Decoupling distributed control of multi-phase LLC resonant converters

Abstract

The invention relates to decoupling distributed control of a multi-phase LLC resonant converter. The invention discloses a phase controller for decoupling a phase of a multi-phase resonant converter using a lag window offset control parameter and a method for lag control of the phase of the multi-phase resonant converter using the lag window offset control parameter. The method comprises: determining a minimum 50% duty cycle (50% DC) operating frequency fmin from a set of respective 50% duty cycle (50% DC) operating frequencies for each phase of the multi-phase resonant converter; in response to the 50% duty cycle operating frequency of the phase being different from fmin, adjusting a lag window offset of the phase to change a current operating frequency of the phase toward fmin; and in response to a change in the operating condition of the phase: readjusting the lag window offset of the phase to change the operating frequency of the phase towards fmin; and if the new 50% dc operating frequency f * min of the phase is less than f * min: replacing f * min with f * min, and transmitting f * min to each other phase as a new minimum 50% dc operating frequency.

Description

Distributed control of decoupled multiphase LLC resonant converter Technical Field

[0001] This disclosure relates to multiphase resonant converters, and more particularly, to decoupling multiphase resonant converters, their controllers, and methods for controlling such converters. Background Technology

[0002] In applications such as automotive, there is a growing trend toward more compact and energy-efficient onboard chargers, which in turn increases the demand for efficient and scalable power electronic converters. For high-power applications, resonant converters, such as LLCdc-dc converters (which include a resonant circuit with both capacitors and inductors in addition to the magnetized inductor involved in the power transfer from the primary side to the secondary side), offer the potential for high efficiency.

[0003] The phases of a multiphase DC-DC resonant converter can be coupled via magnetic coupling or electrical coupling, for example, by arranging the phases such that a current flowing through one phase can be forced to reach another. Alternatively, the phases can be arranged in parallel so that they can operate relatively independently of each other. Such an arrangement can be considered “decoupled.” This disclosure relates to decoupled phases in a multiphase resonant converter. Therefore, a decoupled multiphase resonant converter can be considered fully modular, resulting in high scalability and design flexibility.

[0004] For many applications, it is necessary for the phases of a multiphase resonant converter to operate at the same frequency. Typically, this can be achieved by designating one phase as the "lead" phase and the others as "follow" phases. However, this results in symmetrical operation of the phases. A distributed control system is desired where no individual phase is a predetermined leader. Summary of the Invention

[0005] According to a first aspect of this disclosure, a method is provided for hysteresis control of the phase of a decoupled multiphase resonant converter using hysteresis window offset control parameters, the method comprising: determining a minimum 50% DC operating frequency fmin from a set consisting of corresponding 50% duty cycle (50% DC) operating frequencies for each phase of the multiphase resonant converter; adjusting the hysteresis window offset of the phase to change the current operating frequency of the phase toward fmin in response to a 50% duty cycle operating frequency of the phase being different from fmin; and, in response to a change in the operating conditions of the phase: readjusting the hysteresis window offset of the phase to change the operating frequency of the phase toward fmin; and, if the new 50% DC operating frequency f*min of the phase is less than fmin: replacing fmin with f*min, and transmitting f*min as the new minimum 50% duty cycle operating frequency to each other phase.

[0006] Thus, each phase or module of the multiphase converter is arranged to operate at the (same) frequency, with one of the phases operating at a 50% duty cycle. The system is able to react to changes or disturbances by periodically adjusting the hysteresis window offset of each phase controller (which directly adjusts its duty cycle) to ensure operation at this frequency, and if operating conditions change, the system can calculate and ensure that each phase is aware of the new (same) operating frequency, with one of the phases operating at a 50% duty cycle.

[0007] In one or more embodiments, the method further includes storing a set of corresponding 50% duty cycle operating frequencies for each phase of the multiphase resonant converter in a memory. In one or more such embodiments, if the 50% duty cycle operating frequency of a phase is greater than f*min before the operating conditions change, then fmin is replaced with f*min in the memory. The memory may include a set of registers to store the set of 50% duty cycle operating frequencies for each phase, and each phase independently selects the (same) register indicating the minimum frequency in this set, which then becomes the target or reference operating frequency. Each phase may have its own independent memory, or the memory may be centrally located.

[0008] In one or more embodiments, a change in the phase operating conditions is a change in one of the following groups: input voltage, input current, load impedance, and load current. The system is able to react to such changes in operating conditions and return to a stable operating state without the need for central control.

