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A solenoid driver circuit for a solenoid-operated fluid dispenser in which a valve is operable to dispense a fluid under the control of the solenoid. The driver circuit receives externally applied turn-on and turn-off signals and energizes the solenoid in response to these signals. The driver circui

A solenoid driver circuit for a solenoid-operated fluid dispenser in which a valve is operable to dispense a fluid under the control of the solenoid. The driver circuit receives externally applied turn-on and turn-off signals and energizes the solenoid in response to these signals. The driver circuit is responsive to a turn-on signal to couple a pull-in voltage across the solenoid to pull in a solenoid valve armature. The driver circuit is also operable to sense the level of current in the solenoid. When the solenoid current reaches a preset peak current level, the pull-in voltage is removed from the solenoid and replaced by a hold-in voltage. When the hold-in voltage is applied to the solenoid, the driver circuit is operable to control the level of the hold-in voltage in order to maintain a preselected hold-in current in the solenoid. The driver circuit controls the solenoid current so that it makes a gradual transition from the peak solenoid current level to a steady state hold-in current level. The voltage applied to the solenoid to establish the steady state hold-in current is removed by the driver circuit in response to an externally applied turn-off signal.

대표청구항 ▼

In a solenoid-operated heated-fluid dispensing arrangement having a valve which is operable to dispense a heated fluid and a solenoid energizable to operate the valve, an improved driver circuit to energize the solenoid in response to externally applied turn-on and turn-off control signals, comprisi

In a solenoid-operated heated-fluid dispensing arrangement having a valve which is operable to dispense a heated fluid and a solenoid energizable to operate the valve, an improved driver circuit to energize the solenoid in response to externally applied turn-on and turn-off control signals, comprising: (a) means for coupling a first voltage across the solenoid in response to an externally applied turn-on control signal and for removing the first voltage from the solenoid in response to a solenoid peak current control signal; (b) means for sensing the current flowing in the solenoid to produce a sensed current output; (c) means for comparing the sensed current output of the means (b) to a peak current reference value, when the first voltage is coupled across the solenoid, to produce a solenoid peak current control signal coupled to the means (a) when the sensed current reaches the peak current reference value; and (d) means for applying a second voltage to the solenoid after the removal of the first voltage; the means (c) including a comparator circuit having a first input coupled to the peak current reference value and having a second input coupled to the sensed current output of the means (b), the comparator circuit being operable to compare the signals at the two inputs to produce a solenoid peak current control signal at an output when the input signals are equal; and latch means coupled between the output of the comparator circuit and the means (a) for coupling the solenoid peak current control signal to the means (a) until the latch means is reset after an externally applied turn-off control signal.