Isolated power converter for a thermodynamic system

Abstract

The present invention relates to a power converter system that provides adjustable power to a heater and includes an input rectifier and a full-bridge isolated converter. The input rectifier is configured to rectify a line power having a line energy. The full-bridge isolated converter is configured to generate an isolated output voltage based on the rectified line power. The isolated output voltage is electrically isolated from the line energy.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit and priority of U.S. Application No. 16 / 868,230, filed May 6, 2020. The disclosure of the aforementioned application is incorporated herein by reference. Technical Field

[0003] This invention relates to a power device for a thermal system. Background Technology

[0004] The content in this section provides only background information related to this invention and does not constitute prior art.

[0005] Electric heaters operable to heat loads within a defined temperature range are typically powered by a power control device that provides adjustable power to the heater. Some power controls employ phase angle control (i.e., phase-triggered control) to limit power from the source by modulating a power switch (e.g., a semiconductor thyristor or a triac switch) at a predetermined phase. In another example, the power control device may be a variable DC power supply that converts alternating current (AC) to DC. While specific examples have been provided, other power control devices are also possible.

[0006] The aforementioned power control device exhibits poor harmonics and a lower power factor, requiring additional components to compensate for the power factor. Furthermore, for phase angle control, limiting the heater voltage becomes difficult when the power setpoint is above 50%. Moreover, the variable DC power supply requires numerous electronic components (e.g., large-capacity capacitors, electromagnetic interference (EMI) filters, high-frequency transformers, compound rectifiers, and / or DC / DC converters), all of which increase the complexity and size of the device.

[0007] This invention solves these and other problems related to providing adjustable and controllable power to the heater. Summary of the Invention

[0008] This section provides an overview of the invention and is not a complete disclosure of its full scope or all its features.

[0009] This invention relates to a power converter system for providing adjustable power to a heater. The power converter system includes: an input rectifier configured to rectify a line power supply having line energy; and a full-bridge isolation converter configured to generate an isolated output voltage based on the rectified line power supply. The isolated output voltage is electrically isolated from the line energy.

[0010] In one aspect, the full-bridge isolated converter further includes a full-bridge rectifier, a transformer electrically coupled to the full-bridge rectifier, wherein the transformer is configured to generate an isolated full-wave voltage, and an output rectifier configured to rectify the isolated full-wave voltage to generate an isolated output voltage.

[0011] In another variation of the other aspect, the full-bridge rectifier includes a first pair of electronic switches and a second pair of electronic switches to drive the transformer with the rectified line power. In another variation, the power converter system includes a power controller configured to operate the full-bridge rectifier to generate the isolated output voltage.

[0012] In another aspect, the power controller is configured to perform a variable frequency control to generate the output voltage less than or equal to the voltage-limited power setpoint as the isolated output voltage.

[0013] In yet another aspect, the power converter system further includes a bridge sensor configured to detect a current through a primary winding of the transformer to detect a flux walk.

[0014] In one aspect, the power converter system includes a filter configured to filter the isolated output voltage to output a desired output voltage.

[0015] In another aspect, the input rectifier is configured to receive one of a single-phase alternating current (AC) or a direct current (DC) as the line power.

[0016] In one aspect, the present disclosure relates to a control system including the power converter system described herein and a main system controller configured to determine a desired output voltage and control the power converter system to generate the desired output voltage.

[0017] In one aspect, the present disclosure relates to a method of converting power to operate a load powered by a line power having a line energy. The method includes rectifying the line power, switchably driving a transformer with the rectified line power to generate an adjustable electrically isolated full-wave voltage, and rectifying the electrically isolated full-wave voltage to obtain an isolated output voltage indicative of a desired output voltage applied to the load, wherein a current in phase with the isolated output voltage is extracted from the line power.

[0018] In another aspect, the method further includes filtering the isolated output voltage to obtain the desired output voltage.

[0019] In yet another aspect, the method further includes performing variable frequency control to drive the transformer at a lower switching frequency than a switching frequency when the required output voltage is greater than the voltage-limited power setpoint when the required output voltage is less than the voltage-limited power setpoint.

[0020] In one aspect, the method further includes detecting a current through the transformer primary winding and performing a corrective action when the current is greater than a magnetizing current threshold.

[0021] In another aspect, the method further includes detecting an applied voltage, wherein the applied voltage is at least one of a line power or a rectified line power, and performing a corrective action when the applied voltage exceeds a predetermined voltage range.

[0022] In yet another aspect, the line power is one of a single-phase alternating current (AC) or a direct current (DC).

[0023] In one aspect, the switchably driving the transformer further includes alternatingly driving the first pair of electronic switches and the second pair of electronic switches. The first pair of electronic switches and the second pair of electronic switches form a full-bridge rectifier.

[0024] In one aspect, the present disclosure is directed to a power converter system for providing a required output voltage to a heater. The power converter system includes an input rectifier configured to rectify a line power having a line energy; a transformer configured to generate an isolated full-wave voltage; a full-bridge rectifier electrically coupled to the transformer and operable to drive the transformer to generate the isolated full-wave voltage based on the rectified line power; an output rectifier configured to rectify the isolated full-wave voltage to generate an isolated output voltage indicative of the required output voltage; a bridge sensor configured to measure a bridge current flowing through the transformer; and a power controller configured to operate the full-bridge rectifier to drive the transformer.