[0009] In one or more embodiments, the hysteresis window offset is an offset from the midpoint between a high input voltage level and a low input voltage level. In one or more embodiments, adjusting the phase hysteresis window offset to change the current operating frequency of the phase toward fmin includes: adjusting the phase hysteresis window offset to change the current operating frequency of the phase until the current operating frequency of the phase is equal to fmin.

[0010] In one or more embodiments, the method further includes adjusting the hysteresis window width of the phase to control the output current of the phase. The hysteresis window width may be the difference between a low-voltage control setpoint and a high-voltage control setpoint, the low-voltage control setpoint being used to begin charging the resonant circuit of the phase, and the high-voltage control setpoint being used to stop charging the resonant circuit of the phase.

[0011] According to a second aspect of this disclosure, a phase controller for decoupling the phases of a multiphase resonant converter using hysteresis window offset control parameters is provided. The phase controller includes: a hysteresis control module configured to control the phase using a hysteresis window width and a hysteresis window offset to control the phase duty cycle; a memory configured to store the minimum 50% DC operating frequency fmin from a set of corresponding 50% duty cycles, i.e., 50% DC operating frequencies, for each phase of the multiphase resonant converter; and a communication module configured to transmit and receive signals indicating fmin; wherein the hysteresis control module is further configured to: adjust the phase hysteresis window offset to change the current operating frequency of the phase toward fmin in response to a difference between the 50% DC operating frequency of the phase and fmin; and, in response to a change in the operating conditions of the phase: readjust the phase hysteresis window offset to change the operating frequency of the phase toward fmin; and, at the obtained 50% of the phase... If the DC operating frequency f*min is less than fmin, fmin is replaced with f*min; and the communication module is configured to transmit f*min as the new minimum 50% DC operating frequency to each other phase.

[0012] In one or more embodiments, the memory is additionally configured to store a set of corresponding 50% duty cycle operating frequencies for each phase of the multiphase resonant converter.

[0013] In one or more embodiments, the phase controller is further configured to replace fmin with f*min in memory in response to f*min being less than the 50% duty cycle operating frequency of the phase before the operating conditions change.

[0014] In one or more embodiments, the change in the phase operating conditions is a change of one of the following: input voltage, input current, load impedance, and load current. In one or more embodiments, the hysteresis window offset is an offset from the midpoint between a high input voltage level and a low input voltage level. In one or more embodiments, adjusting the phase hysteresis window offset to change the current operating frequency of the phase toward fmin includes: adjusting the phase hysteresis window offset to change the current operating frequency of the phase until the current operating frequency of the phase equals fmin. In one or more embodiments, the phase controller is additionally configured to adjust the phase hysteresis window width to control the output current of the phase.

[0015] According to another aspect of this disclosure, a method for controlling a multiphase DC-DC resonant converter is provided, the method comprising: each phase broadcasting its own 50% duty cycle operating frequency to provide a set of 50% duty cycle operating frequencies; each phase adjusting its operating frequency toward the minimum of the set of 50% duty cycle operating frequencies by changing a hysteresis window offset; and, in response to operating at a 50% duty cycle, any one of the phases rebroadcasting its own 50% duty cycle operating frequency.

[0016] The method may further include: replacing the current minimum value with the rebroadcast frequency in response to a rebroadcast 50% duty cycle operating frequency being lower than the current minimum value in the set of 50% duty cycle operating frequencies. In one or more embodiments, the method further includes a corresponding controller for each phase storing the set of 50% duty cycle operating frequencies in a corresponding lookup table (LUT). In one or more embodiments, in response to a rebroadcast, the corresponding controller for each phase updates the corresponding value in the LUT. The method may further include, in response to a change in the operating conditions of one of the phases, the one in said phase readjusting its operating frequency toward the minimum value in the set of 50% duty cycle operating frequencies by changing the hysteresis window offset.

[0017] A computer program may be provided that, when executed on a computer, causes the computer to configure the computer to include any device comprising the circuits, controllers, sensors, filters, or means disclosed herein, or to perform any of the methods disclosed herein. The computer program may be a software implementation, and the computer may be considered any suitable hardware, including digital signal processors, microcontrollers, and implementations in read-only memory (ROM), erasable programmable read-only memory (EPROM), or electrically erasable programmable read-only memory (EEPROM), these being non-limiting examples. The software implementation may be an assembler.

