Pole Compensation in a Reconfigurable Power Converter

Abstract

In a power converter including a switched capacitor circuit connected to a switched inductor circuit, reconfiguration logic causes the switched capacitor circuit to transition between a first switched capacitor configuration and a second switched capacitor configuration having different voltage transformation ratios. A compensator compensates for a change in a forward transfer function of the power converter that would otherwise be caused by the transition between the two switched capacitor configurations.

Description

Technical Field

[0001] The present disclosure relates to power converters, and more particularly, to controlling the operation of a power converter. Background Art

[0002] It is desirable for a power converter to convert a first voltage into a second voltage. In doing so, it is necessary to control the power converter to produce the correct second voltage in the presence of changes in the load of the first voltage or the second voltage.

[0003] The control of a power converter can involve the use of feedback, thereby forming a power converter with feedback control. For simplicity, a power converter with feedback control will be referred to herein as a "controlled power converter". A power converter without feedback control is referred to herein as an "uncontrolled power converter".

[0004] Generally, the overall "closed-loop" response of a controlled power converter depends on the loop transfer function, which includes the forward transfer function provided by the uncontrolled power converter and the feedback transfer function provided by one or more feedback modules. The combination of the forward transfer function and the feedback transfer function produces the closed-loop transfer function of the controlled power converter.

[0005] The proper design of the feedback module provides a way to control various characteristics of the operation of a power converter. For example, the feedback transfer function can be used to avoid instability or to adjust the allowable gain margin or phase margin of the entire controlled power converter.

[0006] Needless to say, the feedback transfer function is closely coupled with the forward transfer function. If the forward transfer function changes, it is generally also necessary to change the feedback transfer function to maintain the desired characteristics of the controlled power converter. This means that the feedback transfer function cannot be properly designed without knowledge of the forward transfer function.

[0007] Generally, this does not pose a difficulty. The forward transfer function can be obtained experimentally or by examining a specification sheet provided by the manufacturer of the power converter. However, this is on the premise that the forward transfer function remains unchanged. If the forward transfer function changes significantly during operation, especially if the forward transfer function changes significantly in an unpredictable manner, then one is faced with a moving target. Therefore, it is difficult to properly design the feedback module. Summary of the Invention

[0008] On the one hand, the present invention relates to reconfiguring a switched capacitor circuit of a power converter such that: such reconfiguration does not require reconfiguring at least one of the compensation circuits for controlling the power converter. In particular, the present invention relates to reconfiguring the switched capacitor circuit of a power converter and its first compensation circuit to avoid the need to change its second compensation circuit, thereby avoiding changing the loop transfer function on which the appropriate feedback design depends. For example, the first compensation circuit reconfigured with the power converter can be integrated with the power converter and can be reconfigured by the same reconfiguration logic that reconfigures the switched capacitor circuit. This avoids the need to reconfigure an external compensation circuit.

[0009] On the one hand, the present invention features a compensator and reconfiguration logic. The reconfiguration logic causes the switched capacitor circuit connected to a regulator to transition between a first switched capacitor configuration and a second switched capacitor configuration having respective first and second turns ratios that are different from each other. This causes a change in the forward transfer function of the uncontrolled power converter defined by the switched capacitor circuit and the regulator. The compensator compensates for the change in the forward transfer function that will be caused by the transition between the first switched capacitor configuration and the second switched capacitor configuration.

[0010] In some embodiments, the reconfiguration logic reconfigures both the switched capacitor circuit and the compensator.

[0011] In other embodiments, when the reconfiguration logic causes the switched capacitor to be reconfigured, the reconfiguration logic also causes the compensator to be reconfigured to compensate for the change caused by reconfiguring the switched capacitor circuit.

[0012] In other embodiments, the compensator includes a first compensation circuit that receives a voltage from a second compensation circuit. In these embodiments: the compensation is distributed between the first compensation circuit and the second compensation circuit that supplies a signal to the first compensation circuit. In these embodiments: the second compensation circuit controls the gain margin and phase margin of the loop transfer function.

[0013] In some embodiments, the compensator compensates for the linear component of the change in the forward transfer function. In these embodiments: the compensator includes a first compensation circuit that compensates for the linear component of the change in the forward transfer function and receives a voltage from a second compensation circuit that compensates for the non-linear component of the change.

[0014] In some embodiments, the compensator has a compensator transfer function, and the transition between the configurations causes the zeros of the compensator transfer function to move in frequency steps.

[0015] In the following embodiments: When the reconfiguration logic causes the switched capacitor circuit to transition to a second configuration, the combination of the switched capacitor circuit in the second configuration and the switched inductor circuit has a transfer function: The transfer function has a pole that changes frequency. In such an embodiment, the reconfiguration logic causes the compensator transfer function to have a zero that chases the pole in the frequency space.

