Low power solenoid with dropout detection and automatic reenergization

Abstract

The solenoid control circuit (100) performs measurements during operation to determine the condition of the solenoid (L1) and provides rapid re-energization of the solenoid (L1) upon detection of a dropout condition. A method for controlling the solenoid (L1) includes closing an input switch (Q2), cycling a low-side switch (Q1) based on a voltage drop across a resistor (R1), opening the input switch (Q2) after a time interval, closing the low-side switch (Q1), and driving a discharge switch (Q3) to control the rate of discharge current from an energy storage device (C1) to the solenoid (L1). The method includes determining the condition of the solenoid (L1) based on the time interval between activations of comparators (CMP1, CMP2) and maintaining a level of energy in the energy storage device (C1) sufficient to cause the solenoid to generate a magnetic field to operate the valve. [Selected Figure] Figure 1

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS)

[0002] This application is a PCT application Ser. No. 6 / 103,602, filed Aug. 14, 2018, the entire contents of which are incorporated herein by reference.

[0003] (STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT) Not applicable.

[0004] (Reference to appendix) Not applicable.

[0005] TECHNICAL FIELD The inventions disclosed and taught herein relate generally to control systems, and more specifically to low power control systems. [Background technology]

[0006] Patent Document 1 teaches a "control circuit for supplying a current having a high amplitude portion with an abrupt leading edge and a low amplitude portion to a load." The circuit includes a low voltage power supply connected at its input terminals and a number of actuator circuits connected in parallel between the input terminals, each of which includes a capacitor and a load. Each actuator circuit also includes a first controlled switch between the respective load and a reference line to enable the respective load to supply and store energy. A second controlled switch is provided between the capacitor line and the load line to rapidly discharge the capacitor and recirculate the load current to the load selected by the first switch, or to charge the capacitor with the recirculated load current."

[0007] The patent document 2 teaches that "a circuit arrangement for operating an electric motor, provided in the form of a solenoid actuator, for example a switched reluctance motor, allows the operation of the motor in the event of a malfunction or failure of part of the energy supply". In addition to the main battery, the circuit arrangement advantageously includes an auxiliary battery acting as a redundancy. The auxiliary battery is smaller and has a lower nominal voltage than the main battery. In order to continue to operate the electric motor in the event of a failure, a capacitor that can be switched on and off with a nominal operating voltage adapted to the nominal voltage of the main battery is connected in series with the battery. An amount of energy can be stored in the capacitor by switching the current switching through the excitation winding of the electric motor as in a switching regulator, so that the nominal voltage of the capacitor eventually exceeds the voltage of the auxiliary battery. When a sufficient amount of energy has been stored, the energy stored in the capacitor can be used to operate the electric motor for a short period of time. Electrically operated braking systems in commercial vehicles represent an important and preferred field of application of the invention."

[0008] Patent Document 3 teaches a "low power solenoid control circuit including a power source in series with a sensing element and a first diode, an inductor for actuating a valve, an energy storage device for storing and discharging energy in the inductor, a diode for controlling current flow, a switch for controlling the circuit, and a controller." "The circuit may be operated by closing a first switch to allow a source current to flow through the inductor, opening the first switch to force a charging current to an energy storage device utilizing the inductance of the inductor, repeating these steps until the energy storage device is sufficiently charged, and on command, closing a second switch to force a discharging current from the energy storage device to the inductor to cause the inductor to generate an actuating magnetic field, thereby actuating a mechanical valve."

[0009] A conventional solenoid can always be designed to operate at a power level sufficient to operate within the parameters of the design. If the magnetic attraction is destroyed, for example by mechanical shock, such a solenoid simply provides a magnetic force that tries to return to its original state. Because the energy required to attract the armature at a distance is much greater than the energy required when the parts are close together, this type of design uses much more energy than is required to hold the closed state. This consideration has led to various types of solenoids that apply a higher initial power and then reduce that power after the device reaches a final state. Some designs simply apply a significant amount of power for a short period of time and then throttle back the power, while some designs use the lower power condition to charge an energy storage device such as a capacitor (see, for example, U.S. Patent No. 5,333,332 mentioned above). One problem with both types of devices is that the energy increase only occurs when the device is first powered up, and any changes in the state of the device are not detected or acted upon thereafter. Thus, if the solenoid experiences a mechanical shock or other event that causes disengagement, the device will remain in that state without monitoring and notifying. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Pat. No. 5,532,526 [Patent Document 2] U.S. Patent No. 6,646,851 [Patent Document 3] U.S. Pat. No. 7,911,758 Summary of the Invention [Problem to be solved by the invention]

[0011] The inventions disclosed and taught herein are directed to improved systems and methods for controlling solenoids in low power applications. [Means for solving the problem]

[0012] The solenoid control circuit may include circuitry for detecting the position of the solenoid operator and re-energizing the solenoid following disengagement of the solenoid armature from the fixed pole piece to which it is magnetically attracted, such as by mechanical shock or vibration. The solenoid control circuit may include circuitry for making measurements during operation to determine the state of one or more of the magnetic components. The solenoid control circuit may include circuitry for rapidly re-energizing the solenoid after de-energization. The solenoid control circuit may include circuitry for maintaining the energy storage device in a state of full charge after initial energization. The solenoid control circuit may include circuitry for determining the state of charge of the energy storage device, which may include measuring the off-time of a controller, such as a hysteretic controller, to control the solenoid coil current.

