Patent ID: 8379414

Claim:
A power transistor chip, which is adaptable to an AC/DC voltage converter circuit with a transformer circuit, a pulse width modulation (PWM) circuit and a voltage divider, comprising: a first pin connecting with the transformer circuit; a second pin connecting with the PWM circuit; a third pin connecting with the PWM circuit; a fourth pin connecting with the PWM circuit; a fifth pin connecting with the voltage divider circuit and the PWM circuit respectively; a power transistor acting as a switch of said AC/DC voltage converter circuit and having a first source/drain, a second source/drain and a power transistor gate, wherein said first source/drain couples with said first pin, said second source/drain couples with said second pin and said power transistor gate couples with said third pin; and an enhancement mode metal oxide semiconductor field effect transistor (enhancement mode MOSFET) acting as a start-up circuit of said AC/DC voltage converter circuit, and having a third source/drain, a fourth source/drain and an enhancement mode MOSFET gate, wherein said third source/drain couples with said first pin, said fourth source/drain couples with said fourth pin, said enhancement mode MOSFET couples with said fifth pin.