[0016] In the following embodiments: When the reconfiguration logic causes the switched capacitor circuit to transition to a second configuration, the combination of the switched capacitor circuit in the second configuration and the switched inductor circuit has a transfer function: The transfer function has a pole with a pole frequency, where each compensator configuration defines a gap between the zero frequency and the pole frequency corresponding to the configuration, the zero frequency corresponding to the frequency of the zero associated with the compensator configuration, where there is a set of gaps, each gap corresponding to the difference between the pole frequency and the zero frequency of one of the compensator configurations, and where the reconfiguration logic causes the compensator transfer function to have a zero that minimizes the gap between the zero and the pole in the frequency space.

[0017] Additionally, in the following embodiments: When the reconfiguration logic causes the switched capacitor circuit to transition to a second configuration, the combination of the switched capacitor circuit in the second configuration and the switched inductor circuit has a transfer function: The transfer function has a pole that changes frequency, and where the reconfiguration logic causes the compensator transfer function to have a zero with the same frequency as the pole.

[0018] Some embodiments include a first die, where the compensator, the switched capacitor circuit, and the reconfiguration logic are located on the first die. In the following embodiments: The first die is configured to be connected to a second die that includes a feedback module, the feedback module being configured to cooperate with the compensator to provide feedback control of an uncontrolled power converter.

[0019] In the following embodiments: The uncontrolled power converter has a transfer function: The transfer function has a first Laplace transform that changes when the switched capacitor circuit is reconfigured, and the compensator has a transfer function: The transfer function has a second Laplace transform that changes when the compensator is reconfigured. In these embodiments, the reconfiguration logic attempts to keep the product of the first Laplace transform and the second Laplace transform constant.

[0020] In some embodiments, the switched capacitor circuit has a switched capacitor transfer function, and the compensator has a compensator transfer function. In these embodiments, a second switched capacitor configuration moves the double poles of the switched capacitor transfer function to a lower frequency, and in response, the reconfiguration logic reconfigures the compensator to lower the zero frequency of the compensator transfer function.

[0021] In some embodiments, a compensator and a feedback module that provides signals to the compensator cooperate to form an adaptive compensation circuit that responds dynamically to changes caused by reconfiguring a switched capacitor circuit.

[0022] Changes in the forward transfer function can result in changes in its gain, changes in the distribution of its poles and zeros, or both. Embodiments of the compensator include embodiments that compensate for changes in the distribution of poles and zeros in the complex frequency domain of the forward transfer function caused by the transition between the first switched capacitor configuration and the second switched capacitor configuration, or that compensate for changes in the gain of the forward transfer function caused by the transition between the first switched capacitor configuration and the second switched capacitor configuration, or that compensate for both the gain and changes in the distribution of poles and zeros in the complex frequency domain.

[0023] Additionally, in these embodiments: a regulator is implemented as a switched inductor circuit.

[0024] Additional embodiments include a comparator that receives a compensation circuit output from the compensation circuit and a reference signal and provides a differential signal to a modulator. The modulator then provides a duty cycle signal to the switched inductor circuit using the differential signal indicative of the difference between the reference signal and the compensation circuit output, where the duty cycle signal is based on the differential signal and the duty cycle signal causes a change in the duty cycle of switches in the switched inductor circuit. In these embodiments: reconfiguration logic provides a nominal duty cycle to the modulator and the modulator changes the nominal duty cycle in response to the differential signal, and in these embodiments: reconfiguration logic provides the reference signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] These and other features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings, in which:

[0026] Figure 1 A control system for controlling an additional uncontrolled boost power converter is shown;

[0027] Figures 2 to 5 A regulator for use with Figure 1 the power converter in

[0028] Figure 6 is shown; Figure 1 Details of a reconfigurable charge pump from the power converter shown in

[0029] Figure 7 are shown; Figure 1 Details of an exemplary external compensation circuit from the control system shown in

[0030] Figure 8 and Figure 9 shows the implementation of an internal compensation circuit from the Figure 1 control system shown;

[0031] Figure 10 shows a further control system for controlling Figure 1 a further uncontrolled boost power converter shown;

[0032] Figure 11 shows an internal compensation circuit from the Figure 10 control system shown; and

[0033] Figure 12 shows a diagram of a control system having a two - part internal compensation circuit. DETAILED DESCRIPTION

[0034] Figure 1 shows a voltage source 10 that provides an input voltage VIN to a controlled power converter 17. The controlled power converter 17 converts the input voltage VIN into an output voltage VOUT and makes the output voltage available to a load 14.

[0035] A feedback control system 16 controls the operation of an uncontrolled power converter 12 to produce the controlled power converter 17. The uncontrolled power converter 12 defines a forward transfer function, and the feedback control system 16 defines its feedback transfer function. The combination of the forward transfer function and the feedback transfer function defines the closed - loop transfer function of the controlled power converter 17.

[0036] The uncontrolled power converter 12 includes a regulator 20 and a switched - capacitor circuit 22. The regulator 20 and the switched - capacitor circuit 22 are in series with each other such that the regulator 20 receives the input voltage VIN and the switched - capacitor circuit 22 provides the output voltage VOUT. In this implementation, the regulator 20 is a boost converter. U.S. Patent No. 8,817,501 and U.S. Patent No. 9,203,299 describe suitable regulators and voltage multipliers in detail, the contents of which are incorporated herein by reference. As used herein, the term "charge pump" refers to a switched - capacitor circuit.