[0018] A computer program may be provided on a computer-readable medium, which may be a physical computer-readable medium such as a disk or storage device, or may be embodied in another non-transitory signal. Attached Figure Description

[0019] Now we will refer to the accompanying drawing, which may not be drawn to scale, and in the accompanying drawing:

[0020] Figure 1 shows an example of a decoupled multiphase resonant converter;

[0021] Figure 2A shows the frequency of an oscillating system such as a DC-DC switching converter;

[0022] Figure 2B shows the hysteresis control corresponding to Figure 2A;

[0023] Figure 3 shows the "equal current" curves or trajectories of the five modules of the multiphase LLC resonant converter in the duty cycle / frequency plane;

[0024] Figure 4 illustrates the control mechanism according to a part of this disclosure;

[0025] Figure 5 illustrates the control mechanism based on the change of operating conditions for one of the phases;

[0026] Figures 6 and 7 illustrate the control mechanism that varies depending on the operating conditions of one of the phases; and

[0027] Figure 8 shows the communication components between the controller and a portion of one of the phase controllers.

[0028] It should be noted that the figures are illustrative and not drawn to scale. For clarity and convenience, the relative dimensions and proportions of the parts in these figures have been shown by enlarging or reducing them in size. The same reference numerals are generally used to refer to corresponding or similar features in modified and different embodiments. Detailed Implementation

[0029] This disclosure relates to the control of decoupled multiphase resonant converters, and more particularly, to such DC-DC converters. Figure 1 illustrates an example of a decoupled multiphase resonant converter 100. Figure 1 shows three independent modules or phases 110, 120, and 130 configured in parallel. The phases can be LLC converters, CLLC converters, or any other suitable resonant converter with a half-bridge or full-bridge configuration as required. Each phase is powered by a current at an input voltage Vin, which, as shown, can be symmetrical about zero voltage and therefore has a high input voltage level +Vin / 2 and a low input voltage level -Vin / 2. Each phase outputs a current at an output voltage Vout, which, as shown, can be symmetrical about 0 voltage and therefore has a high input voltage level +Vout / 2 and a low input voltage level -Vout / 2. The phases supply corresponding output currents Iout1, Iout2, and Iout3, which can be equal to each other, especially when the modules have the same size, or they can be different. The total output current Iout can be used to power a load 140. Of course, it should be understood that the input voltage does not have to be symmetrical about 0 voltage, but can be at some other level, as long as it is tracked by the controller to achieve appropriate adjustment of the high threshold voltage and the low threshold voltage, as described below.

[0030] In the control inputs used for each phase, the resonant converter has two degrees of freedom. The duty cycle and frequency can be directly controlled; conversely, the upper and lower limits of the hysteresis window can be controlled. In this hysteresis control, the difference between the upper and lower limits (typically defined by the maximum and minimum voltages at appropriate points in the converter circuit) can be called the hysteresis window width; the displacement of the window center from the midpoint between the upper and lower input voltage levels can be called the hysteresis window offset. This is illustrated in Figures 2A and 2B. Figure 2A shows the frequency freq of an oscillating system such as a DC-DC switching converter: this is shown as cycle period 1 / freq 210 from left to right over time. Figure 2A also shows the duty cycle dc, which is defined by the following formula:

[0031] dc = Ton / (Ton + Toff) = f.Ton

[0032] Where Ton 220 is the on-time and Tofff 230 is the off-time, and...

[0033] Ton + Toff = 1 / freq.

[0034] Figure 2B illustrates hysteresis control using the hysteresis window width hww parameter 240 and the second hysteresis window offset parameter hwo 250. In the example shown, the input voltage is symmetrical about the midpoint "0 V" level, so the offset can be positive or negative near zero.

[0035] The inventors of this case have learned that there is an equivalence relationship between duty cycle and frequency control, and between hysteresis window width and hysteresis window offset control, and that this equivalence can be used to achieve distributed or so-called “masterless” or leaderless control of the converter, as will be described in more detail below.

[0036] Specifically, for a DC-DC converter where individual phases are not coupled, the current through individual phases can vary between phases, but because the modules are arranged in parallel, the output voltage of each phase must be the same. Since the modules also share a common input voltage, this means that the voltage conversion ratio M, defined as M = Vout / Vin, must be the same for each module. Furthermore, since the individual phases of a multiphase resonant converter (which can also be referred to as converter "modules") have two degrees of freedom, two control parameters can be adjusted in a combined manner to maintain a given output current at a given conversion ratio M.

[0037] This is illustrated in Figure 3. Figure 3 shows the "equal current" curves, or trajectories, of the five modules of the multiphase LLC resonant converter in the duty cycle / frequency plane, where the inductance or capacitance values ​​of the LLC components vary compared to the nominal values ​​shown at A 310. Specifically, in each case, increasing the values ​​of the magnetizing inductance Lm, resonant inductance Lr, and resonant capacitance Cr by 20% produces the "equal current" curves B 320, C 330, and D 340, respectively, and increasing all three values ​​by 20% produces curve E 350. The curves are "equal current" curves because they show the combination of duty cycle and frequency that produces the same current output. For each curve, the operating frequency is maximum at a 50% duty cycle, and the frequency that maintains a fixed output current decreases symmetrically as the duty cycle increases or decreases from the 50% value.

