Patent Application
20220263502
The present disclosure relates generally to the field of electrical relays and breakers, and in particular to a solid state contactor assembly, for making and breaking direct current.
Traditional DC output, solid state contactors (“SSCs”) employ through-hole/surface mount discrete semiconductor packages with a plurality of straight or staggered leads. Examples of such packages include such as TO-220, TO-247, TO-263 and their corresponding variants as identified by different prefix and suffix such as TO-220-3. Working with these packages have multiple disadvantages. First, these packages most commonly have a metal tab or a back plate that is not electrically isolated from the internal circuitry. Since DC output SSC will need to mount onto a heatsink, or surface that is said to be electrically conductive, non-isolated, or grounded, this results in the need for the manufacturer to implement an external electrical isolation such as a direct bonded copper (“DBC”) substrate. In addition, working with these through-hole/surface mount packages most commonly requires the SSC manufacturer to solder or weld at points of electrical coupling. Both procedures require the need for special equipment, techniques, and processes that can be both difficult and complex to implement.
The second disadvantage of traditional DC output SSC employing through-hole/surface mount semiconductor packages relates to performance limitations. For example, the protoypical DC output SSCs are not rated to switch more than 200 Adc and 150VDC. For example, the Crydom™ HDC Series™ has a maximum load current of 160 A@150VDC; and the E-T-A Circuit Breakers™ ERP10 Series™ has a maximum output of 200 A@24VDC. Such limitations are primarily imposed by the maximum ratings of the through-hole/surface mount packages themselves, including for example, thermal transfer characteristics and maximum safe RMS current carrying capacity of all electrical connections. In the case of SSCs that employ through-hole/surface mount insulated-gate bipolar transistor (“IGBT”) packages, maximum performances cannot be increased effectively by connecting more IGBTs in parallel. This is because IGBTs typically have a negative temperature coefficient. Among an array of IGBTs, the ones with lower voltage drop will conduct more current resulting in a higher operating temperature which further reduces their corresponding voltage drop and increases their load current. Given the difficulties with current sharing in a large array of IGBTs, the rated output of an IGBT based DC output solid-state relay would be largely dependent on the package limit a single IGBT component.
With SSCs that employ through-hole/surface mount metal-oxide semiconductor field-effect transistor (“MOSFET”) packages, maximum performance, such as carrying current, may be increased by coupling multiple MOSFET packages in parallel. However, at higher current, this approach may be physically unfeasible owing to the sheer number of through-hole/surface mount MOSFETs required to be coupled together for switching higher current. Moreover, due to inherent variabilities such as ON resistance and breakdown voltages among MOSFETs (of the same model), electrical load is not shared equally among all elements coupled in parallel. As a result of these current imbalances, there are diminishing returns associated with connecting more individual through-hole/surface mount MOSFETs in parallel, since the safe operational margins need to be increased for each additional semiconductor element added in parallel.
Another disadvantage of traditional DC output SSCs employing through-hole/surface mount semiconductor packages relates to overall reliability during manufacturing and design. With through-hole/surface mount semiconductor package usage, components could degrade due to repeated high temperature events during the DBC bonding, and soldering in the manufacturing process. The increased use of soldering for installing through-hole/surface mount components also increases the likelihood of soldering joint fail due to fatigue, and stress associated with constant high current and or high temperature operations. The most significant reliability issue relates to the fact that traditional DC output SSCs may require more than half-a-dozen through-hole/surface mount MOSFETs connecting in parallel for reliably switching ≥200 ADC. It should be noted, the larger the number of individual semiconductor elements used in an array, the higher the probability of failures. This is because the failure of a single semiconductor element in the array has an instantaneous impact on the power distribution of rest of the element, often triggering cascading failures of other units within the group, and ultimately rendering the DC output SSC inoperable.
For DC output SSCs, it is generally ideal to use semiconductor packages with higher individual performance. Naturally, the larger the semiconductor packaging, the better output characteristics including lead current rating, power dissipation, and thermal dissipation. However, larger packages such as chassis-mount power modules are less ideal from a control standpoint due to for example higher gate threshold voltage, and larger input capacitance. Thus, the control circuitry of DC output SSC utilizing larger power module packages need a better driving method in order to ensure proper DC switching operation.
