Apparatus and method for controlling a charge pump

Abstract

The present invention provides an apparatus and method for controlling a charge pump. The apparatus for controlling a charge pump includes a charge pump circuit connected to an input circuit, a first capacitor coupled to the charge pump circuit and provided as an element of a resonance circuit, a first switching element connected to the first capacitor, and a controller configured to read an input current and / or an input voltage from the input circuit, generate a pulse width modulation signal according to the input current and / or the input voltage, and output the pulse width modulation signal to control the first switching element. Accordingly, THD and harmonics can be improved while reducing the cost of the circuit.

Description

Technical Field

[0001] The embodiments disclosed herein relate generally to the field of power control circuits, and more specifically to devices and methods for controlling charge pumps. Background Technology

[0002] Resonant circuits are increasingly used in power control circuits; for example, single-stage LLC circuits are commonly used for low output ripple current and low-cost products. Meanwhile, charge pump circuits are frequently applied in power control circuits. For instance, in some solutions, a series charge pump capacitor is added to improve THD (Total Harmonic Distortion) and / or harmonics.

[0003] Reference document 1: WO2013 / 113836A1.

[0004] Reference document 2: US2009 / 0128057A1.

[0005] Reference document 3: US6366027B1.

[0006] This section provides information to aid in a better understanding of aspects of this disclosure. Therefore, the statements in this section should be read in this light and should not be construed as an admission of anything that is in the prior art or not in the prior art. Summary of the Invention

[0007] The inventors discovered that a series charge pump capacitor is needed to improve THD and harmonics in products used for widened voltage applications, such as light-emitting diodes (LEDs). In this solution, the charge pump capacitor is constant for each load, making it a costly solution.

[0008] In some solutions, a first-order power factor correction (PFC) function can be added for different loads; however, PFC functions are also costly. Furthermore, these solutions are time-consuming to develop, and poor harmonic performance will limit the operating range.

[0009] To address at least some of the aforementioned problems, methods, apparatus, and devices are provided in this disclosure. The features and advantages of embodiments of this disclosure will also be understood from the following description of specific embodiments, which, by way of example, illustrate the principles of embodiments of this disclosure, when viewed in conjunction with the accompanying drawings.

[0010] Typically, embodiments of this disclosure provide an apparatus and method for controlling a charge pump. It is desirable to reduce the number of components and cost, while improving THD and / or harmonics with a simple structure.

[0011] In a first aspect, an apparatus for controlling a charge pump is provided. The apparatus for controlling the charge pump includes: a charge pump circuit connected to an input circuit and an output circuit; a first capacitor coupled to the charge pump circuit and provided as a component of a resonant circuit; a first switching element connected to the first capacitor; wherein the capacitance value of the first capacitor is changed by switching operation of the first switching element; and a controller configured to read input current and / or input voltage from the input circuit, generate a pulse width modulation signal based on the input current and / or input voltage, and output the pulse width modulation signal to control the first switching element.

[0012] In some implementations, the controller is configured to adjust the pulse width modulation signal to improve the power factor or total harmonic distortion or harmonics of the resonant circuit.

[0013] In some implementations, the controller is configured to modify the charge pump capacitor value of the charge pump circuit during the power frequency cycle.

[0014] In some implementations, the charge pump capacitor value of the charge pump circuit is modified along with the changed capacitance value of a first capacitor, which is controlled by a pulse width modulation signal.

[0015] In some implementations, the controller is configured to locate the charge pump capacitance value of the charge pump circuit under one of a plurality of different loads.

[0016] In some implementations, the controller is configured to change the duty cycle of the pulse width modulation signal to modify the charge pump capacitance in a load, determine whether the input power, input voltage, or input frequency has changed, and maintain the pulse width modulation signal when the input power, input voltage, or input frequency has not changed.

[0017] In some embodiments, the device further includes a second capacitor coupled to the charge pump circuit and provided as an element of the resonant circuit; wherein the second capacitor is connected in parallel with the first capacitor.

[0018] In some embodiments, the device further includes a second switching element disposed between the first switching element and the controller; wherein a pulse width modulation signal from the controller is used to control the second switching element, and the second switching element is configured to generate a signal to control the first switching element.

