| 摘要 |
PURPOSE:To prevent switching noises, by switching the CR time constant and the reference voltage level and, at the same time, by matching the switching cycle to be used for changing the output voltage to the width of resonance waveform of the switching power source after performing a variable control on the switching cycle. CONSTITUTION:The actual revolution number of a motor 6 is fed back to a microcomputer 2 after it is detected at a revolution number reading circuit 7. The microcomputer 2 compares the detected revolution number with a revolution number set at a revolution number setting circuit 1, and changes the oscillation frequency and on-time of an oscillator 3 in accordance with the difference between the two revolution numbers. By the signal from the oscillator 3, a switching power souce 4 changes the switching time into variable one, and performs a variable control on the voltage impressed upon the motor 6, and then, controls the speed of the motor 6 to the set revolution number. The switching power source 4 eliminates the occurrence of noises resulting from the switching, by coinciding the variation in switching cycle with the variation in the width of the resonance waveform. |
