PWM INVERTER CURRENT CONTROL UNIT

摘要

PURPOSE:To compensate distortion in and around a current zero zone caused by dead time by forming a comparison level voltage into rectangular waves synchronized with the triangular wave carrier frequency. CONSTITUTION:The output ec is outputted from a triangular wave carrier frequency oscillator 23, an operational amplifier 24 and a capacitor 25. A frequency demultiplier 26 divides by one half the voltage comparator output frequency of the triangular wave carrier frequency oscillator. A variable resistance 27 varies the output of the frequency demultiplier 26 to meet the length of the dead time of the power transistor base signal and outputs the comparison level voltage 2. The current can therefore be controlled in the large PWM modulation width even in and around the current zero zone. Consequently, except in the region where the PWM modulation width is small and apt to be affected by the on-delay due to the dead time, the current can be so controlled that the distortion of waveform in and around the zero zone of the motor current can be improved.