[0013] A solenoid control circuit, such as a low power solenoid control circuit, can include a power source, such as a DC power source, one or more switches, such as an input switch, a low side switch, and a discharge switch, one or more diodes, such as a blocking diode, one or more solenoids, which can include moving and fixed parts, one or more energy storage devices, such as a capacitor, and one or more resistors, such as a current sense or other resistor. The circuit can include one or more controllers, e.g., one or more switches or gates, for controlling one or more other components of the circuit, and one or more components for communicating with the controller, and / or other components of the circuit system, e.g., analog, digital, or other comparators, which can include one or more comparators for comparing two or more values ​​or variables. The controller can receive inputs from one or more other components of the circuit and can output signals to one or more other components of the circuit. The one or more comparators can be arranged or configured to measure a voltage drop across one or more components, such as one or more resistors, and compare the voltage drop to one or more thresholds or other values, which can include, separately or in combination, in whole or in part, one or more high or maximum values, and / or one or more low or minimum values. The circuitry may be incorporated in whole or in part into a solenoid, valve, or component thereof, such as a solenoid valve for use in connection with pneumatic and / or hydraulic control systems.

[0014] A method for controlling a solenoid may include closing an input switch, energizing a low-side switch, and allowing a source current to flow through an inductor and a resistor, opening the low-side switch, such as when a voltage drop across the resistor reaches a value, such as a first, second, or other threshold, and forcing or otherwise influencing a charge current to flow, including utilizing the inductance of the inductor, to the energy storage device. The method may include closing the low-side switch when or in response to a voltage drop across the resistor reaching a second or other threshold, which may be or include a threshold less than, less than, or less than the first threshold. The method may include repeating a series of charging steps until one or more energy storage devices are charged to a degree that may be partial or full. The method may include forcing or otherwise inducing a discharge current to flow from the energy storage device to the inductor by closing a discharge switch, causing the inductor to generate an actuation magnetic field, and actuating a valve.

[0015] The method can include passing a source current through the inductor that is less than an operating or operational current of the inductor. The method can include passing a source current through the inductor that is insufficient to operate a valve coupled to the inductor. The method can include measuring a voltage drop across one or more resistors with one or more comparators, which can include a first comparator and a second comparator. The method can include measuring a time interval between switching on and / or off of one or more comparators, such as a time interval between when the second comparator switches off and when the first comparator switches on. The method can include opening an input switch when the time interval reaches a value, such as a cutoff value or other target value. The method can include measuring a number of time intervals over a series or multiple occurrences of one comparator switching off and another comparator switching on, and opening the input switch when a sum of the one or more time intervals reaches a cutoff value or other value, which can include a value corresponding to a charging time of one or more energy storage devices.

[0016] The method may include opening one or more input switches, closing one or more low-side switches, and driving one or more discharge switches in a controlled manner. The method may include driving one or more switches via pulse width modulation (PWM) for one or more pulses, and controlling a discharge current rate and the generation of a magnetic field by the inductor, where the magnetic field is or may include an actuation magnetic field or other magnetic field. The method may include opening the low-side switch and the discharge switch, and returning or otherwise directing residual energy from the inductor to an energy storage device. The method may include closing the input switch and increasing one or more thresholds, such as a second threshold, which may include maintaining a lower or higher threshold than one or more other thresholds.

[0017] The method may include measuring a current discharge time interval and increasing a current in the inductor by opening an input switch and pulsing a discharge switch when the current discharge time interval reaches a cutoff value. The method may further include opening the discharge switch. The method may include determining a state of the inductor by measuring a time interval between an activation of the second comparator and an activation of the first comparator and comparing the time interval to a threshold, the threshold may include a value representative of a dropout state of the inductor. The method may include compensating for a resistance of the inductor by adjusting the threshold based on, for example, an ambient temperature of a winding or coil of the inductor. The method may include maintaining the one or more thresholds or values ​​at a level sufficient to maintain a holding current of the inductor.

[0018] The method may include pulsing a discharge switch to maintain a level of energy in the energy storage device sufficient to cause the inductor to generate an actuation magnetic field. The method may include maintaining a level of energy in the energy storage device sufficient to cause the inductor to generate an actuation magnetic field within 100 milliseconds or another time period after an inductor dropout condition is detected. The method may include driving the discharge switch, such as by pulse width modulation, for a number of pulses appropriate to maintain a level of energy in the energy storage device sufficient to cause an inductor coupled to the energy storage device to generate an actuation magnetic field when or following the inductor dropout condition is detected. The method may include closing the discharge switch for a time sufficient to allow for measurement of the inductance without reducing the level of energy in the energy storage device below a level sufficient to cause an associated inductor to generate an actuation magnetic field. [Brief description of the drawings]

