Patent Description:
<CIT> relates to a safety switching device for fail-safely disconnecting an electrical load which has an input part for receiving a safety-relevant input signal, a logic part for processing the at least one safety-relevant input signal, and an output part. The output part has a relay coil and four relay contacts. The first and second relay contacts are arranged electrically in series with one another. The third and fourth relay contacts are also arranged electrically in series with one another. The first and the third relay contacts are mechanically coupled to each other and form a first group of positively driven relay contacts. The second and the fourth relay contacts are mechanically coupled to each other and form a second group of positively driven relay contacts. The logic part redundantly controls the first and the second groups of positively driven relay contacts to selectively allow, or to interrupt in a fail-safe manner, a current flow to the electrical load, depending on the safety-relevant input signal. The relay coil is electromagnetically coupled to the first and second groups of positively driven relay contacts so that the logic part can control the relay contacts together via a single relay coil.

It is the object of the present invention to provide an improved fault tolerant safety relay.

A component for a dual pulse-width modulation ("PWM") relay driver with diagnostics is disclosed. An alternate component and a system also perform the functions of the component. The component includes a first switch connected to a power source of a safety relay and a second switch connected between the first switch and a first connection of a coil of normally open contacts of the safety relay. The component includes a first controller connected to control the first switch with a first output signal that is a close signal that closes the first switch or a first PWM signal with a first duty cycle that opens and closes the first switch on each PWM cycle. The component includes a second controller connected to control the second switch with a second output signal that includes a close signal that closes the second switch or a second PWM signal with a second duty cycle that opens and closes the second switch on each PWM cycle. The first duty cycle is different from the second duty cycle. The component includes a PWM sensing circuit connected to a second connection of the coil that sends a sensed PWM signal to an input of the first controller and an input of the second controller. The first controller sends the first PWM signal while the second controller sends a close signal and the second controller sends the second PWM signal while the first controller sends a close signal. The first controller verifies that the received PWM signal matches the first PWM signal while sending the first PWM signal and the second controller verifies that the received PWM signal matches the second PWM signal while sending the second PWM signal.

A system with a dual PWM relay driver with diagnostics includes an electrical component and a safety relay controlling power to the electrical component. The safety relay includes a first switch connected to a power source of a safety relay and a second switch connected between the first switch and a first connection of a coil of normally open contacts of the safety relay. The safety relay includes a first controller connected to control the first switch with a first output signal that is a close signal that closes the first switch or a first PWM signal with a first duty cycle that opens and closes the first switch on each PWM cycle. The safety relay includes a second controller connected to control the second switch with a second output signal that is a close signal that closes the second switch or a second PWM signal with a second duty cycle that opens and closes the second switch on each PWM cycle, the first duty cycle is different from the second duty cycle. The safety relay includes a PWM sensing circuit connected to a second connection of the coil that sends a sensed PWM signal to an input of the first controller and an input of the second controller. The first controller sends the first PWM signal while the second controller sends a close signal and the second controller sends the second PWM signal while the first controller sends a close signal. The first controller verifies that the received PWM signal matches the first PWM signal while sending the first PWM signal and the second controller verifies that the received PWM signal matches the second PWM signal while sending the second PWM signal.

In order that the advantages of the embodiments of the invention will be readily understood, a more particular description of the embodiments briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings.

The terms "including," "comprising," "having," and variations thereof mean "including but not limited to" unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive and/or mutually inclusive, unless expressly specified otherwise. The term "and/or" indicates embodiments of one or more of the listed elements, with "A and/or B" indicating embodiments of element A alone, element B alone, or elements A and B taken together.

Furthermore, the described features, advantages, and characteristics of the embodiments may be combined in any suitable manner. One skilled in the relevant art will recognize that the embodiments may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments.

These features and advantages of the embodiments will become more fully apparent from the following description and appended claims, or may be learned by the practice of embodiments as set forth hereinafter. As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method, and/or partly as a computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment or an embodiment combining hardware and software aspects (including firmware, resident software, micro-code, etc.) that may all generally be referred to herein as a "circuit," "module," "component" or "system. " Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having program code embodied thereon.

Some of the functional units described in this specification may be labeled as modules, circuits, components, etc., in order to more particularly emphasize their implementation independence. For example, a module, circuit or controller may be implemented as a hardware circuit comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module, component or circuit may also be implemented in programmable hardware devices such as field programmable gate arrays ("FPGAs"), programmable array logic, programmable logic devices or the like.

Modules, components or circuits may also be partially implemented in software for execution by various types of processors. An identified module, component or circuit of program code may, for instance, comprise one or more physical or logical blocks of computer instructions which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module, component or circuit need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module.

Program code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules, components, or circuits, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network. Where all or a part of a module, component or circuit are implemented in software, the program code may be stored and/or propagated on in one or more computer readable medium(s).

The computer readable medium may be a tangible computer readable storage medium storing the program code. The computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, holographic, micromechanical, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.

More specific examples of the computer readable storage medium may include but are not limited to a hard disk, a random access memory ("RAM"), a read-only memory ("ROM"), an erasable programmable read-only memory ("EPROM" or flash memory), a magnetic storage device, a micromechanical storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, and/or store program code for use by and/or in connection with an instruction execution system, apparatus, or device and, as used herein, a computer readable storage medium is not to be construed as a transitory signal.

The computer readable medium may also be a computer readable signal medium. A computer readable signal medium may include a propagated data signal with program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electrical, electro-magnetic, magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport program code for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable signal medium may be transmitted using any appropriate medium, including but not limited to wire-line, optical fiber, Radio Frequency ("RF"), or the like, or any suitable combination of the foregoing.

In one embodiment, the computer readable medium may comprise a combination of one or more computer readable storage mediums and one or more computer readable signal mediums. For example, program code may be both propagated as an electro-magnetic signal through a fiber optic cable for execution by a processor and stored on RAM storage device for execution by the processor.

In the following description, numerous specific details are provided, such as examples of programming, software modules, user selections, hardware modules, hardware components, hardware circuits, hardware chips, etc., to provide a thorough understanding of embodiments.

The program code may be stored in a computer readable medium that can direct a computer, microcontroller, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in schematic flowchart diagrams and/or schematic block diagrams block or blocks.

Aspects of the embodiments are described below with reference to schematic flowchart diagrams and/or schematic block diagrams of methods, apparatuses, systems, and computer program products according to embodiments of the invention. It will be understood that each block of the schematic flowchart diagrams and/or schematic block diagrams, and combinations of blocks in the schematic flowchart diagrams and/or schematic block diagrams, can be implemented by program code, circuits, components, etc. The program code may be provided to a processor of a controller, special purpose computer, sequencer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks.

The program code may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the schematic flowchart diagrams and/or schematic block diagrams block or blocks.

The program code may also be loaded onto a controller, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the controller, other programmable apparatus or other devices to produce a computer implemented process such that the program code which executed on the controller or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The schematic flowchart diagrams and/or schematic block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of apparatuses, systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the schematic flowchart diagrams and/or schematic block diagrams may represent a module, component, circuit, segment, or portion of code, which comprises one or more executable instructions of the program code for implementing the specified logical function(s).

It will also be noted that each block of the block diagrams and/or flowchart diagrams, and combinations of blocks in the block diagrams and/or flowchart diagrams, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and program code.

In some embodiments, the component includes a current sensor connected between the second connection of the coil and a ground of the safety relay, an analog test switch connected between the second connection of the coil and the inputs of the first controller and the second controller, and a PWM test switch connected between the PWM sensing circuit and the inputs of the first controller and the second controller. The PWM test switch and the analog test switch alternately close and the first and second controllers verify proper PWM operation while the PWM test switch is closed and verify proper current from the coil while the analog switch is closed. In other embodiments, the current sensor is a resistor. In other embodiments, the first controller opens the first switch and/or the second controller opens the second switch in response to detecting an abnormal current condition while the analog test switch is closed. In other embodiments, while the analog test switch is closed, the first and second controllers determine a current at the second connection of the coil to determine one or more of a coil failure, a first switch failure, and a second switch failure due to current not within an expected range during a particular operation of the first and second switches.

