Zero cross control for temperature-controlled appliance

Abstract

To provide zero cross control for a temperature-controlled appliance.SOLUTION: An appliance controller is operatively connected to a switching device for selectively actuating the switching device to connect a component to an AC power supply. The appliance controller executes a zero cross control module synchronizing actuation of the switching device with zero crossings of the AC power supply. The zero cross control module is agnostic to amplitude and frequency of the AC power supply. For example, the zero cross control module synchronizes actuation of the switching device with zero crossings of the AC power supply to minimize inrush current to a DC fan or a refrigeration compressor. The controller is used to actuate a switching device of the appliance at a switch actuation time determined by the zero cross control module, and thereby a phase offset between switching and a true zero cross of the AC power supply is less than ±35°.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates generally to temperature control equipment (e.g., refrigeration equipment). More particularly, this disclosure relates to low-cost, high-precision zero-crossing control for switching devices that selectively connect AC power to power components of the equipment. [Background technology]

[0002] Temperature control equipment (e.g., refrigeration equipment) utilizes switching devices to selectively activate power components by connecting them to a main AC (alternating current) power source. For example, it is common for refrigeration equipment to use mechanical relays to switch compressors on and off. It is well known that such mechanical relays can fail due to electrical arcing that occurs when the switching element moves between open and closed. Arcing occurs when the switching device is activated when the AC power source voltage is non-zero. The greater the absolute value of the voltage at the time of switch activation, the more severe the arcing can be. Arcing problems are typically solved by using oversized relays that are stronger than would otherwise be necessary in the absence of arcing, which increases the cost of the equipment.

[0003] Switch actuation timing can also affect the reliability of power equipment components through other paths. For example, the equipment industry has recently begun to transition from AC-powered fans to DC-powered fans. These fans have integrated AC / DC conversion circuitry that converts the main AC power source to DC and drives the fan motor with the DC power. Like the refrigeration compressor described above, the AC power supply to these fans can be controlled by switching devices (e.g., mechanical relays, solid-state relays, triacs, thyristors, etc.). Activating these switching devices when the AC power source has a non-zero voltage causes inrush currents. Unfortunately, AC / DC conversion circuitry has proven susceptible to damage from such inrush currents, significantly reducing the useful life of DC fans and making them less than expected.

[0004] In view of the above, there is a need for precision control that synchronizes the timing of the operation of equipment switching devices to "zero crossings" when the AC power source voltage is near zero. Efforts have been made to develop stand-alone microcontrollers dedicated to zero crossing control. Such zero crossing controllers are located between the main equipment controller and the switching devices. However, using an additional microcontroller undesirably increases cost and complexity. Furthermore, existing zero crossing controllers use algorithms that are frequency and / or amplitude dependent. As a result, zero crossing controllers can only operate on a particular standard power grid where the AC power source has expected characteristics. If such a zero crossing controller is used, for example, in a foreign country where the AC power source has a different frequency and / or amplitude, the zero crossing controller may perform worse, e.g., cause greater relay arcing and higher inrush currents than would be possible without zero crossing control altogether. Summary of the Invention [Means for solving the problem]

[0005] In one aspect, the cooling equipment includes a housing. A compression-driven refrigeration system cools a load within the housing. The compression-driven refrigeration system includes a refrigeration circuit filled with a refrigerant. The refrigeration circuit includes a heat-absorbing heat exchanger in thermal communication with the load, a heat-rejecting heat exchanger thermally isolated from the load, and a compressor that circulates the refrigerant between the heat-absorbing heat exchanger and the heat-rejecting heat exchanger. The fan is configured to move air across one of the heat-absorbing heat exchanger and the heat-rejecting heat exchanger. The switching device is operable to selectively connect one component selected from a group of components consisting of the compressor and the fan to an AC power source having periodic zero crossings where the voltage of the AC power source is zero. An equipment controller is operably connected to the switching device to selectively operate the switching device connecting the one component to the AC power source. The equipment controller includes a processor and a memory storing processor-executable instructions that, when executed by the processor, configure the processor to execute a zero-crossing control module that synchronizes operation of the switching device to zero crossings of the AC power source. The zero crossing control module is independent of the amplitude and frequency of the AC power supply.

[0006] In another aspect, a temperature control appliance includes an enclosure. The temperature control device controls the temperature of a load within the enclosure. A DC fan moves air to one of (i) distribute air within the enclosure or (ii) exchange heat between the temperature control device and an ambient environment. A switching device is operable to selectively connect the DC fan to an AC power source having periodic zero crossings where the voltage of the AC power source is zero. An appliance controller is operatively connected to the switching device to selectively operate the switching device connecting the DC fan to the AC power source. The controller includes a processor and a memory storing processor-executable instructions that, when executed by the processor, configure the processor to execute a zero-crossing control module that synchronizes operation of the switching device to zero crossings of the AC power source and minimizes inrush current to the DC fan.

[0007] In another aspect, a method for operating a temperature control device includes using circuitry to process an AC power source and output a low-voltage periodic signal synchronized to the AC power source. Using a comparator, the low-voltage periodic signal is compared to a reference voltage and a digital pulse signal indicating the relationship between the low-voltage periodic signal and the reference voltage is output. The digital pulse signal has a pulse width and a period. Using a processor in a controller of the temperature control device, the pulse width and period are determined. Using the processor, a switch actuation time is determined as a function of the pulse width and period. Using the controller, a switching device of the temperature control device is operated to connect a power component of the temperature control device to the AC power source at the switch actuation time, wherein a phase shift between the switching and a true zero crossing of the AC power source is less than ±35 degrees.