[0019] In a second aspect, a method for controlling a charge pump is provided, wherein a charge pump circuit is connected to an input circuit and an output circuit; a first capacitor is coupled to the charge pump circuit and provided as a component of a resonant circuit; and a first switching element is connected to the first capacitor.

[0020] The method includes: reading input current and / or input voltage from an input circuit; generating a pulse width modulation signal based on the input current and / or input voltage; and outputting the pulse width modulation signal to control a first switching element; wherein the capacitance value of the first capacitor is changed by the switching operation of the first switching element.

[0021] In some implementations, the method further includes: adjusting the pulse width modulation signal to improve the power factor or total harmonic distortion or harmonics of the resonant circuit.

[0022] In some implementations, the method further includes modifying the charge pump capacitor value of the charge pump circuit during the power frequency cycle.

[0023] In some implementations, the charge pump capacitor value of the charge pump circuit is modified along with the changed capacitance value of a first capacitor, which is controlled by a pulse width modulation signal.

[0024] In some implementations, the method further includes finding the charge pump capacitance value of the charge pump circuit under one of a plurality of different loads.

[0025] In some implementations, the method further includes: changing the duty cycle of the pulse width modulation signal to modify the charge pump capacitance in a load; determining whether the input power, input voltage, or input frequency has changed; and maintaining the pulse width modulation signal when the input power, input voltage, or input frequency has not changed.

[0026] In a third aspect, a power driver is provided. The power driver includes: a charge pump circuit connected to an input circuit and an output circuit; a resonant circuit coupled to the charge pump circuit; a switching element connected to a capacitor of the resonant circuit; wherein the capacitance value of the capacitor is changed by switching operation of the switching element; and a controller configured to read input current and / or input voltage from the input circuit, generate a pulse width modulation signal based on the input current and / or input voltage, and output the pulse width modulation signal to control the switching element.

[0027] According to various embodiments of this disclosure, a first switching element and a controller are provided, and the capacitance value of the first capacitor is changed by switching operation of the first switching element. Therefore, THD and harmonics can be improved while reducing circuit cost. Attached Figure Description

[0028] The above and other aspects, features, and benefits of various embodiments of the present disclosure will become more apparent by way of example and through the following detailed description with reference to the accompanying drawings, wherein similar reference numerals or letters are used to denote similar or equivalent elements. The drawings are shown for the purpose of better understanding embodiments of the present disclosure and are not necessarily drawn to scale, wherein:

[0029] Figure 1 This is a diagram illustrating an apparatus for controlling a charge pump according to an embodiment of this disclosure;

[0030] Figure 2 This is a diagram illustrating an example of a waveform without capacitor control according to an embodiment of this disclosure;

[0031] Figure 3 This is a diagram illustrating an example of a waveform with capacitor control according to an embodiment of the present disclosure.

[0032] Figure 4 This is a diagram illustrating a method for controlling a charge pump according to an embodiment of this disclosure;

[0033] Figure 5 This is another illustration of a method for controlling a charge pump according to an embodiment of the present disclosure;

[0034] Figure 6 This is an illustration of a power driver according to an embodiment of the present disclosure. Detailed Implementation

[0035] This disclosure will now be described with reference to several exemplary embodiments. It should be understood that the purpose of discussing these embodiments is solely to enable those skilled in the art to better understand and implement this disclosure, and not to impose any limitation on the scope of this disclosure.

[0036] It should be understood that when an element is referred to as "connected," "coupled," or "in contact" with another element, it can be directly connected, coupled, or in contact with the other element, or there may be intermediate elements. Conversely, when an element is referred to as "directly connected," "directly coupled," or "directly in contact" with another element, there are no intermediate elements. Other terms used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.).

[0037] As used herein, the terms “first” and “second” refer to distinct elements. Unless the context clearly indicates otherwise, the singular forms “an” and “a” are intended to include the plural forms as well. As used herein, the terms “comprising,” “including,” “having,” and / or “containing” specify the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0038] The term “based on” should be understood as “at least partially based on”. The term “covering” should be understood as “at least partially covering”. The terms “one implementation” and “implementation” should be understood as “at least one implementation”. The term “another implementation” should be understood as “at least one other implementation”. Other explicit and implicit definitions may be included below.

