| 摘要 |
PURPOSE:To simplify the circuitry, by comparing the counter-electromotive force produced from a coil which is controlled of its power supply through a switching transistor with the output frequency of a voltage controlled oscillator with a neutral point voltage, thereafter feeding the counter-electromotive force to the voltage controlled oscillator. CONSTITUTION:Output from a voltage controlled oscillation circuit 40 is frequency divided and transmitted through a power conduction switching circuit 44 comprising a logic circuit 42 and a power amplifier 43 and drive transistors Tr10-15 to drive coils 1-3. Outputs D1-D3 from the frequency division circuit 41 and outputs U1-W2 from the logic circuit 42 are fed to a phase difference detection circuit 28, then pulse timing is selected and a pulse is fed to a comparator 27. Voltages UB-WB obtained by passing the voltages U0-W0 at one terminals of the coils 1-3 through buffers 21-23 are compared 27 with a common joint voltage NB. Output from the comparator 27 is amplified 30 and fed to the voltage controlled oscillator 40, then the oscillation frequency and phase are controlled such that the phase difference will be zero. Consequently, a filter circuit is not required and power conduction timing close to the optimum timing can be achieved with respect to the counter-electromotive force of the drive coil. |
