The embodiment of the invention provides an electric bridge structure, a commutation circuit and a power electronic transformer. The electric bridge structure is used for directly modulating input alternating current voltage into square-wave voltage in a forward direction, so that the DC/AC conversion is omitted; the input square-wave voltage can be directly modulated into alternating current voltage (sine wave) in a reverse direction, and the voltage can be decreased by one level compared with a topological structure for rectifying medium-high frequency square-wave voltage into direct current voltage and then carrying out pulse width (PWM) modulation. The conversion efficiency of the circuit containing the electric bridge structure such as the commutation circuit is effectively improved, the circuit structure is also more compact, and then the power electronic transformer containing the commutation circuit is higher in conversion efficiency and smaller in size.