[0025] In another aspect, the power controller is configured to determine a magnetizing walk state in response to the bridge current being greater than or equal to a magnetizing current threshold, and the power controller is configured to perform a corrective action in response to the magnetizing walk state.

[0026] In yet another aspect, the power converter system further includes a filter configured to filter the isolated output voltage to output the required output voltage.

[0027] In another aspect, the input rectifier is configured to receive one of a single-phase alternating current (AC) or a direct current (DC) as the line power.

[0028] Other suitable aspects will become apparent to those of ordinary skill in the art from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0029] For a better understanding of the present application, various modes thereof will now be described in exemplary fashion by reference to the attached drawings. In the drawings:

[0030] Figure 1 is a block diagram of a hydronic system according to the present application, including a heater and a control system having isolated power converters;

[0031] Figure 2 is a block diagram of an isolated power converter according to the present application; Figure 1

[0032] Figure 3 is an exemplary circuit diagram of an isolated power converter according to the present application;

[0033] Figure 4 is a graph comparing the output voltage of an isolated power converter with and without variable frequency control at a low power set point according to the present application;

[0034] Figure 5 is a graph showing variable frequency control of an isolated power converter according to the present application; and

[0035] Figure 6 is a block diagram of a hydronic system having multiple isolated power converters according to the present application.

[0036] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present application in any way. DETAILED DESCRIPTION

[0037] The following description is merely exemplary in nature and is not intended to limit the present application, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0038] A hydronic system can include a heater having one or more heating elements and a control system including a controller and a power converter system (i.e., power control device) to independently control the power applied to the heating elements of the heater. In one mode, the power converter system includes step-down converters that are operable by the controller to generate a desired output voltage to the heating elements of the heater.

[0039] ​In another aspect, the control system includes a power converter system that provides an isolation barrier between a power source and one or more power converters to isolate the heater from the power source. More specifically, the present disclosure describes a power converter system that includes an isolation circuit, which can be referred to as an isolated power converter, that isolates and converts line power from a power source to a desired adjustable output voltage that can be applied to a load (e.g., a heater). The isolated power converter includes a full-bridge isolated converter having high switching rate electronic switches and a transformer for isolating and converting the line power to the desired voltage. The isolated power converter reduces or suppresses power losses during conversion and eliminates or reduces the use of large capacity capacitors (i.e., DC side capacitors). As a result, the isolated power converter is smaller than, for example, a variable DC power supply.

[0040] Referring to Figure 1 A thermal system 100 configured in accordance with the present disclosure includes a heater 102 and a control system 104 for operating the heater 102. The control system 104 is configured to provide an isolated adjustable power output to the heater 102 based on, for example, power set points, temperature set points, and / or feedback data from the heater 102, among other variables. In one aspect, the control system 104 includes a master system controller 106 for determining the amount of power to be applied to the heater 102 and a power converter system 108 that is operable by the master system controller 106 for generating an isolated power output. In the figures, dashed arrows represent data and / or control signals (e.g., 0V to 5V), while solid lines represent power lines.

[0041] The heater 102 is operable to heat a load (e.g., but not limited to, a wafer as part of a semiconductor processing chamber, a gaseous fluid flowing in a channel / duct, and / or a liquid disposed in a container). In one aspect, the heater 102 includes a resistive heating element 110 that generates heat when power is supplied to the resistive heating element 110. Although one resistive heating element is provided, the heater 102 can include more than one resistive heating element.

[0042] In one application, in addition to generating heat, the resistive heating element 110 can also act as a sensor for measuring the average temperature of the resistive heating element 110 based on the electrical resistance of the resistive heating element 110. More specifically, such resistive heating elements typically have a non-linear resistance temperature coefficient and define a "two-wire" heater system. Such two-wire systems are disclosed in U.S. Patent No. 7,196,295, which is commonly owned with the present application and is incorporated herein by reference in its entirety. In a two-wire system, the thermodynamic system is an adaptive thermodynamic system that combines the heater design with controls that combine power, resistance, voltage, and current in a customizable feedback control system that defines one or more of these parameters (i.e., power, resistance, voltage, and current) while controlling another. The control system 104 is configured to monitor at least one of the current, voltage, and power delivered to the resistive heating element to determine the resistance, and thus the temperature of the resistive heating element 110.

[0043] In another exemplary application, the heater 102 is configured to include a temperature sensing power pin for measuring the temperature of the heater 102. Utilizing a power pin as a thermocouple to measure the temperature of a resistive heating element is disclosed in Applicant's co-pending U.S. Application No. 14 / 725,537, filed May 29, 2015, entitled "Resistive Heater with Temperature Sensing Power Pin," which is commonly owned with the present application and is incorporated herein by reference in its entirety. Typically, the resistive heating element and control system of a heater are connected by a first power pin and a second power pin that define a first junction and a second junction, respectively. The first and second power pins act as thermocouple sensing pins for measuring the temperature of the resistive heating element of the heater 102. The control system 104 in communication with the first and second power pins is configured to measure voltage changes at the first and second junctions. More specifically, the control system 104 measures millivolt (mV) changes at the junctions, which are then utilized to calculate the average temperature of the resistive heating element 110. In one approach, the control system 104 can measure the voltage changes at the junctions without interrupting the power to the resistive heating element.