In some embodiments, the component includes a PWM alternating circuit that periodically switches between the first controller sending the first PWM signal while the second controller sends a close signal and the second controller sending the second PWM signal while the first controller sends a close signal. In other embodiments, the component includes a breaker close circuit that commands the first controller and the second controller to both send a close signal to close the first switch and the second switch for a startup period prior to operation where one of the first and the second controllers sends a PWM signal and the other of the first and the second controllers sends a close signal. In other embodiments, the PWM sensing circuit includes a comparator that inverts a PWM signal received from the second connection of the coil. The comparator sends the inverted PWM signal to the inputs of the first and second controllers and the first and second controllers determine if the received PWM matches the first or second PWM signals based on the inverted PWM signal.

In some embodiments, the first PWM signal and the second PWM signal reduce power consumption of the coil and each have a frequency and duty cycle adequate to prevent unwanted coil drop out that opens the contacts. In other embodiments, the first and second PWM switches are semiconductor switches and a switching frequency of the first PWM signal and the second PWM signal are selected to open and close the first switch during each switching cycle based on the first PWM signal and to open and close the second switch during each switching cycle based on the second PWM signal.

In some embodiments, the component includes a diode connected in parallel with the coil, where a cathode of the diode is connected to the first connection of the coil and an anode of the diode is connected to the second connection of the coil. In other embodiments, the first controller opens the first switch in response to determining that the received PWM signal does not match the first PWM signal while the first controller is sending the first PWM signal and the second controller opens the second switch in response to determining that the received PWM signal does not match the second PWM signal while the second controller is sending the second PWM signal.

An alternate component with a dual PWM relay driver with diagnostics includes a first switch connected to a power source of a safety relay, where the first switch is a semiconductor switch, and a second switch connected between the first switch and a first connection of a coil of normally open contacts of the safety relay, where the second switch is a semiconductor switch. The component includes a first microcontroller connected to control the first switch, where a first output signal of the first microcontroller is a close signal that closes the first switch or a first PWM signal with a first duty cycle that opens and closes the first switch on each PWM cycle. The component includes a second microcontroller connected to control the second switch, where a second output signal of the second microcontroller is a close signal that closes the second switch or a second PWM signal with a second duty cycle that opens and closes the second switch on each PWM cycle. The first duty cycle is different from the second duty cycle.

The component includes a comparator with an input connected to a second connection of the coil and an output connected to an input of the first microcontroller and an input of the second microcontroller. The comparator inverts the received PWM signal from the second connection of the coil. The first microcontroller sends the first PWM signal while the second microcontroller sends a close signal and the second microcontroller sends the second PWM signal while the first controller sends a close signal. The first microcontroller inverts the PWM signal from the comparator and verifies that a duty cycle of a resulting PWM signal matches a duty cycle of the first PWM signal while sending the first PWM signal and the second microcontroller inverts the PWM signal from the comparator and verifies that a duty cycle of a resulting PWM signal matches a duty cycle of the second PWM signal while sending the second PWM signal. The first microcontroller opens the first switch in response to determining that the duty cycle of the resulting PWM signal does not match the first duty cycle while the first microcontroller is sending the first PWM signal and the second microcontroller opens the second switch in response to determining that the duty cycle of the resulting PWM signal does not match the second duty cycle while the second microcontroller is sending the second PWM signal.

In some embodiments, the component includes a resistor connected between the second connection of the coil and a ground of the safety relay, an analog test switch connected between the second connection of the coil and the inputs of the first microcontroller and the second microcontroller. In the embodiment, the component includes a PWM test switch connected between the output of the comparator and the inputs of the first microcontroller and the second microcontroller. The PWM test switch and the analog test switch alternately close, where the first and second microcontrollers verify proper PWM operation while the PWM test switch is closed and verify proper current from the coil while the analog switch is closed. The first microcontroller opens the first switch and/or the second microcontroller opens the second switch in response to detecting an abnormal current condition while the analog test switch is closed.

In other embodiments, while the analog test switch is closed, the first and second microcontrollers determine a current at the second connection of the coil to determine one or more of a coil failure, a diode failure, a resistor failure, a first switch failure, and a second switch failure due to current not within an expected range during a particular operation of the first and second switches. In other embodiments, the component includes a PWM alternating circuit that periodically switches between the first microcontroller sending the first PWM signal while the second microcontroller sends a close signal and the second microcontroller sending the second PWM signal while the first microcontroller sends a close signal.

In some embodiments, the component includes a breaker close circuit that commands the first microcontroller and the second microcontroller to both send a close signal to close the first switch and the second switch for a startup period prior to operation where one of the first and the second microcontrollers sends a PWM signal and the other of the first and the second microcontrollers sends a close signal. In other embodiments, the first PWM signal and the second PWM signal reduce power consumption of the coil and each have a frequency and duty cycle adequate to prevent unwanted coil drop out to open the contacts.

A system with a dual PWM relay driver with diagnostics includes an electrical component and a safety relay controls power to the electrical component. The safety relay includes a first switch connected to a power source of a safety relay and a second switch connected between the first switch and a first connection of a coil of normally open contacts of the safety relay. The safety relay includes a first controller connected to control the first switch with a first output signal that is a close signal that closes the first switch or a first PWM signal with a first duty cycle that opens and closes the first switch on each PWM cycle. The safety relay includes a second controller connected to control the second switch with a second output signal that is a close signal that closes the second switch or a second PWM signal with a second duty cycle that opens and closes the second switch on each PWM cycle, the first duty cycle is different from the second duty cycle. The safety relay includes a PWM sensing circuit connected to a second connection of the coil that sends a sensed PWM signal to an input of the first controller and an input of the second controller. The first controller sends the first PWM signal while the second controller sends a close signal and the second controller sends the second PWM signal while the first controller sends a close signal. The first controller verifies that the received PWM signal matches the first PWM signal while sending the first PWM signal and the second controller verifies that the received PWM signal matches the second PWM signal while sending the second PWM signal.

In some embodiments, the system includes a current sensor connected between the second connection of the coil and a ground of the safety relay, an analog test switch connected between the second connection of the coil and the inputs of the first controller and the second controller, and a PWM test switch connected between the PWM sensing circuit and the inputs of the first controller and the second controller. The PWM test switch and the analog test switch alternately close and the first and second controllers verify proper PWM operation while the PWM test switch is closed and verify proper current from the coil while the analog switch is closed.

<FIG> is a schematic block diagram of system <NUM> with a dual PWM relay driver with diagnostics according to an embodiment. The system <NUM> includes a coil control component <NUM> connected to contacts <NUM>, and a circuit breaker <NUM> in a circuit breaker/safety relay <NUM> of an electrical component <NUM>, a motor controller/contactor <NUM>, starter logic <NUM>, a motor <NUM>, protected equipment <NUM>, sensors <NUM>, control power <NUM>, warning lights <NUM> and contactor power <NUM>, which are explained in more detail below.

For safe operation, often protected equipment <NUM> and areas around the protected equipment <NUM> include various sensors <NUM>, such as motion sensors, interlocks, light curtains, emergency stop switches, etc. which are used to stop a motor <NUM>, a valve, a pneumatic press, or other protected equipment <NUM> for safety of operators. Typically, a safety relay is used to open contacts <NUM>, which stop motors <NUM> and other protected equipment <NUM> to prevent injury to equipment operators. For example, protected equipment <NUM> such as a printing press, assembly line, etc. may include various light curtains, motion sensors, etc. that stop motors <NUM>, valves, etc. and when a barrier is crossed, an interlock is not actuated, or the like. When the various types of sensors <NUM> are actuated, when an interlock switch is not closed, etc., sensor wiring connected to a coil control component <NUM> transmit one or more signals to the coil control component <NUM>, which causes normally contacts <NUM> to open, which then causes the protected equipment <NUM> to stop.

Traditionally, safety relays are separate from circuit breakers <NUM>, motor controllers <NUM>, motor contactors <NUM>, thermal overload relays, etc. and may be grouped with control and safety equipment in an enclosure that may include one or more of circuit breakers <NUM>, fuses, motor overload relays, and the like.

