Overcurrent protection structure of load driving circuit
AssigneeDenso Corporation
InventorMasahiro Tsuchida
Life of this patent
Estimating the term…
Abstract
An electrical load driving circuit is provided which includes an insulated gate transistor and a control voltage limiting circuit. The transistor works to supply the power to an electrical load selectively. The control voltage limiting circuit includes a control circuit and a switching circuit. The control circuit works to limit a voltage applied to the transistor selectively to one of a higher controlled voltage and a lower controlled voltage. The switching circuit is disposed across the transistor and closed selectively to limit the voltage applied to the transistor to the second controlled voltage through the control circuit when it is determined that an overcurrent has occurred which flows through the transistor.
Claims6
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.
Dependencies are inferred from the claim text.