ELECTROSTATIC DISCHARGE PROTECTION CIRCUIT, CONTROL METHOD THEREFOR, AND SWITCHING REGULATOR USING SAME

1 . A protection circuit to protect an element against static electricity,

the protection circuit comprising:

a clamp element connected in parallel to the protected element; and

a static electricity detection circuit connected to the protected element, to detect static electricity applied to the protected element,

the static electricity detection circuit clamping a voltage applied to the protected element by turning on the clamp element when the detected static electricity exceeds a predetermined value,

the static electricity detection circuit stopping operating and turning off the clamp element in response to an externally input enable signal.

2 . The protection circuit according to claim 1 , wherein the static electricity detection circuit detects voltage applied to both ends of the protected element.

3 . The protection circuit according to claim 1 , wherein the clamp element is constructed of a MOS transistor.

4 . The protection circuit according to claim 1 , wherein the protected element is a switching transistor included in a switching regulator.

5 . A method of controlling a protection circuit for protecting an element against static electricity,

the protection circuit comprising a clamp element connected in parallel to the protected element and a static electricity detection circuit,

the method comprising:

detecting static electricity when an externally input enable signal indicates start of the protection circuit;

clamping a voltage applied to the protected element by turning on the clamp element when the detected static electricity exceeds a predetermined value; and

turning off the clamp element when the externally input enable signal indicates operation stop of the protection circuit.

6 . The method according to claim 5 , wherein the step of detecting static electricity comprises detecting voltage applied to both ends of the protected element.

7 . A switching regulator that starts operating in response to an externally input enable signal, converts an input voltage input to an input terminal to a predetermined voltage, and outputs the predetermined voltage as an output voltage from an output terminal,

the switching regulator comprising:

a switching transistor that performs switching according to a control signal input to a control electrode thereof;

an inductor to be charged with the input voltage by the switching of the switching transistor;

a rectification element to discharge the inductor when charging of the inductor by the switching transistor is stopped;

a control circuit to keep the output voltage at the predetermined voltage by controlling the switching of the switching transistor; and

a protection circuit to protect the switching transistor against static electricity,

the protection circuit including,

a clamp element connected in parallel to the switching transistor, and

a static electricity detection circuit to detect static electricity applied to the switching transistor,

the static electricity detection circuit clamping a voltage applied to the switching transistor by turning on the clamp element when the detected static electricity exceeds a predetermined value,

the static electricity detection circuit stopping operating and turning off the clamp element in response to the externally input enable signal.

8 . The switching transistor according to claim 7 , wherein the static electricity detection circuit detects voltage applied to both ends of the switching transistor.

9 . The switching transistor according to claim 7 , wherein the clamp element is constructed of with a MOS transistor.

10 . The switching transistor according to claim 7 , wherein the switching transistor is an LDMOS transistor.