Driving circuit and method of controlling switching element

Abstract

A driving circuit for controlling a switching element is provided. The driving circuit (200) comprises a plurality of bootstrap capacitors (210) and a switch unit (211). Furthermore, the driver circuit (200) comprises a control unit (102) configured to control the switching unit (211) according to a control signal (ActHS) to provide a parallel arrangement of the plurality of bootstrap capacitors (210) between the charging voltage (VDD) and a reference voltage during said charging phase to charge the plurality of bootstrap capacitors (210); and providing a series arrangement of a plurality of bootstrap capacitors (210) between the charging voltage (VDD) and the control port of the switching element (MHS) during the control phase to control the switching element (MHS).

Description

Technical Field

[0001] The present application relates to a driver circuit and a corresponding method for controlling a switching element. Background Art

[0002] Controlling and driving ungrounded switching elements, especially transistors, presents several challenges. Power conversion topologies, such as buck converter and / or half-bridge converter topologies, include one or more ungrounded high-side switching elements. A bootstrap drive circuit may be used to generate a voltage sufficient to drive the high-side switching element, wherein the bootstrap drive circuit typically includes a bootstrap capacitor for generating a voltage to control the high-side switching element.

[0003] The bootstrap capacitor of the bootstrap drive circuit may need to have a relatively high capacitance value to provide a sufficiently high voltage to drive the high-side switching element. This may result in relatively high cost and chip area.

[0004] The present application solves the technical problem of reducing the capacitance value of a bootstrap capacitor in a drive circuit for driving a switching element. The technical problem is solved by the independent claims. Preferred examples are set out in the dependent claims. Summary of the invention

[0005] According to a first aspect, the present application describes a drive circuit for controlling a switching element. The drive circuit comprises a plurality of bootstrap capacitors and a switching unit. In addition, the drive circuit comprises a control unit configured to control the switching unit according to a control signal, wherein the switching unit is controlled to provide a parallel arrangement of a plurality of bootstrap capacitors between a charging voltage and a reference voltage during a charging phase to charge the plurality of bootstrap capacitors; and to provide a series arrangement of a plurality of bootstrap capacitors between a charging voltage and a control port of the switching element during a control phase to control the switching element.

[0006] According to a second aspect, the present application describes a method for controlling a switching element using a plurality of bootstrap capacitors. The method comprises providing a parallel arrangement of a plurality of bootstrap capacitors between a charging voltage and a reference voltage during a charging phase to charge the plurality of bootstrap capacitors; and providing a series arrangement of a plurality of bootstrap capacitors between the charging voltage and a control port of the switching element during a control phase to control the switching element.

[0007] It should be noted that the methods and systems outlined in this application and their preferred embodiments can be used alone or in combination with other methods and systems disclosed in this application. In addition, features outlined in the context of the system also apply to the corresponding method. In addition, all aspects of the methods and systems outlined in this application can be combined in any way. In particular, the features of the claims can be combined in any way with each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention is explained in an exemplary manner by reference to the accompanying drawings, in which:

[0009] Figure 1a An example power converter is shown;

[0010] Figure 1b Shown is an example relationship between a target voltage for driving a switching element and a required capacitance value for a bootstrap capacitor;

[0011] Figure 2a An example power converter including a drive circuit of a cascaded bootstrap capacitor is shown;

[0012] Figure 2b An example of a cascaded bootstrap capacitor is shown;

[0013] Figure 2c An example relationship between the target voltage for driving the switching element and the required capacitance value of the bootstrap capacitor is shown;

[0014] Figure 3 A flow chart illustrating an example method of controlling a switching element using multiple bootstrap capacitors is presented. DETAILED DESCRIPTION

[0015] As mentioned above, the present application aims to provide a particularly compact and efficient driver circuit for driving an ungrounded switching element. In this context, Figure 1a An example DC / DC power converter 100 is shown. According to the converter topology, the terminal node V X 、V Y and V Z The following voltage values ​​may be obtained:

[0016] Buck Configuration: V X =V IN , V Y =V OUT , V Z =GND;

[0017] Boost Configuration: V X =V OUT , V Y =V IN , V Z = GND; and / or

[0018] Inverting Buck-Boost Configuration: V X =V IN , V Y =GND, V Z =V OUT .

