Electrostatic discharge (ESD) is a source of electromagnetic disturbance. ESD usually takes place in the form of spark that occurs in the air gap between a charged body and a grounded body. Spark discharge characteristics depend on humidity，the speed of motion of a charged body with respect to a grounded body，and the structure of the charged body. An ESD event occurring during the motion of a charged body toward a grounded body has a more significant effect on electronic equipment than an ESD event occurring from a stationary charged body with the same charge. This strange phenomenon has not been well understood due to reasons such as difficulty in reproducibility. For a detailed understanding of ESD，the influence of the rate of increase in the charging voltage on the ESD from a stationary metal sphere was studied by varying the gap length between 20 μm and 80μm. The results of the experiment indicated that when no spark discharge occurred，the peak charging voltage increased with the rate of increase in the charging voltage for a given gap length. When spark discharge occurred at all applied charging voltages under each discharge condition，the average spark voltage increased with the rate of increase in the charging voltage for a given gap length.

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The switching mode DC voltage converter controlled by the integrated voltage control method works stably and has no steady state error. The basic circuit of this control method consists of an error voltage integrator and a hysteresis comparator which drives a power transistor to on/off. In this paper，we propose a new AC voltage PWM converter circuit controlled by　the integrated voltage control method. There are four operational quadrants on the voltage-current plane in this new AC voltage converter. Four power transistors arc controlled by the four hysteresis comparators driven in parallel by one error voltage integrator. It is possible to connect an R-L load of which the voltage phase and the current phase are different. It has been confirmed that the new AC voltage converter has no steady state error and a quick response time，although the control circuit is simple.

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