Patent ID: 8030978

Claim:
A soft-start circuit comprising: an input stage to receive an input voltage to provide a reference current at a first node, wherein the input stage comprises a first resistor such that the value of the reference current is the ratio of the input voltage and the first resistor; a pump stage comprising N current branches connected in parallel each comprising a current source connected to the first node and a switch connected to a second node to transfer the current from the current source to the second node while the switch operates in a connecting state and stop transferring the current while the switch operates in a disconnecting state, the switches has 2 N connecting modes performed one after another to generate an output current with a gradual increment at the second node with 2 N current levels; and a second resistor and a capacitor connected in parallel between the second node and the ground potential to receive the output current to generate an output voltage with a gradual increment with 2 N voltage levels according to the multiple of the value of output current and the second resistor at the second node.