[0044] Although specific examples and operational functions are described, the heater 102 can be other suitable types of heaters that are operable to generate varying temperatures based on the power being received. In addition, in addition to or as an alternative to a "two-wire" type heater or temperature sensing power pin, the heater 102 can include a separate temperature sensor (e.g., a thermocouple or a resistance temperature detector (RTD) sensor, etc.) for measuring the temperature of the heater 102 that is provided to the control system 104 as part of a closed loop control.

[0045] The control system 104 is configured to control the power applied to the heater 102, and thus the thermal performance of the heater 102, based on operating set points, feedback data from the heater 102, and / or predefined control programs / algorithms, as well as other inputs and / or control schemes. More specifically, in one approach, the main system controller 106 determines the output voltage required by the heater 102, and the power inverter system 108 converts the input voltage from the power source 112 (i.e., line power) to the required output voltage. In one approach, the required output voltage can be a value between 0 V and a maximum voltage equal to or greater than the line voltage (e.g., the maximum voltage is equal to the line voltage, 10% greater than the line voltage, or equal to other suitable values based on system standards).

[0046] Based on the application and type of the heater 102, the main system controller 106 can be configured in various suitable ways. For example, in one approach, the main system controller 106 is a closed loop system that acquires feedback data from the heater 102 and / or sensors (not shown) equipped with the heater 102 to monitor performance characteristics of the heater 102 (e.g., but not limited to: applied voltage, current, resistance, power, and / or temperature). Based on the performance characteristics and defined control schemes, the main system controller 106 determines the required output voltage and corresponding control signals to be transmitted to the power inverter system 108 for generating the required output voltage. In addition to the feedback data regarding the performance characteristics of the heater 102, the main system controller 106 can receive other data indicative of the operation of the thermodynamic system 100, which can be used to control the power applied to the heater 102. For example, data indicative of the power from the power source 112 can be monitored to detect power drops or spikes.

[0047] In one approach, the main system controller 106 employs a state mode control in which the main system controller 106 determines the operating state of the heater 102 based on one or more input parameters (e.g., temperature, resistance, current, and / or voltage). The operating states of the heater 102 include: an idle mode in which no power is supplied to the heater 102; a start-up mode in which low power is provided to measure voltage and current; a soft start mode in which power is increased at a low ramp rate until a particular resistance set point is exceeded; a rate mode in which temperature is increased at a ramp rate selected based on the heater's material selection; and a hold mode in which the temperature of the heater 102 is controlled at a particular set point using, for example, a continuous proportional-integral-derivative controller (PID control). These operating states are merely exemplary and other modes can be included within the scope of the present disclosure.

[0048] Based on the operating mode of the heater 102, the main system controller 106 independently controls the heating elements by adjusting the input voltage applied to the heating elements from the corresponding isolated power converter. The main system controller 106 can be configured in various ways to adjust the input voltage, including but not limited to: (1) modifying PID parameters according to operating states; (2) changing from automatic mode (no user input) to manual mode (user input received by the controller) or changing from manual mode to automatic mode; (3) setting a manual percentage power; (4) initiating a setpoint ramp; (5) modifying the integral (hold) of the PID control by modifying the integral by offsetting, scaling, and / or modifying based on temperature; and (6) changing the voltage when entering a new operating state. The logic of the main system controller 106 for adjusting the voltage can be triggered in various suitable ways, including but not limited to: (1) detecting a start-up; (2) a process temperature approaching a setpoint; (3) a process temperature deviating from a setpoint; (4) a change in setpoint; (5) exceeding a process temperature; (6) falling below a process temperature; (7) a predetermined period of time expiring; (8) reaching a general system reading (e.g., current, voltage, wattage, resistance, and / or power percentage). The hydronic system includes a plurality of states, where each state has unique settings to create a programmable state machine that provides optimal performance in a dynamic system. Each state can define the next state to enter when conditions are met.

[0049] The main system controller 106 can also be configured to perform other operations, such as, but not limited to: cold ping control for providing a small signal level (e.g., 5V) to the heater 102 to determine a characteristic (e.g., temperature) of the hydronic system; reporting voltage, current, resistance, and / or wattage through a graphical user interface; calibration control for learning characteristics such as heater-load temperature correlation; diagnostics for monitoring the health and / or status of the heater 102; and / or system protection monitoring.

[0050] More specifically, in one aspect, the main system controller 106 is configured to monitor abnormal activity of the hydronic system 100 that can damage the heater 102 and / or the control system 104. In one aspect, the main system controller 106 implements at least one of the following protection schemes: inter-zone monitoring; inter-zone-reference monitoring; rate-of-change estimation; and / or energy limit control.

