Output circuit for PWM inverter with no floating state

An output circuit for a PWM inverter comprising:

• a main DC power source;
• a first power device of an N-type having an input electrode, a reference electrode and an output electrode, wherein when said input electrode is positive in voltage with respect to said reference electrode, a conduction state between said output electrode and said reference electrode is established;
• a second power device of a P-type having an input electrode, a reference electrode and an output electrode, wherein when said input electrode is negative in voltage with respect to said reference electrode, a conduction state between said output electrode and said reference electrode is established, and said input electrode of the second power device is connected to the input electrode of the first power device to form a common input electrode. and said reference electrode of the second power device is connected to the reference electrode of said first power device to form a common reference electrode;
• input electrode controlling means having a first output terminal connected to said common input electrode and a second output terminal connected to said common reference electrode, the input electrode controlling means controlling a voltage of said first output terminal with respect to said second output terminal to be a positive or negative value, or to be approximately zero;
• a first photocoupler having an input light emitting device;
• and
• a second photocoupler having an input light emitting device,
• wherein when said input light emitting device of said first photocoupler is in a lighting state and said input light emitting device of said second photocoupler is in a nonlighting state, said input electrode controlling means controls the voltage of said first output terminal with respect to said second output terminal to be a positive value, and controls the voltage of said common input electrode with respect to said common reference electrode of said first and second power devices to be said positive value,
• wherein when said input light emitting device of said first photocoupler is in a nonlighting state and said input light emitting device of said second photocoupler is in a lighting state, said input electrode controlling means controls the voltage of said first output terminal with respect to said second output terminal to be a negative value, and controls the voltage of said common input electrode with respect to said common reference electrode of said first and second power devices to be said negative value,
• wherein when said input light emitting device of said first photocoupler and said input light emitting device of said second photocoupler are both in a nonlighting state, said input electrode controlling means controls the voltage of said first output terminal with respect to said second output terminal to be approximately zero, and controls the voltage of said common input electrode with respect to said common reference electrode of said first and second power devices to be approximately zero, thereby interrupting the conduction state between said output electrode and said reference electrode of said first power device, and the conduction state between said output electrode and said reference electrode of said second power device.