| 摘要 |
PURPOSE:To attain a low loop gain as the frequency of oscillated output is low by providing a function generator whose gain is smaller as the input voltage is smaller between the LPF of the inverter oscillator of PLL constitution and a voltage frequency converter. CONSTITUTION:The inverter oscillator driving a motor in a variable speed is of PLL constitution, the phase of a reference output from a crystal oscillator 1 is compared with the phase of the output from a frequency divider 3 by a phase comparator 2 and the compared output is inputted to the function generator 6 through an LPF4. The generator 6 has an input/output characteristic in which the gain is smaller as the input voltage level is smaller, the output voltage is inputted to a voltage-frequency converter 5, where the voltage is converted into a frequency and its output frequency f0 is inputted to the frequency divider 3. As the frequency f0 becomes lower by frequency-division ratio setting, the loop constitution of low gain is formed as a PLL, a stable operation is attained against external disturbance, the low frequency drive is made stable and the start of the motor is attained by the small capacity of inverter.
|
