Patent ID: 7924581

Claim:
A high voltage start-up circuit with constant current control, comprising: a high voltage junction transistor, having a first source/drain, a second source/drain, and a first gate, wherein the first source/drain is coupled to a high voltage power source, and the second source/drain is coupled to an output end of the high voltage start-up circuit; a control transistor, having a third source/drain, a fourth source/drain, and a second gate, wherein the third source/drain is coupled to the first gate of the high voltage junction transistor, the fourth source/drain is grounded, and the second gate receives a control signal and is switched based on the received control signal; and a bias resistor, having one end coupled to the first gate of the high voltage junction transistor and the other end coupled to the output end of the high voltage start-up circuit; wherein, as the control transistor is turned off, the high voltage junction transistor outputs a constant current to the output end of the high voltage start-up circuit, and as the control transistor is turned on, the high voltage junction transistor stops outputting the constant current.