[0019] V IN、V OUT and GND represent the input voltage, output voltage, and ground potential, respectively. The output voltage regulation of the converter can be achieved by duty cycle operation of the power stage, which involves controlling the low-side power switch element M LS and high-side power switch element M HS The switching elements may be field effect transistors (FETs). The switching elements are controlled by respective gate drivers 101, 102. The digital control signal Act LS and Act HS The conversion to the power domain of the respective gate drivers 101 , 102 may be performed using a level shifter 'LVL'.

[0020] The power stage, i.e. the switching element M LS and M HS , which can be implemented using NMOS transistors. The high-side switching element can use an n-type transistor because it has a smaller area (due to increased charge mobility) and lower gate capacitance than a p-type transistor. Using an NMOS transistor as a high-side switching element usually requires the use of a bootstrap capacitor C B 110 guides the gate driver 102 to cope with the change of the voltage level (ie, the reference voltage) of the switch node SW.

[0021] Usually the bootstrap capacitor C B 110 is charged to a higher voltage to ensure that the high-side switching element M HS Depending on the converter topology and the technical environment in which the switching elements operate, different voltage sources may be used to supply the bootstrap capacitor C B 110 is charged. For example, in the case of a buck converter, the input voltage of the buck converter can be the bootstrap capacitor C B 110 Power supply and / or charging. The input voltage may be provided by a lithium-ion battery of the portable device.

[0022] High-side switching element M HS The mathematical expression of the gate-source voltage 111 (i.e., the control voltage) is the capacitance C of the bootstrap capacitor 110. B and the gate capacitance C of the high-side switching element gg The result of charge redistribution between the two can be expressed as follows (ignoring the diode D 1 Pressure drop):

[0023]

[0024] Among them, Q B represents the charge on the bootstrap capacitor 110, C total represents the total capacitance after charge redistribution, including the gate capacitance C of the high-side switching elementgg and the capacitance C of the bootstrap capacitor 110 B . V DD represents the voltage to which the bootstrap capacitor 110 is charged before charge redistribution begins. Charge redistribution from the bootstrap capacitor 110 to the gate capacitance results in a gate-source voltage V gs 111.

[0025] In one example, the switching cycle of operating the power converter 100 may be performed with the low-side switching element M LS The activation starts, for example, using a gate-source voltage V GS,LS ≈4V. When the low-side switching element M LS When the switch node SW is pulled to ground, the bootstrap capacitor 110 uses the charging voltage V DD Charging, for example, charging to V CB ≈4.8V. The low-side switching element M LS After turning off, the high-side switching element M HS turns on, bringing the switch node SW to a high state (e.g., the terminal node V X The gate-source voltage 111 of the high-side switching element is the result of charge redistribution between the bootstrap capacitor 110 and the gate capacitance of the high-side switching element. Therefore, when the high-side switching element is turned on, the voltage of the bootstrap capacitor 110 increases from its initial value (e.g., V CB ≈4.8V) to a lower value, such as V CB =V GS,HS ≈4V.

[0026] Figure 1b The size, in particular the capacitance value, of the bootstrap capacitor 110 required to provide a certain target gate-source voltage for controlling the high-side switching element is shown. It can be seen that the capacitance value 120 of the bootstrap capacitor 110 increases significantly with an increase in the target value 121 of the target gate-source voltage 111 (according to the relation 122). The capacitance 120 required for the bootstrap capacitor 110 is generally dependent on the gate capacitance C of the high-side switching element. gg and / or the charging voltage of the bootstrap capacitor V DD .

[0027] This document describes a bootstrap high-side driver circuit configured to generate a relatively high gate-source voltage 111 for controlling a high-side switching element in an area efficient manner.

