Interrupting circuit for a radio frequency generator

Information

  • Patent Grant
  • 10993293
  • Patent Number
    10,993,293
  • Date Filed
    Monday, December 23, 2013
    11 years ago
  • Date Issued
    Tuesday, April 27, 2021
    3 years ago
Abstract
An interrupting circuit is configured to monitor for and detect a fault in a device for generating a field of electromagnetic radiation (e-field) from a radio frequency (RF) generator configured to convert low voltage direct current (DC) into the e-field for application to an article in the e-field. If a fault is detected, the interrupting circuit interrupts low voltage DC between an energy reserve and the RF generator within a predetermined time less than the time to dissipate energy stored in the energy reserve.
Description
BACKGROUND

A radio frequency (RF) amplifier, or RF generator, is capable of generating a field of electromagnetic radiation (e-field) in the radio frequency spectrum from a power source. An energized RF generator may be configured to generate an e-field that may interact with external objects in a desirable or predictable manner. Typically, an RF generator is further coupled with an RF antenna or applicator in order to apply or direct the e-field as needed to interact with the external objects. For example, a microwave oven typically utilizes an AC power input provided to an RF generator to generate an e-field to heat or cook food items.


SUMMARY

The invention relates to a device for generating a field of electromagnetic radiation (e-field) from a radio frequency (RF) generator configured to convert low voltage direct current into the e-field for application to an article in the e-field. The device includes a generator power supply connected between a power source and the RF generator. The generator power supply has one or more energy reserves and one or more power conversion circuits to convert power to low voltage DC for the RF generator. One or more interrupting circuits are configured to monitor for and detect a fault in the device. If a fault is detected, an interrupting circuit interrupts the low voltage DC between the energy reserve and the RF generator within a predetermined time less than the time to dissipate energy stored in the energy reserve.





BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:



FIG. 1 is a schematic view of an RF oven in accordance with one embodiment of the invention;



FIG. 2 is a schematic view of the power source, generator power supply, RF generator, and RF applicators of FIG. 1, in accordance with one embodiment of the invention;



FIG. 3 is a graphic representation of a reflective e-field power as a function of time in accordance with one embodiment of the invention;



FIG. 4 is a graphical representation of the integral of the reflected e-field power of FIG. 3 as a function of time in accordance with one embodiment of the invention; and



FIG. 5 is graphical representation of a step-down process for controlling applied power in accordance with one embodiment of the invention.





DETAILED DESCRIPTION

The invention may be implemented in any environment using a radio frequency (RF) generator or amplifier capable of generating a field of electromagnetic radiation (e-field) in the radio frequency spectrum regardless of the application of the e-field and regardless of the frequency or frequency range of the e-field. For purposes of this description, any e-field generating device, for example, a microwave or infrared signal generator, will be generally referred to as an RF generator, or similar language, and any e-field applying device, such as an antenna or anode/cathode coupling or pair, will be generally referred to as an RF applicator. These descriptions are meant to make clear that one or more frequencies or frequency ranges of e-field may be included in embodiments of the invention. While this description is primarily directed toward an RF oven providing an e-field capable of heating and or cooking food (collectively, “cooking”), it is also applicable to alternative uses of e-field generation, for example, for drying fabrics.



FIG. 1 schematically illustrates an RF device 10 in the form of an oven comprising a cabinet 12 defining a cavity 14 for electromagnetically heating and/or cooking food, or foodstuff, in the cavity 14. The oven 10 is shown further comprising a door 16 moveably mounted to the cabinet 12, an RF shielding layer, for example, wire mesh 18, removably or fixedly attached to the cabinet 12 and door 16, and at least one door interlock switch, illustrated as a first door switch 20 and a second door switch 22, each switch 20, 22 capable of independently providing a signal indicative of the state of the door 16.


The oven 10 may further include an RF generator 24, for example a microwave generator, having at least one RF amplifier, shown as a first solid state RF amplifier 26 and a second solid state RF amplifier 28. The oven 10 further includes at least one RF applicator, illustrated as a first RF applicator 30 and a second RF applicator 32, each applicator 30, 32 configured to apply an e-field 34 to the cavity 14. The oven 10 also has a generator power supply 36 such as a microwave generator power supply, a power source 38, for example, mains power, and a controller 40. While the cavity 14 is illustrated including the RF generator 24 and the first and second RF applicators 30, 32 located in opposing corners of the cavity 14, embodiments of the invention contemplate alternative placements of the components 24, 30, 32, including a configuration wherein the RF generator 24 is located outside of the cavity 14. Furthermore, while the generator power supply 36, power source 38, controller 40, and each of the door switches 20, 22 are shown outside of the cabinet 12, they are collectively envisioned to be included as components of the oven 10, and various placements of the aforementioned components 20, 22, 36, 38, 40 are contemplated, which may include placement within the cavity 14, cabinet 12, and/or wire mesh 18, or in the instances of the door switches 20, 22, any placement such that the switches 20, 22 are capable of determining the state of the door 16.


