US Patent 11336191 Power supply device with low loss

A power supply device with low loss includes an input switch circuit, a transformer, a first capacitor, an output stage circuit, and a detection and control circuit. The input switch circuit generates a switching voltage according to an input voltage. The output stage circuit generates an output voltage. The output stage circuit includes a first rectifying switch element and a second rectifying switch element. The detection and control circuit detects a first output current flowing through the first rectifying switch element so as to generate a first control voltage, and it detects a second output current flowing through the second rectifying switch element so as to generate a second control voltage. The first rectifying switch element is selectively closed or opened according to the first control voltage. The second rectifying switch element is selectively closed or opened according to the second control voltage.