[0051] Inter-zone monitoring and zone-to-baseline monitoring are examples of consistency controls to assess whether the thermodynamic system 100 is maintaining the desired balance along the heater 102 and to minimize or inhibit damage to the heater 102 (e.g., ceramic cracking). For example, for inter-zone monitoring, the master system controller 106 determines the temperature of a heating zone 114 based on input parameters and determines whether the temperature difference between adjacent zones exceeds a temperature variation threshold (e.g., 10°C difference). If the temperature difference between adjacent zones exceeds the temperature variation threshold, the master system controller 106 executes a protective measure to reduce or inhibit damage to the thermodynamic system 100.

[0052] Zone-to-baseline monitoring compares the average temperature of the heater 102 to a baseline temperature to determine whether the temperature difference between the two exceeds a temperature variation threshold, which can be the same or different from the temperature variation threshold used for inter-zone monitoring. Thus, consistency controls can prevent the thermodynamic system 100 from exceeding the variation threshold by, for example, adjusting the power applied to the heater 102 or shutting down the system.

[0053] Another indicator of abnormal operation of the thermodynamic system 100 is the rate at which the heater 102 heats based on the applied power. In particular, in one approach, the heater temperature and / or the rate at which the electrical response of the heater 102 changes based on the applied power is compared to a relevant rate range threshold to determine whether the heater 102 is responding within specification. For example, if the heater temperature does not rise when the applied power is increased, or if the heater temperature suddenly rises when the applied power is unchanged or slightly increased, the master system controller 106 flags this activity as abnormal and executes a protective measure. Similarly, energy limit controls set limits on the amount of power that can be applied to the heater 102, and the master system controller 106 outputs a protective measure if the thermodynamic system 100 exceeds and / or approaches these limits. For example, energy limit controls are used to set a maximum current during low resistance start-up and a maximum power delivered. The maximums can be set by a user or pre-determined based on, for example, the specifications of the heater 102, and can vary over a temperature range.

[0054] The protective measures executed by the master system controller 106 include, but are not limited to, reducing the power applied to one or more heating zones 114 to control the variation, shutting off power to the heater 102, and / or outputting a message to a computing device about a significant temperature variation.

[0055] In one approach, the power converter system 108 includes an isolated power converter 114, which is a step-down converter used to generate an isolated desired output voltage. See Figure 2In one aspect, the isolated power converter 114 includes a power conversion portion 202 for converting an input voltage to a desired output voltage determined by the main system controller 106 and a control portion 204 for controlling the power conversion portion 202 to generate the desired output voltage.

[0056] In one aspect, the power conversion portion 202 includes a rectifier 206, a full-bridge isolated converter 208, and a filter 210. The rectifier 206 is configured to receive the input voltage (i.e., line power) from the power source 112 and generate a rectified voltage signal (i.e., rectified line power) that flows in one direction. For example, where the input voltage is a single-phase AC power signal, the rectifier 206 outputs a rectified AC signal that is provided in one direction. The input voltage can also be a direct current (DC) voltage signal and is not limited to AC power signals. The rectifier 206 can be an active or passive rectifier.

[0057] Based on the rectified voltage signal, the full-bridge isolated converter 208 generates an isolated output voltage signal indicative of the desired output voltage. As described herein, the full-bridge isolated converter 208 includes a plurality of electronic switches that can be operated by the control portion 204 to regulate the received voltage to the desired output voltage. The filter 210 smooths the isolated output voltage signal to output the desired output voltage to the heater 102.

[0058] The control portion 204 is configured to monitor the performance of the power conversion portion 202 and communicate with the main system controller 106. In one aspect, the control portion 204 includes a power source sensor 212, a rectified power sensor 214, a bridge sensor 216, and a power controller 218 in communication with the sensors 212, 214, and 216. The power source sensor 212 and the rectified power sensor 214 detect voltage levels from the input voltage from the power source sensor 212 and the rectified voltage from the rectifier 206 (i.e., rectified line power), respectively. In one aspect, the power source sensor 212 and the rectified power sensor 214 are voltage sensors and include the necessary circuitry to measure the voltage from the power source 112 and the rectifier 206, respectively. Although the control portion 204 is provided to include both the power source sensor 212 and the rectified power sensor 214, the control portion 204 can include only one of the power source sensor 212 or the rectified power sensor 214.

[0059] The bridge sensor 216 is configured to measure the bridge current through the full-bridge isolated converter 208 to monitor the inductor flux walk condition of the full-bridge isolated converter 208. In one aspect, the bridge sensor 216 is a current sensor and includes the necessary circuitry to measure the current at the full-bridge isolated converter 208, as further described herein.

[0060] The power controller 218 is communicatively coupled to the main system controller 106 and is configured to control the operation of the full-bridge isolated converter 208 to generate a voltage signal indicative of a desired output voltage. Further, based on data from the power supply sensor 212 and / or the rectified power sensor 214, the power controller 218 is configured to monitor the voltage provided to the full-bridge isolated converter 208 to detect abnormal voltage levels. In particular, if the voltage level surges above or drops below a predetermined threshold, the power controller 218 stops the operation of the full-bridge isolated converter 208 to prevent or suppress a power surge / drop at the heater 102. For example, the power supply sensor 212 and / or the rectified power sensor 214 detects the applied voltage (e.g., line power or rectified line power) into the full-bridge isolated converter 208, and the power controller 218 is configured to perform a corrective action when the applied voltage exceeds a predetermined voltage range. In one approach, during such abnormal power activity, the power controller 218 is also configured to notify the main system controller 106 of such abnormal activity and / or to shut off the power to the heater 102 as the corrective action.