[0008] Other aspects and features are apparent below. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic block diagram of a cooling device according to the present disclosure; [Figure 2] FIG. 1 is a circuit diagram of an analog front end for a controller of a cooling device. [Figure 3] (a) is a diagram showing a 60Hz, 120V AC power supply. (b) is a diagram showing a low-voltage signal output from the analog front end after processing the AC power supply in (a). (c) is a diagram showing a digital pulse signal showing the relationship between the low-voltage periodic signal in (b) and the reference voltage Vref. [Figure 4] (a) is a diagram showing a 50Hz, 220V AC power supply. (b) is a diagram showing the low-voltage signal output from the analog front end after processing the AC power supply in (a). (c) is a diagram showing the digital pulse signal showing the relationship between the low-voltage periodic signal in (b) and the reference voltage Vref. [Figure 5A]1 is a diagram produced by a Tektronix measurement instrument showing the inrush current from an AC power supply and a 240v, 60hz power supply to a load after activation of a switching device in accordance with the zero crossing control module of the present disclosure. [Figure 5B] 1 is a diagram produced by Tektronix measurement equipment showing the inrush current from an AC power supply and a 240V, 60Hz power supply to a load after activation of a switching device with a conventional control module at approximately peak voltage. [Figure 6] 1 is a diagram produced by a Tektronix measurement instrument showing the inrush current from an AC power supply and a 120V, 50Hz power supply to a load after activation of a switching device in accordance with the zero crossing control module of the present disclosure. [Figure 7] 1 is a diagram produced by a Tektronix measurement instrument showing the inrush current from an AC power supply and a 240v, 60hz power supply to a load after activation of a switching device in accordance with the zero crossing control module of the present disclosure. [Figure 8] 1 is a diagram produced by a Tektronix measurement instrument showing the inrush current from an AC power supply and a 240V, 50Hz power supply to a load after activation of a switching device in accordance with the zero crossing control module of the present disclosure. [Figure 9] 1 is a diagram produced by a Tektronix measurement instrument showing the inrush current from an AC power supply and a 120V, 60Hz power supply to a load after activation of a switching device in accordance with the zero crossing control module of the present disclosure. [Figure 10] 10 is a bar graph illustrating the cycle life of relays controlled by different control systems, including a control system controlled by the zero crossing control module of the present disclosure.

[0010] Corresponding reference characters indicate corresponding parts throughout the drawings. DETAILED DESCRIPTION OF THE INVENTION

[0011] Referring now to FIG. 1 , an exemplary embodiment of an apparatus according to the present disclosure is generally indicated by the reference numeral 10. The apparatus 10 includes a control system, generally indicated at 11, configured to perform zero-crossing control, which minimizes wear and tear on power components by synchronizing switch actuation to the zero-crossings of the AC power source 12 when the voltage is near zero. As described in more detail below, the control system 11 integrates zero-crossing control at a very low cost, and furthermore, because the zero-crossing control is independent of the amplitude and frequency of the AC power source 12, it is highly accurate across international electrical standards. Thus, the control system 11 allows large manufacturers to use a single zero-crossing solution for equipment products sold and used worldwide, greatly simplifying supply chain management and manufacturing on a global scale. The zero-crossing control disclosed herein is also valuable to smaller manufacturers because of its high accuracy and low cost, insofar as it provides an inexpensive method for significantly reducing destructive wear caused by arcing and inrush currents when switching is not synchronized.

[0012] In the exemplary embodiment, the device 10 is a temperature control device, more specifically, a refrigeration device. The refrigeration device includes an enclosure, generally designated 20, configured to at least partially enclose a load L, and at least one refrigeration system 22, filled with a refrigerant and configured to cool or reject heat from the load. Those skilled in the art will recognize that there are various types of refrigeration devices, including refrigerators, freezers, ice makers, blast coolers, and combinations thereof. In this disclosure, "refrigeration device" may include any type of refrigeration device. Furthermore, this disclosure is not intended to be limited to refrigeration devices. Refrigeration device 10 is shown by way of example only. This disclosure expressly contemplates that the principles of control system 11 can be used in other types of temperature control devices or other kitchen appliances. Furthermore, the principles of this disclosure are suitable for use in HVAC or HVACR systems.

[0013] Appliances within the scope of this disclosure include an appliance controller (including a suitably programmed microprocessor) that selectively activates one or more switching devices that connect AC power to the appliance's power components (e.g., compressors, motors, etc.). For example, food warming enclosures, ovens, grills, and other types of appliances are contemplated within the scope of this disclosure. In certain exemplary embodiments, appliances within the scope of this disclosure include an AC power switching device operably connected to a DC fan and DC fan motor with integrated AC / DC conversion circuitry. As described more fully below, refrigeration appliance 10 is one example of such appliance, and control system 11 significantly improves the appliance's operating life and reliability.