[0037] The switched - inductor circuit 20 receives the input voltage VIN. Then, it generates an intermediate voltage VX and provides the intermediate voltage VX to the switched - capacitor circuit 22. Then, the switched - capacitor circuit 22 converts the intermediate voltage VX into the output voltage VOUT.

[0038] Figure 1Power converters of the type shown are described in detail in the following patents: U.S. Patent No. 8,860,396, U.S. Patent No. 8,743,553, U.S. Patent No. 8,723,491, U.S. Patent No. 8,503,203, U.S. Patent No. 8,693,224, U.S. Patent No. 8,724,353, U.S. Patent No. 8,619,445, U.S. Patent No. 9,203,299, U.S. Patent No. 9,742,266, U.S. Patent No. 9,041,459, U.S. Publication No. 2017 / 0085172, U.S. Patent No. 9,887,622, U.S. Patent No. 9,882,471, PCT Publication No. WO2017161368, PCT Publication No. WO2017 / 091696, PCT Publication No. WO2017 / 143044, PCT Publication No. WO2017 / 160821, PCT Publication No. WO2017 / 156532, PCT Publication No. WO2017 / 196826, and U.S. Publication No. 2017 / 0244318, the contents of all of which are incorporated herein by reference.

[0039] Figure 2 Shown is a regulator 20 implemented as a switched inductor circuit that receives an input voltage across its first regulator terminal 41 and second regulator terminal 42. A switched inductor controller 40 attempts to regulate the input voltage to provide a stable output voltage across its third regulator terminal 43 and fourth regulator terminal 44. The switched inductor controller 40 attempts to maintain a stable output voltage by varying the duty cycle of regulator switch 46 and thus selectively disconnecting and connecting inductor 48.

[0040] Figure 2 The particular embodiment shown is a buck converter. The same components rearranged into a different topology result in Figure 3 a boost converter in Figure 4 and Figure 5 a buck - boost converter in Figure 5 In an alternative embodiment shown in Figures 2 to 5 a transformer provides electrical isolation between inductor 48 and the first regulator terminal 41, second regulator terminal 42, third regulator terminal 43, and fourth regulator terminal 44.

[0041] Figure 6 Shown is for Figure 1An example of the switched capacitor circuit 22 of the uncontrolled power converter 12 in

[0042] The switched capacitor circuit 22 is a single-phase boost symmetric cascade multiplier that has first, second, third, fourth, and fifth stacked switches S 1 , S 2 , S 3 , S 4 , S 5 , and first, second, third, and fourth phase switches S 6 , S 7 , S 8 , S 9 , and these switches cooperate to receive an input voltage across a first switched capacitor terminal 61 and a second switched capacitor terminal 62 and to generate an output voltage across a third switched capacitor terminal 63 and a fourth switched capacitor terminal 64.

[0043] There are four groups of switches: the first, third, and fifth stacked switches S 1 , S 3 , S 5 define a group of "odd stacked switches"; the second and fourth stacked switches S 2 , S 4 define a group of "even stacked switches"; the first and third phase switches S 6 , S 8 define a group of "even phase switches"; the second and fourth phase switches S 7 , S 9 define a group of "odd phase switches".

[0044] The switched capacitor circuit 22 also includes a first capacitor C 1 , a second capacitor C 2 , a third capacitor C 3 , and a fourth capacitor C 4 . These capacitors, together with the switches, define the "stages" within the switched capacitor circuit 22.

[0045] The illustrated switched capacitor circuit 22 has four stages. Each stage includes one of the capacitors C 1 , C 2 , C 3 , C 4 and one of four corresponding stacked switches S 1 , S 2 , S 3 , S 4 . The first stage includes the first stacked switch S1 and the first capacitor C 1 ; the second stage includes the second stacked switch S 2 and the second capacitor C 2 ; the third stage includes the third stacked switch S3 and a third capacitor C 3 ; The fourth stage includes a fourth stacked switch S 4 and a fourth capacitor C 4 . In Figure 3 the illustrated embodiment, since there are four stages, the maximum voltage transformation ratio is 5.

[0046] In response to receiving a control signal at the switched capacitor control terminal 65, the charge pump controller 66 places an operation control signal on the control signal path 60. These operation control signals cause the first, second, third, fourth, and fifth stacked switches S 1 , S 2 , S 3 , S 4 , S 5 and the first, second, third, and fourth phase switches S 6 , S 7 , S 8 , S 9 to change states according to a specific order. Thus, the switched capacitor circuit 22 repeatedly transitions between a first operating state and a second operating state at a specific frequency.