[0038] The vertical lines in Figure 3 represent individual frequencies. As already stated, all phases of the multiphase resonant converter need to operate at a common frequency, and this can be represented on the duty cycle / frequency plane of Figure 3 by the requirement of vertical alignment along the operating points of the "equal current" curves of each module. Furthermore, it should be understood that duty cycle variation between phases can be minimized by selecting a frequency that intersects the lowest frequency module at 50%, as shown at frequency 360 in Figure 3. It should be understood that deviating from a 50% duty cycle increases the DC component of the voltage, which in turn increases voltage stress on the components. Furthermore, deviating from 50% exacerbates signal distortion, causing it to deviate from a proper sinusoidal waveform, which in turn may lead to increased RMS losses in the resonant circuit.

[0039] According to this disclosure, any number of uncoupled resonant DC-DC converters can be connected in parallel and controlled to converge to the same frequency based on a “limiting module”, while minimizing this frequency at which at least one of the modules operates at 50% DC, provided that at least one of the modules operates at 50% DC. For example, the identity of the “limiting module” is not known a priori due to component mismatch. Furthermore, the phase corresponding to the limiting module can change during operation, as will be described in more detail below. Using the methods disclosed herein, stable control of multiphase systems can be achieved using decentralized (i.e., leaderless or masterless) control. It should be understood that this is particularly challenging for implementing self-oscillating resonant converters, as they operate asynchronously by default.

[0040] Figure 4 illustrates the control mechanism according to a portion of this disclosure. Specifically, each phase begins operation with a 50% duty cycle, that is, at points 312, 332, 342, and 352, as shown. To avoid confusion in the following discussion, only the four phases of Figure 3 are shown in Figure 4 and the following figures, with phase B 320 omitted for clarity.

[0041] The controller determines the “minimum 50% duty cycle operating frequency” fmin from a set consisting of the corresponding 50% duty cycle operating frequencies of each phase of the multiphase resonant converter. In other words, the operating frequency of each of phases A, C, D, and E at 50% duty cycle is measured and can be stored in memory; in the example shown, the frequency fmin of phase E 350 is found to be the minimum. Since phase 350 has the minimum frequency at its 50% duty cycle, this phase will at least temporarily become the “limiting module”.

[0042] Since the operating frequency of each of the other phases differs from fmin, the controller is used to indirectly change the duty cycle of each phase (except phase E 350) toward fmin until the frequency of each phase is aligned at fmin. Typically, because the characteristic curves are symmetrical about the 50% duty cycle, the operating point of each phase can be moved toward fmin by shifting it upwards (as shown by arrow 430 for phase C 330) or downwards along the characteristic isocurrent curve of the phase.

[0043] As mentioned, the controller is used to indirectly change the duty cycle. Specifically, instead of directly changing the duty cycle (in hysteresis control methods, the controller typically does not directly control), the controller shifts the hysteresis window offset from its average position (up or down). Those skilled in the art will understand that, all other things being equal, changing the offset corresponds to changing the duty cycle. Specifically, the output current depends only on the norm (duty cycle) -50%, i.e., the deviation from 50%. The difference between the downward deviation (i.e., below the 50% point) and the upward deviation (i.e., above the 50% point) is the DC voltage offset of the resonant capacitor voltage (negative or positive, respectively). This is the dual effect of this action, the reason why the midpoint of the shifted hysteresis control (vth-vtl) / 2 affects the duty cycle: it shifts the DC (0 Hz) component of the capacitor voltage, which in turn manifests as a change in the duty cycle of the self-oscillating signal, since the operating point of the system must be unique. In other words, the offset in the hysteresis window causes a offset in the capacitor voltage, which corresponds to a change in the duty cycle required to inject the DC component into the capacitor voltage signal (caused by switching asymmetry), and thus the self-oscillating system just happens to cause this.

[0044] In other words, for each phase, in response to the phase's 50% duty cycle operating frequency differing from fmin, the controller acts on a hysteresis window offset of the phase to change the phase's current operating frequency toward fmin, and typically to fmin. Once the phase's operating points are aligned with fmin in frequency (that is, they are at points 314, 334, 344, and 352, as shown in the figure), the multiphase converter can continue to operate in a steady state under optimal conditions.