[0061] Referring to Figure 3 , an example circuit diagram of the power conversion portion 300 with the power controller 218 for the isolated power converter 114 is provided. The power conversion portion 300 can be provided as the power conversion portion 202. For brevity, Figure 3 other components (e.g., the sensors 212, 214, and 216) shown with the isolated power converter 114 are not shown in

[0062] The power conversion portion 300 includes a rectifier 304, a full-bridge isolated converter 306, and a filter 308. The rectifier 304, the full-bridge isolated converter 306, and the filter 308 can be provided as the rectifier 206, the full-bridge isolated converter 208, and the filter 210, respectively. The rectifier 304 is a passive rectifier with four diodes 310-1 to 310-4 (collectively referred to as “diodes 310”). As an alternative to the diodes 310, the rectifier 304 can be an active rectifier with switches (e.g., field effect transistors (FETs) or bipolar junction transistors (BJTs)) that can be operated by the power controller 218. In one approach, the filter 308 includes an inductor 311 that smooths the voltage signal from the full-bridge isolated converter 306 and outputs a desired output voltage signal to the heater 102. The filter 308 can be other suitable filters (e.g., a capacitor-inductor filter) and is not limited to the inductor 311.

[0063] The full-bridge isolated converter 306 is configured to generate an isolated voltage signal (i.e., an isolated output voltage) that represents the desired output voltage to be applied to the heater 102. In one aspect, the full-bridge isolated converter 306 includes a full-bridge rectifier 312, a transformer 314, and an output rectifier 316. The full-bridge rectifier 312 is electrically coupled to the rectifier 304 and is operable to drive the transformer 314 with the rectified voltage signal (i.e., the rectified line power supply). In one aspect, the full-bridge rectifier 312 includes a first pair of electronic switches formed by SW1 and SW4, a second pair of electronic switches formed by SW2 and SW3, and switch drivers SD1, SD2, SD3, and SD4 for driving the switches SW1, SW2, SW3, and SW4, respectively. In one aspect, the switches SW1, SW2, SW3, and SW4 can be field effect transistors (FETs) or bipolar junction transistors (BJTs), and the switch drivers SD1, SD2, SD3, and SD4 are electronic components for operating these transistors. Each of the switch drivers SD1, SD2, SD3, and SD4 is electrically coupled to the power controller 218 and can be operated by the power controller 218 to open and close the electronic switches SW1, SW2, SW3, and SW4. Hereinafter, the switches SW1, SW2, SW3, and SW4 can be collectively referred to as switches SW1-SW4, and the switch drivers SD1, SD2, SD3, and SD4 can be collectively referred to as switch drivers SD1-SD4.

[0064] The transformer 314 is disposed between the full-bridge rectifier 312 and the output rectifier 316 to provide galvanic isolation between the power supply 112 and the heater 102. Here, a primary winding 314A of the transformer 314 is coupled to the full-bridge rectifier 312, and a secondary winding 314B of the transformer 314 is coupled to the output rectifier 316. The transformer 314 is configured to have a turns ratio of 1:1, but can have a turns ratio of 1:X, where X is greater than 1 (e.g., a turns ratio of 1:1.2) to increase the voltage of the isolated voltage signal.

[0065] In one aspect, the output rectifier 316 is a passive rectifier having four diodes 318-1 through 318-4 (collectively referred to as "diodes 318"). The output rectifier 316 rectifies the isolated full-wave voltage from the transformer 314 to generate a rectified isolated voltage, which can also be referred to as an isolated output voltage, and represents the desired output voltage. Like the rectifier 304, the output rectifier 316 can be an active rectifier that is controllable by the power controller 218, instead of a passive rectifier.

[0066] The power controller 218 is configured to operate the full-bridge rectifier 312 to generate a required output voltage based on the power command from the main system controller 106, which represents the magnitude of power to be provided to the heater 102 (e.g., 80% of the input voltage, 75% of the input voltage, etc.). Based on the power command, the power controller 218 determines the duty cycle for operating the switches SW1-SW4. The power controller 218 operates the first pair of switches SW1, SW4 simultaneously and the second pair of switches SW2, SW3 simultaneously to drive the transformer 314 in different directions. That is, with the switches SW1, SW4 closed and the switches SW2, SW3 open, the rectified power is applied to the transformer 314 such that current flows through the primary winding 314A in a first direction. With the switches SW1, SW4 open and the switches SW2, SW3 closed, the rectified power is applied to the transformer 314 such that current flows through the primary winding 314A in a second direction opposite the first direction. The magnitude of the generated voltage depends not only on the turns ratio of the transformer 314, but also on the rate at which the switches SW1-SW4 are actuated. That is, assuming a turns ratio of 1:1 for the transformer, if the switches are at 100% duty cycle, the required output voltage will be the same or substantially the same as the input voltage, and less than 100% duty cycle provides a required output voltage that is less than the input voltage. It will be appreciated by those skilled in the art that if the transformer 314 is configured as a step-up transformer, the output voltage at, for example, 100% duty cycle can be greater than the input voltage.