[0039] In this disclosure, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which the exemplary embodiments pertain. It should be further understood that terms defined, for example, in commonly used dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of the relevant field, and will not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0040] This disclosure provides a digital control method for performing stable control with a simple structure. For example, the controller in this disclosure is a microcontroller unit (MCU), but is not limited thereto.

[0041] The first aspect of the implementation plan

[0042] In one implementation, a device for controlling a charge pump is provided.

[0043] Figure 1 This is a diagram illustrating an apparatus for controlling a charge pump according to an embodiment of this disclosure.

[0044] like Figure 1 As shown, the device 100 for controlling the charge pump includes: a charge pump circuit 101 connected to an input circuit 1011; a first capacitor 102 (C4) coupled to the charge pump circuit 101 and provided as a component of a resonant circuit (such as an LLC circuit); and a first switching element 103 (Q1) connected to the first capacitor 102.

[0045] In this disclosure, the capacitance value of the first capacitor 102 is changed by the switching operation (on / off) of the first switching element 103. For example, when the first switching element 103 is on, the capacitance value C of the first capacitor 102 is... on The capacitance C of the first capacitor 102 when the first switching element 103 is turned off off different.

[0046] like Figure 1As shown, the device 100 for controlling the charge pump also includes a controller 104 configured to read input current and / or input voltage (Vin) from input circuit 1011, generate pulse width modulation (PWM) signals based on the input current and / or input voltage, and output PWM signals to control the first switching element 103.

[0047] It should be understood that some parts or components are only used as... Figure 1 Examples are shown in the figure. However, it is not limited to this; for example, the connection or position of parts or components can be adjusted, and / or some parts or components can be omitted.

[0048] In addition, you can add Figure 1 Some parts or components not shown in the diagram, at the same time Figure 1 Components or elements shown but not explained, such as C1-C5, D1-D5, R1-R5 and Vcc, may be referred to in the relevant field.

[0049] In some implementations, controller 104 is configured to adjust the pulse width modulation signal to improve the power factor (PF) or total harmonic distortion (THD) or harmonics of the resonant circuit.

[0050] For example, controller 104 is configured to operate in an open-loop manner. Controller 104 reads the input current and input voltage, and calculates the input power based on the input current and input voltage. Then, controller 104 compares the calculated input power with a predefined power, and changes the PWM signal when the calculated input power does not match the predefined power.

[0051] In another example, controller 104 is configured to operate in a closed-loop manner. Controller 104 reads the input current and input voltage, and calculates the input power based on the input current and input voltage. Controller 104 then modifies the PWM signal, and correspondingly, the input current and / or input voltage change along with the modified PWM signal. Then, when the input power stabilizes, controller 104 determines the PWM signal.

[0052] Therefore, it can improve the power factor (PF) or the total harmonic distortion (THD) or harmonics of a resonant circuit.

[0053] In some implementations, controller 104 is configured to modify the charge pump capacitor value of the charge pump circuit during the power frequency cycle.

[0054] For example, the charge pump capacitance value of charge pump circuit 101 is modified along with the changed capacitance value of first capacitor 102, which is controlled by a pulse width modulation signal.

[0055] Therefore, voltage-widened products such as light-emitting diodes (LEDs) do not require series charge pump capacitors. This can improve THD and harmonics while reducing circuit costs.

[0056] In some implementations, controller 104 is configured to locate the charge pump capacitance value of the charge pump circuit at one of a plurality of different loads. For example, controller 104 may analyze which values ​​for PF, THD, and / or harmonics are optimal at a given load and maintain the charge pump capacitance value and PWM signal at that load.

[0057] In some implementations, controller 104 is configured to change the duty cycle of the pulse width modulation signal to modify the charge pump capacitance in a load, determine whether the input power, input voltage, or input frequency has changed, and maintain the pulse width modulation signal when the input power, input voltage, or input frequency has not changed.

[0058] Therefore, the charge pump capacitor value can be modified under different loads, which can improve the circuit performance without increasing the circuit cost.

[0059] like Figure 1 As shown, the device 100 for controlling the charge pump also includes: a second capacitor 105 (C3) coupled to the charge pump circuit 101 and provided as a component of the resonant circuit; the second capacitor 105 is connected in parallel with the first capacitor 102.

