Patent ID: 6788128
Filing Date: 2004-09-07
Classification: H03K

Abstract:
An electrical load driving circuit comprising:an insulated gate transistor installed in an electrical line extending between a power supply and an electrical load, said insulated gate transistor working to output a current as a function of a control voltage applied across a control terminal and a first terminal thereof; a current measuring circuit working to measure a current flowing through said insulated gate transistor; a control voltage limiting circuit disposed between the control terminal and the first terminal, said control voltage limiting circuit including a control circuit and a switching circuit, the control circuit working to limit a voltage developed across the control and first terminals selectively to one of a first controlled voltage and a second controlled voltage lower in level than the first controlled voltage, the switching circuit being disposed between the control terminal and the first terminal and closed in response to input of a close control signal to establish electric communication between the control terminal and the first terminal to limit the voltage developed across the control and first terminals to the second controlled voltage through the control circuit; and a comparator working to compare the current as measured by said current measuring circuit with a threshold current that is selected within a given current range smaller than a maximum current allowed to flow through said insulated gate transistor, when the measured current is greater than the threshold current, said comparator providing the close control signal to close the switching circuit of said control voltage limiting circuit.