| 摘要 |
PURPOSE:To eliminate the need for a tachometer generator and a wiring therefor by detecting the terminal voltage of a DC motor during a period when an output from an inverter circuit is in OFF state. CONSTITUTION:An inverter drive circuit 6 alters an output from an inverter circuit 2 in response to a control bias from an amplifier 7. An ON-OFF signal generator 11 brings the output from the inverter circuit 2 to ON-OFF at a predetermined period. A sample holding circuit 12 samples the terminal voltage of a DC motor 5 for the OFF period of the output from an inverter when currents do not flow through a motor circuit. An error between an output signal from the sample holding circuit 12 and a motor revolution setting signal is used as a control bias for the inverter drive circuit 6. |
