Abstract:
A solid-state switch, comprising at least one switch controller. At least one switch having a first terminal coupled to a power source, a second terminal coupled to the power source and a control terminal coupled to the switch controller and configured to selectively conduct and block current flow from the first terminal to the second terminal. At least one power converter coupled to the first terminal and the second terminal and configured to convert power from the power source from a first voltage level to a second voltage level and to provide power at the second voltage level to the switch controller.

Description:
RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Patent Application No. 62/031,066, filed Jul. 30, 2014, which is hereby incorporated by reference for all purposes as if set forth herein in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates generally to solid state relays, and more specifically to biasing and redirecting energy in a solid state relay to provide power to other relays, as well as to redirect and balance energy across an isolated or non-isolated secondary region to the primary region. 
       BACKGROUND OF THE INVENTION 
       [0003]    Solid state relays provide a more reliable and faster means to switch loads on and off in a secondary region. When compared to mechanical relays, solid state relays have a much longer cycle life and can turn loads on and off much faster. One of the challenges with solid state relays is that they require a constant charge on the control gate. As such, this constraint requires the control circuit to be constantly operating, which can reduce the battery life when the control circuit is a portable device, as is often the case when a separate power source is not provided for the control circuit. 
         [0004]    The prior art solid state relay  100  shown in  FIG. 1  uses a capacitor  102  to isolate the solid state switch SW 1  and SW 2  from the primary side to the secondary side. In 24 VAC systems, the ground line is not available, and only the VAC line (common) and the load lines are available. Because there is no ground line, there is no robust supply path on the secondary side. Therefore, the power to charge the gates of SW 1  and SW 2  is provided by continuously clocking the isolating capacitor  102  that is tied to solid-state relay  100 . This continued clocking consumes continuous power from the primary side. In many cases, the primary side is battery powered, and therefore, the battery power is consumed. 
       SUMMARY OF THE INVENTION 
       [0005]    A solid-state switch is disclosed that includes at least one switch controller and at least one switch having a first terminal coupled to a power source, a second terminal coupled to the power source and a control terminal coupled to the switch controller and configured to selectively conduct and block current flow from the first terminal to the second terminal. At least one power converter is coupled to the first terminal and the second terminal and is configured to convert power that is provided by the power source from a first voltage level to a second voltage level and to provide power at the second voltage level to the switch controller. 
         [0006]    Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0007]    Aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views, and in which: 
           [0008]      FIG. 1  is a diagram of a prior art relay; 
           [0009]      FIG. 2  is a diagram of a circuit in which the system supply energy is provided by a full-bridge diode bridge  202 ; 
           [0010]      FIG. 3  is a diagram of a circuit for implementing more than one solid-state switch in a system, in accordance with an exemplary embodiment of the present disclosure; 
           [0011]      FIG. 4  is a diagram of a waveform of a differential voltage of the disclosed system, in accordance with an exemplary embodiment of the present disclosure; 
           [0012]      FIG. 5  is a diagram of a system for providing power sharing in a multiple relay system, in accordance with an exemplary embodiment of the present disclosure; 
           [0013]      FIG. 6  is a diagram of of a switching regulator that is configured to turn a switch on once the voltage across the input terminals of comparator reaches near the target reference voltage, and to turn off when the voltage when it exceeds the comparator voltage; 
           [0014]      FIG. 7  is a diagram of a switching regulator that is configured to step a voltage down from a bridge rectifier, which is internal to a solid state relay; 
           [0015]      FIG. 8  is a diagram of circuit where the secondary side can transfer energy to the primary side by use of a boost converter that then transfers the energy across capacitor to the primary side; 
           [0016]      FIG. 9  is a diagram of a system that provides additional control functionality within the solid-state relay; and 
           [0017]      FIG. 10  is a diagram of an automotive control circuit in accordance with an exemplary embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    In the description that follows, like parts are marked throughout the specification and drawings with the same reference numerals. The drawing figures might not be to scale and certain components can be shown in generalized or schematic form and identified by commercial designations in the interest of clarity and conciseness. 
