| 摘要 |
An alternatable constant current circuit is provided which supplies positive and negative polarities of rectangular wave current to an inductive load such as in an exciting circuit of an electromagnetic flowmeter and in a slanted magnetic field system of a nuclear magnetic resonance imaging device at a high current inversion speed and a low power loss, wherein the capacitance of an output capacitor in a switching power source circuit is lowered, the regenerative output voltage of the output capacitor is applied to the inductive load during the current inversion period therein via a polarity inversion circuit, further the load current is controlled by a current control circuit at a predetermined value and the output voltage of the switching power source circuit is also controlled so as to maintain the collector-emitter voltage Vce of a current control transistor in the current control circuit constant, whereby an oscillation is generated in the circuit including the inductive load and the output capacitor during the current inversion to charge the output capacitor to an excessively high voltage and further the output voltage of the output capacitor in the switching power source circuit rises due to a decrease of the collector-emitter voltage Vce thereof to thereby cause an output voltage jump-up of the output capacitor and to hasten the current inversion in the inductive load.
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