As shown, the first RF amplifier 26 may be electrically coupled with the first RF applicator 30 and the second RF amplifier 28 may be electrically coupled with the second RF applicator 32. The RF generator 24 may also be electrically coupled with the generator power supply 36, which may further be electrically coupled to the power source 38. The controller 40 is shown communicatively coupled (illustrated as dotted lines) to each door switch 20, 22 and each RF applicator 30, 32, and providing communication signals to each of the RF generator 24 and generator power supply 36.


The door 16 provides movement between an opened state and a closed state, or condition, to selectively provide access to the cavity 14, for instance, to allow for inserting food items to be cooked or for removing food items previously cooked. When closed, the door 16 and corresponding wire mesh 18 segment are configured to align with the cabinet 12 to effectively prevent access to, and/or effectively seal, the cavity 14. The cavity 14 is further sealed due to the configuration of the wire mesh 18 which operates to prevent any e-field leakage into, or out of, the cabinet 12 and cavity 14.


The RF generator 24 is configured to receive a power input and may generate one, two, three, four, or any number of RF signals, as needed by the particular oven application. The RF generator 24 is further configured to deliver each respective signal to a corresponding RF amplifier 26, 28. In the example illustrated, the RF generator 24 is capable of generating two RF signals, which are delivered to corresponding first and second RF amplifiers 26, 28, each of which amplifies an independent RF signal. It is envisioned each RF signal may correspond to at least one RF amplifier 26, 28. Thus, non-limiting examples of embodiments of the invention are envisioned wherein one RF signal may correspond to one RF amplifier 26, two RF signals may correspond to two respective RF amplifiers 26, 28, three RF signals may correspond to three respective RF amplifiers, or four RF signals may correspond to four respective RF amplifiers, etc. Additionally, non-limiting examples of embodiments of the invention are envisioned wherein one RF signal may correspond to, for example, two, three, or four RF amplifiers, such that each amplifier amplifies the same RF signal. Any number of combinations and/or permutations of any number of RF signals and/or RF amplifiers as described are envisioned.


Each RF amplifier 26, 28 may be correspondingly configured to deliver the amplified signal to the one or more RF applicators 30, 32, which are configured to direct the amplified RF signal, shown as an e-field 34, into the cavity 14. The generator power supply 36 may be additionally configured to operatively convert power received to an alternative power output. For example, the generator power supply 36 may be configured to convert an AC power input to a high current, low voltage DC output. Alternative power conversions are envisioned, and the example provided is merely one non-limiting example of a power conversion. Additionally, the controller 40 may be any appropriate device that is capable of receiving input signals, generating, processing, and/or determining commands, and providing the commands and/or command signals based on said commands, as one or more outputs. For example, the controller 40 may include one or more programmable logic devices, application specific integrated circuits, digital signal processors, and/or microcontrollers.


During operation of the oven 10, food items to be cooked are placed into the cavity 14 via the open door 16, and then the door 16 is closed. The controller 40 operates to control the oven 10 such that the power supply 38 provides a power input to the generator power supply 36, which is controlled to convert the power input from the power supply 38 to a sufficient power output delivered to the RF generator 24. One example of the generator power supply 36 may include, for instance, converting a mains power input of alternating current (AC) to a low voltage direct current (DC) output. The RF generator 24 may generate a radio frequency electromagnetic radiation (e-field) signal, which may be significantly or trivially amplified by each respective first and second RF amplifier 26, 28, and delivered from each RF amplifier 26, 28 to the respective first and second RF applicators 30, 32 for application of the electromagnetic radiation to the cavity 14.



FIG. 2 schematically illustrates the generator power supply 36 and RF generator 24 in further detail. The generator power supply 36 further comprises at least one interrupting circuit having electrical decoupling capabilities, shown as a first interrupting circuit 42 and a second interrupting circuit 44, at least one energy reserve, shown as a first energy reserve 46 and a second energy reserve 48, and at least one power conversion circuit, for example, an AC to DC converter 50 and/or a DC to DC converter 52. Additionally, each RF amplifier 26, 28 may further comprise a temperature circuit 54.