         [0019]    Referring to  FIG. 1 , it would be more desirable to be able to latch the solid state relay  100  on and not to continuously provide a clock signal. This configuration would allow the primary side control system to save power. 
         [0020]    Solid-state relays can be used for driving 24 VAC systems, including but not limited to HVAC control systems, security systems, smoke detector systems, water sprinkler control systems and pool control systems. These systems can be configured to use isolated and non-isolated power systems. Because there is no supply and ground line located at the secondary side of the solid state relay, energy can be alternatively received by rectifying the energy across the common line and a load line using a diode bridge or other suitable circuits. When a switch is in the off position, the diode bridge can provide energy across the rectifier. A problem with this architecture is that if too much load current is drawn in the off-state switch, the load can inadvertently turn on, because the load current threshold for switching on the load is met. This is undesirable and can cause the system to work in an incorrect manner. Alternatively, energy transfer across a rectifier or other suitable power converter can be limited to occur only when the switch is in the off-state. Therefore, when the switch is in the on-state, energy will not be transferred across the rectifier. The relay of the present disclosure can thus obtain its own power from the secondary circuit power source, to enable more control functionality, such as a latching mode, a switching control, a watchdog heartbeat control, fault reporting, current control and other suitable controls. 
         [0021]    The terminology used herein is for the purpose of describing particular examples and is not intended to be limiting of the disclosed subject matter. Like reference numbers refer to like elements throughout the specification. As used herein the term “and/or” includes any combination of one or more of the associated listed items. Also, as used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Also, as used herein, relational terms such as first and second, top and bottom, left and right, and the like may be used to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. 
         [0022]      FIG. 2  is a diagram of a circuit  200  in which the system supply energy is provided by a full-bridge diode bridge  202 , and which provides a voltage bias to the V SYS + and V SYS − pins. In order to better control a solid-state relay switch and to optimize the control of the system, system power can be rectified from the switch terminals SW 1  and SW 2 . Circuit  200  can be implemented in hardware or a suitable combination of hardware and software. 
         [0023]    As used herein, “hardware” can include a combination of discrete components, an integrated circuit, an application-specific integrated circuit, a field programmable gate array, or other suitable hardware. As used herein, “software” can include one or more objects, agents, threads, lines of code, subroutines, separate software applications, two or more lines of code or other suitable software structures operating in two or more software applications, on one or more processors (where a processor includes a microcomputer or other suitable controller, memory devices, input-output devices, displays, data input devices such as a keyboard or a mouse, peripherals such as printers and speakers, associated drivers, control cards, power sources, network devices, docking station devices, or other suitable devices operating under control of software systems in conjunction with the processor or other devices), or other suitable software structures. In one exemplary embodiment, software can include one or more lines of code or other suitable software structures operating in a general purpose software application, such as an operating system, and one or more lines of code or other suitable software structures operating in a specific purpose software application. As used herein, the term “couple” and its cognate terms, such as “couples” and “coupled,” can include a physical connection (such as a copper conductor), a virtual connection (such as through randomly assigned memory locations of a data memory device), a logical connection (such as through logical gates of a semiconducting device), other suitable connections, or a suitable combination of such connections. 
         [0024]    A storage element, such as capacitor  204 , can store energy for use by the system. Alternatively, the V SYS + and V SYS − pins can be tied to other solid-state relays in the system and can share a common energy storage element. The stored energy in this energy storage element can provide power for control  206 , which drives the solid state switches  208  and  210  that are placed across switch terminals SW 1  and SW 2 . The substrate (SUB) can be biased below the potential of the source and/or V SYS − pin by using a negative boost circuit (not explicitly shown). This configuration provides additional robustness for the system by minimizing the risk of causing a parasitic bipolar component to turn on, which can cause device failure. Parasitic active devices such as bipolar components are common in solid-state circuits, and although MOS devices are shown in circuit  200 , an insulated gate bipolar transistor, bipolar junction transistor or any other suitable low impedance, high voltage device can also or alternatively be used. 