[0045] However, the control system also needs to be able to respond to changes in operating conditions, which can be disturbances or permanent changes. The control system achieves this by implementing two control laws. The first of these control laws requires that the phase update the system whenever and only when the 50% duty cycle operating frequency of the phase itself changes (and at system startup when all converters start at different frequencies), and specifically identifies the update to the controllers of other phases. Therefore, the value of fmin changes only when this phase is the phase with the minimum 50% duty cycle operating frequency. The second of the control laws requires each converter to adjust its frequency toward frequency fmin by changing the hysteresis window offset (which thus corresponds to changing its duty cycle). In some embodiments, the adjustment can be implemented by means of a proportional-integral (PI) or proportional-integral-derivative (PID) controller, where the error is the difference between the operating frequency of the respective module and fmin, or the difference between their respective inverse operating switching cycles (defined as 1 / f_op) and Tmax (defined as 1 / fmin). The control signal from the controller is the hysteresis window offset. This adjustment will be described in more detail with reference to Figures 4, 5, and 6.

[0046] Figure 5 illustrates a change in the operating conditions of one of the phases, where the operation of one of the phases (in this example, phase C 330) shifts along its characteristic isocurrent curve to position 534. This could be caused, for example, by a digital fault in the controller or some noise in the communication channel entering the digital / analog controller. By implementing a second control law, the controller for phase C adjusts its hysteresis window offset (towards zero in this case) so that the operating point of phase C 330 shifts backward along the isocurrent curve until it stabilizes at a stable operating point 334 at fmin. Although in the example shown in Figure 5 the disturbance is a decrease in frequency, implementing the same second control law in the opposite example with an increasing frequency would similarly cause the operating point of phase C to shift back along the isocurrent curve to the stable operating point 334 at fmin.

[0047] Figure 6 illustrates a different change in the operating conditions of one of the phases. In this example, the load may have changed, resulting in a different load impedance and thus setting different requirements for the output current. Therefore, one or more phases no longer operate along the same isocurrent characteristic curve; they operate along different isocurrent characteristic curves due to the different currents. To avoid confusion regarding the operation of the entire system, in the example of Figure 6, it is assumed that the current requirement from only one phase (phase C 330 in the illustrated example) has been modified. Therefore, the phase now operates along the new isocurrent curve 630 shown in Figure 6. In the illustrated example, a decrease in current is shown, which can correspond to a generally leftward shift of the characteristic isocurrent curve 630 relative to the original operating curve 330.

[0048] Due to this change or disturbance in operating conditions, the two control laws described above operate as follows: When a change occurs, the controller for phase C operates with the same hysteresis window offset as before the change, so the operating point of the phase does not change in the vertical direction, but rather shifts horizontally to the left, as shown at 632. The operating frequency of phase C is now different from fmin, so the phase control adjusts the hysteresis window offset to change the operating frequency toward fmin. The operating point of phase C thus moves around its new isocurrent characteristic curve, as shown at 633. In the example shown, the entire new operating curve 630 of phase C is to the left of the system's current minimum 50% duty cycle operating frequency fmin (that is, at a lower frequency). Therefore, the operating point of phase C reaches the 50% duty cycle operating point shown at 634, without ever reaching the operating frequency fmin. According to the first control law, since this phase now operates with a 50% duty cycle, it updates the rest of the system with its new 50% duty cycle operating frequency (shown as f*min).

[0049] Since the value of f*min is less than the value of fmin, the system updates fmin by replacing fmin with f*min. Therefore, none of the other phases A, D, and E now operate at the "correct" target frequency, which is now f*min instead of the original fmin. The second control law now forces each of the other phases to change their operating point. This is illustrated in Figure 6 by phase A adjusting its operating point to position 614, phase D adjusting its operating point to position 644, and phase B adjusting its operating point to position 654, also as shown. It should be understood that the frequency of each of operating points 614, 644, and 654 is f*min, which is the new minimum 50% duty cycle operating point in the set.

[0050] In the example shown in Figure 6, the new isocurrent characteristic curve of phase C lies entirely to the left of the old minimum 50% duty cycle operating frequency fmin (i.e., at a lower frequency). In other cases, the change in current requirement from phase C may not be so extreme that its new characteristic curve intersects the fmin line in Figure 6 before reaching the 50% duty cycle. In this case, the operating point of phase C stabilizes at fmin and does not move further around the curve (typically with a small overshoot due to the stability of the control system): in this case, phase C does not operate at a 50% duty cycle and therefore does not broadcast or even know its new operating frequency at a 50% duty cycle.