As shown, the power source 38 is electrically coupled with the first interrupting circuit 42, which is further coupled with the AC to DC converter 50. The first energy reserve 46 is electrically coupled to both the AC to DC converter 50 and the DC to DC converter 52. The second energy reserve 48 electrically couples the DC to DC converter 52 to the second interrupting circuit 44, which is further coupled with the RF generator 24. The controller 40 is communicatively coupled via communication lines (illustrated as dotted lines) to each of the first and second interrupting circuits 42, 44 and each temperature circuit 54.


Each of the aforementioned couplings between the power source 38, generator power supply 36 components 42, 44, 46, 50, 52, and RF generator 24 are shown having two electrical connections, for instance, a voltage line 78 and a ground line 80, but alternative electrical connections are envisioned. Each of the first and second interrupting circuits 42, 44 is positioned on at least one of the voltage line 78 or the ground line 80, or the interrupting circuit 42, 44 is positioned on both the voltage line 78 and the ground line 80.


Each interrupting circuit 42, 44 may be configured to electrically couple the connected components while in a first, closed state, and may be configured to electrically decouple the connected components while in a second, open state. Each interrupting circuit 42, 44 may be further configured to monitor the electrical couplings and detect a fault between respective components, such as irregular or erroneous power characteristics, for example current and/or voltage characteristics. In this respect, each of the first and second interrupting circuits 42, 44 may be considered to include the controller 40 which participates in monitoring and detecting a fault in the oven 10 as well as controlling the coupling or decoupling functions of the first and second interrupting circuits 42, 44. Additionally, each energy reserve 46, 48 is capable of regulating the generator power supply 36 power during operation and supplying an amount of power even during a fault event such as a break in operation, at each respective coupling location. In one example, the energy reserve 46, 48 may comprise a capacitor or an energy buffer which may provide power to the respective components for more than 300 milliseconds (ms) after a fault such as a break in the circuit.


Additionally, while a temperature circuit 54 is described, it is envisioned that the temperature circuit 54 may comprise a temperature sensor, or another, non-temperature sensor circuit, for determining the actual or estimated temperature of each respective RF amplifier 26, 28 without a temperature sensor. For example, a temperature circuit 54 is envisioned wherein the temperature circuit 54 may be initially calibrated to the respective RF amplifier 26, 28 using, for example a negative temperature coefficient (NTC) thermistor or sensor, to generate and/or provide a thermal model for the temperature circuit 54. In this example, the thermal model may be calibrated once by measuring the temperature of the RF amplifier 26, 28 while generating an RF feed from the RF amplifier 26, 28 using, for example, forward and reflected power while utilizing or not utilizing an actual temperature sensor. In other words, the thermal model is calibrated to the RF amplifier 26, 28. Additionally, the above described calibration and/or thermal model may be based on a lumped elements model or a distributed elements model. It is further contemplated that the temperature circuit 54 may be disposed in the RF generator 24 for determining the actual or estimated temperature of the RF generator 24 as a whole.


During RF generator 24 operation, the power source 38 may provide, for example, AC power to the generator power supply 36. The AC power arrives through the first interrupting circuit 42 in a closed state, and may be delivered to the AC to DC converter 50, where the AC power input is converted to a DC power output. The DC power output is supplied to the first energy reserve 46 and further delivered to the DC to DC converter 52, which converts the DC power output of the AC to DC converter 50 to a low voltage DC output. The low voltage DC output may be supplied to the second energy reserve 48, which may be further supplied through the second interrupting circuit 44, in a closed state, to the RF generator 24.


The controller 40 controls the generator power supply 36, the RF generator 24, and each interrupting circuit 42, 44 such that the oven 10 applies a desired e-field 34 to the cavity 14. However, in the event of a fault in the oven 10, the controller 40 may operate one, both, or any permutation of a number of interrupting circuits 42, 44 to change the respective interrupting circuits 42, 44 to an open state, which decouples the generator power supply 36 from the power source 38, or source of mains power. One example of a fault that may trigger the use of one or more interrupting circuits 42, 44 by the controller 40 may be when one or more door switches 20, 22 indicate the door 16 is moved to the open condition. Another example of a fault that may trigger the use of one or more interrupting circuits 42, 44 by the controller 40 may be one or more interrupting circuits 42, 44 monitoring and detecting an irregular or erroneous power characteristic between the aforementioned components, or between the power source 38, or the source of mains power, and the generator power supply 36, e.g., a break in the mains power or power source 38 to the generator power supply 36.


