Abstract: A power control apparatus for protecting an electrical circuit from excessive current and in particular for protecting it from a large and fast transition pulse caused by a rapid current polarity transition. At least two switching devices are coupled in series or in parallel between a power supply and a load. A gate signal is generated to change the switching devices from conductive state to nonconducting state in response to detection of an excessive current state. The gate signal is delayed by a predetermined period of time to change the switching devices into the nonconducting state after all of the switching devices are saturated so that the rapid current polarity transition is eliminated.

Abstract: A variable-capacitance power supply apparatus has an inexpensive structure for variably supplying a desired high power to a load by selecting an appropriate total capacitance for storing charge. A number "n" (an arbitrary integer) of series-coupled capacitors each having capacitance C are independently charged to produce an appropriate output voltage. The total capacitance Cs of the series-coupled capacitors is obtained as Cs=C/n. The total charge Q stored in the series-coupled capacitors is proportional to the total capacitance Cs. The series-coupled capacitors are selectively charged to produce an appropriate output voltage and the desired high power to be supplied to the load.

Abstract: A power control circuit for replacing a current limiting fuse in an electrical protection circuit or for switching large currents rapidly has an array of transistors, each having an identical characteristic to each other and to a device under test, to provide parallel current paths. All of the rows of the transistor array are biased "on" except for a predetermined row. A gate signal is generated to control the "on/off" state of the transistors in the predetermined row, the gate signal being a function of the presence of excessive current--holding the predetermined row of transistors biased "on" in normal operation, and turning the predetermined row of transistors "off" when excessive current is detected.