[0051] Those skilled in the art will understand that the alteration of the operating conditions of a phase, causing it to operate according to a new isocurrent characteristic curve without even knowing its operating frequency at 50% duty cycle, does not lead to ambiguity in the overall system. Specifically, even if the "unknown" frequency (which can be denoted as f?min) at 50% duty cycle for this phase becomes the minimum 50% duty cycle operating frequency for the phase, and this is unknown to the system, this phase will adjust its operating point toward a frequency (f*min) that is understood by the system as the minimum 50% duty cycle operating frequency. This will achieve its own 50% duty cycle operating frequency (f?min) instead of f*min. According to the first control law, the phase will then broadcast this frequency (f?min), which will become the new minimum 50% duty cycle operating frequency for the entire system.

[0052] Figure 7 illustrates another change in the disturbance. In this example, the operating conditions of phase E are modified, for example, by reducing the current requirement from the phase or module, so that the phase operates according to a new isocurrent curve shown as 750 in Figure 7. Before the disturbance change, phase E operates at a 50% duty cycle at frequency fmin, as shown at position 352. Phase E is therefore a limiting module. Due to the change, the operating point of phase E shifts to the right (horizontally, because the control of phase E has not yet adjusted its hysteresis window offset) to the new operating position 752. According to the first control law, this phase informs the system of its (new) 50% duty cycle operating frequency fnew. However, this frequency is no longer the minimum frequency in the set of 50% duty cycle operating frequencies. The system must update fmin. In this example, the new minimum 50% duty cycle operating frequency is the frequency f*min of phase D. Although phase D is not currently operating at this frequency, it has a positive hysteresis window offset at operating point 344. However, it should be recalled that at the start of system operation, each phase operated with its own 50% duty cycle, enabling the system to recognize each 50% duty cycle operating frequency, and this frequency may have already been stored in memory. Therefore, a new value for fmin (f*min) is available to the system.

[0053] Because a new minimum 50% duty cycle operating frequency (f*min) exists, the second control law requires each phase to adjust its own operating frequency toward this new minimum 50% duty cycle operating frequency. Therefore, phase A moves its operating point from 314 to 714, phase C moves its operating point from 334 to 734, and phase D moves its operating point from 344 to 744. Finally, phase E moves its operating point from 752 to 754.

[0054] Figures 4 to 7 above and their related descriptions illustrate two control laws that form the basis of the method consistent with this disclosure. Specifically, the first control law requires the converter to update the broadcast frequency to the remainder of the system only when its duty cycle is 50%; the second control law requires each converter to adjust its frequency toward the currently known reference frequency by changing the offset of its hysteresis window (which corresponds to changing or adjusting its duty cycle). Those skilled in the art will understand that this adjustment and stabilization process is passive in the sense that no specific phase controller is required to command other phases to adjust. The process mentioned above with respect to Figures 4 to 7 explains how the system thus passively reaches a new operating point as the characteristic curve changes shape.

[0055] It should be understood that the corresponding controller for each phase needs to know the current minimum 50% duty cycle operating frequency. This can be achieved in any of a variety of ways. For example, each phase controller may include a lookup table of the 50% duty cycle operating frequencies for each phase, and routinely or periodically check the lookup table to determine the minimum value in the lookup table, which is used as fmin, i.e., the current reference or target frequency. In such embodiments, each phase controller may broadcast its own 50% duty cycle operating frequency to all other phases. Such embodiments may typically require each phase controller to be able to communicate directly with all other phase controllers. In other embodiments, other network architectures may be used, such as fully connected star networks or ring networks. In a ring network, each phase controller is typically connected to only two other phase controllers in a ring configuration. In such embodiments, the entire set of 50% duty cycle operating frequencies can be transmitted around the ring from one controller to its immediate neighbor, and so on.

[0056] Alternatively, and again without limitation, each controller may only transmit the minimum 50% duty cycle operating frequency to its neighbors. In such embodiments, whenever a phase controller (e.g., for phase x) receives the currently known minimum 50% duty cycle operating frequency fmin from its neighbor, it may compare this frequency with its own locally stored 50% duty cycle operating frequency (which may be denoted as fxmin). If fxmin < fmin, the controller for phase x replaces fmin with the new lower value fxmin and forwards this value as the minimum 50% duty cycle operating frequency to its neighboring controllers, which should be a reference or target frequency. Otherwise, it simply forwards the original value fmin as the minimum 50% duty cycle operating frequency. In such embodiments, the phase controllers typically need to communicate continuously around the loop to be able to react efficiently and quickly to new fmin reached by any phase.

