Patent ID: 7480125

Claim:
A constant voltage circuit comprising: an input terminal configured to receive an input voltage; an output terminal configured to output a constant voltage converted from the input voltage to a load; and an overcurrent protection circuit portion configured to perform an overcurrent protection operation of restricting an output current from the output terminal within a threshold current and to generate and provide logic signals comprising information on an operation state of the overcurrent protection operation to a control device disposed outside the constant voltage circuit to control the load based on the information, wherein the overcurrent protection circuit portion further comprises at least one of an output current restriction circuit and a short circuit current restriction circuit, the output current restriction circuit and the short circuit current restriction circuit each comprising: a logic signal transistor having a first source/drain region electrically connected to the input terminal; a resistance circuit electrically connected to a second source/drain region of the logic signal transistor; and a buffer circuit having an input electrically connected to the second source/drain region of the logic signal transistor and an output configured to provide the information on the operation state of the overcurrent protection operation to the control device.