Universal power adapter for converting AC/DC voltage to DC voltage

Claim 1

An electric power adapter comprising: an IEC three-wire socket connected to an AC power supply; an AC/DC power supply detector circuit to obtain an input power voltage from said IEC three-wire socket, said AC/DC power supply detector circuit comprised of a capacitor charging/discharging circuit consisted of transistors and capacitors and used in detecting the type of said input power voltage; an AC/CD power supply selector circuit, said AC/DC power supply selector circuit being consisted of two transistors and a relay, the transistors of said AC/DC power supply selector circuit being controlled by the potential at the capacitors of said AC/DC power supply detector circuit to energize said relay; an AC/DC power supply pre-treating circuit consisted of an EMI prohibition circuit and a rectifier circuit, said AC/DC power supply pre-treating circuit being controlled by said relay to directly transmit a DC power supply to a DC power supply transformer circuit or convert an AC power supply into a DC power supply for transmission to a DC power supply transformer circuit; a DC power supply transformer circuit comprised of a DC/AC converter circuit consisted of two transistor and a transformer, said DC power supply transformer circuit being to convert a DC voltage from said AC/DC power supply pre-treating circuit into an AC voltage for output to a DC output circuit; a feedback and regulating circuit consisted of a variable resistor, a voltage stabilizer, an optical coupling transistor and an integrated circuit, said variable resistor being to provide a reference voltage to said voltage stabilizer causing it to be electrically connected or disconnected, said optical coupling transistor being controlled by said voltage stabilizer to give an output signal to said integrated circuit causing it to change the pulse width of its pulse wave output to the transistors of said DC power supply transformer circuit so as to change output voltage; and a DC output circuit, said DC output circuit being consisted of a rectifier filter circuit used in converting the AC voltage from said DC power supply transformer circuit into a DC voltage for output and to produce a feedback voltage signal to said feedback and regulating circuit.