Yet another example of a fault that may trigger the use of one or more interrupting circuits 42, 44 by the controller 40 may be based on a determination by one or more temperature circuits 54 that an irregular and/or erroneous temperature condition exists based on a temperature reading, sensing, estimation, or comparison. In this example, an RF feed may be generated from the RF amplifier 26, 28. The temperature circuit 54 may measure the gain of the respective RF amplifier 26, 28 while generating the RF feed, and may then compare the measured gain, which may be over time, to a thermal model of the temperature circuit 54. The temperature circuit 54 may then estimate the temperature of the respective RF amplifier 26, 28 based on the comparison of the measured gain to the thermal model. Non-limiting examples of the RF feed may include the power provided to the RF amplifier 26, 28, the amount of energy amplified or consumed during operation of the RF generator 24 and/or the RF amplifier 26, 28.


In this example utilizing the temperature circuit 54, the method described may be further characterized by creating a prediction model based on the comparison, and may, for example, generate a fault indication or estimate the temperature of the RF amplifier 26, 28, based on the prediction model. Furthermore, the method described may be utilized to estimate the temperature of any power transmission system, a dummy load, or a circulator in the RF amplifier 26, 28. As well, any of the foregoing methods may be applied to estimating the temperature of the RF generator 24.


In yet another example a fault may be based on the power reflections in at least one of the cavity 14, either one or both RF amplifiers 26, 28, and/or either one or both RF applicators 30, 32. It is known that e-field 34 reflections occur due to load mismatch. In order to avoid high levels of e-field 34 reflections, embodiments of the invention are envisioned wherein one or more of the cavity 14 or aforementioned components 26, 28, 30, 32 may be capable of, or may contain an e-field 34 sensing device capable of determining a reflected power, and provide the e-field 34 sensing information to the controller 40, such that the controller 40 may make a determination of a fault based on the reflected e-field 34. For instance, in one embodiment of the invention, the controller 40 may take into account all reflected e-fields 34 from each RF amplifier 26, 28, or each RF channel, in making a determination. In another instance, the controller 40 may also take into account, or filter out, reflected e-field 34 levels that are within a normal, or expected operating ranges.


For example, FIG. 3 illustrates an exemplary first graph 56 demonstrating, for instance, a measured amount of e-field 34 reflection in the cavity 14 as a function of time. FIG. 4 illustrates a corresponding second graph 58 that shows the integral of the first graph 56, as a function of time. In the second graph 58, the dotted line represents a predetermined amount of integrated reflected e-field 60 that must be accumulated before the controller 40 determines a fault occurs. As shown in the second graph 58, the controller 40 would determine that a fault occurs at a time 62. Alternatively, embodiments of the invention are envisioned wherein the integral of the reflected e-field 34 is based on a moving predetermined time window, such that only the amount of reflected e-field 34 in, for example, the most recent one second, is summed. Thus, in this alternative example, a fault would only occur if the integrated e-field 34 reflected is greater than a predetermined amount of reflected e-field 60 for any given, consecutive, one second period. Alternative summation techniques, as well as alternative time periods, are envisioned.


During operation, if a fault is detected, regardless of which of the above-described methods determines the fault, the controller 40 may operate one or more interrupting circuits 42, 44. If the controller 40 operates the second interrupting circuit 44 to interrupt the low voltage DC power to the microwave RF generator 24, any residual power in the first or second energy reserves 46, 48 is barred from reaching the RF generator 24 so that power can be cut off faster than if the first interrupting circuit 42 were the only interrupting circuit 42, 44 operated. Preferably the second interrupting circuit 44 is configured to monitor for and detect a fault and if a fault is detected, to interrupt the low voltage DC to the RF generator 24 within a predetermined time, which may be less than the time necessary to dissipate the energy stored in one or more energy reserves 46, 48. In one non-limiting example, the predetermined time may be 20 ms, or within 20 ms of the fault detection.