[0028] Figure 2aAn example power converter 100 with a bootstrap high-side driver circuit 200 is shown for driving a high-side switching element. The driver circuit 200 is configured to use a relatively small bootstrap capacitor 110 to provide a relatively large gate-source voltage 111 for controlling the high-side switching element. To this end, the driver circuit 200 includes a plurality of bootstrap capacitors 110, 210, 210, in particular a basic bootstrap capacitor 110 and two or more (additional) bootstrap capacitors C B11 , C B2 210. The basic bootstrap capacitor 110 is not used to drive the gate of the high-side switching element, thereby greatly reducing the size of the basic bootstrap capacitor 110. Two or more (additional) bootstrap capacitors C B1 , C B2 210 is used to drive the gate of the high-side switching element.

[0029] All bootstrap capacitors 110, 210 are recharged by coupling the bottom plate of each bootstrap capacitor 110, 210 to the switch node SW and charging the top plate of each bootstrap capacitor 110, 210 to the charging voltage V DD In the start-up phase of the high-side switch element, the drive circuit 200 uses the switch unit 211 to connect the bootstrap capacitor C B1 , C B2 The capacitors 210 are stacked in series (as opposed to a parallel arrangement for charging). This results in a voltage pile-up effect, providing a higher gate-source voltage 111 at the high-side switching element.

[0030] Figure 2a An example power converter 100 is shown in a boost converter topology. A switching cycle may begin with activation of the low-side switching element (e.g., using V GS,LS ≈4V). When the low-side switch element pulls the switch node SW to ground, all bootstrap capacitors C B , C B1 , C B2 110 and 210 are arranged in parallel, and each capacitor can be charged to a given voltage, such as V CB ≈4.8V. After the low-side switch element is turned off, the high-side switch element can be turned on, thereby bringing the switch node SW to a high state. The gate-source voltage 111 of the high-side switch element is determined by the bootstrap capacitor stack (consisting of an additional bootstrap capacitor C B1 , C B2 210) and the gate capacitance C of the high-side switching element gg Therefore, during the high-side turn-on period, the voltage of each additional bootstrap capacitor 210 decreases from its initial value (e.g., V CB≈4.8V) to its new value, which may be half of the gate-source voltage 111 of the high-side switching element, such as V CB1 =V CB2 =0.5×V GS,HS ≈2V, while the gate-source voltage 111 itself is the sum of the voltages of each additional bootstrap capacitor 210, e.g. V GGS,HS =V CB1 +V CB2 ≈4V. Basic bootstrap capacitor C B 110 does not participate in driving the high-side switching element, but can be used to control the driving circuit 102. The voltage of the basic bootstrap capacitor 110 may remain relatively constant during the low-side (ie, charging) and high-side (ie, control) phases.

[0031] The gate-source voltage of the high-side switching element V gs 111, the result is a bootstrap capacitor stack 240 (consisting of an additional bootstrap capacitor C B1 , C B2 210) to the gate capacitance C of the high-side switching element gg The result of charge redistribution can be expressed as follows (ignoring the diode D 1 , D 2 Pressure drop):

[0032]

[0033] Among them, C B,1 / 2 is the total bootstrap capacitor for the gate driver, consisting of two (usually K) separate (additional) bootstrap capacitors C B1 , C B2 210 components.

[0034] Figure 2c The total bootstrap capacitor size 120 required to achieve a certain target gate-source voltage 121 of the high-side switch element 111 is shown. It can be seen that when using the stacked capacitor implementation (relation 222), the total bootstrap capacitor size 120 can be significantly reduced, especially for higher values ​​of the target gate-source voltage 121 of the high-side switch element 111. In particular, the relationship between the bootstrap capacitor value 120 and the target value 121 of the high-side switch element gate-source voltage 111 in relation 222 has a more gradual curvature than relation 122. When the target value 121 of the high-side switch element gate-source voltage 111 is close to the nominal value of the charging voltage VDD of the bootstrap capacitor 210, the bootstrap capacitor size required using the stacked bootstrap capacitor 210 is significantly reduced.