[0057] As a variation of the above method, the phase controller can again transmit the current value of fmin and the next lowest value (which can be described as f2min) in a "round-robin" manner. By transmitting two values ​​in a loop, when fxmin > f2min, the controller for the phase used as a reference phase that has undergone a change in operating conditions causing its 50% duty cycle operating frequency (fxmin) to increase can immediately know the new target or reference frequency. In other words, by knowing each phase of the two lowest potential reference frequencies, the system can react more quickly to situations such as those described above with reference to Figure 7.

[0058] Those skilled in the art will appreciate that the above discussion focuses on the independence of the phase controller for each individual phase of a multiphase converter. Independent phase control allows for true system modularity. This can be advantageous, for example, by allowing the addition, replacement, or removal of phases including the phase controller from the overall controller assembly. In other embodiments, two or more phase controllers can be implemented as sub-units of a multiphase controller controlling more than one phase. Thus, a multiphase converter can include sub-units with more than one phase. In still other embodiments, a single controller can be used to control each phase. The individual sub-units of the single controller can still operate independently of each other. In such embodiments, a single lookup table can be made available to each sub-unit for controlling individual phases.

[0059] In embodiments where individual controllers are used to control independent phases, the phases may have separate clocks. The clocks may be driven by local oscillators, which may include mismatches. Those skilled in the art will understand that, in order for each phase to determine a minimum 50% duty cycle operating frequency, the clocks should be synchronized to eliminate mismatches, or each phase should receive a signal from another controller based on which phase has the minimum 50% duty cycle operating frequency, and this frequency is derived from its own clock.

[0060] Figure 8 illustrates the communication components between controllers, and is part of one of the phase controllers, which provides a solution to the aforementioned problem while avoiding the need to determine and correct for mismatches between the oscillator and the clock. Instead of transmitting values ​​corresponding to their own 50% duty cycle operating frequencies, the controllers of each converter 802, 804, 806… transmit PWM signals PWM1, PWM2, PWM3… representing their own 50% duty cycle operating frequencies. In the example shown, these PWM signals are broadcast via bus 810; however, in other embodiments as described above, the PWM signals are transmitted in a loop. In module 820 of the local phase controller, the local phase controller uses counter 830 to measure the frequency of the PWM signal received from another controller. The controller uses its own local clock to measure the frequency of the PWM signal. A multiplexer 840 is used to direct the (locally) measured frequencies f1, f2, f3… to the appropriate registers in register set 850. Since the frequencies are f1, f2, f3… representing the 50% duty cycle operating frequencies of each of the other phases already determined using the same (local) counter, they are locally consistent. The value in each register may differ from the corresponding value in the corresponding register set of another local controller; however, the order of the values ​​will be the same on each local controller.

[0061] The illustrated embodiments described herein are intended to provide a general understanding of the structure of various embodiments and are not intended to serve as a comprehensive description of all elements and features of devices and systems that may utilize the structures described herein. Many other embodiments will become apparent to those skilled in the art upon review of the above description. Other embodiments can be utilized and derived therefrom, allowing structural and logical substitutions and changes to be made without departing from the scope of this disclosure. The drawings are representative only and may not be drawn to scale. Some scales may be enlarged, and others may be minimized. Therefore, the specification and drawings should be considered illustrative rather than restrictive.

[0062] Although specific embodiments have been illustrated and described herein, it should be understood that any arrangement contemplated or configured to achieve the same or similar purpose may replace the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of the various embodiments. This disclosure is prudently considered in combination with the embodiments described above and other embodiments not specifically described herein.

[0063] For example, one or more features or aspects from one or more embodiments may be combined with one or more features or aspects from one or more other embodiments. In one or more embodiments, a positively referenced feature may also be negatively referenced and excluded from the embodiments, whether or not it is replaced by another structural and / or functional feature. The steps or functions described with respect to embodiments of this disclosure may be performed in any order. The steps or functions described with respect to embodiments of this disclosure may be performed individually, in combination with other steps or functions of this disclosure, or according to other embodiments or according to other steps not described in this disclosure. Additionally, more or fewer of all the features described with respect to embodiments may be used.

[0064] Fewer than all the steps or functions described with respect to the exemplary process or method may be performed in one or more exemplary embodiments. Furthermore, unless explicitly stated otherwise, the use of numerical terms such as first, second, third, etc., to describe devices, components, steps, or functions is not intended to describe a sequence or function. Unless otherwise explicitly stated, the use of the terms first, second, third, etc., is generally for distinguishing devices, components, steps, or functions. Additionally, one or more devices or components described with respect to exemplary embodiments may facilitate one or more functions, wherein said facilitation (e.g., facilitating access or facilitating connection establishment) may include fewer than each step required to perform the function, or may include all the steps required to perform the function.