[0067] With continued reference to Figure 3To illustrate the power conversion operation of the isolated power converter, the power conversion portion 300 receives a single phase AC signal 320. The rectifier 304 generates a rectified AC signal 322, which is received by the full-bridge isolated converter 306. Based on the power command from the main system controller 106, the power controller 218 determines the duty cycles of the switches SW1-SW4 and operates the switches SW1-SW4. Accordingly, the full-bridge rectifier 312 is operated to drive the transformer 314 in different directions to generate an isolated full-wave voltage signal 324. The isolated full-wave voltage signal 324 is defined by a plurality of pulse signals that indicate the rectified AC signal 322 applied to the transformer 314 by activating and deactivating the first pair of switches SW1 and SW4 and the second pair of switches SW2 and SW3. The output rectifier 316 rectifies the isolated full-wave voltage signal 324 to provide a rectified isolated voltage signal 326 that represents the desired output voltage. The filter 308 smooths the rectified isolated voltage signal 326 to provide an output voltage signal 328 as the desired output voltage that is applied to the heater 102. Although the input voltage is set as the single phase AC signal 320, the input voltage can be set as any other suitable voltage signal (e.g., two legs of a three-phase signal, a DC signal, etc.).

[0068] Since the switching rate of the full-bridge rectifier 312 is limited, the output voltage experiences a step or a drop when converting to a voltage level that is lower than the defined power setpoint. For example, Figure 4 A plot of the output voltage of the isolated power converter 114 versus the power setpoint is shown. As shown by the solid line A, the relationship is substantially linear before a lower limit power setpoint, which in this example is about 10%. When the power setpoint is less than 10%, the relationship is no longer linear and the output voltage remains constant and then drops.

[0069] To provide a lower output voltage, the power controller 218 is configured to perform a variable frequency control of the full-bridge rectifier 312. Referring to Figure 5 An exemplary three-phase variable frequency control is provided, in which: "T1" represents a first time variable for changing the frequency from a standard operating frequency to a lower frequency level during phase 1 and phase 3; "T2" represents a second time variable that is a predefined wait time provided between each phase; and "T3" represents a third time variable for changing the pulse width of the switches from a standard pulse period (e.g., 5 μβ) to a variable pulse period (0.5 μβ).

[0070] At stage 1 of the variable frequency control, switches SW1-SW4 are open and the switching frequency is reduced from the standard operating frequency (e.g., 120 kHz) to a first frequency level (e.g., 20 kHz). Thus, for stage 1, T1 is set to the time for reducing the switching frequency to the first frequency level (i.e., increasing from 0 until the switching frequency reaches the first frequency level). Prior to starting stage 2, the variable frequency control waits for a predetermined wait time (i.e., T2) and then begins to reduce the pulse period of switches SW1-SW4 from the standard pulse period to a variable pulse period (T3). For example, in one approach, the first pair of switches SW1, SW4 are closed (i.e., driven to allow current to flow through the transformer), switch SW1 initially has the standard pulse period, and the pulse period of switch SW4 is reduced to the variable pulse period (T3). Once switch SW4 is at the variable pulse period, the pulse period of switch SW1 is reduced. The second pair of switches SW2, SW3 undergo the same control in their switching periods. It will be apparent to those skilled in the art that the adjustment of the pulse period occurs over time (i.e., over multiple switching periods), and Figure 5 is not a complete representation of this time period. In another approach, instead of varying the pulse period of each of switches SW1-SW4, the pulse period can be adjusted for one of the pair of switches. In another approach, instead of controlling the pulse period of switches SW4, SW3, the variable frequency control can reduce the pulse period of switches SW1, SW2.

[0071] With the pulse period set to T3 and switches SW1-SW4 open, the first variable time T1 is extended, for example, between switching operations of the pair of switches, to reduce the switching frequency from the first frequency level to a second frequency level during stage 3. For example, the switching frequency is reduced from 20 kHz to 2 kHz. Thus, the time between switching periods is extended. In one approach, to return to the standard operating frequency and the standard pulse period, the variable frequency control can be performed in reverse. That is, the switching frequency is increased from the second frequency level to the first frequency level, the pulse period is increased from the variable pulse period to the standard pulse period, and the switching frequency is increased from the first frequency level to the standard frequency level. It will be readily understood that the values provided for the various variables of the variable frequency control (e.g., the standard operating frequency, the first frequency level, the second frequency level, and the pulse width) are for illustrative purposes only, and other suitable values can be defined.

[0072] By employing the variable frequency control, the control of the output voltage is improved over line A, as Figure 4The isolation power converter can generate a required output voltage less than the voltage-limited power setpoint (e.g., 10% of the line power supply), and suppress voltage droop when operating at or below the lower power setpoint. In one aspect, the variable frequency control can be set as an algorithm executed by the power controller 218 for controlling the switches SW1-SW4 at or below the lower power setpoint. It should be readily appreciated that, Figure 4 The specific values shown in FIG. 6 are for illustrative purposes only and should not limit the scope of the present disclosure.