In the embodiment depicted in <FIG>, a safety relay, which includes the coil control component <NUM> and contacts <NUM> is packaged with a circuit breaker <NUM> in a combination circuit breaker/safety relay <NUM>. In some embodiments, the circuit breaker/safety relay <NUM> is in a size D-frame, but may be included in other frame sizes. One particular problem with grouping a circuit breaker <NUM> with a safety relay in a combination circuit breaker/safety relay <NUM> is the heat that is generated by the circuit breaker <NUM> and safety relay components. For example, power to a coil controlling opening and closing of the contacts <NUM> may generate heat, which may be difficult to handle.

Other aspects of safety relays are redundancy and diagnostics. Depending on a level of required safety, some safety relays include a high degree of redundancy to increase fault tolerance. For example, a particular sensor <NUM> may include dual sensor wiring so that if either set of sensor wiring detects a condition of the sensor <NUM> where the contacts <NUM> should open, the coil control component <NUM> causes the contacts <NUM> to open. Redundancy, such as one out of two designs, within the coil control component <NUM> also provide a degree of fault tolerance and safety. Diagnostics help to ensure that the components of the coil control component <NUM> have not failed. Many current designs include only periodic testing, which is not as desirable as dynamic testing that occurs continuously during normal operation. The coil control component <NUM> beneficially reduces power within the circuit breaker/safety relay <NUM> and other safety relays while providing one-out-of-two redundancy and fault tolerance with dynamic testing, as will be explained in further detail with regard to the embodiments of <FIG>.

Typical circuit breakers <NUM> include contacts, which open and close mechanically and open under various overcurrent conditions. Typically, the circuit breaker <NUM> senses current flowing through the circuit breaker <NUM> trip logic that opens the contacts. For example, the trip logic may include an inverse time characteristic that opens slowly for low current just over a circuit breaker rating and quickly for high current. In some circuit breakers <NUM>, the inverse time characteristic allows for inrush current of a motor <NUM> and may include motor overload protection. Other circuit breakers <NUM> include adjustments to various parts of an inverse time characteristic to allow for circuit breaker coordination with upstream and downstream circuit breakers and components.

While the embodiment of <FIG> includes a circuit breaker/safety relay <NUM> that includes a circuit breaker <NUM> and safety relay components of a coil control component <NUM> and contacts <NUM>, the coil control component <NUM> and contacts <NUM> described herein may also be used for other safety relays to protect various protected equipment <NUM>. For example, the coil control component <NUM> and contacts <NUM> may be separated from the circuit breaker <NUM> or may be used in other applications with a fused disconnect, a motor controller within a motor control center ("MCC"), in an enclosure with other safety relays, etc. The coil control component <NUM> and contacts <NUM> of a safety relay may be used to stop and start other equipment than a motor <NUM>. One of skill in the art will recognize other ways to use the coil control component <NUM> and contacts <NUM> in a safety relay along with fuses, circuit breakers, contactors, thermal overload relays, etc. in various configurations and in various enclosures.

The coil control component <NUM>, as used herein, includes a typical coil for the contacts <NUM>, which is energized by a circuit that includes a power source, two switches in series, and a ground where when the switch is closed, current flows from the power source, through the closed switches, through the coil to ground in a sufficient amplitude to prevent unintentional dropout of the coil where the contacts <NUM> open inadvertently. Currently, various safety relays include a single switch which is placed between the coil and ground, which presents some disadvantages.

In many current safety relays, diagnostics are included to check for component failure in an open or short circuit condition. Some current diagnostic circuitry requires periodically entering a test mode to determine if a component has failed or there is some malfunction that would prevent proper operation of contacts. During periods between testing, these safety relays are vulnerable to undetected failures. Other safety relays use various configurations of switches, current sensing, diagnostic components, etc. for testing. Some safety relays currently may have certain circuit failures that cause the circuit breaker to not open properly or cause immediate opening for a single failure.

The embodiments of the coil control component <NUM> described herein improve on current safety relay technology by increasing fault tolerance and safety while reducing power consumption of the safety relay and/or circuit breaker/safety relay <NUM>. In addition, the coil control component <NUM> includes continuous diagnostic testing, which improves reliability and safety. The coil control component <NUM> is described in more detail with regard to <FIG> below.

The circuit breaker/safety relay <NUM>, in some embodiments, is a stand-alone circuit breaker/safety relay <NUM> that includes input and output terminals and may be mounted in an electrical component <NUM>. In other embodiments, the circuit breaker/safety relay <NUM> may be integrated within the electrical component <NUM> or other electrical device, such as the motor control center, variable frequency drive, etc. In other embodiments, the circuit breaker/safety relay <NUM> is mounted external to the electrical component <NUM>, but provides power to the electrical component <NUM>. In other embodiments, the circuit breaker/safety relay <NUM> is mounted in a panel, a motor control center, or other electrical distribution equipment. One of skill in the art will recognize other embodiments of the circuit breaker/safety relay <NUM> that includes contacts <NUM> and a coil control component <NUM>.

The electrical component <NUM> includes in the embodiment depicted in <FIG> a motor controller/contactor <NUM>. In other embodiments, the electrical component <NUM> includes other loads and may or may not include a motor controller/contactor <NUM>. In other embodiments, the electrical component <NUM> is the motor controller/contactor <NUM> and the circuit breaker/safety relay <NUM> may be located internal or external to the motor controller/contactor <NUM>. In another example, the coil control component <NUM> and contacts <NUM> may be part of an MCC that feeds the motor <NUM> where the MCC includes a contactor, but may also include a fuse, a motor overload, etc. The contacts <NUM> are connected to motor starter circuitry to cause the contactor controlling the motor <NUM> to open upon sensing a problem. The embodiments described herein may be implemented in variations that differ from an integrated circuit breaker/safety relay <NUM> that include contacts <NUM> and a coil control component <NUM> where overload and short circuit functions are included in other components, such as a fuse.

In the depicted embodiment, the system <NUM> includes a motor <NUM> controlled by a motor controller/contactor <NUM> by way of an example. In the embodiment, the motor controller/contactor <NUM> includes starter logic <NUM> and normally open contacts <NUM> in the circuit breaker/safety relay <NUM> are wired in series with the starter logic <NUM> so that the normally open contacts <NUM> must be closed for the starter logic <NUM> to energize the contactor in the motor controller/contactor <NUM>. The circuit breaker/safety relay <NUM>, in certain embodiments, is configured to handle inrush current from the motor <NUM>. Other embodiments include other loads in place of or in addition to the motor <NUM> and/or motor controller/contactor <NUM> that are fed by the circuit breaker/safety relay <NUM>. The circuit breaker/safety relay <NUM> may feed any type of electrical component <NUM>, such as computer equipment, heating and cooling equipment, kitchen appliances, outlets, lighting, an electrical distribution panel, etc. and the circuit breaker/safety relay <NUM> may be incorporated into any type of electrical component <NUM> that includes or feeds an electrical load.

In the system <NUM> of <FIG>, the circuit breaker/safety relay <NUM> is fed by separate control power <NUM>. For example, the control power <NUM> may be <NUM> volts direct current ("VDC") or other voltage and may be used to power sensors <NUM> and other safety equipment. In other embodiments, the control power <NUM> is derived from incoming power to the circuit breaker <NUM> and may be converted to a DC voltage with a converter within or external to the electrical component <NUM>. In some embodiments, the circuit breaker/safety relay <NUM>, electrical component <NUM>, etc. may include a converter that further converts the incoming control power <NUM> to one or more other voltages. In other embodiments, the control power <NUM> is <NUM> V alternating current ("AC") and may be derived from a transformer. One of skill in the art will recognize other ways to derive control power <NUM> for the coil control component <NUM>, for the circuit breaker/safety relay <NUM>, a safety relay, etc..

The system <NUM> includes warning lights <NUM>, which may be used to indicate a problem was detected by the sensors <NUM>. For example, the contacts <NUM> may include a one or more normally closed contacts, which are connected to the warning lights <NUM> so that when the normally open contacts of the contacts <NUM> are open, indicating a problem detected by a sensor <NUM> or other problem with wiring or within the coil control component <NUM>, the normally closed contacts of the contacts <NUM> provide power to the warning lights <NUM>. In other embodiments, the normally closed contacts are wired to other equipment, such as to signaling equipment that sends an alert. One of skill in the art will recognize other ways to use normally closed contacts within the contacts <NUM>.