[0019] [Figure 1]FIG. 2 is a schematic diagram illustrating one of many embodiments of a solenoid control circuit according to the present disclosure. [Figure 1A] 1 is a plot illustrating capacitor discharge time versus capacitor voltage according to one of numerous embodiments of a solenoid control circuit according to the present disclosure. [Figure 2 (1)] 1 is a flow chart illustrating one of many embodiments of a method for controlling a solenoid according to the present disclosure. [Figure 2 (2)] 1 is a flow chart illustrating one of many embodiments of a method for controlling a solenoid according to the present disclosure. [Diagram 3] 1 is a set of waveforms illustrating aspects of one of many embodiments of a charging mode of a solenoid control circuit according to the present disclosure. [Figure 4] 1 is a set of waveforms illustrating aspects of one of many embodiments of a pull-in mode of a solenoid control circuit according to the present disclosure. [Figure 4A] 1 is a plot illustrating capacitor discharge time versus capacitor voltage according to one of numerous embodiments of a solenoid control circuit according to the present disclosure. [Figure 4B] 1 is a plot showing ideal constant inductance versus actual inductance according to one of many embodiments of a solenoid control circuit according to the present disclosure. [Diagram 5] 1 is a set of waveforms illustrating aspects of one of many embodiments of a hold detection mode of a solenoid control circuit according to the present disclosure. [Figure 6] 11 is another set of waveforms illustrating aspects of one of many embodiments of a hold detection mode of a solenoid control circuit according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The drawings above and the written description of specific structures and functions below are not presented to limit the scope of the applicant's invention or the scope of the appended claims. Rather, the drawings and written description are provided to teach those skilled in the art to make and use the invention for which patent protection is sought. Those skilled in the art will understand that not all features of the commercial embodiments of the present disclosure have been described or illustrated for clarity and understanding. Those skilled in the art will also understand that the development of an actual commercial embodiment incorporating aspects of the present disclosure may require numerous implementation-specific decisions to achieve the developer's ultimate goals for the commercial embodiment. Such implementation-specific decisions may include, but are not limited to, compliance with system-related, business-related, government-related, and other constraints, and may vary from time to time depending on the particular implementation, location. While the developer's efforts may be complex and time-consuming in an absolute sense, such efforts are nevertheless a routine undertaking for those skilled in the art having the benefit of the present disclosure. It will be understood that the embodiments disclosed and taught herein are susceptible to many different modifications and alternative forms. The use of singular terms, such as, but not limited to, "a," is not intended to limit the number of items. The use of relative terms, such as, but not limited to, "top," "bottom," "left," "right," "upper," "lower," "lower," "upper," "side," "first," "second" (following "third"), "inlet," "outlet," and the like, is used in the written description for clarity of reference to the drawings and is not intended to limit the scope of this disclosure or the appended claims, unless specifically indicated.The terms "couple," "coupled," "bonding," "coupler," and the like, are used broadly herein and can include any method or device for fastening, joining, adhering, fastening, attaching, joining, inserting into, forming on or in, associating, or otherwise associating with an intermediate element, piece or pieces of members, for example, mechanically, magnetically, electrically, chemically, operably, directly, or indirectly, and can further include, without limitation, integrally forming one member with another member. Coupling can occur in any orientation, including rotationally. The terms "including" and "such as" are exemplary and not limiting, and the term "can" means "can, but need not be," unless otherwise indicated. Notwithstanding any other language in this disclosure, the embodiments shown in the drawings are examples presented for purposes of illustration and description, and are not the only embodiments of the subject matter herein.

[0021] Certain embodiments of the present disclosure may be described with reference to block diagrams and / or operational diagrams of methods. It should be understood that each block of the block diagrams and / or operational diagrams, and combinations of blocks in the block diagrams and / or operational diagrams, can be implemented by analog and / or digital hardware and / or computer program instructions. Such computer program instructions may be provided to a processor of a general purpose computer, a special purpose computer, an ASIC, and / or other programmable data processing system. The executed instructions may create structures and functions for implementing the actions specified in the block diagrams and / or operational diagrams. In at least some implementations, the functions / actions / structures shown in the figures may occur in a different order than that shown in the block diagrams and / or operational diagrams. For example, two operations shown as occurring in succession may be executed substantially simultaneously or the operations may be executed in the reverse order, depending on the functions / actions / structures involved. Computer programs for use with or by one or more of the embodiments disclosed herein may be written in an object-oriented programming language, a conventional procedural programming language, or a low-level code such as assembly language and / or microcode. Such programs may execute as a stand-alone software package or as part of another software package, entirely on a single processor and / or across multiple processors.

[0022] Applicant has created a system and method for detecting the position of a solenoid and rapidly re-energizing the solenoid after it has been de-energized. The low power solenoid drive circuit can determine the state of the solenoid and can be insensitive to fluctuations in operating voltage. The low power solenoid drive circuit can maintain an energy storage device at a full charge or other charge state sufficient to operate the solenoid after initial energization.

[0023] FIG. 1 is a schematic diagram illustrating one of many embodiments of a solenoid control circuit according to the present disclosure. FIG. 1A is a plot showing capacitor discharge time versus capacitor voltage according to one of many embodiments of a solenoid control circuit according to the present disclosure. FIG. 2(1) and FIG. 2(2) are flow charts illustrating one of many embodiments of a method of controlling a solenoid according to the present disclosure. FIG. 3 is a set of waveforms illustrating an aspect of one of many embodiments of a charge mode of a solenoid control circuit according to the present disclosure. FIG. 4 is a set of waveforms illustrating an aspect of one of many embodiments of a pull-in mode of a solenoid control circuit according to the present disclosure. FIG. 4A is a plot showing capacitor discharge time versus capacitor voltage according to one of many embodiments of a solenoid control circuit according to the present disclosure. FIG. 4B is a plot showing ideal constant inductance versus actual inductance according to one of many embodiments of a solenoid control circuit according to the present disclosure. FIG. 5 is a set of waveforms illustrating an aspect of one of many embodiments of a hold detection mode of a solenoid control circuit according to the present disclosure. 6 is another set of waveforms illustrating one aspect of one of many embodiments of a hold detection mode of a solenoid control circuit according to the present disclosure.