Alternatively, during operation, if a fault is detected, regardless of which of the above-described methods determines the fault, the controller 40 may operate the generator power supply 36, the RF generator 24, and/or any number of the RF amplifiers 26, 28 to derate the e-field generation. For example, one embodiment of the invention is envisioned wherein the controller 40 may determine the temperature of one or more of the RF amplifiers 26, 28 (as described above), and also estimate or determine the amount of reflected e-field 34 power between the at least two RF amplifiers 26, 28, (i.e. a “crosstalk” power level). Based on the temperature determination and/or the crosstalk estimation, the controller 40 may reduce the transmitted e-field 34 power level for at least one of the RF amplifiers 26, 28 in at least a two-step process.



FIG. 5 illustrates a third graph 64 of an exemplary two-step process, as described. As shown, the amount of power applied by one or more RF applicators 30, 32 may change as a function of temperature. For example, the applied power 66 may be a maximum power level 68 of applicable power until it is determined that the temperature of at least one of the RF amplifiers 26, 28 is above a first predetermined temperature threshold, shown as a first threshold temperature 70. Similarly, the applied power 66 may be a maximum power level 68 of applicable power until a crosstalk power level is estimated between two or more of the RF amplifiers 26, 28, where the crosstalk power level is above a second predetermined threshold, as described above. When either or both of these conditions are met, a fault or error may be detected. Upon detecting such a fault or error, the applied e-field 34 power may be reduced to a first power level 72, which is less than the maximum power level 68.


In instances where even the first power level 72 continues to increase the temperature of one or more RF amplifiers 26, 28 or the cross talk power level of two or more of the RF amplifiers 26, 28, the power levels may be further reduced. For example, if it is determined that the temperature of at least one of the RF applicators 30, 32 reaches a second threshold temperature 74, and/or if it is estimated that the crosstalk power levels reach another predetermined threshold, the power level may further be reduced as shown, to an even lower second power level 76. Any number of power levels may continue to reduce the amount of applied power 66 until, for example, the temperature stabilizes or reduces below a predetermined level, or the estimated crosstalk power level stabilizes or reduces below a predetermined level or the RF amplifiers 26, 28 are powered off entirely after reducing the power level to zero.


It is envisioned that where a plurality of RF amplifiers 26, 28 generate multiple RF e-fields 34, or feeds, at different frequencies, the transmitted power level may be reduced only for those RF amplifiers 26, 28 where the temperatures exceed the first predetermined threshold, or where the cross talk power levels exceed the second predetermined threshold. Stated another way, embodiments are envisioned where each RF amplifier 26, 28 is independently operated based on the temperature or e-field 34 reflections measured by the respective RF amplifier 26, 28. Alternatively, embodiments of the invention are envisioned wherein the transmitted power level is reduced for all RF amplifiers 26, 28 when any temperatures exceed the first predetermined threshold or when any crosstalk power levels exceed the second predetermined threshold. In another alternative embodiment, the transmitted power level is reduced for all RF amplifiers 26, 28 when any temperatures exceed the first predetermined threshold and when any crosstalk power levels exceed the second predetermined threshold.


Many other possible embodiments and configurations in addition to that shown in the above figures are contemplated by the present disclosure. For example, one embodiment of the invention contemplates redundant components, such as a second controller or multiple temperature circuits to provide increased reliability or comparisons of functionality. Another embodiment of the invention contemplates directly coupling one or more door sensors 20, 22 directly to one of more interrupting circuits 42, 44 such that when the door is moved to an open state, the interrupting circuits 42, 44 interrupt the power from the power source 38 to the RF generator 24 immediately, without controller 40 operation. Additionally, the design and placement of the various components may be rearranged such that a number of different in-line configurations could be realized.


The embodiments disclosed herein provide a method for operating a radio frequency generator. One advantage that may be realized in the above embodiments is that the above-described embodiments have superior failure prevention capabilities. With the proposed fault determinations and detections and the power stepping and/or power interruption, as described above, any RF application can be accomplished with reduced risk of overheating, e-field leakage, and/or severe e-field interference (i.e. reflections, crosstalk) compared to conventional RF applications. The reduced risk of overheating also reduces risk of component scorching or burning, and reduces the fire risk for the RF application. Yet another advantage of the above-described embodiments is that the interrupting circuits provide a reliably fast way to interrupt the RF generation prior to the dissipation of the energy within the energy reserves of the generator power supply. Thus, the RF generation may be abruptly stopped prior to energy dissipation generating additional e-fields, which may be irregular, or increase fault-causing conditions, such as increase the excess temperature of the cavity.


