| 摘要 |
An apparatus for controlling the inductive currents and voltages of a load when the current through the load is suddenly switched off. It comprises primarily a series connection of a diode with its cathode connected to the high voltage of the power supply, connected through a NPN transistor which is connected to the junction between the load and the electronic switch. The control electrode of the NPN is operated by a PNP transistor whose control comes from the voltage at the junction between the load and the electronic switch with respect to ground potential. Normally, the NPN transistor is cut off and blocks the flow of inductive current from the load from passing through the NPN transistor and the diode to the high voltage lead to the motor. However, when the current through the motor or other inductive load is cut off, an inductive voltage appears at the junction between the load and the switch. If this is positive with respect to ground, then the PNP transistor will conduct and will cause the NPN transistor to conduct and reactive current will flow from the junction between the load and the switch through the NPN transistor and through the diode to the high voltage end of the load. This current will flow so long as the potential of the junction between the load and the switch is higher than ground and when the reactive voltage disappears the current drops to zero and the circuit is ready for the next operation of the electronic switch.
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