[0047] For example, during the first operating state, the charge pump controller 66 closes the odd-numbered stacked switches S 1 , S 3 , S 5 and the odd-numbered phase switches S 7 , S 9 , and opens the even-numbered stacked switches S 2 , S 4 and the even-numbered phase switches S 6 , S 8 . In contrast, during the second operating state, the charge pump controller 66 opens the odd-numbered stacked switches S 1 , S 3 , S 5 and the odd-numbered phase switches S 7 , S 9 , and closes the even-numbered stacked switches S 2 , S 4 and the even-numbered phase switches S 6 , S 8 .

[0048] In addition, the charge pump controller 66 transmits a reconfiguration control signal to the reconfiguration input terminal B1 of the reconfiguration block 68. In response, the reconfiguration block 68 provides reconfiguration signals at its reconfiguration output terminals A 1 to A 3 . These reconfiguration signals change the capacitors C 1 to C 4Connection therebetween.

[0049] The switched capacitor circuit 22 has switches that open and close during normal operation. The act of opening and closing these switches does not amount to changing the mode. The term "reconfiguring" expressly excludes the opening and closing of these switches during normal operation and is intended to produce a selected voltage transformation ratio.

[0050] The ability to reconfigure the capacitors C 1 to C 4 between their connections is particularly advantageous because it means that different voltage transformation ratios can be achieved using the same circuit. However, this ability comes at a cost. In particular, when the reconfiguration block 68 reconfigures the connections, it also changes the forward transfer function of the control system. Such a change can manifest as a change in the gain of the forward transfer function, a change in the distribution of its poles and zeros in the complex frequency domain, or both of the aforementioned changes.

[0051] Other examples of charge pumps include Ladder charge pumps, Dickson charge pumps, series-parallel charge pumps, Fibonacci charge pumps, and Doubler charge pumps, all of which can be adiabatically charged and configured as multi-phase or single-phase networks. A particularly useful charge pump is the adiabatically charged version of a full-wave cascade multiplier. However, non-adiabatically charged versions can also be used.

[0052] As used herein, "adiabatically" changing the charge on a capacitor means causing at least some of the charge stored in the capacitor to change via non-capacitive elements. A positive adiabatic change in the charge on a capacitor is considered adiabatic charging, while a negative adiabatic change in the charge on a capacitor is considered adiabatic discharging. Examples of non-capacitive elements include inductors, magnetic elements, resistors, and combinations thereof.

[0053] In some cases, a capacitor can be adiabatically charged for part of the time and non-adiabatically charged for the rest of the time. Such a capacitor is considered to be adiabatically charged. Similarly, in some cases, a capacitor can be adiabatically discharged for part of the time and non-adiabatically discharged for the rest of the time. Such a capacitor is considered to be adiabatically discharged.

[0054] Non-adiabatic charging includes all charging that is not adiabatic, and non-adiabatic discharging includes all discharging that is not adiabatic.

[0055] As used herein, an adiabatically charged switched capacitor circuit is a switched capacitor circuit having at least one capacitor that is both adiabatically charged and adiabatically discharged. A non-adiabatically charged switched capacitor circuit is a switched capacitor circuit that is not an adiabatically charged switched capacitor circuit.

[0056] Return to referenceFigure 1 The external compensation circuit 18 receives the output voltage VOUT as a feedback signal and transforms it into a first compensation voltage VCOMP. The internal compensation circuit 26 compares this first compensation voltage VCOMP with a reference voltage VREF.

[0057] The external compensation circuit 18 is typically provided by the end user based on the specific details of the application. However, Figure 1 As can be seen, the external compensation circuit 18 has no way of knowing whether a reconfiguration has occurred. Therefore, the external compensation circuit 18 will not be able to compensate for any changes in the system transfer function caused by such a reconfiguration.

[0058] On the other hand, the internal compensation circuit 26 is a main part of the uncontrolled power converter 12. The internal compensation circuit 26 is considered "internal" because it is typically located on the same semiconductor die as one or more other components of the uncontrolled power converter 12. In contrast, the external compensation circuit 18 will be connected to such a semiconductor die, but it is external to the semiconductor die.

[0059] Therefore, the external compensation circuit 18 receives a signal indicating a reconfiguration event and compensates for the resulting change in the system transfer function, whether the change manifests as a change in the gain of the transfer function or a change in the distribution of its poles and zeros. This frees the end user from having to know when the switched capacitor circuit 22 has been reconfigured.

[0060] Based on this comparison of the compensation voltage VCOMP with the reference voltage VREF, the internal compensation circuit 26 outputs a second compensation voltage VCOMP2.

[0061] Therefore, the external compensation circuit 18 and the internal compensation circuit 26 define a multi-stage compensation circuit that cooperates to stabilize the entire control system.

[0062] In the illustrated embodiment, the reconfiguration logic 24 provides the reference voltage VREF. However, the reference voltage VREF can also be provided from an external source.

[0063] Now referring to Figure 7 , the external compensation circuit 18 transforms the relatively high output voltage VOUT into a lower first compensation voltage VCOMP. Having a lower compensation voltage avoids having to provide the circuitry required to maintain a high voltage within the internal compensation circuit 26.

