Patent ID: 7580234
Filing Date: 2009-08-25
Classification: H02H

Abstract:
1. A current limiting circuit comprising: an input terminal; a current sensing resistor having first and second ends; a current sensing transistor; a load current limiting semiconductor switch with a current input, a current output and a control input; a capacitive load periodically discharged through an external electrical device; and timer circuits with an interval ending output signal said timer circuits timing an interval after discharge of the capacitive load and providing the interval ending output signal but only after a predetermined time interval after each periodic discharge; where the input terminal is connected to one end of the resistor, the other end of the resistor is connected to the current input of the load current limiting semiconductor switch, the current sensing transistor is connected across the resistor and is coupled to the control input of the load current limiting semiconductor switch and periodically biases that switch to a lower conductivity state in response to a periodically increasing current through the resistor that crosses a predetermined threshold, the capacitive load is connected to the current output of the load current limiting semiconductor switch and is periodically discharged, the load current limiting semiconductor switch remains in the lower conductivity state providing a first current for the capacitive load until the interval ending output signal exhibits a selected state, the load current limiting semiconductor switch then switches to a higher conducting state to charge the capacitive load with a second, higher, current.