         [0025]    Alternatively, power can be provided to a solid-state relay such as system  200  by using active control switches. These active control switches can be used to either limit current or turn power received from the system on or off through the switch terminals. 
         [0026]    System  200  further includes diodes  212 ,  214 ,  216 ,  218 ,  220 ,  222  and  224 , which are used to control current flow in system  200 . 
         [0027]      FIG. 3  is a diagram of a circuit  300  for implementing more than one solid-state switch in a system, in accordance with an exemplary embodiment of the present disclosure. Circuit  300  can be implemented in hardware or a suitable combination of hardware and software. 
         [0028]    Microcontroller  302  is configured to control relays  304 A through  304 N, and is isolated by one or more isolation capacitors  306 , which can be external isolation capacitors as shown, internal isolation capacitors that are included in relays  304 A through  304 N, or other suitable isolation capacitors. Each of the control inputs (CTRL) of relays  304 A through  304 N can have their own dedicated isolation capacitor, can share one common isolation capacitor  306  as shown, or can utilize other suitable configurations. In this configuration, a common V SYS  capacitor C SYS  is used to store charge that is transferred from a diode bridge or other suitable rectifier of the respective off-state solid-state relays  304 A through  304 N. Additionally, a negative voltage boost circuit  308  can be used to bias SUB negative with respect to the V SYS − voltage potential. The clock signal for the negative voltage boost can be provided from the primary side clock (CLK) or other suitable sources. 
         [0029]    Alternatively, the clock signal can be provided from one or more of the solid-state relays. The negative voltage boost circuit  308  is shown as a charge pump circuit having a capacitor C PUMP  and diodes  310  and  312 , but can also or alternatively use other suitable types of circuits to accomplish the same result, such as a magnetic boost regulator. 
         [0030]    A 24 VAC voltage source V AC  provides a supply voltage to solid-state relays  304 A through  304 N, which are used to controllably provide power to load impedances  314  and  316 . The current drawn by load impedances  314  and  316  can be monitored over time to detect changes that indicate incipient failure or other fault conditions. In addition, the 24 VAC source can be used to power additional fault detection circuitry, load monitoring and control circuitry or other suitable circuitry (not explicitly shown), where high frequency data communications can also be transmitted over 24 VAC power network  318 . In one exemplary embodiment, microcontroller  302  can be configured to read the voltage drop across load impedances  314  and  316 , and to track changes in load current over time, such as to detect an incipient failure mode. Likewise, other suitable current sensing mechanisms can also or alternatively be used. In addition, a data communication device located at V AC  (not explicitly shown) can be used to communicate with control devices located at load impedances  314  and  316  or in other suitable locations, so as to facilitate communication between devices on 24 V AC  power network  318 . In this exemplary embodiment, components in an HVAC control system, security system, smoke detector system, water sprinkler control system, pool control system or other suitable systems that utilize 24 VAC power or other suitable power sources can be configured to communicate with each other as well as a system gateway, which can also or alternatively be configured to provide Internet of Things (IOT) connectivity with an external network such as the Internet or other suitable networks. 
         [0031]      FIG. 4  is a diagram of a waveform  400  of the V SYS + and V SYS − differential voltage of system  300 , in accordance with an exemplary embodiment of the present disclosure. Waveform  400  shows that the negative boost allows the substrate to be at a lower voltage bias than the V SYS − pin. This voltage bias assures that the parasitic NPN within the solid-state circuit will not turn on, which either could cause the device to operate improperly or even cause destruction of the device. During the positive cycle of the 24 VAC voltage waveform, the parasite PNP can turn on, which can cause the bias voltage of the substrate to rise. To minimize this rise, a larger C SUB  capacitor can be used to minimize this effect. Alternatively a positive boost circuit can be used to cause the V SYS + pin to be at a voltage potential that is always larger than the 24 VAC signal. This differential voltage can be used to prevent the parasitic PNP from inadvertently turning on. 
         [0032]      FIG. 5  is a diagram of a system  500  for providing power sharing in a multiple relay system, in accordance with an exemplary embodiment of the present disclosure. System  500  can be implemented in hardware or a suitable combination of hardware and software. 