[0065] In providing this abstract, it should be understood that the abstract is not intended to interpret or limit the scope or meaning of the claims. Furthermore, in the foregoing embodiments, it can be seen that various features are grouped together in a single embodiment for the purpose of simplification. This approach of the disclosure should not be construed as reflecting an intention that the claimed embodiment requires more features than expressly recited in each claim. In fact, as reflected in the appended claims, the subject matter of the invention lies in fewer than all features of a single disclosed embodiment. Therefore, the appended claims are hereby incorporated into the detailed description, wherein each claim stands alone as a separately claimed subject matter.

Claims

1. A method for hysteresis control of the phase of a decoupled multiphase resonant converter using hysteresis window offset control parameters, characterized in that, The method includes: determining a minimum 50% DC operating frequency fmin from a set consisting of corresponding 50% duty cycle DC operating frequencies for each phase of the multiphase resonant converter; adjusting the hysteresis window offset of the phase to change the current operating frequency of the phase toward fmin in response to the 50% DC operating frequency of the phase being different from fmin; and readjusting the hysteresis window offset of the phase to change the operating frequency of the phase toward fmin in response to a change in the operating conditions of the phase; and if the new 50% DC operating frequency f*min of the phase is less than fmin: replacing fmin with f*min, and transmitting f*min as the new minimum 50% duty cycle operating frequency to each other phase.

2. The method according to claim 1, characterized in that, Additionally, the set of the corresponding 50% duty cycle operating frequencies for each phase of the multiphase resonant converter is stored in a memory.

3. The method according to claim 2, characterized in that, Additionally, if the 50% duty cycle operating frequency of the phase is greater than f*min before the operating conditions change, then fmin is replaced with f*min in the memory.

4. The method according to claim 1, characterized in that, Adjusting the hysteresis window offset of the phase to change the current operating frequency of the phase toward fmin includes: adjusting the hysteresis window offset of the phase to change the current operating frequency of the phase until the current operating frequency of the phase is equal to fmin.

5. The method according to claim 1, characterized in that, Additionally, the hysteresis window width of the phase is adjusted to control the output current of the phase; the hysteresis window width is the difference between a low-voltage control setpoint and a high-voltage control setpoint, the low-voltage control setpoint being used to begin charging the resonant circuit of the phase, and the high-voltage control setpoint being used to stop charging the resonant circuit of the phase.

6. A phase controller for decoupling the phase of a multiphase resonant converter using hysteresis window offset control parameters, characterized in that, The phase controller includes: a hysteresis control module configured to control the phase using a hysteresis window width and a hysteresis window offset to control the duty cycle of the phase; a memory configured to store a minimum 50% DC operating frequency fmin from a set of corresponding 50% duty cycle DC operating frequencies of each phase of the multiphase resonant converter; and a communication module configured to transmit and receive signals indicating fmin; wherein the hysteresis control module is further configured to: adjust the hysteresis window offset of the phase to change the current operating frequency of the phase toward fmin in response to the 50% DC operating frequency of the phase being different from fmin; and readjust the hysteresis window offset of the phase to change the operating frequency of the phase toward fmin in response to a change in the operating conditions of the phase; and replace fmin with f*min if the resulting 50% DC operating frequency f*min of the phase is less than fmin; and wherein the communication module is configured to transmit f*min as the new minimum 50% DC operating frequency to each other phase.

7. The phase controller according to claim 6, characterized in that, The phase controller is further configured to replace fmin with f*min in the memory in response to the 50% duty cycle operating frequency of the phase before the operating conditions change.

8. The phase controller according to claim 6, characterized in that, Adjusting the hysteresis window offset of the phase to change the current operating frequency of the phase toward fmin includes: adjusting the hysteresis window offset of the phase to change the current operating frequency of the phase until the current operating frequency of the phase is equal to fmin.

9. A method for controlling a multiphase DC-DC resonant converter, characterized in that, The method includes: each phase broadcasting its own 50% duty cycle operating frequency to provide a set of 50% duty cycle operating frequencies; each phase adjusting its operating frequency toward the minimum of the set of 50% duty cycle operating frequencies by changing the hysteresis window offset; and in response to operating at a 50% duty cycle, any one of the phases rebroadcasting its own 50% duty cycle operating frequency.

10. The method according to claim 9, characterized in that, In addition, including: In response to the rebroadcast 50% duty cycle operating frequency being lower than the current minimum in the set of 50% duty cycle operating frequencies, the current minimum is replaced with the rebroadcast frequency.

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