[0035] from Figure 2cIt can be seen that when the target gate-source voltage 111 of the high-side switch element is small, it may be more advantageous to use a single bootstrap capacitor 110. However, when the target gate-source voltage exceeds a certain threshold, such as about 3.5V, the total bootstrap capacitor size of the stacked capacitor implementation is smaller. For example:

[0036] -In V GS,HS =3.6V, the stacked capacitor implementation can be reduced by 15%;

[0037] -In V GS,HS =4V, the stacked capacitor implementation can be reduced by 50%.

[0038] The charging voltage of the bootstrap capacitor V DD There may be a minimum boundary and a maximum boundary within a certain range. The maximum boundary may be determined by the oxide thickness of the bootstrap capacitor 110, 210. An increase in oxide thickness generally results in an increase in the maximum boundary. The minimum boundary may be determined by the generated charging voltage V DD The source of the charge voltage V DD is generated by a lithium-ion battery, the minimum boundary may be 2 to 3V). The stacked capacitor implementation described herein can be used to charge the bootstrap capacitors 110, 210 at a voltage V DD The gate-source voltage 111 of the target voltage level 121 is generated above the bootstrap capacitor 110, 210. DD This can be beneficial when relatively close to its minimum boundary.

[0039] Figure 2b An example capacitor circuit 240 is shown, which includes a plurality of bootstrap capacitors C B1 , C B1 ,…,C Bn 210 and a switch unit 211, the switch unit is configured as:

[0040] - During the charging phase, multiple bootstrap capacitors C B1 , C B1 ,…,C Bn 210 are arranged in parallel at a charging voltage V DD and a reference voltage (corresponding to the voltage of the switch node SW) in order to provide a voltage for each bootstrap capacitor C B1 , C B1 ,…,C Bn 210 is charged to a capacitor voltage (usually substantially equal to the charging voltage V DD );as well as

[0041] - During the control phase, multiple bootstrap capacitors C B1 , C B1,…,C Bn 210 are arranged in series at a charging voltage V DD and a control port, in particular a gate of the switching element, to generate a control voltage 111 for controlling the switching element, in particular a gate-source voltage.

[0042] Through Figure 2a Inverter shown and / or Figure 2b The switch shown is used to realize the bootstrap capacitor C B1 , C B1 ,…,C Bn 210 Control of the bottom plate and / or top plate.

[0043] Figure 3 A method (possibly implemented by a computer) for controlling a switching element M not connected to ground GND using a plurality of bootstrap capacitors 210 is shown. HS The method 300 comprises providing 301 a plurality of bootstrap capacitors 210 arranged in parallel at a charging voltage V during the charging phase. DD and a reference voltage to charge the plurality of bootstrap capacitors 210. Specifically, the parallel arrangement of the plurality of bootstrap capacitors 210 may be arranged at a charging voltage V DD and includes a switching element M HS Therefore, among the plurality of bootstrap capacitors 210, the voltage across each bootstrap capacitor 210 may be equal and may substantially correspond to the charging voltage V DD (Because during the charging phase the reference voltage may correspond to ground GND).

[0044] The method 300 further includes providing 302 a plurality of charging voltages V during the control phase. DD and switching element M HS A bootstrap capacitor 210 is connected in series between the control port (particularly the gate) of the switch element M in order to control the switch element M during the control phase. HS Therefore, a relatively high control voltage 111 can be efficiently provided, in particular for controlling the switching element M HS of the bootstrap capacitors 210 (by using a relatively small total capacitance of the plurality of bootstrap capacitors 210).

[0045] Thus, a method for controlling the switching element M is described. HS (not grounded) driving circuit 200. Switching element M HS It can be a high-side switching element of the power converter 100. Alternatively, the switching element M HS It may be an n-type metal oxide semiconductor (MOS) field effect transistor (FET).