[0064] To achieve this, the external compensation circuit 18 is characterized by a voltage divider having a first resistor RD1 and a second resistor RD2, and these resistors define a node to which the internal compensation circuit 26 can be connected to receive the first compensation voltage VCOMP.

[0065] The external compensation circuit 18 is further characterized by a reactance path in parallel with the first resistor RD1. In the illustrated embodiment, the reactance path is characterized by a series reactance path resistor RPO and a reactance path capacitor CZO. By selecting the values of the resistance and capacitance of the reactance path, the system transfer function can be modified by introducing poles and zeros at specific locations in the complex plane.

[0066] Figure 8 and Figure 9 Two embodiments of the internal compensation circuit 26 are shown.

[0067] In Figure 8 the first embodiment shown, the operational amplifier 27 receives a first compensation voltage VCOMP and a reference voltage VREF at its inverting input and non-inverting input, respectively. This generates a second compensation voltage VCOMP2 at the output of the operational amplifier. The optional feedback path between the output of the operational amplifier and its inverting input includes a feedback resistor RZ2 and a feedback capacitor CP2. They introduce poles and zeros into the system transfer function. By selecting the resistance of the feedback resistor RZ2 and / or the feedback capacitor CP2, the positions of the poles and zeros in the complex frequency domain can be controlled.

[0068] In Figure 9 the second embodiment shown, the operational transimpedance amplifier 27 receives a first compensation voltage VCOMP and a reference voltage VREF at its inverting input and non-inverting input, respectively. This generates a second compensation voltage VCOMP2 at the output of the operational transimpedance amplifier. The optional shunt path between the output of the operational transimpedance amplifier and ground includes a shunt resistor RZ1 and a shunt capacitor CP1. They introduce poles and zeros into the system transfer function. By selecting the resistance of the shunt resistor RZ1 and / or the shunt capacitor CP1, the positions of the poles and zeros in the complex frequency domain can be controlled.

[0069] Returning to Figure 1 , the modulator 28 receives the second compensation voltage VCOMP2 and uses the second compensation voltage VCOMP2 to generate a duty cycle signal D, which is then transmitted to the switched inductor controller 40 through the control terminal 45 of the switched inductor circuit. The switched inductor controller 40 uses the duty cycle signal D as a basis for controlling the duty cycle of the regulating switch 46 in the switched inductor circuit 20.

[0070] In some embodiments, the reconfiguration logic 24 uses the input voltage VIN and the desired output voltage VREF to output a nominal duty cycle signal D0. In these embodiments, a second compensation voltage VCOMP2 causes the modulator 28 to modify the nominal duty cycle signal D0 to generate a duty cycle signal D. In these embodiments where the circuit that produces the forward transfer function is reconfigurable, the nominal duty cycle signal D0 depends on the configuration and can thus change when the circuit is reconfigured. For example, in these embodiments where the turns ratio of the switched capacitor circuit 22 can be changed, the nominal duty cycle signal D0 will change in a corresponding manner.

[0071] The duty cycle signal D affects the duty cycle and thus affects the current flowing out of the switched inductor circuit 20. Generally, this current increases with the duty cycle. However, the relationship between the duty cycle and the current depends on the details of the switched inductor circuit 20. The end result in either case is that the output voltage VOUT tracks the reference voltage VREF.

[0072] The feedback loop is designed to achieve certain desired operating characteristics of the controlled power converter 17. These characteristics can include: limiting the steady-state difference between the output voltage VOUT and the reference voltage VREF and the dynamic response of the output voltage VOUT to disturbances such as step changes or oscillations at different frequencies in the input current or output current. Of particular importance is configuring the feedback loop to ensure that the output voltage VOUT tracks the reference voltage VREF.

[0073] The external compensation circuit 18 is not necessarily required for the operation of the power converter. In some cases, there is a direct connection such that the output voltage VOUT equals the compensation voltage VCOMP. In such a scenario, resistors and reactive elements can be moved from the external compensation circuit 18 to the internal compensation circuit 26.

[0074] The following configuration is among those that use feedback: The external compensation circuit 18 implements a low-pass filter with a long time constant. This improves the stability of the overall feedback-controlled power converter 17.

[0075] Other configurations that use feedback have an external compensation circuit 18 that provides a desired response to disturbances such as rapid changes in the load current, which can cause corresponding rapid changes in the output voltage VOUT.

[0076] The compensation voltage depends on the feedback transfer function, which itself assumes a specific forward transfer function. If the forward transfer function changes, the compensation voltage will change.

[0077] Figure 10 is shown in connection with Figure 1A power converter similar to that shown, but with reconfiguration logic 24 that also has the ability to reconfigure the switched capacitor circuit 22 in response to the input voltage VIN and output voltage VOUT of the power converter. Such reconfiguration has the effect of changing the turns ratio and thus changing the forward path transfer function.