In some embodiments, the system <NUM> includes contactor power <NUM> that feeds a coil of the motor controller/contactor <NUM>. For example, the contactor power <NUM> may be different from the control power <NUM>. In some embodiments, the contactor power <NUM> is <NUM> VAC. In some embodiments, the circuit breaker/safety relay <NUM> or a safety relay with the coil control component <NUM> and contacts <NUM> may be within an MCC and the contactor power <NUM> comes from the MCC. In other embodiments, the contactor power <NUM> is derived within the electrical component <NUM>. For example, the electrical component <NUM> may include a transformer connected to utility power, incoming power, etc. In other embodiments, the contactor power <NUM> is the same as the control power <NUM>. One of skill in the art will recognize other ways to provide power to the coil of the motor controller/contactor <NUM>.

Note that the circuit breaker <NUM>, motor controller/contactor <NUM> and motor <NUM> are depicted in <FIG> as being fed by three-phase power (phases A, B and C). In other embodiments, the circuit breaker <NUM>, motor controller/contactor <NUM> and motor <NUM> are fed by single-phase power that is either line-to-line with two poles in a contactor/circuit breaker or line-to-ground with a single pole in the contactor/circuit breaker.

In some embodiments, the motor controller/contactor <NUM> is a motor starter where a contactor closes to provide full voltage instantly to the motor <NUM>. In other embodiments, the motor controller/contactor <NUM> is a reduced voltage motor starter. In other embodiments, the motor controller/contactor <NUM> is a variable frequency drive ("VFD"). One of skill in the art will recognize other types of motor starters that may be incorporated into the motor controller/contactor <NUM>.

<FIG> is a schematic block diagram of an embodiment <NUM> of a coil control component <NUM> with a dual PWM relay driver with diagnostics. The embodiment <NUM> includes one embodiment of the coil control component <NUM> with a first switch <NUM>, a second switch <NUM>, a first controller <NUM>, a second controller <NUM>, a coil <NUM>, a pulse-width modulation ("PWM") sensing circuit <NUM> and a load power source <NUM>, contacts <NUM>, a load <NUM>, relay power <NUM> and sensor/load <NUM>, which are described below.

The coil control component <NUM> and contacts <NUM> may be implemented in a safety relay, a circuit breaker/safety relay <NUM> or other safety equipment. The load <NUM> may be a motor <NUM> and/or associated contactor, starter, etc. or may be other protected equipment <NUM> and the load power <NUM> may be from a distribution panel, from an MCC, may be fed through a circuit breaker <NUM>, a fuse, etc. Typically, the contacts <NUM> are auxiliary contacts that are part of starter logic <NUM> or are part of circuitry of other switches, interlocks, etc. and are used to stop protected equipment <NUM>. Where the load <NUM> is a motor <NUM> as part of the protected equipment <NUM>, the coil control component <NUM> and contacts <NUM> may be implemented as indicated in the system <NUM> of <FIG> or may be implemented as a safety relay <NUM> used in conjunction with separate overcurrent protection, starter logic <NUM>, a motor controller/contactor <NUM>, a variable frequency drive, etc. controlling the motor <NUM>. Where the load <NUM> represents other protected equipment <NUM>, the protected equipment <NUM> is protected by a safety relay with the coil control component <NUM> and contacts <NUM> or with the combination circuit breaker/safety relay <NUM> where main power to the protected equipment <NUM> runs through the circuit breaker and the contacts <NUM> are wired in series with other start/stop buttons, interlocks, etc. so that the sensors <NUM> control opening of the contacts <NUM>, which then stop/disable the protected equipment <NUM>.

The first switch <NUM> is connected to a power source, which is marked as relay power <NUM>. The relay power <NUM>, is derived from incoming power to the circuit breaker/safety relay <NUM> and may have a reduced magnitude with respect to a voltage of the incoming power. For example, the relay power <NUM> may be <NUM> VDC while incoming power to the circuit breaker <NUM> may be <NUM> V, <NUM> V, <NUM> V, <NUM> V, etc., depending on line-to-line or line-to-neutral connections and type of motor <NUM> or other load. The second switch <NUM> is connected to the first switch <NUM> in series and to a first connection of a coil <NUM> of normally open contacts <NUM>. The circuit breaker/safety relay <NUM> or safety relay may also include another coil <NUM> and first and second switches <NUM>, <NUM> connected to normally closed contacts. Note that the description of <FIG> included both normally open and normally closed contacts as part of the depicted contacts <NUM>. In other embodiments described herein, the normally open contacts and normally closed contacts of the contacts <NUM> may be referred to as contacts <NUM>. Typically, the contacts <NUM> includes at least normally open contacts so that any loss of power to the coil <NUM> results in opening of the contacts <NUM> for safety.

In some embodiments, the first switch <NUM> and the second switch <NUM> are semiconductor switches capable of opening and closing at a particular frequency. In other embodiments, the first switch <NUM> and the second switch <NUM> are mechanical switches capable of opening and closing at a frequency such that the coil <NUM> does not drop out unintentionally.

The first controller <NUM> is connected to control the first switch <NUM> with a first output signal that may be a close signal that closes the first switch <NUM> or a first PWM signal with a first duty cycle that opens and closes the first switch <NUM> on each PWM cycle. The first controller <NUM> also opens the first switch <NUM> to open the contacts <NUM> with an open signal that causes the first switch <NUM> to remain open.

The second controller <NUM> is connected to control the second switch <NUM> with a second output signal that may be a close signal that closes the second switch <NUM> or a second PWM signal with a second duty cycle that opens and closes the second switch <NUM> on each PWM cycle. The second controller <NUM> also opens the second switch <NUM> to open the contacts <NUM> with an open signal that causes the second switch <NUM> to remain open. The first duty cycle is different from the second duty cycle so that the first PWM signal is different than the second PWM signal, which is explained in more detail below.

In some embodiments, the first and second controller <NUM>, <NUM> are microcontrollers and may include a processor and program code or may be implemented in a different way. The first and second controllers <NUM>, <NUM>, in other embodiments, are hardware controllers. For example, the first and second controllers <NUM>, <NUM> may be application specific integrated circuits ("ASICs"), may be programmable hardware devices, such as FPGAs, programmable array logic, etc. For safety, the first controller <NUM> is physically a separate device than the second controller <NUM>. Typically, the first and second controllers <NUM>, <NUM> communicate so that if the first controller <NUM> sends an open signal to the first switch <NUM>, the second controller <NUM> also opens the second switch <NUM>, and vice-versa.

In some embodiments, the first and second controllers <NUM>, <NUM> receive input from a user to change parameters, such as changing pulse-width modulation ("PWM") duty cycle, a time delay, etc. Typically, the first and second controllers <NUM>, <NUM> are separate from overcurrent protection circuitry, but may receive a command from some over current or thermal protection circuitry to open the first and second switches <NUM>, <NUM>. One of skill in the art will recognize other ways to implement the first and second controllers <NUM>, <NUM>.

The PWM sensing circuit <NUM> is connected to a second connection of the coil <NUM> that sends a sensed PWM signal to an input of the first controller <NUM> and an input of the second controller <NUM>. A sensor/load <NUM> is also connected to the second connection of the coil <NUM> and is explained in more detail below with regard to the embodiments, <NUM>-<NUM> of <FIG>. In one embodiment, the PWM sensing circuit <NUM> includes an inverter, comparator or other circuit that inverts the sensed PWM signal from the second connection of the coil <NUM> before sending this inverted PWM signal to the first and second controllers <NUM>, <NUM>. In other embodiments, the PWM sensing circuit <NUM> sends the sensed PWM circuit directly to the first and second controllers <NUM>, <NUM>.

In the embodiment <NUM>, the first controller sends the first PWM signal while the second controller sends a close signal and the second controller sends the second PWM signal while the first controller sends a close signal. The first controller <NUM> verifies that the received PWM signal matches the first PWM signal while sending the first PWM signal and the second controller <NUM> verifies that the received PWM signal matches the second PWM signal while sending the second PWM signal.

