| 摘要 |
<p>PURPOSE:To suppress the generation of harmonic distortion due to the change in magnetic flux, ane the fluctuation of the operating point, by making the magnetic flux density constant and adjusting a current flowing to an exciting coil through the detection of the magnetic flux of a magnetic circuit and the comparison with a reference value. CONSTITUTION:An exciting coil 9 is wound on a center pole 2a of a magnetic circuit and a magnetism detecting element 10 is installed in a magnetic gap G. After the output of the element 10 is amplified at a preamplifier 11, the output is compared with a reference voltage E at a comparison amplifier 12. After this comparison output is amplified at a power amplifier 13, it is applied to the exciting coil 9. The exciting coil 9 generates magnetic flux having opposite phase and almost the same amplitude as the magnetic flux generated with the voice coil 5. Thus, control is made so that the output of the element 10 is equal to the reference voltage E.</p> |