It will be appreciated by those skilled in the art that other variations of the embodiments described below may also be practiced without departing from the scope of the invention. Further note, these embodiments, and other embodiments of the present invention will become more fully apparent from a review of the description and claims which follow.
In one embodiment of the present invention, a DC output solid state contactor includes the option to switch elements based on isolated power module semiconductor packages, namely SOT-227, and its variants denoted by different prefixes and suffixes, with higher per unit package ratings such as RMS output current capacity, and inherent electrical isolation from its baseplate. Components are coupled together within an enclosure to form an integrated panel mount design.
It is an object of the present invention to produce a DC output Solid State Contactor assembly 10 with higher continuous output current capabilities (e.g. >200 A).
It is another object of the present invention for the said assembly 10 to have an integrated, robust and all mechanical construction.
It is an additional object of the present invention to offer better reliability through a design and construction with power module packages including eliminating additional high temperature bonding and soldering events during manufacturing, minimizing gate parasitic inductance, and increasing RMS current capacity.
It is an additional object of the present invention to utilize an improved drive circuitry in order to ensure proper operation of larger power module semiconductors whether it's of IGBT, MOSFET, SicMOSFET, or other semiconductor technology.
In accordance with the objects and those that will be mentioned and will become apparent below. Briefly, in one embodiment of the present invention, the novel DC output SSC assembly 10 is a solid state contactor including a plurality of current carrying power terminals, each for connecting to the “hot side” or “low potential side” of a circuit. Based on a user input control signal, the SSC functions to permit the flow of DC current in the respective power terminals or in another functions to interrupt the flow of current in the respective terminals. In one embodiment of the present invention, each SSC assembly 10 includes one or more isolated power module(s) that can be of an IGBT, a MOSFET, a SicMOSFET or other suitable semiconductor type. In one embodiment of the present invention, the switching semiconductors(s) are of power module packages, namely SOT-227 and its variants that can be in a single element configuration or two or more elements connected in series or parallel. In one embodiment of the present invention, an improved drive circuitry is attached directly onto at least one of the power module(s), coupling to the gate electrodes of at least one of the power module(s). In one embodiment of the present invention, the drive circuitry includes a control input, a voltage priming system, a control circuit, a status and gate impulse outputs. The drive circuitry converts user control input signals into a gate impulse voltage, changing the conduction state of the power modules effectively “opening” or “closing” the switch. In one embodiment of the present invention, the entire assembly 10 is housed in an enclosure having a baseplate that attaches one of more components of the SSC assembly 10. In one embodiment of the present invention, the assembly 10 also allows the integration of additional safety elements, such as an internal transient suppression component, and insulated barriers.
Various aspects of at least one example are discussed below with reference to the accompanying figures, which are not intended to be drawn to scale. The figures are included to provide an illustration and a further understanding of the various aspects and examples, and are incorporated in and constitute a part of this specification, but are not intended as a definition of the limits of a particular example. The drawings, together with the remainder of the specification, serve to explain principles and operations of the described and claimed aspects and examples. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every figure. In the drawings:
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
References in the specification to “one embodiment”, “an embodiment”, “a preferred embodiment”, “an alternative embodiment”, “embodiments”, “variations”, “a variation” and similar phrases mean that a particular feature, structure, or characteristic described in connection with the embodiment(s) or variation(s) is included in at least an embodiment or variation of the invention. The appearances of the phrase “in one embodiment” or “in one variation” in various places in the specification are not necessarily all referring to the same embodiment or variation.
The term “couple”, “coupled”, “connected”, “joined”, “attached” or “fixed” as used in this specification and the appended claims refers to either an indirect or direct connection between the identified elements, components or objects. Often the manner of the coupling will be related specifically to the manner in which the two coupled elements interact.
The term “or” as used in this specification and appended claims is not meant to be exclusive rather the term is inclusive meaning “either or both”.