As stated above the first PWM signal is different than the second PWM signal. For example, the first duty cycle may be <NUM>% while the second duty cycle may be <NUM>%. While the first controller <NUM> is transmitting the first PWM signal, the second controller <NUM> is transmitting a close signal that closes the second switch <NUM>. When working correctly, the first PWM signal from the first controller <NUM> causes the first switch <NUM> to open and close at the PWM frequency and first duty cycle so that the coil <NUM> sees a PWM signal similar to the first PWM signal. The second connection of the coil <NUM> also sees the PWM signal, which is sensed by the PWM sensing circuit <NUM>.

In some embodiments, the PWM sensing circuit <NUM> inverts the sensed PWM signal before transmission to the first and second controllers <NUM>, <NUM>. The first controller <NUM> is transmitting the first PWM signal from an output so that first controller <NUM> responds by determining that the signal received from the PWM sensing circuit <NUM> has a duty cycle that matches the first PWM signal. For example, if the first duty cycle is <NUM>%, the duty cycle of the signal from the PWM sensing circuit <NUM> will be <NUM>% so the first controller <NUM> is able to recognize that a sensed duty cycle of <NUM>% equates to an inverted, sensed PWM signal with a <NUM>% duty cycle.

In some embodiments, the first controller <NUM> receives the signal from the PWM sensing circuit <NUM> through an analog-to-digital converter ("ADC") and digitally inverts the received signal. For example, if the received signal has a duty cycle of <NUM>%, the first controller <NUM> inverts this received signal so that a resulting signal has a duty cycle of <NUM>%, which is then compared to the first PWM signal. If the inverted signal from the PWM sensing circuit <NUM> has a duty cycle that matches the first duty cycle within some tolerance, the first controller <NUM> determines that the transmitted first PWM signal matches the received PWM signal so the first controller <NUM> continues to transmit the first PWM signal.

A benefit of a PWM sensing circuit <NUM> that inverts the sensed PWM signal is that the first and second controllers <NUM>, <NUM> are able to determine if a short exists between the input where the sensed PWM signal is received and the output where the PWM signal is transmitted. For example, if the first controller <NUM> is transmitting the first PWM signal from an output with a duty cycle of <NUM>%, the input of the first controller <NUM> where the sensed PWM signal is received from the PWM sensing circuit <NUM> should have a duty cycle of <NUM>% and the signals are mirrored so when the first PWM signal is high, the sensed PWM signal is low. If the first controller <NUM> determines that the input is not inverted from the output, the first controller <NUM> is able to conclude that there is a short between the input and the output and the first controller <NUM> takes appropriate action, such as opening the contacts <NUM>, sending a notification, informing the second controller <NUM>, etc..

If the first controller <NUM> determines that the received signal from the PWM sensing circuit <NUM> has a duty cycle inconsistent with the first duty cycle, the first controller <NUM> takes appropriate action, such as sending a notification, opening the first switch <NUM>, etc. Typically, when the first controller <NUM> determines that the received signal from the PWM sensing circuit <NUM> has duty cycle inconsistent with the first duty cycle, the first controller <NUM> notifies the second controller <NUM> opens the second switch <NUM>. In other embodiments, the first and/or second controller <NUM>, <NUM> sends notification of a problem, for example to a system administrator.

In addition, a fault tolerant coil control component <NUM> is able to compensate for a switch that has failed short. For example, if the first controller <NUM> determines that that the sensed PWM signal is a constant voltage while the first controller <NUM> is sending the first PWM signal, the first controller <NUM> can attempt to open the first switch <NUM>, but the first switch <NUM> may be failed short. The first controller <NUM> may then notify the second controller <NUM> of the abnormal condition and the second controller <NUM> opens the second switch <NUM>. Typically, the first and second controllers <NUM>, <NUM> are failed short.

Typically, the first controller <NUM> sends a notification to the second controller <NUM> and logic within the first controller <NUM> and/or second controller <NUM> or other circuitry within the circuit breaker/safety relay <NUM> uses fault analysis to determine an appropriate action. For example, the first and second controllers <NUM>, <NUM> may operate in tandem to determine that a single fault has occurred and that an appropriate action is to send a notification to a system administrator or to determine that a second fault has occurred which causes the first switch <NUM> and/or second switch <NUM> to open immediately.

In some embodiments, the coil control component <NUM> of <FIG> is fault tolerant, so the first controller <NUM> sends a notification of a problem when the received duty cycle is inconsistent with the first duty cycle without opening the first switch <NUM>. For example, an operator receiving the notification may then take steps to reroute power so power to protected equipment <NUM> comes from another source, to replace the circuit breaker/safety relay <NUM>, to shut off the circuit breaker/safety relay <NUM> at a convenient time, etc..

When the first controller <NUM> is transmitting a close command to the first switch <NUM>, the second controller <NUM> transmits from an output port the second PWM signal with the second duty cycle to the second switch <NUM>. As with the first controller <NUM> and first switch <NUM>, the second switch <NUM> opens and closes at the frequency and duty cycle of the second PWM signal. The PWM sensing circuit <NUM> senses the second PWM signal at the second connection of the coil <NUM> and transmits an inverted signal, or in another embodiment a non-inverted signal, to the first and second controllers <NUM>, <NUM>. During this condition, the first controller <NUM> stops analyzing the received PWM signal from the PWM sensing circuit <NUM> and the second controller <NUM> starts to analyze the received signal.

In one example, the second PWM signal has a second duty cycle of <NUM>% or some other duty cycle different than is transmitted by the first controller <NUM>. Where the PWM sensing circuit <NUM> inverts the sensed PWM signal from the coil <NUM>, the resulting PWM signal sent to the first and second controller <NUM> has a duty cycle of <NUM>%. The second controller <NUM> may invert this received signal and then determine a duty cycle or may infer from the received PWM signal with a <NUM>% duty cycle that the received duty cycle is consistent or inconsistent with the second duty cycle of the transmitted second PWM signal.

The statements regarding the first controller <NUM> above are equally applicable to the second controller <NUM>. Typically, the first and second controllers <NUM>, <NUM> are identical but transmit PWM signals with different duty cycles so that each controller <NUM>, <NUM> is able to discern that a transmitted PWM signal is the same as a received PWM signal. In one embodiment, the first and second controllers <NUM>, <NUM> transmit a PWM signal with a same duty cycle.

Note that the first and second controllers <NUM>, <NUM> compare transmitted and received PWM signals and, in some embodiments, include a tolerance on a difference between the transmitted and received PWM signals. In some embodiments, a difference between the first duty cycle and the second duty cycle is set to allow a reasonable measurement tolerance. For example, where the difference between duty cycles is <NUM>%, a tolerance may be +/- <NUM>% for each controller <NUM>, <NUM>. In other embodiments, the tolerance is in a range of +/- <NUM>% to <NUM>%. One of skill in the art will recognize an appropriate tolerance based on accuracy of the PWM sensing circuit <NUM>, component tolerances, etc..

In some embodiments, the first PWM signal and the second PWM signal operate at a fixed frequency where for each cycle, the PWM signals include an "on" portion and an "off" portion. For example, where the first PWM signal has a <NUM>% duty cycle, the signal is high for the first <NUM>% of the cycle and low for the last <NUM>% of the cycle. A high signal is a signal that commands the first or second switch <NUM>, <NUM> to a closed state and the low signal commands the first or second switch <NUM>, <NUM> to an open state. A duty cycle is a period when the PWM signal is high. The "on" period may also be called a pulse width.

In some embodiments, the frequency of the PWM signals is a same frequency for the first and second controllers <NUM>, <NUM>. In other embodiments, the PWM frequency is different for the first and second controllers <NUM>, <NUM>. Where the PWM frequency is fixed, the PWM signals from the first and second controllers <NUM>, <NUM> may or may not be synchronized. The frequency for the PWM signals is chosen for a variety of factors. For example, the PWM frequency and duty cycles for the first and second PWM signals are chosen to result in the coil <NUM> remaining in a condition to maintain the contacts <NUM> closed.