[0078] The change in the forward path transfer function changes the overall dynamics of the controlled power converter 17. These changes can affect the response of the output voltage VOUT to changes in the input voltage VIN or the output current IOUT. Thus, if the external compensation circuit 18 is designed for a first configuration of the switched capacitor circuit 22, it is likely to no longer work as expected when the switched capacitor circuit 22 adopts a second configuration.

[0079] To accommodate this difficulty, the controlled power converter 17 is also characterized by a reconfigurable internal compensation circuit 30 that receives a first compensation voltage VCOMP from the external compensation circuit 18 and converts it into a second compensation voltage VCOMP2 that depends on the configuration of the switched capacitor circuit 22. Thus, when Figure 6 the reconfiguration block 68 in reconfigures the switched capacitor circuit 22, the reconfiguration logic 24 also reconfigures the reconfigurable internal compensation circuit 30. The combination of the reconfigurable internal compensation circuit 30 and the external compensation circuit 18 (when present) can be regarded as an adaptive compensation circuit that responds dynamically to reconfiguration events within the circuit that generates the forward transfer function.

[0080] The reconfigurable internal compensation circuit 30 compensates for some or all of the changes in the forward transfer function. In particular, the reconfigurable internal compensation circuit 30 makes the overall forward transfer function appear to remain unchanged, even though the reconfiguration block 68 may have reconfigured the switched capacitor circuit 22. In the case where the feedback control is based on a linear transfer function that can be characterized by its Laplace transform, this can be achieved by ensuring that the product of the Laplace transform of the transfer function of the uncontrolled power converter, which is the combined transfer function of the switched inductor circuit 20 and the switched capacitor circuit 22, and the Laplace transform of the feedback control system 16 remains constant.

[0081] In some embodiments, this can be performed by moving the poles and / or zeros of the transfer function of the switched capacitor circuit and the corresponding poles and / or zeros of the transfer function of the reconfigurable compensator in the complex frequency domain. However, in cases where this is difficult to perform, heuristic rules for moving the poles and / or zeros of the transfer function of the reconfigurable compensator can be provided. For example, if the turns ratio of the switched capacitor circuit increases, then the output double poles typically move to lower frequencies. To compensate for this, the reconfiguration logic 24 will reconfigure the reconfigurable internal compensation circuit 30 so that its zeros are also at lower frequencies.

[0082] In this embodiment, the reconfiguration logic 24 changes the position of the zero of the reconfigurable internal compensation circuit 30 in steps. As an example, the reconfigurable internal compensation circuit 30 can be configured to move its zero in steps of 50 kHz. In this case, the uncontrolled power converter 12 may start operating with double poles at 100 kHz, in which case the reconfigurable internal compensation circuit 30 will be set to have a zero at 100 kHz. However, if the uncontrolled power converter 12 now has poles at 30 kHz after reconfiguration, then the reconfigurable internal compensation circuit 30 cannot place the corresponding zero at 30 kHz. In this case, the reconfigurable internal compensation circuit 30 will do the best by placing the zero at the closest allowed position in the frequency space, which is 50 kHz.

[0083] Referring to Figure 11 , the reconfigurable internal compensation circuit 30 includes an operational transimpedance amplifier ("OTA") 35 that receives a first compensation voltage VCOMP and a reference voltage VREF at its inverting input and non-inverting input, respectively. An optional shunt path between the output of the operational transimpedance amplifier and ground includes a shunt resistor RZ3 and a shunt capacitor CP3. They introduce poles and zeros in the system transfer function, where the positions of the poles and zeros depend on the choice of resistance and capacitance. To provide flexibility in moving the poles and zeros, one or both of the shunt resistor RZ3 and the shunt capacitor CP3 can exhibit variable electrical parameters. In the illustrated embodiment, the shunt resistor RZ3 has a variable resistance and the shunt capacitor CP3 has a variable capacitance. There are various ways to electronically control the resistance of the shunt resistor RZ3 and the capacitance of the shunt capacitor CP3.

[0084] The output of the operational transimpedance amplifier 35 is not used as the second compensation voltage VCOMP2 as is the case in Figure 9 . Instead, the output is passed to an optional reconfigurable virtual ground circuit 33.

[0085] The reconfigurable virtual ground circuit 33 is formed by switches S A 、SB , S C , S X , S Y , S Z interconnected resistive elements R X , R Y , R Z and reactive elements C A , C B , C C , C D of a network. By selectively opening and closing combinations of switches, the zero position can be shifted to compensate for the movement of poles and zeros when reconfiguring the switched capacitor circuit 22.

[0086] In some embodiments, the capacitors C A , C B , C C , C D have equal capacitance, and the resistors R X , R Y , R Z have equal resistance. However, this is by no means necessary. Additionally, there is no particular limitation on how many capacitors and resistors there are. The choice of values and quantities mainly depends on how many states the switched capacitor circuit 22 can be reconfigured into and the positions of the poles and zeros introduced by such reconfiguration in the complex plane.