[0024] In at least one embodiment, a solenoid control circuit 100 according to the present disclosure can include a power source V1, such as a direct current (DC) power source, an input switch Q2, one or more blocking diodes D1, D2, D3, D4, a low-side switch Q1, a discharge switch Q3, a solenoid L1, an energy storage capacitor C1, and one or more resistors R1, such as a current sensing resistor. The circuit 100 can include one or more controllers 102 for controlling one or more other components of the circuit, such as one or more of the switches Q1-Q3. The controller 102 can receive inputs from one or more other components of the circuit, and the circuit can include one or more comparators CMP1, CMP2, such as analog comparators or other comparators. In at least one embodiment, comparators CMP1 and CMP2 may be arranged to measure a voltage drop across resistor R1 and compare that voltage drop (VR1) to one or more thresholds, which may include, individually or in combination, in whole or in part, one or more high or maximum values ​​and / or one or more low or minimum values. Circuit 100 may be incorporated in whole or in part into a solenoid valve or component thereof, such as a solenoid valve for use in connection with a pneumatic and / or hydraulic industrial control system. In at least one embodiment, circuit 100 may be configured to operate in a number of different modes. Such modes may include, but are not limited to, a charge mode to charge capacitor C1, a pull-in mode to activate or pull in solenoid L1, a hold-detect mode to hold solenoid L1 in an activated position and detect whether a dropout has occurred, some of the aforementioned modes, and / or one or more other modes, individually or in combination, in whole or in part. One or more of the aforementioned modes will now be described in further detail.

[0025] In the charging mode, the solenoid L1 can be operated at an energy level below a level sufficient to draw in a device, which can be any level according to the implementation of the circuit 100. The switch Q2 can be placed in an on state (i.e., closed state) that can electrically couple the power source V1 to the solenoid L1. The voltage VR1 across the resistor R1 can be 0 volts at initialization, and the switch Q1 can be on, for example, when VR1 is below a lower threshold (THRSH LOW) or lower limit at which the comparator CMP1 signals the controller 102 to close the switch Q1, allowing current to flow through the solenoid L1 and the resistor R1. VR1 can turn off the switch Q1 when it reaches an upper threshold (THRSH HIGH), such as an upper threshold or upper limit, at which the comparator CMP2 signals the controller 102 to open the switch Q1. When switch Q1 turns off, the current in solenoid L1 can flow through capacitor C1, adding charge, and then continue to flow through resistor R1. This can create a potential drop, or voltage drop VR1, across resistor R1. As the current decreases and the energy stored in the magnetic field of solenoid L1 dissipates (i.e., the discharge cycle), the value of VR1 can decrease. When VR1 reaches a value below THRSH LOW, comparator CMP1 can close switch Q1 again and the charge cycle can resume.

[0026] In at least one embodiment, during the above discharge cycle, the time interval between when comparator CMP2 switches off and when comparator CMP1 switches on can be measured. Such time interval is related to the value of the inductance and resistance of the coil of solenoid L1 as well as the amount of charge stored in capacitor C1. More specifically, voltage source V1 can be connected to inductor L1, such as the top (see example in FIG. 1), via switch Q2 and diode D3. The bottom of inductor L1 (with switch Q1 off) can be connected to the top of storage capacitor C1 via diode D1. The bottom of capacitor C1 can be connected to sense resistor R1. When comparator CMP2 is turned off (Q1 is turned off), a current can flow in inductor L1 (e.g., a peak current (Ip) of about 22 mA). That current is forced to continue flowing by the collapsing magnetic field of inductor L1, but can flow to capacitor C1 to charge it. This process can continue until a lower trip point of comparator CMP1, which can be Imin (e.g., 2mA in this example, but this is just one example among many). The solenoid coil of inductor L1 can have an internal resistance in addition to its inductance that forms the natural time constant (L / Rcoil) of inductor L1. This natural time constant can vary from inductor to inductor. The time to discharge the inductor current can be determined according to the following equation (Equation 1):

[0027]

number

[0028] In Equation 1, t is the discharge time, L is the inductance, Rcoil is the resistance of the coil of inductor L1, Vcap is the voltage across capacitor C1, V1 is the source voltage, Vdiode is the voltage across diode D1, Imin is the lower trip point of comparator CMP1, and Ip is the peak current through inductor L1. For illustrative purposes, an exemplary plot of discharge time t versus voltage Vcap across capacitor C1 is shown in FIG. 1A. In an embodiment that concerns terminating the process of charging C1 with a voltage of, for example, 180-200V, the effect of, for example, a change in V1 (which may typically be 15-30V) will generally not have a significant effect on the measurement. Furthermore, temperature compensation of Rcoil can be repeated by measuring this discharge time and stored energy within C1. These parameters can be measured and reproduced across manufacturing tolerances of solenoids used in commercial or other physical embodiments of the present disclosure.

[0029] Thus, the level or amount of energy available in capacitor C1 can be ascertained by measuring this time interval. In at least one embodiment, such time interval can be compared to a value (e.g., about 250 microseconds (μs)) obtained by measurement for the particular capacitor (which can be any capacitor) utilized in connection with the implementation of circuit 100. This value corresponds to the amount of charging time required to achieve a charge level, such as a full charge or other charge, which can be or include a sufficient charge to draw in a solenoid of circuit 100. In this manner, it can be determined when the charging cycle has charged capacitor C1 sufficiently to draw in solenoid L1, and the charging process can optionally be terminated until a later time or in another manner. At this point, capacitor C1 can be charged to a target voltage, such as, for example, about 200 VDC or another voltage, which can be any voltage according to a particular implementation of the present disclosure. Exemplary waveforms associated with the steps of the charging mode described above are shown in FIG. 3 for illustrative purposes. The waveforms correspond to only one of many examples of physical implementations of the present disclosure and can vary from implementation to implementation depending on the components and configurations utilized. More specifically, in Figure 3, waveform VC1 illustrates the voltage VC1 across exemplary capacitor C1 as it is being charged through on and off cycles of switch Q1 based on the measured current flowing through inductor L1 via sense resistor R1. The value of VC1 can be increased in steps each time switch Q1 is turned off. The energy delivered to each step can be determined according to the following equation (Equation 2):

