse recovery time was also observed to decrease from 3 microseconds to less than 200 nsec when the radiation dose was increased from 0 to 16 Megarads. The damage produced in gate oxide of the MOSFET due to the electron radiation damage was found to cause an undersirable decrease in the gate threshold voltage. This resulted in excessive channel leakage current flow in the MOSFET at zero gate bias. It was found that this channel leakage current was substantially reduced by annealling the devices at 140°C without influencing the integral diode reverse recovery speed. Thus, the electron irradiation technique was found to be effective in controlling the integral diode reverse recovery characteristics without any degradation of the power MOSFET characteristics.

500V BiMOS technology and its applications

The 500V junction-isolated BiMOS high voltage IC process technology recently introduced by the General Electric Company(1,2) and now in manufacturing production provides the circuit designer with a myriad of low and high voltage devices. However, to exploit the full capability of this process and apply it efficienty, it is crucial to understand and model the devices it makes available. This paper describes specifically the high voltage NPN structure, its resulting equivalent model, and shows actual device data. HSPICE device models that accurately predict the behavior of low voltage components (which may be referenced at high voltages) as a function of temperature have been developed and will be presented. We will conclude by showing generic application examples that convey the flexibility and power of this process.

Application of Transistor Emitter-Open Turn-Off Scheme to High Voltage Power Inverters

A transistor emitter-open turn-off scheme has been implemented in an experimental operating high voltage power inverter. Not only the transistor turn-off speed is greatly increased by using such a turn-off scheme but also the reverse-biased second breakdown phenomenon is eliminated. Therefore the very same device can be fully utilized for higher voltage and higher frequency applications.

Adjustable Voltage and Frequency Polyphase Sine Wave Signal Generator

An adjustable-voltage adjustable-frequency polyphase reversible-phase sequence sine wave signal generator is described. This signal generator develops the reference waveforms, in this case sine waves, that are required in the control circuits of certain types of static dc to ac inverters and ac to ac cycloconverters. Digital and linear integrated circuits together with passive components are used to generrate the output signals. The output frequency is adjustable from 0 to 500 hertz; the output voltage is adjustable from 0 to 20 volts peak-to-peak. The phase sequence is reversible on command. The theory of operation together with steady-state and transient performance data are presented.

Application of transistor emitter-open turn-off scheme to high voltage power inverters

Transistor emitter-open turn-off scheme has been implemented in an experimental operating high voltage power inverter. Using such a turn-off scheme, not only the transistor turn-off speed greatly increased but also the reverse-biased second breakdown phenomenon is eliminated. Therefore, the very same device can be fully utilized for higher voltage and higher frequency applications.