[0060] like Figure 1 As shown, the device 100 for controlling the charge pump further includes: a second switching element 106 (Q2) disposed between the first switching element 103 and the controller 104; a pulse width modulation signal from the controller 104 is used to control the second switching element 106, and the second switching element 106 is configured to generate a signal to control the first switching element 103.

[0061] Therefore, stable control with a simple structure is implemented.

[0062] Figure 2 This is an illustration of an example waveform without capacitor control according to an embodiment of this disclosure. For example, without capacitor control. Figure 1 C4, Q1, and controller 104 in this context. In this case, as... Figure 2 As shown, the waveform at the zero crossing point needs to be improved (shown as 201).

[0063] Figure 3 This is an illustration showing an example waveform with capacitor control according to an embodiment of this disclosure. For example, using... Figure 1 C4, Q1, and controller 104 in this context. In this case, as... Figure 3As shown, the waveform at the zero-crossing point is improved (shown as 301). Therefore, THD and harmonics can be improved while reducing circuit cost.

[0064] In some implementations, resonant circuits (such as LLC circuits) are used to drive light-emitting diodes (LEDs) as output loads. However, they are not limited to this; resonant circuits (such as LLC circuits) can also be used to drive other output loads.

[0065] It should be understood that the examples or embodiments discussed above are for illustrative purposes and not for limitation. Those skilled in the art will understand that many other embodiments or examples may exist within the scope of this disclosure.

[0066] As can be seen from the above implementation scheme, a first switching element and a controller are provided, and the capacitance value of the first capacitor is changed by the switching operation of the first switching element. Therefore, THD and harmonics can be improved, while reducing the cost of the circuit.

[0067] The second aspect of the implementation plan

[0068] In one embodiment, a method for controlling a charge pump is provided. A corresponding device 100 is shown in the first aspect of the embodiment, and those identical to those in the first aspect of the embodiment are omitted.

[0069] Figure 4 This is an illustration of a method for controlling a charge pump according to an embodiment of this disclosure. For example, the method is executed by a controller 104. Figure 4 As shown, method 400 includes:

[0070] 401, Read the input current and / or input voltage from the input circuit;

[0071] 402, generates a pulse width modulation signal based on the input current and / or input voltage, and

[0072] 403, outputs a pulse width modulation signal to control the first switching element; wherein the capacitance value of the first capacitor is changed by the switching operation of the first switching element.

[0073] It should be understood that Figure 4 This is merely an example of what is disclosed, but is not limited to it. For example, the order of operations at boxes or steps can be adjusted, and / or some boxes or steps can be omitted. Furthermore, additional steps can be added. Figure 4 Some boxes or steps are not shown in the diagram.

[0074] In some implementations, the method further includes: adjusting the pulse width modulation signal to improve the power factor or total harmonic distortion or harmonics of the resonant circuit.

[0075] In some implementations, the method further includes modifying the charge pump capacitance value of the charge pump circuit during the power frequency cycle. For example, the charge pump capacitance value of the charge pump circuit is modified along with the changed capacitance value of a first capacitor, which is controlled by a pulse width modulation signal.

[0076] Figure 5 This is another illustration of a method for controlling a charge pump according to an embodiment of the present disclosure. For example, the method is executed by a controller 104. Figure 5 As shown, method 500 includes:

[0077] 501, reads the input current and / or input voltage from the input circuit;

[0078] 502, generates a pulse width modulation signal based on the input current and / or input voltage;

[0079] 503, find the charge pump capacitor value of a charge pump circuit under one of several different loads;

[0080] 504, Change the duty cycle of the pulse width modulation signal to modify the charge pump capacitor in a given load;

[0081] 505, determine whether the input power, input voltage, or input frequency has changed, and

[0082] 506, maintains the pulse width modulation signal when the input power, input voltage, or input frequency remains unchanged. In this case, it can be considered to be in a steady state, and the PWM signal and charge pump capacitor value can be considered as available configurations.

[0083] like Figure 5 As shown, 501 continues to execute when the input power, input voltage, or input frequency changes. In this case, it can be considered to be in an unstable state, and the PWM signal and charge pump capacitor value need to be updated.