[0046] The driving circuit 200 includes a plurality of bootstrap capacitors 210 and a switch unit 211. The plurality of bootstrap capacitors 210 may include two or more, in particular three or more bootstrap capacitors 210. The capacitance values ​​of the individual capacitors 210 of the plurality of bootstrap capacitors 210 may be substantially equal. The switch unit 211 may include one or more inverters and / or one or more switches. In particular, the switch unit 211 may be configured to provide different arrangements of the plurality of bootstrap capacitors 210, such as a parallel arrangement and a series arrangement.

[0047] The driving circuit 200 comprises a control unit 102, which is configured to control a switch unit 211 according to a (possibly digital) control signal ActHS. In particular, the switch unit 211 can be controlled to provide a plurality of bootstrap capacitors 210 with a charging voltage V during the charging phase. DD In the plurality of bootstrap capacitors 210, K bootstrap capacitors 210 (K ≥ 2 or K ≥ 3) may be arranged in parallel with each other so that each of the K bootstrap capacitors 210 is arranged at a charging voltage V DD By doing so, each of the K bootstrap capacitors can be charged to a capacitor voltage level (which may substantially correspond to the charging voltage V DD ).

[0048] In addition, the switch unit 211 can be controlled to DD and switching element M HS A plurality of bootstrap capacitors 210 are arranged in series between the control ports (particularly the gates) of the switching element M in order to control the switching element M during the control phase. HS By doing so, the control voltage 111 (particularly the gate-source voltage) can be applied to the switching element M HS The series arrangement of the plurality of bootstrap capacitors 210 results in a voltage across the plurality of bootstrap capacitors 210 corresponding to K times the capacitance voltage (before charge redistribution). This increased voltage across the plurality of bootstrap capacitors 210 can be used to generate a relatively high control voltage 111 in an efficient manner, particularly using a relatively low total capacitance of the plurality of bootstrap capacitors 210.

[0049] During the charging phase, the reference voltage may be different when the plurality of bootstrap capacitors 210 are arranged in parallel, and in particular, lower than the reference voltage when the plurality of bootstrap capacitors 210 are arranged in series during the control phase. In particular, the reference voltage may correspond to the first terminal node V X The first potential (during the control phase) and the second terminal node V Z a second potential, in particular ground potential (during the charging phase).

[0050] The control unit 102 may be configured to control the switch unit 211 to provide a parallel arrangement of the plurality of bootstrap capacitors 210. HS Indicating switch element M HS In addition, the control unit 102 can be configured to control the switch unit 211 to provide a series arrangement of multiple bootstrap capacitors 210, if the control signal Act HS Indicating switch element M HS Therefore, the switching element M HS It may be turned on during the charging phase and turned off during the control phase.

[0051] The control unit 102 may be configured to control the switch unit 211 to operate a sequence of switching cycles of the plurality of bootstrap capacitors 210. In particular, each switching cycle may include a charging phase and a subsequent control phase, in particular exactly one charging phase and a subsequent control phase. By doing so, efficient continuous operation of the drive circuit 200 may be provided.

[0052] The driving circuit 200 may be configured such that, during the charging phase of the parallel arrangement of the plurality of bootstrap capacitors 210, each of the plurality of bootstrap capacitors 210 is charged to a capacitor voltage level. The capacitor voltage level is typically less than the charging voltage V DD Furthermore, the drive circuit 200 may be configured such that the control voltage 111 is provided during the control phase via a series arrangement of a plurality of bootstrap capacitors 210 for controlling the switching element M. HS The control voltage 111 is higher than the charging voltage V DD By doing so, a particularly reliable switching element M can be provided. HS control.

[0053] The driving circuit 200 may further include a basic bootstrap capacitor 110, which is arranged at a charging voltage V during the charging phase and between the control phases. DD and a reference voltage, in particular permanently arranged at a charging voltage V DD and a reference voltage. The basic bootstrap capacitor 110 may be configured to provide power to the control unit 102 for operation of the control unit 102. By providing the basic bootstrap capacitor 110, the reliability of the driving circuit 200 may be improved.

