Patent ID: 8451571

Claim:
An overheat protection circuit for detecting an increase in temperature to protect a circuit from overheating, comprising: a p-n junction element for outputting a forward voltage that is proportional to temperature; a reference voltage circuit that comprises transistors, each transistor operating in a weak inversion region; and a voltage comparator circuit for comparing the forward voltage of the p-n junction element with an output voltage of the reference voltage circuit; wherein the reference voltage circuit comprises: a current generation circuit comprising: a first MOS transistor including a source terminal connected to a ground terminal; a second MOS transistor including a source terminal connected to the ground terminal, and a gate terminal connected to a drain terminal of the first MOS transistor, the second MOS transistor having the same conductivity type as the first MOS transistor; and a first resistive element connected between a gate terminal and the drain terminal of the first MOS transistor; a current mirror circuit connected to the current generation circuit; and a second resistive element including one terminal connected to the current mirror circuit and another terminal connected to the ground terminal, the second resistive element having the same temperature coefficient as the first resistive element, the one terminal serving as a first temperature voltage output terminal, and wherein the first MOS transistor and the second MOS transistor each operate in a weak inversion region.