Solenoid control apparatus

Claim 2

In an electrical system, the combination comprising: a power supply; a solenoid; a control switch connected in series with the power supply and the solenoid for energizing the solenoid with an energizing current when the control switch is rendered conductive and for deenergizing the solenoid which develops a flyback voltage when the control switch is rendered nonconductive; an auxiliary drive circuit including a boosting network connected in series with the solenoid and a flyback network connected in parallel with the solenoid; the flyback network including a Zener diode connected to limit the flyback voltage to a maximum level sufficiently high to rapidly decrease the energizing current through the solenoid as the control switch is rendered nonconductive thereby to minimize the dropout time of the solenoid; the boosting network including the parallel combination of a storage leg, a bypass leg and a reset leg; the storage leg including a storage capacitor connected to discharge through the solenoid to temporarily increase the energizing current through the solenoid as the control switch is rendered conductive thereby to minimize the pull-in time of the solenoid; the bypass leg including a bypass diode connected to shunt energizing current around the capacitor to maintain the solenoid energized after the capacitor has discharged through the solenoid; and the reset leg including a reset inductor connected to combine with the storage capacitor to form a parallel resonant circuit which charges the storage capacitor when the control switch is rendered nonconductive.

Claim 3

In an electrical system, the combination comprising: a power supply; a solenoid; a control switch connected in series with the power supply and the solenoid for energizing the solenoid with an energizing current when the control switch is rendered conductive and for deenergizing the solenoid which develops a flyback voltage when the control switch is rendered nonconductive; an auxiliary drive circuit including a boosting network connected in series with the solenoid and a flyback network connected in parallel with the solenoid; the flyback network including a Zener diode connected to establish a flyback current which limits the flyback voltage to a maximum level, the maximum level high enough to rapidly decrease the energizing current through the solenoid as the control switch is rendered nonconductive thereby to minimize the dropout time of the solenoid, and the maximum level low enough to protect the control switch from damage due to the flyback voltage; the boosting network including the parallel combination of a storage leg, a bypass leg and a reset leg; the Storage leg including a storage capacitor connected to discharge through the solenoid to temporarily increase the energizing current through the solenoid when the control switch is rendered conductive thereby to minimize the pull-in time of the solenoid; the bypass leg including a bypass diode connected to shunt energizing current around the storage capacitor to maintain the solenoid energized after the capacitor has discharged through the solenoid when the control switch is rendered conductive; and the reset leg including the series combination of a reset inductor and a reset switch, the reset inductor connected to combine with the storage capacitor to form a parallel resonant circuit when the reset switch is rendered conductive; the reset switch connected to the flyback network and response to the flyback current to place the parallel resonant circuit in oscillation for a half-cycle to charge the storage capacitor.

Claim 4

In an electrical system, the combination comprising: a power supply; a solenoid; a control switch connected in series with the power supply and the solenoid for energizing the solenoid with an energizing current when the control switch is rendered conductive and for deenergizing the solenoid which develops a flyback voltage when the control switch is rendered nonconductive; an auxiliary drive circuit including a boosting network connected in series with the solenoid and a flyback network connected in parallel with the solenoid; the flyback network including a Zener diode connected to establish a flyback current which limits the flyback voltage to a maximum level, the maximum level high enough to rapidly decrease the energizing current through the solenoid as the control switch is rendered nonconductive thereby to minimize the dropout time of the solenoid, and the maximum level low enough to protect the control switch from damage due to the flyback voltage; the boosting network including the parallel combination of a storage leg, a bypass leg and a reset leg; the Storage leg including a storage capacitor connected to discharge through the solenoid to temporarily increase the energizing current through the solenoid when the control switch is rendered conductive thereby to minimize the pull-in time of the solenoid; the bypass leg including a bypass diode connected to shunt energizing current around the storage capacitor to maintain the solenoid energized after the capacitor has discharged through the solenoid when the control switch is rendered conductive; and the reset leg including the series combination of a reset inductor and a reset switch, the reset inductor connected to combine with the storage capacitor to form a parallel resonant circuit when the reset switch is rendered conductive; the reset switch connected to the flyback network and response to the flyback current to place the parallel resonant circuit in oscillation for a half-cycle to charge the storage capacitor.

