Patent ID: 6911852

Claim:
A start-up circuit, comprising: a power supply node which receives a power supply voltage; a ground node which receives a ground voltage; a first node; a first capacitor which is connected between the first node and the ground node; a second node; a second capacitor which is connected between the power supply node and the second node, and which reduces a voltage level of the second node when a supply of the power supply voltage to the power supply node is stopped; a control circuit which includes a PMOS transistor and an NMOS transistor, wherein a source electrode of the PMOS transistor is connected to the power supply node, wherein a drain electrode and a control electrode of the PMOS transistor connected to the second node, and wherein the NMOS transistor is connected in series between the second node and the ground node; a charge and discharge circuit which is connected between the power supply node and the first node, and which discharges an electrical charge stored in the first capacitor to the power supply node in response to a falling of the voltage level of the second node when the supply of the power supply voltage to the power supply node is stopped, and which supplies an electrical charge from the power supply node to the first capacitor when the supply of the power supply voltage to the power supply node is started; a discharge circuit which is located between the first node and the ground node, and which discharges an electrical charge stored in the first capacitor to the ground node during a set period after the supply of the power supply voltage to the power supply node is started, wherein the discharge circuit comprises a third node, a third capacitor which raises a voltage level of the third node when the supply of the power supply voltage to the power supply node is started, and a switch circuit which electrically connects the first node and the ground node in response to a rising of the voltage level of the third node; and an output circuit which is connected to the first node, and which outputs a start-up signal when a voltage level of the first node becomes higher than a set voltage level.