[0054] Furthermore, a power converter 100 is described, which comprises a switching element M HS and for controlling the switching element M HS The driving circuit 200 can be configured as described in this application.

[0055] Switching element M HS can be arranged at the first terminal node V of the power converter 100 X and the switch node SW. The reference voltage of the switch node SW may be the first terminal node V X The first potential and the second terminal node V Z The voltage at which a resistor varies between a second potential (usually ground).

[0056] The driving circuit 200 can be configured to control the switch unit 211 so that during the charging phase, the plurality of bootstrap capacitors 210 are arranged in parallel at the charging voltage V DD and the switch node SW, thereby providing reliable charging of the K bootstrap capacitors 210.

[0057] The driving circuit 200 described in the present application includes a bootstrap capacitor C for providing the gate-source voltage 111 of the high-side switch through charge redistribution. B1 , C B2 The switch unit 211 may include a CMOS inverter unit 1 1 , used to connect the bootstrap capacitor C B2 The bottom plate is connected to the bootstrap capacitor C B1 The switch unit 211 may include a CMOS inverter unit 1. 2 , used to set the gate V of the high-side switch G,HS Connected to the bootstrap capacitor C B2 of the top plate (for the control phase) or the switch node SW (for the charging phase).

[0058] In addition, multiple diodes D can be used 1 , D 2 Provide a charging voltage V for the corresponding plurality of bootstrap capacitors 210 DD The charging path to recharge the bootstrap capacitor C B1 , C B2 .

[0059] Figure 2b A more general core circuit structure 240 of a cascaded switched capacitor boosting stage is shown.

[0060] The sequential method of operation might be as follows:

[0061] 1. During the low-side turn-on period, the switch node SW may be pulled to ground;

[0062] 2. Switching unit 211, especially inverter I 1 , it is possible to place the bootstrap capacitor CB2 The bottom plate is connected to the switch node SW, the switch unit 211, in particular the inverter I 2 , possibly connecting the gate terminal of the high-side switch to the switching node SW, thereby keeping the high-side switch turned off;

[0063] 3. All bootstrap capacitors C B , C B1 , C B2 210 may pass through respective diodes D 0 , D 1 , D 2 From the charging voltage V DD Charge;

[0064] 4. In the subsequent control phase, the low-side switch may be turned off;

[0065] 5. Switching unit 211, especially inverter I 1 , it is possible to place the bootstrap capacitor C B1 The top plate is connected to the bootstrap capacitor C B2 The bottom plate, the switch unit 211, in particular the inverter I 2 , possibly connecting the gate terminal of the high-side switch to the bootstrap capacitor C B2 's top plate, thereby turning on the high-side switch;

[0066] 6. The high-side switch turns on, causing the switch node SW to rise.

[0067] The proposed stacked bootstrap capacitor scheme is particularly suitable when the target gate-source voltage of the high-side switch is relatively close to the charging voltage V of the bootstrap capacitor. DD In addition, when the target gate-source voltage of the high-side switch is higher than the charging voltage V DD This approach is also beneficial when

[0068] The structure of the proposed stacked bootstrap capacitor scheme is modular and can be expanded to multiple capacitor stages according to the technical environment and application requirements. These different capacitor boost stages can be switched by inverters and / or switches. The drive circuit 200 can be connected to the switch node SW and / or referenced to different potentials to support various DC / DC converters and output stage topologies. The scheme can achieve efficient power stage operation at a relatively low charging voltage, thereby effectively expanding the supported duty cycle range of the DC / DC converter 100.

[0069] It should be noted that the description and illustrations only illustrate the basic principles of the proposed method and system. A skilled person will be able to implement various arrangements that, although not explicitly described or illustrated herein, are consistent with the principles of the invention and are included in its spirit and scope. In addition, all examples and implementations herein are primarily for illustrative purposes to help readers understand the principles of the proposed method and system. In addition, all principles, aspects, implementations and specific examples thereof provided herein are intended to cover their equivalents.

