| 摘要 |
PURPOSE:To enhance the resolution of a PWM circuit through small circuitry without increasing the rate of clock pulse CLK by comparing a carrier signal with art effective reference amount to produce a PWM signal. CONSTITUTION:When a CPU 1 is set to 16 bits and operational counters 4, 5 are set to 12 bits, the CPU 1 calculates the current diference DELTAi for each phase based on the present currents IU, IV measured by an A/D converter 6 and a current command sine wave every Te time and conducts current compensation operation such that the current control system is stabilized with high response. The operation results are stored as a 16 bit control amount S in a RAM 3 and subsequently subjected to data processing by means of 12 bit subtraction counters 4, 5 to produce a PWM output. Least significant 4 bits are then omitted from the PWM output to produce a 12 bit reference value (s) stored in the RAM 3. The number of output times, equal to the least significant 4 bits, is also generated and stored in the RAM 3. This constitution increases the PWM carrier frequency to enhance the PWM resolution. |