[0030]

number

[0031] In Equation 2, E is the energy delivered to the capacitor C1 during each on-off cycle of the switch Q1, L1 is the inductance of the inductor L1, and Ip is the peak current flowing through the inductor L1. The switch Q2 can be turned on during charging to provide a connection to the power source V1. The state of the switch Q1 can be controlled by the controller 102 in response to comparators CMP1, CMP2 arranged to measure the voltage drop VR1 across the resistor R1. As shown in the Q1 gate waveform of FIG. 3 and described above, the capacitor voltage VC1 can increase as the off-time of the switch Q1 decreases. As shown in the current-in-coil waveform of FIG. 3, during the charging phase, the resulting current in the inductor L1 can rise or gradually increase between two current values ​​that represent appropriate current thresholds for the inductor L1. These thresholds can be any thresholds according to the implementation of the present disclosure. At the end of the charging cycle, the capacitor C1 can be discharged. In this case, as capacitor C1 discharges, voltage VC1 decreases (see VC1 waveform), and the current in inductor L1 can correspondingly ramp up to pull in the solenoid, as discussed further below and shown in the current-in-coil waveform of Figure 3. In at least one embodiment, switch Q2 can be disconnected from power supply V1 at this point, as shown in the Q2 gate waveform of Figure 3.

[0032] In at least one embodiment, in charging mode, THRSH LOW can be 20 millivolts (mV) and THRSH HIGH can be 220 mV. However, this need not be the case, as these values ​​are examples of one of many implementations of the circuit 100 and are discussed herein for purposes of explanation, not limitation. THRSH LOW and THRSH HIGH in charging mode can have any value or values ​​according to implementations of the present disclosure and can (and may) vary between implementations. The setting of the comparator thresholds THRSH HIGH and THRSH LOW is typically based on the required coil current for the solenoid used in the physical implementation of the present disclosure, which can be any solenoid suitable for such implementation. The thresholds are coordinated with the resistance of the corresponding sense resistor R1, which can likewise be varied from implementation to implementation. The operating limit of the coil current can be effectively based on the applicable threshold voltage value divided by the resistance value of R1. In the exemplary implementation discussed herein, one of many implementations, the high and low thresholds during this phase are 220 mV and 20 mV, respectively, and the value of R1 is 10 Ω, resulting in 22 mA and 2 mA, respectively. In other implementations of the present disclosure, including alternative solenoid structures, the above values ​​may be changed and / or adjusted to achieve operation of circuit 100 as described herein.

[0033] Moving now to the pull-in mode, in at least one embodiment, the solenoid L1 can be disconnected from the power supply V1 by turning off or opening the switch Q2. The switch Q1 can be turned on and Q3 can be operated to control one or more rates of change or other attributes of the circuit 100. For example, in at least one embodiment, the switch Q3 can be driven in a pulse width modulation (PWM) mode to discharge the energy stored in the capacitor C1 and control the turn-on current waveform of the following rate: regulating the performance of the solenoid as it raises and pulls in the solenoid L1. In at least one embodiment, Q3 can be driven for one or more pulses, which can include a fixed or variable number of pulses according to embodiments of the present disclosure and can be any number of pulses (discussed further below). During this time, the solenoid can be pulled in. Once the PWM period is over, the switches Q1 and Q3 can be turned off to return the residual energy stored in the inductor L1 to the capacitor C1.

[0034] Exemplary waveforms associated with the above-mentioned pull-in mode steps are shown in FIG. 4 for illustrative purposes. In at least one embodiment, for example, in pull-in mode, Q3 may be driven in PWM mode with a 70% duty cycle and 1 ms period. This need not be the case, as these values ​​are an example of one of many implementations of circuit 100 and are described herein for illustrative purposes, not limitation. The PWM variables may have any one or more values ​​according to implementations of the present disclosure and may vary between implementations. In at least one embodiment, the purpose of the PWM pull-in phase is to adjust the solenoid current during pull-in such that the duration and amplitude of the current optimally pulls in the solenoid using the least amount of current. The number of pulses and duty cycle may be adjusted for the duration of the pull-in, as well as the amplitude, based on applicable parameters, which may include electrical parameters (i.e., inductance and resistance) and mechanical parameters (i.e., moving mass, spring force and friction). By observing the solenoid current waveform during development of a physical implementation or otherwise, these parameters may be varied to change the shape of the observed waveform. If the duty cycle is too high, the solenoid may discharge the capacitor too quickly and for a sufficient amount of time, the current may not rise high enough to cause the solenoid armature to move sufficiently. Similarly, if the duty cycle is too low, the solenoid current may not achieve the proper pull-in value. As the solenoid armature moves and comes to rest, a change in shape is seen in the current waveform (characterized by an inflection point in the solenoid current). The duration of the pulses can be configured to ensure that such movement occurs. The PWM duty cycle can also vary the rate of energy extraction from the capacitor. This includes allowing or controlling the extraction or dissipation of energy at a pace consistent with the mechanical response of the device.In at least one embodiment, the duty cycle can be varied at one or more points of the pull-in phase in order to shape the current waveform in a more optimal manner according to the particular physical implementation at hand.

[0035] Turning now to the hold detection mode, in at least one embodiment, this mode of operation of the circuit 100 can include multiple phases. In the first phase, which can be an initial phase, for example, switch Q2 can be turned on and switch Q3 can be turned off. THRSH LOW can be set to a different value (e.g., 140 mV) and Q1 can be controlled by toggling the signals from comparators CMP1 and CMP2. VR1 can be cycled between THRSH LOW and THRSH HIGH (e.g., 140 mV to 220 mV in the exemplary case discussed herein, which is one of many possibilities). Increasing the value of THRSH LOW during the current mode, as compared to the value of THRSH LOW used during the charging mode described above, can at least partially ensure that the current in the coil of the solenoid L1 does not fall below the holding current IH of the solenoid L1. As with the original charging mode, the current discharge time interval can be measured and compared to an experimentally observed value (e.g., 55 μs in the exemplary case). This value can be different from the value utilized during the charging mode. The reason is that, for example, the inductance value of the coil of solenoid L1 is changing as the solenoid moves from open to closed.