Claims

1. A driving circuit for controlling a switching element, the driving circuit comprising: Multiple bootstrap capacitors; Switching unit; A control unit, the control unit being configured to control the switch unit according to a control signal to: providing a parallel arrangement of the plurality of bootstrap capacitors between a charging voltage and a reference voltage during a charging phase to charge the plurality of bootstrap capacitors; During a control phase, a series arrangement of the plurality of bootstrap capacitors is provided between the charging voltage and a control port of the switching element to control the switching element.

2. The driving circuit according to claim 1, wherein: The control unit is configured to control the switch unit to: providing said parallel arrangement of said plurality of bootstrap capacitors if said control signal indicates that said switching element should be opened; The series arrangement of the plurality of bootstrap capacitors is provided if the control signal indicates that the switching element should be closed.

3. The driving circuit according to claim 1, wherein: The driver circuit further comprises a basic bootstrap capacitor, which is arranged, in particular permanently arranged, between the charging voltage and the reference voltage during the charging phase and during the control phase; The basic bootstrap capacitor is configured to provide electrical energy to the control unit to facilitate operation of the control unit.

4. The driving circuit according to claim 1, wherein: The drive circuit is configured such that: charging each of the plurality of bootstrap capacitors to a capacitance voltage level through the parallel arrangement of the plurality of bootstrap capacitors during the charging phase, wherein the capacitance voltage level is less than the charging voltage; A control voltage for controlling the switching element is provided by the series arrangement of the plurality of bootstrap capacitors during the control phase, the control voltage being higher than the charging voltage.

5. The driving circuit according to claim 1, wherein: the drive circuit being configured to provide a control voltage to the control port of the switching element using the series arrangement of the plurality of bootstrap capacitors during the control phase; The control port is the gate of the switch element; The control voltage is a gate-source voltage.

6. The driving circuit according to claim 1, wherein: The plurality of bootstrap capacitors comprises two or more, in particular three or more bootstrap capacitors.

7. The driving circuit according to claim 1, wherein: The reference voltage when the parallel arrangement of the multiple bootstrap capacitors is used during the charging phase is different from that when the series arrangement of the multiple bootstrap capacitors is used during the control phase, and in particular is lower when the parallel arrangement of the multiple bootstrap capacitors is used during the charging phase than when the series arrangement of the multiple bootstrap capacitors is used during the control phase.

8. The driving circuit according to claim 1, wherein: The switch unit comprises: one or more inverters; and / or One or more switches.

9. The driving circuit according to claim 1, wherein: The capacitance of each of the plurality of bootstrap capacitors is substantially equal.

10. The driving circuit according to claim 1, wherein: The control unit is configured to control the switching unit to operate the plurality of bootstrap capacitors in a series of switching cycles; One, in particular each switching cycle comprises a charging phase and a subsequent control phase, in particular exactly one charging phase and exactly one subsequent control phase.

11. A power converter, comprising: Switching elements; and The driving circuit according to claim 1, is used to control the switching element.

12. The power converter of claim 11, wherein: The switch element is arranged between the first terminal node and the switch node of the power converter; the switch node exhibits a reference voltage that varies between a first potential of the first terminal node and a second potential of a second terminal node of the power converter; and The driving circuit is configured to control the switching unit to arrange the parallel arrangement of the plurality of bootstrap capacitors between the charging voltage and the switching node during the charging phase.

13. The power converter of claim 11, wherein: The switching element is a high-side switching element of the power converter; and / or The switching element is an n-type metal oxide semiconductor field effect transistor.

14. A method for controlling a switching element using a plurality of bootstrap capacitors, the method comprising: providing a parallel arrangement of the plurality of bootstrap capacitors between a charging voltage and a reference voltage during a charging phase to charge the plurality of bootstrap capacitors; and During a control phase, a series arrangement of the plurality of bootstrap capacitors is provided between the charging voltage and a control port of the switching element to control the switching element.

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