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The assembly 10 includes a control input termination 16B, enabling the user to supply a control signal voltage to command a change in the conduction state of the internal semiconductor element(s), which in turn “open” or “close” the electrical circuit the SSC is connected to. In this embodiment, the SSC electrically connects to a load via connection to a suitable power distribution device. Shown in
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In one embodiment of the present invention, the board of the drive circuit board 205 is of a “die-cut” or similar shape 207. This shape allows the drive circuit board 205 to be integrated within the confined space of the enclosure 11, while also ensuring electrical coupling is possible from the board 205 to the gate electrodes of all modules 204. The “die-cut” shape 207 also ensures electrical clearance between the board 205 and the power terminals of all modules 204 within the assembly 10.
In one embodiment, the board 205 has points of electrical input 208 for accepting the user's control input signal. In order for the user to connect external control input wires, this embodiment uses a 2-position terminal block 16B which electrically couples to input 208, while also protruding out of the epoxy layer allowing external connections to be made. In this embodiment, circuit board 205 has two pairs of output terminations (206A and 206B) for delivering corresponding gate impulses to the gate electrodes of each of the two modules in parallel. The primary gate impulse output 206A and secondary impulse output at 206B are on the same physical structure of the circuit board in this embodiment. This enables convenient mechanical and electrical coupling to the gate electrodes of each of the modules 204.
In one embodiment, both output 206A and 206B deliver a simultaneous gate impulse to each of the two modules 204 coupled in parallel, changing the conduction state of both modules 204 simultaneously. The use of a conductive structure via circuit board, as shown, minimizes inductance, and reduces possibility of gate oscillation.
In the embodiment shown, the output 206A couples to the gate electrode of the nearest module 204, and output 206B couples to the gate electrode of the second module in group 204. In a larger panel mount enclosure with more semiconductors of the same form factor, it is perceivable that the structure and coupling to the gate electrodes of additional modules 206B coupling repeats for the additional semiconductor elements down the line.
In the embodiment shown, the electrically conductive power terminals coupling the output side semiconductor terminals to the load side are indicated by reference numeral 14. In this embodiment, the power terminals are said to be in the form of a busbar with sufficient thickness and ampacity for the continuous RMS current of the DC output SSC.
Each busbar 14 of the embodiment has a cutout space 210 that ensures a safe electrical clearance and over parts of the integrated drive board 205. Both busbars vertically clear the wall of enclosure 11.
In one embodiment of the present invention, one busbar 14 mechanically and electrically couples the source electrodes 209A of each of the modules 204. The other busbar 14 mechanically and electrically couples the drain terminals 209B of each modules 204.
In one embodiment, a transient suppression device of RC snubber 211 is added to the assembly 10. The RC snubber 211 electrically and mechanically couples at ports 212 across both busbars 14, such that both modules 204 and the RC snubber 211 are said to be coupled together in parallel.
In the embodiment shown, the space between the pair of busbars 14 also includes an electrical insulated barrier 17 having surfaces 214 perpendicular to the baseplate on each side facing each busbar 14. The barrier 17 is said to be freely standing and physically fixed in place after the epoxy resin 13 hardens.
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As described herein, in one embodiment, the drive circuitry of the present invention uses voltage priming process 44. The first step of which is and it first ensure that the DC control voltage supplied by the user at 16B has the correct polarity. Thus, a polarity diode 40 is connected in series either at the positive or the negative control input side as a standard procedure. In one embodiment of a present invention that allows a control input voltage of up to 32 Vdc, the reverse blocking voltage is typically 40 Vdc or more.
Next the drive circuitry undergoes a voltage priming process 44 consisting of regulating, isolating and further converting the input voltage to gate impulses that are then delivered to the gates of power modules 204. Regulation 41 allows a wide range of user's control input voltages to be regulated accurately to a set voltage threshold typically within ±1V; In a preferred embodiment with a rated user control input voltage of 5-32Vdc, the regulation is set to 5Vdc This regulation in 41 may be achieved by using discrete devices such as voltage regulators or IC components such as linear regulator replacements. This set regulated-voltage-threshold can be of any reasonable voltage, as long as it corresponds to user's input voltage range, while also work in tandem with the following process of DC/DC isolation 42 and further DC/DC conversion 43.