[0084] like Figure 5 As shown, method 500 includes:

[0085] 507, outputs a pulse width modulation signal to control a first switching element; wherein the capacitance value of the first capacitor is changed by the switching operation of the first switching element.

[0086] It should be understood that Figure 5 This is merely an example of what is disclosed, but is not limited to it. For example, the order of operations at boxes or steps can be adjusted, and / or some boxes or steps can be omitted. Furthermore, additional steps can be added. Figure 5 Some boxes or steps are not shown in the diagram.

[0087] As can be seen from the above implementation scheme, a first switching element and a controller are provided, and the capacitance value of the first capacitor is changed by the switching operation of the first switching element. Therefore, THD and harmonics can be improved, while reducing the cost of the circuit.

[0088] The third aspect of the implementation plan

[0089] In one embodiment, a power driver is provided. Corresponding devices 100 and methods 500 are shown in the first and second aspects of the embodiments, and identical content to that in the first and second aspects of the embodiments is omitted.

[0090] Figure 6 This is an illustration of a power driver according to an embodiment of the present disclosure.

[0091] like Figure 6 As shown, the power driver 600 includes: a charge pump circuit 601 connected to an input circuit 6011 and an output circuit 6012; a resonant circuit 602 coupled to the charge pump circuit 601; and a switching element 603 connected to a capacitor C4 in the resonant circuit 602; wherein the capacitance value of the capacitor C4 is changed by switching operation of the switching element 603.

[0092] like Figure 6 As shown, the power driver 600 also includes a controller 604 configured to read input current and / or input voltage from input circuit 6011, generate a pulse width modulation signal based on the input current and / or input voltage, and output the pulse width modulation signal to control the switching element 603.

[0093] It should be understood that some parts or components are only used as... Figure 6 Examples are shown in the figure. However, it is not limited to this; for example, the connection or position of parts or components can be adjusted, and / or some parts or components can be omitted.

[0094] In addition, you can add Figure 6 Some parts or components not shown in the diagram, at the same time Figure 6 Components or elements shown but not explained, such as C1-C5, D1-D5, R1-R6, L1, P1, S1, S2, D6-D7, C6, and Vcc, may be referred to in the relevant field.

[0095] In some embodiments, the power driver 600 may be used to drive a light-emitting diode (LED). In other embodiments, the power driver 600 is included in a light-emitting diode (LED) driver; for example, the power driver 600 is part of an LED driver.

[0096] It should be understood that the examples or embodiments discussed above are for illustrative purposes and not for limitation. Those skilled in the art will understand that many other embodiments or examples may exist within the scope of this disclosure.

[0097] As can be seen from the above implementation scheme, a first switching element and a controller are provided, and the capacitance value of the first capacitor is changed by the switching operation of the first switching element. Therefore, THD and harmonics can be improved, while reducing the cost of the circuit.

[0098] Furthermore, although there may be significant effort and many design options, driven by available time, current technology and economic considerations, for example, when guided by the concepts and principles disclosed herein, it is expected that those skilled in the art will readily generate such software instructions and programs and integrated circuits (ICs) with minimal experimentation.

[0099] Generally, the various embodiments of this disclosure can be implemented in hardware or special-purpose circuitry, software, logic components, or any combination thereof. Some aspects can be implemented in hardware, while others can be implemented in firmware or software executable by a controller, microprocessor, or other computing device.

[0100] Although various aspects of the embodiments of this disclosure are illustrated and described by way of block diagrams, flowcharts or other drawings, it should be understood that the blocks, apparatuses, systems, techniques or methods described herein (as non-limiting examples) may be implemented in hardware, software, firmware, special-purpose circuitry or logic components, general-purpose hardware or controllers or other computing devices or some combination thereof.

[0101] Furthermore, although the operations are shown in a specific order, this should not be interpreted as requiring them to be performed in the shown order or in a sequential order, or that all shown operations need to be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous.

[0102] Similarly, while certain specific implementation details are included in the foregoing discussion, these details should not be construed as limiting the scope of this disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features described in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of individual embodiments may also be implemented individually or in any suitable sub-combination in multiple embodiments.

