Solenoid driver and method for determining solenoid operational status

• US 5,784,245 A
• Filed: 11/27/1996
• Issued: 07/21/1998
• Est. Priority Date: 11/27/1996
• Status: Expired due to Term

• Current Assignee: Continental Automotive Systems, Inc. (Continental AG)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Hunninghaus, Roy E., Moraghan, Paul
• Primary Examiner(s): Fleming, Franz
• Application Number:
  US08/757,185
• Time in Patent Office: 601 Days
• Field of Search: 361/152-156
• US Class Current: 361/154
• CPC Class Codes: G01R 31/72 Testing of electric windings testing of transformers G01R31/62
• CPC Class Codes: H01F 2007/185 with armature position measurement
• CPC Class Codes: H01H 2047/008 with a drop in current upon closure of armature or change of inductance
• CPC Class Codes: H01H 47/002 Monitoring or fail-safe circuits
• CPC Class Codes: H01H 47/32 Energising current supplied by semiconductor device

Abstract

A solenoid driver (10) capable of detecting the operational status of a solenoid (12) including the position of an armature within a solenoid coil and an operational method. The solenoid driver (10) generates a first solenoid current within the solenoid (12) and measures a first decay time t₁. The first solenoid current is insufficient to pull the armature into the coil of the solenoid (12). A comparator circuit (22) continuously monitors the solenoid current and initiates a timer within a counter circuit (34) to compute the first current decay time. A second solenoid current is generated within the solenoid (12) that is sufficient to pull the armature into the coil of the solenoid (12). The second solenoid current is turned off and a second decay time t₂ is measured. The decay times are stored in storage registers (R1, R2) within a controller (36). The controller (36) compares the measured decay times with stored values and outputs the armature position information over a communications bus (34).

Claims

1. A method for detecting the position of an armature within a solenoid coil comprising the steps of:

providing a first solenoid current, wherein the first solenoid current is insufficient to pull the armature into the solenoid coil;

turning the first solenoid current off and measuring a first current decay time, wherein the step of measuring the first current decay time is independent of a supply voltage;

providing a second solenoid current, wherein the second solenoid current sufficient to pull the armature into the solenoid coil;

turning the second solenoid current off, while maintaining the armature in the solenoid coil, and measuring a second current decay time, wherein the step of measuring the second current decay time is independent of a supply voltage;

providing armature status reference values; and

comparing the first and second decay times with the armature status reference values to determine the position of the armature.

2. The method of claim 1, wherein the step of measuring the first current decay time comprises:

determining a start time reference by comparing the first solenoid current with a high reference value;

determining a stop time reference by comparing the first solenoid current with a low reference value;

and calculating the first current decay time by subtracting the stop time reference from the start time reference.

3. The method of claim 1, wherein the step of measuring the second current decay time comprises the steps of:

determining a start time reference by comparing the second solenoid current with a high reference value;

determining a stop time reference by comparing the second solenoid current with a low reference value;

and calculating the second current decay time by subtracting the stop time reference from the start time reference.

4. A solenoid driver capable of detecting the position of an armature within a solenoid coil comprising:

a switching circuit responsive to a control signal and energizing the solenoid coil;

a current sensor coupled to the solenoid coil and outputting a current signal;

a first reference circuit responsive to a first reference command signal and outputting a first reference signal;

a second reference circuit responsive to a second reference command signal and outputting a second reference signal;

a comparator circuit responsive to the current signal and to the first and second reference signals and generating a logic state signal;

a counter circuit responsive to the logic state signal and outputting a time signal; and

a controller outputting a power-on signal and a power-off signal to the switching circuit and outputting the first and second reference control signals to the first and second reference circuits, respectively,

wherein the controller receives the time signal and calculates a first decay time after terminating the power-on signal and calculates a second decay time after outputting the power-off signal,

wherein the first and second decay times are independent of a supply voltage and

wherein the controller outputs an armature status signal.

5. The solenoid driver of claim 4, wherein a current developed in the coil during the power-on signal is below that necessary to pull the armature into the coil.

6. The solenoid driver of claim 5, wherein a current maintained in the solenoid coil during the power-off signal is sufficient to maintain the armature in the coil.

7. The solenoid driver of claim 4, wherein the switching circuit couples the solenoid coil to a power source to energize the solenoid coil.

8. The solenoid driver of claim 4, wherein the switching circuit completes a ground connection to energize the solenoid coil.

9. A solenoid driver capable of detecting the position of an armature within a solenoid coil comprising:

a switching circuit responsive to a control signal and energizing the solenoid coil;

a current sensor coupled to the solenoid coil and outputting a current signal;

a first reference circuit responsive to a first reference command signal and outputting a first reference signal;

a second reference circuit responsive to a second reference command signal and outputting a second reference signal;

a comparator circuit responsive to the current signal and to the first and second reference signals and generating a logic state signal,

wherein the comparator circuit includes,

a first comparator coupled to the first reference circuit; and

a second comparator coupled to the second reference circuit,

wherein the first and second comparators are connected to the current sensor by a common node, and

wherein the first comparator outputs a first logic state signal responsive to the magnitude of the current signal and the first reference signal, and

wherein the second comparator outputs a second logic state signal responsive to the magnitude of the current signal and second reference signal;

a counter circuit responsive to the logic state signal and outputting a time signal; and

a controller outputting a power-on signal and a power-off signal to the switching circuit and outputting the first and second reference control signals to the first and second reference circuits, respectively,

wherein the controller receives the time signal and calculates a first decay time after terminating the power-on signal and calculates a second decay time after outputting the power-off signal, and

wherein the controller outputs an armature status signal.