[0087] The reconfiguration logic 24 further includes logic for selecting which of the switches S A , S B , S C , S X , S Y , S Z to open and close in response to the reconfiguration of the switched capacitor circuit to achieve the desired compensation. This selection causes the uncontrolled power converter 12 to exhibit a nominal forward transfer function. Compared to the case where there is no reconfigurable internal compensation circuit 30, this nominal forward transfer function is less dependent on the reconfiguration of the switched capacitor circuit.

[0088] Since the same nominal transfer function is always presented, there is no need to reconfigure the external compensation circuit 18 to accommodate the reconfiguration of the switched capacitor circuit 22. This means that the switched capacitor circuit 22 can change its voltage transformation ratio in a relatively seamless manner, at least as seen from the outside of the power converter 10. Thus, compared to the case where there is no reconfigurable internal compensation circuit 30, the reconfigurable internal compensation circuit 30 makes the overall transfer function less dependent on any reconfiguration of the switched capacitor circuit 22. More generally, compared to the case where there is no reconfigurable internal compensation circuit 30, the reconfigurable internal compensation circuit 30 makes the overall transfer function less dependent on any reconfiguration of any part of the circuit responsible for changing the forward transfer function.

[0089] In some embodiments, the reactive element is a capacitor. The resistive element and the reactive element can be small enough such that the reconfigurable internal compensation circuit 30, the switched capacitor circuit 22, and the reconfiguration logic 24 are located on the same semiconductor die. The external compensation circuit 18 can be located on a different die and / or created using external components such as multilayer ceramic capacitors (MLCCs) and chip resistors.

[0090] In Figure 12 , the modulator 28, the switched inductor circuit 20, and the switched capacitor circuit 22 are combined to form a switching regulator 34. As shown by the dashed arrows, the reconfiguration logic 24 reconfigures both the switching regulator 34 and the reconfigurable internal compensation circuit 30.

[0091] In the illustrated embodiment, the output of the switching regulator 34 is the output voltage VOUT. The inputs to the switching regulator 34 are the second compensation voltage VCOMP2, the input voltage VIN, and the output current IOUT. The second compensation voltage VCOMP2 is a function of the first compensation voltage VCOMP, the input reference voltage VREF, and / or other values.

[0092] For a particular configuration of the reconfigurable internal compensation circuit 30, the design of the external compensation circuit 18 depends on the loop transfer function of the loop starting from the switching regulator 34 and proceeding through the additional internal compensation circuit 38.

[0093] The additional internal compensation circuit 38 generally includes circuitry for introducing poles and zeros into the transfer function. In some embodiments, the poles and zeros are fixed. In other embodiments, the poles and zeros are reconfigurable. In either case, the external compensation circuit 18 receives the output of the additional internal compensation circuit 38.

[0094] In some embodiments, the external compensation circuit 18 includes a voltage divider as Figure 7 shown. However, in other embodiments, alternatively, the additional internal compensator circuit 38 includes such a voltage divider.

[0095] The reconfigurable internal compensation circuit 30 receives the reduced voltage VCOMP and continues to proceed to dynamically introduce additional poles and zeros as discussed in connection with Figure 9 or Figure 11 as discussed.

[0096] The design of the external compensation circuit 18 depends on the gain margin and phase margin of the loop transfer function. The gain and phase of the loop transfer function are typically functions of frequency. Typically, there is a frequency at which the phase is equal to 180 degrees relative to a reference. At this frequency, there is also a corresponding gain. The extent to which this corresponding gain, measured in dB, is less than one is referred to as the "gain margin".

[0097] Conversely, since both the gain and phase depend on frequency, there is a frequency at which the gain is one. The corresponding phase at this frequency determines the phase margin. In particular, the phase margin is the extent to which the corresponding phase is less than 180 degrees.

[0098] In some examples, the gain response and phase response of the feedback control system 16 are modeled as small signals susceptible to linearized analysis about the operating point of the switching regulator 34.

[0099] In certain cases, the task of compensating for the linear and non-linear characteristics of the feedback control system 16 is divided between the reconfigurable internal compensation circuit 30 and the external compensation circuit 18. In some embodiments, the reconfigurable internal compensation circuit 30 compensates for the linear component of the overall transfer function, while the external compensation circuit 18 compensates for the non-linear component, and vice versa.

[0100] Generally speaking, a computer-accessible storage medium may include any non-transitory storage medium that is accessible to a computer during use for providing instructions and / or data to the computer. For example, a computer-accessible storage medium may include storage media such as magnetic disks or optical disks and semiconductor memories.

[0101] Generally, a non-abstract database representing a system can be a database or other data structure that can be read by a program and used, directly or indirectly, to fabricate hardware including the system. For example, the database can be a behavioral-level description or a register-transfer level (RTL) description of the hardware functionality in a high-level design language (HDL) such as Verilog or VHDL. This description can be read by a synthesis tool that can synthesize the description to produce a netlist including a list of gates from a synthesis library. The netlist includes a set of gates that also represent the functionality of the hardware including the system. The netlist can then be placed and routed to produce a data set describing the geometry to be applied to a mask. The mask can then be used in various semiconductor manufacturing steps to produce one or more semiconductor circuits corresponding to the system. In other examples, alternatively, the database itself can be a netlist (with or without a synthesis library) or a data set.