Yet another advantage of the above-described embodiments includes the capability to provide an estimate RF applicator temperature without the need of providing a direct temperature sensor. This may result in reduced component expenses, which has a direct competitive advantage. Finally, by providing an RF application the capabilities to prevent over-temperature conditions, the reliability of the entire RF system, including the components, is increased due to reduced thermal stresses. The above-described conditions further reduce the mean time between failures (MTBF) and reduce the likelihood of system failure due to excessive temperature.


It is contemplated that the present disclosure encompasses at least the following inventive concepts:


Interrupting Circuit for RF Generator

1. A device (10) for generating a field of electromagnetic radiation (e-field) (34) from a radio frequency (RF) generator (24) configured to convert low voltage direct current (DC) into the e-field (34) for application to an article in the e-field (34), comprising a generator power supply (36) connected between a power source (38) and the RF generator (24), the generator power supply (36) having at least one energy reserve (46, 48) and at least one power conversion circuit (50, 52) to convert power to low voltage DC for the RF generator (24), characterized by:

    • at least one interrupting circuit (44) configured to monitor for and detect a fault in the device (10), and if a fault is detected, to interrupt the low voltage DC between the at least one energy reserve (46, 48) and the RF generator (24) within a predetermined time less than the time to dissipate energy stored in the at least one energy reserve (46, 48).


2. The device (10) of 1, wherein the device is one of an RF oven or an RF dryer.


3. The device (10) of 1, wherein the device is an oven having a cabinet (12) defining a cavity (14) for electromagnetically heating a foodstuff in the cavity; a door (16) moveably mounted to the cabinet for movement between opened and closed conditions to selectively provide access to the cavity; and at least one door interlock switch (20, 22) that causes a fault when the door is moved to the open condition.


4. The device (10) of any one of 1-3, wherein the power supply (38) is connected to the RF generator (24) by a voltage line (78) and a ground line (80), and the at least one interrupting circuit (44) is in one of the voltage line (78) or the ground line (80).


5. The device (10) of 2, comprising an interrupting circuit (44) in each of the voltage line (78) and the ground line (80).


6. The device (10) of any one of 1-5, wherein the predetermined time is 20 ms.


Method of Derating Power Amplifiers in a Microwave Oven

1. A method of derating at least one radio frequency (RF) amplifier in a device configured to generate RF feeds, the method characterized by:

    • determining the temperature of the at least one RF amplifier; and
    • reducing the transmitted power level for at the at least one RF amplifier in at least two steps when the temperature of at least one RF amplifier is above a first predetermined threshold.


2. The method of 1, including estimating a crosstalk power level between at least two RF amplifiers; and

    • reducing the transmitted power level for at the at least two RF amplifiers in at least two steps when the crosstalk power level is above a second predetermined threshold.


3. The method of 1 or 2, wherein a plurality of RF amplifiers generates multiple RF feeds at different frequencies, and the transmitted power level is reduced only for those RF amplifiers where the temperatures exceed the first predetermined threshold or where the crosstalk power levels exceed the second predetermined threshold.


4. The method of 3, wherein the transmitted power level is reduced for all RF amplifiers when any temperatures exceed the first predetermined threshold or when any crosstalk power levels exceed the second predetermined threshold.


5. The method of 3, wherein the transmitted power level is reduced for all RF amplifiers when any temperatures exceed the first predetermined threshold and when any crosstalk power levels exceed the second predetermined threshold.


Method of Determining Temperature of Solid State Amplifier

1. A method of determining the temperature of a radio frequency (RF) amplifier without a temperature sensor in a device configured to generate RF feeds, the method characterized by:

    • providing a thermal model calibrated to the RF amplifier;
    • generating an RF feed from the RF amplifier;
    • measuring gain of the RF amplifier while generating the RF feed;
    • comparing the measured gain over time to the thermal model; and
    • estimating the temperature of the RF amplifier based on the comparison.


2. The method of claim 1, further characterized by creating a prediction model based on the comparison.


3. The method of claim 1, wherein the thermal model is calibrated once by measuring the temperature of the RF amplifier while generating an RF feed from the RF amplifier using forward and reflected power, with or without a temperature sensor.


4. The method of any one of claims 1-3, wherein the temperature of a power transmission system or a dummy load or a circulator in the RF amplifier is estimated.


5. The method of any one of claims 1-4, wherein the thermal model is a lumped elements model or a distributed elements model.