The DC/DC isolation process 42, provides required electrical isolation between both the input and output voltage. In one embodiment, this step is achieved by use a DC/DC converter which provides electrical isolation of >1000VAC.
The last process as part of the initial voltage priming procedure 44 in accordance with one embodiment of the present invention, is a DC/DC conversion process 43 to ensure that the voltage to be utilized by the control circuit 45 is at an optimally high level. After regulation 41 and isolation 42, the resulting voltage is said to be at about 5Vdc in this embodiment. The voltage DC/DC conversion process 43, in this case, converted 5Vdc to a higher voltage of 14Vdc, before the voltage is sent into the control circuit. However, the DC/DC conversion process 43 may result in voltages other than 14Vdc, as long as the voltage is sufficiently high enough for power module(s) of the assembly 10 to enter an optimal conduction-state. It should be noted that regulation 41, DC/DC isolation 42 and DC/DC conversion 43 of voltage priming procedure 44 may occur in any order achieved with either a single integrated IC component, such as an isolated DC/DC converter module, or via separate IC components. The voltage priming process 44 will enable the driving of power module semiconductors which often cannot rely on driving method currently used for smaller through-hole/surface mount semiconductor packages incorporating photodiode array output optocoupler.
After the control circuitry 44 generates an optimal voltage level as the result of process 43, it produces one or more outputs in the form of gate impulse voltage, which can then be selectively delivered to the gate electrodes of each module within the assembly 10, based on set logic and or other conditions, to change their respective state of conduction. In this embodiment, the output gate impulse voltage is simultaneously delivered to the separate gate resistor 45 of both MOSFETs, effectively turning on or off both transistors at the same time since both MOSFETs' gate electrodes are coupled to 206A and 206B in the embodiment of the control circuit.
In this embodiment, with both MOSFET modules entering a conduction state by receiving their gate impulses, a current flows between the drains and the sources of both MOSFET modules. The user's electrical circuit coupled to the SSC assembly's power terminals 14 are effectively turned ON or OFF by this operation. In this embodiment, there is also a transient suppression device, a RC snubber circuit, coupled to output power terminals 14, which in turn is coupled to the drains and the sources of all MOSFET modules connected in parallel in this embodiment. This transient suppression device 211 may also be a diode, MOV, or alike.
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Examining the waveforms that occurred in a single cycle of the preferred embodiment, before T=0, the drive circuitry does not receive a control voltage input and remains at 0V. As a result, before T=0, there is no gate impulse voltage produced at output 206A or 206B, and both MOSFET modules remain non-conducting. At T=0, a control input voltage of 4.5Vdc is applied to the terminals 16B. After this voltage is treated by a priming process 43 and then sent through the control circuit, at T=1, an output gate impulse voltage of 13.5Vdc is generated at both output 206A and 206B. Output 206A is coupled to the gate and the source of the first MOSFET module, and output 206B is coupled to the gate and the source of the second MOSFET module. When a sufficiently high gate impulse voltage of 13.5Vdc is received at the gate electrodes of both MOSFET modules simultaneously changes to a conducting state, closing the switch and allowing current to flow. At T=2, the user no longer supplies a control input voltage. As a result of this change, at T=3, both gate impulse drops to 0Vdc again, and both MOSFET modules in this embodiment are no longer in a conducting state.
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The DC output SSC assembly 10 disclosed herein offers improvements in areas of construction, performance and reliability over prior art devices. When fitted in an industry-standard panel mount enclosure, the novel DC output SSC assembly 10 can be rated for a continuous current of 400 Amp or greater.
The scope of this disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of this disclosure is not limited to the example embodiments described or illustrated herein. Moreover, although this disclosure describes and illustrates respective embodiments herein as including particular components, elements, functions, operations, or steps, any of these embodiments may include any modification, combination or permutation of any of the components, elements, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. All such modifications, combinations and permutations are believed to be within the sphere and scope of the invention as defined by the claims appended hereto.
| Number | Date | Country | |
|---|---|---|---|
| 63149311 | Feb 2021 | US |