[0073] In one aspect, the power controller 218 is configured to monitor for occurrence of a magnetic run-away condition of the transformer 314, which can be caused by a voltage rise in the primary winding 314A, and perform a corrective action to suppress or reduce damage to the heater 102. Specifically, the bridge sensor 216 measures the bridge current flowing through the primary winding 314A, and if the bridge current is greater than or equal to a magnetic current threshold, the power controller 218 is configured to perform the corrective action in response to the magnetic run-away condition. In one aspect, for a first occurrence of the magnetic run-away condition, as the corrective action, the power controller 218 opens the switches SW1-SW4 to cut off power to the transformer 314 in the switch cycle being executed (i.e., the current switch cycle) and continues to operate the switches SW1-SW4 for the next switch cycle. For subsequent occurrences of the magnetic run-away condition (e.g., two or more occurrences), as the corrective action, the power controller 218 is configured to open the switches SW1-SW4 to cut off power to the transformer 314, and can further notify the main system controller 106 of the voltage rise.

[0074] As described above, the power controller 218 is configured to suppress a power surge or drop of the heater 102 based on data from the power supply sensor 212 and / or the rectified power sensor 214. For example, in one aspect, the power controller 218 is configured to open the switches SW1-SW4 to cut off power to the transformer 314 in response to the input voltage exceeding one or more thresholds (e.g., the input voltage being greater than a first threshold or the input voltage being less than a second threshold). The thresholds can be based on operating parameters of the hydronic system. The power controller 218 can also send a notification to the main system controller regarding the change in line power supply. Similar control can be performed based on data from the rectified power sensor 214.

[0075] Although Figure 1 The heater 102 in FIG. 1 is shown as having one resistive heating element 110, but the heater 102 can include one or more resistive heating elements, and the power converter system 108 can include one or more isolation power converters 114 for providing power to the resistive heating elements. For example, see Figure 5The heater 502 is controlled by a control system 504 having a main system controller 506 and a power converter system 508. The heater 502 includes a plurality of resistive heating elements 510-1 through 510-N (collectively, "resistive heating elements 510") defining a plurality of heating zones. The power converter system 508 includes one or more isolated power converters 514-1 through 514-N (isolated power converters 514) that provide power to the resistive heating elements 510. Each zone can be independently controlled and connected to a dedicated isolated power converter. Each isolated power converter 514 can be configured in a similar manner as the isolated power converter 114. The power supply 516 can be configured in a similar manner as the power supply 112.

[0076] The control system includes an isolated power converter of the present application to provide adjustable isolated power to the heater. The isolated power converter utilizes high speed switches to regulate the input voltage to the desired output voltage. The isolated power converter also performs power conversion where the heater is driven by no more than the minimum available line voltage and the input current is substantially equal to the power delivered divided by the actual line voltage. Thus, the peak current drawn from the line is at the minimum line voltage.

[0077] The power conversion can reduce the voltage applied to the heater at any given power level and reduce harmonics, thereby further reducing leakage current. However, phase angle control adds high frequency harmonics to the heater, which can increase leakage current. In addition, the isolated power converter inherently has power factor correction, so additional circuitry can not be needed to correct the power factor. That is, the current is drawn from the line supply in phase with the isolated output voltage. The isolated power converter can also not require a large capacitor (i.e., a DC side capacitor) (e.g., a large capacitor in a variable DC power supply) to store energy.

[0078] In this application, the term "controller" can refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code for execution by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

[0079] The term "memory" is a subset of the term "computer-readable medium." The term "computer-readable medium," as used herein, does not encompass transitory propagating signals or electromagnetic waves through a medium (e.g., on a carrier or the Internet). Thus, the term "computer-readable medium," as used herein, can be considered tangible and non-transitory.

[0080] Unless specifically stated otherwise, all numerical values indicate amounts by weight, unless otherwise indicated. All numerical ranges are inclusive of the recited values. All values outside the specified ranges are expressly nixed. All percentages refer to weight / weight (w / w) unless otherwise indicated.

[0081] As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using the non-exclusive logical OR, and should be interpreted not to require at least one of A, at least one of B, and at least one of C.

[0082] In the drawings, the direction of the arrows generally indicates the direction of information flow (e.g., data or instructions) of interest to the illustration. For example, when elements A and B exchange various information, but the information transmitted from element A to element B is relevant to the illustration, an arrow can point from element A to element B. This one-way arrow does not imply that no other information is transmitted from element B to element A. Additionally, for information sent from element A to element B, element B can send a request for the information or a receipt acknowledgment to element A.

[0083] The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. Such changes and modifications are intended to come within the scope of the present disclosure. Such changes and modifications can be made only in light of the spirit and the scope of the present disclosure.

Claims

1. A power converter system for providing adjustable power to a heater, comprising: an input rectifier configured to rectify a line power having a line energy; a full-bridge isolated converter comprising a full-bridge rectifier and a transformer, wherein the full-bridge isolated converter is configured to generate an isolated output voltage based on the rectified line power, wherein the isolated output voltage is electrically isolated from the line energy; a bridge sensor coupled to the full-bridge isolated converter, the bridge sensor configured to detect a current flowing through a primary winding of the transformer; and a power controller configured to: operate the full-bridge rectifier to generate the isolated output voltage; determine whether the transformer is operating in a flux walk state based on the current flowing through the primary winding of the transformer being greater than or equal to a flux current threshold; and in response to the transformer operating in the flux walk state, perform a corrective action, wherein the corrective action comprises the power controller independently controlling variable frequencies of a plurality of heating elements by adjusting an input voltage applied to the plurality of heating elements and issuing a notification to a host system controller.