In other embodiments, the PWM frequency is chosen to be low enough for the first and second switches <NUM>, <NUM> to be able to open and close during each cycle. In other embodiments, the PWM frequency is chosen to be above the audible frequency range, to minimize switching losses, etc. In some embodiments, the PWM switching frequency is <NUM> kilo Hertz ("kHz"). In other embodiments, the PWM switching frequency is within a range of about <NUM> to <NUM>. In other embodiments, the PWM switching frequency is within a range of about <NUM> to <NUM>. As an example, where the PWM frequency is <NUM>, a switching cycle is <NUM> microseconds so where the duty cycle is <NUM>%, the pulse width is <NUM> microseconds and where the duty cycle is <NUM>%, the pulse width is <NUM> microseconds. The pulse width is selected to be high enough so that during each PWM cycle enough energy is transferred to the coil <NUM> to maintain the coil in a closed state during the "off" period of the PWM cycle. One of skill in the art will recognize factors useful in choosing the PWM frequency and tradeoffs between various possible PWM frequencies.

In addition, where the duty cycle is <NUM>%, an average voltage to the coil <NUM> is about <NUM>% of the relay power voltage <NUM>, which represents a power savings for the circuit breaker/safety relay <NUM>. Power savings for the circuit breaker/safety relay <NUM> is a benefit of the embodiments of the coil control component <NUM> described herein. A minimum duty cycle is chosen that will reduce power consumption of the circuit breaker/safety relay <NUM> while safely maintaining the contacts <NUM> closed while the first or second PWM signals are being transmitted from the first and second controllers <NUM>, <NUM> and while maintaining an adequate safety margin between an absolute minimum average voltage across the coil <NUM> and a chosen minimum duty cycle.

In one embodiment, the first controller <NUM> and second controller <NUM> alternate between sending PWM signals at an alternating switch rate. The alternating switch rate is lower than the PWM frequency. In some embodiments, the alternating switch rate is much lower than the PWM frequency. For example, the alternating switch rate may be such that the first and second controllers <NUM>, <NUM> alternate sending the PWM signals every second, every half second, etc. In other embodiments, the alternating switch rate is faster such as a frequency of <NUM>.

In some embodiments, the first and second controllers <NUM>, <NUM> immediately switch from the first controller <NUM> sending the first PWM signal while the second controller <NUM> sends a close signal to the second controller <NUM> sending the second PWM signal while the first controller <NUM> sends a close signal. In other embodiments, there is a delay between the first and second controllers <NUM>, <NUM> sending the PWM signals. For example, both controllers <NUM>, <NUM> may both transmit a close signal to the first and second switches <NUM>, <NUM> during a brief transition time from one controller (e.g. <NUM>) transmitting a PWM signal to the other controller (e.g. <NUM>) transmitting a PWM signal. The brief transition time may be chosen to allow switching and transients to clear before commencement of transmission of another PWM signal.

Note that the coil control component <NUM> may include other components not shown in <FIG>, such as another controller, reset circuitry, remote control circuitry, mechanical components of the circuit breaker <NUM>, a thermal overload and the like. The sensor/load <NUM>, in some embodiments, is chosen to maintain current through the coil <NUM> below a maximum level while maintaining enough current through the coil <NUM> to prevent unwanted dropout of the contacts <NUM>. Typically, the contacts <NUM> are connected to a load power source <NUM> and a load <NUM>. The load <NUM> is what is being protected by the circuit breaker/safety relay <NUM> and the load power <NUM> is typically an input power source connected to the input side of terminals of the circuit breaker/safety relay <NUM>.

<FIG> is a schematic block diagram of an embodiment <NUM> with a version of a coil control component <NUM> with a dual PWM relay driver with analog diagnostics. The embodiment <NUM> includes another embodiment of a coil control component <NUM> that includes a first switch <NUM>, a second switch <NUM>, a first controller <NUM>, a second controller <NUM>, a coil <NUM>, a PWM sensing circuit <NUM>, a load <NUM>, contacts <NUM>, load power <NUM>, and relay power <NUM>, which are substantially similar to those described above in relation to the embodiment <NUM> of <FIG>. The coil control component <NUM> also includes a current sensor <NUM> and a diode <NUM>, which are described below.

The coil control component <NUM>, in some embodiments, includes a current sensor <NUM> connected between the second connection of the coil <NUM> and a ground of the circuit breaker/safety relay <NUM> or safety relay. In some embodiments, the current sensor <NUM> is a resistor that acts as a load for the coil <NUM> and is chosen to have a current of the coil <NUM> to be within limits. In other embodiments, the current sensor <NUM> is separate from a load of the coil <NUM>. In some embodiments, the current sensor <NUM> is a current transformer, a hall effect sensor, etc. Where the current sensor <NUM> is different than a resistor, the current sensor <NUM> may be connected differently than depicted in <FIG>. One of skill in the art will recognize other appropriate current sensors <NUM>.

The coil control component <NUM>, in some embodiments, includes a diode <NUM> across the coil <NUM>. The diode <NUM> is connected across the coil <NUM> as depicted and, in some embodiments, the diode <NUM> is a free-wheeling diode and provides protection for the coil <NUM>, such as allowing current flow through inductance of the coil <NUM> while one or both of the first and second switches <NUM>, <NUM> are open. In other embodiments, one or more snubbers, transient voltage surge suppression, etc. are included.

In the embodiment, <NUM>, the first and/or second controllers <NUM>, <NUM> verify proper current through the coil <NUM>. For example, current sensing through the current sensor <NUM> may detect a short in the coil <NUM>, the diode <NUM>, the load of the coil <NUM>, the first switch <NUM>, the second switch <NUM>, etc. For example, where one or more of the coil <NUM>, the diode <NUM>, the first switch <NUM>, the second switch <NUM>, etc. are shorted, the current sensor <NUM> may detect a higher current than expected. Where voltage at the second connection to the coil <NUM> is zero or very low, this may indicate a short in or across the current sensor <NUM> and/or a load of the coil <NUM>. In other embodiments, the current sensor <NUM> may be used to detect an open condition, such as when the coil <NUM> fails open, when a switch <NUM>, <NUM> fails open, etc..

<FIG> is a schematic block diagram of another embodiment <NUM> of another version of the coil control component <NUM> with a dual PWM relay driver with digital and analog diagnostics. The embodiment <NUM> includes another version of the coil control component <NUM> that includes a first switch <NUM>, a second switch <NUM>, a first controller <NUM>, a second controller <NUM>, a coil <NUM>, a PWM sensing circuit <NUM>, a load <NUM>, contacts <NUM>, load power <NUM>, relay power <NUM>, current sensor <NUM> and diode <NUM>, which are substantially similar to those described above in relation to the embodiments <NUM>, <NUM> of <FIG> and <FIG>. The coil control component <NUM> also includes an analog test switch <NUM>, a PWM test switch <NUM>, a PWM alternating circuit <NUM> and a breaker close circuit <NUM>, which are described below.

The coil control component <NUM>, in some embodiments, includes an analog test switch <NUM> connected between the second connection of the coil <NUM> and the inputs of the first controller <NUM> and the second controller <NUM> and a PWM test switch <NUM> connected between the PWM sensing circuit <NUM> and the inputs of the first controller <NUM> and the second controller <NUM>. The PWM test switch <NUM> and the analog test switch <NUM> alternately close so that only one is closed at a time. For example, while the PWM sensing circuit <NUM> is sensing a PWM signal from the second connection of the coil <NUM>, the PWM test switch is closed while the analog test switch <NUM> is opened to allow the PWM sensing circuit <NUM> to operate and detect PWM signals which allows the first or second controller <NUM>, <NUM> to verify proper PWM operation as described above with respect to the embodiment <NUM> of <FIG>.

Where the analog test switch <NUM> is closed, the PWM test switch <NUM> is open to allow the first and/or second controllers <NUM>, <NUM> to verify proper current through the coil <NUM> as described above with regard to the embodiment <NUM> of <FIG>. For example, when the analog test switch <NUM> is closed, current sensing through the current sensor <NUM> may detect a short in the coil <NUM>, the diode <NUM>, the load of the coil <NUM>, the first switch <NUM>, the second switch <NUM>, etc. and where one or more of the coil <NUM>, the diode <NUM>, the first switch <NUM>, the second switch <NUM>, etc. are shorted, the current sensor <NUM> may detect a higher current than expected. Where voltage at the second connection to the coil <NUM> is zero or very low, this may indicate a short in or across the load of the coil <NUM>. In other embodiments, the current sensor <NUM> may be used to detect an open condition, such as when the coil <NUM> fails open, when a switch <NUM>, <NUM> fails open, etc..