         [0033]    In this exemplary embodiment, a current limit and/or control device ILIMIT  502  can be used to control the amount of power that is received from the switch terminals SW 1  and SW 2 . I CONTROL  is driven by control  504 , which can receive control data CTRL from a primary side controller. By using current control, the leakage current across the switch pins SW 1  and SW 2  can be controlled and minimized to assure that the leakage current will not provide enough parasitic current through the system load to inadvertently turn on the system load that is being controlled by a specific solid-state switch. System  500  further includes diodes  506 ,  508 ,  510 ,  512 ,  514 , rectifier bridge diodes  516 ,  518 ,  520  and  522 , switches  524  and  526  and capacitor  528 . 
         [0034]    In addition to controlling the current, the voltage at the outputs of the V SYS  pins can also be regulated. Voltage regulation can be controlled by switching regulators that use switched capacitor, switched magnetics, a combination of both or other suitable functionality. Alternatively, regulated output can also be controlled by a linear switching control that only operates in a low impedance state and that provides power when the 24 VAC voltage waveform is near the desired voltage output. 
         [0035]      FIG. 6  shows an example of a switching regulator  600  that is configured to turn switch  604  on once the voltage across the input terminals of comparator  602  reaches near the target reference voltage, and to turn off when the voltage exceeds the comparator voltage. For example, when an inductive load is being powered, operation of switch  604  at a point in time where the voltage waveform is not at a minimum can result in current transients with a relatively high peak current magnitude, due to the discharge of stored energy in the inductive load. By preventing operation of switch  604  at such voltages, switching regulator  600  helps to improve system operation and avoids potential damage and wear to the system from large current transients. 
         [0036]    Switching regulator  600  can also minimize power dissipation by only charging the output regulator when the voltage drop is minimal, thereby maximizing efficiency. Circuit  600  further includes diode  606 , capacitor  608 , transistor  610 , diode  612 , capacitor  614  and resistor  616 . Energy is stored in capacitor  608  when transistor  610  is off, to provide an efficient system where transistor  610  only needs to turn on when the conditions allow for minimal power loss. Diode  612  prevents unwanted current flow from the output or discharging of capacitor  608 . Capacitor  614  and resistor  616  control the transients seen at the input. 
         [0037]      FIG. 7  is a diagram of a switching regulator  700  that is configured to step a voltage down from a bridge rectifier  702 , which is internal to a solid state relay. Switching regulator  700  can be implemented in hardware or a suitable combination of hardware and software. 
         [0038]    The voltage output from the bridge rectifier  702  is V SYS + and V SYS −, which is then used to control the power to one or more other solid state relays. The switching pin can alternatively be used to toggle voltage across a capacitor and then the energy across this capacitor can be transferred to the primary side and be stored and used to power the primary controller system. Alternatively, magnetic coupling can be used to transfer energy from the secondary side to the primary side as well. 
         [0039]    Switches  712  and  714  can either be integrated inside of the solid state switch or implemented as discrete devices. Switching regulator control  704  can be modified by control device  706  based on the voltage observed on the primary side. Alternatively, power transfer circuitry can be added to provide either isolated or non-isolated regulated power to both the solid-state control device as well as power to the primary side. 
         [0040]    Solid-state control device  706  can transmit control data and receive data feedback through a capacitor interface to each of the switches, such as through capacitors  710 ,  716  and  718 . Alternatively a single capacitor interface can be used to transfer control information and data information back to the primary controller. Data transfer protocols such as serial interface bus, LVDS, I2C, CAN, LIN, UART or other suitable single or multi-wire protocols can be used to transfer data. This data can be used to control regulation, the solid state switch or other functions inside  704 . 
         [0041]      FIG. 8  is a diagram of circuit  800 , where the secondary side can transfer energy to the primary side by use of a boost converter that then transfers the energy across capacitor  802  to the primary side. Circuit  800  can be implemented in hardware or a suitable combination of hardware and software. Alternatively a magnetically coupled interface can be used to transfer energy from the secondary side to the primary side. Alternatively, inductor  804  can be replaced with a FET, resistor or another suitable device to pull up to Vsys+. 