2. The power converter system of claim 1, wherein, the host system controller configured to adjust the input voltage applied to the plurality of heating elements is further configured to: reduce a switching frequency of the full-bridge rectifier from a standard frequency to a first frequency; decrease a pulse period of the full-bridge rectifier when the switching frequency is equal to the first frequency; and reduce the switching frequency from the first frequency to a second frequency when the pulse period is decreased. the full-bridge rectifier comprises a first pair of electronic switches and a second pair of electronic switches to drive the transformer with the rectified line power.

3. The power converter system of claim 1, wherein, the bridge sensor is further configured to detect flux walk based on the current, and wherein the full-bridge isolated converter further comprises an output rectifier configured to rectify an isolated full-wave voltage to generate the isolated output voltage, and wherein the isolated full-wave voltage is generated by the transformer.

4. The power converter system of claim 1, wherein, a filter configured to filter the isolated output voltage to output a desired output voltage.

5. The power converter system of claim 1, further comprising: the input rectifier is configured to receive one of single-phase alternating current (AC) or direct current (DC) as the line power.

6. The power converter system of claim 1, wherein, 7. A control system, comprising: the power converter system of claim 1 ; and a host system controller configured to determine a desired output voltage and control the power converter system to generate the desired output voltage.

8. A method of converting power to operate a load powered by a line power having a line energy, the method comprising: rectifying the line power; switchably driving a transformer with the rectified line power to generate an adjustable electrically isolated full-wave voltage; ​ ​ rectifying the isolated full-wave voltage to obtain an isolated output voltage indicative of a desired output voltage applied to the load, wherein a current in phase with the isolated output voltage is extracted from the line power supply; detecting a current flowing through a primary winding of the transformer; and determining whether the transformer is operating in a flux run state based on the current flowing through the primary winding of the transformer being greater than or equal to a flux current threshold; and in response to the transformer operating in the flux run state, performing a first corrective action, wherein the corrective action includes a power controller configured to independently control variable frequencies of a plurality of heating elements by adjusting an input voltage applied to the plurality of heating elements.

9. The method of claim 8, further comprising: filtering the isolated output voltage to obtain the desired output voltage.

10. The method of claim 8, wherein, adjusting the input voltage applied to the plurality of heating elements includes: reducing a switching frequency of a full-bridge rectifier from a standard frequency to a first frequency; when the switching frequency is equal to the first frequency, reducing a pulse period of the full-bridge rectifier; and when the pulse period is reduced, reducing the switching frequency from the first frequency to a second frequency.

11. The method of claim 8, further comprising: detecting an applied voltage, wherein the applied voltage is at least one of the line power supply or the rectified line power supply; and when the applied voltage exceeds a predetermined voltage range, performing a second corrective action.

12. The method of claim 8, wherein, the line power supply is one of single-phase alternating current (AC) or direct current (DC).

13. The method of claim 8, wherein, switchably driving the transformer further includes alternatingly driving a first pair of electronic switches and a second pair of electronic switches, wherein the first pair of electronic switches and the second pair of electronic switches form a full-bridge rectifier.

14. A power converter system for providing a desired output voltage to a heater, the power converter system comprising: an input rectifier configured to rectify a line power supply having line energy; a transformer configured to generate an isolated full-wave voltage; a full-bridge rectifier electrically coupled to the transformer and operable to drive the transformer to generate the isolated full-wave voltage based on the rectified line power supply; an output rectifier configured to rectify the isolated full-wave voltage to generate an isolated output voltage indicative of the desired output voltage; a bridge sensor coupled to the transformer, the bridge sensor configured to measure a bridge current flowing through the transformer; and a power controller configured to: operate the full-bridge rectifier to drive the transformer; determine whether the transformer is operating in a flux run state based on the current flowing through a primary winding of the transformer being greater than or equal to a flux current threshold; and ​ in response to the transformer operating in the magnetic flux walk state, performing a correction action, wherein the correction action includes the power controller independently controlling variable frequencies of the plurality of heating elements by adjusting input voltages applied to the plurality of heating elements and sending a notification to a main system controller.

15. The power converter system of claim 14, wherein, The main system controller configured to adjust the input voltages applied to the plurality of heating elements is further configured to: reduce a switching frequency of the full-bridge rectifier from a standard frequency to a first frequency; when the switching frequency is equal to the first frequency, decrease a pulse period of the full-bridge rectifier; and when the pulse period is decreased, reduce the switching frequency from the first frequency to a second frequency.

16. The power converter system of claim 14, further comprising: a filter configured to filter the isolated output voltage to output the desired output voltage.

17. The power converter system of claim 14, wherein, The input rectifier is configured to receive one of single-phase alternating current (AC) or direct current (DC) as the line power.

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