[0036] During the hold detection mode, the capacitor voltage VC1 can be replenished, which can be done in a manner similar to the initial charge mode described above. However, the minimum current Imin can be made higher (e.g., 14 mA in the example discussed herein) to prevent the solenoid armature from disengaging from the corresponding fixed pole piece. According to Equation 1 above, since the minimum current Imin is now higher, it takes less time to discharge the capacitor C1, and it is appropriate to shorten the time t. For illustrative purposes, an exemplary plot of the voltage Vcap across the capacitor C1 versus the discharge time t is shown in FIG. 4A. Once the target current discharge time interval is reached, the second phase of the hold detection mode can be initiated.

[0037] In the second phase, switch Q2 can be turned off, switch Q1 can be turned on, and switch Q3 can be pulsed to discharge energy from capacitor C1 (e.g., once for 500 μs in the implementation discussed herein, but other scenarios are possible). This short pulse, or another pulsing of switch Q3, can discharge a small amount of energy from capacitor C1, causing an increase in the current in solenoid L1. Since the energy extracted from capacitor C1 at this point is small, only a small voltage drop occurs, and even if solenoid L1 drops out, there is enough energy left in capacitor C1 to quickly energize solenoid L1 again. At the end of the pulse, with switch Q3 turned off, a current can be discharged through solenoid L1, diode D4, switch Q1, and resistor R1. This current can follow an exponential curve with a time constant based on the inductance and resistance of solenoid L1. In other words, when the inductance of the solenoid coil is treated as a constant value, the equation for measuring the position of the armature can be obtained based on the following equation (Equation 3).

[0038]

number

[0039] In Equation 3, the variables correspond to those discussed above with respect to Equations 1 and 2. The inductance of the solenoid divided by the resistance of the coil is the definition of the induction time constant, as shown by the solid line in FIG. 4B. However, when dealing with an actual solenoid made from ferromagnetic steel components, the time response of the current can be affected by other factors, including nonlinearities due to the BH curve (aka magnetization curve) of the ferromagnetic material, and eddy current effects created by the rate of change of magnetic flux linkage in the ferromagnetic material as the solenoid is turned on and off. These can cause the time response curve to not follow the relatively simplified Equation 3 above, which is a classical solution to a first order differential equation, which is an exponential decay curve. The above analysis can be performed, for example, using finite element analysis (FEA) software with a transient solver. The actual values ​​determined by testing in the exemplary embodiments described throughout this disclosure are as follows, and are shown by the dashed line in FIG. 4B: In this case, which is only one of many possible implementations of the present disclosure, when switch Q3 is pulsed for 500 μs, the current in the solenoid rises to a value of 51 mA. At the end of the 500 μs pulse, Q3 turns off and the current in L1 begins to decay from Ip (51 mA). When the value falls below Imax (22 mA), the controller 102 starts a timing cycle due to comparator CMP2 changing state, which continues until comparator CMP1 changes state at Imin (14 mA), thus ending the timing cycle. It is advantageous to make this measurement by boosting the current through a 500 μs capacitive discharge and then measuring the timing at a lower current level. Because the discharge equation is exponential, measuring later in the curve results in a larger measurement because the rate of change of current is smaller, thus providing a higher measurement resolution. For example, in the same exemplary circuit, if the pulse of switch Q3 is shortened from 500 μs to 50 μs, the current in inductor L1 does not have time to rise above Imax (22 mA). Under those conditions in the tested solenoid, the discharge time measured at the minimum air gap position is 10 ms and the discharge time measured at the maximum air gap position is 6.5 ms, a difference of 3.5 ms.However, with a 500 μs pulse and an Ip of 51 mA, the minimum gap position changes to a discharge time of 15.1 ms and the maximum gap position changes to a discharge time of 9 ms, a difference of 6.1 ms, almost double what it was before. Furthermore, the observed measurements can be more reproducible and stable in the latter configuration than in the former configuration.

[0040] The voltage VR1 developed across resistor R1 can be detected by comparators CMP1 and CMP2. As VR1 decays, it can first trigger comparator CMP2 THRSH HIGH (e.g., 220 mV), at which point a time counter can be started. As VR1 continues to decay, it can subsequently or later trigger comparator CMP1 THRSH LOW (e.g., 140 mV), at which point the counter can be stopped. The accumulated time value stored in or otherwise associated with the counter can be proportional to the inductance of solenoid L1. In turn, the inductance of solenoid L1 can be related to the relative positions of the solenoid's fixed and movable pole pieces. That is, the stroke of the solenoid will change the working air gap in the solenoid's magnetic circuit. This changes the magnetic reluctance of the magnetic path. This magnetic reluctance increases with a larger air gap (and flux linkage decreases with increasing air gap). The current decay waveform can be experimentally observed for two positions (i.e., closed and open positions corresponding to a larger air gap in the solenoid and a smaller air gap in the solenoid, respectively) and two values ​​of the measurement time can be determined. As described above for this example, these values ​​were 9 ms for the larger air gap and 15.1 ms for the smaller air gap. Thus, for example, a value of 11 ms can be selected as the threshold value, which can have a sufficient margin to detect the larger air gap of the solenoid in a dropout state. In this way, it can be seen that the contents of the counter or the accumulated time value can be compared to a threshold value representing the state of the solenoid in a dropout state. This threshold value can be any solenoid used to implement the circuit 100 according to the present disclosure.