[0014] The refrigeration system 22 includes a complete compression-driven refrigeration circuit, the basic elements of which include a heat-absorbing heat exchanger 24 (e.g., an evaporator assembly), a compressor 26 that circulates a refrigerant through the refrigeration circuit, a heat-rejecting heat exchanger 28 (e.g., a condenser assembly), an expansion device 30, and interconnecting tubing. Those skilled in the art are familiar with the function and operation of these basic components (and other components) in a compression-driven refrigeration circuit. The evaporator assembly 24 is in thermal communication with the load L to absorb heat from the load. The condenser assembly 28 is thermally isolated from the load L to reject heat from the load, for example, to the ambient environment.

[0015] The example cooling apparatus 10 further includes an evaporator fan 32 and a condenser fan 34 configured to move air across the evaporator assembly 24 and the condenser assembly 28, respectively. In certain example embodiments, one or both of the fans 32, 34 are DC fans that include a DC motor 36 and integrated AC / DC conversion circuitry 38 that converts AC power from the power source 12 to DC power that powers each motor.

[0016] The control system 11 includes a temperature controller (generally, an appliance controller), generally designated 40, and one or more switching devices 42, 44, 46 that selectively connect one or more power components 26, 32, 34 of the appliance 10 to the AC power source 12. In an exemplary embodiment, the control system 11 includes switching devices 42, 44, 46 operably connected between the controller 40 and each of the compressor 26, the DC evaporator fan 32, and the DC condenser fan 34. Any suitable type of switching device may be used for any of the switching devices 42, 44, 46. For example, in one or more embodiments, each switching device 42, 44, 46 is a mechanical relay. In certain embodiments, one or more of the switching devices 42, 44, 46 may include a solid-state relay, a triac, a thyristor, or any other suitable type of switching device. Although three separate switching devices 42, 44, 46 for three separate power components 26, 32, 34 are shown schematically for purposes of explanation, it is understood that the apparatus may include a single switching device connected in parallel to multiple power components (e.g., one mechanical relay may be connected to the compressor and evaporator fan to control these components in parallel).

[0017] The controller 40 is operatively connected to the switching devices 42, 44, 46 to selectively operate each switching device connecting each component (e.g., the compressor 26, the evaporator fan 32, or the condenser fan 34) to the AC power source 12. In the exemplary embodiment, the controller 40 is a temperature controller (or cooling controller) operatively connected to a temperature sensor 48 in thermal communication with the load L. The temperature sensor 48 is configured to output a signal representative of a temperature associated with the load L. In the embodiment, the temperature controller 40 uses the signal from the temperature sensor 48 as an input for thermostatic control of the temperature of the load L. More specifically, the controller 40 selectively operates one or more of the switching devices 42, 44, 46 based on the signal from the temperature sensor 48 to thermostatically control the temperature of the load L. In addition to thermostatic control, the controller 40 may be configured to control one or more of the switching devices 42, 44, 46 based on other basic equipment control algorithms. For example, it is known to control refrigeration equipment components based on timers, defrost control algorithms, condenser cleaning algorithms, ice making cycle algorithms, blow-chill algorithms, and other types of basic equipment control logic. Controller 40 may be configured to control switching devices 42, 44, 46 based on any of the above, or any others known to those skilled in the art, without departing from the scope of the disclosure.

[0018] The example control system 11 further includes a door sensor 49 on the housing 20 configured to indicate when an enclosure door (not shown) has been opened. The controller 40 is operatively connected to the door sensor 49 to receive a signal from the door sensor indicating when the door has been opened or closed. The controller 40 may be configured to selectively activate one or more of the switching devices 42, 44, 46 based on the door sensor 49. For example, depending on the type of refrigeration appliance 10, it may be known to cycle the compressor 26 and / or the evaporator fan 44 between on and off operation when the output from the door switch 49 indicates that the enclosure door has been opened.

[0019] The appliance controller 40 includes an analog front end 50 operatively connected to the AC power source 12, a comparator 52 operatively connected to the analog front end, a microprocessor 54 operatively connected to the analog front end, and a memory 56 in operative communication with the microprocessor. The memory 56 stores processor-executable instructions that configure the microprocessor 54 to control the appliance 10. For example, the memory 56 stores instructions defining a basic appliance control module 561 that configures the microprocessor 54 to perform basic appliance controls (e.g., thermostat control, ice making control, blow-chill control, defrost control, and / or maintenance controls (e.g., condenser cleaning control)) by selectively using the appliance's power components 26, 32, 34 based on inputs received from the appliance sensors 48, 49, timers, and / or user inputs. Additionally, the example memory 56 stores processor-executable instructions defining a zero-crossing control module 562 that, when executed by the microprocessor 54, configures the microprocessor to synchronize operation of one or more of the switching devices 42, 44, 46 with zero crossings of the AC power source 12. In other words, the zero-crossing control module configures the microprocessor 54 to delay operation of each of the switching devices 42, 44, 46 until the voltage of the AC power source 12 is approximately zero (e.g., when the phase shift between the switching time and the true zero crossing is less than ±35 degrees, less than ±30 degrees, less than ±20 degrees, less than ±15 degrees, less than ±5 degrees, less than ±4 degrees, or less than ±3 degrees). Additional details regarding example logic for the zero-crossing control module 562 are described in more detail below. However, it can be seen in FIG. 1 that, in certain embodiments, the zero-crossing control module 562 and the basic equipment control module 561 can be executed by the same microprocessor 54. Due to the impressive simplicity of the zero-crossing control module 562 and the low-cost analog front-end 40 (described in more detail below), effective zero-crossing control can be achieved without a separate microcontroller dedicated to the task.Therefore, the zero crossing control module 562 does not add direct cost to an instrument with a digital microcontroller, and the overall control system adds only very little incremental hardware cost for the analog front end 50 .