To the extent not already described, the different features and structures of the various embodiments may be used in combination with each other as desired. That one feature may not be illustrated in all of the embodiments is not meant to be construed that it may not be, but is done for brevity of description. Thus, the various features of the different embodiments may be mixed and matched as desired to form new embodiments, whether or not the new embodiments are expressly described. All combinations or permutations of features described herein are covered by this disclosure.


This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims
  • 1. A device for generating a field of electromagnetic radiation (e-field) from a radio frequency (RF) generator configured to convert low voltage direct current (DC) into the e-field for application to an article in the e-field, comprising: a generator power supply connected between a power source and the RF generator, the generator power supply having at least one energy reserve and at least one power conversion circuit to convert power to low voltage DC for the RF generator, and at least one interrupting circuit configured to monitor for and detect a fault in the device, and if the fault is detected, to interrupt the low voltage DC between the at least one energy reserve and the RF generator within a predetermined time less than the time to dissipate energy stored in the at least one energy reserve, wherein the predetermined time is 20 ms.
  • 2. The device of claim 1, wherein the device is one of an RF oven or an RF dryer.
  • 3. The device of claim 1, wherein the article is a foodstuff and the device is an oven having a cabinet defining a cavity for electromagnetically heating the foodstuff in the cavity; a door moveably mounted to the cabinet for movement between opened and closed conditions to selectively provide access to the cavity; and at least one door interlock switch that triggers the fault when the at least one door interlock switch indicates that the door is moved to the opened position.
  • 4. The device of claim 1, wherein the power supply is connected to the RF generator by a voltage line and a ground line, and the at least one interrupting circuit is positioned on at least one of the voltage line and the ground line.
  • 5. The device of claim 4, wherein the at least one interrupting circuit is positioned on each of the voltage line and the ground line.
PCT Information
Filing Document Filing Date Country Kind
PCT/US2013/077431 12/23/2013 WO 00
Publishing Document Publishing Date Country Kind
WO2015/099649 7/2/2015 WO A
US Referenced Citations (98)
Number Name Date Kind
2742612 Cohn Apr 1956 A
2981904 Ajioka et al. Apr 1961 A
3265995 Hamasaki Aug 1966 A
3430023 Tingley Feb 1969 A
3737812 Gaudio et al. Jun 1973 A
3784781 Foerstner Jan 1974 A
4088861 Zwillinger May 1978 A
4139828 Commault et al. Feb 1979 A
4143646 Sampsel et al. Mar 1979 A
4196332 MacKay et al. Jan 1980 A
4277671 Mori Jul 1981 A
4354562 Newman Oct 1982 A
4374319 Guibert Feb 1983 A
4415887 Kawase Nov 1983 A
4463324 Rolfs Jul 1984 A
4628351 Heo Dec 1986 A
4703151 Sakamoto Oct 1987 A
4743728 Nagafusa et al. May 1988 A
4786774 Kaminaka Nov 1988 A
4870238 Hodgetts et al. Sep 1989 A
4886046 Welch et al. Dec 1989 A
4937413 Spruytenburg et al. Jun 1990 A
5075525 Jung Dec 1991 A
5256859 Nanos Oct 1993 A
5369254 Kwon Nov 1994 A
5483045 Gerling Jan 1996 A
5619983 Smith Apr 1997 A
5831253 Han et al. Nov 1998 A
5878910 Gibemau et al. Mar 1999 A
5919389 Uehashi et al. Jul 1999 A
5973305 Kim et al. Oct 1999 A