[0041] In at least one embodiment, the resistance of the solenoid L1 can affect the time value stored or obtained via the counter, and the circuit 100 can include circuitry to compensate for this effect based on the ambient temperature of the coil (or winding) of the solenoid L1. This compensation can be achieved in whole or in part by analog or digital means, separately or in combination. For example, the analog means can include a temperature compensation network placed in series with the solenoid L1 and configured to counteract the resistance variations described above. As another example, the digital means can include an ambient temperature sensor readably coupled to the controller 102, and a value or threshold in the counter can be adjusted to compensate for the change in resistance.

[0042] If a drop-out condition of the solenoid L1 is detected, the circuit 100 can re-enter the charging and pull-in modes to return the solenoid to the proper state. In at least one embodiment, the time interval of the off-time of the controller 100 (which may be a hysteretic controller) may be very close to a limit since there may still be stored charge available in the capacitor C1 when the circuit 100 re-enters the charging mode. As a result, a limited number of charging cycles may need to occur before the solenoid is re-energized. Exemplary waveforms associated with the steps of the hold detection mode described above are shown in FIG. 5 for illustrative purposes. More specifically, if a drop-out condition is detected in the hold detection mode, the logic circuitry in the controller 102 may re-enter the charging and pull-in modes if the solenoid needs to be pulled in. The number of charging pulses required may depend on the value of the charge stored in the capacitor C1. As discussed elsewhere in this disclosure, the state of charge of the capacitor may be determined by measuring the off-time of the pulses occurring during the charging phase. If the value of the charge stored on the capacitor at the time of dropout detection is close to the amount required to pull in the solenoid, the number of charging cycles required will be relatively small as a comparison condition, such as if the system was de-energized for a period of time to allow the charge on the capacitor to dissipate to zero or another value lower than the charge required to pull in the solenoid, and then re-energized. Thus, it can be seen that the systems and methods of the present disclosure can quickly re-energize the solenoid under a dropout condition, or as another example, when the solenoid is called upon to quickly re-operate after the system is de-energized for a short period of time (e.g., 5 seconds or less) and the solenoid is re-energized.

[0043] In at least one embodiment of the present disclosure, the circuit 100 can be configured to monitor or observe the waveform of the current drawn during operation to detect or determine one or more characteristics of the system or its components. For example, the circuit 100 can be configured to supply power to the solenoid L1 and determine diagnostic information regarding the solenoid by monitoring the current being supplied during operation. In at least one embodiment, the circuit 100 can be configured such that current is only drawn from the power source V1 when the switch Q2 is turned on. Furthermore, in the context of the various modes detailed above, the circuit 100 can be configured such that the switch Q2 is only turned on during one or more of the main charging modes and during the charging phase occurring during the hold detection mode. The duration of these charging pulses can be proportional to the voltage seen at the input to the solenoid L1, and further, the interval between occurrences of the charging pulses during which no current is being drawn (i.e., the solenoid L1 is utilizing its internally stored energy) can be related to the inductance of the solenoid L1. The circuit 100 can be configured to utilize the charge pulse duration and interim intervals to detect or otherwise determine information regarding the position of the solenoid L1, for example, as shown in FIG. 6. FIG. 6 is similar to FIG. 5 described above, but an example input current waveform showing the current drawn from the power supply V1 is shown instead of the coil current. As shown in FIG. 6, during the detection phase of the hold detection mode, the input current goes to zero. Additionally, as described above, the length of the detection phase can vary based on the state of the solenoid stroke. In at least one embodiment, for example, the controller 102 can be configured to monitor the current being drawn from the power supply V1 and make a determination regarding the position of the solenoid based on the duration of the zero current period.

[0044] As will be appreciated by those skilled in the art having the benefit of this disclosure, the circuit system and corresponding method disclosed herein have the advantage of simple circuitry and non-critical measurement techniques. An embodiment utilizing a relatively high current pulse followed by a lower detection threshold current can be configured so that one or more measurements are made along a relatively flat portion of the exponential curve. This can generate a larger time change that provides for detection of the difference in position of the magnetic components of the solenoid without requiring as critical circuitry as required by some conventional methods. There is a limit to how low the current can be in this regard, since if the current in the solenoid coil gets too low, the solenoid will drop out. However, generating a current pulse with a capacitor in the manner described herein can make the detection threshold large enough to hold the magnetic components of the solenoid together while still providing a basis for good detection.

[0045] Also, as will be appreciated by those of ordinary skill in the art having the benefit of this disclosure, one or more of the detection methods disclosed herein may include the inductance of the solenoid and may further include ascertaining the state of the solenoid while being relatively insensitive to the amount of change in the operating voltage. The systems and methods of the present disclosure may be particularly useful, for example, in applications requiring intrinsically safe devices or applications where energy is inherently or otherwise limited. Additionally, the systems and methods of the present disclosure, which may include the controller 102 or other system components or circuits described herein, may be configured to communicate one or more states of the solenoid, separately or in combination, in whole or in part, to another control system or another type of system, including via a wired or wireless interface.