[0020] The analog front end 50 includes low-cost circuitry configured to process the AC power source 12 and output a low-voltage periodic signal that is synchronized to the AC power source. Figure 3(a) shows an example of an AC power source 12 that complies with the North American Electric Power Standard. Figure 3(b) illustrates an example low-voltage signal 72 output from the analog front end 50 (as shown in Figure 2) after processing the AC power source 12 illustrated in Figure 3(a). As can be seen, the example low-voltage signal 72 has voltage peaks synchronized to the voltage peaks of the AC power source and a periodic signal P of the AC power source. AC Synchronized period P LV The AC power supply 12 is a rectified half-wave power supply having a frequency of 100 kHz.

[0021] Referring to FIG. 2, in an exemplary embodiment, analog front-end 50 includes a voltage divider comprised of three resistors 60, 62, and 64, capacitor 66 configured as a capacitive filter to remove high-frequency noise, and diode 68 configured as a half-wave rectifier to rectify half-wave of low-voltage periodic signal 72a from AC power source 12 (see FIG. 3(b) and compare with FIG. 3(a)). In one exemplary embodiment, resistors 60, 62, and 64 function as a 100:1 voltage divider. In this embodiment, resistor 60 comprises a 499k resistor, resistor 62 comprises a 499k resistor, and resistor 64 comprises a 10k resistor. Those skilled in the art will appreciate that the circuitry of exemplary analog front-end 50 can be manufactured very inexpensively (e.g., on the order of a few cents or less).

[0022] 3(b) and 3(c), the comparator 52 compares the low voltage periodic signal 72 from the analog front end 50 with a reference voltage v ref Compared to the low voltage periodic signal 72 and the reference voltage v ref3(b), the reference voltage v ref is set to be greater than 0 volts and less than the peak voltage of the low voltage periodic signal 72 from the analog front end 50. In an exemplary embodiment, the comparator 42 determines whether the low voltage periodic signal 72 is greater than the voltage reference v ref , the digital pulse signal 82 has a pulse width T pw and period T p It has.

[0023] The microprocessor 54 executing the zero crossing control module 562 determines the pulse width T pw and period T p and calculate the switch activation time T as a function of pulse width and period. switch In one or more embodiments, the zero-crossing control module 562 is configured to determine the pulse width T pw and period T p In particular, the zero-crossing control module 562 may be configured to store and / or periodically update the value of T in the memory 56. More specifically, the zero-crossing control module 562 may be configured to calculate the switch actuation time T after the rising edge T of the pulse signal 82. switch In an exemplary embodiment, the processor 54 is configured to activate each switching device 60, 62, 64 at a switch activation time T switch For example, the pulse width T pw 1 / 2 and period T p It is determined as a function of 3 / 4 of the value. Formula 1:T switch =1 / 2*T pw +3 / 4*T p -T delay however, T switch is the switch activation time, T pw is the pulse width, T p is the period, T delayis the predetermined delay.

[0024] Trigger on rising edge T0, pulse width T pw Adding half of this precisely locks the timing to the peaks of the low voltage signal 72 which, as described above, are synchronized to the peaks of the AC power supply 12. The peaks of the AC power supply 12 occur at a phase angle of 90 degrees, or with a period P AC The period T of the pulse signal 82 p is the period P of the low voltage signal 12 LV Then, the period P of the AC power supply 12 is AC Therefore, the period T p By advancing by an additional 3 / 4 of the pw ) to the next rising zero crossing (phase angle of 0 degrees) of the AC power supply 12. AC Advance 3 / 4 of the way.

[0025] Equation 1 is a predetermined delay T delay The true zero crossing time (rising edge T0 minus pulse width T pw 1 / 2 + period T p The switch activation time T is equal to the difference between switch It can be seen that the predetermined delay T delay takes into account the inherent delays in the control system 11 due to analog processing in the front end 50, digital processing in the microprocessor 54, and / or actuation of the switching devices 42, 44, 46. The inventors have found that the delays associated with these functions are substantially deterministic, such that appropriate estimates of the delays can be empirically determined in the lab or factory and then hard-coded into the zero-crossing control module 562. Alternatively, the zero-crossing control module 562 may perform a self-learning function and learn in the field a predetermined delay T delay The microprocessor 54 can be configured to set a predetermined delay T delay Considering the switch activation time T switchWhen actuating the switching devices, the switching opening and closing is ensured to be synchronized with the zero crossings of the AC power source 12 (e.g., the phase shift between the switching time and the true zero crossing is repeatably less than ±35 degrees, less than ±30 degrees, less than ±25 degrees, less than ±20 degrees, less than ±15 degrees, less than ±5 degrees, less than ±4 degrees, or less than ±3 degrees). This prevents the switch actuation from always occurring at or near the peak voltage of the AC power source 12, thereby minimizing inrush current and arcing at the switch.