5981929 Maeda et al. Nov 1999 A
6018158 Kang Jan 2000 A
6054696 Lewis et al. Apr 2000 A
6057535 Derobert et al. May 2000 A
6097019 Lewis et al. Aug 2000 A
6268593 Sakai Jul 2001 B1
6359270 Bridson Mar 2002 B1
6429370 Norte et al. Aug 2002 B1
6557756 Smith May 2003 B1
6559882 Kerchner May 2003 B1
6853399 Gilman et al. Feb 2005 B1
7193195 Lundstrom et al. Mar 2007 B2
7361871 Cho et al. Apr 2008 B2
7476828 Genua Jan 2009 B2
7482562 Song et al. Jan 2009 B2
7926313 Schenkl et al. Apr 2011 B2
8074637 Yamauchi Dec 2011 B2
8389916 Ben-Shmuel et al. Mar 2013 B2
8455803 Danzer et al. Jun 2013 B2
8492686 Bilchinsky et al. Jul 2013 B2
8530807 Niklasson et al. Sep 2013 B2
8610038 Hyde et al. Dec 2013 B2
8745203 McCoy Jun 2014 B2
8803051 Lee et al. Aug 2014 B2
9131543 Ben-Shmuel et al. Sep 2015 B2
9132408 Einziger et al. Sep 2015 B2
9179506 Sim et al. Nov 2015 B2
9215756 Bilchinsky et al. Dec 2015 B2
9374852 Bilchinsky et al. Jun 2016 B2
9560699 Zhylkov et al. Jan 2017 B2
9585203 Sadahira et al. Feb 2017 B2
20050134469 Odorcic Jun 2005 A1
20060289526 Takizaki et al. Dec 2006 A1
20090134155 Kim et al. May 2009 A1
20090160417 Klimczak Jun 2009 A1
20100181307 Richardson Jul 2010 A1
20110031236 Ben-Shmuel et al. Feb 2011 A1
20110168699 Oomori et al. Jul 2011 A1
20110290790 Sim et al. Dec 2011 A1
20120067872 Libman et al. Mar 2012 A1
20120103972 Okajima May 2012 A1
20120152939 Nobue et al. Jun 2012 A1
20130048881 Einziger et al. Feb 2013 A1
20130142923 Torres et al. Jun 2013 A1
20130156906 Raghavan et al. Jun 2013 A1
20130186887 Hallgren et al. Jul 2013 A1
20130200066 Gelbart et al. Aug 2013 A1
20130277353 Joseph et al. Oct 2013 A1
20140168830 Vangool Jun 2014 A1
20140277100 Kang Sep 2014 A1
20150034632 Brill et al. Feb 2015 A1
20150136758 Yoshino et al. May 2015 A1
20150156827 Ibragimov et al. Jun 2015 A1
20150173128 Hosokawa et al. Jun 2015 A1
20150289324 Rober et al. Oct 2015 A1
20150305095 Huang et al. Oct 2015 A1
20150334788 Hofmann et al. Nov 2015 A1
20150373789 Meusburger et al. Dec 2015 A1
20160029442 Houbloss et al. Jan 2016 A1
20160088690 Kubo et al. Mar 2016 A1
20160119982 Kang et al. Apr 2016 A1
20160219656 Hunter, Jr. Jul 2016 A1
20160327281 Bhogal et al. Nov 2016 A1
20160353528 Bilchinsky et al. Dec 2016 A1
20160353529 Omori et al. Dec 2016 A1
20170099988 Matloubian et al. Apr 2017 A1
20170105572 Matloubian et al. Apr 2017 A1
Foreign Referenced Citations (51)
Number Date Country
1523293 Aug 2004 CN
101118425 Feb 2008 CN
201081287 Jul 2008 CN
102620324 Aug 2012 CN
103156532 Jun 2013 CN
203025135 Jun 2013 CN
105042654 Nov 2015 CN
204987134 Jan 2016 CN
106103555 Nov 2016 CN
0493623 Aug 1992 EP
1193584 Mar 2002 EP
1424874 Jun 2004 EP
1426692 Jun 2004 EP
1795814 Jun 2007 EP
2031938 Mar 2009 EP
2220913 May 2011 EP
2405711 Nov 2012 EP
2012162072 Nov 2012 EP
2618634 Jul 2013 EP
2775794 Sep 2014 EP
2976651 Dec 2012 FR
639470 Jun 1950 GB
2367196 Mar 2002 GB
S55155120 Dec 1980 JP
57194296 Dec 1982 JP
59226497 Dec 1984 JP
H0510527 Jan 1993 JP
H06147492 May 1994 JP
10160167 Jun 1998 JP
2000304593 Nov 2000 JP
2008108491 May 2008 JP
2011146143 Jul 2011 JP
2013073710 Apr 2013 JP
2050002121 Jul 2005 KR
101359460 Feb 2014 KR
20160093858 Aug 2016 KR
2122338 Nov 1998 RU
2122338 Nov 1998 RU
2215380 Oct 2003 RU
2003111214 Nov 2004 RU
2008115817 Oct 2009 RU
2008137844 Mar 2010 RU
03077601 Sep 2003 WO
2008018466 Feb 2008 WO
2008102360 Aug 2008 WO
2009039521 Mar 2009 WO
2011138680 Nov 2011 WO
2012001523 Jan 2012 WO
2011039961 Feb 2013 WO
2015024177 Feb 2015 WO
2016128088 Aug 2016 WO
Related Publications (1)
Number Date Country
20160323939 A1 Nov 2016 US