Claim 5

In an electrical system, the combination comprising: a power supply; a solenoid; a control transistor connected in series with the power supply and the solenoid for energizing the solenoid with an energizing current when the transistor is turned on and for deenergizing the solenoid which develops a flyback voltage when the transistor is turned off; an auxiliary drive circuit including a boosting network connected in series with the solenoid and a flyback network connected in parallel with the solenoid; the flyback network including the series combination of a Zener diode, a steering diode and a limiting resistor; the Zener diode connected to establish a flyback current for limiting the flyback voltage to a maximum level, the maximum level sufficiently high to rapidly decrease the energizing current through the solenoid as the transistor is turned off thereby to minimize the dropout time of the solenoid, and the maximum level sufficiently low to protect the transistor from damage due to the flyback voltage; the steering diode connected to block the energizing current and to pass the flyback current; the limiting resistor connected to develop a trigger signal in response to the flyback current; the boosting network including the parallel combination of a storage leg, a bypass leg and a reset leg; the storage leg including a storage capacitor, the storage capacitor connected to initially discharge through the solenoid from a first sense to temporarily increase the energizing current through the solenoid as the transistor is turned on thereby to minimize the pull-in time of the solenoid, and the storage capacitor connected to subsequently charge in a second sense after the capacitor has discharged from the first sense; the bypass leg including the series combination of a bypass diode and a bypass resistor, the bypass diode connected to shunt energizing current around the storage capacitor after the capacitor has discharged through the solenoid from the first sense when the transistor is turned on, and the bypass diode connected to block the discharge of the capacitor from the first sense through the bypass resistor before the transistor is turned on, the bypass resistor connected to define the energizing current shunted around the storage capacitor to maintain the solenoid energized, and the bypass resistor connected to define the extent to which the storage capacitor is charged in the second sense; the reset leg including the series combination of a reset inductor and a reset thyristor, the reset thyristor having a control electrode connected in the flyback network to turn on the thyristor in response to the trigger signal, and the reset inductor connected to combine with the storage capacitor when the thyristor is turned on to form a parallel resonant circuit which oscillates for a half-cycle to discharge the capacitor from the second sense during the initial quarter-cycle of oscillation and to charge the capacitor in the first sense during the subsequent quarter-cycle of oscillation thereby to turn off the reset thyristor.

Claim 6

In an electrical system, the combination comprising: a power supply; a solenoid; a control transistor connected in series with the power supply and the solenoid for energizing the solenoid with an energizing current when the transistor is turned on and for deenergizing the solenoid which develops a flyback voltage when the transistor is turned off; an auxiliary drive circuit including a boosting network connected in series with the solenoid and a flyback network connected in parallel with the solenoid; the flyback network including the series combination of a Zener diode, a steering diode and a limiting resistor; the Zener diode connected to establish a flyback current for limiting the flyback voltage to a maximum level, the maximum level sufficiently high to rapidly decrease the energizing current through the solenoid as the transistor is turned off thereby to minimize the dropout time of the solenoid, and the maximum level sufficiently low to protect the transistor from damage due to the flyback voltage; the steering diode connected to block the energizing current and to pass the flyback current; the limiting resistor connected to develop a trigger signal in response to the flyback current; the boosting network including the parallel combination of a storage leg, a bypass leg and a reset leg; the storage leg including a storage capacitor, the storage capacitor connected to initially discharge through the solenoid from a first sense to temporarily increase the energizing current through the solenoid as the transistor is turned on thereby to minimize the pull-in time of the solenoid, and the storage capacitor connected to subsequently charge in a second sense after the capacitor has discharged from the first sense; the bypass leg including the series combination of a bypass diode and a bypass resistor, the bypass diode connected to shunt energizing current around the storage capacitor after the capacitor has discharged through the solenoid from the first sense when the transistor is turned on, and the bypass diode connected to block the discharge of the capacitor from the first sense through the bypass resistor before the transistor is turned on, the bypass resistor connected to define the energizing current shunted around the storage capacitor to maintain the solenoid energized, and the bypass resistor connected to define the extent to which the storage capacitor is charged in the second sense; the reset leg including the series combination of a reset inductor and a reset thyristor, the reset thyristor having a control electrode connected in the flyback network to turn on the thyristor in response to the trigger signal, and the reset inductor connected to combine with the storage capacitor when the thyristor is turned on to form a parallel resonant circuit which oscillates for a half-cycle to discharge the capacitor from the second sense during the initial quarter-cycle of oscillation and to charge the capacitor in the first sense during the subsequent quarter-cycle of oscillation thereby to turn off the reset thyristor.