[0102] The invention and its preferred embodiments have been described, and what is claimed is defined by the appended claims.

Claims

1. An apparatus for compensating for changes in the gain of a power converter, comprising: a controller for generating one or more control signals; and a compensator for compensating for changes in the gain of the power converter at least partially based on the one or more control signals, the gain being at least partially based on a transition between a first power converter configuration and a second power converter configuration corresponding to a first turns ratio and a second turns ratio, wherein the change in the gain includes a change in at least one transfer function of the power converter, and wherein the compensator compensates for the change in the at least one transfer function that occurs at least partially based on the transition between the first power converter configuration and the second power converter configuration, wherein the at least one transfer function includes a compensator transfer function, and zeros of the compensator transfer function move in frequency steps at least partially based on the transition between the first power converter configuration and the second power converter configuration.

2. The apparatus according to claim 1, wherein the power converter includes at least a charge pump and a regulator coupled to the charge pump.

3. The apparatus according to claim 2, wherein the first power converter configuration and the second power converter configuration include configurations regarding the charge pump and / or the regulator.

4. The apparatus according to claim 1, wherein the at least one transfer function includes at least one forward transfer function.

5. The apparatus according to claim 1, wherein the first turns ratio and the second turns ratio are different from each other.

6. The apparatus according to claim 1, wherein the power converter includes a buck-boost power converter.

7. The apparatus according to claim 1, wherein the compensator compensates for one or more linear characteristics of the change in the at least one transfer function.

8. The apparatus according to claim 7, wherein the compensator includes a first compensation circuit that compensates for one or more linear characteristics of the change in the at least one transfer function, and the first compensation circuit receives a voltage from a second compensation circuit that compensates for one or more non-linear characteristics of the change.

9. The apparatus according to claim 1, wherein the second power converter configuration includes a transfer function having a pole with a changing frequency, and wherein the compensator transfer function includes zeros that chase the pole in an associated frequency space.

10. The apparatus according to claim 1, wherein the second power converter configuration includes a transfer function having a pole including a pole frequency, and wherein the second power converter configuration includes a compensator configuration that defines a gap between a zero frequency corresponding to a zero associated with the compensator configuration and the pole frequency.

11. The apparatus according to claim 10, wherein The compensator configuration also defines a set of gaps, where a particular gap in the set of gaps corresponds to the difference between the pole frequency and the zero frequency of at least one of the compensator configurations, and wherein the compensator transfer function has a zero to minimize the gap between the zero and the pole in the associated frequency space.

12. The apparatus according to claim 1, wherein, the second power converter configuration includes a transfer function having a pole with a varying frequency, and wherein the compensator transfer function includes a zero having the same frequency as the pole.

13. The apparatus according to claim 1, wherein, the at least one transfer function includes at least a charge pump transfer function and a compensator transfer function, and wherein, when the power converter is in the second power converter configuration, the double poles of the charge pump transfer function shift to a lower frequency.

14. The apparatus according to claim 13, wherein, the compensator reduces the zero frequency of the compensator transfer function at least partially based on the shift of the double poles of the charge pump to a lower frequency.

15. The apparatus according to claim 1, wherein, the compensator compensating for the change in gain includes: compensating for a change in the distribution of poles and zeros of the at least one transfer function in the frequency domain, the change in distribution occurring at least partially based on the transition between the first power converter configuration and the second power converter configuration.

16. The apparatus according to claim 1, wherein, the compensator includes an internal compensation circuit and an external compensation circuit coupled to the internal compensation circuit, the internal compensation circuit receiving a voltage from the external compensation circuit, and wherein the compensation for the change in gain is distributed between the internal compensation circuit and the external compensation circuit, the internal compensation circuit compensating for one or more linear characteristics of the at least one transfer function, and the external compensation circuit compensating for one or more non - linear characteristics of the at least one transfer function.

17. A method for compensating for a change in gain of a power converter, the method comprises: detecting a transition between a first power converter configuration and a second power converter configuration corresponding to a first turns ratio and a second turns ratio of the power converter; determining at least partially based on the detected transition a change in at least one transfer function of the power converter; generating one or more control signals at least partially based on the determined change; and compensating at least partially based on the one or more control signals for the change in the at least one transfer function caused by the transition between the first power converter configuration and the second power converter configuration, wherein the at least one transfer function includes a compensator transfer function, and the zero of the compensator transfer function moves in a frequency step at least partially based on the transition between the first power converter configuration and the second power converter configuration.

18. The method according to claim 17, wherein, Compensating for the change in the at least one transfer function between the first power converter configuration and the second power converter configuration includes compensating for the configuration of a charge pump and / or a regulator with respect to the power converter.

19. The method according to claim 17, wherein, the power converter includes a buck-boost power converter, wherein the at least one transfer function includes at least one forward transfer function, and wherein the first turns ratio and the second turns ratio are different from each other.

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