[0103] Although this disclosure has been described in language specific to structural features and / or methodological actions, it should be understood that this disclosure, as defined by the appended claims, is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are disclosed as exemplary forms for implementing the claims.

Claims

1. A device for controlling a charge pump, comprising: A charge pump circuit, wherein the charge pump circuit is connected to the input circuit; A first capacitor is coupled to the charge pump circuit and is provided as a component of the resonant circuit. A first switching element is connected to the first capacitor; The capacitance value of the first capacitor is changed by the switching operation of the first switching element; and A controller configured to read input current and / or input voltage from the input circuit, generate a pulse width modulation signal based on the input current and / or the input voltage, and output the pulse width modulation signal to control the first switching element. The controller is configured to modify the charge pump capacitor value of the charge pump circuit during the power frequency cycle. The charge pump capacitor value of the charge pump circuit is modified along with the changed capacitance value of the first capacitor, which is controlled by the pulse width modulation signal.

2. The device of claim 1, wherein the controller is configured to adjust the pulse width modulation signal to improve the power factor or the total harmonic distortion or harmonics of the resonant circuit.

3. The device according to claim 1 or 2, wherein the controller is configured to locate the charge pump capacitance value of the charge pump circuit under one of a plurality of different loads.

4. The device of claim 3, wherein the controller is configured to change the duty cycle of the pulse width modulation signal to modify the charge pump capacitor in a load, determine whether the input power or the input voltage or the input frequency has changed, and maintain the pulse width modulation signal when the input power or the input voltage or the input frequency has not changed.

5. The device according to claim 1 or 2, wherein the device further comprises: A second capacitor is coupled to the charge pump circuit and is provided as an element of the resonant circuit; The second capacitor is connected in parallel with the first capacitor.

6. The device according to claim 1 or 2, wherein the device further comprises: A second switching element is configured between the first switching element and the controller; The pulse width modulation signal from the controller is used to control the second switching element, and the second switching element is configured to generate a signal to control the first switching element.

7. The device according to claim 1 or 2, wherein the resonant circuit is used to drive a light-emitting diode (LED) as an output load.

8. A method for controlling a charge pump, wherein the charge pump circuit is connected to an input circuit; The first capacitor is coupled to the charge pump circuit and is provided as a component of the resonant circuit; The first switching element is connected to the first capacitor; The method includes: Read the input current and / or input voltage from the input circuit; Generate a pulse width modulation signal based on the input current and / or the input voltage, and The pulse width modulation signal is output to control the first switching element; wherein the capacitance value of the first capacitor is changed by the switching operation of the first switching element. The method further includes: The charge pump capacitor value of the charge pump circuit is modified during the power frequency cycle, wherein the charge pump capacitor value of the charge pump circuit is modified together with the changed capacitance value of the first capacitor, which is controlled by the pulse width modulation signal.

9. The method of claim 8, wherein the method further comprises: Adjusting the pulse width modulation signal to improve the power factor or the total harmonic distortion or harmonics of the resonant circuit.

10. The method according to claim 8 or 9, wherein the method further comprises: Find the charge pump capacitance value of the charge pump circuit under one of several different loads.

11. The method of claim 10, wherein the method further comprises: The duty cycle of the pulse width modulation signal is changed to modify the charge pump capacitor in a certain load; Determine whether the input power, input voltage, or input frequency has changed, and The pulse width modulation signal is maintained when the input power, input voltage, or input frequency remains unchanged.

12. A power driver, comprising: A charge pump circuit, wherein the charge pump circuit is connected to the input circuit; A resonant circuit, which is coupled to the charge pump circuit; A switching element, the switching element being connected to a capacitor in the resonant circuit; The capacitance value of the capacitor is changed by the switching operation of the switching element. and A controller configured to read input current and / or input voltage from the input circuit, generate a pulse width modulation signal based on the input current and / or the input voltage, and output the pulse width modulation signal to control the switching element. The controller is configured to modify the charge pump capacitor value of the charge pump circuit during the power frequency cycle. The charge pump capacitor value of the charge pump circuit is modified along with the changed capacitance value of the capacitor, which is controlled by the pulse width modulation signal.

13. The power driver of claim 12, wherein the power driver is used to drive a light-emitting diode (LED); or the power driver is included in a light-emitting diode (LED) driver.

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