The analog test switch <NUM> and PWM test switch <NUM> are depicted to be controlled by the first and second controllers <NUM>, <NUM>. In some embodiments, the first and second controllers <NUM>, <NUM> are connected to and control the analog test switch <NUM> and the PWM test switch <NUM>. In some embodiments, the first controller <NUM> operates the analog test switch <NUM> and the PWM test switch <NUM> while transmitting the first PWM signal and the second controller <NUM> operates the analog test switch <NUM> and the PWM test switch <NUM> while transmitting the second PWM signal. In other embodiments, the first and second controllers <NUM>, <NUM> cooperate to operate the analog test switch <NUM> and the PWM test switch <NUM>. In other embodiments, another device controls the analog test switch <NUM> and the PWM test switch <NUM>.

In some embodiments, a test switching rate of switching between PWM sensing mode through the PWM test switch <NUM> to current sensing mode through the PWM test switch <NUM> is set to a rate that considers safety as well as operating constraints for the PWM sensing mode and the current sensing mode. For example, the test switching rate may allow a few PWM cycles in the PWM sensing mode before switching to the current sensing mode. In some embodiments, a length of time of the PWM sensing mode is the same as the current sensing mode. In other embodiments, a length of time of the PWM sensing mode is different than a length of time of the current sensing mode. For example, the current sensing mode to check for abnormal current in the coil <NUM> may be brief with respect to PWM sensing operations. In the example, the PWM sensing mode may take <NUM>% of a test switching rate cycle while the current sensing mode may take <NUM>% of the test switching rate cycle. A frequency of switching between the PWM sensing mode to the current sensing mode is different, in some embodiments, than alternating between controllers <NUM>, <NUM> changing which sends the PWM signals.

In some embodiments, the frequency of switching between the PWM sensing mode to the current sensing mode is faster than alternating between controllers <NUM>, <NUM> changing which sends that PWM signals. For example, where the PWM frequency is <NUM>, the frequency of switching between the PWM sensing mode and the current sensing mode may be around <NUM> while the alternating switch rate is around <NUM>.

In some embodiments, the coil control component <NUM> incudes a PWM alternating circuit <NUM> that periodically switches between the first controller <NUM> sending the first PWM signal while the second controller <NUM> sends a close signal and the second controller <NUM> sending the second PWM signal while the first controller sends a close signal at an alternating switch rate. The PWM alternating circuit <NUM>, in some embodiments, functions to alternate which of the first and second controllers <NUM>, <NUM> is transmitting a PWM signal as described above as described in the embodiment <NUM> of <FIG>. In other embodiments, the PWM alternating circuit <NUM> and/or functionality of the PWM alternating circuit <NUM> is incorporated in one or both of the first and second controllers <NUM>, <NUM>.

In some embodiments, the coil control component <NUM> includes a breaker close circuit <NUM> that commands the first controller <NUM> and the second controller <NUM> to both send a close signal to close the first switch <NUM> and the second switch <NUM> for a startup period prior to operation where one of the first and the second controllers <NUM>, <NUM> sends a PWM signal and the other of the first and the second controllers <NUM>, <NUM> sends a close signal. When initially closing the contacts <NUM>, in some embodiments it is desirable to close the contacts <NUM> as fast as possible. Having the first switch <NUM> and the second switch <NUM> closed maximizes voltage across the coil <NUM>, which drives the contacts <NUM> closed faster than where one of the first and second controllers <NUM>, <NUM> is sending a PWM signal and voltage across the coil <NUM> is reduced.

The breaker close circuit <NUM> maintains both the first and second controllers <NUM>, <NUM> sending the close signal for a startup period. The startup period, in some embodiments, is a time adequate for the contacts <NUM> to close. In some embodiments, the startup period is in the millisecond range. In other embodiments, the startup period is longer than a minimum closure time for the contacts <NUM>. In the embodiment <NUM> depicted in <FIG>, the breaker close circuit <NUM> is separate from the first and second controllers <NUM>, <NUM>. In other embodiments, the breaker close circuit <NUM> and/or functionality of the breaker close circuit <NUM> is incorporated in one or both of the first and second controllers <NUM>, <NUM>.

<FIG> is a schematic block diagram of another embodiment <NUM> with a more detailed version of a coil control component <NUM> with a dual PWM relay driver with digital and analog diagnostics. The embodiment <NUM> includes one embodiment of the coil control component <NUM> that includes a first switch <NUM>, a second switch <NUM>, a coil <NUM>, a load <NUM>, contacts <NUM>, load power <NUM>, relay power <NUM>, an analog test switch <NUM>, a PWM test switch <NUM>, which are substantially similar to those described above in relation to the embodiments <NUM>, <NUM>, <NUM> of <FIG>, <FIG> and <FIG>. In the embodiment <NUM>, the coil control component <NUM> includes a resistor <NUM>, a comparator <NUM>, a first microcontroller <NUM> and a second microcontroller <NUM>, which are described below.

In some embodiments, the current sensor <NUM> is a resistor <NUM> and the resistor <NUM> serves for both current sensing and as a load for the coil <NUM>, as described above. The resistor <NUM> is sized to maintain current through the coil <NUM> below a maximum level and above a level to maintain the coil <NUM> closed when one of the first and second microcontrollers <NUM>, <NUM> is transmitting a PWM signal.

In some embodiments, the coil control component <NUM> includes a comparator <NUM> that serves as a PWM sensing circuit <NUM>. The comparator <NUM> includes a reference voltage connected to a positive input and the second connection to the coil <NUM> connected to a negative input of the comparator <NUM> as depicted, which serves to invert the sensed PWM signal from the second connection to the coil <NUM>. The reference is set to a level between a voltage of the relay power source <NUM> and ground, and more particularly to a level between an upper level and a lower level of the sensed PWM signal so that when the sensed PWM signal is high, the output of the comparator <NUM> is low and when the sensed PWM signal is low, the output of the comparator <NUM> is high.

The first and second microcontrollers <NUM>, <NUM> function substantially similar to the first and second controllers <NUM>, <NUM> of the embodiments <NUM>, <NUM>, <NUM> of <FIG>, <FIG> and <FIG>. The first and second microcontrollers <NUM>, <NUM> are one possible embodiment and may include one or more processors, memory, logic for overcurrent protection, short circuit protection, diagnostics, etc. separate from the circuit breaker <NUM> and within the circuit breaker/safety relay <NUM> or within a safety relay. One of skill in the art will recognize advantages of using microcontrollers in the coil control component <NUM>.

<FIG> is a schematic block diagram of one embodiment <NUM> of a more detailed version of part of a coil control component <NUM> with a dual PWM relay driver with diagnostics with digital diagnostics. The embodiment <NUM> includes a first switch <NUM> and a second switch <NUM> as semiconductor switches along with driver circuitry. The embodiment <NUM> also depicts the comparator <NUM> with additional resistors, a supply voltage, etc. The circuitry depicted merely describe a single embodiment and one of skill in the art will recognize other embodiments for implementing the embodiments <NUM>, <NUM>, <NUM>, <NUM> of <FIG>, <FIG>, <FIG> and <FIG>.

<FIG> is a schematic flow chart diagram depicting one embodiment of a method <NUM> for operation of a dual PWM relay driver with diagnostics. The method <NUM> operates <NUM> the first switch <NUM> with a first PWM signal which opens and closes the first switch <NUM> according the to the PWM signal with a first duty cycle. The method <NUM> simultaneously closes the second switch <NUM> and maintains the second switch <NUM> closed. The method <NUM> senses <NUM> a PWM signal at the second terminal of the coil <NUM> and determines <NUM> if the first PWM signal matches a sensed PWM signal. If the method <NUM> determines <NUM> that the first PWM signal matches the sensed PWM signal, the method <NUM> returns and continues to operate the first switch <NUM> with the first PWM signal and operates <NUM> the second switch <NUM> closed. If the method <NUM> determines <NUM> that the first PWM signal does not match the sensed PWM signal, the method <NUM> opens <NUM> the contacts <NUM> of the circuit breaker/safety relay <NUM>, and the method <NUM> ends. After a period of time, the method <NUM>, in some embodiments, alternates so the first switch <NUM> is closed and the second switch <NUM> operates with the second PWM signal. The method <NUM>, in various embodiments, is implemented with the first switch <NUM>, the second switch <NUM>, the first controller <NUM>, the second controller <NUM>, the coil <NUM>, and the PWM sensing circuit <NUM> or other components described herein.

