This invention discloses a controller of a medium voltage brushless DC motor composed of a low voltage control circuit, a three phase inversion bridge, a switch supply and a photoelectric isolator, in which, the low voltage control circuit can be mono-chip CPU and DSP or composed of special IC and surrounding elements, the grating of the upper power tube of the three-phase inversion bridge receives the control voltage signals of the low voltage control circuit by the isolator, the switch power and the three phase inversion bridge are connected with the medium voltage supply characterizing that one end of a low voltage winding in the secondary level of the transformer of the switch supply is linked to the earth, the other end provides DC supply to a low voltage control circuit by the rectified diode and a filter capacitor, the secondary level of the transformer has another low voltage winding, one end of which is connected with the positive of the medium voltage, the other provides saturated and conduction voltage to the upper power grating. |