[0026] The pulse signal 82 is generated by three variables: (1) the frequency (period) of the AC power supply, (2) the amplitude (voltage) of the AC power supply, and (3) the voltage reference v of the comparator. ref ). Variables (1) and (2) vary with different types of AC power sources. The variance in variable (3) is an inherent result of manufacturing tolerances in low-cost circuit components. However, the zero-crossing module 562 is independent of variations in the frequency and amplitude of the AC power source 12, and furthermore, the voltage reference v of the comparator 52 ref It is independent of fluctuations in

[0027] Same voltage reference v ref Even if the pulse width T can be guaranteed in all cases, variations in frequency and voltage across different power standards will cause differences in the pulse signal 82. pw Adding 1 / 2 of this to the rising edge trigger time T0 reliably sets the peak of the AC mains waveform 12. However, even with this information, it is not possible to reliably determine the zero crossing without knowing the frequency of the AC mains 12. While it is proposed to hard-code the control based on the standard frequency of the AC mains 12 (e.g., 60 Hz in North America), this imposes unnecessary geographic constraints on the control system.

[0028] The period T of the pulse signal 82 p is the period of the AC power supply P AC Therefore, it is worth considering as a zero-crossing control input. However, the problem is that the pulse period T pThis involves measuring the time delay between the pulse trigger T0 initiating the pulse and the true zero crossing. Again, although a specific voltage and frequency can be calibrated, this introduces unnecessary geographical constraints. Furthermore, the pulse period T p The algorithm is strictly based on the voltage and frequency constraints, and the geographical constraints on the voltage and frequency are determined by the variable (3) (the voltage reference v ref ) is not properly considered. On paper, the voltage reference v ref can be assumed to be fixed at, for example, 0.3v. However, in reality there will be variations due to manufacturing tolerances, and this dispersion in trigger levels will result in dispersion in timing if not taken into account.

[0029] Pulse width T pw and period T p By combining the two, we take into account both variables (1) and (2) (frequency and amplitude of AC power source 12). pw and period T p The combination of variables (3), the reference voltage trigger level v ref The waveform of the AC power supply 12 is completely determined by the variables (1) and (2) and is not affected by the variance of the comparator 54 (variable (3)). ref Regardless of the pulse width T pw Advancing the rising edge of the pulse by half of T0 sets the 90 degree phase, i.e., peak voltage, of the AC power sine wave 12. Furthermore, the true voltage v ref Regardless of the square wave period T p is always the same, and the period P of the AC power supply 12 AC Therefore, the reference voltage of the comparator, v ref The variance of p , or when there is a peak voltage, the pulse width T pw This does not affect the accuracy of the proposition that 1 / 2 of corresponds to

[0030] Therefore, from any given rising edge T0 of pulse signal 82, the next zero crossing of AC power supply 12 occurs at pulse width T pw 1 / 2 and period T pFrom the first zero crossing, each subsequent zero crossing occurs after a period of T p In Equation 1, the inventors consider the predetermined delay T delay To allow enough time to subtract one period T p However, in other embodiments, the zero crossing function may have a period T p It is contemplated that the multiplier applied to can be any number equal to (1 / 4+n*1 / 2), where n is an integer.

[0031] By comparing Figures 3(a)-3(c) with Figures 4(a)-4(c), it can be seen that the zero-cross control performed by control system 11 is completely independent of the voltage and frequency of the AC power source. Figure 3(a) shows a standard North American 60Hz, 120V AC power source 12, while Figure 4(a) shows a standard European 50Hz, 220V AC power source 12'. Using the same analog front end 50, control system 11 is configured to generate appropriate low-voltage periodic signals 72, 72' for each type of AC power source 12, 12', each low-voltage signal 72, 72' being synchronized with the voltage peaks of each AC power source 12, 12' and the period P of each AC power source. AC , P AC’ Synchronized period P LV , P LV’ Using the comparator 52, the control system 11 detects the rising edges T0, T1 of the digital pulse signals 82, 82'. 0’ From this, each pulse width T pw , T pw’ The peak voltage (90 degrees phase) of each AC power supply 12, 12' is set by notifying 1 / 2 of p , T p’ The pulse width T is configured to notify 3 / 4 of the next rising zero crossing (0 degree phase) of each AC power supply 12, 12'. pw , T pw’ and period T p , T p’Therefore, regardless of the frequency and amplitude of the AC power supply, the controller 70 can obtain the effective switch actuation time T switch The method is configured to determine:

[0032] One exemplary method of using the device 10 of Figure 1 will now be briefly described. The device controller 40 executes the device control module 561 to operate the various power components of the device according to the device's purpose. Whenever the device control module 561 needs to activate the switching devices 42, 44, 46 to connect one of the power components to the AC power source 12, it uses the zero-crossing module 562 to synchronize the switch activation to the zero crossings of the AC power source. The analog front end 50 continuously processes the AC power source 12 and outputs a low-voltage periodic signal 72, and the comparator 52 compares the low-voltage periodic signal with a reference voltage v ref and outputs a digital pulse signal 82 indicative of the relationship between the low voltage periodic signal and the reference signal. pw and period T p The value of T is stored in memory 56 and / or periodically updated. When the equipment control module 561 requires activation of a switch device, the microprocessor 54 executing the zero crossing control module 562 stores the value of T in the memory 56 and / or periodically updates it. switch More specifically, the processor delays actuation of the switching devices 42, 44, 46 from the rising edge T0 of the digital pulse signal 82 to the switch actuation time T switch The controller 40 then activates the switching devices 42, 44, 46 and determines the switch activation time T switch, connects each power component 26, 32, 34 to the AC power source. This process ensures that each time the appliance controller 40 activates the switching devices 42, 44, 46, the switching devices open and close at approximately the zero crossings (e.g., switching occurs repeatably at less than ±45 degrees, less than ±30 degrees, less than ±15 degrees, less than ±15 degrees, less than ±5 degrees, less than ±4 degrees, less than ±3 degrees, and out of phase from the true zero crossings). [Example]

