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1. (WO2019028345) SYSTEM AND METHODS FOR OPERATING A SOLENOID VALVE
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WHAT IS CLAIMED:

1. A drive circuit for controlling a solenoid valve having a solenoid coil and a poppet configured to translate therein, said circuit comprising:

a first node configured to be energized by a power source at a first voltage;

a second node configured to be energized to a second voltage ;

a control circuit coupled to said first node and said second node, and configured to:

selectively couple said first node and said second node in series with the solenoid coil; and

periodically energize the solenoid coil using a pulse -width-modulated (PWM) signal having a frequency and a duty cycle configured to regulate a current conducted through the solenoid coil; and

a flyback circuit coupled to the solenoid coil and configured to energize said second node with energy stored in the solenoid coil.

2. The drive circuit of Claim 1, wherein said control circuit is further configured to:

couple the solenoid coil to said first node and said second node to apply the first voltage and the second voltage to the solenoid coil; and

adjust the duty cycle of the PWM signal to 100 percent to translate the poppet toward an open position.

3. The drive circuit of Claim 1, wherein said control circuit is further configured to:

decouple the solenoid coil from said second node;

couple the solenoid coil to said first node to apply the first voltage to the solenoid coil; and

adjust the frequency and the duty cycle of the PWM signal to maintain the poppet in an opened position.

4. The drive circuit of Claim 1, wherein said control circuit is further configured to:

decouple the solenoid coil from said second node;

couple the solenoid coil to said first node to apply the first voltage to the solenoid coil; and

adjust the frequency and the duty cycle of the PWM signal to regulate the current conducted through the solenoid coil below an opening threshold for translating the poppet to an open position, thereby maintaining the poppet in a closed position.

5. The drive circuit of Claim 4, wherein said control circuit is further configured to adjust the frequency and the duty cycle of the PWM signal to limit the current conducted through the solenoid coil to below the opening threshold, wherein the opening threshold is determined based on a measured fluid pressure differential across the solenoid valve .

6. The drive circuit of Claim 5, wherein said control circuit is further configured to:

couple the solenoid coil to said second node to apply the first voltage and the second voltage to the solenoid coil; and

increase the duty cycle of the PWM signal to 100 percent to translate the poppet toward an open position.

7. The drive circuit of Claim 6, wherein said control circuit is further configured to adjust the duty cycle of the PWM signal to increase the current conducted through the solenoid coil to above a closing threshold determined based on the measured fluid pressure differential across the solenoid valve .

8. The drive circuit of Claim 6, wherein said control circuit is further configured to increase the frequency of the PWM signal to at least 1000 Hertz prior to coupling the solenoid coil to said second node.

9. The drive circuit of Claim 4, wherein said control circuit is further configured to regulate the frequency of the PWM signal to no more than 40 Hertz.

10. The drive circuit of Claim 1, wherein said control circuit is further configured to periodically couple said first node and said second node to the solenoid coil

according to a valve-pulsing PWM signal.

11. The drive circuit of Claim 1 further comprising a current sensor configured to measure the current conducted through the solenoid coil, wherein said control circuit is further configured to adjust the frequency and duty cycle of the PWM signal based on the measured current.

12. The drive circuit of Claim 1, wherein said control circuit is further configured to adjust the duty cycle of the PWM signal to below 50 percent.

13. A method of controlling a solenoid valve having a solenoid coil and a poppet configured to translate therein, said method comprising:

energizing a first node to a first voltage using a power source ;

coupling the first node to the solenoid coil and energizing the solenoid coil using a pulse-width-modulated (PWM) signal having a frequency and a duty cycle configured to regulate a current conducted through the solenoid coil to below an opening threshold to maintain the poppet in a closed position;

energizing a second node to a second voltage with energy stored in the solenoid coil using a flyback circuit coupled to the solenoid coil;

coupling the second node to the solenoid coil and energizing the solenoid coil using a DC signal configured to increase the current to above the opening threshold to translate the poppet toward an opened position; and

coupling the first node to the solenoid coil and energizing the solenoid coil using the PWM signal having a frequency and duty cycle configured to regulate the current to above a closing threshold to maintain the poppet in the opened position.

14. The method of Claim 13 further comprising computing the opening threshold based on a measured pressure

differential across the solenoid valve.

15. The method of Claim 13, wherein energizing the first node comprises coupling the first node to a 12 Volt direct current (DC) power supply.

16. The method of Claim 13, wherein energizing the solenoid coil using the PWM signal to regulate a current conducted through the solenoid coil to below an opening threshold comprises modulating the PWM signal to at least 1000 Hertz.

17. The method of Claim 13 further comprising de-energizing the solenoid coil momentarily to reduce the current to below the closing threshold.

18. The method of Claim 13 further comprising

initiating opening of the solenoid valve according to a low frequency valve-pulsing PWM signal.

19. The method of Claim 13 further comprising measuring the current conducted through the solenoid coil.

20. The method of Claim 19 further comprising

regulating the frequency of the PWM signal according to the measured current conducted through the solenoid coil.

21. The method of Claim 19 further comprising

regulating the duty cycle of the PWM signal according to the measured current conducted through the solenoid coil.