10. The solenoid driver of claim 9, wherein the counter circuit comprises:

a first JK flip-flop receiving an one input from the controller and another input from an XOR gate and outputting to an OR gate;

a second JK flip-flop receiving an one input from the controller and another input from an the second comparator and outputting to the OR gate; and

a clock circuit receiving an input from the OR gate and outputting timing values to the controller.

11. The solenoid driver of claim 9, wherein the controller determines the armature position by comparing the first decay time with a first reference time standard correlated to current values less than that necessary to pull the armature into the solenoid coil and by comparing the second decay time with a second reference time standard correlated to current values greater than that necessary to maintain the armature within the solenoid coil.

12. A solenoid driver capable of detecting the position of an armature within a solenoid coil comprising:

a switch coupled to the solenoid coil, such that the solenoid coil is energizing when the switch is turned on;

a current sensor coupled to the solenoid coil and outputting a current signal;

a comparator circuit coupled to the current sensor and configured to receive reference signals from first and second reference circuits,

wherein the comparator circuit generates an output signal to a counter circuit in response to the relative magnitude of the current signal and the reference signal from the first and second reference circuits; and

a controller outputting a power-on signal and a power-off signal to the switch,

wherein the controller receives a time signal from the counter circuit and measures a first decay time after outputting the power-on signal, and measures a second decay time during output of the power-off signal,

wherein the first and second decay times are independent of a supply voltage, and

wherein the controller compares the first and second decay times to reference time standards and outputs an armature status signal.

13. The solenoid driver of claim 12, wherein a current developed in the solenoid coil during the power-on signal is below that necessary to pull the armature into the solenoid coil, and wherein a current maintained in the coil during the power-off signal is sufficient to maintain the armature in the coil.

14. The solenoid driver of claim 12, wherein the switch couples the coil to a power source to energize the solenoid coil.

15. The solenoid driver of claim 12, wherein the switch completes a ground connection to energize the solenoid coil.

16. A solenoid driver capable of detecting the position of an armature within a solenoid coil comprising:

a transistor switch coupled to a power source and supplying on and off current to the solenoid coil;

a first reference circuit and a second reference circuit;

a current sensor coupled to the solenoid coil;

a first comparator having a first input coupled to the current sensor and a second input coupled to the first reference circuit, the first comparator outputting a first logic state signal;

a second comparator having a first input coupled to the current sensor and a second input coupled to the second reference circuit, the second comparator outputting a second logic state signal;

a first counter circuit responsive to the first and second logic state signals and outputting first and second timing signals; and

a controller having a first output coupled to the transistor switch, a second output coupled to the first reference circuit, a third output coupled to the second reference circuit,

wherein the controller outputs a power-on signal to the transistor switch and receives the first and second timing signals when the armature is outside of the solenoid coil, and

wherein the controller outputs a power-off signal to the transistor switch and receives the first and second timing signals when the armature is within the solenoid coil, and

wherein the controller measures a first decay time after outputting the power-on signal and measures a second decay time when outputting the power-off signal and outputs an armature position signal, and

wherein the first and second decay times are independent of a supply voltage.

17. A solenoid driver capable of detecting the position of an armature within a solenoid coil comprising:

means for generating current pulses in the solenoid coil;

means for measuring a decay time of a first current pulse and a second current pulse,

wherein the first and second decay times are independent of a supply voltage, and

wherein the first current pulse is insufficient to pull the armature into the solenoid coil, and

wherein the second current pulse is sufficient to maintain the armature within the solenoid coil; and

means for comparing the first and second decay times with time reference standards to determine the armature position.

18. A solenoid driver capable of detecting the position of an armature within a solenoid coil comprising:

means for generating current pulses in the solenoid coil;

means for measuring a decay time of a first current pulse and a second current pulse,

wherein the first current pulse is insufficient to pull the armature into the solenoid coil, and

wherein the second current pulse is sufficient to maintain the armature within the solenoid coil; and

means for comparing the first and second decay times with time reference standards to determine the armature position, and

wherein the means for measuring includes,

a comparator circuit including a first comparator coupled to a first reference circuit and a second comparator coupled to a second reference circuit,

wherein the first and second comparators are connected to a current sensor by a common node, and

wherein the first comparator outputs a first logic state in response to the magnitude of a current signal from the current sensor and a first reference signal from the first reference circuit, and

wherein the second comparator outputs a second logic state in response to the magnitude of a current signal from the current sensor and a second reference signal from the second reference circuit.

19. The solenoid driver of claim 18, wherein means for measuring further comprises:

a counter circuit including a first counter configured to receive the first logic state from the first comparator and a first clock signal from a controller, and

a second counter configured to receive the second logic state signal from the second comparator and a second clock signal from the controller,

wherein the first counter outputs a first time signal to the controller when the current signal is less than the first reference signal, and

wherein the second counter outputs a second time signal to the controller when the current signal is greater than the second reference signal.

20. A solenoid driver capable of detecting the position of an armature within a solenoid coil comprising:

a controller circuit generating first and second current pulses to the solenoid coil,

wherein the first current pulse is insufficient to pull the armature into the solenoid coil, and

wherein the second current pulse is sufficient to maintain the armature within the solenoid coil;

a timing circuit measuring a first decay time of the first current pulse and a second decay time of the second current pulse,

wherein the first and second decay times are independent of a supply voltage; and

a logic circuit receiving the first and second decay times and comparing the first and second decay times to reference decay times standards, and outputting an armature status message.

21. The solenoid driver of claim 20, wherein the controller circuit comprises a switch coupling the solenoid coil to a power source to energize the solenoid coil.

22. The solenoid driver of claim 20, wherein the controller circuit comprises a switch that completes a ground connection to energize the solenoid coil.