         [0042]    Microcontroller  808  can send data to control device  806  to modify frequency or pulse width, so as to control the voltage seen at the primary side. Data transfer protocols such as serial interface bus, LVDS, I2C, CAN, LIN, UART or other suitable single or multi-wire protocols can be used to transfer data. This same data path can be used to control the state or function of the solid state switch. 
         [0043]      FIG. 9  is a diagram of a system  900  that provides additional control functionality within the solid-state relay. System  900  can be implemented in hardware or a suitable combination of hardware and software. 
         [0044]    System  900  includes microcontroller  902 , which is coupled to integrated controller  904 . Integrated controller  904  controls the operation of switches  906 ,  908 ,  910  and  912 , can measure load currents through impedances  914  and  916 , can measure load voltages, can store data and programming in a local memory device, can execute stored control algorithms, can download updated control algorithms, can generate status messages and alerts, and can perform other suitable functions. 
         [0045]    The added control functionality and memory can be used to monitor the 24 VAC load, such as to detect low voltage conditions, overvoltage conditions, intermittent voltage failure conditions or other suitable conditions. The additional control functionality provides for management of load profiles of the system loads, which can be placed into a look up table and compared. Both voltage and current profiles can be evaluated during switching, so as to allow for changes from the load to be monitored and evaluated. The solid-state system can determine whether the load is in an on or off state, and can take corrective actions to modify the switch settings for switches  906 ,  908 ,  910  and  912 , such as by using pulse width modulation, by changing the switch impedance or in other suitable manners. Additionally, high frequency data communications can be modulated onto the 24 VAC line from the control device, such as by modulating a waveform pattern on top of the 24 VAC line and load, by pulse width modulating the switch to the load or in other suitable manners. The respective loads can then receive information that can be used at the end system, such as for control and operation of a compressor, a heater unit, a camera, a microphone, a water sprinkler head, a damper, a servomotor, or other suitable devices. Data communication from the end device can use load dithering that can be evaluated by the solid-state system or other suitable signal processing techniques. 
         [0046]    The solid state relay can also or alternatively be used to drive DC voltages, such as those that are used in automatic test equipment or other equipment and systems that require the use of isolated relays. Alternatively, the isolated switch can be used to control one or more switches in a power management system where switching regulation is required but isolation is necessary to control the switch. 
         [0047]      FIG. 10  is a diagram of an automotive control circuit  1000  in accordance with an exemplary embodiment of the present disclosure. Automotive control circuit  1000  can be implemented in hardware or a suitable combination of hardware and software. 
         [0048]    Automotive control circuit  1000  includes high power switch  1006  and high power diode  1004 , which are coupled to battery  1002  and load  1010 . Controller  1008  is coupled to high power switch  1006 , load  1010  and load current sensor  1012 . In operation, load  1010  can draw current from battery  1002 , such as a starter motor, a compressor, an electric motive device, or other suitable load devices. During normal operation, high power switch  1006  is closed and conducts current from battery  1002  to load  1010 . However, when controller  1008  detects a fault condition, it generates control data to open switch  1006 , so as to prevent damaging reverse current flow in the event that the operator of an automobile associated with automotive control circuit  1000  inadvertently connects a replacement battery or supplemental battery to battery  1002  in a reverse polarity, as such reverse polarity connections can result in damaging current flow in the opposite direction of a design current flow direction. In this configuration, diode  1004  blocks the reverse current until the fault condition is corrected, at which point controller  1008  closes switch  1006  to bypass diode  1004 . In this manner, high magnitude current does not flow through diode  1004  under normal operation, as that can cause heating damage to occur to diode  1004 , which can ultimately result in failure of diode  1004 . Nevertheless, diode  1004  is used to prevent damage resulting from inadvertent imposition of reverse polarity on automotive control circuit  1000 . 
         [0049]    It should be emphasized that the above-described embodiments are merely examples of possible implementations. Many variations and modifications may be made to the above-described embodiments without departing from the principles of the present disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.