[0033] Referring to Figures 5A and 5B, an experiment was conducted to evaluate the effect of the zero-cross control module 562 on the inrush current to a DC fan motor. A 240V, 60Hz AC power supply was connected to a mechanical relay, which in turn was connected to a DC fan motor. The voltage and current to the fan motor were monitored when the mechanical relay was switched from open to closed to connect the DC fan motor to the AC power supply. Figure 5A shows data obtained when the instrument controller 40 and the zero-cross module 562 were used to control the mechanical relay. The upper line represents voltage, and the lower line represents inrush current. As can be seen, using the zero-cross control module 562, the relay closed at approximately 0V. As a result, the maximum inrush current was only 3.7A. In comparison, Figure 5B shows data obtained when zero-cross control was not used and the mechanical relay switched on the fan motor at approximately its peak voltage. The inrush current to the fan motor was significantly higher, at 23.3A.

[0034] Referring to Figures 6-9, further experiments were conducted to verify that the zero-cross control module is independent of the amplitude and frequency of the AC power supply. Figure 6 shows the results when an equipment controller 40 including a zero-cross control module 562 is used to close a mechanical relay and connect a load to a 120V and 50Hz AC power supply (top line). As shown, using the zero-cross control module 562, the relay is closed at approximately 0V, limiting the maximum inrush current to less than 1.5A. Figure 7 shows the results when an equipment controller 40 including a zero-cross control module 562 is used to close a mechanical relay and connect a load to a 240V and 60Hz AC power supply (top line). As shown, using the zero-cross control module 562, the relay is closed at approximately 0V, limiting the maximum inrush current to less than 3.5A. Figure 8 shows the results when an equipment controller 40 including a zero-cross control module 562 is used to close a mechanical relay and connect a load to a 240V and 50Hz AC power supply (top line). As shown, using the zero crossing control module 562, the relay closed at approximately 0V, limiting the maximum inrush current to less than 3A. Figure 9 shows the results when using an appliance controller 40 including the zero crossing control module 562 to close the mechanical relay and connect a load to a 120V and 60Hz AC power source (top line). As shown, using the zero crossing control module 562, the relay closed at approximately 0V, limiting the maximum inrush current to less than 1.5A. Thus, it can be seen that the zero-crossing control module 562 is independent of the amplitude and frequency of the AC power source (e.g., the zero-crossing control module is configured to limit inrush current to less than 10 A, less than 9 A, less than 8 A, less than 7 A, less than 6 A, less than 5 A, and / or less than 4 A over a range of AC power signals including at least (i) 240V, 60Hz AC power, (ii) 240V, 50Hz AC power, (iii) 120V, 50Hz AC power, and (vi) 120V, 60Hz AC power). Furthermore, the zero-crossing control module 562 can achieve this inrush current limiting without adjusting the zero-crossing control module's software or hardware for each type of AC power source.

[0035] Referring to FIG. 10, another experiment was conducted to test the effectiveness of the control system 11 and zero-crossing control module 562 in preventing relay damage. In this experiment, three identical relays were connected between a 60 Hz AC power source and a resistive load, with each relay controlled by a different controller. The controller connected to the first relay was specially programmed to repeatably switch the relay 2 ms after the AC power's zero-crossing (43-degree phase angle). As can be seen in the left bar labeled "Worst Case" in Figure XX, this relay failed (due to arc welding) after less than 100,000 cycles. The controller connected to the second relay was conventional and was used as the experimental control. Like all conventional relay control systems, the control was independent of the AC power's phase, and therefore the relay switched at random times relative to the AC power waveform. This relay failed (due to arc welding) after less than 300,000 cycles. A controller 40 implementing the zero-crossing control module 562 was connected to the third relay. As can be seen in the right bar of the graph (labeled "True Zero Crossing"), the relay did not fail after 1,000,000 cycles. The test was stopped after 1,000,000 cycles, and the relay was inspected. No signs of wear or damage were detected during the inspection. Additional tests were performed along these lines to determine the break-even point for 1.6 ms control (phase angle 35 degrees). Thus, it can be seen that the zero-crossing control module 562 increases the useful life of a mechanical relay by at least 100% (e.g., at least about 150%, at least about 200%, at least about 250%, at least about 300%, at least about 400%) when compared to the same type of mechanical relay used under the same conditions without the zero-crossing control module.

[0036] The "open" and "close" delay times of various relays (i.e., the time between sending a signal to the relay and when the relay opens or closes the circuit) are set to a fixed value T delayAdditional testing was performed to verify that the values ​​of T were consistent enough to be reliably used in Equation 1. For each type of relay, the switch was opened and closed a specified number of times, and the opening and closing time for each actuation was measured. Testing revealed that the standard deviation of the opening and closing delays for some models of mechanical relays was less than 500 microseconds, about less than 100 microseconds, resulting in opening and closing times of T delay is sufficiently deterministic for Equation 1 to be valid based on a given value for .