[0046] In at least one embodiment, an additional feature of the disclosed system and method can include the ability of the circuit to quickly re-energize the solenoid after de-energization. For example, there is an application in the process industry. In this case, the health of a large pneumatically operated valve, such as a valve that is normally energized for a long time, is tested by de-energizing the pilot control valve, checking with a valve indicator if the valve shifts, and then re-energizing the pilot control valve after a very short period of time (e.g., less than 100 ms). This process may be done to ensure that the valve can move, i.e., that the valve is not locked in an open mode and cable closes. While this test protocol may not be an issue with a normal power pilot valve, it can be an issue with a low power pilot valve that uses an energy storage device to provide auxiliary opening power. In at least one embodiment, the time required to charge the energy storage device can exceed 750 ms, which can prevent a rapid re-energization of the valve and make such valves unusable with the above test protocol. In at least one embodiment, the disclosed system and method can allow the energy storage device to be maintained in a fully charged state after it is initially energized. This means that if the valve is subsequently de-energized as described in the test protocol above, there may already be enough energy available in the storage device to quickly re-energize the valve, for example within the 100 ms requirement.

[0047] Other and further embodiments utilizing one or more aspects of the above-described systems and methods may be devised without departing from the spirit of applicant's disclosure. For example, the systems and methods disclosed herein may be used alone or to form one or more parts of other valves, valve components, and / or fluid control systems. Furthermore, the various methods and embodiments of the control system may be included in combination with each other to produce variations of the disclosed methods and embodiments. A description of a singular element may include a plurality of elements and vice versa. A reference to at least one item followed by a subsequent item may include one or more items. Also, various aspects of the embodiments may be used in conjunction with each other to achieve the goals of the disclosure.

[0048] Unless the context dictates otherwise, the words "comprising," "including," "having" (including variations and conjugations such as "comprising," "including," "having") include at least the recited elements or steps, or groups of elements or steps, or their equivalents, and do not exclude a greater quantity or other elements or steps, or groups of elements or steps, or their equivalents. Devices, apparatuses, and systems can be used in many orientations and orientations. The sequence of steps can be performed in various orders, unless otherwise limited. Various steps described herein can be combined with other steps, interleaved among the recited steps, and / or divided into multiple steps. Similarly, elements are described functionally and can be embodied as separate components and / or combined into components having multiple functions.

[0049] The embodiments are described in the context of preferred and other embodiments, and not all embodiments of the applicant's disclosure are described. Obvious modifications and variations to the described embodiments are available to those skilled in the art having the benefit of this disclosure. The disclosed and undisclosed embodiments are not intended to limit or restrict the scope or applicability of the applicant's disclosure, but rather, in accordance with patent laws, the applicant intends to fully protect all such modifications and improvements that come within the scope or range of equivalents of the claims.

Claims

1. (a) energizing a low-side switch by closing an input switch, thereby allowing a source current to flow through an inductor and a resistor; (b) forcing a charging current through an energy storage device utilizing the inductance of the inductor by opening the low-side switch when a voltage drop across the resistor reaches a first threshold; (c) closing the low-side switch when the voltage drop across the resistor reaches a second threshold, the second threshold being lower than the first threshold; and (d) repeating steps a, b and c until the energy storage device is charged; (e) forcing a discharge current to flow from the energy storage device to the inductor by closing a discharge switch, causing the inductor to generate an actuation magnetic field, thereby actuating a valve; A method comprising: measuring the voltage drop across the resistor with a first comparator and a second comparator; measuring the time interval between when the second comparator switches off and when the first comparator switches on; opening the input switch when the time interval reaches a cutoff value; The method further comprising:

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

3. 2. The method of claim 1, further comprising measuring a plurality of time intervals over a plurality of occurrences that the second comparator switches off and the first comparator switches on.

4. The method of claim 3 , further comprising the step of opening the input switch when the sum of the plurality of time intervals reaches the cutoff value, the cutoff value corresponding to a charging time for the energy storage device.

5. (f) opening the input switch; (g) closing the low-side switch; (h) controlling the discharge current rate and the generation of the actuation magnetic field of the inductor by driving the discharge switch in a pulse width modulation (PWM) mode for a number of pulses; The method of claim 1 , further comprising:

6. The method of claim 5 , further comprising the steps of opening the low-side switch and the discharge switch, and returning residual energy from the inductor to the energy storage device.

7. The method of claim 6 , further comprising the steps of closing the input switch and increasing the second threshold, wherein the second threshold remains lower than the first threshold.

8. (i) increasing a current in the inductor by opening the input switch and pulsing the discharge switch when the time interval reaches the cutoff value; (j) opening the discharge switch; determining a state of the inductor by measuring a time interval between an activation of the second comparator and an activation of the first comparator and comparing the time interval to a threshold; The method of claim 7 further comprising:

9. 9. The method of claim 8, wherein the threshold is a time interval representative of a dropout condition of the inductor, further comprising compensating for a resistance of the inductor by adjusting the threshold based on an ambient temperature of a winding of the inductor.

10. The method of claim 7 further comprising the step of maintaining the second threshold at a level sufficient to maintain a holding current in the inductor.

11. 8. The method of claim 7, further comprising the steps of pulsing the discharge switch to maintain a level of energy in the energy storage device sufficient to cause the inductor to generate an actuation magnetic field, and further comprising the steps of maintaining a level of energy in the energy storage device sufficient to cause the inductor to generate an actuation magnetic field within 100 milliseconds of detecting a dropout condition of the inductor.

12. The method of claim 5, further comprising the step of driving the discharge switch in the PWM mode for a number of pulses appropriate to maintain a level of energy in the energy storage device sufficient to cause the inductor to generate an operating magnetic field when a dropout condition of the inductor is detected based on the time interval between the operation of the second comparator and the operation of the first comparator, and further comprising the step of closing the discharge switch for a time sufficient to allow measurement of inductance without reducing the level of energy in the energy storage device below a level sufficient to cause the inductor to generate an operating magnetic field.

13. The method of claim 12 further comprising closing the discharge switch for 500 microseconds.

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