LOW POWER SOLENOID CONTROL SYSTEM AND METHOD

• US 20090284891A1
• Filed: 05/13/2008
• Published: 11/19/2009
• Est. Priority Date: 05/13/2008
• Status: Active Grant

• Current Assignee: Automatic Switch Company (Emerson Electric Company)
• Original Assignee: Automatic Switch Company (Emerson Electric Company)
• Inventors: HALLER, John J.
• Granted Patent: US 7,911,758 B2
• Time in Patent Office: Days
• US Class Current: 361/189
• CPC Class Codes: H02M 3/155 using semiconductor devices only

Abstract

A low power solenoid control circuit including a power source in series with a sensing element and a first diode, an inductor to actuate a valve, an energy storage device to store and discharge energy into the inductor, diodes to control current flow, and switches and a controller to control the circuit. The circuit may be operated by closing a first switch, thereby allowing a source current to flow through an inductor; opening the first switch, thereby forcing a charge current to flow through an energy storage device utilizing the inductance of the inductor; repeating these steps until the energy storage device is sufficiently charged; and upon command, closing a second switch, thereby forcing a discharge current to flow from the energy storage device to the inductor causing the inductor to produce an actuating magnetic field thereby actuating a mechanical valve.

Claims

1. A method comprising the steps of:

(a) closing a single first switch, thereby allowing a source current to flow through an inductor;

(b) opening the single first switch, thereby forcing a charge current to flow through an energy storage device utilizing the inductance of the inductor;

(c) repeating steps a and b until the energy storage device is sufficiently charged;

(d) upon command, closing a second switch, thereby forcing a discharge current to flow from the energy storage device to the inductor causing the inductor to produce an actuating magnetic field thereby actuating a mechanical valve.

2. The method of claim 1, wherein the source current is insufficient to actuate the valve.

3. The method of claim 1, wherein step a is maintained until the source current reaches a first predetermined level as measured through a current sensing element.

4. The method of claim 3, wherein step b is maintained until the source current reaches a second predetermined level as measured through the current sensing element.

5. The method of claim 1, wherein steps a and b are performed a predetermined number of times.

6. The method of claim 5, the predetermined number of times is determined through a calibration process and accounts for both component tolerances and ambient temperature.

7. The method of claim 1, wherein steps a and b are performed with the second switch open.

8. The method of claim 1, further including the steps of:

(e) after the valve has been actuated, monitoring the source current through a current sensing element; and

(f) once the source current reaches a predetermined level, repeating steps a and b to recharge the energy storage device.

9. The method of claim 1, wherein the first switch is a normally closed depletion mode MOSFET.

18. The method of claim 1, wherein the first switch is a normally closed depletion mode MOSFET.

10. A method comprising the steps of:

(a) opening a first SPST switch and closing a second SPST switch, thereby forward biasing a first diode, allowing a source current to flow through a capacitor charging the capacitor;

(b) opening the second switch, thereby reverse biasing a second diode and maintaining the charge of the capacitor;

(c) closing the first switch, thereby allowing the source current to flow through a solenoid coil;

(d) opening the first switch, thereby forward biasing the second diode and forcing a charge current to flow through the capacitor utilizing the inductance of the solenoid coil;

(e) repeating steps c and d until the capacitor is sufficiently charged;

(f) upon command, closing both the first and second switches, thereby reverse biasing both the first and second diodes and forcing a discharge current to flow from the capacitor to the solenoid coil causing the solenoid coil to produce an actuating magnetic field thereby actuating a mechanical valve.

11. The method of claim 10, wherein the source current is insufficient to produce the actuating magnetic field to the actuate the valve.

12. The method of claim 10, wherein step c is maintained until the source current reaches a first predetermined level as measured through a current sensing element.

13. The method of claim 12, wherein step d is maintained until the source current reaches a second predetermined level as measured through the current sensing element.

14. The method of claim 10, wherein steps c and d are performed a predetermined number of times.

15. The method of claim 14, the predetermined number of times is determined through a calibration process and accounts for both component tolerances and ambient temperature.

16. The method of claim 10, wherein steps c and d are performed with the second switch open.

17. The method of claim 10, further including the steps of:

(e) after the valve has been actuated, monitoring the source current through a current sensing element; and

(f) once the source current reaches a predetermined level, repeating steps a and b to recharge the energy storage device.

19. A circuit comprising:

a power source in series with a sensing element and a first diode between nodes a and b;

an inductor between nodes a and c;

a first SPST switch between nodes b and c;

a second SPST switch between nodes a and d;

a capacitor between nodes b and d;

a second diode between nodes c and d; and

a controller monitoring the sensing element and operating the switches based at least in part on input from the sensing element.

20. The circuit of claim 19, wherein the first switch is a normally closed depletion mode MOSFET.