[0037] Embodiments of the present disclosure may include a special purpose computer that includes various computer hardware, as described in more detail herein.

[0038] For purposes of illustration, programs and other executable program components may be illustrated as discrete blocks, however, it will be appreciated that such programs and components reside at various times in different storage components of the computing device, and are executed by the device's data processor(s).

[0039] Although described in connection with an exemplary computing system environment, embodiments of aspects of the present invention are operational with other specialized computing system environments or configurations. The computing system environment is not intended to suggest any limitation as to the scope of use or functionality of any aspects of the present invention. Moreover, the computing system environment should not be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary operating environment. Examples of computing systems, environments, and / or configurations that may be suitable for use with aspects of the present invention include, but are not limited to, personal computers, server computers, handheld or laptop devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics, mobile phones, network personal computers, minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like.

[0040] Embodiments of aspects of the disclosure may be described in the general context of data and / or processor-executable instructions (e.g., program modules) stored on one or more tangible, non-transitory storage media and executed by one or more processors or other devices. Generally, program modules include, but are not limited to, routines, programs, objects, components, and data structures that perform particular tasks or implement particular abstract data types. Aspects of the disclosure may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote storage media, including memory storage devices.

[0041] In operation, the processor, computer, and / or server may execute processor-executable instructions (e.g., software, firmware, and / or hardware) such as those illustrated herein to implement aspects of the present disclosure.

[0042] Embodiments may be implemented with processor-executable instructions. The processor-executable instructions may be organized into one or more processor-executable components or modules on a tangible, processor-readable storage medium. Furthermore, embodiments may be implemented with any number and organization of such components or modules. For example, aspects of the present disclosure are not limited to the specific processor-executable instructions or the specific components or modules illustrated in the figures and described herein. Other embodiments may include processor-executable instructions or components having more or less different functionality than those illustrated and described herein.

[0043] The order of execution or performance of acts in accordance with the aspects of the present disclosure illustrated and described herein is not critical unless otherwise specified. That is, unless otherwise specified, acts may be performed in any order, and embodiments may include more or fewer acts than those disclosed herein. For example, it is contemplated that performing or implementing a particular act before, contemporaneously with, or after another act is within the scope of the invention.

[0044] When introducing elements of the invention or embodiments of the invention, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0045] Not all of the illustrated components illustrated or described may be required. Furthermore, some implementations and embodiments may include additional components. Changes in the arrangement and type of components may be made without departing from the spirit or scope of the claims as set forth herein. More, different, or fewer components may be provided, or components may be combined. Alternatively, or in addition, a component may be implemented by several components.

[0046] The foregoing specification presents embodiments by way of example, not limitation. This specification describes several embodiments, adaptations, variations, alternatives, and uses of aspects of the present invention, including what is currently contemplated as the best mode for carrying out aspects of the present invention, enabling those skilled in the art to make and use aspects of the present invention. Furthermore, aspects of the present invention are not limited to the details of construction and the arrangement of components set forth in the following specification or illustrated in the drawings. Aspects of the present invention are capable of other embodiments and of being practiced or carried out in various ways. Moreover, the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting.

[0047] It will be apparent that modifications and variations can be made without departing from the scope of the invention as set forth in the appended claims. Because various changes can be made in the structure and methods described above without departing from the scope of the invention, it is intended that all matter contained in the above specification and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

[0048] In view of the above, it will be seen that the several advantages of the inventive aspects are achieved and other advantageous results attained.

[0049] The Abstract and Overview are provided to assist the reader in quickly ascertaining the nature of the technical disclosure. The Abstract and Overview are presented with the understanding that they will not be used to interpret or limit the scope or meaning of the claims. The Overview is provided to introduce in a simplified form a selection of concepts that are further described in the Detailed Description. The Overview is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the nature of the claimed subject matter. [Explanation of symbols]

[0050] 10 equipment 11 Control System 12 AC power supply 20 Case 22 Cooling System 24 Heat absorption heat exchanger 26 Compressor 28 Heat rejection heat exchanger 32 Evaporator fan 34 Condenser fan 36 DC motor 38 AC / DC conversion circuit 40 Controller 42, 44, 46 Switching devices 48 Temperature Sensor 49 Door Sensor 50 Analog Front End 52 Comparator 54 processors 56 memory 561 Equipment Control Module 562 Zero Cross Control Module L load

Claims

1. The housing and a compression-driven refrigeration system for cooling a load within the enclosure, the compression-driven refrigeration system including a refrigeration circuit filled with a refrigerant, the refrigeration circuit including a heat absorption heat exchanger in thermal communication with the load, a heat rejection heat exchanger thermally isolated from the load, and a compressor circulating the refrigerant between the heat absorption heat exchanger and the heat rejection heat exchanger; a fan configured to move air across one of the heat absorption heat exchanger and the heat rejection heat exchanger; a switching device operable to selectively connect a component selected from the group of components consisting of the compressor and the fan to an AC power source having periodic zero crossings where the voltage of the AC power source is zero; an appliance controller operably connected to the switching device to selectively operate the switching device connecting the one component to the AC power source, the appliance controller including a processor and a memory storing processor-executable instructions that, when executed by the processor, configure the processor to execute a zero-crossing control module that synchronizes operation of the switching device to zero crossings of the AC power source, the zero-crossing control module being independent of the amplitude and frequency of the AC power source; Including cooling equipment.

