发明授权
US4661766A Dual current sensing driver circuit 失效
双电流检测驱动电路

Dual current sensing driver circuit
摘要:
A hybridized solenoid driver circuit includes a first and second current sensing resistor. The first current sensing resistor is disposed within the flyback current path of the windings of an electrically actuated solenoid and provides a signal proportional to the flyback current only. Control of the solenoid current is effected by operation of a power transistor to controllably connect and disconnect the solenoid from the power supply at a preselected duty cycle. Operation of the driver circuit in the energization mode has no effect on the first current sensing resistor. Conversely, the second current sensing resistor is disposed within the energization current path and provides a signal proportional to the energization current only. Operation of the driver circuit in the flyback mode has no effect on the second current sensing resistor. A summing amplifier receives the first signal directly from the first current sensing resistor as it is referenced to ground; however, the second current sensing resistor is referenced to positive battery and the second signal must be passed through a current mirror prior to delivery to the summing amplifier. The signal provided by the summing amplifier is used by a control circuit to maintain the solenoid current at a desired level by constantly adjusting the duty cycle of a biasing signal delivered to the power transistor.
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