<FIG> is a schematic flow chart diagram depicting one embodiment of a method <NUM> for operation of a dual PWM relay driver with digital or analog diagnostics and alternating PWM signals. The method <NUM> begins and operates <NUM> the first switch <NUM> and the second switch <NUM> to close. For example, the method <NUM> may operate <NUM> both the first and second switches <NUM>, <NUM> to close during an initial startup period to drive the contacts <NUM> closed quickly, to verify that the coil <NUM> will close the contacts <NUM>, to verify that the first and the second switches <NUM>, <NUM> are capable of closing, etc..

The method <NUM> operates <NUM> the first switch <NUM> with a first PWM signal and senses <NUM> a PWM signal at the second connection to the coil <NUM>. The method <NUM>, from the sensed PWM signal, determines <NUM> if the first PWM signal matches the sensed PWM signal. If the method <NUM> determines <NUM> that the first PWM signal does not match the sensed PWM signal, the method <NUM> opens <NUM> the contacts <NUM>, and the method <NUM> ends. Opening <NUM> the contacts <NUM> then has an effect on the load <NUM>, which may then open a contactor in the motor controller/contactor <NUM>, stop a variable speed drive, or otherwise stop protected equipment <NUM>. In other embodiments, at the time the method <NUM> opens <NUM> the contacts <NUM>, the method <NUM> may also close normally closed contacts.

If the method <NUM> determines <NUM> that the first PWM signal matches the sensed PWM signal, after a period of time the method <NUM> operates <NUM> the first switch <NUM> to close and operates <NUM> the second switch <NUM> with the second PWM signal and senses a PWM signal at the second connection <NUM> to the coil <NUM>. The method <NUM> determines <NUM> if the second PWM signal matches the sensed PWM signal. If the method <NUM> determines <NUM> that the second PWM signal does not match the sensed PWM signal, the method <NUM> opens <NUM> the contacts <NUM>, and the method <NUM> ends. If the method <NUM> determines <NUM> that the second PWM signal matches the sensed PWM signal, after a period of time the method <NUM> operates <NUM> the second switch <NUM> to close and returns to operate the first switch <NUM> with the first PWM signal. In various embodiments, the method <NUM> is implemented with the first switch <NUM>, the second switch <NUM>, the first controller <NUM>, the second controller <NUM>, the coil <NUM>, the PWM sensing circuit <NUM>, the PWM alternating circuit <NUM>, or other components described herein.

<FIG> is a schematic flow chart diagram depicting another embodiment of a method <NUM> for operation of a dual PWM relay driver with diagnostics. The method <NUM> begins and closes <NUM> the first switch <NUM> and the second switch <NUM> during startup. For example, the method <NUM> closes <NUM> the first and second switches <NUM>, <NUM> to close the contacts <NUM> of the circuit breaker/safety relay <NUM>, which allows contacts of the motor controller/contactor <NUM> to close, which starts the motor <NUM>. In other embodiments, the coil control component <NUM> and contacts <NUM> are in a safety relay, so that the method <NUM> closing <NUM> the first and second switches <NUM>, <NUM> allows operation of protected equipment <NUM>, which may include starting a motor <NUM> or allowing other equipment to operate.

The method <NUM> continues to close <NUM> both switches <NUM>, <NUM> for a startup period until at least the contacts <NUM> are closed and the method <NUM> closes <NUM> the PWM test switch <NUM> and opens <NUM> the analog test switch <NUM> and operates <NUM> the first switch <NUM> with a first PWM signal and operates <NUM> the second switch <NUM> closed. The method <NUM> senses <NUM> a PWM signal at a second connection to the coil <NUM> and determines <NUM> if the first PWM signal differs from the sensed PWM signal. If the method <NUM> determines <NUM> that the first PWM signal differs from the sensed PWM signal, the method <NUM> opens the contacts <NUM> and the method <NUM> ends. Opening the contacts <NUM> affects the protected equipment <NUM>, by stopping a motor <NUM>, disconnecting power to equipment, etc..

If the method <NUM> determines <NUM> that the first PWM signal does not differ from the sensed PWM signal for a period of time, the method <NUM> closes <NUM> the analog test switch <NUM> and opens <NUM> the PWM test switch <NUM>. The method <NUM> senses <NUM> current in the coil <NUM> and determines <NUM> if the current in the coil <NUM> is abnormal, which signals a problem with one or more of the coil <NUM>, the first switch <NUM>, the second switch <NUM>, the diode <NUM>, the current sensor <NUM>, etc. If the method <NUM> determines <NUM> that the current in the coil <NUM> is abnormal, the method <NUM> opens <NUM> the contacts <NUM> of the circuit breaker/safety relay <NUM>, and the method <NUM> ends. If the method <NUM> determines <NUM> that the current in the coil <NUM> is normal, after a time adequate to sense <NUM> abnormal current, the method <NUM> returns and closes <NUM> the PWM test switch <NUM> and opens <NUM> the analog test switch <NUM>.

At some point during normal operation where the method <NUM> continues to determine <NUM> that the first PWM signal matches the sensed PWM signal and determines <NUM> that the current in the coil <NUM> is normal, the method switches <NUM> functionality of the first switch <NUM> and the second switch <NUM> so that the method <NUM> operates <NUM> the second switch <NUM> with the second PWM signal and operates <NUM> the first switch <NUM> closed. In this operating condition, the method <NUM> determines <NUM> if the second PWM signal matches the sensed PWM signal. In various embodiments, the method <NUM> is implemented with the first switch <NUM>, the second switch <NUM>, the first controller <NUM>, the second controller <NUM>, the coil <NUM>, the PWM sensing circuit <NUM>, the current sensor <NUM>, the analog test switch <NUM>, the PWM test switch <NUM>, the diode <NUM>, the PWM alternating circuit <NUM>, the breaker close circuit <NUM>, the resistor <NUM>, the comparator <NUM>, the first microcontroller <NUM>, the second microcontroller <NUM>, etc..

Claim 1:
A safety relay (<NUM>) comprising a first switch (<NUM>), a second switch (<NUM>), a first controller (<NUM>), a second controller (<NUM>), a pulse-width modulation, PWM, sensing circuit (<NUM>), and a coil (<NUM>);
wherein the first switch (<NUM>) is connectable to a power source (<NUM>);
wherein the second switch (<NUM>) is connected between the first switch (<NUM>) and a first connection of the coil (<NUM>) of normally open contacts (<NUM>);
wherein the first controller (<NUM>) is connected to the first switch (<NUM>) for controlling the first switch (<NUM>) with a first output signal comprising one of a close signal for closing the first switch (<NUM>) and a first PWM signal with a first duty cycle for opening and closing the first switch (<NUM>) on each PWM cycle;
wherein the second controller (<NUM>) is connected to the second switch (<NUM>) for controlling the second switch (<NUM>) with a second output signal comprising one of a close signal for closing the second switch (<NUM>) and a second PWM signal with a second duty cycle for opening and closing the second switch (<NUM>) on each PWM cycle, the first duty cycle being different from the second duty cycle;
wherein the PWM sensing circuit (<NUM>) is connected to a second connection of the coil (<NUM>) for sending a sensed PWM signal to an input of the first controller (<NUM>) and an input of the second controller (<NUM>);
wherein the first controller (<NUM>) is configured to send the first PWM signal while the second controller is configured to send a close signal and wherein the second controller (<NUM>) is configured to send the second PWM signal while the first controller (<NUM>) is configured to send a close signal; and
wherein the first controller (<NUM>) is configured to verify that the received PWM signal matches the first PWM signal while sending the first PWM signal and the second controller (<NUM>) is configured to verify that the received PWM signal matches the second PWM signal while sending the second PWM signal.