2. 10. The cooling equipment of claim 1, wherein the equipment controller further includes an analog front end operably connected to the AC power source, the analog front end configured to process the AC power source and output a low-voltage periodic signal synchronized to the AC power source.

3. 3. The cooling appliance of claim 2, wherein the appliance controller further includes a comparator operatively connected to the analog front end and the processor, the comparator configured to compare the low-voltage periodic signal with a reference voltage and output a digital pulse signal to the processor indicative of a relationship between the low-voltage periodic signal and the reference voltage.

4. 4. The cooling device of claim 3, wherein the digital pulse signal has a pulse width and a period, and the zero-crossing control module is configured to determine the pulse width and the period and to determine a switch activation time as a function of the pulse width and the period.

5. 5. The cooling equipment of claim 4, wherein the zero-crossing control module is configured to determine a switch actuation time as a function of a predetermined delay associated with one or more of the analog front end, the processor executing the processor-executable instructions, and actuation of the switching device.

6. The cooling device of claim 5 , wherein the zero-crossing control module is configured to determine the switch activation time according to the following function: T ｓｗｉｔｃｈ =1 / 2*T ｐｗ +3 / 4*T ｐ -T ｄｅｌａｙ (however, T ｓｗｉｔｃｈ is the switch actuation time, T ｐｗ is the pulse width, T ｐ is the period, T ｄｅｌａｙ is the predetermined delay)

7. The cooling device of claim 2 , wherein the analog front end includes a voltage divider.

8. The cooling device of claim 2 , wherein the analog front end includes a capacitive filter configured to remove high frequency noise.

9. The cooling device of claim 2 , wherein the analog front end includes a diode configured to convert the low voltage periodic signal into a rectified half wave of the AC power source.

10. 2. The cooling equipment of claim 1, wherein the switching device is a mechanical relay, and the zero-crossing control module increases the useful life of the mechanical relay by at least 100% when compared to a mechanical relay of the same type used under the same conditions without the zero-crossing control module.

11. 2. The cooling equipment of claim 1, wherein the switching device is a normally open mechanical relay, and the zero-crossing control module is configured to repeatably synchronize closures of the mechanical relay to zero crossings of the AC power source such that each closure of the mechanical relay is out of phase with each zero crossing by less than 35 degrees.

12. The housing and a temperature control device for controlling the temperature of a load within the enclosure; a direct current fan for moving air for one of: (i) distributing air within the enclosure; or (ii) exchanging heat between the temperature control device and an ambient environment; a switching device operable to selectively connect the DC fan to an AC power source having periodic zero crossings where the voltage of the AC power source is zero; an appliance controller operatively connected to the switching device for selectively operating the switching device connecting the DC fan to the AC power source, the controller including a processor and a memory storing processor-executable instructions that, when executed by the processor, configure the processor to execute a zero-crossing control module that synchronizes operation of the switching device with zero crossings of the AC power source to minimize inrush current to the DC fan; temperature control equipment, including

13. 13. The temperature control apparatus of claim 12, wherein the DC fan includes a DC motor and AC / DC conversion circuitry connected between the switching device and the DC motor.

14. The temperature control device of claim 12 , wherein the zero-crossing control module is independent of the frequency and amplitude of the AC power source.

15. 13. The temperature control instrument of claim 12, wherein the instrument controller further includes an analog front end operably connected to the AC power source, the analog front end configured to process the AC power source and output a low-voltage periodic signal synchronized to the AC power source.

16. 16. The cooling appliance of claim 15, wherein the appliance controller further includes a comparator operatively connected to the analog front end, the comparator configured to compare the low-voltage periodic signal with a reference voltage and output a digital pulse signal to the processor indicative of a relationship between the low-voltage periodic signal and the reference voltage.

17. 17. The temperature control device of claim 16, wherein the digital pulse signal has a pulse width and a period, and the zero-crossing control module is configured to determine the pulse width and the period and to determine a switch actuation time as a function of the pulse width and the period.

18. 18. The temperature control apparatus of claim 17, wherein the zero-crossing control module is configured to determine a switch actuation time as a function of a predetermined delay associated with one or more of the analog front end, the processor executing the processor-executable instructions, and the actuation of the switching device.

19. 20. The temperature control device of claim 18, wherein the zero-crossing control module is configured to determine switch actuation times according to the following function: T ｓｗｉｔｃｈ =1 / 2*T ｐｗ +3 / 4*T ｐ -T ｄｅｌａｙ (however, T ｓｗｉｔｃｈ is the switch actuation time, T ｐｗ is the pulse width, T ｐ is the period, T ｄｅｌａｙ is the predetermined delay)

20. 1. A method of operating a temperature control device, comprising: using circuitry to process an AC power source and output a low voltage periodic signal synchronized to said AC power source; using a comparator to compare the low voltage periodic signal with a reference voltage and output a digital pulse signal indicative of a relationship between the low voltage periodic signal and the reference voltage, the digital pulse signal having a pulse width and a period; determining the pulse width and the period using a processor in a controller of the temperature control device; using the processor to determine switch actuation times as a function of the pulse width and the period; using the controller to activate a switching device of the temperature control device to connect a power component of the temperature control device to the AC power source at the switch activation time, wherein a phase shift between switching and a true zero crossing of the AC power source is less than ±35 degrees; A method comprising:

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